Volume 2013, Issue 1 - University of Michigan

Transcription

Abstract Booklet
8th Annual Engineering Graduate
Symposium
Friday, November 15, 2013
College of Engineering, University of Michigan, Ann Arbor
2
Table of Contents
Message from the Chairs
Committee and Volunteers
Sponsors
Abstracts
Aerospace Engineering: Flight Dynamics and Controls
Aerospace Engineering: Fluid Dynamics, Thermal Sciences and Combustion
Atmospheric, Oceanic, and Space Sciences: Atmospheric and Climate Sciences
Atmospheric, Oceanic, and Space Sciences: Space and Planetary Sciences
Biomedical Engineering
Chemical Engineering: Sustainable Energy
Chemical Engineering: Nanotechnology and Microfabricated Systems
Civil and Environmental Engineering: Infrastructure Error! Bookmark not defined.
Civil and Environmental Engineering: Environment and Water Resources
Computer Science and Software Design
Electrical Engineering: Applied Electromagnetics and Plasma Science
Electrical Engineering: Integrated Circuits, VLSI, MEMS, and Microsystems
Electrical Engineering: Optics, Photonics, and Solid State Devices
Electrical Engineering Systems: Systems Engineering and Communication
Electrical Engineering Systems: Control Systems, Power and Energy
Electrical Engineering Systems: Signal and Image Processing, Computer Vision
Industrial and Operations Engineering: Operations Research
Industrial and Operations Engineering: Ergonomics
Mechanical Engineering: Design and Manufacturing
Mechanical Engineering: Automotive Engineering and Transportation
Mechanical Engineering: Mechanics of Materials and Structures
Material Science and Engineering: Materials for Energy Conversion and Storage
Material Science and Engineering: Synthesis and Application of Organic and Bio Materials
Nuclear Engineering and Radiological Sciences: Fission Systems and Radiation
Measurements/Imaging
Richard and Eleanor Towner Award
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From the Chairs
th
We, on the behalf of the planning committee, would like to welcome you to the 8 edition of the annual
Engineering Graduate Symposium (EGS ’13), which is a premier event for graduate students in the College
of Engineering (CoE). This event is aimed at establishing collaboration and communication from different
disciplines, as well as facilitating interactions between current graduate students, prospective students,
faculty members and corporate sponsors.
This year’s symposium is focused on fostering enterprenurial thinking among the graduate students and a
lecture titled “Arbor Networks Ph.D Research Impact Lecture” will be the keynote. This lecture is based on
an award given to an alum that has made significant discovery or innovation translating into an industry or
company, based on their dissertation. The research poster presentation by the current graduate students
is the central theme of the event.
EGS ‘13 has received about 300 submissions this year, which is a new record for this event. The planning
committee comprises of sub-committees and representatives from all departments / tracks in the CoE,
who review the submissions in their respective areas of expertise. This enables graduate students to share
their research and accomplishments as well as review the research currently being conducted by their
peers. In addition to the technical program, the symposium hosts special sessions and tours for
prospective graduate students invited from top schools nationwide, introducing them to the broad
research portfolio of the College of Engineering.
We look forward to meeting you and welcoming you on November 15, 2013.
Best regards,
4
Riddhiman Bhattacharya & Deepak Singh
Symposium Co-Chairs
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Committee and Volunteers
Mike Nazareth
Director for Graduate Recruitment
Tiffany Porties
Assistant Director for Graduate Education
Programs
Andria Rose
Coordinator for Graduate Education Programs
Shira Washington
Coordinator for Graduate Education Programs
EGS Planning Committee
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Riddhiman Bhattacharya
MS&E
EGS Planning Committee Co-Chair
Deepak Singh
AOSS
EGS Planning Committee Co-Chair
Brandan Walters
BME
Editorial Chair
Kendra Keady
NERS
Logistics Chair
Abhinav Dasari
Aero
Publicity Chair
Alex Emly
MS&E
Sponsor Recruiter
Jacob Davidson
Aero
Website, Aero Track Chair
Aravind Venkitasubramony
AOSS
AOSS Track Chair
Barry Belmont
BME
BME Track Chair
Ran Gao
CEE
CEE Track Chair
Anh Ta
ChE
ChE Track Chair
Cheng Zhang
EE
EE Track Chair
Parinaz Naghizadeh Ardabili
EE:Sys
EE:Systems Track Chair
Greggory Schell
IOE
IOE Track Chair
Nakul Shah
IS+D
IS+D Track Chair
Joshua Padeti
ME
ME Track Chair
Sung Joo Kim
MS&E
MS&E Track Chair
Bruce Pierson
NERS
NERS Track Chair
Austin Allen
Aero
Editorial Committee
Janakiraman Balachandran
ME
Sponsorship Committee
Huai-Ning Chang
BME
Logistics Committee
Adam Mendrela
EE
EE Committee
Samanthule Nola
Macro
Logistics Committee
Rahul Singh
BME
Logistics Team
Eric Yu
EE
EE Committee
Prospective Committee
Aramis Alvarez
EE
Sarah Paleg
ChE
David Burdette
Aero
Minnae Chabwera
Aero
Liz Cloos
EE
Michelle Gonzalez
Melendez
ChE
Juan Lopez
MS&E
Elizabeth Mamantov
CSE
Jose Mesa
NAME
Irving Olmedo
CSE
Christina Reynolds
CEE
Megan Szakasits
ChE
Andre Thompson
MS&E
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Sponsors
We would also like to thank:
Are You a Human
In2being
ProSource International, LCC
SRS Technologies, LLC
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Benzinga
Logic Solutions
Quantum Signal
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Abstracts
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17
Aerospace Engineering:
Flight Dynamics, Controls &
Optimization
Session Chair: Jacob Davidson
18
Nonlinear optimal control of a rotary inverted pendulum
Ambarish Desai1, Dr. Noboru Sakamoto2
1
2
Department of Aerospace Engineering, University of Michigan, Ann Arbor, USA
Department of Aerospace Engineering, Nagoya University, Nagoya, Japan
In this work, we have addressed the problem of swing up and stabilization of a rotary
inverted pendulum. The motivation was to derive a single feedback control law for both
the swing up and stabilization unlike most of past work which use different feedback
control laws for these two operations. The problem is formulated as an optimal control
problem and solved using stable manifold approach which has been proposed to solve
the Hamilton-Jacobi equation. The problem is solved by extending the domain of
solutions to include the pending position. After a finite number of iterations, an optimal
feedback control law for a reduced system is obtained. The closed loop system dynamics
with this controller is then verified using simulations. We acknowledge the contribution of
Kazuo Ishikawa and Kyosuke Yamaguchi and the staff of the JUACEP at Nagoya
University in completion of this work. This work was done as a part of the graduate
research exchange program at Nagoya University under the ambit of JUACEP in
collaboration with IPE at University of Michigan, Ann Arbor, supported and funded by
Nagoya University, Japan.
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Large-Scale Multidisciplinary Optimization of a Small Satellite's Design and
Operation
John T. Hwang1, Dae Young Lee1, James W. Cutler1, Joaquim R. R. A. Martins1
1
Department of Aerospace Engineering, University of Michigan
Gradient-based multidisciplinary optimization is applied to a small satellite. This problem
involves large numbers of design variables, state variables, and disciplines, necessitating
the use of a gradient-based optimizer, adjoint-based coupled derivative computation, a
new multidisciplinary optimization framework, and the multidisciplinary feasible
architecture. The modeled disciplines are orbit dynamics, attitude dynamics, cell
illumination, temperature, solar power, energy storage, and communication. Many of
these contain discontinuities and non-smooth regions that are addressed to enable
numerically exact derivative computation for all modeled variables. The design problem’s
wide-ranging time scales, spanning 30 seconds to 1 year, are captured through a
combination of multi-point optimization and the use of a small time step in the analyses.
Optimizations involving over 25,000 design variables and 2.2 million unknowns require
100 hours to converge nearly 5 and 3 orders of magnitude in feasibility and optimality,
respectively. Results show that geometric design variables yield a 40% improvement in
the total data downloaded, which is the objective function, and operational design
variables yield another 40% improvement.
This work was partially supported by NASA through award No. NNX11AI19A — Technical
Monitor: Justin S. Gray. The authors thank Daniel Meinzer, who developed the OpenGLbased exposed area model, Alyssa Francken, who developed the transmitter gain model,
and John Springmann for providing his knowledge of small satellites.
20
X-HALE: Flight Testing and Development of an Unmanned Aeroelastic Test
Vehicle
Jessica R. Jones1, Carlos E.S. Cesnik1
1
An experimental, remotely-piloted aircraft has been designed and fabricated at University
of Michigan that is aeroelastically representative of very flexible aircraft. Known as XHALE, this Experimental High-Altitude Long-Endurance aircraft exhibits geometrically
nonlinear behavior and displays specific, well-characterized aeroelastic traits. This unique
test-bed aircraft is used to study the coupling between the elastic and rigid-body modes
that are typical of very flexible aircraft and gather aeroelastic data to validate existing and
future aeroelastic codes. This poster presents the preliminary data from the initial flight
tests of the lightly instrumented X-HALE Risk Reduction Vehicle that confirm the
airframe’s expected aeroelastic characteristics. This data is also compared with
simulations of the X-HALE generated using the University of Michigan Nonlinear
Aeroelastic Simulation Toolbox. These flight tests also provided data used to inform the
re-design of the fully-instrumented X-HALE platform which will be used in future flight
tests to provide high quality data to support validation of coupled, nonlinear
aeroelastic/flight dynamic codes. This work has been supported by the Air Force
Research Lab, The Boeing Company, and the National Science Foundation.
21
Model predictive control of spacecraft maneuvers using the IPA-SQP
approach
Hyeongjun Park1, Ilya Kolmanovsky1, and Jing Sun2
1
Department of Naval Architecture and Marine Engineering, Department of Electrical Engineering and
Computer Science, University of Michigan
2
A Model Predictive Controller (MPC) based on the Integrated Perturbation Analysis and
Sequential Quadratic Programming (IPA-SQP) is designed and analyzed for spacecraft
relative motion maneuvering. We treat the spacecraft relative motion control problems as
a nonlinear MPC problem and solve it using the IPA-SQP. The IPA-SQP combines the
solutions derived using the Perturbation Analysis (PA) and Sequential Quadratic
Programming (SQP). It obtains the solution to MPC problem using neighboring optimal
control theory for constrained discrete-time systems and then corrects the result using an
SQP update. The combination of PA and SQP improves computational efficiency as
shown in our previous work. In this work, we apply the IPA-SQP MPC to spacecraft
relative motion control problems with thrust magnitude constraints. To evaluate the
effectiveness of the IPA-SQP approach, the simulation results of the IPA-SQP MPC are
compared with the results of the linear quadratic MPC. The fuel consumption is also
evaluated for both approaches. In addition, we present the simulation results of the IPASQP algorithm handling a nonlinear thrust magnitude constraint.
22
RANS-based High Fidelity Aerodynamic Shape Optimization
Peter Zhoujie Lyu1, Joaquim R.R.A. Martins1
1
Aerospace Engineering, University of Michigan
A series of aerodynamic shape optimization for an 800-passenger blended-wing-body
aircraft is performed using Reynolds-averaged Navier--Stokes equations. A gradientbased optimization algorithm and a parallel structured multiblock RANS solver with a
Spalart--Allmaras turbulence model are used. The derivatives are computed using a
discrete adjoint method considering both frozen-turbulence and full-turbulence
assumptions. A total of 274 shape and planform design variables are optimized. The
objective function is the drag coefficient at nominal cruise condition. Lift, trim and center
plane bending moment are constrained. Control surfaces at the rear centerbody are used
to trim the aircraft via a nested free-form deformation volume approach. The optimized
design is trimmed and stable in both on- and off-design conditions. The drag coefficient of
the optimized design is reduced by 37 counts. Trim and bending moment constraints are
satisfied. The addition of planform design variables provide an additional 2 drag count
reduction.
This work was funded by Michigan/AFRL/Boeing Collaborative Center in Aeronautical
Sciences (MAB-CCAS). The computations were performed on Flux HPC at the University
of Michigan CAEN Advanced Computing Center, and Stampede HPC of the Extreme
Science and Engineering Discovery Environment (XSEDE), which is supported by
National Science Foundation grant number OCI-1053575.
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Aerospace Engineering: Fluid
Dynamics, Thermal Sciences
and Combustion
Session Chair: Jacob Davidson
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Chemical Kinetic Modeling for the Oxidation of Branched
AlkanesShao Teng Chong1
1
Department of Mechanical Engineering, University of Michigan, Ann Arbor
The rising cost of petroleum and environmental concerns have stimulated efforts to
advance the production of renewable biomass fuels as potential alternatives to D2 Diesel.
In order to better understand the combustion process of these novel biosynthetic fuels,
the chemical characterization of lightly branched alkanes which appear in high
concentrations in the renewable fuels is required. In the present study, a detailed
chemical kinetic model for 2,5-Dimethylhexane was developed over the temperature
range of 550 - 1500 K, pressures from 0.01 – 10 atm, and equivalence ratios from 0.5 – 1
with Argon or Helium as the diluent. Quantum chemistry ab initio/DFT methods were used
to calculate the bond dissociation energies and generate the potential energy surface.
RRKM/Master Equation simulations were performed to compute pressure and
temperature dependent rate constants for the first oxidation reactions. The proposed rate
constants were based on a previously presented model for 2-methylalkane by Sarathy et
al. 2011. The updated model was validated against new and existing experimental data
from pulsed-photolysis and shock tube experiments. Sensitivity analysis identified the
most important reactions for 2,5-dimethylhexane ignition which is then further refined by
using the solution mapping fractional factorial design method. The proposed model shows
good agreement with all the data obtained from the experimental conditions.
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An optimal HDG-DPG method for advection-diffusion
Johann P.S. Dahm1, Steven M. Kast1, Krzysztof J. Fidkowski1
1
We present a new version of the hybrid discontinuous Galerkin (HDG) finite-element
method that displays optimal convergence in chosen outputs of interest. HDG methods
are a new, efficient approach to numerically solving fluid problems. However, on their own,
they don't achieve optimal stability or output accuracy. To make HDG optimal, we
introduce ideas from discontinous Petrov-Galerkin (DPG) methods, which are provably
optimal in the above respects. We apply our new HDG-DPG method to the advectiondiffusion equation and show that it is both more efficient and accurate than standard
finite-element methods.
This work is funded by the National Science Foundation (NSF) and the Department of
Defense (DoD) through NSF-GRFP and NDSEG fellowships.
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Dynamics of Laser-Induced Cavitation Bubbles
Joel Hartenberger1, Steve Ceccio1,2
1
2
Deptartment of Naval Architecture and Marine Engineering, University of Michigan Ann Arbor
Department of Mechanical Engineering, University of Michigan Ann Arbor
The collapse of cavitation bubbles damages pumps, propellers, and spillways resulting in
reduced performance and costly repairs. Numerous studies of the dynamics of bubble
collapse suggest that this cavitation erosion is primarily the result of a high velocity reentrant jet which forms in the later stages of collapse. However, recent findings suggest
that the shockwave emitted at collapse may also be a significant source of damage. In the
work presented here, a pulsed Nd:YAG laser was used to produce single cavitation
bubbles in a quiescent flow near solid boundaries and video of the consequent bubble
growth and collapse was recorded using a high-speed camera. Simultaneously, a needle
hydrophone recorded the impulse generated during bubble collapse. The needle probe
was used to spatially and temporally resolve the pressures of the impulses created by
both the re-entrant jet and shockwave at collapse.
The authors thank the Office of Naval Research (ONR) for funding this work and Prof.
Eric Johnsen and Renaud Gaudron for their insights into single cavitation bubble
collapse.
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A study of the entrainment and mixing of co- and counter-flowing gas in
confined turbulent jets used for industrial combustion
I. S. Lee1 and A. Atreya1
1
Department of Mechanical Engineering, University of Michigan at Ann Arbor
Confined reacting turbulent jets are widely used in industrial furnaces. The flame pattern
and emissions of confined turbulent jet flames are influenced by the jet interaction and
mixing. This paper presents the results of an experimental and numerical investigation of
mixing and entrainment characteristics in a confined, non-reacting turbulent jet. This is a
basic first step toward understanding the confined reacting jets. The experiments were
designed to simulate exhaust flow from co- or counter-flowing 1 to 10 MMBtu industrialscale burners. NO was used as a tracer gas to determine mixing and entrainment. The
apparatus consists of: (i) a 20 inch inner diameter, 6ft long cylindrical vertical duct that
carries 328.15 K (slightly hot) air at co- or counter-flow velocities ranging from 0.61 to
3.12 m/s, (ii) and an ambient temperature high velocity air jet containing NO as a tracer
gas which is discharged by a ¼ inch nozzle in the center of the vertical duct. Radial profile
measurements of stream wise velocity, composition, and temperature are made along the
length of the jet to determine the extent of entrainment and the dilution of the jet fluid as a
function of the co- or counter-flow velocities, as well as,jet flow velocities. Numerical
calculations using FLUENT are conducted to determine the details of the flow field. These
calculations essentially confirm the experimental results and provide a picture of the flow
field. These results provide fundamental information on entrainment and flow
characteristics of confined jets used in industry.
28
Nanoparticle growth mechanisms in flames
Jeffrey Lowe1, Paolo Elvati2, and Angela Violi1,2,3,4,5
1
Department of Chemical Engineering, University of Michigan
Department of Mechanical Engineering, University of Michigan
3
Department of Biomedical Engineering, University of Michigan
4
Department of Macromolecular Science, University of Michigan
5
Department of Applied Physics, University of Michigan
2
The widespread emission of carbonaceous nanoparticles (CNPs) from combustion
engines poses a significant health risk to humans; therefore, CNP formation has been
studied by the combustion community in great detail. The community has deduced that
CNP formation consists of a number of steps involving both chemical and physical growth
mechanisms. However, the particle nucleation step, or the transition from gas-phase
particles to solid-phase particles, is not well understood. Our work aims at developing a
more complete picture of the particle nucleation process by studying a possible
mechanism: the dimerization of aliphatic-substituted polycyclic aromatic hydrocarbons
(PAHs). Specifically, we have quantified the effect of geometry on the free energy stability
of dimerized compounds of PAHs with saturated and unsaturated chains. We employed
molecular dynamics techniques coupled with the well-tempered metadynamics algorithm
to measure the free energy surfaces (FESs) of dimerization between compounds of
interest. We found that molecules with saturated chains display an increase in stability
with an increase in the number of substituted chains whereas molecules with unsaturated
chains have stabilities relatively unaffected by the number of chains. Further, we
determined that monomer structure affects the shape of the FES of substituted PAHs.
Some substituted PAHs displayed broader minima on their FESs, showcasing the
remarkable stability of a range of dimer configurations for those PAHs. These results
demonstrate the feasibility of the dimerization of aliphatic-substituted PAHs as a particle
nucleation model and add another level of theory to the development of a predictive code
to model CNP formation.
This research was funded by the Department of Energy, Office of Basic Energy Sciences,
Division of Chemical Sciences, Geosciences, and Biosciences under Contract No. DESC0002619
29
High-pressure low-temperature ignition behavior of syngas mixtures
A.B. Mansfield1, M.S. Wooldridge2
1
2
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109
Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109
Ignition properties of simulated syngas mixtures were systematically investigated at highpressure low-temperature conditions relevant to gas turbine combustor operation using
the University of Michigan Rapid Compression Facility.
Pressure time-history
measurements and high-speed imaging of the ignition process were used to determine
auto-ignition delay times and observe ignition behaviors. The simulated syngas mixtures
were composed of H2 and CO with a molar ratio of 0.7, for equivalence ratios (φ) of 0.1
and 0.5, near air dilution, with N2 as the primary diluent gas. The pressures and
temperatures after compression ranged from 3 – 15 atm and 870 – 1150 K.
Inhomogeneous ignition behaviors were evident for all mixtures at some thermodynamic
conditions, characterized by localized flame-like structures. Analysis of the behavior
revealed a strong dependence of the ignition behavior on the dominant H 2/O2 chemistry,
suggesting that thermal sensitivity of the auto-ignition delay time is an important factor in
the occurrence of inhomogeneous ignition. The proposition, calculation, and comparison
of a criterion for thermal sensitivity revealed critical values of 0.7 ms/K for φ = 0.1 and
0.04 ms/K for φ = 0.5; where any region (i.e. state and mixture conditions) with a
sensitivity value in excess of this critical limit exhibited inhomogeneous ignition
phenomena and any region with a lower value exhibited only homogeneous ignition. The
thermal sensitivity metric and the ignition behavior maps created in the present work
provide important tools for understanding and validating ignition chemistry and behaviors
as well as powerful tools for the design of combustion devices using syngas fuels.
The authors acknowledge the generous support of the U.S. Department of Energy via the
National Energy Technology Laboratory, Award Number DE-FE0007465 and the
Department of Mechanical Engineering at the University of Michigan.
30
Modeling Ramjet Engine Transient Behavior: A Quasi 1D Approach
Christopher Marley1, James Driscoll1
1
The transient behavior of a ramjet engine is investigated. The engine comprises of a
converging-diverging inlet with a normal shock in the diverging section, a combustor and
a propulsive nozzle. The assumption of quasi-steady flow, which can be valid for
simulating turbojet engines, is of particular interest in this study. The model is based on
the unsteady quasi-one-dimensional Euler equations with a thermally perfect gas; the
combustor is modeled as a heat addition source term in the energy equation. A throttling
maneuver is simulated and the thrust response is compared to the response from a
similarly modeled turbojet engine. The dynamic response of a gas-turbine engine is
dominated by the relatively slow shaft dynamics and hence the flow can be accurately
modeling as quasi-steady. As expected, the results of this study indicate that the quasisteady assumption is not valid for modeling the transient performance of a ramjet. This
unsteady quasi-one-dimensional ramjet model has important implications in
understanding the highly transient phenomenon of engine unstart. A transient reduced
order model is obtained by applying proper orthogonal decomposition to the quasi-onedimensional model. This reduced order model can be used in stability analysis of the
engine inlet shock and for controller design to avoid engine unstart.
31
Stability of a Hanging Pendant Drop
Parameshwaran Pasupathy1, Behrouz Shiari2
1
National Nanotechnology Infrastructure Network, Electrical Engineering and Computer Science
Department, University of Michigan
2
The Hanging Drop Method has various applications in life sciences research such as anticancer drug sensitivity testing. It provides for high throughput capabilities and offers
several advantages over conventional spheroid cell culture methods. In the paper, the
Finite Element Method is used to study a pendant drop (hanging drop) hanging under
gravity. The formation of a hanging drop in a micro-fluidic channel and its stability is
investigated by simulating the problem as a two phase flow. The level set method
available in the micro-fluidics module in COMSOL is used for the analysis. Parametric
studies have been carried out to evaluate the size and stability of the drop with respect to
varying channel geometry, contact angle and boundary conditions. It is observed that
volume of the droplet increases with height until a maximum value is reached and the
droplet remains stable as long as its volume increases with height. In addition, 3D
simulations of a hanging drop are performed to study the stability of the drop in a
rectangular channel.
Support
from
the
NNIN
Michigan is gratefully acknowledged.
32
computation
program
(NNIN/C)
at
Cavitation rheology in finite volume limits: Using bubbles to measure the
elasticity of small volumes of viscoelastic biomaterials
Leonid Pavlovsky1, Mahesh Ganesan1, John G. Younger2, and Michael J. Solomon1
1
2
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
Department of Emergency Medicine, University of Michigan, Ann Arbor, MI 48109
We evaluate the application of cavitation rheology to characterize the elasticity of
biological soft matter that may be confined to volumes as small as 1 µL. Cavitation
rheology, a technique developed by Zimberlin et. al (Soft Matter, 3(6), 765-767, 2007), is
a simple, rapid method to characterize the mechanical properties of materials that can be
approximated as linearly elastic by creating a bubble, or cavity, in a relatively small
volume of the material. This technique relates the critical pressure necessary to form the
cavity to the material elasticity in a limit where the bubble size is small relative to size of
the specimen. For characterization of small volumes of biological soft matter, such as
surface adherent bacterial biofilms, this method must be extended to accommodate
situations in which the cavitation volume is finite relative to the specimen volume. We
therefore investigated the underlying principles of cavitation rheology. From basic
elasticity theory, we mathematically related the critical pressure to the sample elasticity
for finite sample volumes and evaluated the results by numerical simulation. We use
semi-dilute solutions of polyethylene oxide (PEO) to test the performance of cavitation
rheology in the limit of small volumes and applied the method to evaluate the elasticity of
Staphylococcus epidermidis biofilms.
This work was funded, in part, by the NSF CDI Program and NIGMS.
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Simulations of Shockwave Propagation in Viscoelastic Media
Mauro Rodriguez1, Eric Johnsen1
1
Department of Mechanical Engineering, University of Michigan at Ann-Arbor
Understanding the mechanics of shock waves emitted by cavitation bubbles and
propagating through viscoelastic media is important to various naval and medical
applications, particularly in the context of cavitation damage. In such problems, the
constitutive models describing the material are non-trivial, and include effects such as
nonlinear elasticity, history and viscosity. Thus, the influence of the shock on the material
and the response of the material to the shock are generally unknown. A novel numerical
approach is proposed for simulating shock and acoustic-wave propagation in a Zener-like
viscoelastic medium. The method is based on a high-order accurate weighted essentially
non-oscillatory (WENO) scheme for shock capturing and introduces evolution equations
for the stresses. The HLLC Riemann solver is used for upwinding, with a reconstruction of
the primitive variables. The performance and accuracy of the numerical approach is
presented for several one- and two-dimensional problems, including acoustic wave
propagation and the Sod shock tube problem for various combinations of elasticities,
viscosities and relaxation times. This work is supported by ONR grant N00014-12-1-0751.
34
A Computationally Efficient Thermodynamic Model of Boosted HCCI
Combustion for Engine Systems Analysis
Prasad S. Shingne1, Janardhan Kodavasal2, Dennis N. Assanis3 and Jason B. Martz1
1
Walter E Lay Automotive Laboratory, University of Michigan, Ann Arbor, MI, USA
Argonne National Laboratory, Lemont, IL, USA
3
Stony Brook University, Stony Brook, NY, USA
2
As the global energy crisis worsens and the effects of climate change become dire there
is pressing need for more efficient transportation. Homogeneous Charge Compression
Ignition (HCCI) has been a topic of widespread research due to its potential of reducing in
cylinder NOx and particulate emissions while maintaining high thermal efficiencies.
Typically a large number of experiments are required in order to define engine systems
and strategies suitable for a new combustion mode such as HCCI. This poster presents a
model for boosted HCCI combustion for use in thermodynamic engine cycle simulations.
The model consists of two parts; an ignition model which predicts the location of ignition
and burn model which predicts the rate of combustion. Ignition model uses an autoignition integral (AI) with an ignition delay term that is provided with the temperature of the
adiabatic core, computed thermodynamically at each time step. The adiabatic core model
has been validated against motored as well as reacting CFD simulations; predicted
adiabatic core temperatures are within 1% of the peak charge temperature at TDC from
motored CFD simulations. The burn profile is modeled as a Wiebe curve fit with
experimental data collected over a wide range of engine operating conditions, with the
locations of ignition, 10% and 75% mass fraction of fuel burned (MFB). The 10% and
75% MFB locations are correlated as a function of the location of auto-ignition and the
conditions at intake valve closing (IVC). The combustion model is implemented into GTPower and validated against experimental HCCI.
This material is based upon work supported by the Department of Energy [National
Energy Technology Laboratory] under Award Number(s) DE-EE0003533. This work is
performed as a part of the ACCESS project consortium (Robert Bosch LLC, AVL Inc.,
Emitec Inc., Stanford University, and University of Michigan) under the direction of PI
Hakan Yilmaz and Co-PI Oliver Miersch-Wiemers, Robert Bosch LLC. The authors also
acknowledge Jeff Sterniak from Robert Bosch LLC for providing experimental data for the
burn rate model and many useful discussions.
35
An Extreme Learning Machine Approach to Predicting Near Chaotic HCCI
Combustion Phasing in Real-Time
Adam Vaughan1
1
Homogeneous Charge Compression Ignition (HCCI) is an advanced low temperature
combustion strategy that can simultaneously improve engine fuel efficiency and
dramatically lower smog precursor production (i.e. NOx). Unfortunately, broad usage of
gasoline HCCI is hampered by combustion instabilities and a limited operation envelope.
Difficulties also include highly non-linear chemistry, almost chaotic period doubling
bifurcation(s), turbulent mixing, model parameters that can drift day-to-day, combustion
deposits, and mixture state information that is typically not available cycle-to-cycle,
especially during transients. As an alternative to traditional physics based, controloriented models that often struggle with the aforementioned processes, this work
proposes an online adaptive machine learning approach that is specifically aimed at
enabling cycle-to-cycle predictions at the HCCI stability limit on a multi-cylinder engine.
This fully causal method is shown to account for 79% of the cycle-to-cycle combustion
phasing variance across a wide variety of random transient and steady-state conditions,
right up to complete engine misfire. The hope is that this new modeling framework will
enable a new class of cycle-to-cycle predictive control strategies that extend HCCI’s
constrained load envelope. To this end, ongoing experimental work is being done to
explore predictive control using this new approach and custom developed electronic
hardware for the low-cost Raspberry Pi platform.
The author thanks his co-advisors Dr. Stanislav V. Bohac and Prof. Claus Borgnakke for
their support, Dr. Vijay Janakiraman for providing the raw data analyzed in this work, and
Jeff Sterniak for both his test cell and project support.
This material is based upon work supported by the Department of Energy [National
Energy Technology Laboratory] under Award Number(s) DE-EE0003533. This work is
performed as a part of the ACCESS project consortium (Robert Bosch LLC, AVL Inc.,
Emitec Inc., Stanford University, University of Michigan) under the direction of PI Hakan
Yilmaz and Co-PI Oliver Miersch-Wiemers, Robert Bosch LLC.
36
Atmospheric, Oceanic, and
Space Sciences:
Atmospheric & Climate
Sciences
Session Chair: Aravind Venkitasubramony
37
Synoptic and local controls on precipitation patterns in the Great Lakes
region
Alexander M. Bryan1, Guiling Wang2, Derek Posselt1, Allison L Steiner1
1
2
Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan
Department of Civil and Environmental Engineering, University of Connecticut
Using the Regional Climate Model coupled with the Community Land Model (RegCMCLM), we examine the role of synoptic versus local processes on precipitation processes
in the Great Lakes Region. Synoptic processes are examined through the selection of
varying lateral boundary conditions, and local processes are examined through the land
and lake feedbacks. Both can affect the magnitude and distribution of precipitation, and
the Great Lakes region is one that is particularly sensitive to both forces. First, we
consider the individual effects of climate and land use change by simulating present-day
(1980–2004) and future (2041–2065) precipitation under changing climate and land use
independently. To assess the large-scale influences of synoptic meteorology on
precipitation patterns, we then compare two present-day simulations driven by two
contrasting global circulation models: the Earth-System component of the Hadley Centre
Global Environment Model version 2 (HadGEM2-ES) and the Geophysical Fluid
Dynamics Laboratory Earth System Model version 2 with GFDL’s Modular Ocean Model
version 4.1 (GFDL-ESM2M). For the local influences on precipitation, we investigate
deficiencies in latent heat release and examine the sensitivity of precipitation to terrestrial
evapotranspiration. While large-scale boundary conditions can influence the simulation of
precipitation in the region, the local feedbacks also play an important role and suggest the
need for improved parameterizations of surface layer processes controlling fluxes across
the surface boundary condition. Funding for this work was provided by the National
Science Foundation under Grant No. 1039043.
38
Spectral Dependence of the Response Time of Sea State to Local Wind
Forcing
David D. Chen1, Scott Gleason2, Chris Ruf1, Mounir Adjrad3
1
Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI, USA
Department of Electrical and Computer Engineering, Concordia University, Montreal, Québec, Canada
3
Department of Electronic and Electrical Engineering, University College London, London, UK
2
Measurements of wind near the surface of the ocean are essential to the determination of
momentum and energy fluxes at the air/sea interface and to the forecasting of weather
phenomena such as hurricanes. Bistatic remote sensing using L-band GPS signals has
been proposed as an alternative to the conventional microwave radiometers and
monostatic radar scatterometers for spaceborne ocean surface windspeed
measurements. L-band waves can easily penetrate precipitation, and the cost and
accommodation requirements of GPS receivers are significantly lower than their
radiometer and scatterometer counterparts. However, L-band scattered signals are
sensitive to waves with longer wavelengths than those sensed by conventional
radiometers and scatterometers, which typically operate at higher frequencies. It is known
that longer surface waves take more time to respond to surface winds, propagate further
before decaying, and are generally less directly coupled to the local wind field. These
factors could affect the ability of scattered GPS L-band signals to retrieve local wind
fields. In this work, we attempt to quantify the relationship between the longwave
spectrum and local winds by examining windspeed and surface slope measurements by
buoys. Specifically, by applying a lag-correlator, it is observed that the average lag time
decreases monotonically as the ocean surface wavelength decreases. It is found that 1
hour serves as a conservative upper bound on the average response time of L-band
waves to local wind forcing.
This work is funded by a NASA Earth and Space Science Fellowship (NESSF).
39
Sensitivities of AGCM-Simulated Tropical Cyclones to Varying Initial
Conditions
Fei He1, Derek J. Posselt1, Naveen N. Narisetty2, Colin M. Zarzycki1, and Vijayan N. Nair2
1
2
Department of Atmospheric, Oceanic and Space Science, University of Michigan
Department of Statistics, University of Michigan
This study examines how the development of Tropical Cyclones (TCs) is represented in
Atmospheric General circulation Models (AGCMs) and assesses the impact of changes in
initial conditions on modeled TCs. The National Center for Atmospheric Research
(NCAR) Community Atmosphere Model (CAM) has been used to simulate the
development of idealized TCs over 10 days. A Latin Hypercube Sampling (LHS) method
is used to generate two 300-member space-filling ensembles of simulations with grid
resolution of 1 ´1 and 0.5 ´ 0.5 , respectively. Composite analysis is first used to analyze
the ensemble results, then, the Expanded Multivariate Adaptive Regression Splines
(EMARS) method is implemented to characterize various TC response functions. Both 0.5
and 1.0 degree simulations produce a wide range of TC intensities ranging from tropical
depression to category 5 on the Saffir-Simpson scale. On average, storms in the higher
resolution simulations are stronger than those produced by the coarser-resolution model.
Specifically, it is found that (1) the intensity, track, cloud, precipitation and radiative fields
of simulated TCs are highly sensitive to changes in the initial vortex characteristics and
surrounding environment; (2) nonlinear interaction between the initial conditions is crucial
to the distribution of clouds, precipitation, and radiation of simulated TCs; (3) favorable
initial conditions are able to produce intense and destructive TCs even in 1 ´1 resolution
global climate models.
40
The role of pollution state on urban heat islands in the Midwestern United
States
Stacey Kawecki1,Allison Steiner1, David Stensrud2,Larissa Reames3,Geoffrey Henebry4
1
NOAA/National Severe Storms Laboratory
3
School of Meteorology, University of Oklahoma
4
Geospatial Sciences Center of Excellence, South Dakota State University
2
Concentrations of anthropogenic greenhouse gases and other pollutants are magnified in
urban areas and likely affect urban heat islands (UHIs). UHIs are defined by temperatures
in the urban core that are warmer relative to nearby rural areas. These warmer
temperatures alter atmospheric stability, cloud and precipitation formation, and increase
photochemical smog production. However, the air quality-UHI link remains unquantified.
Here we assess the chemical contribution of pollution state to the UHI. We focus on small
to medium-sized (population ranging from 300,000 to 1.2 million) cities in the Great
Plains, a region known for its springtime extreme weather and good to moderate air
quality. We investigate the urban pollution state using satellite and ground-based
observations for aerosol optical depth (AOD), nitrogen dioxide (NO 2: an important
anthropogenic precursor for ozone formation), and ozone (O3: a greenhouse gas). To
isolate the chemical effects of urban pollution on the UHI, we simulate an isolated
supercell thunderstorm crossing the Oklahoma City urban area using the WRF-Chem
model. One simulation includes the physical effects of the UHI over Oklahoma City during
a severe convective event. The second simulation further incorporates the radiative
effects of short-lived climate forcing agents such as aerosols and tropospheric ozone and
its precursors to determine the chemical contribution to the UHI. Through these
simulations with and without atmospheric chemistry, we assess the chemical contribution
to the UHI and the formation and sustenance of this severe weather event.
41
Numerical modeling of the energy balance and the englacial temperature of
Greenland Ice Sheet
Xiaojian Liu1, Jeremy N. Bassis1
1
The surface mass and energy balance of ice sheets links the response of ice sheets to
atmospheric forcing. Historically, ice sheet model have relied on empirical
parameterizations of these surface processes. More recently, global and regional climate
models (e.g., RACKMO, MAR) have begun to incorporate sophisticated surface process
models in an attempt to simulate ice sheet mass balance using a more physically based
modeling approach. In this study we explore the limits of simple downscaling techniques
to obtain the appropriate atmospheric forcing for surface energy balance models from
global reanalysis products and evaluate the partition of uncertainties associated with
downscaling and with various albedo, turbulent energy transfer and densification
parameterizations. To accomplish this we have developed a simple physically based
numerical model of the coupled radiation, snow and ice system has been developed. The
model is a one-dimensional multi-layer snow and ice model that accounts for both the
surface energy balance and subsurface heating to evaluate the energy and mass balance
in the upper part of Greenland Ice Sheet and calculates the surface energy balance,
temperature and density evolution in the uppermost part of ice. It is run over the full
annual cycle, simulating melting, temperature and density profiles throughout the
seasons. We assess uncertainty in the forcing by driving the model using
downscaled ECMWF ERA-Interim reanalysis data and comparing this with forcing derived
from in situ AWS stations from Greenland AWS data and performs sensitivity studies for
the albedo, turbulent fluxes and densification.
42
Is the earth flat or only the models are telling so
Yue Ma1, Jeremy Bassis2
1
2
Department of Physics, University of Michigan
Department of Atmospheric, Oceanic and Space Sciences, University of Michigan
At this moment, most models are using polar stereographic projection to treat ice sheets
on a flat earth. Under the current conditions where most ice sheets are relatively small in
size, the approximation provides acceptable results. However, as the size of ice sheet
increases, the difference introduced by the assumption of a flat earth would become
obvious. We address this point by starting from the known Vialov profile and solving the
ice thickness equations in spherical coordinates without having to compromise the
simplicity of solutions. The difference between results on a flat and a round earth is
noticeable when the size of the ice sheet is comparable to the radius of the earth (~7 km)
or in other words big enough to cover a quarter of earth's surface. On the other hand, the
higher creep exponent n, the less discrepancy between ice sheets on a flat and a round
earth.
43
Design, Modeling, and In-situ Verification of WiBAR as Snowpack/Lake Ice
Thickness Sensor
Hamid Nejati1, Sing Y. E. Wong1, Roger D. De Roo2, Lin van Nieuwstadt2, Kamal
Sarabandi1, and Anthony W. England1,2
1
2
Departament of Electrical Engineering and Computer Science, University of Michigan
Wideband autocorrelation radiometer (WiBAR) enables us to measure the physical
characteristics of layered media. Due to multiple reflections occurring within the layered
media, the autocorrelation response of the received signal demonstrates distinct peaks
corresponding to the travel times of subsequent reflections. Since the Fourier transform of
the autocorrelation response gives the power spectral data, monitoring the received
power spectral data enables the extraction of physical characteristics of the layered
media.
We have successfully implemented WiBAR in the frequency range of 7− 10GHz by
connecting a high gain pyramidal horn antenna to a wideband amplifier chain. The output
is then monitored using a handheld spectrum analyzer. The sensitivity of the implemented
WiBAR is tuned by setting the resolution and video bandwidths of the spectrum analyzer.
WiBAR adopts a different calibration procedure from typical radiometers, since the
absolute temperature measurement is not required in WiBAR.
We have gathered the H-polarized far field measurements of snow covered terrains/ lake
ice using our implemented WiBAR over some locations in Ann Arbor and Houghton, MI.
The estimation of the snow thickness requires a good approximation of snow dielectric
constant. We have used the refractive index mixing formula using the ice density of the
snow that we have measured in site. The reconstructed estimated snow thicknesses are
in good agreement with in-situ measurements. The accuracy of our device in measuring
snow/ice thicknesses are within 1cm.
44
Comparison of a Moist Idealized Test Case and Aquaplanet Simulations in
an Atmospheric General Circulation Model
Diana Thatcher1 and Christiane Jablonowski1
1
The vast array of dynamical and physical processes within atmospheric general
circulation models (GCMs) makes it difficult to correctly isolate sources of model errors.
Simplified test cases are important in testing the accuracy of individual model
components, such as the fluid flow component in the dynamical core. Typically, dynamical
cores are coupled to complex subgrid-scale physical parameterization packages, and
nonlinear interactions between various components of the model mask the causes and
effects of atmospheric phenomena. Idealized tests are a computationally efficient method
for analyzing the underlying numerical techniques of dynamical cores. The proposed test
case is based on the widely-used test for dry dynamical cores by Held and Suarez, which
replaces the full physical parameterization package with temperature relaxation and
damping of low-level winds on an idealized planet. The impact of moisture, a crucial
physics-dynamics coupling process, is missing from this test.
Here we present an idealized test case of intermediate complexity with moisture
feedbacks. It uses simplified physical processes to model large-scale condensation,
boundary layer turbulence, and surface fluxes of horizontal momentum, latent heat, and
sensible heat between the atmosphere and an ocean-covered planet. We apply this test
to the Spectral Element (SE) dynamical core within the NSF/DoE Community Atmosphere
Model (CAM) version 5.3 and compare the results to aqua-planet experiments with
complex physical parameterizations. The moist idealized test case successfully
reproduces many features of the general circulation seen in the aqua-planet simulations,
such as the Hadley cell, precipitation patterns, and atmospheric waves.
45
Atmospheric, Oceanic, and
Space Sciences:
Atmospheric & Climate
Sciences
Session Chair: Aravind Venkitasubramony
46
Statistical Storm-Time Examination of MLT Dependent Plasmapause
Location Derived from IMAGE EUV
R. M. Katus1, D. L. Gallagher2, M. W. Liemohn1, and J. Goldstein3
1
Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI, United
States.
2
Marshall Space Flight Center (MSFC), NASA, Huntsville, AL, United States.
3
Southwest Research Institute (SwRI), San Antonio, TX, United States.
The location of the outer edge of the plasmaphere (the plasmapause) as a function of
geomagnetic storm-time is investigated statistically in terms of the solar wind driver.
Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Extreme Ultraviolet
(EUV) data is used in an automated plasmapause extraction. The extraction technique
searches a set range of possible plasmasphere densities for a maximum gradient. The
MLT dependent plasmapause results are then compared to manual extractions. The
plasmapause results are then examined along a normalized epoch storm timeline to
determine the average plasmapause Lshell as a function of MLT and storm time. The
smoothness of the plasmapause is inspected to describe the spatial scale of the electric
field. The results are then investigated in terms of the solar wind driver and the storm
intensity.
47
Automated tracking of changes to terminus position of Greenland’s marine
outlet glaciers
Fiona Seifert 1, Charles Galey2, Jeremy Bassis1
1
Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI, United
States.
2
Mission Systems Concepts, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA,
United States.
Mass loss from the Greenland ice Sheet is primarily through the dynamic changes of its
marine terminating outlet glaciers. Understanding the behavior of these glaciers is
therefore key to understanding how much the ice sheet will contribute to sea level in the
next century. Glacier behavior is, however, complex, with wide disparities in behavior
even between glaciers that occupy adjacent fjords. Deciphering the multitude of factors
that control glacier behavior requires a comprehensive dataset of near daily changes in
terminus position for a large set of glaciers over many years. The creation of this dataset
has been difficult due to the time required to process the changes manually. Evolution in
computational methods allows the creation of an automated algorithm, using a
combination of filtering techniques and edge detection, which ingests MODIS imagery
and tracks changes to (i) the terminus position and (ii) the areal extent of mélange
downstream of the terminus. We tested the algorithm on several well-studied glaciers
including Jakobshavn, Helheim, and Kangerdlugssuaq. Comparison with manually
identified terminus positions proved the algorithm accurate to within +/- 2 pixels (500 m).
The validated model was then applied to a larger set of Greenland’s marine terminating
outlet glaciers. We use this higher temporal resolution dataset to determine statistical
patterns to the calving events and ask whether these patterns are linked to mélange
extent, fjord geometry, and any seasonal component affecting the regularity of the events.
48
Examination of Nonlinearities in the Van Allen Probes Data During
Geomagnetic Storms
Lois Keller Smith1, Michael Liemohn1
1
In the recently released Van Allen Probes data, signatures indicating geomagnetic activity
were examined closely. In particular, we chose several different storms throughout 20122013 where a large ionized oxygen flux was seen in conjunction with a significant drop in
the disturbed storm time (DST) index. For these storms, the electric and magnetic fields in
a Cartesian coordinate system were analyzed for coupled nonlinearities. Preliminary
results show that during storm time, the magnetic field in the z direction will drop
dramatically, sometimes reversing direction in extreme situations. The results of this work
give a clearer picture of the behavior of the inner magnetosphere during storm times.
49
Coronal sources, elemental fractionation, and release mechanisms of heavy
ion dropouts in the solar wind
Micah J. Weberg1, Thomas H. Zurbuchen1, and Susan T. Lepri1
1
The elemental abundances of heavy ions (m > He) in the solar wind provide information
concerning physical processes occurring in the corona. Additionally, the charge state
distributions of these heavy ions are sensitive to the temperature profiles of their
respective source regions in the corona. Both the abundances and charge states become
set within a few solar radii and propagate unchanged throughout the heliosphere,
regardless of turbulence, propagation effects, and local heating. Therefore, heavy ions
yield in-situ evidence of an environment inaccessible to spacecraft and traditionally only
observed via spectroscopy.
Heavy ion dropouts are a relatively new class of solar wind events. Their origins lie in
large, closed coronal loops where processes such as gravitational settling dominate and
can cause a mass-dependent fractionation pattern. In this study we consider and attempt
to answer three fundamental questions concerning heavy ion dropouts: (1) Where are the
source loops located in the large scale corona? (2) How does the interplay between
coronal processes influence the end elemental abundances?, and (3) What are the most
probable release mechanisms?. We begin by analyzing the temporal and spatial
variability of heavy ion dropouts and their correlation with heliospheric plasma and
magnetic structures. Next we investigate the ordering of the elements inside dropouts
with respect to mass, charge state, and First Ionization Potential. Finally, we consider the
prevailing solar wind theories and the processes they posit that may be responsible for
the release of coronal plasma into interplanetary space.
50
Searching for Separatrix-Web Signatures in the Solar Wind
A. Young1, M. Stakhiv1, T. Zurbuchen1, J. Linker2, S. Antiochos3
1
Predictive Science, Inc.
3
Goddard Space Flight Center, NASA
2
There are two types of solar wind emanating from the sun. The fast wind has speeds of
600-800 km/s and is known to originate from coronal holes. The slow wind ranges from
450-600 km/s and has a higher average charge-state composition. This suggests its
source exists in the corona where temperatures are known to be 1.0 million degrees. This
is supported by spectroscopic measurements of the corona showing elemental
abundances matching those found in slow solar wind. It is unknown how the slow wind
escapes from a region where the dominant magnetic field is closed rather than open to
the solar wind. The separatrix-web (S-Web) theory proposes that a web of interface
regions, existing along the boundaries of coronal holes, is continuously undergoing
magnetic reconnection. This would allow closed magnetic field to become open and
release hot plasma into the heliosphere. These interface regions, where reconnection is
highly likely, can be found by looking for where neighboring field lines diverge quickly.
This divergent property is quantized by the “squashing factor” (Q). Values of Q have been
calculated from magneto-hydrodynamic simulations of the heliosphere, where observed
photospheric magnetic field maps were used as an initial condition. By taking the values
of Q calculated in these simulations and comparing to in-situ data such as speed,
elemental charge-state, and compositional charge-state, we should be able to detect
signatures of the S-Web in the solar wind measured at Earth.
The authors acknowledge Ben Lynch and Justin Edmondson for their collaboration.
51
Biomedical Engineering
Session Chair: Barry Belmont
52
Development of Acid-Sensitive Micelles for Targeted
Chemotherapeutic Agents to Cancer Lesions in Bone
Delivery
of
Omer Aydin1, Yasemin Yuksel Durmaz1, Mohamed E. H. ElSayed1
1
Prostate cancer (PC) is the 2nd leading cause of cancer related deaths in U.S. men.
