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Multi-layer configuration for the cathode electrode of polymer electrolyte fuel cell
This paper conducts a one-dimensional theoretical study on the electrochemical phenomenon in the dual-layer cathode electrode of polymer electrolyte fuel cells (PEFCs) with varying sub-layer thicknesses, and further extends the analysis to a triple-layer configuration. We obtain the explicit solution for a general dual-layer configuration with different layer thicknesses. Distributions of the key quantities such as the local reaction current and electrolyte overpotential are exhibited at different ratios of the ionic conductivities, electrochemical kinetics, and layer thicknesses. Based on the dual-layer approach, we further derive the explicit solutions for a triple-layer electrode. Sub-layer performances are plotted and compared. The results indicate that the layer adjacent to the electrolyte membrane may contribute a major part of the electrode faradic current production. The theoretical analysis presented in this paper can be applied to assist electrode development through complicated multi-layer configuration for cost-effective high performance electrodes. © 2010 Elsevier Ltd
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Robust sliding mode design for uncertain stochastic systems based on H∞ control method
The official published version can be found at the link below.In this paper, the design problem of sliding mode control (SMC) is addressed for uncertain stochastic systems modeled by Itô differential equations. There exist the parameter uncertainties in both the state and input matrices, as well as the unmatched external disturbance. The key feature of this work is the integration of SMC method with H∞ technique such that the robust stochastic stability with a prescribed disturbance attenuation level can be achieved. A sufficient condition for the existence of the desired sliding mode controller is obtained via linear matrix inequalities. The reachability of the specified sliding surface is proven. Finally, a numerical simulation example is presented to illustrate the proposed method.This work was funded by The Royal Society of the U.K.;NNSF of China. Grant Numbers: 60674015, 60674089;The Technology Innovation Key Foundation of Shanghai Municipal Education Commission. Grant Number: 09ZZ60;Shanghai Leading Academic Discipline Project. Grant Number: B50
Spin relaxation and decoherence of two-level systems
We revisit the concepts of spin relaxation and spin decoherence of two level
(spin-1/2) systems. From two toy-models, we clarify two issues related to the
spin relaxation and decoherence: 1) For an ensemble of two-level particles each
subjected to a different environmental field, there exists an ensemble
relaxation time which is fundamentally different from . When the
off-diagonal coupling of each particle is in a single mode with the same
frequency but a random coupling strength, we show that is finite while
the spin relaxation time of a single spin and the usual ensemble
decoherence time are infinite. 2) For a two-level particle under only a
random diagonal coupling, its relaxation time shall be infinite but its
decoherence time is finite.Comment: 5 pages, 2 figure
A Fast DOA Estimation Algorithm Based on Polarization MUSIC
A fast DOA estimation algorithm developed from MUSIC, which also benefits from the processing of the signals' polarization information, is presented. Besides performance enhancement in precision and resolution, the proposed algorithm can be exerted on various forms of polarization sensitive arrays, without specific requirement on the array's pattern. Depending on the continuity property of the space spectrum, a huge amount of computation incurred in the calculation of 4-D space spectrum is averted. Performance and computation complexity analysis of the proposed algorithm is discussed and the simulation results are presented. Compared with conventional MUSIC, it is indicated that the proposed algorithm has considerable advantage in aspects of precision and resolution, with a low computation complexity proportional to a conventional 2-D MUSIC
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