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The main aim of this study is to simulate the response of a micro-PEMFC numerically by utilizing a 3-D FEM model while the micro-PEMFC was assembled by three pairs of bolt along the upper and lower portions, respectively, of the end plates. The effects of different bolts locking sequences on the deformation and pressure distributions at flow-channel plates in a micro-PEMFC were investigated. The simulated results showed that if one locked the middle bolt either on the upper or lower portion first, then the obtained warpage, uniformities of deformation and von Mises equivalent stress were superior than those results if one locked either one of the four corner bolts first. Also, among the three pairs of bolts used for assembling the cell, the first locking bolt of the first pair of locking bolt and the first locking bolt of the rest of two pairs of locking bolt were to minimize the warpage and stress should locate on the different portions of the end plates.

SUMMARY This paper presents a new DC/DC converter with series half-bridge legs for high voltage application. Two half-bridge legs connected in series and two split capacitors are used in the proposed circuit to limit the voltage stress of each active switch at one-half of input voltage. Thus, active switches with low voltage stress can be used at high DC bus application. In the proposed converter, two circuit modules are operated with an interleaved pulse-width modulation scheme to reduce the input and output ripple currents and to achieve load current sharing. In each circuit module, two resonant tanks are operated with phase-shift one-half of switching cycle such that the frequency of the input current is twice the frequency of the resonant inductor current. Based on the resonant behavior, all MOSFETs are turned on at zero voltage switching with the wide ranges of input voltage and load conditions. The rectifier diodes can be turned off at zero current switching if the switching frequency is less than the series resonant frequency. Thus, the switching losses on power semiconductors are reduced. The proposed converter can be applied for high input voltage applications such as three-phase 380-V utility system. Finally, experiments based on a laboratory prototype with 960-W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2011 John Wiley & Sons, Ltd.

A methodology has been developed for the analysis of operational flexibility of a continuous processing plant. An application has been demonstrated for a multipurpose plant with uncertain operating conditions. A practical flexibility analysis procedure using a direct search optimization algorithm is proposed to solve the problem. The method provides a heuristic screening technique that makes it possible to avoid the exhaustive enumeration of every constraint vertex, while the direct search optimization offers a simple and effective means to identify bottlenecks. A refinery multiperiod plant problem has been investigated in order to highlight the procedures which lead to the construction of flexibility indices for each operating mode. On a mis au point une methodologie pour l'analyse de la flexibilite operationnelle d'une unite de traitement continue. Une application est demontree pour une unite a usages multiples dans des conditions operatoires incertaines. Une procedure pratique d'analyse de la flexibilite utilisant un algorithme de recherche direct est proposee pour resoudre le probleme. La methode fournit une technique de selection heuristique qui permet d'eiter l'enumeration exhaustive de chaque sommet de contraintes, tandis que l'optimisation par recherche directe offre un moyen simple et efficace d'identifier les goulots d'etranglement. On a etudie une probleme pour une unite de raffinage a periodes multiples dans le but de mettre en evidence les procedures qui menent a l'etablissement des indices de flexibilite pour chaque mode operatoire.

A dynamic simulation model for the bioleaching of uranium ore in a stope leaching process has been developed. The model incorporates design and operating conditions, reaction kinetics enhanced by Thiobacillus ferrooxidans present in the leaching solution and transport properties. Model predictions agree well with experimental data with an average deviation of about ± 3%. The model is sensitive to small errors in the estimates of fragment size and ore grade. Because accurate estimates are difficult to obtain a parameter estimation approach was developed to update the value of fragment size and ore grade using on-line plant information.

An equation of state is obtained to describe the fluid state from the supercritical gas to subcritical vapor and liquid for small and large molecules of organic and inorganic substances. The perturbation theory of the fluid state is extended to include rotational contribution of molecular motion in addition to translational and the attractive force contributions. Three equation constants describe a substance and values are presented for 22 substances. Application is made to mixtures with emphasis on their phase equilibria.