Metastasized PC to other organs (e.g. bone) has posed a significant challenge because
of the inability to deliver therapeutic concentrations of anticancer drugs (e.g. cabazitaxel;
CTX) to PC lesions in bone. Further, systemic administration of chemotherapeutic agents
has been associated with major side effects (e.g. neutropenia, renal cytotoxicity, and
peripheral edema). To address current therapeutic limitations, we have developed a new
tri-block copolymer composed of a hydrophilic polyethylene glycol (PEG) block, a central
polyacrylic acid (PAA) block, and hydrophobic polymethylmethacrylate (PMMA) block
sequentially linked via “click” coupling. This tri-block copolymer self-assembles in
aqueous solutions forming nano-sized non-shell cross-linked micelles (NSCL, 25.2 ± 2.1
nm). To increase the stability of micelles in aqueous environments, we introduced
glutaraldehyde as a cross-linker that is able to react with NH2 functional groups of the
functionalized PAA block of the copolymer forming acid-labile hydrazone linkages (SCL
Micelles, 28.2± 3.1nm). Further, we encapsulated model drug Nile Red (NR) and CTX,
achieving 80% and 55% encapsulation efficiency rates and 8% and 10% loading ratios,
respectively. Meanwhile, we investigated the release profiles of NR and CTX from NSCL
and SCL micelles at pH 7.4 and 5.0. The model drugs are significantly arrested in SCL
micelles at pH 7.4 with minimal burst release, while they are gradually released in acidic
pH, as compared to NSCL and SCL micelles at pH 5.0. Current investigation focuses on
anti-cancer activity of the particles on PC cell lines. These results indicate pH-sensitive,
CTX-loaded SCL micelles can potentially achieve tunable CTX release in tumor lesion,
which can selectively kill tumor cells while limiting systemic side effects.
Acknowledgement: The Univeristy of Michigan Prostate Specialized Programs of
Research Excellence (SPORE), Republic of Turkey the Ministry of National Education
(1416), Sanofi-Aventis.
53
Home away from home: recreating the metabolic and proliferative
microenvironment of disseminated tumor cells within a 3D bone marrow
niche.
Stephen P. Cavnar1, Brendan Leung1, Sasha Cai Lesher-Perez1, Rahul Iyengar1, Kathryn
E. Luker2, Shuichi Takayama1,3, and Gary D. Luker1,2,4
1
Center for Molecular Imaging, Department of Radiology, University of Michigan Medical School
3
Department of Macromolecular Sciences, University of Michigan
4
Department of Microbiology and Immunology, University of Michigan Medical School
2
Identifying and therapeutically targeting disseminated tumor cells is a major hurdle in
limiting disease recurrence and improving survival of cancer patients. Chemotherapeutic
drugs often target rapidly dividing and metabolically active cancer cells, which is effective
in debulking the primary tumor. However, disseminated tumor cells, particularly those
that reach the bone marrow, often become dormant with limited/no proliferation, resist
many chemotherapies, and potentially seed disease recurrence years later. We use a 3D
tissue model of the bone marrow niche to study how the bone marrow stroma confers
drug resistance and cancer dormancy.
Using this system we evaluate the
chemotherapeutic sensitivity of multiple breast cancer cell lines within 2D and 3D bone
marrow niche co-cultures. We corroborate 3D drug sensitivities using autofluorescence
redox imaging, fluorescent cell cycle indicators, and bioluminescence imaging, which
measure the metabolic status, cell cycle, and cancer burden in the bone marrow niche,
respectively. Using this system we expect to recreate long-term drug resistance and
disease relapse, to screen therapeutic candidates specific to dormant cancer cells, and to
optimize dosing as to limit toxicities to normal bone marrow cells.
S.P.C. was funded on the Proteome Informatics of Cancer Training Program #T32
CA140044 and the National Science Foundation Graduate Research Fellowship
Program. The project was also funded by the Provocative Questions Grant #R01
CA170198-01.
54
Chronically-stable recording neural microprobes with deployed electrodes
and vertical stiffeners
Daniel Egert1 and Khalil Najafi1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI
Motor neuroprosthetics aid the paralyzed to regain independence by controlling artificial
limbs with signals recorded from the brain. Clinical pilot studies on these devices are
presently being employed. A key requirement for control of motor neuroprosthetics is the
ability to record brain activity of awake, freely behaving hosts accurately enough to
distinguish action potentials of single neuron. To date, only neural probes implanted into
the brain can provide the required specificity. However, the high spatial resolution of
these neural probes comes at the cost of a high degree of invasiveness; the host immune
response inhibits recording over a patient’s lifetime.
This project pursues two technologies to mitigate the immune response to implanted
neural probes and its impact on their performance. The developed neural probes consist
of silicon or Parylene formed into millimeter-long, needle-like shanks hosting multiple
microelectrodes. Following the first technology, individual electrodes are placed at the
end of very fine and flexible needle extensions, supported by the shank. Before
implantation the needles are locked into a protected position close to the shank using
biodissolvable glue. After implantation they deploy away from the shank into healthy
tissue, where they act like satellites, floating almost freely inside the brain tissue. This is
expected to greatly extend their working life. A second technique uses Parylene, a flexible
and biocompatible polymer. It allows improving the insertion of Parylene probe shanks by
formation of sharp tips and mechanical robustness enhancement without significantly
increasing its size.
This work was funded, in part, by the DARPA Hybrid Insect MEMS program under grant #
N66001-07-1-2006. Portions of this work were performed in the University of Michigan’s
Lurie Nanofabrication Facility.
55
Probing the associative interactions of biofilm extracellular polymers
Mahesh Ganesan1, Prannda Sharma2, John G. Younger2 and Michael J. Solomon1
1
2
Department of Chemical Engineering, University of Michigan, Ann Arbor, USA
Department of Emergency Medicine, University of Michigan, Ann Arbor, USA
Biofilms are surface adherent microbial aggregates enclosed within an extracellular (EPS)
matrix consisting of polysaccharides, proteins and eDNA. Bacterial biofilms have been
frequent causes of bloodstream related nosocomial infections. A commonly isolated
pathogen related to these infections is the bacteria Staphylococcus epidermidis. A vital
polymer in the S. epidermidis EPS is the polysaccharide intercellular adhesin (PIA). PIA is
crucial for the biofilm lifecycle in protecting the bacteria against blood shear forces and
antibiotics. However, knowledge of the synergistic role of PIA with extracellular proteins
and eDNA towards the microstructure of the biofilm matrix is still minimal. It is important to
study the interaction of PIA with these macromolecules to understand the construction of
the biofilm EPS and thus its role as a protective barrier. We view the biofilm as a
composite soft matter constituting of associating polymers. Using techniques based on
static and dynamic light scattering, and gel electrophoresis, we show that PIA forms
complexes with both DNA and proteins at concentrations relevant in situ. We also
establish that eDNA binds with a class of histone like DNA binding matrix proteins. This
implies that, all the major extracellular macromolecules exist in a state of intra and intermolecular associations that hold the EPS together. This knowledge, aids in the theoretical
re-construction of the extracellular hydrogel to study its responses towards a variety of
external stimuli. This would help in advancing our understanding on the rudimentary
protective role of the EPS in a biofilm and thus support better treatment methods.
We thank NIH and NSF for their financial support
56
Superior glenoid labrum pathomechanics
Eunjoo Hwang1,2, James Carpenter3, Richard Hughes3,4, Mark Palmer1,2
1
School of Kinesiology, University of Michigan
3
Department of Orthopaedic Surgery, University of Michigan
4
Department of Industrial and Operations Engineering, University of Michigan
2
The purpose was to understand the effects of superior humeral head translation and load
of the long head of biceps on the pathomechanics of the superior glenoid labrum by
predicting labral strain. Using MicroCT cadaver images, a finite element model of the
glenohumeral joint consisting of humerus, glenoid bone, cartilages, labrum and the long
head of biceps tendon was generated. A 50N compression and 0N, 22N, 55N, or 88N of
biceps tension were applied. The humeral head was superiorly translated from 0mm to
5mm at 1mm increments. The highest labral strain occurred at the interface with the
glenoid cartilage and bone beneath the origin of the biceps tendon. The maximum strain
is lower than the reported failure strain. Labral strain was significantly affected by biceps
tension, translation of the humeral head, and location along the superior labrum (P ≤
0.002). A linear regression model demonstrated that these parameters account for
approximately 74% of the strain predicted by the model. This supports the mechanistic
hypothesis that superior labral lesions may occur as a result of superior migration of the
humeral head. However, repetitive microtrauma rather than a single loading event may be
necessary to cause a mid-substance failure of the labrum.
This work was funded by an internal grant from the Valassis Endowed Research Fund
and the Department of Orthopaedic Surgery.
57
Decoding finger information from macaque motor cortex
Z. T. Irwin1, K. E. Schroeder1, D. E. Thompson1, A. J. Sachs6, P. G. Patil2,
Chestek1
3, 1
, C. A.
1
Department of Biomedical Engineering, University of Michigan,
Department of Neurosurgery, University of Michigan,
3
Department of Anesthesiology, University of Michigan,
4
Department of Electrical Engineering and Computer Science, University of Michigan,
5
Department of Neuroscience, University of Michigan,
6
Department of Neurosurgery, University of Ottawa
2
Intracortical brain-machine interfaces (BMIs) could one day restore normal function to
people with motor disabilities. In general, BMI research has focused on upper-arm
movement, as opposed to the fine motor skills needed to naturally grasp and manipulate
objects. In order to investigate the possibilities for decoding finger information from
neuronal activity, we implanted a rhesus macaque with two 96-channel Utah arrays in the
hand area of motor cortex. We recorded spikes while inducing somatosensory responses
by brushing the monkey’s fingertips. Using two seconds of neural data, we were able to
classify the brushed finger (out of 5) with 68.3% correct using a Naïve Bayes classifier on
the lateral array, compared to chance at 20%. When restricted to classification of thumb,
index, and little fingers, the same algorithm performed at 91.7% correct on the lateral
array, compared to chance at 33.3%.The monkey was also trained to hit virtual targets on
a computer screen by performing a four-finger bend (as measured by a bend sensor
attached to the index finger). A Naïve Bayes classifier decoded flexion versus extension
at 94.4% correct and movement versus rest at 100% correct for the lateral array (chance
at 50% for both).These results demonstrate that sufficient hand and finger information
may be present in motor cortex within the recording scope of a standard microelectrode
array to decode both motor behavior and sensory stimulus. These signals could be used
in the future to give motor BMIs the fine motor skills needed to produce dexterous hand
movements.
Funding: Taubman Medical Institute (P. G. Patil)
58
Pilot in-vivo study of chronically implanted Bi-directional Optrodes in rat
cerebral cortex
K. Kampasi1, B.L. McLaughlin2, G.E. Perlin2, J. LeBlanc2, C. Segura2, and
D. Kipke1
1
2
University Biomedical Engineering, University of Michigan, Ann Arbor, MI 48105 USA
Charles Stark Draper Laboratory, Cambridge, MA 02139 USA
Many recent advances in Neural Engineering are focusing on investigating the cause of
chronic failure of neural microelectrodes. This demands significant attention towards
understanding the impact of tissue immune response on long-term performance of neural
implants. Different tissue monitoring techniques like In-vivo Imaging and Tissue
Immunohistology, have been employed over past years to assess the dynamic nature of
tissue response. Unfortunately, these techniques are either retrospective, cumbersome or
suffer from sensitivity limitations at deeper brain areas. Bi-directional Optrodes propose a
novel approach to obtain real time histological assessment of neural tissue interface
failure at any cortical depth with constant sensitivity. This pilot study presents first in-vivo
analysis of Optrode’s spectroscopic measurement data and provides a critical analysis of
device performance. While a significant change in tissue optical properties was observed
post implantation period, more follow-up work is needed to better understand tissue
spectral characteristics and their direct dependence on tissue response.
This material is based upon the work supported by DARPA-RENET under award number
N66001-11-1-4191. Animal procedures were administered through the University of
Michigan Institutional Animal Care and Use Committee (IACUC) and the USAMRMC
Animal Care and Use Review office (ACURO) protocol 08227. The authors gratefully
acknowledge staff at ULAM Pathology Department (University of Michigan) and
Microscopy and Imaging Lab (University of Michigan) for their technical assistance. Any
opinions, findings, conclusions, or recommendations expressed in this publication are
those of the author(s) and do not necessarily reflect the views of DARPA.
59
Multicompartmental nanocarriers for Medical Applications
Asish C Misra1, Tae-Hong Park2, Srijanani Bhaskar3, Amanda Stacer4, Nicholas Clay2,
Randy P. Carney5, Francesco Stellacci5, Gary Luker4, Joerg Lahann1,2,3
1
3
Department of Macromolecular Science & Engineering, University of Michigan
4
Medical School, University of Michigan
5
Department of Materials Science & Engineering, École Polytechnique Fédérale de Lausanne
2
There is great potential for polymer micro- and nanocarriers in biomedical applications
such as tissue engineering or drug delivery. However, while such technologies are
hypothesized in some case to increase efficacy and potency of small molecule drugs this
goal has not been realized. There are many barriers to effective therapy caused by both
physiological and pathophysiological processes. Therefore, multifunctional carriers
capable of addressing multiple challenges are required for effective therapy.
Electrohydrodynamic co-jetting is a technique that may allow for the manufacturing of
such particles. Here we propose to develop several particle systems using the co-jetting
technique to address the challenge of developing carriers that can cope with these
barriers to effective therapy.
This work was funded in part by the Department of Defense.
60
Kinesin motion in the presence of obstacles on microtubules
Woochul Nam1, Bogdan I. Epurenau1
1
University Mechanical Engineering, University of Michigan
Kinesin molecules walk by moving their heads to binding site on microtubules. This walk
involves 16 nm advances of each kinesin head, realized by a conformational change in
the structure and by diffusion. Most previous studies focus on movement on microtubules
which have almost every binding site accessible. However, obstacles such as other
molecular motors or different proteins can occupy binding sites in front of a kinesin. This
study focuses on predicting the effects of obstacles on the dynamics of kinesin. First, a
novel quantitative model is developed to capture the diffusion of kinesin heads in the
absence of obstacles. To obtain probabilities of a head to bind at different neighboring
sites, this model considers the combined effects of the head geometry on the extension of
neck linkers, the interaction of the head and microtubules, and the dynamic behavior of
the coiled-coil structure of kinesin neck. The model reveals that the unwinding of the neck
and the binding of the head with tilted configuration are required to obtain the comparable
probability of side walk of kinesin as was measured in previous experiments. Then, the
motion of kinesin in the presence of obstacles is studied by using this model. The results
of previous experiments with obstacles suggest that the unbinding rate of kinesin
increases in the presence of interference with obstacles. Thus, this effect is also
incorporated in the model. The effects of the size and number of obstacles on the velocity
and run length of single kinesins are predicted.
61
Signal Magnitude, Reliability, and Validity of Regenerative Peripheral Nerve
Interface Device Function during Movement
Andrej Nedic1, D Ursu2, JD Moon3, CA Hassett3, RB Gillespie2, NB Langhals1,3, PS
Cederna1,3 MG Urbanchek3
1
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI
3
Department of Plastic Surgery, University of Michigan, Ann Arbor, MI
2
Regenerative Peripheral Nerve Interface (RPNI) devices successfully transduce
peripheral nerve action potentials to electrical signals suitable for prosthesis control.
Voltage changes are the controlling mechanism and can be observed during
electromyography (EMG). However, RPNI device signaling has not been characterized
during voluntary movements. Our purpose was to: a) characterize active RPNI signal
strength compared to background activity and b) define the reliability and validity of RPNI
signal function during purposeful movements. Three groups of rats were trained to walk
on a treadmill: Control (n=3), RPNI (n=3), 100% Denervated (n=3). Bipolar electrodes
were implanted onto the soleus muscles in each group. While walking on a treadmill, rats
were videographed and raw EMG signals were simultaneously recorded. Rectified EMG
was integrated (iEMG) and then normalized (NiEMG) to time for each gait phase: stance,
swing, and sit (nonactive). Fidelity of RPNI activity (stance) to background signaling (sit)
was 5.6 to 1, double the Control signal fidelity. Significant differences between stance and
swing NiEMG activity were confirmed for the Control and RPNI groups. As expected,
stance and swing EMG signals were not different for the Denervated group. Correlations
between iEMG and stance time for the Control (r=0.74) and RPNI (r=0.76) indicate good
RPNI signal reliability. These data comparing gait cycle to EMG activation accuracy
between Control, RPNI, and Denervated groups validated RPNI signaling as purposeful
peripheral nerve activity appropriate for meaningful control of prostheses (Chi Square;
p<0.05).
This work was sponsored by DARPA MTO through Grant N66001-11-C-4190.
62
Carbon fiber array insertion assisted by controlled application and removal of
polyethylene glycol.
Paras R. Patel1, Huanan Zhang2, Takashi D. Y. Kozai3, Nicholas A. Kotov2, Daryl R.
Kipke1, Cynthia A. Chestek1
1
3
Department of Bioengineering, University of Pittsburgh
2
In both human clinical applications and neuroscience studies, such as neural plasticity,
penetrating electrodes serve as a primary front end interface. In either field, the
successful implementation of neural probes that can function for long durations will
require recording arrays with high channel counts that simultaneously cause minimal
damage to the surrounding brain region and provide high quality neural signals. Recent
advances in this field have led to ultrasmall devices (<10µm) manufactured using carbon
fibers insulated with a highly conformal, yet thin, insulating layer of parylene (Kozai et al.,
2012). Owing to their small size, these probes have been shown, through histology, to
cause a minimal immune response and require no assistance in penetrating the brain at
short lengths. However, longer carbon fibers (>1mm), can be difficult to insert as they are
prone to bending or buckling which necessitates the use of forceps or other tools that can
in turn damage or break the probes. To this end we have developed a method to aid the
insertion of longer fibers by temporarily encapsulating them in a polyethylene glycol
(PEG) block, leaving only a small portion of the fiber exposed that can easily penetrate
the brain. By further dissolving away the PEG in a controlled manner, our group has
been able to reach insertion depths of 2.5mm. This method has been tested with a 16
channel carbon fiber array, yielding high quality recordings from distinct neuronal
populations.
This work was financially supported by an NIH Challenge Grant in Health and Science
Research from the National Institute of Neurological Disorders and Stroke (NINDS,
1RC1NS068396-0110) and the Center for Neural Communication Technology, a P41
Resource Center funded by the National Institute of Biomedical Imaging and
Bioengineering (NIBIB, P41 EB002030) and the National Institutes of Health (NIH). This
material is also based upon work partially supported by the Center for Solar and Thermal
Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department
of Energy, Office of Science, Office of Basic Energy Sciences (DE-SC0000957).
63
Orthogonal Decoration of Patchy Particles and Their Applicationsin Drug
Delivery
Sahar Rahmani1, Sampa Saha2, Tae-Hong Park2, Asish Misra1,3, Acacia Dishman4, and
Joerg Lahann1,2,5,6
1
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
3
Medical School, University of Michigan, Ann Arbor, MI 48109
4
Department of Biophysics, University of Michigan, Ann Arbor, MI 48109
5
Department of Material Science & Engineering, University of Michigan, Ann Arbor, MI 48109
6
Department of Macromolecular Science & Engineering, University of Michigan, Ann Arbor, MI 48109
2
Drug delivery is a rapidly growing field with numerous novel discoveries in the last few
years. These discoveries have tried to address some of the major challenges in this field,
which include the delivery of multiple drugs with distinct pharmacokinetics, sustained
release over a set period of time, the fabrication of nanoparticles, the inclusion of imaging
agents, and the surface modification of such particles for the incorporation of targeted and
stealth moieties. Through electrohydrodynamic co-jetting, our group has been able to
fabricate multi-compartmental, biodegradable particles that can be used for predictable,
controlled, and distinct delivery of multiple therapeutics.
In such cases, each
compartment can be loaded with a different drug and/or polymer with varying degradation
kinetics and release profiles. Additionally, each compartment can be selectively surface
modified to include targeting and stealth moieties, thereby increasing uptake to the
desired tissue and minimizing systemic side effects. Adjusting the size of the particles
can enhance this level of tissue specificity. Through the use of different solvents and
additives, we have been able to show the capability of fabricating particles that range in
size from nanoparticles (50-80 nm in diameter) to hundreds of microns (200-400 μm).
Tuning the size of the nanocarriers enables us to exploit different processes in the body,
for example the EPR (Enhanced Permeation and Retention) effect or size-dependent
phagocytosis by the RES (Reticulo-Endothelial System). Together, such characteristics
make our anisotropic carriers the optimal theranostic vehicles.
We would like to
acknowledgement our funding sources the American Cancer Institute, National Institute of
Health, and the Department of Defense.
64
Mobile, passive monitoring of breath sounds for management of asthma
Bharath Balaji Sathiyamoorthy1, Matt Christensen2, Evan Leitner2, Ben Levy3, Dr. Thomas
Sisson4, Dr. David T. Burke5
1
Medical School, University of Michigan
3
Department of Computer Science and Engineering, University of Michigan
4
Department of pulmonary and critical care, University of Michigan Hospital
5
Department of Genetics, University of Michigan
2
Asthma is an obstructive lung disease which is difficult to manage as the symptoms vary
frequently. According to AAFA, 44,000 Americans have an asthma attack every day and
these attacks can be mild, moderate or severe. It is essential to monitor the developments
and improvements in asthmatic care of the patients through the assessment of pulmonary
function on daily basis. We have designed and developed a home-centric asthma
monitoring system using wireless and smart mobile technologies at low cost with high
precision of data available both to the patient and the physician, engaging the patient
providing its sustainability. In this, we acquired the tracheal sound signals through a
specially designed hardware attached to the patient in the form of a band in the neck,
positioned at the suprasternal notch, where the signal-to-noise ratio was at its best. The
signals acquired were recorded via Bluetooth on the patient’s iOS device through the app
developed by us and they were visualized after decibel filtering in real-time. The recorded
signals would then be sent to cloud services with HIPPA compliance and these signals
would be analysed by LabVIEW software running continuously on a protected server.
LabVIEW processes all the requests from the patient using its in-built restful webservices
and its algorithms. The responses to the requests will be available on the cloud as well as
directly on our patient’s iOS app. The data available on the cloud can be accessed both
by the patient as well as the physician.
Acknowledgements: This project was funded by an educational grant from the Verizon
Foundation. Thanks goes out to the Department of Pulmonary and Critical care for
coordinating this interdisciplinary project with special thanks to Donna Johns. Dr. David
Burke and Dr. Thomas Sisson have been critical to the project's progress and they have
been excellent mentors.
65
Somatosensory responses in finger area of macaque motor cortex
KE Schroeder1, Z Irwin1, DE Thompson1, AJ Sachs6, PG Patil2,3,1, CA Chestek1,4,5
1
Department of Neurosurgery, University of Michigan
3
Department of Anesthesiology, University of Michigan
4
Department of Electrical Engineering and Computer Science, University of Michigan
5
Department of Neuroscience, University of Michigan
6
Department of Neurosurgery, University of Ottawa, ON, Canada
2
Recent work in intracortical Brain-Machine Interfaces (BMIs) has stressed the need for
sensory feedback to improve the performance of neuroprosthetics, leading to renewed
interest in the amount and nature of sensory information encoded in primary motor cortex
(M1). Previous single unit studies in monkeys showed M1 is responsive to tactile
stimulation, as well as passive and active movement of the limbs. Recent work in this
area has focused on proprioception, but we are interested in how somatosensation of the
hand and fingers is represented in M1. We recorded threshold crossings (<-4.5 RMS, 97
trials) from macaque M1 while gently brushing individual finger pads by hand at about 2
Hz. Surprisingly, the majority of channels showed a significant change in firing rate during
brushing when compared to a rest condition, and 48 of 96 channels showed significant
differences in firing rate between individual fingers (p<.05). Power spectral density
analysis on spike trains of exemplary trials showed a peak at about 2 Hz, the frequency of
stimulation, suggesting that some cells in M1 perform rate coding of somatosensory
inputs. We also created a map of tuning curves for all channels in the array based on the
physical location of electrodes. No somatotopic organization of finger preference was
obvious across cortex; however, for any given channel, preference did vary linearly
across the hand. Understanding M1 function with and without sensory inputs to the skin
(and potentially directly to the cortex via optogenetic stimulation) will inform better sensory
feedback to clinical prosthetic devices.
This work was supported by the Taubman Medical Institute and the University of Michigan
Department of Biomedical Engineering.
66
Interaction of atmospheric pressure DBDs with liquid covered tissues
Wei Tian1 and Mark Kushner2
1
2
Department. of Nuclear Engineering& Radiological Science, University of Michigan
Department of Electrical Engineering & Computer Science, University of Michigan
Atmospheric pressure dielectric barrier discharges in contact with liquid are of interest in
the context of tissue treatment in plasma medicine, from sterilization to wound healing,
because the tissues are often covered by a thin layer of liquid. This liquid is dominantly
water with dissolved gases and proteins. The liquid evaporates water into and
humidifying the adjacent gas. This liquid layer processes the plasma produced radicals
and ions prior to their reaching the tissue. In this paper, we report on a computational
investigation of the interaction of DBDs contacting a thin liquid layer covering tissue.
These simulations were performed using nonPDPSIM, a 2-dimensional model in which
Poisson’s equation, electron temperature equation and transport equations for charged
and neutral species are solved. The liquid layer, typically hundreds of microns thick, is
water containing dissolved. The discharges are operated at -15 kV with multiple pulses at
100 Hz followed by a 1 s afterglow. Reactive oxygen and nitrogen species (RONS)
produced in the gas phase intersect the water vapor saturated air above the liquid and
then solvate when reaching the liquid. The photoionization and photodissociation of
water by the plasma produced UV/VUV radiation play a significant role in the radical
production. In liquids without RH, O2- dominates the negative ions while hydronium
(H3O+) dominates the positive ions. The hydronium concentration determines the pH
value of the liquid.
[1] G. V. Buxton, C. L. Greenstock, W. P. Helman, and A. B. Ross, J. Phys. Chem. Ref.
Data. 17, 513 (1988).
* Work was supported by the DOE Office of Fusion Energy Science and the National
Science Foundation.
67
Quantifying nanomaterial partitioning into the cell membrane: A connection
to effective gene delivery?
Sriram Vaidyanathan 1, Bradford G.Orr 2, Mark M. Banaszak Holl 1,3
1
Department of Biomedical Engineering, University of Michigan, Ann Arbor 48109
Department of Physics, University of Michigan, Ann Arbor 48109
3
Department of Chemistry, University of Michigan, Ann Arbor 48109
2
The delivery of biomolecules such as nucleic acids and proteins to tissue for therapeutic
applications is an area of active research. Surfactants, cationic polymers (e.g
poly(ethyleneimine)) and cationic lipids (e.g DOTAP) are used in the formulation of such
therapeutics. We have investigated the effect of various surfactants, polymers, cationic
lipids and polymer-DNA polyplexes on the membrane conductivity of HEK293A and HeLa
cells using an automated whole cell patch clamp technique that can measure membrane
currents from 320 cells simultaneously. We have observed that the exposure of cells to
surfactants and polymers results in increased membrane permeability which is not
reversible for over 15 minutes. A 10 s exposure the fluorescent surfactant-like molecule
Octadecyl rhodamine B is sufficient to both increase membrane conductivity and
fluorescently tag the cell membrane. We have further used whole cell patch clamp to
determine the amount of surfactants partitioned in the cell membrane. This method is also
being used to quantify the amount of polymers and polyplexes complexes partitioned into
the membrane. It is known from literature that dyes used to stain the cell membrane are
distributed to the internal organelles. Future work will be focused on determining the role
of this membrane intercalated material in drug and gene delivery.
We thank BME departmental fellowship, Rackham research grant and NIH EB005028.
68
Live-Cell Subcellular Study of Force-Mediated Focal Adhesion
Morphogenesis Using Elastomeric Micropost Force Sensors
Shinuo Weng1, Yue Shao1, Weiqiang Chen1, and Jianping Fu1,2
1
2
Department of Mechanical Engineering , University
Department of Biomedical Engineering, University
External mechanical stretch/strain plays an important role in regulating cellular processes
including signal transduction, gene expression, growth, and survival. Mechanical stimuli
applied to the cells are predominantly detected at focal adhesions (FAs), the adhesion
structure containing structural and singling molecules. The co-localization of mechanical
and biochemical functions at FAs has suggested its functional role in transducing
mechanical forces on FAs into appropriate biochemical responses. However, the
correlation and cooperation between cytoskeleton (CSK) force and FAs in response to the
external stretch/strain is largely unclear due to the limitation of the current methods for
correlating CSK Force with FAs.
In this research, we used a novel cell stretching device that allows for real-time
measurement of mechanical stimuli and CSK forces, and constrains the recruitment of
FAs only on each force sensors. We applied 8% equibiaxial stretching to REF-52 cells
stably expressing YFP-Paxillin (gift from Dr. A. Bershadsky), and time-lapse fluorescent
images of YFP-Paxillin and micropost tops were taken before and after stretch. Images
were analyzed using customized Matlab code to determine CSK force and FAs on each
adhesive sites.
We observed a strong correlation between CSK force and FAs before and after stretch.
Acute increase of CSK force and FA recruitment within 1min after stretch was
independent of the initial CSK force, the initial FAs, and the position of the adhesion sites
inside the cell body. In the long term, spatiotemporal evolution of subcellular distribution
of CSK force and FAs were coordinated and compensated to reestablish the tensional
homeostasis.
69
Chemical Engineering:
Sustainable Energy
Session Chair: Anh Ta
70
Transition-Metal Carbide and Nitride Supercapacitor materials
Olabode T Ajenifujah1, Abdoulaye Djire1, Alice E. S. Sleightholme1, Paul Rasmussen1, 2,
Levi T Thompson1,2
1
Department of Chemical Engineering
Hydrogen Energy Technology Laboratory
University of Michigan, Ann Arbor, MI
2
Supercapacitors are energy-storage devices just like batteries, but they possess high
power density, long cycle life and moderate energy density. They fill the gap between
conventional capacitors and batteries in respect to their power and energy density. Their
commercial applications include use in hybrid commercial vehicles for load-leveling during
start-up, acceleration and regenerative braking, memory back-up in electronic device, and
uninterruptible power supplies. However, their moderate energy densities and high cost
limit their application in a number of areas. Carbon based materials are currently used
commercially as supercapacitor electroactive material, which are unsustainable and
costly. In our approach to these challenges, we explore the use of early transition-metal
carbide and nitride as the electroactive materials for these devices, which are cheap,
have high electronic conductivity, and can be synthesized with high surface area. This
poster describes the synthesis of novel low-cost, high-surface-area transition-metal
carbides and nitrides via temperature program reaction and their characterization as
electroactive materials. Among many early transition-carbide and nitride materials, we
currently focused our attention on Titanium Nitride(TiN), Niobium Nitride(NbN) and
Tungsten carbide(βWC1-X). The characterization of these materials were done physically
using X-ray diffraction(XRD) to determine the phase purity, Brunauer-Emmett-Teller(BET)
to determine the pore size distribution and the surface area of these materials. Then, we
characterized the materials using electrochemical techniques such as Open circuit
potential (OCP), to determine the voltage at which the current is zero (equilibrium
potential), cyclic voltammetry (CV); we applied voltage and get current output. Using the
CV curve, we determined the capacitance of the material, and understand the chemistry
and the two possible charge storage mechanisms (puesdocapacitance and double layer)
that may be occurring on these materials. Varying the scan rate of the CV experiment, we
were able to determine the contribution of each storage mechanism to the total
capacitance, which we found interesting and important toward understanding how these
materials store charges.
The authors acknowledge financial support from the Automotive Research Center, Army
Tank Command and Army Research Office.
71
Liquid Phase Carbon Dioxide Hydrogenation to Methanol over Molybdenum
Carbide Based Catalysts
Yuan Chen1, Levi T. Thompson1,2
1
2
Department of Chemical Engineering, University of Michigan, Ann Arbor
Hydrogen Energy Technology Laboratory, Energy Institute, University of Michigan, Ann Arbor
Carbon dioxide is generated during the combustion of fossil fuels and has been linked to
global climate change. CO2 could also be used as a source of carbon for the synthesis of
fuels and commodity chemicals. This project explores the possibility of hydrogenating
CO2 to methanol, an attractive first product, commonly used as a fuel or chemical
precursor.
This presentation will describe a low temperature route to produce methanol from CO 2 in
the liquid phase. A possible pathway to produce methanol under these conditions is via a
three-step tandem reaction: i) hydrogenation of CO2 to formic acid; ii) esterification of
formic acid to alkyl formate; iii) hydrogenolysis of alkyl formate to methanol. Effective
homogeneous catalysts exist for the first two steps; however, catalysts for the ratedetermining step, the third step, are needed. We observed that molybdenum carbide
(Mo2C) based materials are highly active for formate hydrogenolysis. The selectivity to
methanol was enhanced, when nanoscale particles of Cu and/or Pd, the species that are
active for methanol synthesis, were deposited onto high surface area Mo2C. The results
indicate the viability of employing metal supported Mo2C in the tandem conversion of CO2
to methanol.
This work is supported by the NSF under the CCI Center for Enabling New Technologies
through Catalysis (CENTC) Phase II Renewal, CHE-1205189.
72
Effects of Surface Oxygen on Charge Storage in TransitionMetal Carbide and Nitride Supercapacitor Materials
Abdoulaye Djire1, Olabode T Ajenifujah1, Alice E. S. Sleightholme1, Aniruddha Deb2, Paul
Rasmussen1,3, James Penner-Hahn2,
Levi T Thompson*1,3
1
Department of Chemistry
3
Hydrogen Energy Technology Laboratory
University of Michigan, Ann Arbor, MI 48109-2130
2
Supercapacitors are a relatively new type of energy-storage device that provide high
power densities, long cycle life and moderate energy densities. They fill the gap between
conventional capacitors and batteries. These devices can replace batteries in a number of
applications (e.g. electronic devices, military platforms) or can complement batteries in
hybrid systems to extend the lifetime of a battery pack. One of the emerging applications
of supercapacitors is in storing the intermittent energy available from renewable sources
including solar and wind. These devices could facilitate the introduction of renewable
electricity into the grid. The energy stored in supercapacitors is a function of the
capacitance and voltage. In order to increase the energy density of supercapacitors to
meet the current Department of Energy target of 15 Wh/kg, one would need to
significantly increase the capacitance and/or the operating voltage. The materials used
currently in commercial supercapacitors are based on carbon which is unsustainable and
costly. Over the past few years, significant emphasis has been placed on finding low-cost,
better performing materials for supercapacitor applications. This poster describes the use
of low-cost, high-surface-area transition-metal carbides and nitrides as electroactive
materials for supercapacitor applications. These materials possess very high
capacitances over a wide voltage window. Recently, we observed that pretreatment of
the surface significantly improved the capacitances of all of the materials from 43% for VN
to a 79% increase for Mo2C. The use of this pretreatment technique is of interest in the
design of higher-energy-density carbide and nitride-based supercapacitor electrode
materials.
The authors acknowledge financial support from the Automotive Research Center, Army
Tank Command and Army Research Office.
73
Electrolyte Strategies for Magnesium-Oxygen Batteries
James Saraidaridis1, Gulin Vardar2, Alice Sleightholme1, Don Siegel3,4, Charles Monroe1
1
Department of Materials Science, University of Michigan
3
4
2
Electric vehicles (EVs) employing state-of-the-art Li-ion battery packs are too expensive
and provide insufficient range to compete with internal combustion engine vehicles
(ICEVs) in mass markets. Although Li-ion technology will likely progress enough to allow
mass competition between EVs and ICEVs in the car sector, the chemistry lacks the
energy density to compete in larger vehicle sectors like small and large trucks.
Magnesium-oxygen chemistries have theoretical energy densities an order of magnitude
larger than Li-ion. Magnesium is readily abundant, inexpensive and stable during
electrochemical deposition or dissolution. However, developing a rechargeable Mg-O2
battery requires overcoming magnesium’s tendency to passivate and also preferentially
forming reversible discharge products. Herein we describe our progress in developing
Mg-O2 batteries.
Thank you to Denso International America for financially supporting this project, to Lucas
Griffith in the Monroe Laboratory, and Professor Bartlett and Emily Nelson from
Department of Chemistry at the University of Michigan for their synthetic facilities and
expertise.
74
Chemical Engineering:
Nanotechnology and
Microfabricated Systems
Session Chair: Anh Ta
75
Entropically Patchy Particles and their Emergent Valence
N Khalid Ahmed1, Greg van Anders1, Daphne Klotsa1, Ross Smith2, Michael Engel1 and
Sharon C. Glotzer1,2
1
2
Department of Chemical Engineering, University of Michigan, Ann Arbor
Department of Material Science and Engineering, University of Michigan, Ann Arbor
The self assembly of target crystal structures has been shown to be possible by
selectively introducing specific chemical patches and surface patterns on particles that
use enthalpy to align themselves anisotropically, resulting in the formation of a crystal
lattice. Recent computer simulations and experiments additionally have shown that
entropy can also be used to order hard anisotropic particles into complex crystals, liquid
crystals and even quasicrystals. The emergence of directional entropic forces (DEFs) has
been proposed for the ordering of non-spherical particles. We compute these forces for
particles of different shapes and show that they are at least several kT at the onset of
ordering, comparable to forces contributing to assembly in nano colloidal systems such as
traditional depletion interactions and van der Waals forces amongst others. Thus we
propose a new rubric for the design of nano and colloidal building blocks, by
systematically modifying particle shape and inducing emergent forces that drive
monodisperse systems of hard particles to self-assemble various target crystals
structures using entropy alone. We successfully self-assemble interesting crystal
structures in this manner. These design schemes are generalized into anisotropy
dimensions, similar to those exploited for enthalpically patchy particles.
This material is based upon work supported by, or in part by, the U.S. Army Research
Office under Grant Award No. W911NF-10-1-0518, the DOD/ASD(R&E) under Award No.
N00244-09-1-0062 and the James S. McDonnell Foundation 21st Century Science
Research Award for Studying Complex Systems.
76
Anomalous Dispersions of Hedgehog Particles
Joong Hwan Bahng1, Bongjun Yeom2, Yi Chun Wang1, Siu On Tung4, Nicholas Kotov1, 2, 3,
4, *
1
Department of Biomedical Engineering, University of Michigan, 3074 H.H. Dow Building, 2300 Hayward
Street, Ann Arbor, MI 48109, USA
2
Department of Chemical Engineering, University of Michigan, 3074 H.H. Dow Building, 2300 Hayward
Street, Ann Arbor, MI 48109, USA
3
Department of Material Science & Engineering, University of Michigan, 3074 H.H. Dow Building, 2300
Hayward Street, Ann Arbor, MI 48109, USA
4
Macromolecular Science and Engineering Program, University of Michigan, 3062C H.H. Dow Building,
2300 Hayward Street, Ann Arbor, MI 48109, USA
Aqueous dispersion of hydrophobic colloids is a procedural requirement in current
technological demands ranging from drug delivery to environmental remedy. Despite
undoubted success, the prevalence of chemical masking of the hydrophobic surfaces with
surfactants and amphiphilic polymers limit versatilities and untapped potential of particle
technologies due to toxicity and cost. In this letter, we demonstrate a novel route to
dispersion of hydrophobic colloids by topological modification to sculpture pronounced
nano-asperities at the interface. Methodological motivation stems from Cassie-Baxter
wetting and we hypothesized that air entrapment amidst the nano-asperities exert
significant repulsive potential that overrides decreased hydrophobic attractive potential
due to substantial reduction in the fractional hydrophobic surface. We have constructed
hydrophobic Hedgehog particles, reflective of its morphology, by either or both
hydrothermal sonochemcial growth of ZnO nano-spikes on a polystyrene spherical core.
Their hydrophobic equivalents are modeled by silanation of surface corrugations. We will
confirm our hypothesis by providing experimental observation of aqueous dispersion and
evidences of air-entrapment in the interstitial voids between nano-spikes. In addition, we
will demonstrate density manipulation to enable free aqueous suspensions facilitated by
the air-entrapment. Lastly, we will illuminate dispersion mechanism via evaluation of total
interaction potential between the hydrophobic Hedgehog particles.
Acknowledgement: This work is funded by ARO/MURI. We thank Doty Sorensen of MIL
for help with TEM and Jiyoung Kim for the help with CdTe synthesis
77
Towards Advanced Manufacturing of Hierarchical Carbon Nanotube
Structures
Mostafa Bedewy1, and A. John Hart1,2
1
2
Department of Mechanical Engineering, Massachusetts Institute of Technology
The unique properties of organized carbon nanotubes (CNTs) highlight their potential for
integration in high-performance structural composites, electrical interconnects, thermal
interfaces, and filtration membranes. However, materials and devices that are based on
hierarchical CNT ensembles require CNTs that are monodisperse, well aligned, and
densely packed. Hence, precise control of the morphology of as-grown CNT structures is
needed. In my Ph.D. research, I have created and validated tailored synthesis methods,
characterization techniques, and mathematical models that enable the production of
highly uniform CNT “forests”. Since a large number of CNTs grow simultaneously in a
typical chemical vapor deposition (CVD) process (typically 109 CNTs/cm2), understanding
the collective chemical and mechanical effects of growth is key. We have developed a
comprehensive non-destructive methodology for studying CNT population growth
dynamics by combining high-resolution spatial mapping of synchrotron X-ray scattering
and mass attenuation, with real-time forest height kinetics (laser-triangulation
measurements). By interrogating millions of CNTs concurrently, the CNT diameter
distribution, quantified alignment and density are obtained. Inferring mass kinetics of CNT
subpopulations, also reveals the size-dependent activation-deactivation competition
during the successive growth stages. Further, we demonstrate that mechanical coupling
among neighboring CNTs is not only responsible for the self-organization into the aligned
morphology, but is also an important limiting mechanism. Finally, we show that the
synergetic chemical coupling between CNT microstructures can be exploited to design
uniform CNT micropillar arrays.
We thank E. Meshot, and B. Farmer for collaborative contributions. This work was
funded, each in part, by DOE (DE-SC0004927), ONR (N000141010556), and NSF
(CMMI-0800213).
78
Patterned nanocomposite sensing skins for distributed strain sensing
Andrew Burton1, Jerome Lynch1,2
1
2
Department of Civil and Environmental Engineering, University of Michigan
Advanced performance requirements of modern structural systems are driving technology
development for monitoring structural performance. Paramount to these efforts are
multifunctional materials that produce an electrical response, or signal, when acted on by
a mechanical stimulus, such as strain. Carbon nanotube (CNT)-polymer thin films have
shown exceptional promise as one such material that can be nanoengineered into a
multifunctional skin for structural sensing. However, a layer-by-layer deposition process
used in creating these skins has previously limited the control and precision in sensing
skin fabrication. The scalability and utility of CNT-polymer sensing skins for sensing
distributed strain could be greatly enhanced with the ability to patterning precise sensor
geometries as this would allow for efficient spatial damage detection, increased CNT film
sensor scalability, and component-specific design of structural sensors. Here, processes
common to microelectromechanical systems (MEMS) are used to fabricate CNT-polymer
skins with various geometries and subsequently characterize the potential of such
patterning in the context of structural sensing. This is achieved as a carbon nanotubepolymer composite thin film is deposited on a glass substrate using a layer-by-layer
fabrication process then and patterned through an optical lithography lift-off process. The
pattern fabricated consists of five linear sensing elements of varying width, as linear
patterns are generally characteristic of strain sensors. The mechanical responses of
varying skin geometries are investigated by bonding sensors to structural test specimens
and then deforming these specimens in a load frame. Pattern fabrication quality is
characterized with optical and scanning electron microscopy.
79
Self-assembly of colloidal shape alloys
Eric S. Harper1, Ryan Marson1, Joshua Anderson2, Sharon Glotzer1,2
1
2
Department of Materials Science and Engineering, University of Michigan
Self-assembly of nanoparticles and colloids holds great promise to create useful new
materials. Nearly ubiquitous in nature, self-assembly is a powerful tool for organizing
matter, observed in everything from the formation of virus capsids and protein folding to
the bubbles on top of a glass of beer. Scientists and engineers in a wide variety of
disciplines hope to better understand how different particles self-assemble to facilitate the
engineering of desired assemblies of materials. While the use of DNA tethers, chemical
functionalization, and even magnets have been shown to effectively direct self-assembly,
the effect of particle shape on self-assembly has received surprisingly little attention.
Nature makes extensive use of shape-based complementary interactions, such as the
“lock and key” mechanism of enzymes and protein recognition at the surface of a cell. We
investigate a class of complementary “shape alloys” that can be used to stabilize desired
phases. These complementary particles fit together in a manner similar to that of puzzle
pieces. We begin with a two dimensional system of squares, which assemble into a
square lattice. When split into equal area rectangles and right isosceles triangles, the
rectangles assemble into an ordered lattice while the triangles do not. These were
compared with rectangles and triangles that have been “cut” so as to complement each
other. We see evidence that this shape complementarity promotes the desired assembly,
even in a system which otherwise would not assemble e.g. the right isosceles triangles.
This material is based upon work supported by the National Science Foundation Open
Data IGERT DGE 0903629, the U.S. Army Research Office under Grant Award No.
W911NF-10-1-0518, and the DOD/ASD(R&E) under Award No. N00244-09-1-0062.
80
Heat Dissipation in Atomic-Scale Junctions
Woochul Lee1, †, Kyeongtae Kim1, †, Wonho Jeong1, Linda Angela Zotti2, Fabian Pauly3,
Juan Carlos Cuevas2, Pramod Reddy1, 4
1
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center
(IFIMAC), Universidad Autónoma de Madrid, Madrid 28049, Spain
3
Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
4
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
†
These authors contributed equally to this work.
2
Heat dissipation is ubiquitous in nanoscale circuits and devices, yet it remains largely
unexplored. Here, we report heat dissipation studies in atomic and single-molecule
junctions using custom-fabricated scanning probes with integrated nanoscale
thermocouples. Heat dissipation in the electrodes of molecular junctions, whose
transmission characteristics are strongly dependent on energy, is asymmetric—that is,
unequal between electrodes—and also dependent on both the bias polarity and the
identity of the majority charge carriers (electrons versus holes). In contrast, atomic
junctions whose transmission characteristics show weak energy dependence do not
exhibit appreciable asymmetry. These studies unambiguously relate the electronic
transmission of nanoscale junctions to their heat dissipation properties proving a central
prediction of Landauer theory that has remained untested despite its relevance to a range
of nanoscale systems.
Reference
Woochul Lee, Kyeongtae Kim, Wonho Jeong, Linda Angela Zotti, Fabian Pauly, Juan
Carlos Cuevas, and Pramod Reddy, “Heat dissipation in atomic-scale junctions”, Nature,
498, 209 (2013)
81
Plasma-Assisted Nanoprinting for Manufacturing Large Arrays of MoS2Based Functional Devices
Hongsuk Nam1, Sungjin Wi1, Hossein Rokni1, Mikai Chen1, Greg Priessnitz1, Wei Lu1, and
Xiaogan Liang1
1
Molybdenum disulfide (MoS2), widely used as a lubricant material, recently attracts a
great deal of attention because of its attractive electronic, optoelectronic, and mechanical
properties. Especially, monolayer and few-layer MoS2 films have a large direct bandgap
that is suitable for semiconductor-related applications such as thin-film transistors,
chemical sensors, and light emission devices. Such atomically layered films also exhibit a
high mechanical flexibility and can be used for making flexible electronic products with
high performance. The current methods for producing few-layer MoS2 flakes include
scotch tape exfoliation, chemical vapor deposition, and laser-thinning process etc. These
methods still suffer from specific disadvantages and cannot create ordered, pristine MoS2
device arrays over large areas that are required for large-area applications. Therefore,
novel low-cost, upscalable nanofabrication methods are needed for addressing such
manufacturing-related issues and enabling the future scale-up applications of MoS2 in
electronics and optoelectronics. In this work, we systematically studied transfer-printing
approaches for creating orderly arranged MoS2 micro- and nanostructures over large
(cm2-scale) areas and demonstrated working field-effect transistors (FETs) made from
printed MoS2 flakes with excellent transistor performance. This research also identified
the key processing conditions affecting the printing uniformity over large areas,
morphologies of printed MoS2 structures, and ultimate transport properties of MoS2-based
FETs.
Our work demonstrated the printing of high-quality, well-defined MoS2 flakes over large
areas and working MoS2 FETs with excellent performance. The fundamental knowledge
achieved in this work could also be used for optimizing the printing-based manufacturing
routes for producing other atomically layered materials and functional devices.
Acknowledgement: NSF Grant #CMMI-1232883, NSF Grant #ECCS-1307740
82
Computational study of entropically driven crystal nucleation
Sam Nola1, Richmond Newman2, Sharon Glotzer1,2
1
2
Department of Macromolecular Engineering, University of Michigan
Through simulations and theory we are studying the self-assembly dynamics of hard
polyhedra systems that form rotator crystal phases in simulation. The transition path for
the crystallization of hard sphere systems is known to be a nucleation and growth process
resulting in FCC crystals. The polyhedra systems considered here also exhibit nucleation
and growth kinetics, but have significant differences in the observed homogeneous
nucleation rates and critical packing fractions. Formation of crystal nuclei in these
systems, including sphere systems, is a rare event: The formation of a stable nuclei
occurs on a timescale much smaller than the time between events. This makes sampling
and studying these events challenging. We employ several statistical and free energy
based methods to sample nucleation events in order to identify the critical nuclei and
understand transition paths.
