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101.
Xinyu Huang Roham Solasi Yue Zou Matthew Feshler Kenneth Reifsnider David Condit Sergei Burlatsky Thomas Madden 《Journal of Polymer Science.Polymer Physics》2006,44(16):2346-2357
The life of proton exchange membrane fuel cells (PEMFC) is currently limited by the mechanical endurance of polymer electrolyte membranes and membrane electrode assemblies (MEAs). In this paper, the authors report recent experimental and modeling work toward understanding the mechanisms of delayed mechanical failures of polymer electrolyte membranes and MEAs under relevant PEMFC operating conditions. Mechanical breach of membranes/MEAs in the form of pinholes and tears has been frequently observed after long‐term or accelerated testing of PEMFC cells/stacks. Catastrophic failure of cell/stack due to rapid gas crossover shortly follows the mechanical breach. Ex situ mechanical characterizations were performed on MEAs after being subjected to the accelerated chemical aging and relative humidity (RH) cycling tests. The results showed significant reduction of MEA ductility manifested as drastically reduced strain‐to‐failure of the chemically aged and RH‐cycled MEAs. Postmortem analysis revealed the formation and growth of mechanical defects such as cracks and crazing in the membranes and MEAs. A finite element model was used to estimate stress/strain states of an edge‐constrained MEA under rapid RH variations. Damage metrics for accelerated testing and life prediction of PEMFCs are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2346–2357, 2006 相似文献
102.
Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation 总被引:5,自引:2,他引:3
HU Jun WANG Jianlong & CHEN Rong . Laboratory of Environmental Technology Institute of Nuclear Energy Technology Tsinghua University Beijing China . State Key Joint Laboratory of Environmental Simulation Pollution Control Tsinghua University Beijing China Correspondence should be addressed to Wang Jianlong 《中国科学B辑(英文版)》2006,(2)
The application of radiation technology in the en-vironmental protection was listed as one of the mostimportant research fields by the International AtomicEnergy Agency (IAEA) for the peaceful use of nuclearenergy. It has great research value and potential appli-cation. Because of their broad-spectrum antimicrobialproperties, Cholophenols (CPs) have been used aspreservative agents for wood, paints, vegetable fibersand leather and as disinfectants. In addition, they havebeen widely employed… 相似文献
103.
Christian Maes 《Journal of statistical physics》1990,61(3-4):667-681
An anisotropic lattice gas dynamics is investigated for which particles on
d
jump to empty nearest neighbor sites with (fast) rate –2 in a specified direction and some particular configuration-dependent rates in the other directions. The model is translation and reflection invariant and is particle conserving. The space coordinate in the fast-rate direction is rescaled by –1. It follows that the density field converges in probability, as 0, to the corresponding solution of a nonlinear diffusion-type equation. The microscopic fluctuations about the deterministic macroscopic evolution are determined explicitly and it is found that the stationary fluctuations decay via a power law (1/r
d
) with the direction dependence of a quadrupole field. 相似文献
104.
Tomasz Rolski 《Queueing Systems》1989,4(1):17-26
We study single server periodic queues in the day equilibrium conditions. The following characteristics of interest are considered at time of dayt: Vp(t)-the work load, Lp(t)-the number of customers and up(t)-the departure rate. We give relationships between E[Vp(t)], E[Lp(t)] and up(t). We also prove that E[Vp(t)] < and E[Lp(t)] < provided the second moment of the service time is finite. 相似文献
105.
R. Schilling 《Journal of statistical physics》1988,53(5-6):1227-1235
A one-dimensional kinetic Ising model with Glauber dynamics subjected to a slow continuous quench to zero temperature is studied. For a rather general class of cooling schemes, described by a time-dependent temperatureT(t), the mean domain sizeL(t) is calculated along with the residual energye
res
(r) as a function of the cooling rater. If the attempt frequency =0 exp(–/kT), entering into the transition rates, is temperature dependent (i.e., the barrier is non-zero), the asymptotic growth ofL(t) is given byL()–L(t)~exp[–/kT(t)]. For this case the residual energy exhibits a power-law behaviore
res(r) ~r
/2(1 + ) forr small, where =4J/ andJ is the nearest neighbor coupling constant. For =0 and for certain cooling schemes the residual energy is zero andL(t)~t1/2, independent ofr. 相似文献
106.
粒径和流速对吸附速率的影响 总被引:4,自引:0,他引:4
本文主要考察了吸附剂的粒径大小及动态循环时流速大小对吸附速率的影响,根据膜扩散限制和孔隙扩散限制的理论模型对其影响作了定量描述。 相似文献
107.
G.?G.?GospodinovEmail author M.?G.?Stancheva 《Journal of Thermal Analysis and Calorimetry》2004,78(3):1057-1063
The solubility isotherm of the Sm2O3-SeO2-H2O system was studied at 100°C. The two compounds obtained in the three-component system were identified by the Schreinemakers method as well as by chemical, thermoanalytical and X-ray diffraction analyses after their isolation in pure state. 相似文献
108.
Xi Kui WANG* Guan Hong CHEN Zhong Yan YAO College of Chemistry Environmental Science University of Jinan Jinan 《中国化学快报》2003,14(2):205-208
Ultrasonic waves in a liquid induce the formation of cavitation bubbles. Submitted to an oscillating pressure field, cavities filled with vapor and dissolved gas pulsate, grow and implode violently when they reach a critical resonant size. According to the 慼ot spot?theory, extremely high temperature and pressure are produced during the collapse of cavitation bubbles1. Under these extreme conditions, the molecules vaporized in the bubbles as well as in the surrounding condensed layer could … 相似文献
109.
椭圆法用于阳极溶出伏安法测定微量银 总被引:6,自引:1,他引:6
用新物理量Vop的椭圆法对阳极溶出伏安法分析的含银离子浓度为10^5-10^-9mol/L的一系列溶液进行了研究。结果表明:光学方法与电化学方法所得分析结果相同;椭圆法可检测的浓度下限比电化学方法低一个数量级以上。而且测量的相对平均偏差也小于电化学方法。 相似文献
110.
本文报导了与硅原子直接相连的有机基团(R)对杂氮硅三环成环速率的影响。利用气相色谱检测成环反应的产物之一——乙醇的生成速率和数量,并同与硅相连的R基团对成环反应速率的影响作比较。实验结果表明五种杂氮硅三环成环速度顺序为Cl_2CH—>ClCH_2—>ClCH_2CH_2CH_2—>CH_2=CH—>CH_3—,这与理论推断相符。 相似文献