Research Express@NCKU

Research Express@NCKU - Articles Digest
Research Express@NCKU
Volume 28 Issue 10 - April 10, 2015
[ http://research.ncku.edu.tw/re/articles/e/20150410/1.html ]
Wave Propagation and Power Flow Analysis of
Sandwich Structures with Internal Absorbers
Jung-San Chen *, Rong-Tyai Wang
Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
[email protected]
ASME Journal of Vibration and Acoustics, Vol. 136, 041003 (2014)
H
ere we study wave attenuation and power flow characteristics of sandwich beams
with internal absorbers. Two types of internal mass-spring-damper systems are
considered, namely, a conventional (Kelvin) model and a relaxation (Zener) model. We
present that the reduction in power flow can be viewed as a practical indicator for the
occurrence of energy blockage. The reduction in the power flow indicates that some
amount of energy produced by the external force can be effectively obstructed by internal
absorbers.
Sandwich structures commonly used to construct many marine composite structures are lightweight and are
efficient in taking bending loads but are relatively weak in resisting blast loads/slamming impacts. The
investigation on the dynamic behavior of sandwich structures has been a subject of extensive research for decades
[1-2].
To enhance the impact resistant strength on the sandwich structure, many researchers have focused on
adjusting the core properties, such as density, thickness, and mechanical properties[3-4]. We propose that the use of
dynamic absorbers can offer an additionally feasible technique for alleviating structural vibration due to
disturbances.
Sandwich beam with undamped absorbers
Fig. 1(a) shows the dispersion curves of the present sandwich beam. It is found that a well-developed gap
(
) is occurred. Theoretically, in this frequency range, harmonic waves cannot propagate. It is
also found that the maximum wave attenuation would be attained at the local resonance. Fig. 1(b) depicts the
power flow of the beam with undamped absorbers. It is seen that the frequency range corresponding to zero power
flow coincides with the bandgap as shown in Fig. 1(a). In other words, in the frequency gap, the energy is
forbidden from entering into the main structure. Energy produced by the external force is stored temporarily in the
internal mass and later taken out by the driving force. The mechanism of energy transfer of the present structure is
analogous to the one found in acoustic metamaterials[5].
1 of 4
Research Express@NCKU - Articles Digest
Fig. 1 (a) Real part and imaginary part of wave numbers of the sandwich beam with undamped absorbers (b)
power flow of the sandwich beam with undamped absorbers.
Sandwich beam with conventional damped absorbers
Fig. 2(a) illustrates the wave numbers of flexural mode acquired for different damping ratios. It is found that as γ
increases, the bandwidth of attenuation considerably increases; more towards to higher frequencies, but some
towards the lower frequencies as well. Also, the peak attenuation decreases and moves to higher frequencies. The
power flow of the sandwich beam with conventional absorbers is exhibited in Fig. 2(b). It is found that in the
frequency range: around 0.25 to 1.33, the power flow of such a damped sandwich beam is lower than that of the
original beam. That is to say, some amount of the energy produced by the external force is effectively blocked
from entering into the main structure. The reduction of the power flow seems to follow the extent of attenuation of
flexural wave as shown in Fig. 1(a).
Fig. 2 (a) Imaginary part wave numbers of the sandwich beam with conventional damped absorbers (b) Power flow
of the sandwich beam with conventional damped absorbers.
Sandwich beam with relaxation absorbers
The decay ratesβ, the imaginary parts of the wave number, with varying stiffness ratio N is displayed in Fig. 3. It is
2 of 4
Research Express@NCKU - Articles Digest
seen that with fixed mass ratio and loss factor, increasing the stiffness ratio N factor causes peak attenuation to
drop and the attenuation bandwidth to increase slightly. Fig. 4 shows the comparison of two damped sandwich
beams with identical mass ratio and loss factor. It is seen that if N goes to infinity, the relaxation absorbers will
behave like the conventional damped ones. On the contrary, if N goes to zero, the whole structure will act more
like the one with undamped absorbers. Apparently, for the former case, the spring connected to the dashpot
becomes too stiff to have any effect; for the latter, the dashpot is no longer connected to the sandwich beam.
Fig. 3 Imaginary part wave numbers of the sandwich beam with relaxation absorbers
3 of 4
Research Express@NCKU - Articles Digest
Fig. 4 Comparison of power flow between two damped sandwich beams
References:
1. Sayir, M. and Koller, M.G., 1986, “Dynamic Behavior of Sandwich Plates,” J. Appl. Math. and Phys., 37,
pp. 78-103.