83
Fabrication of a Wire Grid Polarizer by the Angled-evaporation
Method Showing an Increased Viewing Angle
Young Jae Shin1, Yi-Kuei Wu2, Kyu-Tae Lee2, Jong G. Ok3, and L. Jay Guo1,2,3
1
Department of Macromolecular Sciences and Engineering, University of Michigan
3
2
A wire grid polarizer (WGP) was fabricated by using a simplified approach with a
combination of nanoimprint lithography (NIL) and angled metal deposition. The period of
the imprinted polymer nanograting used in this study was 180 nm. The WGP was formed
by 2 consecutive angled aluminum evaporation processes essentially halving the period
for the aluminum (Al) nanograting. The fabricated WGP showed good optical properties
for polarized light. More importantly, because of the slight reduction of the period of the
nanograting as compared with our previous results, the viewing angle, which is one of the
most important characters in display equipment, was extended greatly. Encapsulation of
the WGP using poly(methyl methacrylate) was conducted for practical application of the
WGP. The thickness of the coating was controlled to be less than 1 µm to prevent the
degradation of the optical properties of the WGP.
84
Nanograting–Mediated Growth of Bismuth Selenide Topological Insulator
Nanoribbons
Sungjin Wi1, Eljon Elezi1, Amy Liu1, Vishva Ray2, Kai Sun3, and Xiaogan Liang *1
1
Department of Mechanical Engineering,
Lurie Nanofabrication Facility, Department of Electrical Engineering and Computer Science,
3
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109
2
Topological Insulators (TIs) are a group of emerging materials that exhibit unusual
electronic properties. The ballistic transport of carriers via these conductive surface states
can be topologically protected against the scattering by nonmagnetic defects. Therefore,
TIs could be implemented to make low-dissipation electronic channels for applications in
spintronics, thermoelectrics, and magnetoelectronics. However, additional research is
needed to significantly improve the yield of sub-100 nm wide TNRs and also obtain a high
uniformity of the ribbon widths.
In this work, we present a nanostructure-mediated growth process specifically for
producing bismuth selenide (Bi2Se3) TNRs with a high yield. In this process, TI
nanostructures are grown on nanograting templates by using NP-catalyzed VLS
mechanism. In comparison with the growth processes on flat and randomly rough
substrates, such a nanograting-mediated growth process produces TNRs with a higher
yield (~15,000/mm2), a narrower average ribbon width (wavg < 60 nm), and a higher
uniformity in width (σ < 30 nm); effectively suppresses the formation of other unwanted
morphologies; and also results in the axial growth of nanoribbons along specific in-plane
directions relative to pre-structured gratings. The TEM characterization shows that the
produced nanoribbons are single crystals with atomically smooth edges. Finally,
Aharonov–Borm (AB) oscillations in the magnetoresistance were observed and clearly
demonstrated the coherent transport of electrons through topological surface states of
Bi2Se3 nanoribbons.
This work could serve as an important foundation for nanomanufacturing topological
insulator nanoribbons with controllable feature size, large-area uniformity and ordering
suitable for future applications in low-dissipation nanoelectronics and magnetoelectronic
sensors.
85
Chiral Transmission to Self-Assembling Nanostructures from Circularly
Polarized Light
Jihyeon Yeom1, Bongjun Yeom2, Sung Jin Chang3, Wei-Shun Chang4, Gongpu Zhao5,
Peijun Zhang5, Stephan Link4, Nicholas A. Kotov1,2*
1
Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109,
USA
2
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
3
Division of Material Sciences, Korea Basic Science Institute, Daejeon, 305-333, Republic of Korea,
4
Department of Electrical and Computer Engineering, Rice University, Houston TX 77005, USA
5
University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
*To whom correspondence should be addressed. E-mail: [email protected] (N.A.K.)
Regarding life’s distinctive selectivity of chiral molecular species, and various chirooptical
properties of chiral materials, synthesizing chiral nanostructures have attracted strong
scientific interest. However, control over enantiomeric preference for artificial inorganic
nanomaterials has limited to templating method using biological compounds. Here we
show that circularly polarized light can drive the self-assembly of cadmium telluride
nanoparticles (CdTe NPs) into nanoribbons controlling helical directions by transcription
of chiral information from the light to NPs. Different helical directions of laser induce
different light adsorption of CdTe NPs which lead to greater reactivity of a selective
chirality. This simple method for chiral nanoribbons can open the door to understanding
life’s homochirality and chiroptical devices.
Key words: chirality, self-assembly, circularly polarized light, nanoribbon, chirooptical
86
Civil Engineering:
Infrastructure
Session Chair: Ran Gao
87
Capturing Spatial and Temporal Variations in Non-Uniform Thermal Loads
on Structural Elements
Paul A. Beata1, Dr. Ann E. Jeffers1
1
In a typical analysis of a structure exposed to fire, the scenario is idealized as a
compartment fire model and the heating is represented by a uniform gas temperature.
However, local fires present a more complicated thermal load that cannot be fully
captured by a compartment fire model. The proposed method for handling non-uniform
thermal loads is a finite-element approach based on energy equivalence. First, a
computational fluid dynamics (CFD) model representing the fire scenario was used to
measure the thermal loads as they vary across the surface of a structural element. Using
these measurements in conjunction with a temporal sub-cycling algorithm that was
developed in a previous study, the thermal loads on the surface of the element were
specified as input to the finite element heat transfer analysis. The non-uniform surface
fluxes from the CFD simulation are represented in the finite element heat transfer model
using numerical techniques such as time-average subcycling and spatial homogenization
to provide an energy-equivalent boundary condition in the heat transfer model. Results
from a preliminary study involving a plate exposed to a local fire show that the new
analysis technique is efficient beyond the CFD simulation phase; the heat transfer
analysis is accurate without adding substantial simulation time.
88
Performance Evaluation of Existing Highway Bridges under Combined
Hazard of Seismic and Corrosion
Xiaohu Fan1 and Jason McCormick1
1
Given the increasing awareness of seismic hazard in the Central and Eastern United
States (CEUS), the seismic performance of the area’s highway bridge infrastructure is
gaining more concern in both public and academic communities. Particularly, a majority of
the bridges, constructed based on outdated design codes with little seismic consideration,
are approaching their design service life, which have sustained corrosion in steel
components such as steel bearings to various levels. According to the 2013 ASCE report
card, many bridges of the CEUS will need major rehabilitation due to deficiency and
deterioration. Thus, it is vital to identify the structural components in these bridges
requiring the most urgent retrofit and upgrade. In this poster, one of the critical
components, steel bearings that are representative of those found in the CEUS and have
been experimentally investigated in a previous study regarding their seismic response at
various levels of corrosion, is emphasized in the performance evaluation of an older
highway bridge under moderate seismic loading. Constitutive models that are correlated
with corrosion levels are established for the first time for a suite of steel bearings
considered in the mentioned experimental study. A full bridge model is also created for a
typical four span continuous highway bridge considering a variety of nonlinearities. This
study will fully explore the combined effect of corrosion and seismic on the performance
of older highway bridges regarding bearing displacements, pier wall plasticity
development, and deck-abutment impact to assist the search for sustainable and viable
retrofit strategies.
89
Structural reliability evaluation under fire
Qianru Guo1 and Ann E. Jeffers1
1
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor
The current fire resistance design methodology in the United States is based on
prescriptive requirements for fire resistance rating of isolated structural elements without
considering the structural system performance and the actual fire scenario. In order to
change this situation and also to give engineers more flexibility on fire resistance design,
the professional society is trying to move from the prescriptive design to the performancebased design. As an important component of performance-based design, an efficient
reliability-based design methodology is urgently needed to ensure adequate reliability in
the face of uncertainty.
This poster shows a framework that is able to simulate structural response in fire and to
evaluate the failure probability of structure subjected to fire. The compartment fire model,
the thermal heat transfer model, and the structural model are coupled together to predict
the actual gas temperatures, structural element temperatures, and structural responses
during a fire. Both analytical reliability methods, namely the First-Order Reliability Method
(FORM) and Second-Order Reliability Method (SORM), and Monte Carlo Simulation
(MCS) are applied to quantify the structural reliability of the multi-physical and highly
nonlinear system. An application involving a protected steel column exposed to natural
fire is presented in this poster. The FORM is recommended for the rapid estimation of the
reliability of structures threatened by fire based on its comparison with MCS on the
accuracy and the efficiency.
90
Damage Detection in Metallic Elements using a Point-based Thermal
Measurement Strategy
Nephi R. Johnson1, Jerome P. Lynch1, 2, Ann E. Jeffers1
1
2
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI
Early detection of damage in metallic structures (e.g., bridges, ships, aircraft) is crucial to
the success of structural health monitoring (SHM). Often times, visual inspection or single
point surface mounted sensors are not enough to detect some forms of damage with
adequate time to perform preventative maintenance on the structure. Non-destructive
methods using thermal imaging have been developed to monitor the state of a structure in
two and three dimensions. These techniques use an infrared (IR) camera to track the
heat conduction through the material, which has been heated by either a laser or a lamp.
While these methods have proven to be effective techniques in the lab or during shortterm field deployments, they are expensive and generally not feasible for long-term
permanent applications. This poster presents a method of thermography-based damage
detection that employs an economic sensor setup that is feasible for permanent
deployment in operational structures. The setup includes resistive heating elements and
an array of IC temperature sensors mounted to the boundary of 2 aluminum plate
specimens (1 undamaged, 1 damaged). As the heat is conducted from the resistor
through the metal, sensors measure the time variance in temperature rise at the sensor
locations. This data can then be used in an inverse manner using a high-fidelity finite
element model (FEM) to solve for imperfections in the metal that cause delays in heat
conduction. Correlations between the finite element and the temperature sensor system
are analyzed as well as damage detection results of the inverse problem solver.
The authors would like to gratefully acknowledge the generous support offered by the
U.S. Department of Commerce, National Institute of Standards and Technology (NIST)
Technology Innovation Program (TIP) under Cooperative Agreement Number
70NANB9H9008. Additional support was provided by the National Science Foundation
through Grant Number 0846256.
91
Development of ECC Slurry for Levee Cut-off Wall Applications
Lena M. Soler Ayoroa1, Victor C. Li1
1
Earthen levees are used as the primary flood protection system in many U.S. river cities,
and their structural stability is maintained by the use of slurry cut-off walls. However, due
to the slurry material’s brittle nature (generally a mixture of cement, soil and bentonite)
and lack of steel reinforcement, its performance in seismically active regions is often
questioned. Engineered Cementitious Composites (ECC) are ultra-ductile cement based
composites, which have been successfully employed in a variety of structures for
enhancing durability and structural performance under seismic loads. The present study
focuses on evaluating various ECC mixtures for their applicability in cut-off walls in terms
of cost, greenness, workability, strength, and ductility. Although ECC has proven to be
exceedingly better than other cementitious based materials due to its ductile ability, the
high cost of the polyvinyl alcohol (PVA) fibers typically used in ECC mixtures prohibits the
use of these composites for slurry wall applications. Hence for this study, high-tenacity
polypropeleyne (HTPP) fibers will be evaluated as a possible replacement for PVA fibers
since they reduce both cost and environmental impact of the mixtures. Furthermore,
greenness and ductility were further improved by increasing the fly ash content. Results
show that mixtures with high fly ash (HFA) content and HTPP fibers meet slurry
requirements in terms of cost, workability, permeability, and compressive performance. In
addition, HFA-ECC with HTPP fibers exceed the current slurry cut-off walls in terms of
mechanical properties such as tensile strength and strain, and other properties such as
permeability which makes ECC slurry a viable and desirable replacement for current cutoff walls.
Acknowledgements
Support from the University of Michigan is gratefully acknowledged. The project is funded
by the National Science Foundation (NSF). The authors would also like to recognize the
support given by Lafarge (cement), Headwaters (fly ash), WR Grace (HRWRA), Brasit
(HTPP fibers), and Poraver® (Poraver®).
92
Impact of Dissolved Oxygen and Microbial Populations on Pharmaceutical
Biotransformations in Wastewater
Lauren B. Stadler1, Lijuan Su2, Diana S. Aga2, and Nancy G. Love1
1
2
Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY
Thousands of pharmaceuticals are excreted by humans in intact and metabolized forms,
reaching wastewater treatment plants (WWTPs) before entering our waterways. WWTPs
represent the entry point for the environmental proliferation of pharmaceuticals. Yet they
are also the last line of defense against this chemical pollution. Our limited understanding
of pharmaceutical transformation pathways prevents us from aligning the design and
operation of WWTPs to reduce pharmaceutical exposure and associated risk in receiving
environments In addition, as the industry moves toward implementing technologies in the
name of sustainability, such as low dissolved oxygen (DO) treatment, it must recognize
the consequences that these systems have on other treatment objectives that impact the
environment and public health.
The objective of this study is to evaluate how low DO treatment affects the profile of
pharmaceuticals in effluents and to understand which microbial populations are
responsible for pharmaceutical biotransformation. This is achieved by measuring
biotransformation rates of six commonly used pharmaceuticals in batch experiments
using cultures of heterotrophs and ammonia oxidizers enriched under different DO
conditions. Pharmaceutical quantification is performed using liquid chromatography and
mass spectrometry. Initial results show that certain pharmaceuticals such as 17αethinylestradiol (EE2), a drug commonly used for birth control, is biotransformed much
faster by ammonia oxidizers than heterotrophs and occurs faster in high DO than low DO
conditions. These results will further our understanding of the fate of pharmaceuticals
during wastewater treatment will improve our ability to design WWTPs to achieve multiple
goals (i.e. reduce energy demands and achieve pharmaceutical inactivation).
93
Time-Dependent Behavior of Sand
Zhijie Wang1
1
Department of Civil and Environmental Engineering, Uniersity of Michigan
Time-dependent increase in small strain stiffness of sand under sustained load has been
reported by some researchers, but the mechanisms causing this behavior are not well
understood. The hypothesis in this research considers delayed fracturing of micromorphological features on grain surfaces at inter-granular contacts as a key mechanism
contributing to time-dependent behavior of sand at the macroscopic scale. Experimental
work has been carried out at both the microscopic (a single contact) and the macroscopic
(sand specimen) scales. Time-dependent behavior of a single contact was investigated
using custom-designed device, which allows one to measure a time-dependent response
of a contact once it had been loaded. A modified consolidometer was then used to
investigate the response of a large assembly of grains (sand specimen) to sustained load.
The inaccuracies of measurements of the radial stress in the consolidometer were
overcome through a fluid-calibration process. Both dry and water-saturated specimens
have been tested. Scanning electron microscopy (SEM) and atomic force microscopy
(AFM) were used to characterize the surface of the grains where the key process
contributing to aging is believed to take place. The results were found to be very
sensitive to temperature and vibrations, and the experiments have been performed in an
environmental chamber with constant temperature of 20C (and constant relative humidity
of 20%). Preliminary results will be presented. These results have been found consistent
with the proposed hypothesis.
94
Incorporation of Innovative Materials in Seismic Hollow Structural Section
Connections
Dan Wei1, Matthew Fadden2, Jason McCormick, Ph.D.1
1
2
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI,48105
Department of Civil Engineering, University of Louisiana at Lafayette, Lafayette, LA, 70504
Hollow structural sections (HSS) are currently underutilized in steel moment frame
system. In order to evaluate cyclic behavior and design details of HSS to HSS connection
in seismic moment frame systems, cyclic quasi-static tests of four different detailing
connections are conducted. The behavior of reinforced connections can limit the location
of inelasticity to beam and panel zone region which is more desirable than unreinforced
ones. However, based on these test results, the behavior during cyclic loading can be
affected by local buckling and the damage associated with the inelastic behavior. The
voids of structural members provide an often underutilized location for the application of
non-traditional materials. One means of mitigating local buckling and providing
supplemental energy dissipation capacity is through the use of non-traditional materials
for passive control applications. The high damping properties polymer foams, metal
foams and rubber materials provide a unique means of adding energy dissipation
capacity to the plastic hinge region of a member with minimal increase in weight. To
determine the properties and energy dissipation capacity of the selected fill materials,
future work will focus on cyclic material characterization studies under loadings and
loading rates expected during an earthquake. The results are used to evaluate the ability
of the passive control systems to control the behavior of structures during a seismic
event.
95
Ductile spray-applied fire-resistive material for enhanced fire safety of steel
structures
Qian Zhang1, Victor Li1
1
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor
Spray-applied fire-resistive material (SFRM) is one of the most widely used passive fire
protection material in North America. However, SFRM is inherently brittle and tends to
dislodge or delaminate under extreme loading conditions (earthquakes or impacts) and
even under normal service conditions such as wind induced building movement. Such
loss of fire protection material puts the steel structure in great danger under fire loading,
especially under multi hazards (post-earthquake or post-impact fires). As an alternative to
conventional brittle cementitious material, engineered cementitious composites (ECC) is a
family of high performance fiber reinforced cementitious composites. ECC typically
exhibits strain hardening behavior with very high tensile ductility (3-5%) under static and
high rate loading. In this paper, a new spray-applied fire-resistive material that combines
the desirable thermal insulation property, ease of construction (facilitated by sprayability),
lightweightness of SFRM and the enhanced ductility of ECC is developed as an
alternative material to current SFRM. The newly developed spray-applied fire-resistive
ECC (SFR-ECC) exhibits density as low as 550 kg/m 3 yet with tensile strength up to
1MPa and tensile strain capacity greater than 2%, significantly higher than those of
conventional SFRM with tensile strength of less than 0.1MPa and no inelastic tensile
strain. The thermal conductivity of SFR-ECC is measured in accordance with ASTM
E2584 and is shown to be comparable to conventional SFRM within the same density
range. SFR-ECC with enhanced mechanical performance is expected to improve the
overall fire safety of steel structure under both service and extreme loads.
The authors wish to express their gratitude and sincere appreciation to 3M, Lafarge, WR
Grace, Dayton and Brasilit for material supply for this research project.
96
Frost heave and thaw settlement of ground surface above an oil pipeline
Yao Zhang1
1
Freezing and Thawing of frost-susceptible soils often causes substantial damage to
infrastructure. A pipeline system could be vulnerable to such issue since the medium
transported may have below-freezing temperature and the surrounding soil is above
freezing, or vice-versa. Such examples may include chilled gas pipelines going through
normal temperature soils or warm oil pipelines buried in permafrost region. Accounting for
frost heave and thaw settlement is important in transportation infrastructure, and of
particular concern are the regions in soils where thermal front (freezing and thawing) may
propagate into the soil at different rates, leading to differential heave or settlement.
A Thermal-hydro-mechanical (THM) model will be introduced including basic partial
differential equations (PDEs) for conservation of energy, conservation of mass and
mechanical equilibrium, to describe the multi-physical feature of soils under freezing and
thawing. The constitutive relationship in the model is elastic-plastic and on the basis of
critical state framework with consideration of freezing effect. Frost heave and thaw
settlement induced by a chilled gas pipeline as well as seasonal temperature change will
be simulated using this model, and the potential damage to the pipeline will be analyzed.
This work was funded, in part, by the Army Research Office, grant No. W911NF-08-10376.
97
Computer Science
Session Chairs: Cheng Zhang and Parinaz Naghizadeh Ardabili
98
Robust Image Denoising with Multi-Column Deep Neural Networks
Forest Agostinelli1, Honglak Lee1, Michael Anderson1
1
Department of Computer Science, University of Michigan
Stacked sparse denoising auto-encoders (SSDAs) have recently been shown to be
successful at removing noise from corrupted images. However, like most denoising
techniques, the SSDA is not robust to variation in noise types beyond what it has seen
during training. We present the multi-column stacked sparse denoising autoencoder, a
novel technique of combining multiple SSDAs into a multi-column SSDA (MC-SSDA) by
combining the outputs of each SSDA. We eliminate the need to determine the type of
noise, let alone its statistics, at test time. We show that good denoising performance can
be achieved with a single system on a variety of different noise types, including ones not
seen in the training set. Additionally, we experimentally demonstrate the efficacy of MCSSDA denoising by achieving MNIST digit error rates on denoised images at close to that
of the uncorrupted images.
99
The Moo and Cement Shoes: A Real-World Application of Sensor Swarms
Miran Alhaideri1, Michael Rushanan2, Denis Foo Kune1, Kevin Fu1
1
2
Department of Computer Science and Engineering, Johns Hopkins University
Passively-powered computational RFIDs (CRFID) have dispelled the assumption that
only simple computations are possible under harvested RF-power. This lass of RFIDs
feature reprogrammable microcontrollers, electronic sensors and actuators, and
nonvolatile memory. Most importantly, the sensors and actuators provide the foundation
for a not-too-distant paradigm shift toward the integration of cyber-physical worlds.
A classical approach in civil engineering is to address the structural integrity of an
infrastructure retroactively. This process often requires human intervention, introducing
non-negligible error, and is restricted to a limited set of data points subject to
interpolation. In an attempt to gauge the gap between research and industry, we
immersed devices built on our research platform in a real-world application. We
embedded 19 epoxied CRFIDs, Moo Platform 1.1 [4], inside the concrete walls of a
residential basement. Each Moo was placed inside a concrete-filled cinderblock at parallel
diagonals, along three distinct heights. Afterwards, we immediately began sampling from
the Moo's external temperature and accelerometer sensors. The temperature sensor was
used to capture the concrete curing process, while the three-dimensional accelerometer
was used to measure structural changes in the position of the wall over time.
This work was supported in part by the TerraSwarm Research Center and the Center for
Future Architectures Research (C-FAR).
100
X-ray: Automating Root-cause Diagnosis of Performance Anomalies in
Production Software
Mona Attariyan1, Michael Chow2, Jason Flinn2
1
2
Google Inc.
Department of Computer Science & Engineering, University of Michigan
Troubleshooting the performance of production software is challenging. Most existing
tools, such as profiling, tracing, and logging systems, reveal what events occurred during
performance anomalies. However, users of such tools must infer why these events
occurred; e.g., that their execution was due to a root cause such as a specific input
request or configuration setting. Such inference often requires source code and detailed
application knowledge that is beyond system administrators and end users.
We introduce performance summarization, a technique for automatically diagnosing the
root causes of performance problems. Performance summarization instruments binaries
as applications execute. It first attributes performance costs to each basic block. It then
uses dynamic information flow tracking to estimate the likelihood that a block was
executed due to each potential root cause. Finally, it summarizes the overall cost of each
potential root cause by summing the per-block cost multiplied by the cause-specific
likelihood over all basic blocks. Performance summarization can also be performed
differentially to explain performance differences between two similar activities. X-ray is a
tool that implements performance summarization. Our results show that X-ray accurately
diagnoses 17 performance issues in Apache, lighttpd, Postfix, and PostgreSQL, while
adding 2.3% average runtime overhead.
101
Low-Power, Real-Time Gaze Tracking
Russ Bielawski1, Prabal Dutta1
1
It has long been said that they eye is the window to the soul. However, until now, this allimportant visual context information has been absent from the personal computing
infrastructure. With advances in low-power CMOS imaging technology and wireless
radios, continuous, low-power eye tracking is an idea whose time has come. The
SensEye wireless gaze detection prototype represents the first step in augmenting the
computational ecosystem with real-time gaze information. This visual context has board
applications in transportation and medicine as well as in more long-term ideas such as
augmented reality. SensEye is a low-power, lightweight system for tracking a person’s
gaze fixation in real time. Our wireless eyeglasses weigh only slightly more than a heavy
pair of spectacles and are capable of six hours of continuous operation.
This work is supported by the National Science Foundation, NSF Grant 1239341, in
collaboration with Deepak Ganesan, Benjamin Marlin, Marco Duarte, Christopher
Salthouse, Addison Mayberry, Boyan Lu, Pan Hu, Hamid Dadkhahi, Venkatesh Murthy,
Pengyu Zhang and Jeremy Gummeson at the University of Massachusetts.
102
When to attack? Android UI state inference as an attack building block
Qi Alfred Chen1, Zhiyun Qian2, Zhuoqing Morley Mao1
1
2
University of Michigan, Ann Arbor
NEC Labs America, Inc.
Recently many studies have pointed out that on mobile platforms such as Android, a
malicious app running in the background can hijack TCP connections, infer web pages
and keystrokes, etc., endangering security and privacy of mobile users. However, these
attacks usually only work during certain operation of the victim app, e.g. keystroke
inference for user input related operations. Thus, not knowing when to attack makes such
attacks infeasible in practice (due to success rate, overhead and stealthiness concerns).
In this work, we solve this problem by introducing User Interface (UI) state inference as a
building block for these attacks: an unprivileged background app with minimal privileges is
able to peek into another application's UI and track its states closely in real time, thus
allowing attacker to choose the best attack moment. The underlying problem is that the
design and implementation of Android UI framework has interesting and unexpected
interactions with publicly accessible side channels. Since there is no obvious vulnerability
in either design or implementation, it is non-trivial to eliminate the problem. Our evaluation
shows that the accuracy of UI state inference is 80-90% for the first candidate UI state on
popular apps such as WebMD, Chase Bank, etc., and over 95% for top three candidates.
Furthermore, through case studies, we have designed and implemented fully several
interesting new attacks based on UI state inference, including capturing sensitive pictures
(e.g. checks for banking app) at the background, and monitoring private information of the
user (e.g., medical conditions in health app).
103
Senbazuru: A Prototype Spreadsheet Database Management System
Zhe Chen1, Michael Cafarella1, Jun Chen1, Daniel Prevo1, Junfeng Zhuang1
1
Department of Computer Science & Engineering, University of Michigan
Spreadsheets have become a critical data management tool, but they lack explicit
relational metadata, making it difficult to join or integrate data across multiple
spreadsheets. Because spreadsheet data are widely available on a huge range of topics,
a tool that allows easy spreadsheet integration would be hugely beneficial for a variety of
users.
We demonstrate that Senbazuru, a prototype spreadsheet database management system
(SSDBMS), is able to extract relational information from spreadsheets. By doing so, it
opens up opportunities for integration among spreadsheets and with other relational
sources. Senbazuru allows users to search for relevant spreadsheets in a large corpus,
probabilistically constructs a relational version of the data, and offers several relational
operations over the resulting extracted data (including joins to other spreadsheet data).
Our demonstration is available on two clients: a JavaScript-rich Web site and a touch
interface on the iPad. During the demo, Senbazuru will allow VLDB participants to search
spreadsheets, extract relational data from them, and apply relational operators such as
select and join.
104
Anception: Hybrid Virtualization for Smartphone Applications
Earlence Fernandes1, Alexander Crowell1, Ajit Aluri1, Atul Prakash1
1
Department of Computer Science and Engineering, University of Michigan, Ann Arbor
The improved performance and functionality of smartphones in recent years has
transformed them into mobile extensions of desktops and laptops. But with this new
versatility also comes the security threats that plague other computer systems. Methods
for allowing trusted and untrusted desktop applications to securely share the same
environment have been well researched, producing approaches that use system call
redirection and virtualization, among other methods. However, that research often does
not carry over neatly to the mobile environment, where resource constraints are a limiting
factor and the user interface paradigm is fundamentally different. This paper proposes a
new security mechanism called hybrid virtualization that combines elements of traditional
full-system virtualization with selective system call redirection.
Hybrid Virtualization provides high-performance isolation while largely preserving the
original user interface in terms of receiving notifications from apps in multiple trust
domains and being able to interact with them with low latency. We describe our
implementation of \emph{Anception}, which realizes hybrid virtualization in the Android
environment with only minimal modifications to the Linux kernel. Our security evaluation
based on reported vulnerabilities from the past 4 years shows that Anception provides
comparable security to full-system virtualization. Anception incurs only a 1.2% overhead
on the SunSpider application benchmark and up to 3.88% overhead on 2D and 3D
graphics benchmarks.
105
Emotion Classification via Utterance-Level Dynamics: A Pattern-Based
Approach to Characterizing Affective Expressions
Yelin Kim1 and Emily Mower Provost1
1
Departament of Electrical Engineering and Computer Science, University of Michigan Ann Arbor
Human emotion changes continuously and sequentially. This results in dynamics intrinsic
to affective communication. One of the goals of automatic emotion recognition research
is to computationally represent and analyze these dynamic patterns. In this work, we
focus on the global utterance-level dynamics. We are motivated by the hypothesis that
global dynamics have emotion-specific variations that can be used to differentiate
between emotion classes. Consequently, classification systems that focus on these
patterns will be able to make accurate emotional assessments. We quantitatively
represent emotion flow within an utterance by estimating short-time affective
characteristics. We compare time-series estimates of these characteristics using Dynamic
Time Warping, a time-series similarity measure. We demonstrate that this similarity can
effectively recognize the affective label of the utterance. The similarity-based pattern
modeling outperforms both a feature-based baseline and static modeling. It also provides
insight into typical high-level patterns of emotion. We visualize these dynamic patterns
and the similarities between the patterns to gain insight into the nature of emotion
expression.
106
Putting the IT in QuIT Smoking
Noah Klugman1, Prabal Dutta1
1 Departament of Electrical Engineering and Computer Science, University of Michigan
Cigarette smoking is responsible for millions of deaths, despite valiant individual efforts to
quit. In response to these failures, new programs have been proposed that would offer
incentives to smokers to quit. Unfortunately, the programs suffer from dependence on
unreliable, self-reported data to determine a participant’s compliance [Abroms11]. We
claim that information technology can offer a better compliance mechanism. Because
cigarette smoke contains carbon monoxide (CO), the absence of CO from a program
participant’s breath offers reliable evidence of compliance with an intervention program.
We propose a CO monitor that pairs with a smartphone to measure an individual’s breath
CO concentration. Our CO monitor communicates wirelessly with a smartphone using the
Bluetooth Low Energy protocol. An IOS app stores the data locally, displays CO
concentration to the user, and delivers the data to the cloud for analysis and compliance
verification. Our prototype offers comparable accuracy to existing monitors while greatly
improving usability and user satisfaction.
[Abroms11] Abroms et al., iPhone apps for smoking cessation: A content analysis. 2011.
107
Using N-gram and Word
Identification
Network
Features
for Native
Language
Shibamouli Lahiri1, Rada Mihalcea2
1
2
Computer Science and Engineering, University of North Texas
Computer Science and Engineering, University of Michigan
Native Language Identification is an interesting and challenging problem in natural
language processing, where the goal is to identify an author's native language (L1) from
his/her writings in a second language (L2), usually English. The task is conventionally
framed as a multi-class classification problem, where training documents are in L2, and
the class labels are different authors' L1s. In our study, we experimented with two sets of
features - a traditional feature set comprising the raw frequency, normalized frequency,
and binary presence/absence indicator of the most frequent character, word, and part-ofspeech n-grams (n = 1, 2, 3), and a new feature set comprising centrality measures of
most frequent words in the documents' word co-occurrence networks. Among traditional
features, we observed that word unigrams with punctuations were the best performers on
the training dataset released by the Educational Testing Service (ETS), under ten-fold
cross-validation. On the same training corpus, our new feature set involving centrality
measures on word networks showed promising performance. Degree and neighborhood
size (of order one) were the best-performing centrality measures, whereas function words
like ''a'', ''however'', and ''the'' were found to be among the most discriminatory words. We
performed an extensive array of experiments with several different classifiers, and
Support Vector Machines (SVM) emerged as the best classifier under most settings.
108
Emotion Recognition from Spontaneous Speech using Hidden Markov
Models with Deep Belief Networks
Duc Le1, Emily Mower Provost1
Research in emotion recognition seeks to develop insights into the temporal properties of
emotion. However, automatic emotion recognition from spontaneous speech is
challenging due to non-ideal recording conditions and highly ambiguous ground truth
labels. Further, emotion recognition systems typically work with noisy high-dimensional
data, rendering it difficult to find representative features and train an effective classifier.
We tackle this problem by using Deep Belief Networks, which can model complex and
non-linear high-level relationships between low-level features. We propose and evaluate
a suite of hybrid classifiers based on Hidden Markov Models and Deep Belief Networks.
We achieve state-of-the-art results on FAU Aibo, a benchmark dataset in emotion
recognition. Our work provides insights into important similarities and differences between
speech and emotion.
109
AMC: Verifying User Interface Properties for Vehicular Applications
Kyungmin Lee1, Jason Flinn1, T.J. Giuli2, Brian Noble1, Christopher Peplin2
1
2
Ford Motor Company
Vehicular environments require continuous awareness of the road ahead. It is critical that
mobile applications used in such environments (e.g., GPS route planners and locationbased search) do not distract drivers from the primary task of operating the vehicle.
Fortunately, a large body of research on vehicular interfaces provides best practices that
mobile application developers can follow. However, when we studied the most popular
vehicular applications in the Android marketplace, no application followed these
guidelines. In fact, vehicular applications were not substantially better at meeting best
practice guidelines than non-vehicular applications.
To remedy this problem, we have developed a tool called AMC that uses model checking
to automatically explore the graphical user interface (GUI) of Android applications and
detect violations of vehicular design guidelines. AMC is designed to give developers
early feedback on their application GUI and reduce the amount of time required by a
human expert to assess an application's suitability for vehicular usage. We have
evaluated AMC by comparing the violations that it reports with those reported by an
industry expert for 12 applications. AMC generated a definitive assessment for 85\% of
the guidelines checked; for these cases, it had no false positives and a false negative rate
of under 2%. For the remaining 15% of cases, AMC reduced the number of application
screens that required manual verification by 95%.
110
Robot Navigation in Dynamic and Uncertain Environments via Hierarchical
and Integrated Motion Planning and Control
Jong Jin Park1 and Benjamin Kuipers2
1
2
The ability to navigate intelligently and effectively in dynamic and uncertain environments
is crucial for any autonomous mobile agent to survive, to interact with the world, and to
achieve its goals. For this, we have proposed the model predictive equilibrium point
control (MPEPC) framework, applicable for navigation to a target pose in space [2], and
also for person pacing and following for human-robot companionship [3]. The algorithm
builds upon a smooth control law which enables the robot to reach any pose in space
gracefully [1], which shapes and defines a continuous space of realizable actions for the
mobile robot. The controller puts useful constrains on some of the degrees of freedom of
the robot so that the resulting trajectories of the robot are smooth and comfortable, and
also provide a low-dimensional parametric representation of the remaining degrees of
freedom, which in turn defines the search space of the trajectory planner. The trajectory
planner lets the robot navigate by selecting and executing the best local trajectory at each
planning cycle, where each trajectory hypothesis is tested for the expected utility to find
the locally optimal solution, fully considering probability of collision, cost of action and
progress toward achieving the agent's goal, either a fixed pose in space or a moving
target about a person. With our low-dimensional representation of the trajectory space
and integrated planning and control architecture, the typical optimization cycle takes
<200ms on a physical robot.
Acknowledgement:
Research of the Intelligent Robotics lab is supported in part by grants from the National
Science Foundation (CPS-0931474 and IIS-1111494), and from the TEMA-Toyota
Technical Center.
References:
[1] J. Park and B. Kuipers, “A Smooth Control Law for Graceful Motion of Differential Wheeled Mobile Robots in 2D
Environment”, Proceedings of IEEE International Conference on Robotics and Automation (ICRA), 2011.
[2] J. Park, C. Johnson and B. Kuipers, "Robot Navigation with Model Predictive Equilibrium Point Control",
Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2012
[3] J. Park and B. Kuipers, "Autonomous Person Pacing and Following with Model Predictive Equilibrium Point
Control", Proceedings of IEEE International Conference on Robotics and Automation (ICRA), 2013
111
A multimodal dataset for deception detection
Veronica Perez-Rosas1, Rada Mihalcea2, Mihai Burzo2.
1
2
Computer Science and Engineering. University of North Texas
Computer Science and Engineering. University of Michigan
The automatic identification of deceptive behavior in human responses is a desirable
capability of applications in human-computer interaction. Most of the previous work
presented in this area has focused on individually analyzing specific components of
human deceptive responses, such as spoken or written language, visual behaviors, or
physiological responses. More recently, in an effort to improve the understanding of
deceit, multimodal approaches have been explored. In these studies, one important
requirement is the availability of deception datasets, which to date are scarce. Motivated
by the lack of multimodal resources for the task of deception detection, we introduce a
new multimodal dataset. We elicit subject’s deceptive responses by using three deceit
scenarios in which participants express deceptive and truthful statements about different
topics. The data is collected in a multimodal setting where we acquire video, audio,
thermal, and physiological recordings of the participants. After presenting a detailed
description of the experimental protocol and the data acquisition process, we present a
set of descriptive statistics. Furthermore, we discuss directions for future research that
might benefit from using this data set.
112
TARDIS: Secure Time Keeping For Embedded Devices
Without Clocks
Amir Rahmati1, Mastooreh Salajegheh2, Dan Holcomb3, Jacob Sorber4,
Wayne P. Burleson2, Kevin Fu1
1
CS, University of Massachusetts Amherst
3
Electrical Engineering and Computer Science, University of California Berkeley
4
CS, Dartmouth Collage
2
Lack of a locally trustworthy clock makes security protocols challenging to implement on
batteryless embedded devices such as contact smartcards, contactless smartcards, and
RFID tags. A device that knows how much time has elapsed between queries from an
untrusted reader could better protect against attacks that depend on the existence of a
rate-unlimited encryption oracle. The TARDIS (Time and Remanence Decay in SRAM)
helps locally maintain a sense of time elapsed without power and without special-purpose
hardware. The TARDIS software computes the expiration state of a timer by analyzing the
decay of existing on-chip SRAM. The TARDIS enables coarse-grained, hourglass-like
timers such that cryptographic software can more deliberately decide how to throttle its
response rate. Our experiments demonstrate that the TARDIS can measure time ranging
from seconds to several hours depending on hardware parameters. Key challenges to
implementing a practical TARDIS include compensating for temperature and handling
variation across hardware. Our contributions are (1) the algorithmic building blocks for
computing elapsed time from SRAM decay; (2) characterizing TARDIS behavior under
different temperatures, capacitors, SRAM sizes, and chips; and (3) proof-of-concept
implementations that use the TARDIS to enable privacy-preserving RFID tags, to deter
double swiping of contactless credit cards, and to increase the difficulty of brute-force
attacks against e-passports.113113113
113
AppProfiler: A Flexible Method of Exposing Privacy-Related Behavior in
Android Applications to End Users
Sanae Rosen1, Zhiyun Qian1, Z. Morley Mao1
1
Although Android's permission system is intended to allow users to make informed
decisions about their privacy, it is often ineffective at conveying meaningful, useful
information on how a user's privacy might be impacted by using an application. We
present an alternate approach to providing users the knowledge needed to make
informed decisions about the applications they install. First, we create a knowledge base
of mappings between API calls and fine-grained privacy-related behaviors. We then use
this knowledge base to produce, through static analysis, high-level behavior profiles of
application behavior. We have analyzed almost 80,000 applications to date and have
made the resulting behavior profiles available both through an Android application and
online. Nearly 1500 users have used this application to date. Based on 2782 pieces of
application-specific feedback, we analyze users' opinions about how applications affect
their privacy and demonstrate that these profiles have had a substantial impact on their
understanding of those applications. We also show the benefit of these profiles in
understanding large-scale trends in how applications behave and the implications for user
privacy.
114
Organizational Design Principles and Techniques for Decision-Theoretic
Agents
Jason Sleight1, Edmund Durfee1
1
Recent research has shown how an organization can influence a decision-theoretic agent
by replacing one or more of its model components (transition/reward functions,
action/state spaces, etc.), and how each of these influences impacts the agent's decisionmaking performance. This work delves more precisely into exactly which parts of an
agent's model should be organizationally influenced, and asserts a broader principle for
delineating what aspects of an agent's behavior an organization should be sanctioned to
influence. We present a formal framework for specifying factored organizational
influences and incorporating them into agents' decision models, and empirically
demonstrate that organizational specifications based on our proposed principle
outperform the alternatives. We further describe an algorithm for automating the
organizational-design process that is inspired by this principle, and demonstrate
empirically that its organizational designs are both intuitively sensible and also find and
exploit domain structure that our hand-generated designs miss.
This work was supported by NSF grant IIS-0964512.
115
Electrical Engineering:
Applied Electromagnetics and
Plasma Science
116
Investigating the Potential of Miniature Electrodynamic Tethers to Enhance
Capabilities of Ultra-small Sensor Spacecrafts
Iverson C. Bell, III1
1
Department of Electrical Engineering, University of Michigan
The success of nanospacecraft (1–10 kg) and the evolution of the millimeter-scale
wireless sensor network concept have generated interest in small, sub-kilogram scale,
“smartphone”-sized spacecraft, either as stand-alone satellites or as elements in a
maneuverable fleet. These satellites are in the picosatellite (100 g–1 kg) and
femtosatellite (<100 g) mass categories. The need for propellantless propulsion is
evident: not only would formation flying of a fleet require the maneuverability of each
satellite, but flat pico- and femtosat wafers also can have an inherently short orbital life in
low Earth orbit (LEO) due to atmospheric drag, ranging from a few weeks to a few hours.
In this paper, we present the results of trade studies that investigate the feasibility of
using short (few meters), semi-rigid electrodynamic tethers (EDTs) for pico- and femtosat
propulsion. The results reveal that an insulated tether, only a few meters long, can
provide milligram-to-gram-level satellites with complete drag cancellation and even the
ability to change orbit. Our goal in this paper is also to improve our understanding of the
spacecraft’s interaction with the ionosphere by conducting ground-based plasma
experiments that capture critical characteristics of the LEO environment. By further
investigating plasma contactors in the system concept, we aim to better understand the
feasibility of the dual ultra-small satellite–EDT propulsion concept.
The authors acknowledgement support from AFOSR grant FA9550-09-1-0646, the
National Science Foundation Graduate Student Research Fellowship under Grant No.
DGE 1256260, and the Michigan Space Grant Consortium.
117
Ultra-Wide-Band Slot Antenna with Uni-axial Dielectric Superstrate
Hatim Bukhari1 and Kamal Sarabandi1
1
The Radiation Laboratory, Electrical Engineering and Computer Science Department, University of
Michigan, Ann Arbor, MI
Slot antennas constitute one of the most popular planar low-profile antennas which are
easy to fabricate, have high radiation efficiencies, are easy to integrate with the RF
frontend, and are low-cost. Their radiation pattern and bandwidth are similar to dipole
antennas and thus number of modifications are required to achieve ultra-wideband
performance and for radar applications to make the antenna radiation pattern directional.
In this paper, a new technique in designing a slot antenna with 60% fractional bandwidth
and directional radiation pattern is presented. In order to further improve the bandwidth,
reduce the size, and achieve directional radiation pattern, the use of a stepped index
superstrates with tapered dielectric constants, from dense to sparse, is proposed. The
electromagnetic waves behavior can be controlled by adding different materials with
different permittivities which allows better matching of the waves in the superstrate to the
surrounding medium. Adding superstrate with equivalent dielectric constant of periodic
media create a dielectric resonance mode near to the other resonance of the slot antenna
itself. Proper feeding can also create a fictitious short along the slot antenna. The
superstrate has the effect of reducing the slot dimension for given resonance and
therefore, the slot radiates effectively toward the superstrate and reduces the backward
radiation. The stepped index allows a better matching to free-space. The width and length
of the slot antenna and the thicknesses of each periodic layer of the superstrate are
optimized to achieve the required operating bandwidth.
118
Tailoring the phase and power flow of electromagnetic fields
Gurkan Gok1, Anthony Grbic1
1
A method for arbitrarily controlling the phase progression and power flow of
electromagnetic fields within a region of space is introduced. Specifically, we describe
how a 2D inhomogeneous, anisotropic medium can be designed that supports desired
spatial distributions of the wave vector and Poynting vector direction. Plane-wave
relations in anisotropic media are used in conjunction with an impedance matching
process to find the required material parameters. The developed formulation allows one
to independently tailor the phase and amplitude of a field profile. In the presentation, the
use of the proposed method in transformation of the cylindrical source radiation into
desired amplitude and phase profiles are shown. In addition, design of a wide-band
antenna beam-former generating a collimated beam from a cylindrical source is outlined.
Implementation of the beam-former using tensor transmission-line metamaterials and
simulation results are presented.
This work was supported by a NSF Faculty Early Career Development Award (ECCS0747623) and the Presidential Early Career Award for Scientists and Engineers
(PECASE) grant (FA9550-09-1-0696).
119
Dielectric Characterization of Thin Materials at 240 GHz
Amr Ibrahim1, Kamal Sarabandi2
The increasing demand on higher data rates in modern communication systems has
pushed the operating carrier frequencies to the millimeter wave (MMW) regime. Also
MMW and sub-MMW frequencies are being considered for small short range radars
envisioned for autonomous robotic applications.
In order to develop a robust
communication or radar system, the surrounding multi-path channel and the radar clutter
environment needs to be accurately modeled. For doing so, the electromagnetic
properties (complex permittivity, magnetic permeability, electric conductivity…) of different
materials found in the physical transmission medium are required.
The characterization of different thin materials at millimeter-wave frequency, 240 GHz, is
presented in this abstract. This includes vegetation leaves as well as different types of
fabrics. The complex permittivity retrieval algorithm is based on fitting the measured
transmission coefficient at different incident angles to the corresponding analytical
transmission coefficient of a simple dielectric slab. The extracted dielectric permittivity
values for the fabrics are compared with the corresponding values measured at low
microwave frequency (~1 GHz), using a standard material analyzer, where they are found
to be nearly the same. For the leaf measurements, it is found that a simple dielectric
mixing formula can be used to predict the value of dielectric permittivity.
120
Micromachined Frequency Beam Scanning Patch Array Antenna at J-Band
Armin Jam1, Mehrnoosh Vahidpour1, Jack East1, and Kamal Sarabandi1
1
This paper presents the design, fabrication and characterization of a frequency beam
scanning array antenna operating from 230 GHz to 245 GHz. The array is designed using
hollow rectangular waveguides with slot cuts placed on the H-plane of the waveguide
wall. The slots in turn excite a linear patch array above it. The progressive phase shift
between the slots is facilitated by meandered waveguide lines supporting TE10 mode. By
changing the frequency, the propagation constant of the waveguide changes, which in
turn will change the excitation phase of each slot and hence the beam is steered. This
one-dimensional array forms a narrow beam width in the plane of slots while generating a
wide beam in a plane perpendicular to that. In order to confine the beam in the elevation
direction, the antenna aperture is widened by using slot-coupled patch arrays. This twodimensional structure provides a two-dimensional confined beam. The patches are
positioned on top of the slots separated by a dielectric substrate. The center patch is fed
by the slot on the bottom layer of the substrate, while the rest are series-fed through the
center one.
One method to fabricate the antenna is the micromachining technique where the
waveguide trenches are etched in silicon and then covered with gold. Next the slots are
fabricated on a wafer and bonded to the other wafer to form the one-dimensional array.
Finally, the patches are fabricated on a membrane which is then attached to the one
dimensional array to form the complete antenna.
This project is funded by Army Research Lab (ARL).The authors would like to thank M.
Moallem and the staff at the Lurie Nanofabrication Facility (LNF), University of Michigan,
Ann Arbor for their thoughtful comments and suggestions.
121
An Optically Transparent Two-Element Wideband Array Antenna with
Unidirectional and Tilted Beam for Ground Vehicles
M. Kashanianfard1, K. Sarabandi1
1 Departament of Electrical Engineering and Computer Science Department, University of Michigan
Wireless communication between vehicles is affected by some of the adverse effects of
the communication channel such as multi-path fading, attenuation, non-line-of-sight, etc.
To mitigate some of these effects, operation at lower frequencies (UHF and VHF) is often
preferred for ad hoc communication networks. One drawback of operating at these
frequencies for mobile platforms is the size of the antenna. In addition, for situations
where different channels or space diversity are needed, the close proximity of many such
antennas results in co-site interference and other undesired issues. Embedding the
antenna in the windows of the vehicle eliminates the mentioned problems but imposes
additional requirements such as optical transparency and unidirectionality (radiation
inside the cabin is unwanted). To compensate for the tilt angle of the windshield, a two
element phased array can be used.
In this paper, a planar two element array antenna is designed to be embedded in the
described window. A rigorous numerical optimization of the design parameters is
performed and transmission line based matching circuits are designed to enhance the
impedance matching and produce the required phase shift between the array elements. A
number of balun designs are used and their effect on the radiation pattern and input
impedance of the antenna is studied. The optical transparency of the antenna is improved
by replacing the bow-tie antenna elements with a wire mesh of the same shape.
122
Large Signal Modeling of Intrinsically Switchable Ferroelectric FBARs and Its
Application to Linearity Analysis of BST FBAR Filters
Seungku Lee1, Victor Lee1, Seyit Sis1, and Amir Mortazawi1
This presentation presents the large signal modeling procedure of intrinsically switchable
ferroelectric thin film bulk acoustic resonators (FBARs) as well as its application to FBAR
filter linearity analysis. There has been a growing interest in ferroelectric FBARs due to
their electric field dependent permittivity and electric field induced piezoelectricity.
Ferroelectric barium strontium titanate (BaxSr(1-x)TiO3, BST) FBARs are intrinsically
switchable, namely they have resonances that switch on with the application of a dc bias
voltage. In this presentation, the large signal performance and nonlinear behavior of
ferroelectric BST FBARs are investigated. Measurement results show that the device
nonlinearity can be reduced by applying higher dc bias voltages. Moreover, a large signal
model that accurately describes the dc bias voltage as well as RF power dependent
performance of BST FBARs is developed. Large signal simulation results obtained from
this model at different bias voltages and RF power levels show good agreement with the
measurement results. Then, BST FBAR filters composed of two series FBARs and one
shunt FBAR are designed, fabricated, and measured. IIP3 of more than 26 dBm for a 1.6GHz filter with insertion loss of 4.1 dB is obtained. A linearity improvement technique for
BST FBAR filters is also demonstrated through simulation using a nonlinear BST FBAR
model.
