Much work has been conducted on the substitutes for Nafion as proton exchange membrane materials. Some researches are focused on the heterogeneous multilayered membranes reported by R. Jiang [J. Electrochem. Soc. 153 (2006) (2005) 59]. However, just as the dependence of methanol crossover upon the layer with the lowest permeability, the proton transfer ability is major confined by the layer with the poorest conductivity. Moreover, various swelling ratio and contractibility of sub-layers will make the hidden problems of separation between catalyst layer and proton exchange membrane become more obvious. We present here a multilayered membranes containing five thin layers of sulfonated poly(ether ether ketone)(SPEEK) and five thin layers of poly(vinyl alcohol)(PVA). SPEEK layers and PVA layers were located alternatively in the composite membrane. The swelling behaviors of PVA layer are restrained by both sideward SPEEK layers. Methanol crossover is efficiently alleviated piece by piece without visible proton conductivity loss. The preliminary investigation in DMFC suggests its promising application as resisting methanol and proton exchange membrane.
In this paper, for heat conductivity identification of three dimension steady heat transfer model of composite materials, a new hybrid Tikhonov regularization mixed multiscale finite-element method is present. First the mathematical models of the forward and the coefficient inverse problems are discussed. Then the forward model is solved by mixed multiscale FEM which utilizes the effects of fine-scale heterogeneities through basis functions formulation computed from local heat transfer problems. At last the numerical approximation of inverse coefficient problem is obtained by Tikhonov regularization method.
This paper discusses three kinds of typical one-dimensional nonlinear equations coming from low permeability reservoir seepage models with different boundary conditions. The several finite difference methods including forward difference method and second central order difference quotient method are used for the respective discrete process of three models. With these difference methods, the discrete schemes of models are obtained. Then the corresponding nonlinear discrete equations are deduced. While dealing with the boundary condition, the mid-rectangle formula is used. Finally, integrated discrete equations of three nonlinear equations are formed. The results should be meaningful for the numerical simulation of non-Darcy flow model of the low-permeability oil wells.
<p class="p15">The main innovation of this paper includes two parts. One part is the discrete formulas of Thermo-hydro-mechanical (THM) coupling equations and another part is the discussion of the truncation errors based on the Taylor formula. There are many THM coupling problems in unsaturated soils, which are very important in both theoretical and engineering applications. The numerical computing of coupling equations is increasingly important. Considering the deformation of unsaturated soils skeleton, fluid flow and heat transfer, constitutive relationships of the THM coupled behavior are given. Then, the constitutive equations are derived and a closed problem is formed. The equations are dispersed by difference method and the truncation errors of the discrete formulas are given.</p>
This article Considers an inverse problem for identifying a pollution source in a watershed. The pollution concentration is governed by a linear advection-dispersion-reaction equation with a point pollution source modeled by the Dirac function. Firstly, a system of first-order ordinary differential equations is obtained by using the semi-discretization approach and the approximation of the Dirac function. Then the location of the point source is identified from the measurements. Secondly, the numerical scheme is established for recovering the strength of pollution based on the above semi-discretization scheme and the location of the point source. Thirdly, the error analysis was investigated from two aspects: both the semi-discretization and the approximation of the Dirac function. At last, the numerical results show that the presented method is effective.
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