传热与接触两类问题耦合作用的有限元分析

考虑传热接触耦合作用的热力学分析问题大量存在于工程中,分析的难点是必须考虑热与可移动接触边界间的耦合作用。针对这类问题的求解,该文给出了接触边界上热交换与温度边界条件,并在此基础上建立了两类变分方程,一类是热力学变分泛函,其考虑了接触区域对结构热传导的影响;另一类是二维热弹性接触分析的参数变分原理,可以方便地对接触问题进行求解。文中给出有限元分析的离散公式,并进一步给出两类问题耦合分析的迭代算法,其中接触分析的惩罚因子是可以消除的,数值结果验证了该文的理论与算法。     

多孔饱和半空间上弹性圆板垂直振动的积分方程

应用新的方法求解多孔饱和固体的动力基本方程－Ｂｉｏｔ波动方程,首先把Ｂｉｏｔ波动方程化为仅有土骨架位移和孔隙水压力的偏微分方程组,并且逐次解耦方法（不引入位移势函数）求解此偏微分方程组,然后按混合边值条件建立多孔饱和半空间上弹性圆板垂直振动的对偶积分方程,用Ａｂｅｌ变换化对偶积分方程为第二类Ｆｒｅｄｈｏｌｍ积分方程。文中考虑两种孔隙流体的表面边界条件：（ａ）半空间表面（包括圆板与半空间的接触面）是     

Theory of Supercoiled Elastic Rings with Self-Contact and Its Application to DNA Plasmids

Methods are presented for obtaining exact analytical representations of supercoiled equilibrium configurations of impenetrable elastic rods of circular cross-section that have been pretwisted and closed to form rings, and a discussion is given of applications in the theory of the elastic rod model for DNA. When, as here, self-contact is taken into account, and the rod is assumed to be inextensible, intrinsically straight, transversely isotropic, and homogeneous, the important parameters in the theory are the excess link Δℒ (a measure of the amount the rod was twisted before its ends were joined), the ratio ω of the coefficients of torsional and flexural rigidity, and the ratio d of cross-sectional diameter to the length of the axial curve C. Solutions of the equations of equilibrium are given for cases in which self-contact occurs at isolated points and along intervals. Bifurcation diagrams are presented as graphs of Δℒ versus the writhe of C and are employed for analysis of the stability of equilibrium configurations. It is shown that, in addition to primary, secondary, and tertiary branches that arise by successive bifurcations from the trivial branch made up of configurations for which the axial curve is a circle, there are families of equilibrium configurations that are isolas in the sense that they are not connected to bifurcation branches by paths of equilibrium configurations compatible with the assumed impenetrability of the rod. Each of the isolas found to date is connected to a bifurcation branch by a path which, although made up of solutions of the governing equations, contains regions on which the condition of impenetrability does not hold. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contact Problem for Porous Elastic Half-Plane

The paper is concerned with a static contact problem about a rigid punch on the free surface of a linear porous elastic half-plane. With the use of the Fourier transform the problem is reduced to a singular integral equation holding over the contact zone. This integral representation permits consideration of the Flamant problem (a line load on the half-plane) to be explicitly reduced to some quadratures. It is shown that in the classical linear elasticity limit the main integral equation has a Cauchy-type kernel, so distribution of the contact pressure is like in the Sadowsky punch-problem. For arbitrary porosity a numerical co-location technique is applied that allows one to analyze in detail the distribution of the contact pressure versus porosity. Both in the Flamant and Sadowsky problems we demonstrate a higher compliance of the porous foundation, with respect to the classical linear elastic results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fast evaluation of friction forces in traction-drive contacts including thermal effects

Summary  In automotive traction drives, power is transmitted by friction forces. The friction forces result from the shear stresses developed in lubricated and highly loaded contacts between rolling bodies. Due to the kinematics of a traction drive, shear velocities occur in both the rolling direction and perpendicular to it. Due to these shear velocities and by normal pressure, the lubricant is forced to build up shear stresses. The increase of the shear stresses may be modelled by a nonlinear viscous element. The describing differential equations are coupled by the equivalent shear stress, which defines the nonlinear behaviour of the element. A fast method is described to evaluate the coupled differential equations. By using a known analytical approximation for the equivalent shear stress, the differential equations are decoupled and can be solved analytically. In an iterative procedure the equivalent shear stress is updated, and the complete solution is found. The iterative method is extended to account for thermal effects in the contact. Received 17 June 1999; accepted for publication 26 October 1999     

近乎Sasakian流形的CR子流形

本文定义并讨论了近乎Ｓａｓａｋｉａｎ流形的ＣＲ子流形,得到了关开这类子流形的微分几何方面的一些有意义的结果。     

A Linear Complementarity Approach for the Non-convex Seismic Frictional Interaction between Adjacent Structures under Instabilizing Effects*

The paper deals with a numerical treatment of the dynamic hemivariational inequality problem concerning the elastoplastic-fracturing unilateral contact with friction between neighboring structures under second-order geometric effects during earthquakes. The numerical procedure is based on an incremental problem formulation and on a double discretization, in space by the finite element method and in time by the Houbolt method. The generally nonconvex constitutive contact laws are piece-wise linearized, and in each time-step a nonconvex linear complementarity problem is solved with a reduced number of unknowns.     

自组装半导体碳纳米管薄膜的光电特性

采用自组装的方法制备99%高纯度半导体碳纳米管平行阵列条带,以金属钯和钪为非对称接触电极制备碳纳米管（CNT）薄膜晶体管（TFTs）器件. 主要研究不同沟道长度碳纳米管薄膜晶体管器件的电输运特性和红外光电响应特性,分析了其中的载流子输运和光生载流子分离的物理机制. 我们发现薄膜晶体管器件的电学性能和光电性能依赖于器件沟道长度（L）和碳纳米管的平均长度（L_CNT）. 当沟道长度小于碳纳米管的平均长度时,器件开关比最低;当沟道长度超过碳纳米管平均长度时,随着沟道长度的增加,器件开关比增加,光电流减小.相关研究结果为高纯碳纳米管薄膜晶体管器件在红外光探测器方面的进一步应用提供参考依据.     

测定痕量磷的激光热透镜光谱法--钼蓝法与孔雀绿法的比较

采用激光热透镜光谱法（LTLS）,分别以孔雀绿－磷钼杂多酸缔合物法和磷钼蓝法对痕量磷进行了测定;探讨了测定条件的影响,分析比较了两种测定方法,结果表明,钼蓝法的线性范围较宽,孔雀绿法的灵敏度较高,选择性较好,将孔雀绿LTLS法应用于河水、自来水和土壤样品中痕量磷的分析测定,取得了满意的效果。     

在玻璃的TiO2涂膜上有机物分子的吸附及光催化分解对水接触角的影响

研究了有机物分子在玻璃的TiO₂ 和WO₃/TiO₂ 复合物涂膜上的吸附及光催化分解对水接触角的影响.结果表明:有机物在空白玻璃及其膜的表面的吸附为不可逆化学吸附,WO₃/TiO₂ 复合物膜可钝化玻璃表面对大气污染物分子的吸附能力并具有较好的光催化活性.