123
Beam Shaping with Metamaterial Huygens’ Surfaces
Carl Pfeiffer1, Anthony Grbic1
1
Metamaterials have demonstrated the ability to manipulate electromagnetic waves with
unprecedented control. However, their notable thickness often leads to significant loss
and fabrication challenges. This has motivated the development of metasurfaces: the two
dimensional analog of metamaterials. Here, a new type of metasurface, referred to as a
metamaterial Huygens’ surface, is introduced. Metamaterial Huygens’ surfaces are
capable of arbitrarily manipulating electromagnetic wavefronts without reflection. These
surfaces will likely find a wide range of beam shaping applications including: singlesurface lenses, polarization controlling devices, stealth technologies, and perfect
absorbers.
A proof of concept Huygens’ surface was designed that refracts a normally incident plane
wave to an angle of 45o from normal. The electric response is realized with loaded strips
and the magnetic response is realized with split-ring-resonators. This structure was
fabricated by stacking 58 identically patterned printed-circuit-boards, and measured with a
near field scanning system. The half-powered bandwidth and peak efficiency were
measured to be 24.2% and 86% respectively, which closely agreed with simulations.
This work was supported by a US Air Force grant (FA4600-06-D003) and the National
Science Foundation Materials Research Science and Engineering Center program DMR
1120923 (Center for Photonics and Multiscale Nanomaterials at the University of
Michigan).
124
Simulation of Micro-Plasma Based Pressure Sensors*
J. C. Wang1, Z. Xiong1, C. Eun1, X. Luo1, Y. Gianchandani1, and M. J. Kushner1
1 Departament of Electrical Engineering and Computer Science Department, University of Michigan, Ann
Arbor, USA
Pressure sensors having dimensions of a few mm are used for automotive, biomedical
and industrial applications based on piezoresistive and capacitive methods. Recently, a
microplasma-based sensor has been developed for pressure measurements in harsh
environments. In these sensors, a microplasma is sustained between an anode and two
competing cathodes in a sealed chamber with a diaphragm mounted on one cathode.
The external pressure deforms the diaphragm which then redistributes the current
collected by the cathodes. Pressure is then measured based on the relative difference in
currents.
In this presentation, we will discuss the properties of microplasma-based pressure
sensors using results from a two-dimensional simulation. The model, nonPDPSIM,
solves Poisson’s equation and transport equations for charge species and electron
energy equation for electron temperature. Radiation transport is addressed using a
Green’s function approach. The microplasma is sustained between an anode (A) biased
with hundreds of volts and two grounded cathodes (K 1, K2) in a sealed chamber filled with
1 atm of Ar. The reference cathode (K1) is located adjacent to the anode (A) while the
sensing cathode (K2) is mounted on the diaphragm separated by a gap of 10 μm. We find
that a highly conductive plasma is first generated between AK 2, and then repetitive
ionization waves propagate along AK1. The current on K1 and K2 varies with interelectrode spacing (AK2) which is changed by deflection of the diaphragm due to the
external pressure. The current distribution can also be optimized by adjusting the
impedance connected to electrodes.
*Work was supported by the Advanced Energy Consortium.
125
Super-miniaturized Borehole Antenna Design and Radio-wave Estimation of
Sub-surface Hydraulic Fractures at MF Band
Jiangfeng Wu1, Kamal Sarabandi1
1
In this paper we present a medium frequency (MF) band helical dipole antenna for
borehole application. The proposed antenna is loaded with a ferrite-bundle and is
optimized to achieve an ultra-compact size to fit within a volume of λ0/1337 × λ0/1337 ×
λ0/80 while maintaining a relatively high efficiency of about 20%. To feed the antenna
from the center using an external source, the effect of a metallic cylinder placed in the
center is also examined. The feeding network is designed to match the antenna input
impedance with the frequency tunability. Based on the proposed antenna, a radio-wave
technique for detecting and measuring the extent of hydraulic fractures in subsurface rock
layers using MF band is developed. Compared with conventional high frequency mapping
system, the penetrating distance has increased by one to two orders of magnitude due to
the low propagation loss at MF band frequencies. The method is based on transmission
measurements among elements of vertical synthetic arrays in the boreholes. The array
patterns are optimized to minimize the direct-link from the transmitter antenna to receiver
antenna. Post-processing maps the conductivity contrast in the target area with a good
resolution.
126
Integrated Circuits VLSI,
MEMS, & Microsystems
127
HEMT-Based Read-out of a AlGaN/GaN Thickness-mode Resonators
Azadeh Ansari1, Mina Rais-Zadeh1
1
Departament of Electrical Engineering and Computer Science, University of Michigan
AlGaN/GaN high electron mobility transistors (HEMTs) have been widely used in broadband power amplifiers in base station applications due to high electron mobility in the twodimensional electron gas (2DEG) channel and high saturation velocity. The high electron
concentration of nitride HEMTs is induced by piezoelectric and spontaneous polarization
of the strained AlGaN layer. Thus, Nitride HEMTs are very sensitive to mechanical
pressure, which changes the piezoelectric polarization-induced surface and interface
charges. In this work, the HEMT drain current is modulated with the strain induced in the
2DEG channel through a Schottky back gate contact. This work combines the benefits of
piezoelectric actuation with HEMT-based sensing.
Authors would like to thank staff at LNF for their help with fabrication and NSF for funding
the project.
128
Fused Silica Platform for Inertial MEMS Devices
Zongliang Cao1, Yi Yuan1, Guohong He1, Rebecca L. Peterson1, and Khalil Najafi1
1
This project aims to create an extremely compact platform for MEMS based inertial
sensors. Such compact systems are ideally suited to mobile applications as well as
navigational guidance where space is limited. In particular, we aim to build a high
performance timing and inertial measurement unit (TIMU) with size comparable to an
apple seed. Our TIMU consists of three single-axis accelerometers and three single-axis
gyroscopes and a clock. Miniaturization is achieved via vertical integration of the devices
and packing within the same framework. Fused silica, a non-traditional bulk material for
MEMS, serves as both the structural material for the devices as well as packaging. This
was enabled by newly developed silica etching capabilities here at the University of
Michigan. It is expected that superior resonant devices of higher Q-factor can be built on
fused silica due to its much lower material losses, enhancing device performance. In
addition, its thermally and electrically isolating nature makes it ideal for packaging and
low-power ovenization while also allowing for lower noise feedthroughs. To date, we have
demonstrated seven working devices in a package smaller than 13 mm 3 with 60 electrical
feedthroughs. Challenges that remain are improving device sensitivity, vacuum
packaging, and reducing mechanical coupling between devices.
This work is supported by DARPA TIMU award #N66001-11-C-4170. Portions of this work
were performed in the University of Michigan’s Lurie Nanofabrication Facility
129
A 5.9-μm Pixel-Pitch, 336×256 Pixels 3-D Camera with Background Light
Suppression over 100klx
Jihyun Cho1, Seokjun Park1, Euisik Yoon1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
Real-time depth profiling or imaging now became an essential part in human-computer
interaction (HCI) and security systems. In these applications, the three dimensional (3-D)
profile provides secure and stable information compared to conventional 2-D intensity
images because 3-D information is independent of illumination conditions. Time-of-flight
(TOF) is the most popular solution to realize the depth sensors due to its fast acquisition
speed and sufficient resolution of centimeter range. However, TOF measurement relies
on active illumination; thus, any extraneous light disturbs the measurement. For example,
the sensor cannot produce any useful information when saturated by strong background
light (BGL). For this reason, most TOF sensors are only used for indoor applications. To
overcome this problem, some TOF sensors implemented the BGL suppression function
by employing dedicated pixel-level circuitry at the cost of large pixel size, which makes it
difficult to extend the array size for high resolution imaging. In this poster, a 3-D camera
with column-level BGL suppression scheme is presented for high resolution outdoor
applications. The sensor achieved over 100klx BGL suppression with the smallest pixel
size of 5.9-μm among all reported TOF sensors. Though the array size in the prototype
chip is QVGA, it can be easily extended to a larger array thanks to the smallest pixel. The
array can also be dynamically reconfigured by binning and superresolution techniques,
providing spatial and/or temporal resolution controllability. This, in turn, enables an
adaptable imaging for the optimal performance in various conditions by compromising the
spatial resolution, frame-rate, and BGL suppression performance.
Acknowledgements
This research was supported by Samsung Advanced Institute of Technology in South
Korea.
130
Resonant Infrared Detector Arrays
Vikrant J. Gokhale1 and Mina Rais-Zadeh1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor
This work presents design, fabrication and measured results demonstrating the use of
gallium nitride (GaN) based micromechanical (MEMS) resonator arrays as uncooled,
high-sensitivity, fast response, low-noise infrared (IR) detectors. The resonator arrays
batch fabricated using single crystal GaN-on-SOI, and commonly used MEMS process
technology. Incident IR radiation is absorbed in a thin film silicon nitride absorber layer
that is deposited in top of the mechanical resonators, causing a proportionate increase in
the temperature of the device. This increased temperature changes the resonance
frequency of the resonators. The mechanism of sensing is this change in frequency in
proportion to the incident IR radiation. MEMS resonators can potentially provide highlyaccurate and sensitive measurements even for low levels of incident radiation. Interfering
effects such as changes in pressure or ambient temperature can be eliminated by
comparing the sensor response to that of a reference resonator that is uncoated with
silicon nitride, but identical in all other aspects to the sense resonator. Each array of
sensors can have one such reference. The small format resonator array prototypes are
characterized for their RF and thermal performance and exhibit a radiant responsivity of
1.68%/W, thermal time constant on the order of 556 µs and an average IR responsivity of
-1.5 % when compared to a reference resonator, for a 100 mK radiation-induced
temperature rise. The current results show promise for optimized designs that can
compare with state of the art uncooled IR detectors.
This research was supported in part by the National Science Foundation and the Army
Research Laboratory through participation in the MAST CTA.
131
A Reconfigurable Characterization, Control, and Compensation System for
MEMS Rate and Rate-Integrating Gyroscopes
Jeffrey Gregory1, Christopher Boyd2, Jong-Kwan Woo3, Khalil Najafi4
1 Departament of Electrical Engineering , University of Michigan – Ann Arbor
Inertial sensors are valuable in many applications including automotive, consumer
electronics, robotics, vehicle navigation systems, and distributed environmental
monitoring systems. MEMS gyroscopes and accelerometers offer the advantages of low
power operation, small size, and reduced cost through batch fabrication. However, MEMS
devices require a readout interface and control system in order to achieve high
performance operation as sensors. Among these sensors, a gyroscope can be operated
in a mode-matched rate-mode for increased sensitivity or rate-integrating mode for greatly
increased dynamic range and bandwidth, however controlling this as a sensor is
challenging. This work focuses on developing a software/hardware co-design to assist in
the characterization, control, and compensation of MEMS gyroscopes. The platform was
built using FPGA based hardware and open source software at a cost of less than $1000.
When operated in the rate mode the system provides amplitude, rate, and quadrature
closed loop feedback which improves the noise and stability performance over 400%
compared to open loop operation. The system can also operate in rate integrating mode
and has the advantage of continuous gyroscope operation, unlike previous systems
where operation time is limited by ring down time. The next phase of this project will
examine the effectiveness of multiple DSP-based control schemes for inertial sensors and
implement an optimized control system on an ASIC. Our ultimate goal is to achieve a
navigation-grade inertial microsystem which only occupies an area of 10mm3.
The authors thank Mr. Robert Gordenker for testing support.
132
A Microdischarge-Based Monolithic Pressure Sensor
Xin Luo1, Christine Eun2, Jun-Chieh Wang2, Zhongmin Xiong2, Mark Kushner2, Yogesh B.
Gianchandani1, 2
1
Mechanical Engineering, University of Michigan, Ann Arbor
Electrical Engineering and Computer Science, University of Michigan, Ann Arbor
2
This work describes the investigation of a microdischarge-based approach for sensing the
diaphragm deflection in a monolithically fabricated pressure sensor. Microdischargebased transduction is advantageous for harsh environments, such as those encountered
in oil exploration and production, because of its immunity to temperature and inherently
large signals. The device consists of a deflecting Si diaphragm with a sensing cathode
and a glass substrate with an anode and a reference cathode. The total exterior volume
of the device is 0.05 mm3; typical electrode size and separations are 35 µm and 10 µm.
Pulsed microdischarges are initiated in a sealed chamber formed between Si and glass
chips and filled with Ar gas. External pressure deflects the Si diaphragm and changes the
interelectrode spacing, thereby redistributing the current between the anode and two
competing cathodes. The differential current, expressed as (I1-I2)/(I1+I2), is indicative of
the diaphragm deflection which is determined by the external pressure. A 6-mask
microfabrication process is investigated for device fabrication. Electrode connections to
the interior of the chamber are provided by laser drilling and copper electroplating through
high aspect ratio glass vias. The Si and glass substrates are bonded by Au-In eutectic.
The re-distribution of plasma current between competing cathodes, as a consequence of
diaphragm deflection over a range of pressure (0–40 MPa), was experimentally
demonstrated.
133
A Pulsed High-Voltage Generator Utilizing a Monolithic PZT Element and
Evaluation of Nonlinear Piezoelectric Behavior in Transient Mode
Xin Luo1, Yogesh B. Gianchandani1, 2
1
2
Electrical Engineering and Computer Science, University of Michigan, Ann Arbor
This work presents a monolithic pulsed high-voltage (HV) generator utilizing a single
piezoelectric element (PZT51 disk, 5 mm in diameter and 740 µm thick) with electrodes
series-connected via a flexible polyimide cable. The design, fabrication, assembly, and
testing of the HV generator are described. In response to transient mechanical load, the
HV generator is evaluated within the stress range from 1 MPa to 5 MPa, and the
corresponding peak output voltages vary from 100 V to 900 V. Performance comparison
between single-electrode pair HV generator without electrodes series-connection and
three-electrode pair device indicates that series-connected electrodes on a monolithic
PZT element greatly boost the output voltage under the same mechanical load conditions.
In further tests, the generated high-voltage pulses exceed 1.35 kV and are successfully
used to initiate microdischarges on monolithically patterned electrodes across a 75 µm air
gap. The measured capacitance of the test HV generator is 25 pF and the calculated
charge delivered to the terminal electrodes in each discharge is 34 nC. The nonlinear
piezoelectric property of the PZT51 in transient mode is studied. We experimentally
obtain a linear increase of the effective piezoelectric coefficient as the applied pressure
increases within the range from 1 MPa to 5 MPa.
134
A Vibration Harvesting System for Bridge Health Monitoring Applications
James McCullagh1 and Khalil Najafi1
1
Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, MI
Energy harvested from vibrations on a bridge can be used to power bridge health
monitoring sensors. Sensing a bridge’s structural integrity at hard to reach positions will
be made easier if energy can be harvested to power these sensors, eliminating the need
for expensive and inconvenient wired power or battery replacement. This abstract
presents a system comprising of electronics and an electromagnetic energy harvester
used for harvesting the low-frequency, low amplitude, and non-periodic vibrations present
on bridges. The energy harvester in this system is the Parametric Frequency Increased
Generator (PFIG). The PFIG, designed at Michigan, uses a non-resonant architecture
that up-converts the low frequency bridge vibrations found on bridges to higher
frequencies. Multiple passive and active circuit designs have been built to boost, rectify,
and store the PFIG’s output. A passive circuit design uses the PFIG’s two outputs that are
fed into two transformers. The transformer outputs are fed into two cascaded three-stage
Cockcroft multipliers. This design has been used in short-term and long-term testing on
the New Carquinez bridge in CA. Best results showed that an average of 5 µW was
harvested over a period of 120 seconds by the PFIG. The electronics could regularly
charge a 10 µF storage capacitor to between 1 V and 2 V. Long-term tests have shown
that the system has remained operational for 13 months demonstrating its robustness. A
full-wave IC-based active diode charge pump capable of sub-threshold start-up and high
efficiency harvesting with ~16× boosting has recently been designed for this system.
This work was funded, in part, by National Institute of Standards and Technology (NIST)
Technology Innovation Program (TIP) under Cooperative Agreement Number
70NANB9H9008
135
High-Q 3–D Resonators Fabricated with a Novel Blowtorching Molding
Technique
Tal Nagourney1, Jae Yoong Cho1, Khalil Najafi1
A novel method of producing high-Q three-dimensional resonators with a computerized
blowtorch is introduced. A 100 µm-thick chip of fused silica is placed over a graphite
mold, quickly heated to its softening point (~1585 °C), and pulled into the mold with
vacuum. Fused silica has been selected in this case for its isotropic structure and high
quality factor, but this technique can be applied to any material with a softening
temperature within the ~2500 °C range of the propane-oxygen torch. Major advantages of
this technique over traditional micromachining include the ability to make devices with a
large height/width ratio, fast fabrication time (several seconds for feature definition), and
low operating cost. This project focuses on the definition of hemispherical and half-toroid
(birdbath) shapes, with potential application for a rate-integrating gyroscope. Using this
technique, birdbath resonators with a resonant frequency of ~10 kHz and quality factor of
249k have been fabricated.
136
79.5pJ/pixel Bio-Inspired Time-Stamp Based Optic Flow Sensor for Micro Air
Vehicles
Seokjun Park1, Jaehyuk Choi1, Jihyun Cho1 and Euisik Yoon1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor,MI, USA
A vision-based autonomous navigation utilizing optic flow as front-end information is a
promising approach for micro-air-vehicle (MAV) applications, not only because the power
source of the MAV system is extremely limited, but also because its application is
indispensable where GPS signal does not reach. Conventional optic flow algorithms, such
as Lucas-and-Kanade, require huge amount of calculation; therefore, they require
substantial digital hardware (CPU and/or FPGA) on a system. As an alternative approach,
bio-inspired elementary motion detector (EMD) based algorithms (or neuromorphic
algorithms) are studied and implemented in a form of analog VLSI circuits for autonomous
navigation. However, pure analog signal processing is easily susceptible to temperature
and process variations to provide a stable optic flow. Also, the analog processing should
be implemented in pixel-level circuits; as a result, it is difficult to either scale the pixel size.
In this paper, we report a bio-inspired analog/digital mixed-mode optic flow sensor. This
sensor employs a time-stamp-based optic flow algorithm, which is modified from the EMD
algorithm to give an optimum partitioning of hardware blocks in analog and digital
domains. Temporal filtering is remained in a pixel-level analog processing unit. Feature
detection and time-stamp latching blocks are implemented using digital circuits in column
parallel. Finally, time-stamp information is decoded into velocity from simple arithmetic
circuits, thus significantly reducing core digital processing power consumption. The
sensor estimates 1-D optic flow from the integrated mixed-mode algorithm core and 2-D
optic flow with an external time-stamp processing. The sensor provides 1-D 8-b optic
flows at 79.5pJ/pixel.
Acknowledgments
This research was supported by the U.S. Army Research Laboratory under contract
W911NF and prepared through collaborative participation in the Microelectronics Center
of Micro Autonomous Systems and Technology (MAST) Collaborative Technology
Alliance (CTA).
137
Piezoelectrically Transduced Fused Silica Higher-order Lamè Mode
Resonators
Adam Peczalski1, Zhengzheng Wu1, Vikram Thakar2, and Mina Rais-Zadeh1,2
1
2
Department of Electrical Engineering and Computer Science, University of Michigan - Ann Arbor
Department of Mechanical Engineering, University of Michigan - Ann Arbor
This paper reports a micro-machined piezoelectric MEMS resonator for use in timing
devices. Microelectromechanical system (MEMS) resonators seek to replace current
quartz-based timing references by offering a cheap, batch produced, small form factor
alternative with equivalent or better performance. Fused silica was chosen as the
resonating material for its strong thermal and mechanical characteristics, which include
low acoustic loss, thermal conductivity, and coefficient of thermal expansion. An
additional benefit of fused silica is its low thermoelastic damping (TED) at low MHz
frequencies, where silicon devices can show significant loss. The resonating mode was
chosen as a Lamè mode for its low anchor loss and TED, providing a high performance
resonator. Higher-order Lamè modes were chosen in order to decrease motional
impedance, increase power handling, and decrease squeeze-film damping, all of which
are required to realize a high performance timing reference. This work shows fabricated
resonators in both the second- and third-order Lamè modes. The second-order mode
shows a center frequency at 8 MHz with a loaded Q of 17,400 (unload 18,100) and a
motional impedance of 2.475 kΩ, while the third-order mode shows a center frequency at
12 MHz with a loaded Q of 17,300 (unloaded 18,400) and a motional impedance of 1.604
kΩ. The maximum measured f·Q product of these resonators is 2.071011, which is a 3x
improvement over previously published fused silica devices. Future work will focus on
improving device Q and further investigating designs for higher-order modes.
This work was funded by DARPA under the Timing and Inertial Measurement Unit (TIMU)
program.
138
iGC1: An integrated fluidic system for gas chromatography including
Knudsen pump, preconcentrator, column, and detector, micro-fabricated by
a three-mask process
Yutao Qin1, Yogesh B. Gianchandani1
Abstract: This work reports an integrated micro gas chromatography (μGC) system, which
contains four components: a Knudsen pump (KP), a preconcentrator-focuser (PCF), a
separation column and a gas detector. All the four components are fabricated from glass
wafers using a three-mask process with minimal post-processing. In a stackable
architecture, the components are finally assembled into a 4-cm3 system. The Knudsen
pump operates based on the thermal transpiration in nanoporous mixed-cellulose-ester
membranes, and produces a measured 0.4 sccm air flow with 1 W power. The
preconcentrator absorbs vapor analytes and produces a <2 sec injection peak. The
column separates the analytes with an efficiency of ≈2600 plates/m. The gas detector
creates microdischarges with emission spectra, which indicate the quantities of analytes
eluting the column. The stacked system demonstrates the successful separation and
detection of an alkane mixture in the range of C5-C8 in <60 sec.
Acknowledgements: The study was supported in part by the Microsystems Technology
Office of the Defense Advanced Research Projects Agency High-Vacuum Program
(DARPA Contract #W31P4Q-09-1-0011). Facilities used for this research included the
Lurie Nanofabrication Facility (LNF) operated by the Solid-State Electronics Laboratory
(SSEL) and the University of Michigan. The authors thank Prof. Ken Wise and Mr. Robert
Gordenker for providing access to test facilities, Mr. Seungdo An for wafer metallization,
and Dr. Naveen Gupta, Dr. Jing Liu, Mr. Xin Luo, Prof. Katsuo Kurabayashi, and Prof.
Xudong Fan for discussions.
139
Micro-Hydraulic Structure for High Performance Biomimetic Air Flow Sensor
Arrays
Mahdi M. Sadeghi1, Khalil Najafi1
1
We introduce a novel micro-hydraulic structure to significantly improve performance of
many MEMS devices. The micro-hydraulic system in conjunction with application-specific
appendages can realize high-performance sensors and actuators. For instance,
biomimetic hair-like structures can provide airflow sensing with high accuracy and high
resolution. Moreover, hairs with small footprints enable array fabrication to provide
redundancy, fault tolerance and directional sensitivity. In previous works, the high
accuracy is achieved at the expense of dynamic range. Using a micro-hydraulic structure
we fabricated and tested a new type of low-power, accurate and robust flow sensor in
which a hair-like appendage is used to translate flow into hydraulic pressure. This
pressure is sensed with an integrated capacitor within the micro-hydraulic system by
which the sensitivity is amplified. The airflow sensor can detect flow speeds ranging from
about 2 mm.s-1 to over 15 m.s-1 with a resolution of 1.7 mm.s-1. This corresponds to about
78.9 dB of range to minimum detection ratio, which is the highest range over resolution
ratio to our best of knowledge. An array of sensors can realize 2D directional sensing with
13° angular resolution.
The micro-hydraulic structure can be used as a platform to realize many cross-disciplinary
high-performance devices. We have used this platform to make tactile sensors
resembling human skin that are highly needed in humanoid robotics. Additionally, these
structures have been tested in actuation mode to form micro-valves for micro-fluidic
circuitry. The significant impact of this work is its advancement and applicability to other
important research and commercial applications.
This work is funded, in part, by MAST Program of the Army Research Lab under Award
Number W911NF-08-2-0004.
140
Miniature Wireless Magnetoelastic
Selectable Bi-directional Rotation
Resonant
Motor
with
Frequency
Jun Tang1, Scott R. Green1, Yogesh B. Gianchandani1
1
Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan
This work presents the analysis, fabrication, and experimental results of wirelessly
actuated, chip-scale rotary motors. Two designs are described. Design M is actuated by
a ø8 mm magnetoelastic stator lithographically micromachined from Metglas™ 2826MBbulk-foil with 25 µm thick. It operates at a resonant frequency of 11.35 kHz while a 3 Oe
DC and a 2 Oe-amplitude AC magnetic field are applied. The measured rotation speed,
start torque, calculated driving step size, and payload are 44 rpm, 2 nN•m, ≈23 millidegree and 9 mg, respectively. Design S uses a stator that is a sandwich of Si (ø8 mm
diameter and 65 µm thick) and magnetoelastic foil (ø8 mm diameter and 25 µm thick) to
tailor the stiffness. The typical resonant frequency of clockwise (CW) mode and
counterclockwise (CCW) mode are 6.1 kHz and 7.9 kHz, respectively. The CCW mode
provides a rotation rate of about 100 rpm, start torque of 30 nN•m, driving step size of 74
milli-degree, while a 8 Oe DC and a 6 Oe-amplitude AC magnetic field are applied. Bidirectional rotation is realized by switching the applied frequency, thereby exciting the
stator in a slightly different mode shape. Design S shows at least 100 mg payload
capability.
141
Technology for Fabricating Dense 3-D Microstructure Arrays for Biomimetic
Hair-Like Sensors
Yemin Tang1, Rebecca L. Peterson1, and Khalil Najafi1
1 Departament of Electrical Engineering , University of Michigan, Ann Arbor
The project focuses on design, fabrication and simulation of highly-dense arrays of 3-D
high-aspect ratio MEMS structures that can imitate biological hairs. Hair has many unique
properties including high aspect ratios, local neural processing, robustness, and
multiplicity of functions. A key feature of our arrays is the tall, 3-D structure which allows
for spatially efficient integration of traditional MEMS resonators which use a large mass to
bend a much smaller spring. The sensors can be combined in series or in parallel and
can include local signal processing using underlying CMOS circuitry. We implement 2axis capacitive acceleration sensor arrays. Each sensor consists of a proof mass atop a
narrow post. The post acts as mechanical spring and the mass is surrounded by four
walls for capacitive sensing of deflection. The sensor is fabricated using a silicon-on-glass
(SOG) process. DRIE is used to define the small capacitive gaps while simultaneously
etching more deeply to separate neighboring sensors. The device is modeled in
COMSOL to maximize sensitivity within the available process windows. Based on these
simulations, the mass height is fixed at 400 µm and the average gap is ~6 µm. The gap
can be further reduced by refilling it. After DRIE the Si wafer is bonded to a glass wafer
which has been prepared with recesses and metal electrodes. By taking advantage of
high aspect ratio DRIE and SOG process, we have fabricated a new class of highly dense
3-D MEMS sensor arrays which offer improvements in performance, robustness, and
multi-sensor functionality.
142
Optimization of support tether geometry to achieve low anchor loss in Lamé
mode resonators
Vikram Thakar1 and Mina Rais-Zadeh1,2
1
2
Department of Electrical Engineering, University of Michigan, Ann Arbor
The quality factor (Q) of micromachined resonators in the sub-GHz regime is most often
limited by anchor loss (design dependent) rather than the fundamental material
dissipation limits1. In this work we study the fundamental cause of anchor dissipation in
Lamé- or wineglass-mode resonators and show that by optimizing the resonator tether
geometry, low anchor losses can be achieved2, making it possible to reach the intrinsic
f×Q limit of the resonator.
In order to support the Lamé-mode resonance, the tethers are required to undergo forced
flexural vibrations. As a consequence the anchor loss in such resonators is strongly
dictated by the resonance frequency of the tether and for tether geometries having
resonances far from the Lamé-mode frequency, the device shows a much higher anchor
Q. To verify this hypothesis, finite element analysis of the structures is performed using
COMSOL using the Perfectly Matched Layer (PML) approach 3 . For experimental
characterization, devices are fabricated on a low-resistivity SOI substrate with 1 μm
actuation gaps. Both the simulation and measurement results are found to corroborate
the presented hypothesis. Using such an optimization technique, a high-Q Lamé-mode
resonator operating in its fundamental mode at 41.5 MHz is demonstrated with a Q of
296,000 (in vacuum, at room temperature, and 300 V bias). The f×Q of the resonator is
1.23×1013, which is close to the fundamental limit for silicon1.
This work is supported by NASA under the Chip-Scale Precision Timing Unit project. The
authors acknowledge A. Peczalski and Z. Wu for useful discussions and staff at the LNF
for their help with the device fabrication.
1
R. Tabrizian, M. Rais-Zadeh and F. Ayazi, Transducers, 2009.
L Khine and M. Palaniapan, J. Micromech. Microeng., vol. 19, pp. 015017, 2009.
3
D. Bindel and S. Govindjee, Int. J Numer. Meth. Eng., vol. 64, pp. 789-818, 2005.
2
143
Environmentally stable piezoelectric-on-silica MEMS oscillator
Zhengzheng Wu1, and M. Rais-Zadeh1,2
1 Departament of Electrical Engineering Department, University
2
Mechanical Engineering Department, University
Microelectromechanical (MEMS) resonators and oscillator have shown great potential in
realizing miniaturized and integrated timing references. In this work, a high performance
MEMS clock reference is implemented for a chip-scale timing and inertia measurement
unit. For the first time, we have demonstrated a low phase-noise MEMS oscillator based
on a fused silica micro-mechanical resonator. The resonator is implemented using a
piezoelectric-on-silica structure, achieving high quality factor (Q ~15,860) and low
motional impedance (Rm ~360Ω) at 5 MHz. By interfacing the resonator to a CMOS
amplifier, an oscillator phase noise of -138 dBc/Hz at 1 kHz and -155 dBc/Hz at far-fromcarrier has been achieved. Vibration tests on the oscillator indicate a low acceleration
sensitivity of less than 4 ppb/g. The noise performance of this oscillator is among the best
between all reported MEMS oscillators. As an ultra-stable master clock, temperature
stability of the oscillator is improved by combining both passive and active compensation
techniques. A two-resonator temperature sensing and compensation scheme based on
phase-lock technique has been designed. Low power and low noise CMOS integrated
circuit design has been investigated in order to realize temperature sensing and the
thermal control algorithms. Such active temperature compensation scheme is expected to
reduce environment-induced drifts of the MEMS clock and other sensors on the platform
by orders of magnitude. Therefore, the compensation can push the miniaturized silica
MEMS sensor fusion platform to various demanding and emerging applications, such as
inertia navigation.
144
Design, and fabrication of high aspect ratio MEMS meandering springs
Chuming Zhao1, Katherine Knisely+1, Karl Grosh1*
1
*[email protected]
Flexible meandering structures are often introduced in microelectrical-mechanical
systems (MEMS) to increase mechanical compliance in prescribed directions of motion.
In order to tune the device performance, an understanding of the stiffness of the spring
structure is essential. Many variables in the microfabrication process can affect the
meander compliance including choice of photoresist, exposure and development time,
sidewall profile and undercut of photoresist. In this study, we present a finite element
analysis (FEA) model, using COMSOL, which we use to optimize a high aspect ratio
meander spring that has high lateral compliance and sufficient stiffness in orthogonal
directions to resist motion under gravity, for instance. The spring is designed to be with
width from 10um to 20um, height from 20um to 40um, amplitude from 50um to 100um,
and length from 250um to 350um. A non-dimensional variable is introduced to study the
effect of those geometric parameters. Different shapes of meanders are also studied.
Selected designs are then fabricated in the Lurie Nanofabrication Facility (LNF) using
lithography and gold electroplating. Gold is chosen as the material of the meanders for its
high malleability and ductility. Trenches with height to width aspect ratio of 4:1 are
achieved by using photoresist KMPR 1025 as the mold for electroplating. As high aspect
ratio electroplating has a number of challenges, we discuss typical failures and potential
issues of the fabrication process. The geometry of the FEA model is modified to fit the
actual meanders in order to get a more accurate result.
145
Optics, Photonics, and SolidState Devices
146
Vertical Ge/Si Nanowire Heterojunction Devices
Lin Chen, Wayne Fung, and Wei Lu
1
Departament of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor
Different vertical nanowire heterojunction devices were fabricated and tested based on
single Ge nanowire grown epitaxially at low temperature on (111) Si substrate. VaporLiquid-Solid growth and our transfer-free process resulted in a sharp and clean Si/Ge
interface. The nearly-ideal Si/Ge heterojunction has a well-controlled, abrupt doping
profile which was verified through material analysis and electrical characterization. In the
nSi/pGe heterojunction diode, an ideality factor of 1.16, sub-picoampere reverse
saturation current and rectifying ratio of 106 were obtained; while the n+Si/p+Ge structure
leads to Esaki tunnel diodes with high peak tunneling current of 4.57 kA/cm 2 and negative
differential resistance at room temperature. The large valence band discontinuity between
Ge and Si in the nanowire heterojunction was further verified in the p +Si/pGe structure,
which showed a rectifying behavior instead of an Ohmic contact and raised an important
issue in making Ohmic contacts to heterogeneously integrated materials. All
measurement data can be well explained and fitted by theoretical models with known
material parameters, suggesting that the Si/Ge nanowire system offers a very clean
heterojunction interface with low defect density and holds great potential as a platform for
future high density, high performance electronics.
The authors acknowledge partial support of this work by the National Science Foundation
(ECS-0601478 and ECCS-1202126). This work used the Lurie Nanofabrication Facility
(LNF) at UM, a member of the National Nanotechnology Infrastructure Network (NNIN)
funded by the NSF.
147
Stable few-layer MoS2 rectifying diodes formed by plasma-assisted doping
Mikai Chen1, Hongsuk Nam1, Sungjin Wi1, Xiaogan Liang1
1
Mechanical Engineering, University of Michigan
Molybdenum disulfide (MoS2) and other two-dimensional layered transition metal
dichalcogenides recently attracted a great deal of interest because of their excellent
electronic, optoelectronic, and mechanical properties.
To explore new mechanical/chemical mechanisms and process for tailoring the band
structures of 2D LTMD micro-/nanostructures to achieve desirable characteristics for
device applications in various fields, my first step is to develop upscalable techniques for
realizing controlled doping and creating p-n junctions in MoS2 and other 2D
semiconductors, which are demanded for making LTMD-based complementary electronic
circuits and optoelectronic devices.
To meet this milestone, I developed and studied a new doping method for creating stable
p-n junctions in MoS2 using the selected-area plasma treatment of few-layer MoS2 flakes.
Such plasma-doped diodes exhibit high forward/reverse current ratios and a superior
long-term stability at room temperature.
Furthermore, the transport and X-ray photoelectron spectroscopic characterizations of
MoS2 transistors treated with different plasmas systematically confirm that the rectifying
characteristics of plasma-created MoS2 diodes are attributed to plasma-induced p-doping
and p-n junctions in MoS2.
This method is anticipated to play an important role in the development of MoS2-based
nanoelectronic devices. In addition, the presented plasma-assisted doping process has
been demonstrated to be able to produce MoS 2-based ambipolar and p-type transistors
that have not been achieved by other groups.
Acknowledgment. This work is supported by NSF grant CMMI-1232883 and ECCS1307744. The authors would like to thank the staff of Electron Microbeam Analysis
Laboratory for providing the support of XPS characterization; the staff of Lurie
Nanofabrication Facility for providing the support of device fabrication.
148
Random Telegraph Noise and Resistance Switching Analysis of Oxide
Based Resistive Memory
Shinhyun Choi1, Yuchao Yang1, and Wei Lu1
1 Departament of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor
Resistive random access memory (RRAM) devices (sometimes termed “memristors”) are
widely believed to be a promising candidate for future memory and logic applications.
Although excellent performance has been reported, the nature of resistance switching is
still under extensive debate.
We perform systematic investigation of the resistance switching mechanism in a TaOx
based RRAM through detailed noise analysis, and show the resistance switching from
high-resistance to low-resistance is accompanied by the accumulation of oxygenvacancies. Specifically, pronounced random-telegraph noise (RTN) with values up to 25%
was observed in the device high-resistance state (HRS) but not in the low-resistance
state (LRS). Through time-domain and temperature dependent analysis, we show the
RTN effect shares the same origin as the resistive switching effects, and both can be
traced to the (re)distribution of oxygen vacancies (VOs). From noise and transport
analysis we further obtained the density of states and average distance of the V Os at
different resistance states, and developed a unified model to explain the conduction in
both the HRS and the LRS and account for the resistance switching effects in these
devices.
The authors thank J.H. Lee, L. Chen and P. Sheridan for useful discussions. This work
was supported in part by the National Science Foundation (NSF) CAREER award (ECCS0954621), and by the AFOSR through MURI grant FA9550-12-1-0038 and grant FA955012-1-0441. S.H. Choi is supported in part by Samsung Scholarship. This work used the
Lurie Nanofabrication Facility at the University of Michigan, a member of the National
Nanotechnology Infrastructure Network (NNIN) funded by NSF.
149
Radiative Decay Rate Enhancement of InGaN Site-Controlled Quantum Dots
in a Silver Cavity
Brandon Demory1, Tyler Hill2, Chu-Hsiang Teng1, Lei Zhang2, Hui Deng2, and Pei-Cheng
Ku1
1
2
Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MI
Department of Physics, The University of Michigan, Ann Arbor, MI
InGaN quantum dots show single photon emission potential at higher temperatures, but
the long radiative lifetimes on the order of tens of nanoseconds limit the potential
applications. One way to address the long lifetimes is to increase the local density of
states near the quantum dot. Coupling an emitter to a cavity alters its decay rate by the
Purcell Factor and changes the density of states of the system. The Purcell factor for a
metallic cavity depends on the dipole orientation, metal film thickness, and the spacing
between the metal film and the emitter. By adjusting these parameters, we can change
the magnitude of the decay rate enhancement and the ratio of the radiative enhancement
to non-radiative enhancement. Simultaneously, due to the shape of our InGaN quantum
dot pillar structure, the silver cavity’s resonance wavelength is highly tunable by adjusting
the same film thickness parameters. Previously, we have shown Radiative decay rate
enhancement and Photoluminescence Intensity enhancement using a silver cavity with a
Quantum efficiency of 60% at the resonance wavelength of 430nm. In this work, we
demonstrate that with an optimized cavity structure we can achieve Radiative decay rate
enhancements of ~80x with a Quantum efficiency of 75% at the resonance wavelength of
460nm.
This work is funded, in part, by the National Science Foundation
150
Electrically driven polarized single photon emission from InGaN quantum dot
in a single GaN nanowire
Saniya Deshpande1, Junseok Heo1, Ayan Das1 and Pallab Bhattacharya1
1
48109-2122, USA
In a classical light source, such as a laser, the photon number follows a Poissonian
distribution. For quantum information processing and metrology applications, a nonclassical emitter of single photons is required. A single quantum dot (QD) is an ideal
source of single photons and such single photon sources in the visible spectral range
have been demonstrated with III-nitride and II-VI based single quantum dots. It has been
suggested that short wavelength blue single photon emitters would be useful for free
space quantum cryptography, with the availability of high speed single photon detectors in
this spectral region. Here, we demonstrate blue single photon emission with electrical
injection from an In0.25Ga0.75N quantum dot in a single nanowire. The emitted single
photons are linearly polarized along the c-axis of the nanowire with a degree of linear
polarization of ~70%.
151
Selection rule-based transmission filtering of a single-layer dielectric grating
Justin M. Foley1, Steve M. Young1, and Jamie D. Phillips1,2
1
2
Applied Physics Program, University of Michigan
Electrical Engineering and Computer Science Department, University of Michigan
Spectral manipulation is ubiquitous in today’s society where personal electronics including
cell phones, tablets, computers, and cameras require the ability to focus light onto a CCD,
reflect light back to a viewer’s eyes and filter light to provide red, green and blue pixels.
Optical components used in these applications generally consist of metallic mirrors, glass
lenses and absorption-based filters, which are ill-suited for many applications since
ordinary glass is not transparent across all wavelengths, dyes are not always opaque,
and metallic mirrors can absorb heavily upon transmission. Thermal imaging, in particular,
is extensively used in surveillance, remote sensing, and spectroscopy where many
conventional optical materials and components cannot function properly. Developing
reliable and low-cost components to work in this spectral range would enable the next
generation of thermal imaging systems, including hyperspectral capabilities where the
electromagnetic spectrum is generated for each pixel within a viewing plane.
We report our progress on narrowband transmission filters based on lossless dielectric
gratings that show potential to enhance thermal imaging capabilities. The optimized
suspended silicon gratings exhibit greater than 90% reflectance between 8 and 14 µm at
normal incidence with resonant transmission peaks developing away from normal
incidence. We use finite element analysis to model the spectral response, which agrees
well with the experimental results. Using modal analysis that permits complex propagation
constants, we show the resonant phenomenon is a consequence of interference between
wave-guided modes within the grating that can be understood using a simple slab
waveguide model.
152
Stochastic memristive devices for computing and neuromorphic applications
Siddharth Gaba1, Patrick Sheridan1, Jiantao Zhou+1, Shinhyun Choi1 and Wei Lu1
1 Departament of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor.
Nanoscale resistive switching devices (memristive devices or memristors) have been
studied for a number of applications ranging from non-volatile memory, logic to
neuromorphic systems. However a major challenge is to address the potentially large
variations in space and time in these nanoscale devices. Here we show that in metalfilament based memristive devices the switching can be fully stochastic. While individual
switching events are random, the distribution and probability of switching can be well
predicted and controlled. Rather than trying to force high switching probabilities using
excess voltage or time, the inherent stochastic nature of resistive switching allows these
binary devices to be used as building blocks for novel error-tolerant computing schemes
such as stochastic computing and provides the needed “analog” feature for neuromorphic
applications. To verify such potential, we demonstrated memristor-based stochastic
bitstreams in both time and space domains, and show that an array of binary memristors
can act as a multi-level “analog” device for neuromorphic applications.
The authors thank Dr. Zhengya Zhang, Phil Knag and Lin Chen for useful discussions.
This work was supported in part by the AFOSR through MURI grant FA9550-12-1-0038
and by the National Science Foundation (NSF) through grant CCF-1217972. This work
used the Lurie Nanofabrication Facility at the University of Michigan, a member of the
National Nanotechnology Infrastructure Network (NNIN) funded by NSF.
153
Three-Dimensional Vertical Dual-Layer Oxide Memristive Devices
Siddharth Gaba1, Chao Du1 and Wei Lu1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor.
The exponential growth in the semiconductor industry in the past a few decades has been
largely driven by device scaling following Moore’s law. However, as the transistor size
reaches sub-10 nm regime, continued scaling faces a number of fundamental and
technical challenges. In addition to the lateral scaling based on continued shrinkage of the
device size, vertical scaling that aims at enhancing the device performance or
functionality through expansion in the vertical direction is now being widely researched for
future memory and logic applications. In particular, resistive memories (RRAMs) based on
two-terminal resistive switching devices have attracted broad attention due to their
compatibility with vertical scaling
In this poster, we fabricate and show that vertical, 3D dual layer resistive switching
devices based on WOx exhibit well-defined analog memristive behavior. The device
characteristics in the dual layer stack are closely matched and exhibit excellent
incremental potentiation and depression characteristics with no degradation up to ten
thousand cycles. The demonstration of vertical, multi-layer memristive devices fabricated
in CMOS friendly fashion makes them well suited for analog memory or large-scale
neuromorphic computing applications.
The authors thank L. Chen, P. Sheridan and Dr. Y. Yang for useful discussions. This work
was supported in part by the Air Force Office of Scientific Research (AFOSR) through
MURI grant FA9550-12-1-0038. This work used the Lurie Nanofabrication Facility at the
University of Michigan, a member of the National Nanotechnology Infrastructure Network
(NNIN) funded by the NSF.
154
Molybdenum as a contact material for solution-processed zinc tin oxide thin
film transistors
Wenbing Hu1 and Rebecca L. Peterson1
1
Solution-processed zinc tin oxide (ZTO), as an indium-free transparent amorphous oxide
semiconductor, is an inexpensive, non-toxic candidate for future printed electronics. For
high-speed, high-current, short-channel thin film transistors (TFTs), the source and drain
contact resistance must be minimal and stable. Here we show that Mo is a superior
contact material for solution-processed ZTO TFTs.
The gate electrode and dielectric are formed by p+-Si thermal SiO2. ZTO was deposited
by spin-coating [1] and patterned by wet etch. ITO, Mo or Au/Ti source/drain electrodes
were deposited and patterned by lift-off. The TFT channel length varies from 3 µm to
400 µm. Transmission line measurements are used to extract contact resistance
properties. The width-normalized contact resistance of Mo/ZTO, Au/Ti/ZTO and ITO/ZTO,
is 8.7Ω•cm, 90.7Ω•cm and 163.4Ω•cm respectively, comparable to or smaller than
previously reported metal-ZTO contacts [2-4]. The small Mo/ZTO contact resistance
results in a higher effective mobility of ~5.9 cm 2/(V•s) for narrow channel devices. The
results show that Mo can be used as a contact material for sub-micron TFTs.
This project is funded by National Science Foundation ECCS Award #1032538. Portions
of this work were performed in the Lurie Nanofabrication Facility, a site of the National
Nanotechnology Infrastructure Network, which is funded in part by NSF.
References:
[1] Hu, et al., J. Mater. Res. 27 (2012) 2286.
[2] Jackson, et al., Appl. Phys. Lett. 87 (2005) 193503.
[3] Yang, et al., Appl. Phys. Lett. 98 (2011) 122110.
[4] Avis, et al., J. Mater. Chem. 22 (2012) 17415.
155
High speed high sensitivity carbon-nanomaterial based chemical and
biological sensors
Girish Kulkarni1 and Zhaohui Zhong1
1
Department of Electrical Engineering and Computer Science, University of Michigan Ann Arbor
Nanosensors based on the unique electronic properties of 1-D and 2-D nanomaterials
have the potential to revolutionize the field of rapid on-site chemical and biological
detection. Most of the current nanoelectronic chemical and biological sensors rely
ubiquitously on the detection of electrochemical potential or conductance change
associated with the adsorbed charges on the surface. However, such charge-based
direct-current (DC) detection has many limitations. For example, DC chemical sensors
suffer from extremely slow sensing response and recovery (~10-100s of seconds), which
arises from the slow dynamics of interface trapped charges. In biological sensors, directcurrent detection fails in physiologically relevant background concentrations (~100mM),
where the sensitivity of devices suffers from Debye screening effect due to mobile ions
present in the solution. Here, we report a radically new sensing mechanism for chemical
and biological detection wherein we operate carbon nanomaterial based field-effecttransistors as high-frequency mixers and measure the adsorbed molecules’ dipole
moment rather the associated charge. We demonstrate for the first time, high speed (~0.1
s) and extremely high sensitivity (< 1ppb detection limit) detection of chemical vapors on
a pristine graphene device without any surface functionalization. To demonstrate the
universality of our technique, we use a carbon-nanotube based high-frequency mixer
platform and detect streptavidin-biotin binding in 100mM background salt solutions, an
environment where conventional charge-based techniques fail. These results not only
open the door for a novel frequency-mixing based nanoelectronic sensing methodology,
but can also lead to rapid and highly sensitive nanosensors ideally suited for real time onsite chemical/biological analysis.
Acknowledgement: The work is supported by the National Science Foundation Scalable
Nano-manufacturing Program (DMR-1120187). This work used the Lurie Nanofabrication
Facility at University of Michigan, a member of the National Nanotechnology Infrastructure
Network funded by the National Science Foundation.
156
Non-Destructive
Optoelectronics
Wafer
Recycling
for
Low-Cost
Thin-Film
Flexible
Kyusang Lee1, Jeramy D. Zimmerman1, Tyler W. Hughes2, and Stephen R. Forrest 1,2,3
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor,
Department of Physics, University of Michigan, Ann Arbor
3
Department of Material Science and Engineering, University of Michigan, Ann Arbor
2
Compound semiconductors are the basis for many of the highest performance optical and
electronic devices in use today. Their widespread commercial application has, however,
been limited due to the high cost of substrates. Device costs can, therefore, be
significantly reduced if the substrate can be reused in a simple, totally non-destructive
and rapid process. Here, we demonstrate a method that allows for the indefinite reuse
and recycling of wafers, employing a combination of epitaxial “protection layers”, plasma
cleaning techniques that return the wafers to their original, pristine and epi-ready
condition following epitaxial layer removal and adhesive-free bonding to a secondary
plastic substrate. We demonstrate the generality of this process by fabricating high
performance GaAs-based photovoltaic cells, light emitting diodes, and metalsemiconductor field effect transistors that are transferred, without loss of performance,
onto flexible and lightweight plastic substrates, and then the parent wafer is recycled for
subsequent growth of additional device layers. Our process leads to a transformative
change in, device cost, arising from the inevitable consumption of the wafer that
accompanies conventional epitaxial liftoff followed by chemo-mechanical polishing.
