A Generalized Soft-Sphere for Monte Carlo Simulation

A new collision model, called the generalized soft-sphere (GSS) model, is introduced. It has the same total cross section as the generalized hard-sphere model [Phys. Fluids A 5, 738 (1993)], whereas the deflection angle is calculated by the soft-sphere scattering model [Phys. Fluids A 3, 2459 (1991)]. In virtue of a two-term formula given to fit the numerical solutions of the collision integrals for the Lennard-Jones (6-12) potential and for the Stockmayer potential, the parameters involved in the GSS model are determined explicitly that may fully reproduce the transport coefficients under these potentials. Coefficients of viscosity, self-diffusion and diffusion for both polar and nonpolar molecules given by the GSS model and experiment are in excellent agreement over a wide range of temperature from low to high.

Effects of heat-treatment processes on the electroless Ni-B coating and its natural aging mechanism

A Ni-B coating was prepared with EN using potassium borohydride reducing agent. The as-plated micro-structure of the coating was confirmed from XRD to be a mixture of amorphous and supersaturated solid solution. Three kinds of phase transformation were observed from the DSC curve. Different from the previous works, the formation of Ni4B3 and Ni2B was found during some transformation processes. The key factors which influence the variation of micro-hardness and micro-structure in deposits are the formation, the size and amount of Ni3B, Ni4B3 and Ni2B. Aging of the deposits treated under some heat treatment conditions occurred at room temperature. Changes of the micro-hardness indicated aging phenomena evidently. the natural aging phenomena are concerned with various kinds of decomposition of borides, especially with Ni4B3 phase. The extent of natural aging depends on the formation and the quantity of Ni(4)B3 and Ni2B.

多热源分布时薄层液体中热毛细对流的分叉特征

研究一个液体薄层在热源作用下的流动特征.Pimputakar和Ostrach给出了单热源作用下薄层液体的高度和流场方程.在此基础上具体分析比较了多个热源分布作用下的流动图像随各参数尤其是随热源间距离不同的变化情况,着重讨论产生的分叉现象.

基于球形压入法提取材料的塑性力学参数

基于球形压入的工作方式,重点研究材料塑性力学参数的表征方法.首先,通过对球压入可测量的综合评价,选取能晕比(可释放功和压入总功之比)作为主要分析参数;其次,利用孔洞模型、量纲分析和数值模拟等工具,定义特定的代表性应变,建立起能量比和材料塑性力学参数之间的关系式,由此,提出一种能提取材料屈服应力和硬化指数的力学表征方法,该方法避免了对接触半径的测量,确保了方法的可操作性,并通过参数重组提高其稳定性;最后,选用45号钢和6061铝合金进行压入试验,与拉伸试验结果比对显示:该方法识别的塑性力学参数能满足工程测试需要.

Reflection and transmission of Gaussian beam from a uniaxial crystal slab

We investigate the characteristics of Gaussian beams reflected and transmitted from a uniaxial crystal slab with an arbitrary orientation of its optical axis. The formulas of the total electric and magnetic fields inside and outside the slab are derived by use of Maxwell's equations and by matching the boundary conditions at the interfaces. Numerical simulations are presented and the field values as well as the power densities are computed. Negative refractions are demonstrated when the beam is transmitted through a uniaxial crystal slab. Beam splitting of the reflected beam is observed and is explained by the resonant transmission for plane waves. Dependences of the lateral shift on the incident angle and beam width are discussed. Negative and positive lateral shifts are observed due to the spatial anisotropic properties.

Subsurface damage of Nd-doped phosphate glasses in optical fabrication

We present a destructive method for detecting and measuring subsurface damage of Nd-doped phosphate glasses. An instrument based on the dimple method - a destructive method - was developed. Subsurface damage depth produced in each fabrication procedure was obtained. We extend the surface roughness-subsurface damage relation to Nd-doped phosphate glasses. The constant ratio of subsurface damage and surface roughness was obtained as well. We also analyse the relation of abrasive size and subsurface damage experimentally. From a measurement of the surface roughness or abrasive size, one can obtain an accurate estimate of the damage layer thickness that must be eliminated by polishing or subsequent grinding operations. (C) 2007 Elsevier GmbH. All rights reserved.

掺钕陶瓷激光器获得236W高功率激光输出

随着1999年陶瓷制备工艺的突破性进展，透明陶瓷作为激光增益介质取得了可与单晶相比拟的光学质量。Nd：YAG单晶是目前应用最广泛的固体激光介质，然而传统提拉法生长的单晶的固有缺陷限制了它的进一步发展。

平面行星夹具的物理气相沉积均匀性计算

建立了平面行星夹具薄膜淀积无量纲模型。通过对蒸发源位置LIH、行星主轴与副轴距离PIH、夹角倾角A以及蒸发源蒸汽发射特性N等因素的分析，得到了典型径向理论均匀的优化几何配置．并从优化几何配置的膜料效率、角向均匀性和膜厚分布对蒸发源蒸汽发射特性变化的敏感性方面评价优化结果，得到了最优化设计区域．结果表明，优化配置的LIH＋PIH小，则角分布差异小；LIH＋PIH和A小，则膜料效率高；L〈P，A=15°时，优化配置对N变化最不敏感；L〉P时，由N变化引起的典型径向分布变化小于0．5％．