焦绿石型复合氧化物对氧电极反应的催化作用

前文介绍了新型双功能氧电极材料Pb_2[Ru_(2-x-g)Sb_xPb_y]O_(7-z)焦绿石型复合氧化物(简称Pb-Sb-Ru氧化物)的合成及其性能。本文介绍氧在该氧化物上还原及析出的动力学特性。 1 实验方法 1.1 材料的制备 Pb-Sb-Ru氧化物的制备、检测方法同文献中的材料4~#。     

Optical properties of methane to 288 GPa at 300 K

Optical properties of solid methane (CH₄) were studied at high pressure and room temperature using a diamond anvil cell. Reflectivity and transmission measurements were used to measure the refractive index to 288 GPa. Fabry-Perot interferometery was used to measure the sample thickness to 172 GPa. This data was fitted to the derived expression of thickness vs. pressure that was then used to calculate the thickness to 288 GPa. This in turn was combined with optical absorption experiments to obtain the absorption coefficient and hence the extinction coefficient k^*. From combined reflection and absorption experiments the refractive index n=n_s+ik^* was obtained. The index of refraction and the ratio of molar refraction to molar volume showed a large increase between 208 and 288 GPa. This behavior indicated that a phase transformation of insulator-semiconductor might have occurred in solid CH₄ by 288 GPa.     

Implicit application of non‐reflective boundary conditions for Navier–Stokes equations in generalized coordinates

The non‐reflective boundary conditions (NRBC) for Navier–Stokes equations originally suggested by Poinsot and Lele (J. Comput. Phys. 1992; 101 :104–129) in Cartesian coordinates are extended to generalized coordinates. The characteristic form Navier–Stokes equations in conservative variables are given. In this characteristic‐based method, the NRBC is implicitly coupled with the Navier–Stokes flow solver and are solved simultaneously with the flow solver. The calculations are conducted for a subsonic vortex propagating flow and the steady and unsteady transonic inlet‐diffuser flows. The results indicate that the present method is accurate and robust, and the NRBC are essential for unsteady flow calculations. Copyright © 2005 John Wiley & Sons, Ltd.     

A sorted partial jacobi method and its convergence analysis

Jacobi methods for computing the eigendecomposition of a class of so-called low-rank-plus-shift symmetric matrices are investigated. An order-of-magnitude reduction in the computational complexity can be achieved for this special class of matrices by terminating the Jacobi sweep early in a cyclic ordering. It is proved that these partial sweeps combined with sorting the diagonals still deliver quadratic convergence. It is also shown that useful results can still be obtained even if the low-rank-plus-shift structure only holds approximately.     

An efficient upwind/relaxation algorithm for the Euler and Navier–Stokes equations

An efficient Euler and full Navier–Stokes solver based on a flux splitting scheme is presented. The original Van Leer flux vector splitting form is extended to arbitrary body-fitted co-ordinates in the physical domain so that it can be used with a finite volume scheme. The block matrix is inverted by Gauss–Seidel iteration. It is verified that the often used reflection boundary condition will produce incorrect flux crossing the wall and cause too large numerical dissipation if flux vector splitting is used. To remove such errors, an appropriate treatment of wall boundary conditions is suggested. Inviscid and viscous steady transonic internal flows are analysed, including the case of shock-induced boundary layer separation.     

模糊仿真的近似推理与边值问题的数值解

本运用模糊仿真技术中的近似推理方法和差分原理，求解具有模糊不确定性时的二阶微分方程的边值问题．     

Modifying the generalized singular value decomposition with application with application in direction-of-arrival finding

We consider updating and downdating problems for the generalized singular value decomposition (GSVD) of matrix pairs when new rows are added to one of the matrices or old rows are deleted. Two classes of algorithms are developed, one based on the CS decomposition formulation of the GSVD and the other based on the generalized eigenvalue decomposition formulation. In both cases we show that the updating and downdating problems can be reduced to a rank-one SVD updating problem. We also provide perturbation analysis for the cases when the added or deleted rows are subject to errors. Numerical experiments on direction-of-arrival (DOA) finding with colored noises are carried out to demonstrate the tracking ability of the algorithms. The work of the first author was supported in part by NSF grants CCR-9308399 and CCR-9619452. The work of the second author was supported in part by China State Major Key Project for Basic Researches.     

试论高比能量电池进展

在综述电化学近５０年来比能量提高情况的基础上，讨论了现代科技发展对电池比能量的要求，以及当今电池能在多大程度上满足这些要求，并讨论了进一步提高电池比能量的可能性及可能途径．     

碳酸盐岩储层流体包裹体差分拉曼光谱的研究

拉曼微探针分析法对单个气液包裹体的化学成分和相态的无破坏性测量来说,目前几乎是唯一最好的方法.但是由于众多因素的影响,特别是主矿物具有较强荧光时,提高信噪比的问题急待解决.本工作对碳酸盐岩储层包裹体样品制成的薄片进行了显微观察、荧光测试及拉曼分析,并进行了空间上横向XY扫描、纵向上深度剖析(Z扫描)和冷热台上变温的流体包裹体筹分拉曼光谱测量方法的研究.结果表明,所得到的差谱揭示了包裹体更真实的光谱曲线,消除了主矿物对包裹体的干扰,以较高的信噪比显现出包裹体中流体(-170℃温度下的冰)位于位移波数3 098 cm-1附近的宽拉曼散射峰,明显的改善了信噪比.     

Molecular dynamics study of mechanical properties of carbon nanotube-embedded gold composites

The mechanical properties of nano-single crystal gold and carbon nanotube-embedded gold (CNT/Au) composites under axial tension were investigated using molecular dynamics (MD) simulation method. The interactions between atoms were modeled using the many-body tight-binding (TB) potential and the empirical Tersoff potential coupled with the Lennard-Jones (L-J) potential. We get the yield strain and the yield stress of nano-single crystal gold 0.092, 5.74 GPa, respectively. The computational results show that the increase in Young's modulus of the long CNT-embedded gold composite over pure gold is much large. From the simulation, we also find that the yield stress and the yield strain of short CNT-embedded gold composite are evidently less than that of the nano-single crystal gold.