The authors thank Jaesang Lee and Xiao Liu for assistance with LEDs measurements,
and the Army Research Laboratory MAST program and Global Photonic Energy Corp. for
partial financial support of this work.
.
157
Angle-insensitive color filters employing highly absorbing materials
Kyu-Tae Lee1, Sungyong Seo1, Jae Yong Lee1, and L. Jay Guo1
1
Department of Electrical Engineering and Computer Science, The University of Michigan.
Color filters have played a crucial role as a key element for a wide variety of applications
such as liquid crystal display, light emitting diodes, and complementary metal-oxidesemiconductor (CMOS) image sensors. Traditional color filters utilize organic dyes that
are susceptible to surrounding environment, for example, longstanding UV illumination
and high temperature resulting in a degradation of performance over time. Additionally,
the size of the dye-based filters cannot be scaled down to the order of several hundred
nanometers, mainly due to the small absorption of the color pigment. Owing to higher
durability to both heat and constant UV radiation exposure, color filters, which rely on
photonic subwavelength gratings based on guided-mode resonance, and plasmonic
nanostructures, have recently been under intensive investigation to overcome the
aforementioned problems. However, most plasmonic and photonic based color filters
suffer from a resonance shift which occurs when light is incident upon the device at
different angles of incidence. This resonance shift results in an undesirable color change,
dramatically limiting the use of this type of filter today. Therefore, there is a strong need to
improve the angular dependence property of color filters. Here, we demonstrate the color
filters with wide viewing angles up to  70 degrees based on a strong resonance behavior
in a lossy material. The underlying physics behind improved angular dependence of
proposed filters is investigated by numerical calculation and experiment.
158
Observation of an unexpected ultrafast photo-Dember field in
graphene
Chang-Hua Liu1, You-Chia Chang2, Ted Norris1.2 and Zhaohui Zhong1
1
2
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109
The photo-Dember effect arises from the asymmetric diffusivity of ultrafast photoexcited
electrons and holes, which create a spatial charge distribution and transient dipole
radiation. Conventionally, this effect was exhibited strongly in bulk semiconductors with
the large asymmetry of electron-hole mobility, such as GaAs or InAs. In contrast, the
photo-dember effect was principally considered negligible in graphene due to its similar
electron and hole mobilities.. Here, we utilize photocurrent spectroscopy and observe the
formation of intense photo-Dember field when exciting graphen-metal interface with
femtosecond laser. Scanning photocurrent measurements reveal the polarity of
photocurrent is determined by device mobility. Furthermore, ultrafast pump probe
measurements indicate the magnitude of photocurrent is related to hot carrier cooling
rate. Our simulations suggest intense field originates from graphene truly 2D nature
combined with its low electronic specific heat. Taken together, our results indicate
ultrafast photoresponse in graphene could be strongly correlated with its electrical
properties, atomic structure as well as light-graphene interaction. This observations are
both of fundamental interest and relevant for applications in future graphne-based
terahertz emitters.
This work was supported by the National Science Foundation Center for Photonic and
Multiscale Nanomaterials (DMR 1120923), and by NSF CAREER Award (ECCS1254468). Devices were fabricated in the Lurie Nanofabrication Facility at University of
Michigan, a member of the NSF National Nanotechnology Infrastructure Network.
159
Scattering nanostructures for angle selective light management in
semitransparent photovoltaics
Brian Roberts1, Qi Chen1, and P.-C. Ku1
1
Semitransparent photovoltaics (PVs) have the potential to enable widespread light
harvesting when integrated with buildings and windows, though their conversion efficiency
is limited by an intrinsic tradeoff between absorption and transparency. To address this
drawback, we propose an angle selective PV window system which transmits normally
incident light for visibility while selectively absorbing light at an elevated angle (including
direct sunlight). This functionality can be realized by exploiting the optical backscattering
properties of high aspect ratio nanostructures.
Two nanostructured systems of interest are studied and described. Metal nanorods can
be engineered to selectively backscatter angled light via their localized surface plasmon
resonance, though they are difficult to fabricate and introduce optical losses to the
system. Dielectric nanopores, such as those of self-assembled anodized aluminum oxide
(AAO) films, can also enable angle selective light management via coherent scattering
processes, including scattering to extreme near-horizontal angles and guided modes in
accompanying PV films.
Research supported as part of the Center for Solar and Thermal Energy Conversion
(CSTEC), an Energy Frontier Research Center funded by the U.S. Department of Energy
(DOE), Office of Science, Basic Energy Sciences (BES), under Award # DE-SC0000957
160
Machine learning with memristive devices
Patrick Sheridan1, Wen Ma1, Chao Du1, Wei Lu1
1
Machine learning can improve the efficiency and accuracy of data analysis from a variety
of sources, such as email spam filter and facial recognition technologies. While these
learning algorithms can be implemented with traditional CMOS transistors, implementing
them with novel nanoelectronic devices can save significant amounts of time, space, and
energy. Further, the unique dynamics afforded by these devices mimic neuron behavior
found in real biological systems.
This work presents the simulation of machine learning tasks implemented with
nanoelectronic resistive switching (memristive) device networks. Memristive device
dynamics were modeled after tungsten oxide (WOx) devices, which were characterized
using a set of diverse inputs. Spike-timing-dependent plasticity, a phenomenon observed
in multiple brain regions, was employed to train the weights of neural network while
conserving energy. The development of receptive fields, or input pattern selective neuron
activation, in an unsupervised learning algorithm was demonstrated with potential uses in
pattern recognition and image compression.
Further, the study of nanoeletronic networks can provide insights into how neurons are
able to collectively compute complex functions and can improve machine learning
development and application.
We would like thank DARPA for funding this research.
161
Polarization-controlled Single Photon Emission from Site-controlled InGaN
Quantum Dots
Chu-Hsiang Teng1, Lei Zhang2, Tyler Hill2, Brandon Demory1, Hui Deng2, Pei-Cheng Ku1
1
2
Department of Physics, University of Michigan, Ann Arbor
Single photon emission and potential single photon emitters have been studied
extensively in the past decades because they are critical for quantum information
technologies. Moreover, a lot of applications require linearly polarized single photon
emission. In this work, we present a polarization control scheme of single photon
emission from InGaN quantum dots (QDs) based on manipulating the QD geometry. The
polarization control was achieved by engineering asymmetric strain relaxation and
valence band mixing. Simulation was performed to investigate the strain and electronic
structures and revealed that III-nitride QDs provide better polarization properties than
other III-V QDs. Experimentally, InGaN QDs were fabricated by top-down approach. The
shape, size, and position were determined by E-beam lithography. Microphotoluminescence measurements were carried out and revealed linearly polarized
emission and controlled polarization properties from InGaN QDs. More importantly, single
photon emission with designated polarization properties was demonstrated
experimentally for the first time.
162
Heterojunction n-ZnSe/p-ZnTe Solar Cells
Alan S. Teran1, Chihyu Chen2, Jamie D. Phillips1, 2
1
2
Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MI
Department of Applied Physics, The University of Michigan, Ann Arbor, MI
Heterojunctions based on II-VI materials can be used to increase the efficiency of multijunction solar cells, and may also offer the opportunity to realize next generation
approaches such as the intermediate-band solar cell (IBSC) based on highly-mismatched
alloys or quantum dots. One material of particular interest is ZnTe:O, where IB solar
energy conversion has been demonstrated. Efficient doping in many II-VI materials,
however, is often a major obstacle to achieving high-quality junction diodes. ZnTe is no
exception, where efficient p-type doping is possible, but n-type doping is difficult to obtain.
In this work, studies of n-ZnSe/p-ZnTe heterojunction solar cells grown by molecular
beam epitaxy on GaAs and GaSb substrates will be reported. Dark current-voltage (I-V)
measurements show improved reverse saturation current and ideality factor for the solar
cells grown on GaSb. These improvements agree with I-V measurements done under
illumination where short-circuit current (JSC,GaSb = 2.13 mA/cm2, JSC,GaAs = 0.53 mA/cm2),
open-circuit voltage (VOC,GaSb = 0.84 V, VOC,GaAs = 0.54 V), and fill-factor (FFGaSb = 0.43,
FFGaAs = 0.37) are improved for the solar cells grown on GaSb. Temperature dependent IV (T-I-V) measurements allow us to identify and understand the nature of the limiting
features of our solar cells, demonstrating a strong linear dependence of Voc on
temperature with the solar cells grown on GaSb having larger activation energy (EA,GaSb =
1.55 eV, EA,GaAs = 1.44 eV). The design and future directions for ZnSe/ZnTe
heterojunction solar cells will be presented, including the application of these
heterojunctions to ZnTe:O IBSCs.
This work was jointly funded by the National Science Foundation Materials World Network
DMR-1006154 and the bilateral US-Spain Research Programme with Contract
C11.0910B.01.
163
Dispersion Engineering for Vertical Microcavities using Sub-wavelength
Gratings
Zhaorong Wang1, Bo Zhang2, Hui Deng2
1
2
Department of Electrical Engineering and Computer Science Department, University of Michigan
Department of Physics, University of Michigan
Energy dispersion is a fundamental property of a confined system. It defines the distinct
features of different dimensionalities—the density of states (DOS), effective mass, phase
and group velocity of the eigen-modes. Dispersion engineering of the photonic modes has
been implemented via metamaterial and photonic crystals to enable novel optical
functionalities. However all existing methods have their limitations of either loss or
evanescent nature. Here we show the possibility of engineering cavity dispersion using a
high-index-contrast subwavelength grating (SWG) as the top mirror of a conventional
DBR cavity. The phase responses of the SWG is investigated in a revealing way, which
helps us to both understand the physical origins and guide dispersion engineering via the
resonance phase condition. Our results imply many applications under the research area
of cavity-quantum electrodynamics (CQED), particularly in polariton research and
devices.
Thanks NSF and AFOSR for funding. Thanks Pavel Kwiecien for rcwa-1d code.
164
Ultra-high efficiency small molecule photovoltaic cell with a fullerene-based
electron filtering buffer
Xin Xiao1, Kevin J. Bergemann2, Jeramy D. Zimmerman1, Kyusang Lee1, Stephen R.
Forrest1,2,3
1
Department of Physics, University of Michigan, Ann Arbor, MI
3
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI
2
Small molecule organic photovoltaic (OPV) cells have attracted intense interest owing to
their high purity, ease of processing, and minimal batch-to-batch variation in device
performance. The power conversion efficiency (PCE), however, has not attained values of
interest for commercial use. Recently, we have developed an efficiency planar-mixed
heterojunction (PM-HJ) based on tetraphenyldibenzoperiflanthene (DBP) and C70. The
optimal cell has achieved a PCE of 6.4 ± 0.3% under 1 sun illumination. However, the fill
factor (FF) is relatively low, which limits the device performance. Here, we employ a
fullerene-based mixed buffer in PM-HJ cell, acting as an electron filter buffer, which can
spatially separate excitons and electrons and, therefore, reduce both bimolecular
recombination and exciton-polaron quenching. FF is significantly increased from 56 ± 1 %
to 66 ± 1 %. The optimal DBP:C70 cell with the electron filter buffer results in PCE = 8.1 ±
0.4% under 1 sun illumination, which is the highest reported efficiency for OPV cells
grown by vacuum thermal evaporation. Moreover, we incorporate DBP:C 70 cells into a
tandem cell. Previous tandem cells demonstrated in our lab suffered from a low FF
characteristic of the SubPc:C70 graded HJ as a back subcell. By replacing the previous
back subcell with a DBP:C70 PM-HJ cell, along with a solvent-annealed blended
squaraine bilayer cell as a front subcell, the tandem achieves PCE = 8.3 ± 0.4 % under 1
sun illumination, which is, to our knowledge, the highest reported efficiency for small
molecule tandem cells in the literature.
This work was funded, in part, by the Center for Solar and Thermal Energy Conversion at
the University of Michigan, the SunShot NextGenII Program of the Department of Energy,
Global Photonic Energy Corp.
165
The Simulation on Pit-Defect in Stressed AlGaN/GaN High Electron Mobility
Transistors by Nanostructure Evolution
Jung Hsiang Yang1
1
Department of Electrical Engineering and Computer Science, University of Michigan-Ann Arbor
AlGaN/GaN high electron mobility transistors (HEMTs) has widely been designed to the
high-frequency and high-power application for many years. However, when the device is
operated at high voltage, an unpreventable electrical degradation is induced. The detailed
studies about reliability issue are still required and the length of pit-defect is one of critical
indicators to examine the performance of device. In this project, 2-D finite element
method (FEM) is implemented to understand the growth of pit-defect near the gate
contact edges by nanostructure evolution. The COMSOL with MATLAB software package
is completely exploited in the overall study and the evolution model considers the
interface migration, atom diffusion and the electric field from the applying voltage. The
important dimensional parameters like gate length (Lg) and distance from gate contact to
drain contact (Sgd) are carefully studied.
There are three findings from the simulating results. First, the pit-depth growths in the
source-side and drain-side have stronger linear relationship with the drain voltages. This
confirms that the electrical degradation can possibly be more serious if the higher drain
voltage applied under OFF-state. Second, the depths of pit-defect in both sides are
inversely proportional to the Sgd. Moreover, a significant pit-defect growth when the Sgd
decrease from 1 µm to 0.5 µm. Finally, the degree of pit-defect growth in the device
becomes much larger with the decrease of gate length. It can be explained that the
smaller gate length can dominate the pit-defect growth even though there is a long
enough Sgd.
166
Systems Engineering and
Communication
167
Polar Codes Achieve the Shannon Capacity and RateDistortion Function
Aria Ghasemian1, Sahebi1, and S. Sandeep Pradhan1
1
Department of Electrical Engineering and Computer Sceince, University of Michigan
Polar codes were originally proposed by Arikan for discrete memory-less channels
(DMCs) with binary input alphabets. Polar codes over binary-input channels are linear
codes capable of achieving the “symmetric capacity” of channels and are constructed
based on the Kronecker power of the
matrix
. It was later shown that Polar
codes can achieve the symmetric capacity of arbitrary DMCs. These codes are the first
known class of codes achieving the symmetric capacity of channels with an explicit
construction. The symmetric capacity of a channel is defined as the mutual information
between the channel input and the channel output when the input distribution is confined
to be uniform. The symmetric capacity coincides with the true (Shannon) capacity only for
a small fraction of channels called symmetric channels and in general it can be very small
compared to the true capacity of the channel.
In this paper, we show that Polar codes can achieve the Shannon capacity of (binary or
non-binary) DMCs. We show that using two polar codes, one contained in another, in the
form of a “nested’ code, the input distribution of the channel can be “shaped” to any
arbitrary distribution. The novelty of the approach is to break the (non-symmetric) channel
coding problem into two simpler problems: A source coding problem with a symmetric
source and a channel coding problem with a symmetric channel.
We also show that Polar codes can achieve the true (Shannon) rate-distortion function for
the source coding problem as opposed to the “symmetric rate-distortion” function
available in the literature.
168
Group Learning and Opinion Diffusion in a Broadcast Network
Yang Liu1, Mingyan Liu1
1
Department of Electrical Engineering and Computer Science: Systems, University of Michigan, Ann Arbor
We analyze the following group learning problem in the context of opinion diffusion:
Consider a network with $M$ users, each facing $N$ options. In a discrete time setting, at
each time step, each user chooses $K$ out of the $N$ options, and receive randomly
generated rewards, whose statistics depend on the options chosen as well as the user
itself, and are unknown to the users. Each user aims to maximize their expected total
rewards over a certain time horizon through an online learning process, i.e., a sequence
of exploration (sampling the return of each option) and exploitation (selecting empirically
good options) steps. Within this context we consider two group learning scenarios, (1)
users with uniform preferences and (2) users with diverse preferences, and examine how
a user should construct its learning process to best extract information from other's
decisions and experiences so as to maximize its own reward. Performance is measured
in {\em weak regret}, the difference between the user's total reward and the reward from a
user-specific best single-action policy (i.e., always selecting the set of options generating
the highest mean rewards for this user). Within each scenario we also consider two
cases: (i) when users exchange full information, meaning they share the actual rewards
they obtained from their choices, and (ii) when users exchange limited information, e.g.,
only their choices but not rewards obtained from these choices.
This work is partially supported by the NSF under grants CIF-0910765 and CNS
1217689.
169
Closing the Price of Anarchy Gap in the Interdependent Security Game
Parinaz Naghizadeh1 and Mingyan Liu1
1
The security of an interconnected system depends on the collective effort of all users in
security technologies. As a result, investment in security by strategic users has been
typically modeled as a public good problem, known as an Interdependent Security (IDS)
game. The equilibria for such games are often inefficient, as selfish users free-ride on
positive externalities of others’ contributions. In this paper, we present a mechanism that
can implement the socially optimal equilibrium in an IDS game through a message
exchange process, in which users submit proposals about the security investment and tax
profiles of one another. This mechanism is different from existing solutions in that (1) it
results in socially optimal levels of investment, closing the Price of Anarchy gap in the IDS
game, (2) it is applicable to a general model of user interdependencies, (3) it does not
need to monitor or audit users, record their incidents, or dictate their investments. We
further consider the issue of individual rationality, often a trivial condition to satisfy in
many resource allocation problems, and argue that with positive externality, the incentive
to stay out and free-ride on others’ investment makes it harder to design an individually
rational mechanism.
170
A Decentralized Routing Problem in a Simple
Queueing System
Yi Ouyang1, Demosthenis Teneketzis1
1
The following routing problem in a queueing system with non-classical information
structure is investigated in discrete time. A service system consists of two service stations
and two controllers; one controller is affiliated with each station. Each station has an
infinite size buffer. The service stations provide the same service with identical
Bernoulli(μ) service time distributions and identical holding costs. Customers requiring
service arrive at one of the service stations. The processes describing the two arrival
streams are independent Bernoulli(λ).At any time, a controller can route one of the waiting
customers in its own service station to the other service station. Each controller knows
perfectly the workload in its own station. Furthermore, it observes perfectly the arrival
stream to its own station as well as the arrivals due to customers routed from the other
service station. The structure of the controllers' routing strategies that minimize the total
expected holding cost is determined. Under certain conditions on the initial workload at
each station, the controllers' optimal routing strategies are explicitly determined.
171
Computing sum of sources over an arbitrary multiple access channel
Arun Padakandla1, Sandeep Pradhan1
1
The problem of computing sum of sources over a multiple access channel (MAC) is
considered. Building on the technique of linear computation coding (LCC) proposed by
Nazer and Gastpar [2007], we employ the ensemble of nested coset codes to derive a
new set of sufficient conditions for computing the sum of sources over an arbitrary MAC.
The optimality of nested coset codes [Padakandla, Pradhan 2011] enables this technique
outperform LCC even for linear MAC with a structural match. Examples of non-additive
MAC for which the technique proposed herein outperforms separation and systematic
based computation are also presented. Finally, this technique is enhanced by
incorporating separation based strategy, leading to a new set of sufficient conditions for
computing the sum over a MAC.
This work was supported by NSF grant CCF-1111061.
172
PHY layer strategies based on algebraic codes for multiplexing information
over broadcast networks
Arun Padakandla1, Sandeep Pradhan1
1
We present an achievable rate region for the general three user discrete memoryless
broadcast channel, based on nested coset codes. We characterize 3-to-1 discrete
broadcast channels, a class of broadcast channels for which the best known coding
technique, which is obtained by a natural generalization of that proposed by Marton for
the general two user discrete broadcast channel, is strictly sub-optimal. In particular, we
identify a novel 3-to-1 discrete broadcast channel for which Marton's coding is analytically
proved to be strictly suboptimal. We present achievable rate regions for the general 3-to-1
discrete broadcast channels, based on nested coset codes, that strictly enlarge Marton's
rate region for the aforementioned channel. We generalize this to present achievable rate
region for the general three user discrete broadcast channel. Combining together
Marton's coding and that proposed herein, we propose the best known coding technique,
for a general three user discrete broadcast channel.
This work was supported by NSF grants CCF-0915619 and CCF-1116021
173
Symmetric Nash Equilibrium in Secondary Spectrum Market
Shang-Pin Sheng1, Mingyan Liu1
1
We consider a secondary spectrum market where multiple primary license holders
(sellers) seek to sell excess bandwidth to secondary users (potential) buyers. The
channels are considered to be heterogeneous while the buyers are assumed to be
identical. We compute the sellers' pricing strategy in the symmetric Nash equilibrium and
show that the pricing decreases when channel quality increases.
174
Distributed Source Coding in Absence of Common Components
Farhad Shirani1
1
We introduce a coding scheme for the distributed source coding problem using two layers
of codes. The first layer code is of constant finite block-length while the second layer code
has block-length approaching infinity. We give a general achievable rate-distortion region
for this scheme. It is shown that the scheme achieves the common component ratedistortion region in the case when the sources have a common component, while if the
common component is replaced with highly correlated functions of the two inputs; it
improves upon existing achievable bounds. We argue that it is beneficial to have the initial
finite-length code to capture the high correlation between components of the two sources.
We show that as the block-length of the first layer code is increased, the transmission rate
required in the scheme decreases, reaches its minimum at some finite value and then
increases. This phenomenon is not typically seen in traditional schemes used in multiterminal source coding.
175
Generalised Proportional Allocation Mechanism Design for Multi-rate
Multicast Service on the Internet
Abhinav Sinha1, Achilleas Anastasopoulos1
1
Department of Electrical Engineering: Systems, University of Michigan
In multicast transmission on the Internet, agents are divided into multicast groups based
on the content they demand. In addition, when multi-rate transmission is used, each user
in the same multicast group may request different quality of service for the same content.
With multi-rate multicast transmission, each link on the network carries only the highest
quality content of each multicast group passing through this link, thus resulting in
substantial resource savings compared to unicast transmission. In this paper two
mechanisms are constructed that fully implement social welfare maximizing allocation in
Nash equilibria for the case of multi-rate multicast service under the assumption of
strategic agents for whom utilities are private information. The first applies to a Weak
Budget Balance setting while the second applies to a Strong Budget Balance setting. The
emphasis of this work is on full implementation, which means that all pure strategy Nash
equilibria of the induced game result in the optimal allocations of the centralized allocation
problem. The mechanism, which is constructed in a quasi-systematic way starting from
the dual of the centralized problem, has a number of additional useful properties.
Specifically, the proposed mechanism results in feasible allocation (in fact in Pareto
optimal allocation) even off equilibrium. Finally, handling the Strong Budget Balance
setting is shown as a simple extension to the mechanism for Weak Budget Balance.
176
Real-time Posterior Matching Scheme for Multiple Access Channels with
Complete Feedback over DMC
Jui Wu1, Achilleas Anastasopoulos1
1
An achievable rate region of the communication systems over a special class of multiple
access channels (MACs) with two transmitters and one receiver with complete feedback
was proposed by Cover and Leung and proved to be the capacity region by Willems.
Inspired by the block-wise transmission scheme in their work, a sequential transmission
scheme could be found. For analysis, first we view the communication system as an
equivalent controlling system operating in discrete time which has sequential encoding
and decoding strategies. With two-stage simplification, another equivalent system is
derived with states which are the posterior distributions. Furthermore, from the converse
part of the proof of the capacity region, a set of necessary conditions for variables in the
system, such as independence between the current state and previous states, is derived.
Based on the derived conditions and the simplified system, a communication system
composed of a sequential posterior matching scheme is established.
177
Control Systems, Power and
Energy
178
Robust Iterative Learning for High Precision Control through L1 Adaptive
Feedback
Berk Altın1, Kira Barton2
1
2
We introduce a modified robust iterative learning control (ILC) framework with L1 adaptive
feedback for single-input single-output (SISO) linear time invariant (LTI) systems with
iteration varying constant parametric uncertainties. We use the adaptive loop to
compensate for nonrepetitive effects (exogenous disturbances and/or uncertainties) and
ensure that the plant, as seen from the ILC input, is sufficiently close to its nominal value
for performance improvement through learning. We reformulate the L1 controller to
accommodate the feedforward input, which results in an adaptation that considers
changes in the system trajectory due to learning. We present a rigorous stability analysis,
and evaluate performance and trade-offs via simulation. Our findings indicate that the
augmentation of the L1 controller with the feedforward input results in an overall controller
that focuses on minimizing the reference tracking error. The design trade-off thus
simplifies to the performance-robustness trade-off that can be seen in the respective
domains of both controllers.
This work was supported by startup funds from the University of Michigan.
179
Control Signal Impact on HVAC Demand Response Efficiency
Ian Beil1, Ian Hiskens1, Scott Backhaus2
1
2
Condensed Matter and Magnetic Science, Los Alamos National Laboratory
Building heating, ventilation, and air conditioning (HVAC) represents a sizable portion of
electrical grid loading. Reducing or offsetting HVAC power through demand response
(DR) has been proposed as a way to alleviate power system stress while avoiding
installation of peak generation. In this research, a commercial HVAC building has been
equipped for DR control through global thermostat resets. A series of experiments was
run to determine the additional energy needed to provide DR services and, by comparing
this behavior to baseline performance, calculate a measure of efficiency. Results suggest
that tuning of the HVAC system parameters and the types of control input applied have a
significant impact on DR performance.
180
Monjolo: An Energy-Harvesting Energy Meter Architecture
Samuel DeBruin1, Bradford Campbell1, Prabal Dutta1
1
Conventional AC power meters perform at least two distinct functions: power conversion,
to supply the meter itself, and energy metering, to measure the load consumption. This
paper presents Monjolo, a new energy-metering architecture that combines these two
functions to yield a new design point in the metering space. The key insight underlying
this work is that the output of a current transformer – nominally used to measure a load
current – can be harvested and used to intermittently power a wireless sensor node. The
hypothesis is that the node’s activation frequency increases monotonically with the
primary load’s draw, making it possible to estimate load power from the interval between
activations, assuming the node consumes a fixed energy quanta during each activation.
This paper explores this thesis by designing, implementing, and evaluating the Monojolo
metering architecture. The results demonstrate that it is possible to build a meter that
draws zero-power under zero-load conditions, offers high accuracy for near-unity power
factor loads, works with non-unity power factor loads in combination with a whole-house
meter, wirelessly reports readings to a data aggregator, is resilient to communication
failures, and is parsimonious with the radio channel, even under heavy loads. Monjolo
eliminates the high-voltage AC-DC power supply and AC metering circuitry present in
earlier designs, enabling a smaller, simpler, safer, and lower-cost design point that
supports novel deployment scenarios like non-intrusive circuit-level metering.
181
Energy Positioning: Economics and Control: Optimal Power Flow with
Storage and Renewable Generation
Jennifer K. Felder1, Ian A. Hiskens2
1
2
Department of Electrical Engineering and Computer Science: Systems, University of Michigan
Solution algorithms for the optimal power flow (OPF) problem are well established for
traditional electricity networks. However, there is an increasing need for integrating
renewable sources and energy storage into electricity networks. These newer devices
have physical properties that require modification of traditional OPF algorithms. In
particular, energy storage devices introduce temporal coupling over the optimization
horizon. This paper explores two algorithms that expand traditional OPF methods to
incorporate energy storage devices and wind generation. The first method is based on a
traditional LP-AC OPF method, while the second is a quadratic program with DC power
flow constraints. The algorithms are demonstrated using several test cases that are
based on a modified RTS-96 system. The performance of the two algorithms is compared
in terms of convergence properties and quality/optimality of their respective solutions.
182
Mitigating Power Fluctuations in Electrical Ship Propulsion Using Model
Predictive Control with Hybrid Energy Storage System
Jun Hou1, Jing Sun1, 2, Heath Hofmann1
1
2
Department of Naval Architecture and Marine Engineering, University of Michigan
Shipboard electric propulsion systems experience large power and torque fluctuations on
their drive shaft due to propeller rotational motions and waves. This paper explores new
solutions to address the fluctuations by integrating a hybrid energy storage system
(HESS) and exploring coordinated power management. A propeller and ship dynamic
model, which captures the underlying physical behavior, is established to support the
control development and system optimization. Given the fact that both high and low
frequency contents exist in the power fluctuations, a combination of battery pack and
ultracapacitor bank is proposed, coordinated control is developed, and performance is
evaluated in different sea conditions. Simulation results show that the proposed HESS
with predictive model reference control provides substantial benefits in terms of reducing
fluctuation and sustaining self-operation, compared to other solutions that involve
batteries or ultracapacitors alone. Moreover, our analysis shows that the benefits of
HESS are achievable only through both effective power management and device
coordination.
Acknowledgement of the U.S. Office of Naval Research (ONR) and the Naval
Engineering Education Center (NEEC)
183
Hybrid dynamic modeling of legged robots with a spinal joint
Mohammad Khodabakhsh1
1
Bio-Inspired Robotics Laboratory, Ecole Polytechnique Federale De Lausanne
Legged systems such as quadrupedal mammals are adept at moving on rough terrain,
unreachable by wheeled vehicles. Many researchers have investigated the effect of
morphology on the locomotive performance of legged robot in attempt to replicate animal
ability [1, 2]. Consideration of various morphological properties such as actuation
mechanisms, geometric specifications, and mass distribution allowed for improved
locomotor performance.
Since performing experiments on robotic platforms is costly and time-consuming,
developing a mathematical model can be helpful. In this poster, we present a hybrid
dynamic model for quadruped robots. Extending previous models, we include a rotational
spinal joint and two point masses in each leg (lower and upper) connected by a prismatic
actuator. Legs connect to trunk via a spring-damper. Elaborating the mass distribution of
the legs allowed for a more realistic model of the collision effects at touchdown compared
with the commonly used Spring Loaded Inverted Pendulum (SLIP) model. Implementing
our model may allow for improved estimates of morphological parameters for the legged
robots to be obtained.
Funded by the European Union 231688 program. This work was performed during an
internship in EPFL, Switzerland, summer 2011.
184
A Hybrid System Provides a Robust Alternative to a Linear Regulator
Matthew D. Kvalheim1, Shai Revzen1
1
"Multiple contact" animal gaits, in which multiple legs touch down nearly simultaneously,
can be modeled by ordinary differential equations with periodic solutions and vector fields
which are smooth except for discontinuities at states representing touch down -- they are
"hybrid systems". The stability of such systems can be studied by considering the stability
their Poincaré maps. We analyze a class of these hybrid systems in comparison to linear
continuous systems with identical Poincaré maps. We compare the robustness to timevarying actuator disturbances of both the hybrid and linear systems through their effect on
the Poincaré maps and present the two-dimensional case.
Let p denote the fixed point of the Poincaré map corresponding to the unperturbed linear
and hybrid systems, and let hn and cn denote the output of the nth iteration of the
Poincaré map for the hybrid and linear systems, respectively. We show that as n
approaches infinity, the Euclidean distance d(hn, p) is immune to suitably bounded
actuator disturbances, whereas the Euclidean distance d(cn, p) depends linearly on
actuator disturbances. We conclude that as a hybrid controller, this system is
fundamentally more robust than a comparable linear regulator. This may help explain the
widespread appearance of multiple contact gaits in many terrestrial animal species.
185
Grazing Concepts for Reachability Analysis of Uncertain Power Systems
Maxim Markov1, Ian A. Hiskens1
1
The dynamic behaviour of power systems is affected by many parameters that cannot be
easily quantified. Load model parameters provide an important example. When major
disturbances occur, more often than not the match between the measured and simulated
responses is substandard, with load models being a major contributing factor. Likewise,
as renewable generation grows, its inherent variability will challenge the usefulness of
traditional approaches to dynamic security assessment that currently rely almost
exclusively on forward simulation.
We will describe an innovative suite of numerical continuation algorithms for analysis and
design of power systems with slow and fast timescales, coupled components, and with
state resets and switches typical of models of power systems. These algorithms provide
understanding of changes in the observed dynamics as system parameters change, and
hence can be used for assessing the impact of parameter uncertainty. In order to scale
the continuation methods to high-dimensional hybrid systems with competing timescales,
new trajectory-discretization algorithms based on asynchronous collocation methods and
associated mesh-adaptation strategies have been developed.
The above techniques form the basis for reachability analysis that can be used to assess
the vulnerability of power systems to undesirable outcomes. This reachability assessment
uses the fact that trajectories which graze the boundary of an undesirable region of statespace demarcate acceptable from unacceptable behaviour. Such grazing trajectories can
be incorporated into the collocation methods via a boundary-value formulation. Multidimensional covering algorithms can then be applied to obtain bifurcation diagrams that
establish boundaries, in parameter space, between safe and unsafe operation.
186
Reactive Power Limitation due to Wind-Farm Collector Networks
Jonathon A. Martin1, Ian A. Hiskens1
1
Type-3 and Type-4 wind turbines are capable of contributing to the reactive power
required by wind-farms for supporting grid voltages. However, characterizing the
maximum reactive power capability of a wind-farm by summing the individual generator
ratings does not account for the effect of voltage variations over the radial collector
network and can significantly overestimate the total reactive power production capacity.
This paper uses a continuation process to show that maximum reactive power production
can be achieved by sending a common control signal to all turbines. The outcome of the
continuation process is explored using an interior-point optimization algorithm. Analysis
suggests that global optimality is achieved. Several examples demonstrate how generator
voltage limits can significantly curtail the reactive power output requested by the control
strategy. This improved characterization of wind-farm reactive power production will
enable better design and operation of wind-farm reactive power resources, reducing the
need for additional shunt capacitors and Statcoms.
187
Transmission Constrained Economic Dispatch: A Public Goods Approach
Erik Miehling and Demosthenis Teneketzis1
1
This report offers a solution to the transmission constrained economic dispatch (TCED)
problem when the agents’ utilities are their private information, agents are non-strategic,
and losses are taken into account using a modified DC power flow method. The modified
DC power flow allows us to solve for the system operating point more accurately than with
the standard DC power flow method. We approach the problem by treating the system as
a public goods network. We first formulate the centralized information problem with
losses; we approximate the total system losses by a strictly convex quadratic function of
the vector of power injections at all nodes in the network; we distribute the losses among
the generators in the system using participation factors. The centralized information
problem is, in general, non-convex. We proceed to solve this non-convex problem as
follows. We decompose it into a sequence of linearized subproblems each of which is
convex; the solution of each subproblem in this sequence is the linearization point of the
next subproblem in the sequence. The solutions of this sequence of subproblems
converge to the optimal solution of the original centralized non-convex problem. For each
convex subproblem in the above sequence we propose an externality algorithm which
satisfies the TCED problem’s informational constraints and converges to the optimal
solution of the subproblem. We thus obtain a nested iterative method/algorithm which
satisfies the TCED problem’s informational constraints and converges to the optimal
allocation of the original non-convex centralized TCED problem.
188
Nonlinear Internal Model Controller Design for Wastegate Control of a
Turbocharged Gasoline Engine
Zeng Qiu1, Jing Sun2, Mrdjan Jankovic3, Mario Santillo3
1
Department of Naval Architecture and Marine Engineering, University of Michigan, Ann Arbor
3
Ford Motor Company
2
This work investigates the design of nonlinear internal model control (IMC) for wastegate
control of a turbocharged gasoline engine. We extend the inverse-based IMC design for
linear time-invariant (LTI) systems to nonlinear systems. A fourth-order nonlinear model
which sufficiently describes the dynamic behavior of the turbocharged engine is
implemented to serve as the model in the IMC structure. To leverage the available tools
for LTI IMC deign, we have explored the quasi linear parameter varying (quasi-LPV)
model. IMC design through transfer function inverse of the quasi-LPV model is ruled out
due to parameter variability. A new approach for nonlinear inverse, referred to as the
structured quasi-LPV model inverse, is developed and validated. The controller based on
this nonlinear inverse is then designed to achieve boost pressure tracking. Finally,
simulations on a validated high fidelity model are carried out to show the feasibility of the
IMC. Its closed-loop performance and robustness are compared with a well-tuned PI
controller with extensive feed-forward and anti-windup built in.
I would like to acknowledge Ford Motor Company for their sponsorship. I wish to show
appreciation to Prof. Jing Sun for her patient guidance and instructions, and to Mrdjan
Jankovic and Mario Santillo for their valuable and constructive suggestions.
189
Resilient Monitoring System for Boiler/Turbine Plant
M. T. Ravichandran1, S. M. Meerkov1 and H. E. Garcia2
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109,
USA
2
Idaho National Laboratory, P. O. Box 1625, Idaho Falls, ID 83415-3675, USA
Resilient monitoring systems are sensor networks that degrade gracefully under malicious
attacks on their sensors, which cause them to project misleading information. The goal of
this work is to design, analyze, and evaluate the performance of a resilient monitoring
system intended to monitor the condition (normal or anomalous) of a boiler/turbine (B/T)
plant. A main feature of the system considered here is that process variables that
characterize the B/T plant are not independent, which leads to the possibility of inferring
the state of one variable using measurements of the other. A four-layer monitoring system
architecture is developed, which consists of data quality assessment, process variable
assessment, plant condition assessment, and sensor network adaptation layers. The
measure of resiliency of the monitoring system is quantified using Kullback-Leibler
divergence and is shown, using simulations, to be sufficiently high in several attack
scenarios.
W.-C Lin of Idaho National Laboratory is acknowledged for his participation in this
research. Support for this research has been provided by the U.S. Department of Energy
under DOE Contract DE-AC07-05ID14517 and performed as part of the Instrumentation,
Control, and Intelligent Systems (ICIS) initiative at the Idaho National Laboratory.
190
A Robust Adaptive Controller for Surface-Mount Permanent Magnet
Machines
David M. Reed1, Jing Sun2, and Heath Hofmann1
1
2
High torque density and the potential for high efficiency have made Surface-Mount
Permanent Magnet machines an attractive option for many high-performance drive
applications. However, parameter variations due to temperature changes, skin effect,
and magnetic saturation, can detune the transient characteristics of the drive, and cause
large mismatches in torque regulation. The approach presented in this paper utilizes a
combination of adaptively tuned feedforward and feedback-decoupling terms, in addition
to standard proportional feedback for added robustness. The resulting controller
achieves consistent transient response characteristics with zero steady-state error over a
wide range of operating points, without the use of integral control. The adaptive law is
derived using Lyapunov's stability theorem, and a robust switching σ-modification is used
to prevent parameter drifting due to the presence of unmodeled disturbances.
Additionally, overactuation is exploited to allow the use of persistently exciting inputs
without compromising the control objective (torque regulation). The performance of
resulting robust adaptive torque regulator is analyzed and tested numerically in Simulink.
Experimental results confirm the performance of the proposed adaptive controller.
This work was supported by funding from the U.S. Office of Naval Research (ONR) and
the Naval Engineering Education Center (NEEC).
191
Mitigating the Impact of Wind Power Variability on Subtransmission Networks
Sina Sadeghi Baghsorkhi1 and Ian Hiskens1
1
Department of Electrical Engineering and Computer Sciences, University of Michigan
Wind power variability, in weak grids, can significantly alter the voltage profile and flow
patterns across the network. Due to high sensitivity of voltage magnitudes to wind
injection, distribution (<40kV) and sub-transmission (40-120kV) network operators are
requiring the voltage at the point of interconnection of the wind farm to be “strictly”
regulated. The introduction of large sizes of local reactive compensation (for voltage
regulation) is starting to interfere with the key voltage regulator of distribution and subtransmission networks, the on-load tap changing transformer (OLTC). We have
investigated this interaction and proposed a coordinated voltage control scheme that
minimizes the tap-changing operations of OLTC transformers induced by variation in wind
generation. This method, by reducing the tap operations extends the lifetime of these
critical and costly components of the power system while facilitating larger penetration
levels of wind power.
192
Optimized Energy Harvesting Methods and Power Electronics for Variable
Capacitive Devices
Aaron Stein1 and Heath Hofmann1
1
The utility of wireless sensor nodes can be extended by harvesting ambient energy to
power them. Variable capacitive energy harvesters are typically micro-electromechanical
systems (MEMs). In order to effectively harvest energy from these devices, highlyefficient power electronic circuitry is extremely important and can be the difference
between generating or losing energy during the harvesting cycle. Two basic methods of
harvesting energy from these devices are known: Constant Voltage and Constant
Charge. However, other harvesting cycles have been developed which combine the
properties of the basic methods: the Passive Method and the Constant Charge with a
Parallel Capacitor Method. All four methods have been reported; however, the literature
is lacking a formal comparison of these methods. This paper evaluates these four
methods while considering circuit efficiency as a parameter. By including efficiency as a
parameter new fundamental properties can be derived: a threshold efficiency for energy
harvesting, analytical solutions for optimal operating conditions, and a more realistic
comparison of the four methods at nominal operating conditions. These properties
demonstrate the advantage of using the passive method and lead to a proposed design
which implements two DC-DC converters to operate the variable capacitive device at its
optimal operating conditions.
193
Optimal Energy Procurement from a Strategic Seller with Renewable
Generation
Hamidreza Tavafoghi1, Demosthenis Teneketzis 1
1
We consider a mechanism/contract design problem for energy procurement, when there
is one buyer and one seller. We assume that the buyer has all the bargaining power and
therefore is the mechanism designer. The seller has the ability to generate power from a
conventional plant and a non-conventional plant (renewable). The generation from the
non-conventional plant is not deterministic, it depends on a random variable W (e.g.
weather), which is realized at the time of production, and the seller's technology, which is
her private information. There is a cost of energy produced from the conventional plant;
this cost depends on the seller's technology, which is her private information. The seller's
expected utility is given by the payment she receives from the buyer for the energy
delivered minus the expected cost of energy production. The buyer's utility is given by his
benefit from the energy he receives minus the payment he makes to the seller. This utility
is the buyer's private information.
The objective is to design a mechanism/contract that maximizes the buyer's expected
utility, and guarantees the voluntary participation of the seller.
We prove that the solution to the problem is a menu of contracts from which the seller
chooses one based on her technologies.
194
Ensuring Privacy in Location-Based Services: An Approach Based on
Opacity Enforcement
Yi-Chin Wu1, Karhik Abinav2, Stéphane Lafortune1
1
2
Department of Computer Science and Engineering, Indian Institute of Technology, Madras
Opacity is an information-flow property that characterizes whether the secret of the
system can be inferred by an observer. In this work, we study the location privacy in
Location-Based Services (LBS) as the notion of opacity in Discrete Event Systems. We
show that privacy can be enhanced using the framework of opacity insertion enforcement
mechanism that we proposed in our prior work. Non-deterministic finite state automata
are used to capture the mobility model of LBS users. Using the opacity verification
techniques, we show how LBS server can infer the accurate location of the user by
tracking queries that contain only generalized spatial information. To enhance location
privacy, we deploy i-enforcing insertion functions that insert fictitious queries to the user’s
original query sequences. With the i-enforceability property, the insertion functions
provably generate convincing fictitious queries such that modified queries are always
consistent with the mobility model and thus LBS server can never know for sure the
user’s accurate location. Finally, to minimize the overhead from fictitious queries, we
design an optimal insertion function that introduces the minimum average number of
fictitious queries.
This work was partially supported by the NSF Expeditions in Computing project ExCAPE:
Expeditions in Computer Augmented Program Engineering (grant CCF- 1138860).
195
A General Approach for Synthesis of Supervisors for Partially-Observed
Discrete-Event Systems
Xiang Yin1, Stéphane Lafortune1
1
We revisit the synthesis of supervisors for partially-observed discrete-event systems from
a new angle, based on the construction of a new structure called the All Inclusive
Controller (or AIC). We consider control problems for safety specifications, where the
legal language is a prefix-closed sublanguage of the system language. We define the AIC
as a transition system that embeds all safe supervisors and thus all controllable and
observable sublanguages of the legal language. The structure of the AIC is that of a
bipartite graph, reminiscent of a game between the supervisor and the system, with (i)
control states, where all safe control decisions are enumerated, and (ii) system states,
where all feasible observable system events are executed. The states of the AIC are
information states, i.e., subsets of system states. We present an algorithm for the
construction of the AIC. This algorithm exploits the pre-computation of the so-called
extended specification, which makes the safety of a control state a function of the current
information state alone, thereby allowing for on-the-fly construction of the AIC, if so
desired. We discuss the properties of the AIC. We also describe how the AIC can be used
for synthesis of supervisors that posses desired maximality and/or optimality properties.
This work was partially supported by the NSF Expeditions in Computing project ExCAPE:
Expeditions in Computer Augmented Program Engineering
(grant CCF-1138860).
196
Finite-Element-Based Computationally-Efficient Electric Machine Model
Suitable for Integration in Vehicle Design Optimization
Kan Zhou1, Andrej Ivanco2, Zoran Filipi2, Heath Hofmann1
1
2
Department of Automotive Engineering, Clemson University
Electric machines and their corresponding power electronic circuitry are not only a key
component of electric/hybrid electric vehicle powertrains, but also play important roles in
traditional vehicles as generators to provide on/off-board power generation. It is therefore
important that vehicle-system-level design and control engineers have access to accurate
computationally-efficient, physics-based modeling tools of the electromagnetic behavior of
electric machines. The ability to quickly generate and simulate electric machine designs is
crucial for vehicle-level design and optimization. For example, efficiency maps of an
electric machine design are a useful tool for vehicle system designers.
In this paper, electric machine design scaling techniques are proposed to easily and
flexibly generate new machine designs. The efficiency maps of the scaled designs are
then calculated based on a “base design” database generated by 2D magneto-static finite
element analysis (FEA), without the necessity of re-solving computationally-intensive FEA
for each scaled designs. Results show that the proposed techniques can be extremely
useful for vehicle powertrain-level or system-level design and optimization. With these
techniques, powertrain or system designers can easily and quickly adjust the
characteristics and the performance of the machine in ways that are favorable to the
overall vehicle performance.
*This work is supported by the Automotive Research Center (ARC), a U.S. Army Center
of Excellence for Modeling and Simulation of Ground Vehicles led by the University of
Michigan. This work has been submitted to the 2014 Twenty-Ninth Annual IEEE Applied
Power Electronics Conference and Exposition (APEC).
197
Electrical Engineering: Signal
and Image Processing
198
Accelerated MRI Field Map Estimation
Michael J. Allison1, Jeffrey A. Fessler1
1
In magnetic resonance imaging (MRI), inhomogeneity in the main magnetic field can
cause artifacts. However, these artifacts can be corrected with accurate estimates of the
field inhomogeneity. The majority of field inhomogeneity estimators use multiple scans
with varying echo times to avoid phase wrapping in the estimate. One such method [1],
uses a penalized-likelihood approach consisting of a sinusoidal data-fit term and a
quadratic regularizer that promotes smoothness in the estimate. This method is highly
accurate and robust to phase wrapping, but its current minimization strategy is
computationally expensive. In this work, we develop methods to accelerate the
computation of this estimator.
We begin by extending the separable quadratic surrogate (SQS) minimization method in
[1] to define a set of quadratic surrogate functions for the penalized-likelihood cost
function. We then consider two minimization frameworks where we can use these
functions: Huber's algorithm for quadratic surrogates [2] and a non-linear conjugate
gradient (NCG) method. For the case of Huber's algorithm for quadratic surrogates, the
minimization strategy requires iteratively solving a linear system of equations based on
our quadratic surrogate functions. For the case of the NCG method, we use our quadratic
surrogate functions for both preconditioning the problem as well as for a monotonic line
search strategy [3]. Numerical experiments on a simulated dataset found that all of the
minimization methods converged to similar estimates with our new methods doing so
approximately 20 times faster than the existing SQS method.
This work was funded, in part, by NSERC and NIH-CA87634.
[1] A. Funai et al., IEEE-TMI, 27(10), 2008. [2] P. Huber, Robust Statistics, pp. 184-5,
1981. [3] J. A. Fessler et al., IEEE-TMI, 8(5), 1999.The
199
Performance of Regularized Canonical Correlation Analysis (RCCA)
Nicholas Asendorf1, Raj Rao Nadakuditi1
1
Department of Electrical and Computer Engineering, University of Michigan
Multi-modal data fusion is a challenging but common problem arising in fields such as
economics, statistical signal processing, medical imaging, and machine learning. In such
applications, we have access to multiple datasets that use different data modalities to
describe different system features. Canonical correlation analysis (CCA) is a
multidimensional data fusion algorithm used to extract correlated features from exactly
two datasets. CCA uses the SVD of the empirical covariance matrices to find a linear
transformation for each dataset such that the transformed datasets are maximally
correlated. However, when the number of observations is less than the combined
dimension of the datasets, CCA deterministically returns a perfect correlation between the
datasets. In an effort to overcome this undesired property of CCA, a regularized version
(RCCA) is regularly employed in the sample starved regime.
In this work, we explore the performance of RCCA. We first use random matrix theory to
theoretically predict the distribution of the RCCA correlations when the data matrices are
purely noise. We then compare the performance of CCA and RCCA when used to detect
the presence of a correlated signal in noisy datasets. This analysis shows that RCCA
provides little improvement in detection performance and is especially sensitive to the
choice in regularization parameter. Motivated by insights from random matrix theory, we
provide an informative CCA (ICCA) algorithm that, unlike CCA and RCCA, is able to
reliably detect correlated signals in the sample starved regime.
Work partially supported by the US Army Research Office (ARO) under grant W911NF11-1-0391.