2. Chalak, H. D., Chakrabarti, A., Ashraf Iqbal, M., Sheikh A. H., 2013, “Free Vibration Analysis of
Laminated Soft Core Sandwich Plates,” ASME J. Vib. Acoust., 135, pp. 011013.
3. Karagiozova D, Nurick G. N., Langdon G. S., Chung Kim Yuen S., Chi Y., Bartle S., 2009, “Response of
Flexible Sandwich-type Panels to Blast Loading,” Compos Sci Technol, 69, pp. 754-763.
4. Wang D., 2009 Impact Behavior and Energy Absorption of Paper Honeycomb Sandwich Panels. Int. J.
Impact Eng., 36, pp.110-114.
5. Huang, H. H., and Sun, C. T., 2009, “Wave attenuation mechanism in an acoustic metamaterials with
negative effective mass density,” New J. Phys. 11, 013003.
4 of 4
Research Express@NCKU - Articles Digest
Research Express@NCKU
Volume 28 Issue 10 - April 10, 2015
[ http://research.ncku.edu.tw/re/articles/e/20150410/2.html ]
Discrete Particle Swarm Optimization for Constructing
Uniform Design on Irregular Regions
Ray-Bing Chen1,*, Yen-Wen Shu2, Ying Hung3and Weichung Wang4
1
Department of Statistics, National Cheng Kung University, Tainan 701, Taiwan
Department of Mathematics, National Taiwan University, Taipei 10617, Taiwan
Department of Statistics and Biostatistics, Rutgers University, NJ 08854, USA
Institute of Applied Mathematical Sciences, National Taiwan University, Taipei 10617, Taiwan
2
3
4
[email protected]
Computational Statistics and Data Analysis, 72, 282-297.
E
fficient experimental design plays an important role in the study of the scientific
problem. Since the experiments may have high-dimensional inputs and be costly, instead of
running the experiments over a dense grid of input configurations, uniform design (Fang,
1980) is one of the most widely used approaches, because uniform design possesses a
desirable space-filling property in which the design points are placed evenly over the
experimental region.
In previous literatures, uniform designs are developed mainly for regular experimental regions, such as rectangular
or hypercubic regions. However, this regular region assumption is often violated (Ranjan et al., 2008; Hung et al.,
2010; Hung, 2011). Recently, Chuang and Hung (2010) proposed central composite discrepancy (CCD) as a new
uniformity criterion for irregular regions. The idea of CCD is to divide the K-dimensional experimental region, D,
into several sub-regions and then compute both the ratio of the number of design points in each sub-region to the
total number of design points and the ratio of the sub-region volume to the overall experimental region volume. In
a uniform design, we would expect these two ratios to be close. Thus we would use this CCD criterion as our
design criterion.
In this article, the discrete version of the CCD is used, and the candidate design points are limited to a set of grid
points in the experimental region. Thus the objective can be formulated as solving an optimization problem,
minP∈Z(n,qK) CCD(P),
where Z(n, qK) is the set of all possible discrete designs with n design points. Here we focus on how to efficiently
generate the CCD-based uniform design, because the computational challenges in optimal CCD design search and
uniformity evaluations remain unsolved, especially for larger dimensionality and run sizes.
Particle swarm optimization (PSO) algorithm is a stochastic population-based heuristic that inherits the efficiency
and capability of PSO for solving high-dimensional optimization problems with multiple optima. Here we propose
a discrete version PSO (DPSO) for the CCD uniform design search problem. The complexity analysis of the
discrete CCD computation is also given. The analysis result suggests that the computational cost increases rapidly.
Parallel computing techniques based on the latest graphic processing unit (GPU) are thus applied to significantly
accelerate the CCD function evaluations. The proposed DPSO algorithm is implemented and numerical results are
compared with existing methods for two and three dimensional irregular experimental regions. Results on higher
dimension regions are also provided to demonstrate the capability of the proposed algorithms. Finally the DPSO
1 of 2
Research Express@NCKU - Articles Digest
algorithm is used to solve a data center thermal management problem (Hung et al., 2010; Hung, 2011). This
example shows how the proposed algorithms can easily be extended to handle disconnected experimental regions
with additional constraints.
Reference:
1. Chuang, S.C., Hung, Y.C., 2010. Uniform design over general input domains with applications to target
region estimation in computer experiments. Computational Statistics & Data Analysis 54, 219–232
2. Fang, K.-T., 1980. The uniform design: application of number-theoretic methods in experimental design.
Acta Mathematical Application Sinica 3, 363–372.
