排序方式: 共有68条查询结果,搜索用时 15 毫秒
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Mahdi Tohidian Seyed Reza Ghaffarian Seyed Emadodin Shakeri Erfan Dashtimoghadam Mohammad Mahdi Hasani-Sadrabadi 《Journal of Solid State Electrochemistry》2013,17(8):2123-2137
Nanocomposite membranes based on polyelectrolyte complex (PEC) of chitosan/phosphotungstic acid (PWA) and different types of montmorillonite (MMT) were prepared as alternative membranes to Nafion for direct methanol fuel cell (DMFC) applications. Fourier transform infrared spectroscopy (FTIR) revealed an electrostatically fixed PWA within the PEC membranes, which avoids a decrease in proton conductivity at practical condition. Various amounts of pristine as well as organically modified MMT (OMMT) (MMT: Cloisite Na, OMMT: Cloisite 15A, and Cloisite 30B) were introduced to the PEC membranes to decrease in methanol permeability and, thus, enhance efficiency and power density of the cells. X-ray diffraction patterns of the nanocomposite membranes proved that MMT (or OMMT) layers were exfoliated in the membranes at loading weights of lower than 3 wt.%. Moreover, the proton conductivity and the methanol permeability as well as the water uptake behavior of the manufactured nanocomposite membranes were studied. According to the selectivity parameter, ratio of proton conductivity to methanol permeability, the PEC/2 wt.% MMT 30B was identified as the optimum composition. The DMFC performance tests were carried out at 70 °C and 5 M methanol feed and the optimum membrane showed higher maximum power density as well as acceptable durability compared to Nafion 117. The obtained results indicated that owing to the relatively high selectivity and power density, the optimum nanocomposite membrane could be considered as a promising polyelectrolyte membrane (PEM) for DMFC applications. 相似文献
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Stochastic optimization of an urban rail timetable under time‐dependent and uncertain demand 下载免费PDF全文
Masoud Shakibayifar Erfan Hassannayebi Hossein Jafary Arman Sajedinejad 《商业与工业应用随机模型》2017,33(6):640-661
Urban rail planning is extremely complex, mainly because it is a decision problem under different uncertainties. In practice, travel demand is generally uncertain, and therefore, the timetabling decisions must be based on accurate estimation. This research addresses the optimization of train timetable at public transit terminals of an urban rail in a stochastic setting. To cope with stochastic fluctuation of arrival rates, a two‐stage stochastic programming model is developed. The objective is to construct a daily train schedule that minimizes the expected waiting time of passengers. Due to the high computational cost of evaluating the expected value objective, the sample average approximation method is applied. The method provided statistical estimations of the optimality gap as well as lower and upper bounds and the associated confidence intervals. Numerical experiments are performed to evaluate the performance of the proposed model and the solution method. 相似文献
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Erfan Mafakheri Abdollah Salimi Rahman Hallaj Abdolali Ramazani Mohamad Almasi Kashi 《Electroanalysis》2011,23(10):2429-2437
For the first time iridium oxide (IrO2) nanotubes are synthesized by electrodeposition in a polycarbonate (PC) template. Potential cycling (90 cycles) between 0.0 and 0.9 V is used for the preparation of IrOx nanotubes onto the PC template with a pore diameter of 100 nm. Field‐emission scanning electron microscopy (FESEM) images show, that IrO2 nanotubes with uniform diameters of 110±10 nm and an estimated length of 1–3 µm are formed. The electrochemical properties and the electrocatalytic activity of a glassy carbon‐IrOx nanotube modified electrode toward Cr3+ and As3+ oxidation are investigated. Finally, the modified electrode is used for micromolar detection of the proposed analytes using differential pulse voltammetry. 相似文献
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Erfan Salavati 《Mathematical Methods in the Applied Sciences》2017,40(18):7022-7025
A well‐known result on pathwise uniqueness of the solution of stochastic differential equations in is the Yamada‐Watanabe theorem. We have extended this result by replacing the Lipschitz assumption on the drift coefficient by much weaker assumption of semi‐monotonicity. 相似文献
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Majedi FS Hasani-Sadrabadi MM Emami SH Taghipoor M Dashtimoghadam E Bertsch A Moaddel H Renaud P 《Chemical communications (Cambridge, England)》2012,48(62):7744-7746
A microfluidic platform is developed for the synthesis of monodisperse, 100 nm, chitosan based nanoparticles using nanogelation with ATP. The resulting nanoparticles tuned and enhanced transport and electrochemical properties of Nafion based nanocomposite membranes, which is highly favorable for fuel cell applications. 相似文献