200
Deep Community Detection using Local Fiedler Vector Centrality
Pin-Yu Chen1 and Alfred O. Hero1
1
In this poster, a new centrality called local Fiedler vector centrality (LFVC) is proposed to
analyze the connectivity structure of a graph. It is associated with the sensitivity of
algebraic connectivity to node or edge removals and features distributed computations via
the associated graph Laplacian matrix. LFVC can be related to a monotonic submodular
set function that guarantees that greedy node or edge removals come within a factor 11/e of the optimal non-greedy batch removal strategy. Due to the close relationship
between graph topology and community structure, we use the proposed centrality
measure to detect deep and overlapping communities on various real-world social
network datasets. Compared with conventional community detection method, the results
offer new insights on community detection by discovering new significant communities
and key members in the network. Notably, LFVC is also shown to greatly outperform
other well-known node centralities for revealing communities embedded in a graph.
201
Improving Isotropy and Uniformity of Spatial Resolution and Noise
Characteristics for low-dose 3D Axial X-ray CT
Jang Hwan Cho1, Jeffrey A. Fessler1
1
Improved noise and spatial resolution properties are one of the potential advantages of
statistical image reconstruction methods over conventional filtered back-projection (FBP)
reconstruction. Regularized image reconstruction methods, such as penalized weighted
least squares (PWLS) method or a penalized likelihood (PL) method, provide noise
control by integrating a roughness penalty into the cost function. Although statistical
weighting and system models are responsible for improving image quality, their
interaction with a conventional quadratic roughness penalty results in images as
anisotropic and nonuniform spatial resolution and noise. Due to the large number of
voxels in the image volume, regularization design methods based on discrete Fourier
transforms would require prohibitive computational cost. In this study, we propose two
quadratic regularization design methods for 3D axial X-ray computed tomography (CT)
that aim to improve isotropy and uniformity of resolution and noise, respectively. In
addition, the developed method is not limited to improving isotropy and uniformity, but can
be used for promoting other user-defined characteristics. Simulations and a phantom
experiment show that the proposed methods lead to more uniform and isotropic spatial
resolution and noise characteristics in 3D axial CT with modest computational cost.
202
Spatio-Temporal Analysis of Gaussian WSS Processes via
Complex Correlation and Partial Correlation Screening With Applications to
Financial Data
Hamed Firouzi1, Dennis Wei1, Alfred Hero1
1
We propose a framework for spatio-temporal correlation analysis of jointly Gaussian Wide
Sense Stationary (WSS) multivariate time series. The goal is to identify the hub time
series, i.e., the ones that are highly correlated with a number of other time series. When
the dimension of the multivariate time series and the number of time samples are
relatively large, direct correlation analysis in the time domain could be computationally
intractable. As an alternative, we apply the Discrete Fourier Transform to the time series
and perform correlation analysis in the frequency domain. We extend the previous theory
of hub screening to the complex domain to accommodate complex-valued Fourier
transforms. The theory allows p-values to be assigned to time series for being a hub
under the null hypothesis that the time series are independent of each other. It also
specifies thresholds for which thresholded sample (partial) correlation matrices can be
used to identify hubs. We then use an independence property of Gaussian WSS time
series in the frequency domain to perform multiple inference for detecting hub time series.
Experimental results on both synthetic data and real financial data illustrate the accuracy
of our theoretical results and the usefulness of the proposed framework.
The research in this paper was supported in part by AFOSR grant FA955013-1- 0043.
203
Kronecker Sum Decompositions of Spatio-Temporal Data
Kristjan Greenewald1, Theodoros Tsiligkaridis1, Alfred O. Hero III1
1
In this paper we consider the use of the space vs. time Kronecker product decomposition
in the estimation of covariance matrices for spatio-temporal data. This decomposition
imposes lower dimensional structure on the estimated covariance matrix, thus reducing
the number of samples required for estimation. To allow a smooth tradeoff between the
reduction in the number of parameters (to reduce estimation variance) and the accuracy
of the covariance approximation (affecting estimation bias), we introduce a diagonally
loaded modification of the sum-of-kronecker products representation (Tsiligkaridis et al.
2013). We derive an asymptotic Cramer-Rao bound (CRB) on the minimum attainable
mean squared predictor coefficient estimation error for unbiased estimators of Kronecker
structured covariance matrices. We illustrate the accuracy of the diagonally loaded
Kronecker sum decomposition by applying it to video data of human activity.
This research was partially supported by ARO under grant W911NF-11-1-0391 and AFRL
under grant FA8650-07-D-1220-0006.
204
An Iterative, Backscatter-Analysis Based Algorithm For Increasing
Transmission Through Highly-Backscattering Random Media Using Phasemodulated Wavefronts
Curtis Jin1, Raj Rao Nadakuditi1, Eric Michielssen1, and Stephen Rand1
1
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48104
Materials such as turbid water, white pain and egg shells are opaque because it is
impossible for light to pass straight through them. In such media, the randomly arranged
particles cause light to scatter in random directions, thereby frustrating its passage. As
the thickness of a slab of highly scattering random medium increases, this effect becomes
more pronounced, and less and less light is transmitted through.
Surprisingly, it turns out that there are a few highly transmitting wavefronts that achieve
perfect transmission through such media. We describe new, physically-realizable
algorithms that rapidly construct these wavefronts using backscatter-analysis only and
describe phase-only modulated variants of these algorithms that enable their
implementation in optical experiments using phase-only spatial light modulators.
This work was supported by an NSF-CCF award.
205
Fast ordered subsets optimization algorithms using momentum for statistical
X-ray CT image reconstruction
Donghwan Kim1, Sathish Ramani2, and Jeffrey A. Fessler1
1
2
CT Systems and Applications Laboratory, GE Global Research Center
X-ray computed tomography (CT) has been criticized for its radiation exposure to the
patients, and the CT industry and researchers have responded by developing a reduceddose CT machine with sophisticated statistical image reconstruction algorithms to deal
with the noisier measurement data. Statistical image reconstruction provides good images
from low-dose scans, but requires very long computation time for minimizing an X-ray CT
statistical cost function. Therefore, our goal is to develop fast optimization algorithms for
statistical X-ray CT problems. Ordered subsets (OS) methods are widely used in
tomography problems including CT, accelerating the convergence by the number of
subsets ‘M’ in early iterations, by using only a subset of a measurement data per iteration
for computational efficiency. Here, we further accelerate OS algorithms by introducing a
momentum approach that dramatically speeds up the convergence rate. We particularly
combine the OS algorithm with Nesterov’s momentum algorithms, leading to a promising
‘M2’ times acceleration in early iterations. However, we have observed unstable behavior
of the algorithm in some cases, and we propose to adapt diminishing step sizes to
stabilize the algorithm while preserving the fast convergence rate. A real 3D helical CT
scan is used to examine the acceleration of the proposed algorithms.
This work was supported in part by GE Healthcare, the National Institutes of Health under
Grant R01-HL-098686, and equipment donations form Intel.
206
Regularized Image Reconstruction for Parallel MRI using ADMM
Mai Le1, Sathish Ramani2, Jeffrey A. Fessler1
1
2
GE Global Research Center
To reduce motion blur, decrease operation costs, and improve spatial and temporal
resolution, a number of methods to accelerate MRI have been proposed. Sensitivity
Encoded (SENSE) MRI is a method of receiving spatially encoded signals simultaneously
on multiple receive coils, and Compressed Sensing inspired undersampling techniques
have also been proposed to reduce acquisition time. Both SENSE and random
undersampling require spatial regularization for good image quality, but sparsity-based
regularization involves computationally costly nonlinear optimization. Variable splitting
algorithms seek to minimize computation time by decoupling a single, costly nonlinear
optimization into several smaller problems of less computational complexity. In particular,
the AL-P2 method in [1] demonstrated very fast convergence speeds, but did not satisfy
known sufficient conditions for convergence. Here, we present variable splitting
algorithms that satisfy the conditions for the Alternating Direction Method of Multipliers
(ADMM) and subsequently convergence. In particular one proposed method exploits the
structure of 1st-order finite difference regularizers to apply fast tridiagonal matrix
inversions in the inner variable updates. Preliminary results indicate that the image quality
of the new algorithm, ADMM AL-P2 is comparable to that of other variable splitting
methods. Further experiments will compare the speed of ADMM AL-P2 and AL-P2, and
further analysis will characterize the behavior as a function of several algorithmic
parameters.
1. S. Ramani and J.A. Fessler. Parallel MR image reconstruction using augmented
Lagrangian methods, IEEE Trans. Med. Imag., 30(3):694-706, March 2011
207
Sparse positive-definite FIR filter design with Schatten p-norm optimality
Madison G McGaffin1, Jeffrey A Fessler1
1
Department of Electrical Engineering:Systems, University of Michigan
Many models in signal processing can be usefully approximated with circulant operators.
Because circulant matrices are diagonalized by the discrete Fourier transform, the
inverses of these circulant approximations are easy to compute. These model inverses
are particularly useful in preconditioner design for gradient-based optimization, where an
efficient approximation to the inverse of the cost function Hessian is used to determine a
good search direction.
Traditional convergence theory requires that these
preconditioners be positive-definite to ensure convergence, which is simple to enforce on
a dense circulant matrix. The traditional approach to applying these operators is a pair of
fast Fourier transforms and a few scalar operations.
In some applications, even the conventionally "fast" FFT is unacceptably slow. The FFT is
also not ideally suited for modern highly parallel architectures like the GPU, which favor
highly localized memory accesses. In these cases, a few-tap finite impulse response
(FIR) filter implemented with convolution is considerably more efficient.
In this work we consider the problem of designing an FIR filter with few taps that "best"
approximates (in a Schatten p-norm sense) a given dense circulant matrix, while also
remaining positive definite. We propose an iterative algorithm to solve this design
problem and demonstrate the effectiveness of our FIR filter-based preconditioners on a
challenging denoising problem.
Supported in part by NIH grant R01 HL 098686 and a hardware donation by Intel.
208
Distributed Learning of Gaussian Graphical Models via Marginal Likelihoods
Zhaoshi Meng1, Dennis Wei1, Ami Wiesel2 and Alfred O. Hero III1
1
2
School of Computer Science and Engineering, The Hebrew University of Jerusalem
We consider distributed estimation of the inverse covariance matrix, also called the
concentration or precision matrix, in Gaussian graphical models. Traditional centralized
estimation often requires inverse of full covariance matrix through expensive global
inference, which can be computationally intensive in large distributed networks. In this
work, we propose a general framework for distributed estimation based on a maximum
marginal likelihood (MML) approach. Each node independently computes a local estimate
by maximizing a marginal likelihood defined with respect to data collected from its local
neighborhood. Due to the non-convexity of the MML problem, we introduce and solve a
convex relaxation. The local estimates are then combined into a global estimate without
the need for iterative message-passing between neighborhoods. We analyze the behavior
of the proposed estimator in the classical asymptotic regime, and also derive its rate of
convergence to the true parameters in the high-dimensional scaling regime. We show that
under certain assumptions the error due to our computational relaxation is only a lowerorder term compared with the intrinsic statistical estimation error. Numerical experiments
validate our theoretical findings and demonstrate the improved performance of the twohop version of the proposed estimator, which almost closes the gap to the centralized
maximum likelihood estimator at a reduced computational cost.
This research was supported in part by ARO grant W911NF-11-1-0391 and ISF 786/11.
209
OptShrink: An optimal algorithm for estimating a low-rank matrix buried in
noise
Brian Moore1 and Rajesh Rao Nadakuditi1
1
We propose a novel spectral algorithm for estimating a low-rank matrix buried in noise.
Our approach is motivated by recent results in random matrix theory on the eigenvalues
of low-rank perturbations of large random matrices. Specifically, we leverage this theory
to design an optimal data-driven shrinkage function to apply to the eigenvalue spectrum
of the observed data. We show that the resulting algorithm is asymptotically optimal and,
in particular, strictly outperforms the ubiquitous principal component analysis (PCA)
estimator and its so-called robust generalizations. OptShrink is optimal for a large class of
noise models, including the standard setting of independent and identically distributed
(i.i.d.) Gaussian noise.
Our analysis provides first-principles justification for the use of non-convex shrinkage
functions in spectral optimization. We also show that our algorithm asymptotically solves
a certain matrix optimization problem with non-convex regularizer. OptShrink has no
tuning parameters, so it can be safely integrated into any system that requires low-rank
matrix estimation. We validate our theoretical results with numerical simulations and
motivate future research on some related open problems.
This work was supported by an ONR Young Investigator Award N000141110660, an
AFOSR Young Investigator Award FA9550-12-1-0266, a NSF award CCF-1116115 and
an ARO MURI grant W911NF-11-1-0391.
210
Optimal fusion of multiple, noisy adjacency matrices for improving
community detection
Himanshu Nayar1, Raj Rao Nadakuditi1
1
Department of Electrical Engineering and Computer Science Department, University of Michigan, Ann
Arbor
We consider the problem of extracting common community structure from multiple noisy
adjacency multiple matrices. We derive an asymptotic expression for the optimal linear
combining coefficients that leverages analytical insights from Random Matrix Theory to
improve the probability of correct detection. We validate our results using simulations and
show that the fusion techniques developed can identify community structure even when
community structure cannot be reliably identified from any of the individual adjacency
matrices.
211
Energy Efficient Source Localization on a Manhattan Grid Wireless Sensor
Network
Matthew A. Prelee1 and David L. Neuhoff1
1
In the area of wireless sensor networks, several decentralized algorithms have been
developed to solve the problem of locating a source that emits acoustic or
electromagnetic waves, based solely on received signal strength. There are many
motivations for implementing decentralized algorithms, including the fact that they reduce
the number of transmissions between sensors, thereby prolonging sensor battery life.
Whereas most such algorithms are designed for arbitrary sensor placements, including
random placements, this work focuses specifically on applications that allow an a priori
choice of sensor placement. In particular, to ensure small communications cost, it is
proposed to place sensors uniformly along evenly spaced rows and columns, i.e., a
Manhattan grid. The Midpoint Algorithm is proposed for such a placement, which is a
simple noniterative decentralized algorithm. This work demonstrates that Manhattan grid
networks offer an improved accuracy vs. energy tradeoff over randomly distributed
networks. Results also show that the proposed Midpoint Algorithm offers a gain in energy
savings over the recent POCS algorithm.
This work was supported by NSF grant CCF 0830438.
212
Rapid Prediction of Image Noise Variance for 3DCT with Arbitrary
Trajectories
Stephen M. Schmitt1, Jeffrey A. Fessler1
1
Fast variance prediction for iteratively reconstructed helical CT images is useful for
analysis of resulting images and potentially for dynamic dose adjustment during a scan.
Previous methods require impractical computation times to generate an approximate map
of the image variance; other methods are able to approximate variance quickly but only
for specific CT geometries. We present an approximation to the local frequency response
of projection and back-projection for third-generation CT geometries. We also present an
application of this frequency response to predict the variance of iteratively reconstructed
helical CT images. Compared to the empirical variance derived from multiple simulated
reconstruction realizations, our method is accurate in most of an image to within 15%
while being computable for over 2000 voxels per second.
This work was supported in part by NIH grant R01 HL-098686.
213
The Performance of MUSIC-based DOA in White Noise with Missing Data
Raj Tejas Suryaprakash1 and Raj Rao Nadakuditi1
1
Multiple Signal Classification (MUSIC) is a widely used algorithm for estimating the
direction of arrival (DOA) of signals impinging on a sensor array. We analyze the
performance of MUSIC-like algorithms in the large array setting, where we have relatively
few signal-plus-white-noise snapshots, and where only a random, sample-independent
fraction of the data is observed. Using recent results from random matrix theory, we
obtain a closed-form, minimal stochastic representation for the DOA estimation error, that
captures how the performance depends on the number of sensors, number of snapshots,
Signal-to-Noise ratio (SNR) and the probability of observing an entry of the data matrix.
This minimal representation facilitates accurate computation of the DOA mean
squared error (MSE) and other desired statistics. Our analysis brings into sharp focus the
presence of a phase transition that separates a regime where MUSIC-based algorithms
accurately localize a source, from a regime where the source is present but the
algorithms fail. The critical phase transition threshold depends on the number of sensors,
the number of samples and the probability of observing an entry of the data matrix in a
simple manner that we make explicit. We validate our asymptotic theoretical predictions
with simulations.
214
Real-time Visual Scene Understanding for an Indoor Navigating Agent
Grace Tsai1, Benjamin Kuipers2
1
2
How can an indoor navigating agent with vision sensor learn about its local environment?
In this work, we present the Planar Semantic Model (PSM), a semantic geometric
representation for the local 3D indoor environment. The PSM is a coarse-grained
description of the indoor environment in terms of meaningful planes (the ground plane
and the walls), instead of a low-level fine-grained representation like a point cloud. The
PSM is capable of representing partial knowledge of the local environment so that
unknown areas can be incrementally built as observations become available.
We demonstrate an on-line method that efficiently constructs the PSM of the local
environment from a monocular camera, in real-time, without the need for prior training
data or the Manhattan-world assumption. Our method generates and evaluates a set of
qualitatively distinct PSM hypotheses and refines the parameters within each hypothesis
quantitatively. Our method is a continual, incremental process that transforms current
PSM hypotheses into children hypotheses describing the same environment in more
detail.
This work has taken place in the Intelligent Robotics Lab in the Computer Science and
Engineering Division of the University of Michigan. Research of the Intelligent Robotics
lab is supported by grants from the National Science Foundation.
215
Learning To Classify With Possible Sensor Failures
Tianpei Xie1, Nasser Nasrabadi2, Alfred O. Hero III1
1
2
Department of Electrical Engineering, systems, University of Michigan, Ann Arbor
US. Army Research Lab
Corruptions and sensor failure are inevitable in real signal processing systems and it is
well-known that the max-margin classifier, such as Support Vector Machine (SVM) is
sensitive to such anomalous events. In this project, we propose an efficient algorithm to
train a robust max-margin classifier when the corrupted measurements are present in the
training set. By incorporating a non-parametric prior based on the empirical distribution of
the training data, the proposed Geometric-Entropy-Minimization regularized Maximum
Entropy Discrimination (GEM-MED) method would perform classification and anomaly
detection in a joint manner. We demonstrate that our method can yield improved
performance over the conventional Ramp-loss-based classification methods in terms of
both classification and detection accuracy in simulated data set and real footstep data set.
Acknowledgement: the research in this paper was partially supported by ARO grant
WA11NF-11-1-103A1
216
Study of complex bilevel image quality
Yuanhao Zhai1, Prof. David Neuhoff1
1
Bilevel images are images with only two intensity levels: black and white. Different from
text, silhouettes and halftones, the bilevel image in which we are interested are complex
“scenic images”, which contain natural scenes, e.g. landscapes and portraits. Several
lossy coding algorithms have been developed to compress such images. Four of such are
studied in this project. Traditionally, percentage error is used as a metric to quantify the
fidelity of compressed bilevel images, which is equivalent to mean squared error (MSE) in
the bilevel case. However, this metric is not always consistent with human perception.
Some images with similar percentage error appear very different to viewers. To develop a
better metric to quantify bilevel image fidelity, the first step is needed to collect human
judgments about a series of bilevel images with different distortions.
This project includes two parts. The first part is a survey designed to collect human
judgments about different distorted bilevel images. The database images are formed
using all four existing compression methods with different compression qualities, together
with three manually added distortions: random flip, erosion and dilation. The results
provide the ground truth with which to compare different compression methods. The
second part of this project is to developing an objective bilevel image quality metric,
based on the ground truth obtained in part one. The new metric includes the features
using the concepts of adjusted percentage error, connected component and binary
gradient histogram and gives significantly better predictions of bilevel image quality than
percentage error.
217
Industrial and Operations
Engineering: Operations
Research
Session Chair: Greggory Schell
218
Mathematical Modeling of Pediatric Patients
Jason S. Card, BSE1, Alison D. Cator, MD, PhD3, Amy M. Cohn, PhD1, 2, 4, Joseph R.
East, BS1, Tara Lynn O’Gara, BSE1, Emily J. Burns1, Michelle L. Macy, MD, MS 3
1
Industrial & Operations Engineering, University of Michigan
School of Public Health, University of Michigan
3
Children’s Emergency Services, Department of Emergency Medicine, University of Michigan
4
Center for Healthcare Engineering and Patient Safety, University of Michigan
2
We use mathematical models and data analysis to observe how pediatric patients are
treated and discharged in the emergency department and inpatient units. We study
length-of-stay and other metrics for patients using different discharge methods. We
compare the results and discuss the implications of the findings.
Acknowledgements: This study was funded through support from the Center for
Healthcare Research and Transformation (CHRT), the University of Michigan Center for
Research on Learning and Teaching (CRLT), the Center for Healthcare Engineering and
Patient Safety (CHEPS), and the Bonder Foundation.
219
Improving Quality of Service and Fairness in Stochastic Operating Room
Planning
Yan Deng1, Siqian Shen1, Brian Denton1
1
Existing research on stochastic operating room (OR) planning rely on an expected-costbased approach, which penalizes under-performance and minimizes the total expected
cost. However, penalty costs are often difficult to estimate accurately. In this paper, we
formulate the problem as chance-constrained programs, where waiting and overtime are
limited by probabilities. Chance constraint provides a natural representation of Quality of
Service parameters. It also promotes fairness by accounting for individual surgeries and
ORs. We consider a set of surgeries with uncertain duration and a set of ORs with fixed
length of opening time, we decide (i) which ORs to open, (ii) surgery-to-OR allocation and
(iii) starting time of individual surgeries, to minimize OR opening cost. We formulate
chance constraints to capture the on-time-start guarantees for individual surgeries and
the on-time-closure target of the entire OR sector. We provide two alternative models
where surgeries are scheduled in continuous time and discrete time blocks respectively.
Via sampling, we reformulate chance constraints in each model as mixed-integer
programming (MIP) constraints based on finite realizations of uncertain surgery duration.
We also decompose the discrete-time MIP and develop cutting planes to improve the
computational efficiency. We test randomly generated instances based on real data from
a healthcare provider and develop insights of how our approaches improve the quality of
service and fairness in stochastic OR planning.
220
Modeling the Underlying Dynamics of the Spread of Crime
David McMillon1, Carl Simon2, Jeffrey Morenoff3
1
Applied & Interdisciplinary Mathematics, Industrial & Operations Engineering, University of Michigan
Mathematics & Public Policy, University of Michigan
3
Sociology, University of Michigan
2
The spread of crime is a complex, dynamic process that calls for a systems level
approach. Here, we build and analyze a series of dynamical systems models of the
spread of crime, imprisonment, and recidivism, using abstract transition parameters
based on empirical research on criminological dynamics. To find general patterns among
these parameters - patterns which are independent of the underlying particulars - we
compute analytic expressions for the tipping points between high-crime and low-crime
equilibria using Lyapunov functions.
We examine, among other relationships, the effects of longer prison terms and of
increased incarceration rates on the long-term prevalence of crime, with a follow-up
analysis of the “Three-Strike Policy.”
221
When Is Bone Scan Needed For The Baseline Staging Of Newly Diagnosed
Prostate Cancer?
Selin Merdan1, David C. Miller2,3, MD, MPH, Christine Barnett1, MEng, James E.
Montie2,3, MD, Zaojun Ye2,3, MS, Susan Linsell3, MSHA, Brian T. Denton1, Ph.D.
1
Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
Department of Urology, University of Michigan, Ann Arbor, MI, 48109, USA
3
Michigan Urological Surgery Improvement Collaborative, Ann Arbor, MI, 48109, USA
2
Bone scans are often performed in the staging evaluation of patients with newly
diagnosed prostate cancer (PCa). The most important aspect of staging is the detection
of bone metastasis (BM). Considering that the skeleton is the most painful and debilitating
site of metastasis from PCa, an accurate staging is of crucial importance for treatment
choice as well as for patient diagnosis. Bone scan (BS) is the most widely accepted
method for evaluating the entire skeleton for evidence of metastatic PCa; however it is
also an expensive and time-consuming staging modality. Moreover, patients vary widely
in risk of harboring BM at diagnosis. This may translate into a high number of patients for
whom staging BS can be safely avoided with a significant reduction in financial burden on
the healthcare system and reduced anxiety for patients. Recently, several international
guidelines have been published addressing the need to reduce the unnecessary use of
BS in low risk patients; however, no consensus currently exists regarding the use of
imaging for evaluating primary PCa. This poster will present a study using statistical
methods to evaluate the ability of clinical and pathological variables in predicting positive
BS among a large sample of PCa patients from community and academic practices. We
used the statistical model to identify subgroup of patients for whom staging BS could be
safely eliminated due to low probability of BM. Furthermore, the performance
characteristics of the published guidelines are evaluated in terms of sensitivity and
specificity by adjusting for verification bias.
This material is based in part upon work supported by the National Science Foundation
(NSF) under Grant Number CMMI 0969885. Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the authors and do not
necessarily reflect the views of the NSF.
222
Using Stochastic Programming and Discrete Event Simulation to Improve
Service Quality in an Outpatient Infusion Center
Spyridon Potiris1, Autumn Heiney2, Jeremy Castaing1, Amy Cohn1, Brian Denton1,
Christopher Friese2
1
2
School of Nursing, University of Michigan
Background: Demand for outpatient chemotherapy delivery is rising, resulting in high
patient volumes at infusion centers. Reduction in patient wait times can help address this
challenge. Operations research techniques such as discrete event simulation and
stochastic programming can inform more efficient patient scheduling. Methods: First, 60
hours of observation in the UMHS Comprehensive Cancer Center's outpatient infusion
center contributed in mapping patient flow. Then, a computer simulation model was
created to examine the effects on patient wait times and total hours of operation under
different scheduling paradigms. 9 months of data from the electronic medical record and
scheduling systems were used as input for the simulation model. To create different
appointment schedules, both simple heuristics and a more complex stochastic
programming model were developed. The aforementioned scheduling methods explicitly
consider the variability in infusion times. Results: The baseline average patient wait time
was 130.48 minutes (95% CI 122.38-138.68). Computer simulation results show that
schedules generated by the stochastic programming model perform better than baseline
and simple heuristics, reaching a 70% reduction in waiting times. Schedules that
allocated patients with longer infusion times to earlier appointments resulted in both
reduced average patient wait times and total hours of operation. Conclusions: Based on
our results from the computer simulation model, scheduling patients with longer infusion
times earlier in the day results in shorter patient waiting times and total length of day of
operations. Next steps include development of a simple heuristic to support appointment
scheduling that conforms to the optimal appointment schedule.
Acknowledgements
The Seth Bonder Foundation, the TDC Foundation, and Center for Healthcare
Engineering and Patient Safety (CHEPS), University of Michigan
223
Scheduling Residents to Achieve Adequate Training on Procedures with
Random Occurrences
William Pozehl1, Ryan Chen1, Amy Cohn1, Mark Daskin1, Rishi Reddy2, Jake Seagull3
1
Department of Surgery, University of Michigan Health System
3
Department of Medical Education, University of Michigan Medical School
2
Surgical residents must accrue a certain minimum number of case experiences on a
variety of procedures (e.g., heart transplants) to receive certification. These residents
work a rotating call schedule to cover unplanned, emergency cases that occur randomly.
Due to the coupling of unplanned events with fixed schedules, not all residents will
necessarily accrue enough case experiences even with a sufficient total number of cases.
We analyze the current system to identify alternative methods by which residents can
achieve certification more reliably. We develop a simulation model of this problem and
outline alternative scheduling rules that increase the number of residents who can be
certified in a graphical tool developed in Visual Basic. The simulation tool also has some
degree of customizability; the user can stipulate such factors as: how to assign multiple
procedures in one day, how the residents’ call schedule works, how seasonality affects
procedure occurrences, etc. These statistics can be displayed for one repetition or can be
aggregated over multiple repetitions. In addition, the simulation tool has a feature which
calculates the probabilities of all residents receiving sufficient case experiences for
certification as a function of the mean number of procedures performed per year. Our
results demonstrate that the likelihood of certifying all residents training for heart and lung
transplant certification in an average year at the University of Michigan Health System is
exceedingly low. Medical personnel may use the tool to conceptually and visually
understand the effects of randomness on the ability to train residents effectively.
We would like to thank the Seth Bonder Foundation, The Doctors Company Foundation,
and the Center for Healthcare Engineering and Patient Safety for funding this project.
224
Transmission Expansion Planning with Demand and
Uncertainty and Transmission Switching as Recovery Action
Contingency
Kathryn Schumacher1, Richard Li-Yang Chen2, Amy E.M. Cohn1
1
2
Quantitative Modeling and Analysis, Sandia National Laboratories
One of the major challenges in deciding where to build new transmission lines is that
there is uncertainty regarding future loads, levels of renewable penetration and equipment
failures. We propose a robust optimization model whose transmission expansion
solutions ensure that demand can be met over a wide range of conditions. Specifically,
we require feasible operation for all loads and renewable generation levels within given
ranges, and for all single transmission line failures. Furthermore, we consider
transmission switching as an allowable recovery action. This relatively inexpensive
method of redirecting power flows improves the network’s resiliency, but introduces
computational challenges. We present a novel algorithm to solve this model.
Computational results will be discussed.
225
Optimization Models for Differentiating Quality of Service Levels in
Probabilistic Network Capacity Design Problems
Siqian Shen1, Zhihao Chen1
1
This paper focuses on various forms of chance-constrained models for the probabilistic
network design problem (PNDP), where given uncertain demand we aim to differentiate
the quality of service (QoS) and measure the related network performance. The upper
level problem of the PNDP designs continuous/discrete link capacities shared by multicommodity flows, while the lower level problem ensures a certain level of demand
satisfaction via recourse. The differentiated QoS adjusts the feasible region for given
prioritized customers and/or commodities. We consider PNDP variants that have either
fixed flows (formulated at the upper level) or recourse flows (at the lower level) according
to different applications. We transform each probabilistic model as a mixed-integer
program, and derive polynomial-time algorithms for special cases with single-row chance
constraints. The paper formulates benchmark stochastic programming models by either
enforcing to meet all demand or penalizing unmet demand via a linear cost function. We
compare different models and approaches by testing randomly generated diverse
networks and an instance given by the Sioux-Falls network. We analyze the numerical
results to demonstrate the effectiveness of our models, and to derive managerial insights.
226
Using Monte Carlo Simulation to Conduct Sensitivity Analysis on Markov
Chains
Haipeng Wu1; Yuanhui Zhang2; Brian T. Denton1; James R. Wilson3
1
Graduate Program in Operations Research, North Carolina State University
3
Edward P. Fitts Department of Industrial and Systems Engineering, North Carolina State University
2
Markov chain (MC) models are commonly used in medical decision making. Since
transition probabilities are usually estimated using sample data or conflicting subjective
information, they are subject to uncertainty. However, methods for conducting sensitivity
analysis on the transition probability matrix (TPM) of an MC have not been widely
adopted. We describe two simulation-based methods for performing sensitivity analysis
on MCs with uncertain TPMs. Given an initial estimate of the TPM, method 1 samples the
TPM’s rows independently. Assuming no prior knowledge of the TPM’s distribution,
method 1 samples the TPM uniformly in a user-specified uncertainty set whose reference
point is the initial TPM estimate. Method 2 generates an initial sample from the estimated
multi-normal distribution of the TPM’s maximum likelihood estimator; then taking that TPM
as the uncertainty set’s reference point, we generate the final TPM uniformly in the
uncertainty set by method 1. We use both methods for performance evaluation of
published treatment guidelines for glycemic control of type 2 diabetes patients, where an
MC models the natural variation in Glycosylated hemoglobin (HbA 1c). We report the
variation in expected quality-adjusted life span and medication cost due to uncertainty in
the associated TPM. We also compare the computation times for methods 1 and 2.
Acknowledgement: This material is based in part upon work supported by the National
Science Foundation (NSF) under Grant Number CMMI 0969885. Any opinions, findings,
and conclusions or recommendations expressed in this material are those of the authors
and do not necessarily reflect the views of the NSF.
227
Incorporating Functionality into Radiation Therapy Treatment Planning
Optimization
Victor Wu1, Marina Epelman1, Mary Feng2, Troy Long1, Martha Matuszak2, Edwin
Romeijn1
1
2
Radiation Oncology, University of Michigan Health System
Conventional Radiation Therapy Treatment Planning (RTTP) has the goals of (i)
maximizing dose to eradicate the tumor and (ii) minimizing dose to preserve critical
structures. Although post-treatment functionality of critical structures is a main clinical
concern, current RTTP optimization models do not explicitly consider functionality. In liver
cancer cases, dynamic contrast enhanced magnetic resonance imaging (DCE-MRI)
provides perfusion maps that have been shown to be a good indicator of tissue function
both locally and globally [Cao 2013]. We propose a model that explicitly incorporates
functionality metrics obtained from perfusion maps with the goal of redistributing dose
through lower-functioning areas while achieving conventional treatment planning goals.
We use liver cancer cases to compare treatment plans with and without using
functionality information. Initial results indicate redistribution of dose while satisfying
clinically used metrics. Future steps in model development include incorporating
uncertainty of functionality information from image registration (“matching”) of DCE-MRI
(for perfusion maps) with CT (for patient geometry maps).
This project is funded by MCubed.
228
Industrial and Operations
Engineering: Ergonomics
Session Chair: Greggory Schell
229
Development of a Next-Gen Hand Model
Rosemarie Figueroa1, Thomas Armstrong PhD 1, Mark Palmer PhD2
1
2
Department of Industrial and Operations Engineering, The University of Michigan
School of Kinesiology, The University of Michigan
Hands are the primary means by which we exercise control over objects in our
environment. In industry, proper design of workspace and tools, considering hand
properties and population variability, is necessary for proactive prevention of hand acute
and chronic injuries. To fully understanding the relationship between exposure and
development of work-related musculoskeletal disorders, objective measurements to
quantify physical risk factors (e.g. human models) are needed. The main goal of this
project is to collect new knowledge to develop a scalable 3D biomechanical hand model.
This model could be used to determine required hand forces and postures so that risk
factors can be identified and controlled. CT-Scans, of a hand in different poses (e.g. “FHflat hand”, “LP-lateral pinch”) were used to create 3D quantitative images. Bones of FH
and LP poses were used to estimate anatomical joint centers, bone distances and to
create representative vectors of each bone. Spheres were fitted to proximal and distal
ends of four phalanges. The center of these spheres corresponded to the joints
instantaneous centers of rotation (COR). The distal COR was linked to the distal COR for
the previous bone to create a representative finger vector. On average, representative
vector length from “flat hand” and “lateral pinch” poses varies by 12% showing that
movement changes the location of COR, and thus, having vector lengths that vary with
hand posture is essential. To validate the segmentation process hand key dimensions
such as hand length, index finger length, hand breath and index finger breath will be
analyzed.
230
Vessel Diameter Mismatch in Microsurgical Free Flap Transfer and Methods
for Rectification
C. Green1, D. Yu1, R. Minter 2, A. Frischknecht3, S. Kasten2, T. Armstrong1
1
Center for Ergonomics, University of Michigan
Department of Surgery, University of Michigan
3
College of Human Medicine, Michigan State University
2
Microvascular anastomosis is an integral aspect of free flap transfer surgery. When a
tumor is excised from a patient, the blood vessel network is also removed. To restore
blood flow to the impacted area, a pedicle containing blood vessels may be extracted
from another body region such as the anterolateral thigh. However, since the vessels
being anastomosed generally serve different physiological purposes, the vessel
diameters may significantly differ. If this diameter disparity is not surgically rectified,
medical complications may arise. Numerous methods have been created to rectify the
disparity, including altering anastomotic geometry, physically altering the vessels and
introducing tools to alter vessel diameter. To determine if these methods were present
and how they altered surgical patency at varying levels of vessel diameter mismatch, 68
free flap transfers performed on 63 patients at the University of Michigan were analyzed.
This study determined that two of the three aforementioned methods were utilized. The
anastomotic geometry was altered by creating an end-to-side anastomosis and a
mechanical coupler was utilized to anastomose vessels. Vessel alteration methods such
as oblique cutting and fish mouth incisions were not witnessed. No clear pattern emerged
when the surgical patency rates for the observed techniques were compared against the
level of diameter mismatch. For end-to-side anastomoses, at a mismatch less than
double, the complication rate was 100%, however when the mismatch was more than
double, the complication rate was 14.3%. These results may have occurred due to postoperative data collection timing or the relatively minor diameter disparities present.
This work was financially supported, in part, through the Graduate Medical Education
Innovations Program through the University of Michigan Health System.
231
How drivers react with their hands or feet in intersection crashes?
Heejin Jeong1 and Paul Green1, 2
1
2
Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor
Driver Interface Group, University of Michigan Transportation Research Institute
According to the National Motor Vehicle Crash Causation Survey report of 2008, 36% of
roadway crashes occurred when turning or crossing at intersections. Given this
frequency, driving behavior at particularly crash-prevalent intersections should be
investigated, including: Straight Crossing Path (SCP, 30%), Left Turn Across-Path Lateral
Direction (LTAP/LD, 28%), and LTAP-Opposite Direction (LTAP/OD, 20%) crashes. To
understand how people drive in these situations, some 24 drivers drove through 70
intersections in a driving simulator, 10 of which involved conflicts. While driving, their
steering wheel angle, accelerator position, and brake pedal position were recorded, as
well as speed and lane position to determine how drivers reacted to each crash scenario.
In SCP, RTIP, and LTIP scenarios, older subjects (over age 65) actively steered more
often than young subjects (ages 18-30). In SCP scenarios, male drivers were more likely
to use foot controls than female drivers. The next step in the analysis is to develop
quantitative predictions of how drivers respond in each of the situations and then to
develop predictions of how those responses will change when various types of warning
systems to reduce those crashes are introduced. Those predictions will be validated in a
follow-on experiment. This research was supported by a grant provided by the National
Science Foundation.
232
Effects of Primary Flight Display Clutter: Evidence from Performance and
Eye Tracking Measures
Nadine Moacdieh1, Julie Prinet1, and Nadine Sarter1
1
There is an ever-growing increase in the amount of information needed and available to
operators in complex environments. One example of this trend is modern primary flight
displays (PFD), many of which now include weather, terrain, and navigation data. The
addition of more information to already busy displays has raised concerns about display
clutter. In this study, our goal was to investigate the performance and attentional costs
associated with PFD clutter during a simulated flight and to determine to what extent
pilots are aware of clutter and its effects. Low, medium, and high-clutter PFDs were
developed, and pilots flew a simulated flight scenario containing periods of high and low
workload using one of the three PFDs. Pilots were asked to detect different visual alerts
and notifications that appeared on the PFD throughout the flight. Performance, eye
tracking, and subjective measures were recorded. Clutter significantly increased the
response time to alerts, and high workload resulted in more alerts being missed. The eye
tracking data provided insight into pilots’ monitoring strategies and efficiency in the
different clutter conditions. Spatial density and the number of transitions were found to be
larger in the case of higher clutter, whereas the number of fixations on flight mode
annunciators was higher in the low-clutter condition. Importantly, pilots rated clutter as
being relatively low even in the high-clutter condition. In combination, these results
suggest that pilots may benefit from real-time clutter detection and reduction techniques
that are based on eye tracking metrics.
This research was supported, in part, by a research grant from the Federal Aviation
Administration (10-G-022; technical monitors: Dr. Tom McCloy and Colleen Donovan).
We would also like to thank Joseph Phillips, Khevna Shah, Noah Klugman, Brian
Anthony, and Michael Stengel.
233
Cross-modal matching: Towards the development of a novel technique
Brandon Pitts1, Sara Lu1, and Nadine Sarter1
1
Department of Industrial and Operations Engineering, University of Michigan – Ann Arbor
Research in the area of multimodal displays and information processing has reported
several benefits of distributing information across multiple sensory channels (vision,
audition, and touch, in particular). However, with few exceptions, studies on multimodal
information processing involve the potential risk of confounding modality with other
factors, such as salience, because no cross-modal matching is being performed prior to
experiments. To date, no agreed-upon cross-modal matching method has been
developed. The goal of our research is to develop and compare the feasibility and validity
of various approaches. In this poster session, we present the findings for one particular
technique that employs cue adjustments and bidirectional matches. Six participants were
asked to perform a series of 216 matching tasks for combinations of cues in vision,
audition and touch. The results show that participants’ matches differed from one another,
were inconsistent across trials, and were also a function of the intensity level of the initial
cue. The findings from this research further highlight the need for careful matching of
multimodal cues in research on multisensory information processing and will result in
refinements of the proposed technique.
The authors would like to acknowledge the National Science Foundation Graduate
Research Fellowship Program (NSF GRFP), Noah Klugman, Christie Rockwell, and
Katherine Lu for helping to conduct and support this research.
234
Technique variations among different surgeons and conditions: Using a
hierarchical taxonomy to describe techniques that impact outcomes
Denny Yu1, Adam Frischknecht2, Steven J. Kasten2, Rebecca Minter2, Thomas J.
Armstrong1
1
2
Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, MI
Department of Surgery, University of Michigan, Ann Arbor, MI
Standardization of surgical procedures on best methods can improve patient outcomes
and reduce the time and cost. A hierarchical taxonomy is proposed for describing the
variability in surgical technique to identify best methods. Hierarchical task analysis (HTA)
was performed on eight “microvascular anastomosis” cases. It was found that the
analyses could be simplified by redefining subtasks and elements to only describe actions
and adding attributes to describe the work object, method, tool, material, conditions, and
ergonomics factors. The resulting taxonomy was used to describe 64 cases. Differences
were found among cases for the frequency and duration of subtask, elements, attributes,
and element sequences. Observed variations were used to formulate hypotheses about
the relationship between different methods and outcomes that can be tested in future
studies. The taxonomy can provide a framework to define best practices both within and
across operations, and for teaching surgical trainees and assessing performance.
The authors would like to acknowledgement all the surgical team members that
participated in this study. This work was financially supported, in part, by the Graduate
Medical Education Innovations Program through the university health systems and by the
National Science Foundation.
235
Materials Science and
Engineering: Materials for
Energy-Conversion and
Storage
Session Chair: Sung Joo Kim
236
Synthesis and Characterization of Cu(4-x)Li(x)S2 (x = 1, 2, 3)
Erica Chen1 and Pierre F. P. Poudeu1
1
Laboratory for Emerging Energy and Electronic Materials, Materials Science and Engineering Department
University of Michigan, Ann Arbor, 48109, USA
Li(4-x)Cu(x)S2 (x = 0, 1, 2) were synthesized using conventional solid-state reaction in a
tube furnace, annealed mechanical alloying, and induction melting. The products of these
reactions were structurally characterized using powder X-ray diffraction (XRD).
Differential scanning calorimetry (DSC) was used to investigate possible phase transitions
in the synthesized compounds between room temperature and 1000°C. Laser flash
method was used to determine the thermal conductivity of the compounds. Lastly, cyclic
voltammograms (CV) were obtained to locate the redox peaks in each composition (xvalue). Capacities were also calculated based upon the CV data.
This work has been supported by ACS-PRF Grant # 52761-ND 10. Special thanks to
TimCal and Arkema for generously providing Super P 45 carbon black and HSV761A
PVDF respectively. Thank you to Poudeu Lab members for helpful discussion and insight.
237
The effect of capping chemistry on GaSb Quantum Dot shape and
photoluminescence.
Matt DeJarld,1 M. Luengo-Kovac2, E. Smakman3, P. Koenraad,3 V. Shih2,
J.M.Millunchick1
1
Department of Materials Science, University of Michigan, Ann Arbor, MI.
Department of Physics, University of Michigan, Ann Arbor, MI.
3
Eindhoven University, Applied Physics, Netherlands
2
The formation of quantum dots by droplet epitaxy has been studied with consistent
success for the GaAs system, but the underlying mechanisms have not been confirmed
and the use of heavier group V elements as Sb is not well characterized. When capped
with GaAs, GaSb will disintegrate into clusters and islands of various sizes. This
phenomenon has been observed in cross sectional STM and can degrade device
performance in next generation devices by induce band broadening. An examination of
GaSb quantum dot evolution indicates that upon reaching the critical thickness, some of
the quantum dot can incorporate into the adjacent wetting layer upon dissolution. To
better understand quantum dot disintegration, GaSb quantum dots grown on GaAs were
capped with four different compounds, 50nm of GaAs, one monolayer of AlAs with 50nm
of GaAs, three monolayers of AlAs with 50nm of GaAs, and 20nm of Al 0.5Ga0.5As. From
cross sectional STM data, the AlAs and Al0.5Ga0.5As capping layers significantly retained
the quantum dot shape, with only 20% of the dots being demolished with the Al 0.5Ga0.5As
capping as opposed to 60% of the dots capped with just GaAs. Additionally, the PL peaks
for the quantum dots were significantly more pronounced in the Al 0.5Ga0.5As and three
monolayer AlAs samples. However, the overall intensity decreases with more compact
dots, which may signify an increased density of defects.
This work was supported as part of the Center for Solar and Thermal Energy Conversion,
an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of
Science, Basic Energy Sciences under Award #DE-SC0000957.
238
A Model for Anodic Film Growth on Aluminum Coupling Bulk Transport and
Interfacial Reactions
Stephen DeWitt1 and Katusyo Thornton1,2
1
2
Department of Applied Physics, University of Michigan – Ann Arbor
Department of Materials Science and Engineering, University of Michigan – Ann Arbor
Anodization is an electrochemical method to grow oxide films on metallic substrates that
can either be nanostructured (e.g. nanoporous) or compact. Anodic films have a wide
range of applications that include nano-templates, capacitors, solar cells, batteries,
biomedical devices, sensors, and anti-corrosion finishes. However, the mechanisms
underlying anodic growth are not fully understood. To provide improved understanding of
these growth mechanisms, we present a new continuum model and one-dimensional
simulations for anodic film growth incorporating high-field ionic conduction, Butler-Volmer
reaction kinetics, and space charge within the film. We demonstrate that the simulated
results reproduce experimental trends for the Al3+ ejection current, transient responses,
and embedded surface charge in compact films as well as equilibrium pore-base
thickness and growth velocity in nanoporous films. We also discuss the application of this
model to multi-dimensional simulations of anodic nanopore growth and self-organization.
Support for this work was provided by the U.S. Department of Energy under contract
numbers DE-AC05-06OR23100, DE-FOA-0000559, and DE-SC0000957.
239
Design principle of molecular doping for enhanced thermoelectric efficiency
G. H. Kim1, L. Shao1, K. Zhang1, and K. P. Pipe1,2
1
2
Organic semiconductors (OSCs) provide advantages over inorganic semiconductors
(ISCs) such as low cost, mechanical flexibility, and large-area deposition. For
thermoelectric applications, OSCs further offer low thermal conductivity. Carrier transport
mechanisms in OSCs differ from those in ISCs, leading to different tradeoffs in Seebeck
coefficient, electrical conductivity, and thermal conductivity (e.g., OSCs do not typically
obey the Wiedemann–Franz law).
Doping plays a critical role in optimizing the thermoelectric power factor (S2 ), since it
dictates both free carrier concentration and carrier mobility (µ). For OSCs, which typically
have low S2 , the presence of dopants can affect µ significantly by increasing the
distance between weakly bonded molecules and thereby the length over which carriers
must hop. Furthermore, weak bonding in OSCs leads to a small dopant ionization fraction
(i.e., a small number of free carriers per dopant); achieving a given carrier concentration
therefore requires a relatively large total dopant volume. We show that the volume
associated with a large number of unionized dopants in an OSC exponentially decreases
the hopping rate and consequently S2 . Therefore, reducing the number of unionized
dopants is crucial to maximizing ZT in OSCs.
We develop a model for thermoelectric transport parameters that includes the effects of
dopant volume, and experimentally demonstrate the importance of reducing total dopant
volume by dedoping non-ionized poly(styrenesulfonate) (PSS) dopants from poly(3,4ethylenedioxythiophene) (PEDOT). We find that this dedoping causes all three
parameters that compose ZT to vary in a manner so that ZT is increased, yielding ZT =
0.42 at room temperature.1
[1] G.-H. Kim, L. Shao, K. Zhang, and K. P. Pipe, Engineered doping of organic
semiconductors for enhanced thermoelectric efficiency, Nature Mater. 12, 719 (2013).
240
Tailoring the morphology and performance of bulk heterojunction organic
photovoltaics using conjugated copolymers
Anton Li1, Jojo Amonoo2, Bingyuan Huang1, Ed Palermo3, Peter Goldberg3, Anne
McNeil3, Peter Green1,2
1
Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48109
Department of Applied Physics Program, University of Michigan, Ann Arbor, MI 48109
3
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
2
Thin film organic photovoltaics hold great potential, but further progress largely hinges
upon understanding nano-scale structure-property relationships, and being able to
manipulate them through molecular design and materials processing. To this end, we
have synthesized and characterized novel fully-conjugated copolymers and investigate
ways to exploit their unique behavior to tailor the morphology and properties of solar cell
devices. This study focuses on the effects of incorporating the random copolymer poly((3hexylthiophene)-r-(3-((hexyloxyl)methyl)thiophene)) (P(3HT-r-3HOMT)) into a blend of
P3HT homopolymer and indene-C60 bisadduct (ICBA). The structure and properties of the
active layer thin film were characterized using UV-visible spectroscopy, conductive atomic
force microscopy (c-AFM), and energy-filtered transmission electron microscopy
(EFTEM). Along with bulk current-voltage device measurements, charge carrier dynamics
were studied using photo-induced charge extraction with a linearly increasing voltage
(photo-CELIV). Using this combination of techniques, was found adding a small fraction of
P(3HT-r-3HOMT) to the baseline P3HT:ICBA blend generated an improved microphaseseparated morphology, leading to reduced charge recombination and yielding a 20%
improvement in device efficiency. Ongoing work on copolymers of other chemistries and
architectures are uncovering different types of morphologies with correspondingly
different device characteristics. These findings provide insights on designing polymers
and processing protocols to produce devices with appropriate nanostructure and
properties for optimal light harvesting and energy conversion.