3. Hung, Y., 2011. Adaptive probability-based latin hypercube designs. Journal of the American Statistical
Association 106 (493), 213–219.
4. Hung, Y., Amemiya, Y., Wu, C.F.J., 2010. Probability-based latin hypercube designs for slid-rectangular
regions. Biometrika 97 (4), 961–968.
5. Ranjan, P., Bingham, D., Michailidis, G., 2008. Sequential experiment design for contour estimation from
complex computer codes. Technometrics 50 (4), 527–541.
2 of 2
Research Express@NCKU - Articles Digest
Research Express@NCKU
Volume 28 Issue 10 - April 10, 2015
[ http://research.ncku.edu.tw/re/articles/e/20150410/3.html ]
A Study on the Lineage of Taiwanese Traditional
Architectural Paintings from 1910s to 1930s
Ya-Hui Tsai, Min-Fu Hsu*
Department of Architecture, National Cheng Kung University
[email protected]
民俗曲藝, Vol.169, 89-145（2010）
T
he colored painting decoration of the traditional architectures in Taiwan has been a long
history; yet it is easy to be damaged due to humidity and the soot that deepens the difficulties
on history studies for the architectures need to be repainted regularly.
According to information gathered from written sources and field research, the development
of Taiwan’s traditional rchitectural painting can be divided into Ming-Qing period, Japanese
Colonial period, and Post-War period. Each demonstrates its unique mode under different
historical background. Judging from the amount of extant works, the period from 1910s to 1930s is the one when
development of Taiwanese architectural painting reached its peak. In this article, I intend to explore the
development of traditional architectural paintings in Taiwan during the Japanese Colonial period. Points to
investigate include, 1) state-of-the-field review, 2) lineage mapping of the painting craftsmen, 1910–1930, and 3)
analysis of the features of the craftsmen’s painting.
The research on the traditional architectural painting in Taiwan covers a wide-range of subjects, such as lineage of
schools, division of labor, contents of the paintings, construction process, material-specific techniques,
preservation and repair. Based on interviews with the craftsmen, investigations on the architecture and
corroborating materials, this article intends to build up a more complete and correct lineage map of traditional
painting craftsmen. It expects to shed light on benefit the research on the changes and traits of development of
traditional arts.
1 of 1
Research Express@NCKU - Articles Digest
Research Express@NCKU
Volume 28 Issue 10 - April 10, 2015
[ http://research.ncku.edu.tw/re/articles/e/20150410/4.html ]
miR-196a Ameliorates Phenotypes of Huntington
Disease in Cell, Transgenic Mouse, and Induced
Pluripotent Stem Cell Models
Pei-Hsun Cheng1,5, Chia-Ling Li2,5, Yu-Fan Chang1, Shaw-Jeng Tsai1,2, Yen-Yu Lai1, Anthony
W.S. Chan3, Chuan-Mu Chen4, Shang-Hsun Yang1,2,*
1
Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101,
Taiwan
2 Institute of Basic Medical Sciences, National Cheng Kung University, Tainan 70101, Taiwan
3 Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30329, USA
4 Department of Life Sciences, Agricultural Biotechnology Center, National Chung Hsing University,
Taichung 40227, Taiwan
5 These authors contributed equally to this work
[email protected]
The American Journal of Human Genetics 93, 306–312, August 8, 2013
H
untington disease is an autosomal-dominant neurodegenerative disease that is caused
by a mutation of CAG trinucleotide repeats in the huntingtin (HTT) gene. In our study, we
identified that the effect of miR-196a in Huntington’s disease (HD) and further confirm
that increased expression of miR-196a ameliorates the molecular, pathological, and
behavioral phenotypes in vitro and in vivo. In the in vitro results, overexpression of miR196a suppressed the mutant HTT aggregates in either human embryonic kidney cells or
mouse neuroblastoma cells. In the in vivo model, HD transgenic mice overexpressing miR-196a revealed the
suppression of mutant HTT and also inhibited the aggregations of mutant HTT in brains. In addition, improvement
of behavioral phenotypes also was found in HD transgenic mice overexpressing miR-196a. Furthermore, we also
confirmed that miR-196a decreased the expression of mutant HTT in HD-induced Pluripotent Stem Cells (iPSCs).
Taken together, this study suggests the potential therapeutical role of miR-196a in HD.
1 of 1