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71.
Ho Lee Taehee Kim Woojong Sim Saehoon Kim Byungki Ahn Taewon Lim Kwonpil Park 《Korean Journal of Chemical Engineering》2011,28(2):487-491
During the operation of a PEMFC, the polymer membrane is degraded by electrochemical reactions and mechanical stresses. We
investigated the effects of repeated electrochemical and mechanical degradations in a membrane. For mechanical degradation,
the membrane and MEA were repeatedly subjected to wet/dry cycles; for electrochemical degradation, the cell was operated under
open-circuit voltage (OCV)/low-humidity conditions. The repeated wet/dry cycles led to a decrease in the mechanical strength
of the membrane. When the MEA was degraded electrochemically, repeated wet/dry cycling resulted in the formation of pinholes
in the membrane. In the case of different MEAs that were first degraded electrochemically, the extents of their hydrogen crossover
currents increased due to repeated wet/dry cycling being different. Therefore, these results indicated that the membrane durability
could be evaluated by these methods of repeated electrochemical degradation and wet/dry cycles. 相似文献
72.
Moumita Mukherjee Biswanath Mukherjee Youngill Choi Kyoseung Sim Junghwan Do Seungmoon Pyo 《Synthetic Metals》2010,160(5-6):504-509
We report a copper hexadecafluorophthalocyanine (F16CuPc) based n-type organic field-effect transistor (OFET) with polymeric gate dielectrics with different physical/electrical properties. The gate dielectrics are four types of cross-linked poly(4-vinylphenol) and newly prepared poly(4-phenoxy methyl styrene) and those are characterized based on surface tension, leakage current and capacitance. The performance of F16CuPc OFETs with those gate dielectrics was compared. We found that the composition of the gate dielectrics and the interfacial interaction of F16CuPc with the gate dielectric play a decisive role in the performance of OFETs. The effect of physical/electrical properties, composition and processing condition of the gate dielectrics on the device performance was investigated. 相似文献
73.
Kazushi Yamanaka Noritaka Nakaso Takeshi Fukiura Dong Youn Sim 《Electrical Engineering in Japan》2009,168(1):41-51
A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817 相似文献
74.
Simões S. Ramos A. S. Viana F. Emadinia O. Vieira M. T. Vieira M. F. 《Journal of Materials Engineering and Performance》2016,25(10):4394-4401
Journal of Materials Engineering and Performance - Ni/Al multilayers are known to transform into NiAl in a highly exothermic and self-sustaining reaction. The fact that this reaction has a high... 相似文献
75.
In this paper, experimental and numerical studies are presented to understand why some trees close to the shoreline survived the 25 October 2010 Mentawai tsunami, while trees further inland before a steep coastal hill were all destroyed. A set of experiments were performed in a wave flume to measure the flow depths and forces acting on tree models, and the experimental results were used to verify our numerical model. Cross-shore distribution of the flow depth and the flow-induced bending moment acting on tree trunks were studied using our numerical model. Our results show that the presence of the steep hill increased both the flow depth and the bending moment acting on trees close to the steep hill, and might be an important mechanism responsible for the destruction of coastal trees. 相似文献
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Nuno Lopes Paulo Vila Real Luís Simões da Silva Jean-Marc Franssen 《Fire Technology》2010,46(1):91-108
In this paper, the structural response of stainless steel thin-walled elements submitted to fire is analysed numerically by
means of the geometrically and materially non-linear Finite Element program SAFIR, including imperfections. In order to make
these simulations, two main changes in the program were made: (i) the code was changed in order to deal with the stainless
steel 2D material constitutive law to be used with shell elements and (ii) the possibility of the program to take into account
residual stresses with shell finite elements was introduced. The stainless steel stress–strain relationship at high temperatures
was based on the one presented in part 1.2 of Eurocode 3. To model the strain hardening exhibited by the stainless steels,
using the shell element formulation, an approximation to the Eurocode 3 constitutive law was needed. Local and global geometrical
imperfections were considered in the simulations. The paper shows the influence of the residual stresses on the ultimate load-carrying
capacity of thin-walled stainless steel structural elements in case of fire. 相似文献
79.
Wan Zakiah Wan Ismail Kok Swee Sim 《International journal of imaging systems and technology》2011,21(3):280-289
Image processing requires an excellent image contrast‐enhancement technique to extract useful information invisible to the human or machine vision. Because of the histogram flattening, the widely used conventional histogram equalization image‐enhancing technique suffers from severe brightness changes, rendering it undesirable. Hence, we introduce a contrast‐enhancement dynamic histogram‐equalization algorithm method that generates better output image by preserving the input mean brightness without introducing the unfavorable side effects of checkerboard effect, artefacts, and washed‐out appearance. The first procedure of this technique is; normalizing input histogram and followed by smoothing process. Then, the break point detection process is done to divide the histogram into subhistograms before we can remap the gray level allocation. Lastly, the transformation function of each subhistogram is constructed independently. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 280‐289, 2011; 相似文献
80.