This work was funded as part of the Center for Thermal and Solar Energy Conversion, an
Energy Frontiers Research Center supported by the U.S. Department of Energy, Office of
Science, Basic Energy Sciences under Award #DE-SC-0000957. We also thank Jonas
Locke for his work on copolymer synthesis.
241
Tuning the HOMO-LUMO Gap in Conjugated Polymers for Organic
Photovoltaics Applications based on First-Principles Calculations
Xiao Ma1, Hossein Hashemi1, Bong Gi Kim1, Jinsang Kim1, and John Kieffer1
1
Department of Materials Science and Engineering, University of Michigan, Ann Arbor
To tune the HOMO and LUMO energy levels via alternating donor-acceptor monomer
units, we investigated a series of conjugated polymers (CP)s in which the electron
withdrawing power of the acceptor group and the electron giving power of the donor
group is varied, while maintaining the same conjugated chain conformation. We observed
that the introduction of electron withdrawing groups lowers the LUMO level, while keeping
the HOMO level almost unchanged. Conversely, inserting the electron donating groups
raises the HOMO level while maintaining the LUMO level unchanged. According to these
trends, designing a low band gap polymer requires strong donors and acceptors. Using
first-principles calculations we investigated underlying reason. Charge localization on the
electron-rich and electron-poor segments in CPs plays a key role. We identified strong
correlations between the withdrawing strength of the acceptor group, the HOMO and
LUMO levels, and the degree of orbital localization, which allows us to derive reliable
design principles for CPs.
242
Incorporation Kinetics and Bi Surfactant Growth in Mixed Anion Compound
Semiconductor Alloys
Joanna M Millunchick1, Evan M Anderson1, Chris Pearson2, Wendy L. Sarney3, Stefan P.
Svensson3
1
Department of Materials Science and Engineering, University of Michigan-Ann Arbor
Department of Computer Science, Engineering, and Physics, University of Michigan-Flint
3
Army Research Laboratory
2
We present a kinetic model predicting the behavior of anion incorporation in InAsSb.
Included are the effects of As desorption, Sb segregation, and Sb displacement by As,
which may be limited by the In flux if it is comparatively larger. The model captures
experimental data over a range of growth conditions for the InAsSb system using
activation energies for desorption and Sb segregation found in literature. The activation
energy for Sb displacement is 1.22eV. This model is general and should be valid for other
mixed anion systems, or, appropriately modified, mixed cation systems and mixed
anion/cation systems such as AlInAsSb. Additional experiments have been performed
using Bi as a surfactant, resulting in a decrease in Sb incorporation with increasing Bi flux
and constant In, As, and Sb fluxes.
JMM, EMA, and CP gratefully acknowledge Chakrapani Varanasi and the support of the
Department of Defense, Army Research Office via the grant number W911NF-12-1-0338.
We also acknowledge Adam Lundquist for acquiring XRD and AFM data.
243
Structure and Electrical Properties of Stoichiometric CuxAgySe2 Synthesized
via Redox Solid State Phase Transformations
Alan Olvera1, Pierre Ferdinand Poudeu Poudeu1
1
Department of Material Science & Engineering, University of Michigan
Silver chalcogenides have regained attention over the past decade because of their
multiple temperature dependent structural phase transitions, which generally induce
interesting changes in electronic transport properties. These structural transitions have
been reported previously in the Cu2Se, Ag2Se, Ag2S, and Ag2SeS systems, where
significant increase in the electrical conductivity and large decrease in the lattice thermal
conductivity are generally observed due to the ‘liquid-like’ disordered state of the metal
ions within the rigid lattice formed by the chalcogen atoms. Here we report a new
approach for an energy efficient synthesis of novel stoichiometric ternary phases with
general formula CuxAgySe2 (1 x, y  3) in the Ag-Cu-Se system. The compounds
Cu3AgSe2, CuAg3Se2, and Cu2Ag2Se2 were synthesized by solid-state transformation of
CuSe2 via mechanical alloying using the corresponding amount of Cu and/or Ag metal
powders. X-ray diffraction study on a single crystal of CuAg3Se2 at 100K revealed that the
compound crystallizes in the monoclinic space group C2/m with lattice parameters a =
9.8720 Å, b = 18.0780 Å, c = 5.3091 Å,  = 105.13, Z = 8 and adopts a new structure
type. In the structure, two corrugated chains of corner-sharing [(Cu/Ag)Se4] tetrahedra
further share corners to form a one-dimensional ribbon, which stitches adjacent layers of
edge-sharing [AgSe6] octahedra and [AgSe8] bicapped trigonal prisms. The large void left
by this packing arrangement is occupied by a linearly coordinated Cu atom. The thermal
behavior of the Cu3AgSe2, CuAg3Se2, and Cu2Ag2Se2 phases and their potential as
thermoelectric materials will be discussed.
244
Molecular Dynamics Study of Heat Transfer at CuPc-metal Interfaces
Chen Shao1, Yansha Jin1, Max Shtein1, Kevin Pipe2, and John Kieffer1
1
2
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
We use classical molecular dynamics (MD) simulations to carry out a systematic study of
the nanoscale processes that govern the thermal boundary resistance at copper
phthalocyanine (CuPc)/metal interfaces. Non-equilibrium MD simulations (NEMD) are
performed on metal–CuPc–metal junctions to study thermal energy transport across the
interfaces through the Müller-Plathe method. The interfacial bonding strength is
controlled directly in the MD simulation by scaling the interaction parameters for the
materials juxtaposed at the interface. The thermal boundary resistance is closely related
to the interfacial bonding strength. By comparing the MD calculation results with the
experimental measurements, the work of adhesion between CuPc and metal substrates is
estimated to be 0.06 J/m2 for CuPc/Au, 0.04 J/m2 for CuPc/Ag, and 0.4 J/m2 for CuPc/Al
interfaces. These findings confirm the experimental observation of very weak bonding
between CuPc and Au or Ag and strong bonding at the CuPc/Al interface. Our study
shows that the interfacial bonding strength is a very important factor in predicting thermal
boundary resistance at CuPc/metal interface. Conversely, the acoustic impedance
mismatch between the adjoining materials appears to be less important. To further
investigate the mechanisms of interfacial heat transfer we carry out a detailed analysis of
the momentum exchange across the interface, based on incoherent space-time
correlation functions of the atomic motion and their spectral representations. Our results
suggest that the anharmonic contributions to the phonon spectrum directly correlate with
the thermal boundary resistance at the CuPc-metal interface.
245
Characterization of Magnesium Rare Earth Precipitates
Ellen Sitzmann1, John Allison1, Emmanuelle Marquis1
1
Magnesium is the lightest of all the commonly used structural metals today, with a density
about two thirds that of aluminum and one fourth that of steels. Due to the significant
weight savings, magnesium alloys have become of great interest to automotive
industries. Although magnesium is an abundant material, the yield strength, creepresistance, formability, and corrosion resistance of cost-effective magnesium alloys are
insufficient for use in engineering applications. To increase the strength of magnesium
alloys, solid-state precipitates are formed by an age hardening heat treatment. Typically,
magnesium alloys that do not contain rare earth elements are relatively weak structural
materials because the precipitates form parallel to the crystallographic basal planes. Mg
alloyed with Nd, Y, and/or Gd, on the other hand, form precipitates on prismatic planes of
the magnesium matrix phase, providing a more effective barrier to dislocation motion.
However, rare earth elements tend to be expensive, motivating the design of alternative
alloy compositions with comparable mechanical properties.
The mechanisms of
precipitation in Mg-RE alloys are not fully understood and the nature of the precipitate
phases remains matter of debate. Therefore, the objective of this project is to first
understand the thermodynamic and kinetic mechanisms that control the complex
precipitation sequence in Mg-Nd, Mg-Nd-Y, and Mg-Nd-Zr alloys. The evolution of
precipitates (nucleation, growth, and coarsening of each phase) is systematically
characterized as a function of aging conditions using transmission electron microscopy
and atom probe tomography.
Acknowledgements: PRedictive Integrated Structural Materials Science (PRISMS) UMDOE Software Innovation Center for Integrated Multi-Scale Modeling of Structural Metals
Funding provided by DOE-BES contract DE-SC0008637.
246
Reversible Pt Nanoparticle Formation in Pt-doped BaCeO3 and Related
Application
S.Y. Zhang1, X.F. Du1, M. H. Fang1, M.B. Katz1, G. W. Graham1 and X.Q. Pan1
1
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Engineered nanocomposites are of considerable interest for potential application in areas
such as photonics, catalysts and thermoelectrics [1-3]. In this work, we report a reversible
process of Pt nanoparticle formation in Pt-doped BaCeO3, a phenomenon that may be
exploited to create and control engineered nanocomposites. Both ex-situ and in-situ
reactions have been studied through scanning transmission electron microscope. An
application of this phenomenon, to lower the thermal conductivity of oxide materials,
whose potential in thermoelectrics has been inhibited by their relatively high thermal
conductivities, is presented as an example.
The thin films of BaCeO3 (BCO), doped with 5% Pt, were grown by pulsed laser
deposition (PLD) on (001) MgO substrates. Pt dopants presumed to occupy B sites of the
perovskite matrix in the as grown film. After 1 hour’s reduction at 800 °C in 10% H2
balanced with N2, Pt nanoparticles, were expelled from the perovskite lattice, appearing
uniformly dispersed throughout the film, at grain boundaries, and on the free surface. The
reduced film was then subjected to an oxidation treatment in dry air at 800 °C for one
hour. Almost all the Pt particles, including those as large as 7-8 nm, disappeared, having
completely dissolved back into the perovskite lattice, and the system itself has essentially
returned to the initial, as-grown state. We next conducted a second reduction treatment
on the oxidized film, again at 800 °C for 1 hour, and found that Pt particles were again
expelled, but now exhibiting a more uniform size and spatial distribution.
The authors gratefully acknowledge funding from Ford Motor Company under a
University Research Proposal grant and the National Science Foundation under grants
DMR-0723032 and CBET-115940
247
Materials Science and
Engineering: Synthesis and
Application of Organic and
Bio Materials
Session Chair: Sung Joo Kim
248
Reduction of Voc loss in a polymer photovoltaic cell via interfacial molecular
design: insertion of a molecular spacer
David Bilby1, Jojo Amonoo2, Matthew E. Sykes1, Bradley Frieberg3, Bingyuan Huang1,
Julian Hungerford4, Max Shtein1,3,4, Peter Green1,2,3,4, Jinsang Kim1,3,4,5
1
Materials Science and Engineering, University of Michigan
3
Macromolecular Science and Engineering, University of Michigan
4
5
Department of Chemistry, University of Michigan
2
Loss to the open circuit voltage (Voc) in organic photovoltaic cells is a critical bottleneck to
achieving high power conversion efficiency. We demonstrate that the insertion of
multilayers of a poly(phenylene ethynylene) spacer into the planar heterojunction between
poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester incrementally escalates
the Voc of a polymer solar cell from 0.43 V to 0.9 V. Through a combination of light
intensity and temperature dependent measurements, we show that this control over the
molecular structure local to the interface increases Voc by raising the polaron pair energy
and by suppressing the dark-diode current.
This work was supported as part of the Center for Solar and Thermal Energy Conversion,
an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of
Science, Basic Energy Sciences under Award Number DE-SC-0000957.
249
Design principles of conjugated polymers for realization of directed
alignment
Kyeongwoon Chung,1 Bong-Gi Kim,2 Eun Jeong Jeong,2 Jong Won Chung,4 Sungbaek
Seo,1 Bonwon Koo,4 and Jinsang Kim1,2,3*
1
Macromolecular Science and Engineering,
Department of Material Science and Engineering,
3
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
4
Display Device Laboratory, Materials and Device Institute, Samsung Advanced Institute of Technology,
Samsung Electronics Company, Ltd., Youngin 446-712, Korea
2
Conjugated polymers (CPs) having one-dimensional p-orbital overlap along their long
rigid rod-like conjugated backbone exhibit anisotropy in their characteristics such as
absorption, emission and charge mobility. Therefore, alignment of CPs is essential to fully
realize their unique anisotropic properties in device applications. In this presentation,
molecular design principles in order to achieve directed alignment of CPs will be
systematically discussed: (1) chain planarization under a concentrated condition, and (2)
bulky side chains on (3) tetrahedral out-of-plane bonding to regulate the mobility of the
CP chains and their self-assembly. The aligned film of the designed lyotropic liquid
crystalline CP exhibited a high dichroic ratio of 16.67 in emission, and well-defined
lamellar-type molecular packing and alignment were confirmed by means of 2-D grazing
incidence X-ray diffraction measurement. Moreover, the hole mobility along the alignment
direction was measured as high as 0.86 cm 2/V•s in thin film transistors, which is more
than three orders of magnitude higher than that of the perpendicular to the alignment
direction.
This work is supported by the US Department of Energy (DOE), Office of Basic Energy
Sciences, as part of the Center for Solar and Thermal Energy Conversion, an Energy
Frontier Research Center (DE-SC0000957).
250
5,6-Dihydroxyindole as Key Mussel-Mimicking Adhesive Molecular Structure
in Biomimetic Thin Films
Noah Gajda1 and Jinsang Kim1,2,3,4
1
Department of Materials Science and Engineering
3
Department of Biomedical Engineering
4
Department of Macromolecular Science and Engineering
University of Michigan, Ann Arbor, MI 48109-2130
2
Dopamine has become a molecule of great interest within the field of mussel-inspired
adhesive materials because it self-deposits to form a hydrophilic thin film, polydopamine,
on a wide variety of surfaces. Structural characterization of polydopamine has been
difficult because of its high reactivity and insoluble nature. Previous efforts have
proposed that dopamine undergoes an oxidative self-reaction to form the conjugated
intermediate 5,6-dihydroxyindole (DHI) and then aggregates to form thin films onto
substrates. While this structure has been clearly identified within polydopamine, we
further explored the DHI intermediate to determine the link between its structure and the
adhesive properties of the thin films. We found that catecholamine functionalities are
enough for molecules to self-deposit onto surfaces but without the presence of a
conjugated indole structure, the thin films did not have the same robust nature as
polydopamine. Through the formation of DHI oligomers with extended conjugation, these
molecules are able to self-assemble with extremely strong intermolecular forces that
generate the versatile adhesive characteristics and insoluble nature of the film. We will
continue to explore the properties of the mussel-mimicking structure DHI for the use in
further biomimetic adhesive applications.
Acknowledgement of funding agencies, and collaborators who are not co-authors.
251
Transparent Superomniphobic Surfaces
Kevin Golovin1, Duck Hyun Lee1, Joseph Mabry2, Anish Tuteja1
1
2
Air Force Research Laboratory, Edwards Air Force Base, CA
Superomniphobic surfaces display contact angles >150° with nearly all liquids. Such a
surface has the potential to be self-cleaning, drag reducing, chemical shielding and stain
repelling. Not only are these surfaces extremely rare, but the large majority are opaque.
To extend the usefulness of liquid-repellant surfaces to applications such as windows,
smartphone screens, LCDs or eyeglasses, the surfaces must be transparent. In this work,
we design superomniphobic surfaces that are highly transparent while maintaining a
contact angle hysteresis of <3° for all tested liquids. The surfaces are fabricated using a
facile mold and spray technique that is easily scalable to large scale fabrication. The flow
field formed during spray-coating allows for highly controllable particle deposition. Such
control facilitates the design of textured surfaces that repel organic solvents, alcohols,
oils, acids and aqueous media. Nearly all known liquids simply bead up and roll off the
surfaces with little-to-no tilt angle. The surfaces fabricated in this work are the first to
maintain a high degree of transparency while allowing low surface tension liquids like
ethanol and hexadecane to roll off with a contact angle hysteresis of <3°.
252
Patterned Superomniphobic-Superomniphilic Surfaces: Templates for SiteSelective Self-Assembly
Sai P.R. Kobaku1, Arun K. Kota2, Duck Hyun Lee2, Joseph M. Mabry3, and Anish
Tuteja1,2*
1
Department of Macromolecular Science & Engineering, University of Michigan, Ann Arbor
Department of Materials Science & Engineering, University of Michigan, Ann Arbor
3
Rocket Propulsion Divison, Air Force Research Laboratory
2
Superomniphobic surfaces display both superhydrophobicity (apparent contact angle, q *
> 150º and low contact angle hysteresis with water) and superoleophobicity ( q * > 150º and
low contact angle hysteresis with low surface tension liquids like oils and alcohols).
Superomniphilic surfaces display both superhydrophilicity and superoleophilicity i.e., q * ~
0º with both water and low surface tension liquids. Patterned surfaces containing well
defined domains that display both these extreme wetting properties have many potential
applications in fog harvesting and liquid transport, microchannels and microreactors,
enhanced condensation and boiling heat transfer, and the selective deposition of thin
films. However, the majority of patterned surfaces developed thus far exhibit extreme
wettability contrast only with high surface tension liquids such as water (surface tension,
-1
g lv = 72.1 mN m ), thereby limiting the applications of such surfaces mostly to surfactantfree aqueous systems. In this work, we have developed first-ever patterned
superomniphobic-superomniphilic surfaces that exhibit stark contrast in wettability with a
wide range of polar and non-polar liquids. Using such patterned surfaces, we
demonstrate the site-selective self-assembly of both high as well as very low surface
tension liquids upon dipping and spraying. We have also demonstrated that here
developed patterned surfaces can be applied to enhance both condensation and boiling
heat transfer with low surface tension liquids. Further, we have utilized these patterned
surfaces for site-selective self-assembly of a wide variety of polymers films and
microparticles in different shapes and sizes.
We thank Dr. Charles Y-C. Lee and the Air Force Office of Scientific Research (AFOSR)
for financial support under grants FA9550-11-1-0017
253
Room Temperature Phosphorescence of Metal-free Organic Materials
Dongwook Lee1, Onas Bolton2, Byoung Choul Kim1,4, Ji Ho Youk5, Shuichi Takayama1,4,6,
and Jinsang Kim1,2,3,4,*
1
Department of Materials Science and Engineering,
3
Department of Chemical Engineering, 2300 Hayward St., University of Michigan, Ann Arbor, MI 48109;
4
Department of Biomedical Engineering, 2200 Bonisteel Blvd., University of Michigan, Ann Arbor, MI 48109;
5
Department of Advanced Fiber Engineering, Division of Nano-Systems Engineering, Inha University,
Incheon, 402-751, Korea,
6
Division of Nano-Bio and Chemical Engineering WCU Project, UNIST, Ulsan, Korea
2
Phosphorescent materials have attracted much attention due to potential applications in
solid-state lighting because they can provide three-fold higher internal quantum efficiency
in electronic luminescence devices than fluorescent alternatives by harvesting triplet
excitons through intersystem crossing. Many organometallic compounds are efficient
phosphors since spin-orbit coupling is promoted by metals. While these materials exhibit
high quantum efficiency they require rare and expensive elements such as platinum and
iridium. Developing metal-free organic phosphorescent materials is promising but
challenging because suppressing the vibration of triplets, one of the key processes to be
phosphorescent, is not efficient without heavy metal atoms. While recent studies reveal
that bright room temperature phosphorescence can be realized in purely organic
crystalline materials through directed halogen bonding, these organic phosphors still have
limitations to practical applications due to the stringent requirement of high quality crystal
formation. In this presentation, we will report bright room temperature phosphorescence
by embedding a purely organic phosphor into an amorphous glassy polymer matrix. Our
study implies that the reduced beta (β)-relaxation of isotactic PMMA most efficiently
suppresses the vibrational decay and allows the embedded organic phosphors to achieve
a bright 7.5% phosphorescence quantum yield. We will also demonstrate a microfluidic
device integrated with a novel temperature sensor based on the metal-free purely organic
phosphors in the temperature-sensitive polymer matrix. This unique system has many
advantages: (i) simple device structures without feeding additional temperature sensing
agents, (ii) bright phosphorescence emission, (iii) a reversible thermal response, and (iv)
tunable temperature sensing ranges by using different polymers.
254
Developments of Polydiacetylene Liposome Microarray toward Influenza A
Virus Detection
Sungbaek Seo1, Jiseok Lee1, Eun-Jin Choi5, Eun-ju Kim5, Jae Young Song5, Jinsang
Kim1,2,3,4
1
Department of Materials Science and Engineering,
3
Department of Chemical Engineering,
4
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109,
5
Animal Plant and Fisheries Quarantine and Inspection Agency, 175 Anyangro, Manan-Gu, Anyangsi,
Gyeonggido, 430-757, Republic of Korea
2
We systematically studied the effect of the target size on the turn-on signaling of
polydiacetylene (PDA) sensory systems for detection of biological molecules based on
the intermolecular interactions between a probe molecule and its target. The interaction
between the M1 peptide and the M1 antibody of influenza A virus was rationally devised
into a PDA sensor design for direct and indirect detection of influenza A virus. By using
the same pair but only switching their role as a probe or a target in the detection system,
we could keep the same paring affinity and therefore unquestionably examine the target
size effect. While the larger M1 antibodies produced red fluorescence emission upon
binding with densely packed M1 peptides at the PDA liposome surface, the smaller M1
peptides could not generate any noticeable signal when they bound to tightly packed M1
antibodies. When the probe density at the PDA surface was low, we could not observe
any sensory signal generation from the PDA microarray regardless of the role of M1
antibody and M1 peptide. These results clearly revealed that the PDA sensory signal is
mainly from the steric repulsion between probe-target complexes not the strength of the
probe-target binding force. Based on the finding, we developed PDA microarray for direct
detection of influenza A virus. The PDA liposome microarrays having densely packed M1
antibody probes and co-assembled phospholipids allows turn-on sensory signal within 1
hour and comparable detection limit with conventional kits. The demonstrated target size
effect can be readily applicable to various PDA-based biosensor design and
developments.
255
Nanoparticle encapsulation in thin film micellar structures: A physical method
for functional materials design
Junnan Zhao1 and Peter F. Green1*
1
Department of Materials Science and Engineering, University of Michigan, Ann Arbor
Thin films functional materials exhibit properties that render them viable for diverse
applications from sensors to electronic devices. The properties of these materials can be
tuned by controlling the spatial distribution of inorganic nanoparticles over various length
scales. The major fabrication challenge is associated with understanding and controlling
the factors, such as confinement and enthalpic and entropic interactions, which affect the
organization of nanoparticles. In this work, we investigate the confinement of gold
nanoparticles, onto which poly(2-vinylpyridine) (P2VP) are end-tethered, in supported thin
film diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP)/homopolymer PS
blends. The thin film nanocomposites were prepared by spin-casting mixtures of
nanoparticles, the copolymer chains and homopolymer chains onto a substrate. The
samples were then annealed above the glass transition of the polymers, resulting in the
formation of spherical micelles composed of inner cores of the P2VP segments and outer
coronas of the PS blocks throughout the PS homopolymer host. All nanoparticles were
encapsulated within micelle cores; on average each micelle contains one, or no,
nanoparticle. The micelles exhibited a strong tendency to self-organize at interfaces when
the PS homopolymer chain length is large compared to the PS corona chain length. In
comparison to pure PS-b-P2VP/PS blends, the nanoparticle/PS-b-P2VP/PS blends
contain a higher density of, on average, smaller micelles. This sample fabrication
procedure is straightforward and compliments the current “toolbox” used to create
functional materials from block copolymer/nanoparticle systems.
256
Mechanical Engineering:
Design and Manufacturing
Session Chair: Joshua Padeti
257
Optimal Data Assimilation and Utilization for Intelligent Traffic Management
Kang-Ching Chu1, Kazuhiro Saitou1
1
Mechanical Engineering, University of Michigan
Traffic congestion in urban areas is posing many challenges, while utilizing high-quality
traffic information from traffic flow model can be beneficial for congestion management.
Because of the popularization of GPS equipment, travel data from individual vehicles (as
known as probing data) became an attractive alternative to fix-location detectors as a
data source for traffic status estimation. However, traffic engineers are still trying to
develop an optimal strategy for traffic data collection and traffic information utilization.
This research focuses on investigating the appropriate data assimilation technique for
macroscopic traffic model using probing and fix-location data; formulating optimization
problem for probe vehicle deployment by considering information quality and operation
cost; and then developing traffic information distribution strategy with predicted traffic
status. The first attempt used Newtonian relaxation method to incorporate probe data into
a deterministic macroscopic traffic flow model. The preliminary result of probe vehicle
deployment revealed the trade-off between the quality of traffic density estimation and
probing cost using multi-objective genetic algorithm. The result suggested that probing
strategy may be adaptive with traffic condition, since the decreasing probe data during
congestion would only cause negligible degradation on the estimation performance.
Filtering-based method for data assimilation with modified traffic flow model will be the
next step. Future goal would be developing an adaptive traffic information utilization
strategy using the prediction quality of traffic status under varied traffic condition.
Furthermore, microscopic traffic simulation would be used to evaluate the benefit of
individual driver and the efficiency of transportation system using proposed strategy.
258
Knowledge-based Trajectory Generation for Advanced Manufacturing
Molong Duan1
1
Advanced manufacturing machines (AMMs) are utilized in a family of manufacturing
activities that, among others, make use of cutting edge materials and emerging
capabilities enabled by the physical and biological sciences. AMMs have to maintain
submicron tolerances during contouring and at the same time travel as fast as possible so
as to increase productivity. Large portion of AMM’s motion error stems from the dynamic
error due to the non-contact feature (e.g. laser micro machining and PCB manufacturing);
therefore, motion generation (or trajectory generation) is often utilized to improve the
motion quality of AMMs especially at sharp corners.
The industrial look-ahead algorithms employ user defined parameters to slow down the
process, which do not incorporate the knowledge of the system, controller limits
accurately. Also, the procedure often leads to trial and error, and the possible
conservative parameters sacrifice the velocity and thus reduce the productivity.
Therefore, the objective of this research is to incorporate the machine dynamics of AMMs
into motion generation so as to develop a comprehensive method for minimizing cycle
time while ensuring that tolerance constraints are not violated. To be practical, the
developed methods must be (1) computationally efficient and (2) robust to modeling
errors.
To achieve that goal, a two-stage architecture which consists of constrained trajectory
optimization, parameterization, and inverse dynamics is established as a novel trajectory
generation scheme, with which the corner velocity is significantly increased, also the
contour error is maintained.
259
A simplistic model for quadrupedal walking and trotting
Zhenyu Gan1, C. David Remy2
1
Department of Mechanical Engineering
Traditionally, two different simplistic models have been used to describe the dynamics of
human locomotion. A spring-mass model for running and an inverted pendulum model for
walking. While the latter failed to explain the characteristic double hump in the vertical
ground reaction forces of a walking motion found in nature, the spring-model can do so in
a different oscillation mode.
We developed a passive dynamic quadrupedal model that is able to produce walking and
trotting with a single set of parameters. The model has an extended main body and four
massless legs that, during swing, instantaneously go to a predefined angle of attack;
similar to a bipedal SLIP model. Periodic motions of this model were identified in a
MATLAB simulation framework for gait creation. An automated method to identify model
parameters to optimally match the ground reaction forces of the model with experimental
data has been developed.
Our model is able to produce periodic walking and trotting gaits, that qualitatively exhibit
the same ground reaction forces as seen in the data of a representative crossbred horse
(as provided to us by the Veterinary Teaching Hospital Zurich). Through means of
automated parameter adjustment, we are very closely matching trotting data in a
quantitative fashion and currently investigating how to do so for a walking gait. Ideally we
succeed in quantitatively matching ground reaction forces for both, trotting and walking
gaits, thus creating a single model that explains the different dynamic behaviors of
quadrupedal locomotion.
260
Estimation of Active Maintenance Opportunity Windows in Stochastic
Production Lines
Xi Gu1, Xiaoning Jin1, and Jun Ni1
1
Effective maintenance actions can preserve or improve system availability, product quality
and plant cost-effectiveness in automated manufacturing systems. However, arbitrarily
stopping machines for maintenance will occupy their production time and may introduce
production losses to the system. There may exist hidden opportunities during production,
such that specific machines can be actively shut down for maintenance without penalizing
the system throughput. In this paper, such time intervals are defined as active
maintenance opportunity windows (AMOWs). We develop a Bernoulli model to
analytically estimate AMOWs in a stochastic two-machine-one-buffer line. A recursive
procedure based on aggregation method is used to estimate the AMOWs in long lines.
For balanced lines, a heuristic approach is proposed. The effectiveness of the methods
has also been validated through numerical studies.
This work is based upon work supported by the National Science Foundation under grant MES 0825789 “Short-Term Joint Maintenance and Production Decision Support Tool of Manufacturing
Systems”.
261
Within-cycle monitoring and diagnosis of cyclic nonlinear profile signals
Weihong (Grace) Guo1, Judy Jin1, S. Jack Hu2
1
2
Department of Industrial and Operations Engineering, The University of Michigan, Ann Arbor, MI
Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI
With the rapid development of online sensing technologies, many real-time signals of
process information are readily available in manufacturing processes. Particularly, cyclic
signals are collected from repeatable operations where each cycle represents the signal
collected from one part produced. In order to fully utilize this information, there have been
many studies on the monitoring of cyclic signals. However, existing research are limited to
detecting process changes after a part is produced based on its complete cycle of
signals.
In practice, especially short-duration processes with critical part quality and high cost,
between-cycle monitoring decisions are too late. It is more beneficial to detect the
process changes before a part is produced so that corrective actions or process
adjustments can be quickly triggered.
This research develops a monitoring and diagnosis methodology based on an early
portion of cyclic signals. The proposed method is capable of making within-cycle
decisions and the results can be used for guiding real-time process adjustments for defect
prevention.
The work presented in this poster aims to determine the segmentation of the cyclic signal
for early detections and to develop a within-cycle monitoring technique using wavelets,
logistic regressions, and control charts. More specifically, we first determine a minimum
signal segment which can make a reliable detection and also leave sufficient time till the
end of the cycle for process adjustment to be effective. The changes in profiles are then
characterized using wavelet coefficients. Logistic regression models and a control chartbased method are then developed to detect fault condition.
Funding: The research is sponsored by the General Motors Collaborative Research Lab
in Advanced Vehicle Manufacturing at the University of Michigan.
262
High-performance micromachining of glass using electrochemical discharge
machining (ECDM)
Baoyang Jiang1, Shuhuai Lan1, Jun Ni1
1
The demand of non-conductive material has grown rapidly with the broad application in
optical, electrical, and mechanical systems. Glass is expansively employed due to the
properties including optical transparency, high stiffness, and good chemical resistance.
Typical engineering glass is non-conductive, brittle, and hard, making it difficult to
machine. Conventional electrical discharge machining (EDM) or electrochemical
machining (ECM) cannot be applied to glass because these machining processes require
workpiece to be electrically conductive. Electrochemical discharge machining (ECDM),
taking advantage of electrochemical discharge phenomenon, is a non-traditional micromachining process for non-conductive materials. ECDM has been seen as a promising
technology for precision micro-machining of glass. Features with high aspect ratio and
complicated geometry can be created by ECDM.
Machining quality and efficiency of conventional ECDM process is far from satisfactory.
Surface quality and machinable depth is limited in many applications. ECDM process can
be improved either by introducing innovative methods, or by refining current process with
comprehensive process models. Both approaches are adopted in this research.
263
Low cost and Energy Efficient Vibration Reduction of Ultra-Precision
Manufacturing Machines
Jihyun Lee1, Chinedum Okwudire1
1
Mechanical Engineering, University of Michigan Ann Arbor
Due to increased global competition and concerns about the environment, today’s
advanced manufacturing machines not only have to achieve high accuracy and speed but
also low cost and energy consumption. Ultra-precision manufacturing (UPM) machines
are designed to manufacture and measure parts with micron level features and
nanometer level accuracy. Therefore, they play a central role in a variety of advanced
manufacturing processes. Due to the stringent accuracy requirements on UPM machines,
they need to be isolated from ground vibrations. Generally, passive isolators are often
preferred over active isolators because they are cheaper and energy neutral. However,
passively isolated UPM machines suffer from residual vibrations during the motion of the
machines’ axes which degrade their speed and accuracy. As a result, active isolators
are utilized in high end UPM machines to reduce residual vibrations but this leads to
higher costs and energy consumption. It has however been observed that some machine
design parameters (e.g. isolator/motor locations) have a significant impact on the
performance of passively isolated UPM machines. For instance, prior results from my
research have shown that unwanted vibrations can be significantly reduced simply by
changing the isolator locations due to an interesting dynamic phenomenon known as
mode coupling. My research seeks to understand how to optimally exploit mode coupling
so that superior vibration reduction can be obtained using passive isolators. If successful,
it will enable high end UPM machines to be designed with passive instead of active
isolators thereby reducing cost and energy consumption while maintaining high
performance.
264
Friction stir welding of dissimilar Al alloy to advanced high strength steel
Xun Liu1, Shuhuai Lan1, Jun Ni1
1
S.M. Wu Manufacturing Research Center, Department of Mechanical Engineering, University of Michigan,
Ann Arbor, MI 48109, USA
Sheets of aluminum alloy 6061-T6 and one type of Advanced High Strength Steel (AHSS),
TRIP 780/800 have been successfully butt joined using Friction Stir Welding (FSW)
technique. The maximum ultimate tensile strength of the joint can reach 85% of the base
aluminum alloy. Effects of process parameters were investigated from aspects of
microstructure evolution, mechanical welding forces and temperature distribution during
the process. Intermetallic compound (IMC) layer of FeAl or Fe 3Al with thickness of less
than 1 micron is formed at the Al-Fe interface in the advancing side, which can actually
contribute to the joint strength. Aluminum matrix in the weld nugget is enhanced by
dispersed sheared-off steel fragments encompassed by a thin intermetallic layer or simply
intermetallic particles. Welding speed has an insignificant effect on either temperature
distribution or mechanical welding forces and accordingly the composition of the
intermetallic layer. However, larger welding speed can effectively reduce the length of
thermal history and the interlayer thickness. The relationship between the thickness of
interlayer and welding speed depends on the type of intermetallic compound that is
formed. Higher rotational speed and larger tool offset will increase the temperature
distribution and reduce the required mechanical welding force in both lateral and axial
directions. Besides, these two factors can affect the composition of the formed
intermetallic compounds.
Acknowledgements
This work is supported by the CERC-CVC U.S.-China Program of Clean Vehicle.
265
Value of wind diversity for increased integration of wind power into the grid
Josh Novacheck1, Jeremiah Johnson2
1
Department of Mechanical Engineering/School of Natural Resources and Environment, University of
Michigan
2
Center for Sustainable Systems, School of Natural Resources and Environment, University of Michigan
Sudden variability in wind power output can cause wind to be an unreliable power source.
The fast ramping up or down of its power output can have negative consequences for grid
operations, including increased costs. One method to deal with ramp rate variability of
wind farms is to develop wind farms that are subject to different wind patterns, essentially
diversifying the wind power portfolio. If proper wind power portfolios are chosen, the
cumulative power output of the portfolio will smooth out the variability of individual wind
farms. Mean-Variance Portfolio optimization (MVP) is one technique that can be utilized
to help determine optimal portfolios that are diverse and maximize power output. In one
example, MVP is applied to investigate benefits of wind diversity in Minnesota. In this
case, large ramping events, defined by the ramping up or down of wind power output by
more than 5% of total capacity within ten minutes, are decreased from occurring 10%
over the sample period to less than 2% of the time. Average forecasting errors also
decrease from 14.2% to 7.8% using MVP. Using a zonal model of the US Eastern
Interconnect, the benefits to the grid of using MVP to develop future wind power sites can
be generalized beyond the simple Minnesota example. The benefits of adding diverse
wind portfolios onto the grid can decrease the overall costs of wind power integration,
allowing for increased wind power development.
I would like to thank Maite Madrazo and Markus Walther, graduate students in the School
of Natural Recourses and Environment, for their work to develop the Eastern Interconnect
model.
266
A Near-Optimal Power Management Strategy for Rapid Component Sizing of
Power Split Hybrid Vehicles with Multiple Operating Modes
Xiaowu Zhang1 Huei Peng1, and Jing Sun2
1
2
Department of Naval Architecture & Marine Engineering, University of Michigan
In the design of hybrid vehicles, it is important to identify proper component sizes. When
the design search space is large, exhaustive optimal strategies such as dynamic
programming (DP) is too time-consuming to be used. Instead, a near-optimal method
that is orders of magnitude faster than DP is needed. One such near-optimal method is
developed and presented in this research. This method is applied to design the
powertrain parameters of all power-split hybrid vehicles utilizing a single planetary gear
(PG). There are 12 possible configurations, 6 input- and 6 output-split, and each
configuration has up to 4 modes [1]. Based on the analysis of the efficiency of powertrain
components of the four modes, and the “Power-weighted Efficiency” (PE) concept, we
show that the computation time can be reduced by a factor of 10,000 compared with the
dynamic-programming approach. The optimal design of each configuration is analyzed
and presented.
[1] X. Zhang, C. Li, D. Kum, H. Peng, “Prius+ and Volt-: Configuration Analysis of Power-Split Hybrid Vehicles with a
Single Planetary Gear”, IEEE Transactions on Vehicular Technology, vol. 61, Issue 8, pp. 3544-3552, 2012.
267
Automotive Engineering &
Transportation
268
Design of Next Generation Biofuels
Tyler Dillstrom1, Jason Lai1, Akbar Mohamad1, Paolo Elavti1, and Angela Violi1
1
Low temperature combustion is dominated by chemistry and transport propertied. The
Violi group utilizes molecular scale simulations in tandem with quantum scale calculations
to bridge the gap between biotechnology groups that engineer novel biofuels, and engine
researchers. Out findings provide a necessary link between the molecular structure of
fuels and their macro-scale performance in engines.
Funding sources: NSF, AFORSR, DOE- CERC-CVC
269
“Wheels vs. Tracks” A Comparison Study for Small Unmanned Ground
Vehicles from Power Consumption Perspective
Tianyou Guo1, Huei Peng2
1
2
Small Unmanned Ground Vehicles (SUGVs) can perform many surveillance, scouting,
detection and rescue missions and keep soldiers out of harms’ way in the battlefield.
Usually SUGVs operate on various terrains (soft or hard, rough or flat). The issue of
wheeled SUGVs vs. tracked SUGVs for off-road operations with regard to mobility and
power consumption has been a subject of debate for a long period of time. This study that
considers SUGVs at about 15kg aims at comparison of tracks vs. wheels that is focused
on power consumption on soft soil. This study includes 3-D track-terrain interaction skid
steering model and 5-D wheel-terrain interaction skid steering model to do the
comparison. 5-D wheel-terrain interaction skid steering model is a new model that
considers 3-dimensional contact surface with various sinkage of inner and outer wheels.
Both models also include zero-radius turning maneuver which is widely used in skid
steering SUGVs. Simulation compares torque and power consumption of each
configuration and weight effect, slip ratio and drawbar pull are also studied.
This work was funded by the Automotive Research Center (ARC), a U.S. Army center of
excellence in modeling and simulation of ground vehicles at the University of Michigan.
270
Reaction Pathway and Elementary Ignition Behavior of Surrogates for JP-8
and Alternative JP-8 Fuels
Dongil Kang1, Vickey Kaslaskar2, Jason Martz3, Angela Violi1,3 and André Boehman3
1
Energy and Mineral Engineering, Pennsylvania State University
3
2
The cetane number (CN) variation of jet fuels causes difficulty in military ground vehicles with
diesel/compression-ignition engines. Recently, computational fluid dynamic (CFD) modeling
studies from Dr.Violi’s research group at University of Michigan developed two accurate JP-8
surrogates (UM I, UM II), capturing the CN and property variations in the various types of jet fuels
that can be used in Army ground vehicles, but these surrogates are not validated on any practical
combustion platforms. Therefore, to provide validation experiments to compare elementary
ignition behavior, a modified Cooperative Fuel Research (CFR) engine was tested where various
equivalence ratios, compression ratios, and fuel and air intake temperature were employed,
focusing on the chemical portion of the ignition delay of the surrogate fuel formulations in
comparison with a practical JP-8 fuel (POSF-4658). Our group investigated the elementary
ignition behavior including the percentage of low temperature heat release the critical
compression ratio and the critical equivalence ratio of each surrogate single compound, the UM
surrogate JP-8 mixtures and the practical JP-8 fuel. Furthermore, condensed exhaust trapping
and subsequent detailed chemical analysis highlighted the reaction pathways for a particular
molecule. This study is intended to provide an intermediate step to validate simulations based on
the surrogate fuel representation of JP-8 and the kinetic model to describe its combustion,
contributing not only by supporting the ongoing work of Dr.Violi’s research group on surrogate
fuels development, but also by building a predictive engine simulation capability, resulting in the
development of robust and efficient vehicle powertrains fueled with JP-8.
Acknowledgement: “Automotive Research Center (ARC), a U.S. Army center of excellence in
modeling and simulation of ground vehicles”
271
Model Predictive Control based Vehicle Motion Control to Mitigate
Secondary Crashes after a Minor First Impact
Byung-joo Kim1, Huei Peng1
1
It has been shown that even a minor collision between vehicles can lead to devastating
consequences if the driver fails to react properly. To reduce the severity of possible
subsequent (secondary) crashes, this study considers both vehicle heading angle and
lateral deviation from the original driving path. The research concept here is different from
today’s electronic stability control (ESC) systems in the sense that the differential braking
is activated even when the yaw rate and vehicle slip angle is very high, and the relative
lateral and yaw positions with respect to the road are part of the control objective. As a
control strategy to achieve the goal, the Linear Time Varying Model Predictive Control
(LTV-MPC) method is used, with the key tire nonlinearities captured through linearization.
We consider tire force constraints based on the combined-slip tire model and their
dependence on vehicle motion. The computed high-level (virtual) control signals are
realized through a control allocation problem, which uses a map between vehicle motion
control commands and independent braking forces under feasible constraints. Numerical
simulation and analysis results are presented to demonstrate the effectiveness of the
control algorithm.
272
Maximum Load Limit of Boosted HCCI Combustion in a NVO Engine
Stefan Klinkert1, George Lavoie1, Dennis Assanis2, Volker Sick1
1
2
Stonybrook University
Homogeneous charge compression ignition (HCCI) engines offer the potential to
simultaneously achieve high efficiency and low emissions. Implementation and practical
use of HCCI combustion, however, remain a challenge due to the limited operating range.
Studies aiming at high load extension of HCCI to date have only been done on laboratorytype engines with conventional valvetrains and degrees of freedom over intake/ exhaust
conditions that are not necessarily viable from a practical standpoint. This research work
is unique in that a practical NVO engine was used to independently investigate the effects
of intake boost pressure, charge composition, thermal/ compositional stratification (NVO)
and exhaust-back pressure on burn duration and combustion phasing limits.
To determine the potential benefit of conventional positive valve overlap (PVO) operation
on the maximum load limit, experiments were supplemented by a parametric study using
a 1-D engine simulation software. A parameter walk from a NVO to PVO engine showed
that improved volumetric efficiency, due to enhanced breathing and a decrease in RGF
content, and lower engine speed, allowing further combustion phasing retard, are key
enablers that suggest PVO operation can be a useful pathway to achieving higher loads.
The results of this research work have provided new insight into what limits maximum
load of an HCCI engine and shown how the thermo-physical state of the mixture as well
as operating conditions affect the maximum attainable load through its implications on
combustion phasing limits.
273
Vehicle-Dynamics-Conscious Real-Time Hazard Avoidance in Autonomous
Ground Vehicles
Jiechao Liu1, Paramsothy Jayakumar2, James L. Overholt3,
Jeffrey L. Stein1, Tulga Ersal1
1
U.S. Army RDECOM-TARDEC
3
Air Force Research Lab
2
Unmanned ground vehicles (UGVs) are gaining importance and finding increased utility in
both military and commercial applications. Historically, UGVs have often been small and
teleoperated but current interest is in much larger fully autonomous vehicles. Due to their
size, higher operating speed and ability to navigate more complicated terrain, these larger
size vehicles have significantly different dynamic and, therefore, require different
approach to hazard avoidance algorithms. This work is focused on the development of a
model predictive control (MPC) based hazard avoidance algorithm that is aware of the
dynamic limitations of the vehicle and can thus push the vehicle to its limits to maximize
its performance. To achieve this, a maximum steering angle that prevents tire lift-off is
obtained from a vehicle model given the vehicle speed and terrain slope. The optimal
steering sequence that avoids the obstacles and navigates the vehicle to the target is
calculated within the safe steering range using another vehicle representation. The
developed MPC based hazard avoidance algorithm is evaluated as a function of the
incorporated model fidelity. Results indicate that mixed fidelity models can potentially be
used to achieve good obstacle avoidance behavior while simultaneously reducing the
computation required. In particular, a 14 degree of freedom (DoF) vehicle model with
Pacejka Magic Formula tire model is used to establish the safe steering range and a 2
DoF vehicle model with linear tire model is used to find the optimal steering sequence
along the prediction horizon.
This work was supported by the Automotive Research Center (ARC), a U.S. Army Center
of Excellence in Modeling and Simulation of Ground Vehicles, led by the University of
Michigan and U.S. Army TARDEC.
274
Comparison of terramechanics modeling methods for simulating steady-state
wheel-terrain interaction for small vehicles
William Smith1, Daniel Melanz2, Carmine Senatore3, Karl Iagnemma3, and Huei Peng1
1
Department of Mechanical Engineering, University of Wisconsin
3
Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology
2
A simulation study was conducted to evaluate three common terramechanics methods
used for predicting single wheel performance of small vehicles on granular terrain. Small
ground vehicles are used in areas where mission success is critical, such as planetary
exploration and explosive disarmament. Modeling the interaction between wheel and soil
using terramechanics can reduce the risk of immobilization due to insufficient thrust
production and low propulsion efficiency through improved vehicle design and control.
The Bekker method, the most common form of terramechanics modeling, assumes
steady-state operation on smooth, flat ground. Small vehicles frequently operate under
conditions that violate this assumption. More complex models are required to simulate
multibody vehicle dynamics over rough terrain, such as the dynamic Bekker method and
the discrete element method (DEM). Before these methods can be evaluated under
dynamic conditions, they must first be tested in steady-state operation. Single wheel
experiments were performed to evaluate wheel performance at various slip ratios on
Mojave Martian Simulant. Similar tests were simulated using the three terramechanics
modeling methods to evaluate the quantitative and qualitative accuracy of each method.
Each method was tuned to match direct shear and pressure-sinkage soil tests using the
same soil. The results show that DEM better predicts wheel performance at steady-state,
though the computation penalty compared to Bekker-type methods is significant. DEM
also captures some of the experimental time series behavior for drawbar pull and driving
torque.
This work was supported in part by a Science, Mathematics & Research for
Transformation (SMART) Scholarship.
The authors of this paper would like to
acknowledge members of the US Army Tank Automotive Research Development and
Engineering Center (TARDEC), especially Dr. Paramsothy Jayakumar, for their feedback
and suggestions. We would also like to thank TARDEC for the use of their HPC cluster
computer, which was used to conduct the majority of the DEM simulations.
275
Reducing Rollover Risk of a High Speed Mobile Manipulator
Justin G. Storms1 and Dawn M. Tilbury1
1
Small-scale unmanned ground vehicles are prone to rollover when operated at high
speed. Remote teleoperators are often forced to drive the robot slowly, with gradual turns
to avoid rollover. This paper proposes to use a manipulator arm on the robot in a dynamic
weight-shifting arrangement to reduce rollover risk. Compared to other methods for
reducing rollover, this method does not require reducing speed or turning radius. Use of
the manipulator arm for weight-shifting is presented, and a simple linear control law for
the manipulator arm angle is proposed. A linear dynamic model is used to analyze the
effect of the arm design (link length, mass, etc.) on the roll dynamics, and a more
complex nonlinear simulation model is used to evaluate the roll reduction factor for a
range of steering angles and velocities. In a simulation of the system for a nominal design
using the same steering angle input, a roll reduction of 11% is shown. For the same
radius turn a roll reduction of 24% occurs. Consequently, a 43% reduction in steering
angle was used to achieve a similar turning radius when the dynamic weight-shifting is
activated. By increasing the rollover stability region, this semi-autonomous behavior of roll
reduction has the potential to increase the safe operating speed for mobile robots.
This work was supported in part by a fellowship from the Department of Mechanical
Engineering at the University of Michigan.
276
Mechanics of Materials &
Structures
277
Effects of Microstructure on Very High Cycle Fatigue Behavior of Magnesium
Jacob Adams1, J. Wayne Jones1, John Allison1
1
Magnesium alloys offer significant potential for structural applications because of their
high specific strength. However, development of new magnesium alloys is hampered by
incomplete understanding of the role of composition and microstructure on strengthening
mechanisms and on fatigue behavior. The current work examines the initial results of
research on the effects of microstructure on the Very High Cycle Fatigue (VHCF)
behavior of a rare-earth magnesium alloy, WE43, and presents goals in the identification
of critical fatigue mechanisms and phenomena necessary for the development of
computational models as a step towards rapid material development.
