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Acoustic waves in a phononic crystal (PnC) showed properties of band gaps and anisotropic propagation and promised many applications. By arranging the filling fraction of PnCs gradually in space, a gradient-index (GRIN) PnC was proposed to bend the wave propagation. GRIN PnCs were reported and applied as an acoustic lens to focus acoustic waves. Theoretically, this kind of lens has a hyperbolic secant...
Enterprises do not typically choose between R&D cooperation and R&D competition. They may be engaged in a large number of R&D projects. Some cooperatively with others, some competitively on their own. So there is need to take both cooperation and competition into account simultaneously. We set up a model of nontournament process R&D where enterprises engage simultaneously in noncooperative...
Evaluation for target threat is an important part in the defensive decision making. As to each target, there are multiple attributes described by fuzzy or uncertain information which is represented with interval numbers. How to integrate these fuzzy information becomes a meaningful work. This paper integrates the fuzzy numbers by introducing the distance among interval numbers to find a special interval...
This letter presents a novel synthetic aperture radar (SAR) image segmentation method based on a single graph cut. Due to the speckle, the classical pixel-by-pixel Markov random field (MRF) based SAR image segmentation method may still result in salt and pepper label map. Compared to the classical MRF based SAR image segmentation method, our proposed method exploits geometric prior to describe the...
Flow field is the important part in proton exchange membrane (PEM) fuel cell and one of its control factors. In this paper, the performance of PEM fuel cell with non-equipotent flow field was tested. Influences of the dimension change and the arrangement of flow field on its performance is analyzed. Experimental results show that comparison with conditional water management in PEM fuel cell with equipotent...
PEM fuel cell is a kind of generator with the characteristics of high efficiency and no pollution. Dynamic performance of current density distribution is important one of its parameters. In this paper, current density distribution measurement gasket and fuel cell test system were used to measure current density distribution in PEM fuel cells. Effects of fuel cell temperature and humidification temperature...
PEM fuel cell is a clean and high-efficient generation, which can be applied widely. Oxygen concentration of cathode reactants plays an important role on its performance. Performance of PEM fuel cell was surveyed by experiments in this paper. Influence of oxygen concentration on performance of PEM fuel cell is studied. Experimental results show that with the increase of oxygen concentration, open...
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