We gratefully acknowledge the U.S. Department of Energy for the funding of this project.
We also thank Bruce Davis of Magnesium Elektron for providing the material for this
research.
278
Force and Moment Generation of Fiber-reinforced Pneumatic Soft Actuators
Joshua Bishop-Moser1
1
Soft actuators are found throughout nature from elephant trunks to round worms,
demonstrating large specific forces without the need for sliding components. These
actuators offer impact resilience, human-safe interaction, versatility of motion, and
scalability in size. Biological structures often use a fiber-reinforcement around a fluid filled
elastomeric enclosure, in which the elastomeric material will capture the distributed
pressure and transfer it to the fibers, which will in turn direct the forces to the ends. We
previously discovered an entire domain of fiber-reinforced elastomeric enclosures
(FREEs), of which McKibben actuators are a small subset. The range of forces and
moments possible with FREEs has not been previously investigated. 45 FREE actuators
across the span of fiber angle configurations were fabricated and tested. The reaction
force and moment of each actuator was determined across a gamut of pressures.
Analytical models were generated using a variety of simplifying assumptions. These
models were created to provide a closed form expression that models the force and
moment data. The models were compared to the experimental values to determine their
fit; this provides an understanding of which simplifying kinematic assumptions best
represent the experimental results. Interpolated experimental results and the analytical
models are all graphically represented for use as an intuitive design tool.
The author would like to acknowledge the contribution of Prof. Girish Krishnan, Corey
Bertch, Darlene Yao, and Prof. Sridhar Kota. This work was funded by the National
Science Foundation.
279
Effects of Aluminum Content and Thickness on the Microstructure and
Tensile Behavior of AM series Magnesium Alloys
Erin Deda1, John Allison1
1
Department of Materials Science & Engineering, University of Michigan
Magnesium alloys are of interest to the automotive industry for their weight reduction
potential, due to their low density and good castability. Magnesium alloyed with aluminum
and manganese is commonly used for high pressure die casting. The ductility is highly
variable, and is dependent on location and local microstructural features. [1] This limits
the ability to use these alloys in impact sensitive applications. Important microstructural
features are porosity and secondary phase β-Mg17Al12, which have been predicted to limit
ductility. [2] [3] Models have been developed to describe the impact of these
microstructural features on the ductility, and the models that have been developed focus
on the porosity of the castings. [4] High pressure die cast plates have been cast to assess
the impact of plate thickness and aluminum content on the ductility and other tensile
properties of Mg SVDC alloys. Microstructural features of the different alloys and
thicknesses are characterized to be included in a weak link mechanical model for ductility.
Primary features that are characterized are porosity, pore band structure, and distribution
of β-Mg17Al12. Tensile properties are compared to literature models.
This work was funded by the Department of Energy Vehicle Technologies Office under
the Automotive LIghtweighting Materials Program managed by William Joost. The authors
would like to thank Ford Motor Company for the assistance and advice from Mei Li, Jacob
Zindel, Larry Godlewski, and Joy Forsmark, as well as Xin Sun at Pacific Northwest
National Labs. The authors would like to acknowledge the help of Sunnie Han (UM) for
her assistance with metallographic preparation.
[1]
[2]
[3]
[4]
280
G. Chadha, J. E. Allison, and J. W. Jones, “The Role of Microstructure on Ductility of DieCast AM50 and AM60 Magnesium Alloys,” Metall. Mater. Trans. A, vol. 38, no. 2, pp. 286–
297, Feb. 2007.
C. D Lee, “Dependence of tensile properties of AM60 magnesium alloy on microporosity
and grain size,” Mater. Sci. Eng. A, vol. 454–455, pp. 575–580, Apr. 2007.
J. Song, S.-M. Xiong, M. Li, and J. Allison, “In situ observation of tensile deformation of
high-pressure die-cast specimens of AM50 alloy,” Mater. Sci. Eng. A, vol. 520, no. 1–2, pp.
197–201, Sep. 2009.
J. P. Weiler and J. T. Wood, “Modeling the tensile failure of cast magnesium alloys,” J.
Alloys Compd., vol. 537, pp. 133–140, Oct. 2012.
Thermal Response of Laminates with Varying Fiber Orientation
Adam Duran1, Nicholas Fasanella1
1
Hypersonic aircrafts are subject to severe aerodynamic heating which may cause thermal
bucking. It is of great interest to investigate the material systems needed to maintain
structural integrity under these extreme conditions. Composites allow for tailoring of
material systems to attain the desired structural behavior. This characteristic may be
exploited to obtain materials with enhanced resistance to buckling. We investigated the
layering configuration of laminates which produced the highest resistance to thermal
buckling given a specific thermal loading. We first investigated at symmetric, balanced,
simply supported laminates. The fibers in each layer were restricted to be straight, and it
was found that a 45° angle ply, [45/-45]s, allowed for the highest temperature, before
buckling would occur. With modern manufacturing techniques, it is no longer necessary
that the fiber paths be straight and so variable stiffness panels via curvilinear fibers were
investigated. Here, fiber angles were varied along the length of the composite; therefore,
the stiffness of the laminate was a function of position. Much like the straight fiber
configuration, we sought the layup that would give the maximum temperature before
buckling occurred. We found that the maximum buckling temperature could be improved
by use of curvilinear fibers, a result contrary to examples in literature. The maximum
buckling temperature is found to be at a configuration of T0=46° and T1=26°
281
An Atomistically-informed Energy Based Theory of Environmentally Assisted
Failure
Sriram Ganesan1, Veera Sundararaghavan1
1
Department of Aerospace Engineering, University of Michigan-Ann Arbor, MI-48109, USA
For brittle fracture of crystalline solids capable of being plastically deformed, the critical energy
release rate defined as J = 2γ+γp (where, γ is the ideal work of fracture and γp is the plastic work)
is widely used as a macroscopic fracture criterion. The generally accepted notion that γp is a
material property, similar to γ, is called into question when considering embrittlement processes.
In this work, we study the critical energy release rate in embrittlement of Aluminum by Gallium
using first principles atomistic calculations and recent experiments to identify the parameters in a
power law relationship between γp, γ and 'stress intensity factor', k, γp= cka γb (where a,b and c
are material constants). Material constant a=2.002 was obtained for aluminum and is similar to
published results. The atomistic model and the simple power law form of γp give a good estimate
of the macroscopic brittle failure regime of the ductile material, and describe various aspects of
embrittlement such as fracture toughness, KIC and subcritical value of stress intensity, KIscc.
282
Novel Techniques for Studying the Role of Microstructural Variation on Very
High Cycle Fatigue Crack Formation in Ti-6Al-2Sn-4Zr-2Mo
Jason Geathers1, J. Wayne Jones2, Samantha Daly1,2
1
2
Many aerospace components originally designed for 107 cycles are exceeding their
expected lifetimes (107 < Nf < 109). Additionally, new components are being designed to
operate in this very high cycle fatigue (VHCF) regime. Ultrasonic fatigue techniques at 20
kHz enable testing at 109 cycles to be achieved in hours, rather than days as required by
a 40 Hz servo-hydraulic system. Although VHCF is characterized by nominally elastic
strains, local cyclic plastic strain accumulation occurs on the microscale. Thus, fatigue
damage mechanisms are much more sensitive to the microstructural landscape in this
regime. New experimental methodologies that link local damage accumulation to
microstructural variations are essential to the design and prediction of fatigue behavior for
components in the gigacycle regime. The objective of this research is to understand the
effect of microstructure variability and environment on fatigue crack nucleation and short
crack propagation during VHCF. Ti-6Al-2Sn-4Zr-2Mo will be examined using a novel
methodology that allows in-situ ultrasonic fatigue in an environmental scanning electron
microscope (ESEM). Combined with advanced digital image correlation techniques, we
can achieve full-field, quantitative, and in situ analysis of deformation mechanisms and
damage accumulation at the microstructural length scale.
We gratefully acknowledge the Air Force Office of Scientific Research, Structural
Mechanics Program monitored by Dr. David Stargel, for funding the majority of this
research, and the Rackham Merit Fellowship Program at the University of Michigan for
providing the initial startup for this work. We would also like to thank Chris Torbet for
equipment fabrication, and our AFRL collaborators, particularly Chris Szczepanski, for
providing the material.
283
Deformation Mechanisms in Magnesium Alloy WE43 at the Microscale
Alan Githens1, John Allison1, Samantha Daly2
1
2
A technique is currently being developed to better understand the phenomenology of
ductility and fracture in magnesium alloy WE43 by determining possible failure
mechanisms at the microstructural scale. Recently, digital image correlation has been
combined with scanning electron microscopy in order to track, with high accuracy, strain
on the microstructural level. The information gathered about intragranular strain
inhomogeneities provides valuable information for computational crystal plasticity and
continuum elasto-plasticity groups by providing experimental validation and experimental
parameterization for their models. Chemistry has been developed to successfully deposit
a fine speckle pattern required for digital image correlation at the microscale through a
self-assembled arrangement of gold nanoparticles on the surface of magnesium.
Depending on the size of the nanoparticles used, this speckle pattern may be applied for
analysis at various length scales. Future work will track deformation under monotonic
tension and compression of WE43 and assess the effect of slip, twinning, and microcracking on local strain.
Funding is provided by DOE-BES contract DE-SC0008637.
284
Title: Non-diffusive Heterogeneous Phase Transformation on Shape Memory
Effect of Nitinol
Y. Gong1, S. Daly1
1
Department of Mechanical Engineering, The University of Michigan
The resultant full strain fields of non-diffusive solid phase transformation on shape
memory effect of Nitinol have been investigated. Phase transformation was induced by
uniaxial tension and temperature variation performed on an in-situ tensile stage mounted
in a scanning electron microscope. Scanning electron microscopy was used to capture
images of sample surface with micro scale speckle patterns upon every load or
temperature variation step. Digital image correlation (DIC) quantified evolution of smallscale strain fields in order to match local strain to phase transformation and possible
detwinning modes of martensite variants. In situ observations of 50µm by 50µm field of
interest indicate prominent martensitic detwinning during uniaxial tension and martensite
to austenite phase transformation upon temperature increase. Plastic deformation
occurred post shape memory effect suggested by band like residual strain. The role of
microstructure and possible mechanism of detwinning of martensite and martensite to
austenite phase transformation will also be discussed.
285
Benchmarking the Accuracy of Inertial Measurement Units for Estimating
Kinetic Energy
Jessandra Hough1, Ryan S. McGinnis1, N.C. Perkins1
1
Newly developed miniature wireless inertial measurement units (IMUs) hold great promise
for measuring and analyzing multibody system dynamics. This relatively inexpensive
technology enables non-invasive motion tracking in broad applications, including human
motion analysis. In this study, we point to the potential use of wireless IMUs for
measuring the kinetic energy of human motion. Knowing the kinetic energy of the human
body, and its decomposition into the kinetic energies of the major body segments, has
tremendous value in a wide range of applications. Significant challenges thwart our ability
to measure segmental kinetic energy in real (non-laboratory) environments. The aim of
this research is to address these challenges by advancing the use of an array of
miniaturized body-worn IMUs for estimating segmental kinetic energy. The study is
conducted on a well-characterized mechanical system, a double pendulum, which also
serves as an apt model for the lower or upper extremities. A two-node IMU array is used
to measure the kinematics of each segment as input to computations of segmental kinetic
energy. The segments are also instrumented with two high-precision optical encoders
that provide the truth kinematic data for comparison. The segmental kinetic energies
estimated using the IMU array remain within 1.1% and 2.8% of the kinetic energies
estimated using the optical encoders for the top and bottom segments, respectively, for
the freely decaying pendulum oscillations considered. These promising results point to
the future development of body-worn IMU arrays for real-time estimates of segmental
kinetic energy for health, sports, safety and military applications.
286
Quantitative Measures of Microstructural Phase Transformation in NickelTitanium
Michael Kimiecik1, J. Wayne Jones1, Sam Daly1,2
1
2
Martensitic transformation in superelastic Nickel-Titanium has been successfully
quantified and analyzed at the microstructural length scale. A novel approach enables the
determination of full-field, in situ surface displacements that are used as an indicator of
the extent of microstructural martensitic transformation. The resulting high spatialresolution displacement fields provide point-by-point information on the evolution of local
deformation within individual grains as the macroscopic transformation front progresses,
and enable analysis of the martensite phase fraction inside grains that results from
interactions between the macroscopic front and microstructural features. The
heterogeneous structure of the martensite band, including areas of elevated strain from
plastic deformation and areas of low strain from retained austenite, will be given special
attention. The high-spatial resolution strain data is related to the underlying
crystallographic information, provided by Electron Backscatter Diffraction (EBSD), in order
to quantify and elucidate microstructural effects on both small-scale and meso-scale
phase transformation. Ultra high-resolution experiments focusing on individual
microstructural elements, such as single grains, will also be discussed.
The authors gratefully acknowledge the financial support of the US Department of
Energy, Office of Basic Energy Sciences (contract No. DE-SC0003996 monitored by Dr.
John Vetrano), who funded the in situ experiments and analysis detailed in this paper.
The authors would like to acknowledge Mr. Adam Kammers for his development of the
SEM-DIC methodology used in this work, and Mr. Jared Tracy for his experimental
assistance.
287
Experiments and Inverse Analysis for Non-linear Viscoelastic (NLV)
Properties Determination
Nhung Nguyen1, Alan Wineman1, Anthony Waas2
1
2
This work presents a methodology to extract NLV properties with applications to liquidfilled polymeric capsules and biological cells. Being used widely in the pharmaceutical
industry, the performance of polymeric capsules is highly dependent on their mechanical
properties, which govern the deformation during interactions inside the body. Thus,
understanding the capsule’s mechanical behavior could be used in improving the
product’s efficiency like predicting the bursting time for drug release. For this purpose, the
mechanical responses of fluid-filled polymeric capsules are investigated using tests in
which they are compressed between two flat, rigid, parallel plates. The bottom one is a
transparent prism allowing the measurement of contact area during the compression
process. The force-displacement-time response and contact area are used for the
property extraction. The test is simulated using finite element (FE) in which the capsule
material is modeled by a NLV constitutive relationship as suggested by the experimental
data. An inverse analysis based on surrogate modeling and a Kriging estimator is also
employed to automatically and efficiently determine NLV parameters for the capsule wall.
This approach is also applied to biological cells in which experimental data is obtained
utilizing atomic force microscopy. Cells are indented by spherical probes and force-time
responses are recorded. The indentation experiment is also simulated using FE and the
same inverse technique is applied to extract cell’s NLV properties. Such properties could
be used to give more insight into the design of synthetic cells or investigating the
possibility of using mechanical properties as biomarkers for disease.
288
Modeling, Capacitive Sensing and Optimal Filtering Algorithm Design for
High-Precision Actuation of a Rotary Micro-Stage
Jinhong Qu1, Kenn Oldham1
1
The goal of this work is to control a magnetoelastic rotary stage fabricated by MEMS
technology, which can provide continuous rotation under large payload. Target
specifications are 1000 degree/s over arbitrary angles with a resolution less than ±10
milli-degree. The first step in controller design towards achieving this behavior is to
develop a dynamic model of the magnetoelastic rotary stage motion. A differential
capacitive sensor, with accurate detection of several fixed points, is then designed for the
stage to capture the rotation that will eventually be used for feedback control. The
dynamic model of the stage is modeled in two parts: a collision model and a transient
model. An analytical solution has been found and validated by experiments. Meanwhile, a
capacitive sensor, with a capacitive readout circuit to transfer the signal, has been
designed to sense the motion of the stage using gold electrodes placed on the stage with
a symmetric geometry. Motion at several fixed angles detected by the electrodes with less
error than standard analog sensing, which should increase the accuracy of the entire
motion detection scheme. The controller will be designed based on the behavior of the
stage motion and capacitive sensor. Given the behavior of the system, a Kalman filter and
a Kalman smoother will be re-designed to reduce the noise of the analog signal. Current
challenges that need to be considered include state-dependent noise from sensor and offaxis stage wobble.
This work is supported by DARPA. Other collaborators not listed as co-authors: Jun Tang,
Scott Green, Yogesh Gianchandani, Becky Peterson, Biju Edamna, Bongsu Hahn, Khalil
Najafi, Erkan Aktakka.
289
Design of Materials for Blast Resistant Armor
Tanaz Rahimzadeh1, Ellen Arruda1,2,3, Michael Thouless1,4
1
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI
3
Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, MI
4
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI
2
In the current US military, the Advanced Combat Helmet (ACH) is one of the main pieces
of equipment used for head protection against blast and ballistic loading. Considering the
current ACH design, being near an explosion (blast) can still produce a range of injuries
called Traumatic Brain Injury (TBI). TBI is generally considered as the signature injury of
the current military conflicts involving costly and life-altering long-term effects. Hence,
there is an urgent need to battle this problem first by gaining a better understanding of the
mechanisms responsible for the blast-induced TBI and second by designing/developing
more effective head protection systems. In the present work, blast-induced TBI were
reviewed from biological point of view and linked to several influencing mechanical
parameters. Then several alternatives for the mitigation of the defined influencing
mechanical parameters were explored such as impedance mismatch, energy dissipation
through plasticity in irreversible crushable foams and finally stress relaxation concept and
frequency tuning in visco-elastic materials. Using a systematic design optimization
methodology, some potential multilayered ACH designs were proposed and their TBI
mitigation capabilities were investigated using Finite Element Analysis (FEA).
This work was funded, in part, by ONR.
.
290
Modeling Crack Propagation in Polycrystalline Alloys using Variational
Multiscale Cohesive Method
Shang Sun1, Veera Sundararaghavan2
1
2
Crack propagation in polycrystalline grains is analyzed using a novel multiscale
polycrystalline model. This model combines reduced order descriptors of microstructures
with explicit representation of polycrystals at critical areas (eg. crack tips). For the critical
areas, refined meshes are employed to discretize each crystal. The crack propagation in
the microstructure is calculated using the variational multiscale cohesive method which
allows for arbitrary intergranular and transgranular crack paths. The computational load is
reduced substantially by combining probabilistic representation of the macroscale
problem with exact resolution of the crystals at the crack tips. Examples of intergranular
failure and inter and transgranular failure problems are demonstrated, showing
exceptional mesh convergence and efficiency of the numerical approach.
291
Recrystallization in Binary Alpha Titanium Alloys
Anna Trump1, John Allison2
1
Recrystallization can have a significant impact on the mechanical properties of metals
and development of recrystallization models is an important element for any Integrated
Computational Materials Engineering (ICME) capability for wrought structural metals.
Throughout the forging process, the material is deformed and reheated multiple times,
therefore it is important to understand exactly when and how much recrystallization is
occurring during the process. Determining a relationship between the process variables
and the amount of recrystallization allows for the prediction of the resulting mechanical
properties of the material. A first step for producing such a model is to develop a high
quality, quantitative experimental understanding which in turn requires development of
accurate and efficient way to quantify recrystallization. This poster compares various
methods for quantifying the percent of recrystallization in a binary alpha titanium alloy.
These methods include hardness testing, optical microscopy and electron backscatter
diffraction (EBSD). The fractional softening method relates changes in the hardness of a
material to the amount of recrystallization. Recrystallization decreases the amount of
dislocations in the material and therefore decreases the hardness. The optical point
count method uses optical microscopy to visually determine what regions of the material
are recrystallized. Grain orientation spread is an EBSD method that measures the local
misorientation within each grain. A deformed grain will have a higher local misorientation
than a recrystallized grain because of dislocations which induce lattice rotations. The
advantages and disadvantages of each method are discussed.
The authors acknowledge support of Office of Naval Research under Grant N00014-12-10013.
292
Progressive damage and failure analysis for 3D woven composites
subjected to flexural loading
Dianyun Zhang1, Anthony M. Waas1, and Chian-Fong Yen2
1
2
Department of Aerospace Engineering, University of Michgian
Army Research Laboratory
Textile composites are increasingly attractive for industrial applications. A 3D hybrid
textile composite has been recently manufactured by weaving three different fibers
(carbon, glass, and Kevlar) into a single dry preform, which is subsequently impregnated
and cured using a Vacuum Assist Resin Transfer Molding (VARTM) process to form a
solid panel. Previous studies in 3D textile composites have shown that this type of
material has improved mechanical performance and increased resistance to
delamination.
A new computational multi-scaling approach is proposed to study the flexural response of
a quasi-statically loaded 3D textile composite. For the experimental work, three-point
bend tests were performed on a hydraulically activated machine at a loading rate of
1mm/min. The experimental observations suggest that the geometrical characteristics of
the textile reinforcement play a key role on the mechanical response and progressive
failure mechanism of this type of material. A computational model that reflects the detail
of textile architecture and incorporates a damage constitutive law has been used to
successfully capture the experimental results. The model has been implemented using a
new multi-scaling approach in which the unit cell computations, carried out in closed form,
are based on extreme values (as opposed to average values) to drive damage and
failure. The resulting computational scheme is shown to be very fast and results in a highfidelity and efficient computational model for assessing structural integrity and damage
tolerance of textile fiber composites.
The authors are grateful for the financial support from Army Research Laboratory.
293
Nuclear Engineering and
Radiological Sciences
Session Chair: Bruce Pierson
294
Coupling of 1D System Code to 3D Computational Fluid Dynamics Code
Timothy P. Grunloh1, Victor E. Petrov1, Annalisa Manera1
1
Nuclear Engineering and Radiological Sciences, University of Michigan
In order to properly simulate and, by extension, understand the behavior of a nuclear
power plant (NPP), a large number of physical phenomena with widely varying degrees of
complexity must be appropriately modeled. Hydrodynamically, the examples of simple
pipe flow and 3D mixing in the lower plenum juxtaposed represent the range of
complexity present in a NPP simulation. A similarly wide range of tools exists to cope with
these issues. Computational Fluid Dynamics (CFD) codes such as STAR-CCM+ excel at
the 3D simulation of fluid flows in complex geometries whereas system codes such as
TRACE excel at quickly simulating less complex flows found in NPPs.
It is the goal of this project to unite these two codes, exploiting their respective
advantages to accurately and efficiently simulate important physical phenomena. This
work has developed a coupling infrastructure that facilitates several types of interfaces on
simple geometries as a demonstration of principle, laying the groundwork for extension to
more complex and useful coupling configurations. The two primary philosophies of
coupling (separate and overlapping domains) are examined in this context, with emphasis
currently on explicit temporal discretization. Multiple scenarios, transient and steady state,
have been simulated. The results of this work show that coupling between the codes is
possible and provide a route through which more useful, and complex, coupled
simulations will be realized.
This work has been funded in part by a Nuclear Engineering University Programs (NEUP)
fellowship and by NRC-HQ-12-G-04-0083 grant.
295
First Efforts of Hybrid Monte Carlo Method in 2D Neutron Transport
Changyuan Liu1, Prof. Edwards Larsen1
1
Nuclear Engineering and Radiological Science, University of Michigan
The Monte Carlo Method in neutron transport had a long history dated back to the first
application of Digital Computer and the first simulation of extracting atomic powers.
However with more demanding of the accuracy of atomic powered reactor simulation,
problems with random fluctuation nature of the solution from Monte Carlo became
intolerable. Later in 1990, the Coarse Mesh Finite Feedback (CMFD) method originally
developed for the deterministic methods had been migrated and adapted to accelerate
and reduce the noise levels in Monte Carlo Solver; nevertheless the results were not
satisfactory as the reactor designer zoomed in details of the reactor. Nowadays the rapid
growth of computation power makes a greater demand of a better. As a result, in the past
decade, Professor Larsen had developed several so-called Hybrid Monte Carlo Methods,
namely, which combine the deterministic and Monte Carlo together. As previous efforts of
Dr. Yang and Wolters had shown, advantageous progresses could be made in one
dimensional model problems.
In this article, the author had developed a better method and took the first endeavors into
the two dimensional problems, where only CMFD accelerations exist. Those new
methods are called the Generalized Coarse Method Finite Difference Methods (GCMFD).
We will show that with these new methods built on a triangular mesh will further reduce
random fluctuation than CMFD.
Moreover the efforts will demonstrate the application of a more advanced data structure
for 2D geometry, borrowing ideas from CAD software, which will be promising for the
future neutrontransport software development.
296
Characterization of Detection Limits Using Mock Waste Matrices in a 3He
Passive Drum Counter for Plutonium Waste Verification
Marc Gerrit Paff1,2, Bent Pedersen2, Jean-Michel Crochemore2, V. Canadell Bofarull3
1
Department of Nuclear Engineering and Radiologial Sciences, University of Michigan
Nuclear Security Unit, Institute of Transuranium Elements, Joint Research Centre Ispra, European
Commission, Ispra, Italy
3
Nuclear Safeguards-Unit E1, Directorate General Energy, European Commission, Luxembourg,
Luxemburg
2
Waste streams from the fuel cycle or research facilities may contain measurable
quantities of plutonium that must be accounted for under international safeguards
agreements. Inspectors must perform measurements to verify operator declared
plutonium masses within waste matrices potentially containing sub-gram quantities of
plutonium. Neutron coincidence measurements are a standard tool to measure 240Pu
content due to its high spontaneous fission rate. Given prior knowledge of isotopics, total
plutonium mass can be estimated. For such measurements, the European Commission's
Joint Research Centre (JRC) maintains, tests and upgrades a 3He drum monitor for
deployment to European nuclear facilities at the request of EURATOM. This drum monitor
consists of 148 standard 3He tubes in a 4pi geometry for passive neutron coincidence
measurements using a shift register and standard INCC software. The neutron drum
monitor is designed and optimized to handle standard 55 gallon conditioned waste drums
of low plutonium content. This nondestructive measurement tool recently underwent
extensive electronic and structural refurbishments. Before redeployment, the passive
neutron detection system must undergo an extensive measurement campaign to
ascertain its limits of detection of plutonium in a variety of waste matrices. For this
purpose, mock waste matrices were produced. These consist of concrete filled standard
waste drums. A number of cavities at different distances from the drum center allow for a
variety of source locations to be tested. Plutonium metal and oxide samples ranging from
milligram to gram quantities were measured during this campaign.
“This research was performed under appointment to the Nuclear Nonproliferation
International Safeguards Fellowship Program sponsored by the National Nuclear Security
Administration’s Next Generation Safeguards Initiative (NGSI).”
297
A Quantitative Comparison of Analog and Digital Pulse-ShapeDiscrimination Systems for Organic Scintillators
Charles S. Sosa1, Marek Flaska1, and Sara A. Pozzi1
1
Department of Nuclear Engineering and Radiologial Sciences, University of Michigan
Organic scintillators require accurate discrimination of neutrons and gamma rays when
used in mixed neutron/gamma-ray radiation fields. Pulse-shape-discrimination (PSD)
systems are used in synergy with organic scintillators to identify the radiation type. This
paper compares PSD performance of a digital, charge-integration PSD system (based on
a CAEN V1720 waveform digitizer) against a state-of-the-art, analog, zero-crossing PSD
system (Mesytec MPD-4). The optimization of the MPD-4 analog PSD system was
successfully completed and verified using figure of merit (FOM) comparison studies for
different combinations of settings, to produce the best possible particle discrimination.
The MPD-4 was then compared against a state-of-the-art digital-PSD system using FOM
studies. The same equipment and sources were maintained for all measurements.
Measurements were performed using an organic liquid scintillator (EJ-309) coupled with a
photo-multiplier tube (ETL-9821B). A Cf-252 spontaneous-fission source was used to
provide neutrons and gamma rays for the measurements. From the FOM results, it was
determined that the performance of the digital-PSD system is slightly better than that of
the analog-PSD system. Future work will include various detector gains to potentially
further improve the PSD performance of the MPD-4.
298
Axial Solvers for the 2D/1D Implementation in MPACT
Shane Stimpson1, Benjamin Collins1, and Thomas Downar1
1
Department of Nuclear Engineering and Radiological Sciences, University of Michigan
The Michigan PArallel Characteristics-based Transport code (MPACT) has been
developed to simulate light water reactor (LWR) cores, providing sub-pin-level flux
distributions. One of the methods available is based on the 2D/1D method, which solves
the 3D neutron transport equation by coupling 2D-radial and 1D-axial transport sweepers,
usually wrapped by a three-dimensional coarse mesh finite difference (CMFD)
accelerator. This scheme is successful because most of the heterogeneity in reactors
usually exists radially, which is handled with 2D-MOC that uses an explicit geometric
representation. Axially, however, there is less heterogeneity and a homogenized
geometry can generally be used.
Up to this point, 2D/1D development in MPACT has been limited to using finite
difference axially, in which case there are no axial transport sweepers, but where
the 3D-CMFD accelerator acts as the axial solver. To capture a more accurate
representation of the axial flux profile, higher-fidelity methods are necessary. This
work explores incorporating several different axial sweeper options, including both
diffusion- and transport-based sweepers, most of which use higher-order
expansions of the source and flux to allow for larger axial mesh. These axial
solvers lighten the computation burden of requiring a large number of radial
sweepers (as is the case when using finite difference) while providing higher
fidelity axial solutions.
299
High-fidelity simulations of CRUD deposition on PWR fuel rods
using neutronics, CFD, and coolant chemistry
Daniel Walter 1, Victor Petrov1, Brian Kendrick 2, Annalisa Manera 1
1
2
Department of Nuclear Engineering and Radiological Sciences, University of Michigan
Theoretical Division, Los Alamos National Laboratory
The development of computational tools to predict CRUD deposition on commercial
nuclear pressurized water reactor (PWRs) fuel rods within the DOE CASL project is
ongoing. CRUD causes two primary operating issues: CRUD induced power shift (CIPS),
and CRUD induced localized corrosion (CILC). The coupling of three physics, including
neutronics, thermal-hydraulics, and coolant chemistry is necessary to accurately predict
CRUD deposition and boron hideout. Several simulations have been performed including
a single pin cell, a 4x4 sub-assembly, and a 5x5 sub-assembly. Due to the fidelity of the
thermal-hydraulic characteristics that must be captured, computational fluid dynamics
(CFD) is a requirement. However, the computational cost of CFD is very high and thus
the current simulation effort is on small sub-assemblies. In this work, the most recent
simulations and sensitivity studies will be discussed, which includes a 5x5 sub-assembly
simulation using coupled CFD and coolant chemistry with STAR-CCM+ and MAMBA,
respectively. Additionally, in this work it is shown that the azimuthal variation of the power
distribution within a fuel rod may not significantly impact the locations of “hot spots”, or
regions of highest temperature. In reality, the thermal-hydraulics, specifically the turbulent
flow induced by spacer grid mixing vanes, more significantly controls the locations of the
hot spots. Time stepping studies (frequency of data updates) on the feedback between
CFD and coolant chemistry codes was also investigated. It was shown that, in general,
coarse ~50 day time steps are sufficient to accurately predict CRUD and boron mass, as
long as the precipitation of boron is not occurring.
This work was funded, in part, by the Consortium for Advanced Simulation of Light Water
Reactors (CASL).
300
Richard and Eleanor Towner
Award for Outstanding Ph.D.
Research Competition
301
Enhancing Vision via Stochastic Computing
Armin Alaghi1 and John P. Hayes1
1
Vision chips, i.e., chips that have image sensors integrated with an image processing
circuit, have several interesting applications such as human vision restoration and
millimeter-scale stand-alone sensors. The area/power constraints associated with these
applications are so demanding that make conventional digital design approaches
unattractive or sometimes impossible, especially for real-time image processing. We
show that stochastic computing is a solution to this problem. Stochastic computing is an
unconventional technique which processes data in the form of bit-streams that denote
probabilities. It can implement complex operations by means of simple logic circuits. We
demonstrate that the simplicity of stochastic circuits, allows massively parallel processing
of images in real-time. We also show that stochastic circuits are very noise tolerant, a
property that is becoming ever important as the electronic technology advances.
302
Integrated Microfluidic Platform for Immunophenotyping of Subpopulations of
Immune Cells
Weiqiang Chen1, Nien-Tsu Huang1, Timothy T. Cornell2, Thomas P. Shanley2, Katsue
Kurabayshi1,3, Jianping Fu1,4
1
Department of Mechanical Engineering,
Department of Pediatrics and Communicable Diseases,
3
Department of Electrical Engineering and Computer Science,
4
Department of Biomedical Engineering, University of Michigan, Ann Arbor
2
An accurate measurement of the immune status in patients with immune system
disorders is critical in evaluating the stage of diseases and tailoring drug treatments. The
functional cellular immunity test is a promising method to establish the diagnosis of
immune dysfunctions. The conventional functional cellular immunity test involves
measurements of the capacity of peripheral blood mononuclear cells to produce proinflammatory cytokines when stimulated ex vivo. However, this “bulk” assay measures the
overall reactivity of a population of lymphocytes and monocytes, making it difficult to
pinpoint the phenotype or real identity of the reactive immune cells involved. In this
research, we developed an integrated microfluidic immunophenotyping assay (MIPA)
platform that can perform efficient isolation, enrichment, and enumeration of peripheral
blood mononuclear cells (PBMCs) as well as subpopulations of immune cells from minute
quantities of human blood samples, and simultaneously perform quantitative
measurements of multiple inflammatory cytokines secreted from these isolated immune
cells using a no-wash, homogeneous chemiluminescence ("AlphaLISA") assay.
303
High Efficiency Single Cell Capture Chip by Using Herringbone Vortices for
Small Sample Analysis
Yu-Heng Cheng1, Yu-Chih Chen1, Patrick Ingram2 and Euisik Yoon1,2
1
Dept. of Electrical Eng. and Computer Science, University of Michigan, Ann Arbor, MI, USA
Dept. of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
2
In this work, we report a high efficiency single cell capture scheme utilizing herringbone
vortices for small assay samples incorporating only tens of cells. Single cell analysis has
become increasingly important in cancer biology where rare sub-populations have been
shown to have a large clinical impact. Cancer stem cells, for instance, have a strong
potential for self-renewal and metastasis, driving disease progression. Circulating tumor
cells (CTCs) can be found in patient blood and present an opportunity for cancer
prognosis. However, due to the scarcity of such populations, only small numbers can be
acquired for analysis. Thus, it is important to increase the capture efficiency of single cell
platforms. In this design, we used herringbone vortices to induce hydrodynamic cell
focusing to significantly enhance the capture efficiency. Three different designs were
tested: no herringbone, cell focusing herringbone, and cell diverting herringbone. The cell
focusing herringbone showed 70% cell capture efficiency, which is twice of the efficiency
of no herringbone design. In addition, cell trajectories are also tracked in three designs. It
shows that, due to the nature of the laminar flow, in the microwell without herringbone
structures, the cell trajectories diverges when the cross-section of microfluidic channel is
abruptly enlarged inside the microwell, limiting the capture efficiency. On the other hand,
the turbulence generated by cell focusing herringbone can guide the cells back to the
center to facilitate cell capture. It demonstrated the feasibility of herringbone cell-focusing
capture scheme for analysis of small samples that contain tens of cells.
304
Supervisory Control for Collision Avoidance in Vehicular Networks with
Imperfect Measurements
Eric Dallal1, Alessandro Colombo2, Domitilla Del Vecchio3, Stéphane Lafortune1
1
Department of Electrical and Computer Engineering, University of Michigan
Department of Mechanical Engineering, Politecnico di Milano
3
Department of Mechanical Engineering, Massachusetts Institute of Technology
2
We consider the problem of collision avoidance at road intersections in vehicular
networks in the presence of uncontrolled vehicles, a disturbance, and measurement
uncertainty. Our goal is to construct a supervisor of the continuous time system that is
safe (i.e., avoids collisions), nonblocking (i.e., all vehicles eventually cross the
intersection), and maximally permissive with respect to the discretization, despite the
presence of a disturbance and of measurement uncertainty. We proceed in four steps:
defining a discrete event system (DES) abstraction of the continuous time system, using
uncontrollable events to model the uncontrolled vehicles and the disturbance; translating
safety and non-blocking requirements to the DES level; solving at the DES level; and
translating the resulting supervisor back from the DES level to the continuous level. We
give sufficient conditions for this procedure to maintain the safety, non-blocking and
maximal permissive properties as the supervisor is translated back from the DES level to
the continuous level. Prior work on this problem based on similar abstractions assumes
perfect measurement of position. Our method for handling measurement uncertainty is to
introduce measurement events into the DES abstraction and then to compute the
observer of the DES abstraction and the supremal controllable solution of the DES
supervisory control problem.
Research supported in part by NSF grant CNS-0930081.
305
Surface Dynamics of Miscible Polymer Blends
Bradley Frieberg1, Jenny Kim2, Suresh Narayanan3, Peter F. Green1,2,4
1
Department of Macromolecular Science & Engineering, University of Michigan, Ann Arbor, MI
Department of Macromolecular Science & Engineering, University of Michigan, Ann Arbor, MI
3
Advanced Photon Source, Argonne National Laboratory, Argonne, IL
4
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI
2
In the case of thin polymer films, the interactions between the polymer and an interface
can have strong influences on the physical properties, including surface induced structure
and dynamics which can differ significantly from the bulk material. In thin film polymerpolymer mixtures the component with the lower surface tension will preferentially
segregate to the free surface to form a wetting layer. Due to this effect, the free surface of
a polymer film can have a different composition than the average in the bulk material
giving it significantly different properties. With the use of X-ray photon correlation
spectroscopy (XPCS) we show that the dynamics of poly(vinyl methyl ether) (PVME)
chains at the free surface of polystyrene (PS)/PVME thin film mixtures is 2 orders of
magnitude faster than the PVME chains in the bulk. Furthermore, the thickness of the
wetting layer and consequently the viscosity is demonstrated to be significantly influenced
by the overall film thickness. Such enhancements in the surface dynamics manifest from
the differences between the local compositions of the blend near the free surface and the
bulk.
Support from the Department of Energy, Office of Science, Basic Energy Sciences,
Synthesis and Processing Program, DOE no. DE-FG02-07ER46412 is gratefully
acknowledged. Use of the Advanced Photon Source was supported by the U. S.
Department of Energy, Office of Science, Office of Basic Energy Sciences, under
Contract No. DE-AC02-06CH11357.
306
Using laser accelerated electrons for femtosecond electron diffraction
application
Zhaohan He1, Benoît Beaurepaire2, Victor Malka2, Jérôme Faure2, John Nees1, Bixue
Hou1, Karl Krushelnick1 and Alexander G. R. Thomas1
1
Center for Ultrafast Optical Science, University of Michigan Ann Arbor, Michigan, USA
Laboratoire d’Optique Appliquée, ENSTA-CNRS-Ecole Polytechnique, Palaiseau, France
2
The development of tools to take ultrafast snapshots (at femtosecond time scale) of
matter at the atomic scale has been a significant endeavor in the scientific community for
understanding fundamental processes in biology, chemistry, material science and solidstate physics. Much progress has been made thanks to advances in ultrafast laser
technology and the advent of X-ray free-electron laser light sources. Using electrons as
probe is a cost-effective alternative to X-ray with unique advantages, such as the larger
cross section for elastic interaction with matter, less radiation damage to samples and the
possible higher spatial resolution due to the shorter wavelength of electron. However,
achieving a time resolution better than 100 fs remains a great challenge for conventional
photocathode based femtosecond electron source due to problems such as rf jitter and
space charge effect. We develop a novel electron source based on laser-plasma
wakefield accelerator using a high-repetition-rate femtosecond laser system. The inherent
short bunch duration and perfect synchronization with the optical pump makes this source
a promising candidate for ultrafast electron diffraction (UED) applications. We will present
single-shot electron diffraction result from a crystalline gold foil in a proof-of-principle
experiment to demonstrate the sufficient beam charge and quality. Simulations show that
the accelerated electrons are energy chirped in time, which enables electron bunch
compression for UED or utilizing the momentum-time correlation by streaking techniques
for time-resolved experiments.
307
Engineering the elasticity of soft colloidal materials through surface
modification and shape anisotropy
Lilian C. Hsiao1, Richmond S. Newman1, Kathryn A. Whitaker2, Eric M. Furst2, Sharon C.
Glotzer1, Michael J. Solomon1
1
2
Department of Chemical Engineering, University of Michigan, Ann Arbor MI
Department of Chemical Engineering, University of Delaware, Newark DE
Designing complex fluids has always involved the arduous manipulation of systemspecific parameters. Recently, we developed a general correlation to predict the flow
behavior of a range of soft matter based on their microstructure. By applying the
framework of structural rigidity at the macroscale (bridges, buildings, domes) to the
microscale, we are able to explain the nonlinear elasticity of colloids flowing at high rates
that are typical of industrial processing. In particular, we find that we can design colloidal
gels with better mechanical properties and stability without resorting to a greater quantity
of materials, simply by incorporating particles with different shapes, sizes, and roughness.
Biphasic particles with metallic facets have also been proposed to provide extraordinary
structural strength due to their interaction anisotropy. We test these ideas by synthesizing
monophasic and biphasic colloids of controlled roughness in various ellipsoidal shapes,
dispersing the particles in refractive-index matched solvents, and inducing self-assembly
and gelation with a measurable and tunable depletion attraction. To quantify their flow
properties, rheological measurements are carried out in conjunction with microscopy
experiments. Consider this scenario: a pharmaceutical product encapsulated in a
viscoelastic gel is transported from a factory to a hospital, but the formulation phase
separates after a bumpy ride in a truck, rendering the drug useless. Our work shows that
this type of problem can be mitigated by applying the principle of structural rigidity to
material design; for example, engineers can incorporate smaller ellipsoidal particles to
increase yield stress without a significant increase in the production cost.
308
A reduced-order model of Titanium alloy for the control of microstructuresensitive material properties
Abhishek Kumar1, Veera Sundararaghavan1
1
Department of Aerospace, University of Michigan Ann Arbor
A crystal-plasticity based constitutive model for the large deformation of polycrystalline materials with
hexagonal crystal structure deforming by mechanism of slip only(no twinning) is developed. To
account for the infinite degrees of freedom of microstructural features, a model reduction on the microscale is introduced. Reduced-order models are developed to model the evolution of microstructure
described by an orientation distribution function using a infinite element discretization of the orientation
space. Novel design problems are introduced for the control of microstructure based on realistic
polycrystalline plasticity.
Specifically, a gradient based optimization framework is introduced using a multi-length scale
continuum sensitivity method(CSM). The model reduction is extended to the sensitivity analysis and is
a key element for the success of computational design of deformation processes. Numerical examples
that highlight the benefits of the continuum sensitivity method and model reduction are presented.
309
Smart membranes for energy-efficient separation of liquid mixtures
Gibum Kwon1, Arun K. Kota1, Joseph M. Mabry2, and Anish Tuteja1,3#
1
Rocket Propulsion Division, Air Force Research Laboratory, Edwards Air Force Base
3
Macromolecular Science and Engineering, University of Michigan
2
In this work, we have developed the next generation of smart membranes that can
separate virtually all types of liquid mixtures using gravity alone. These counter-intuitive,
liquid-responsive, smart membranes were designed by systematically tailoring the surface
chemistry and the surface texture. The developed membranes can separate a range of
different immiscible liquid mixtures, including all types of oil-water mixtures, with greater
than 99.9% separation efficiency, using gravity alone. We also demonstrated continuous
separation of oil-water emulsions for over 100 hours without a decrease in flux. Further,
we developed a technique that combines liquid-liquid extraction and our smart
membranes to separate numerous miscible liquid mixtures. We have utilized this
technique for separating a wide variety of commercially relevant mixtures, including for
the removal of sulfur compounds from both gasoline and diesel to less than 1 part per
million. We also demonstrated the separation of alcohol-oil azeotropes and recovery of
highly pure oils using this technique. Since the separation uses only gravity, it is an
extremely energy-efficient and cost-effective methodology. We also developed another
smart separation methodology that uses an electric field as a trigger to separate oil-water
mixtures, on-demand. We anticipate that our smart membranes and separation
methodology will have a wide range of commercial applications including clean up of
marine oil-spills, wastewater treatment, separation of numerous commercially relevant oilwater emulsions, biofuel separation and recovery of oils, plastics recycling and fuel
purification.
310
Improved Embryo Developmental Competence from Reduced Osmotic
Stress by Gradual Shrinkage Rate Vitrification
David Lai1,2, Jun Ding2,3, George W. Smith4, Gary D. Smith2,3, Shuichi Takayama1,2, …
1
Reproductive Sciences Program, University of Michigan
3
Department of Obstetrics and Gynecology, University of Michigan
4
Department of Physiology, Michigan State University
2
Treatment for cancer involves non-target specific radio- and chemotherapy that leave
female patients with high risk of permanent infertility. With increasing cancer survival
rates, oncofertility preservation has become a significant quality of life issue for young
cancer survivors. Vitrification has become the preferred method for preservation of human
oocytes due to higher survival rates and time efficiency. Current osmotic stress theories
deal only with cryosurvival (percentage of cell death) and minimum cell volume, however
the preservation of oocytes and zygotes necessitates the additional consideration of cell
health and developmental competence. A major cause of sub-lethal osmotic stress is by
high cell shrinkage rates for oocytes and zygotes. The new mechanism for osmotic stress
was first derived mathematically using Kedem-Katchalsky equations and validated using
a microfluidic device that enables a more gradual shrinkage rate not possible with manual
cryoprotectant exchange. Importantly, the cell loading/withdrawal port allowed for 100%
recovery of cells (n=474) from the device in a manner that enabled actual vitrification after
the cryoprotectant agent exchange. Bovine oocytes vitrified with lower osmotic stress had
24.8% higher lipid retention than oocytes vitrified by manual pipetting (n=17, n=18).
Murine zygotes vitrified with lower osmotic stress also have superior embryo
developmental competence with more blastomeres (98±3 blastomeres, n=46) after 96h
embryo culture compared to manual pipetting controls (89±3 blastomeres, n=35).
We thank NIH GM 096040 for funding support.
311
Compressive Sensing Methods for Reducing Resource Requirements in
Wireless Bridge Monitoring Systems: Validation on the Telegraph Road
Bridge
Sean M. O’Connor1 and Jerome P. Lynch1
1
Wireless monitoring systems represent a cost-effective alternative to traditional tethered
monitoring systems for monitoring the performance and health of bridges. While great
advances have recently been made in wireless sensing technology, wireless sensors still
suffer from two major limitations: limited communication bandwidth and a dependence on
batteries. Data compression is one potential solution for reducing the amount of data
required for communication in wireless sensor networks. By compressing data, the
communication requirements of a wireless sensor can be lowered leading to improved
communications and lower power requirements. A new approach to compression called
compressive sensing offers even greater benefit by reducing the amount of sensor data
required for sampling. Specifically, sub-Nyquist asynchronous sampling can be used to
reduce the amount of data collected before transforming the data to a sparse
representation with near perfect reconstruction potential. In this study, a compressive
sensing framework is implemented within a wireless sensor network deployed to monitor
the response of operational bridge structures. The paper reports on the implementation
of the proposed compressive sensing-based wireless monitoring system on the Telegraph
Road Bridge located in Monroe, MI. Field implementations of compressive sensing
schemes in wireless SHM systems have been challenging due to the lack of commercially
available sensing units capable of sampling methods (e.g., random) consistent with the
compressive sensing framework, often moving evaluation of compressive sensing
techniques to simulation and post-processing. The research presented here describes
actual implementation of a random sampling scheme to the Narada wireless sensing unit.
Sub-sampled data is communicated to the wireless monitoring system base station where
a matching pursuit approach is employed to reconstruct the original bridge signal for
subsequent data analysis. The study reports on the reduction in communication
requirements for the wireless monitoring system in addition to the amount of energy
saved through compression.
312
The Influence of Moisture and Gravity Wave Drag Parameterizations in
Idealized Simulations of the Quasi-Biennial Oscillation
Weiye Yao1, Christiane Jablonowski1
1
Department of Atmospheric Oceanic and Space Sciences, University of Michigan
The Quasi-Biennial Oscillation (QBO) can be characterized as a downward propagating
wind regime that periodically changes the equatorial zonal wind from westerlies to
easterlies in the tropical stratosphere. The QBO is mainly generated and influenced by
vertically propagating gravity waves. The main difficulty in simulating the QBO with
General Circulation Models (GCM) is the representations of subgrid-scale processes,
including moist processes, which act as wave triggers and thereby impact the wave-mean
flow interactions. In this work, idealized simulations of the QBO with simple gravity wave
drag is investigated, and the influence of moisture on the QBO-like simulations is
analyzed.
In particular, the QBO-like oscillations are simulated with version 5 of the Community
Atmosphere Model (CAM 5) which has been developed at the National Center for
Atmospheric Research (NCAR). The QBO-like phenomenon is modeled with the spectral
transform semi-Lagrangian (SLD) dynamical core, which is driven by a Newtonian
temperature relaxation and Rayleigh damping. In addition, the Lindzen (1981) gravity
wave drag scheme can be activated to parameterize the unresolved effects of small-scale
gravity waves. By adding gravity wave drag, the QBO signal is strengthened. However,
the period and amplitude of the QBO signal is highly related to the tuning parameter of
the gravity wave drag. In the simulations with moisture, a simplified physics package is
used to represent sub-grid scale processes, including the surface fluxes of moisture,
sensible heat and momentum, large-scale condensation and convection
parameterization. Wave-mean flow analysis is utilized to shed light on the QBO driving
mechanisms.
313
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Volume 2013, Issue 1 - University of Michigan

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