Interaction Between Fine Diamond Particles in Electroless Nickel Solutions

The classical DLVO theory was applied to calculate the interaction potential energy between diamond particles in electroless nickel (EN) solution and its diluted solutions with deionized (DI) water to predict their dispersion and sedimentation rates. Sedimentation tests and particle size distribution for all particle dispersions were measured to verify the DLVO calculations. Results show that the curve features of interaction potential energy vary with the dilution ratio of dispersions. The energy barrier in the curves requires the minimum 1:100 dilution of the EN solution. A sufficient energy barrier results in an extremely slow sedimentation rate of particles by keeping them separate. Otherwise, they settle down quickly due to the agglomeration resulting from their attractive forces at any separation distance. The prediction results are in good agreement with the measurement of sedimentation tests and particle size distribution. The classical DLVO theory is applicable to the field of electroless plating.     

高温高压下石墨-Ni70Mn25Co5体系中金刚石单晶合成工艺参数对金属包膜的影响

利用扫描电子显微镜和能谱仪,研究了高温高压下金刚石单晶合成工艺参数对石墨-Ni70Mn25Co5体系中金属包膜组织形貌和成分的影响。结果发现:合成压力和合成温度都合适时,金属包膜中基本无条状石墨,而且包膜中间都存在网状物,包膜中存在着明显的碳、镍和锰的成分起伏;此时合成时间对包膜的形貌影响不明显;而合成压力为5.1GPa的包膜中存在大量条状石墨,包膜中间无网状物。分析认为,网状物为溶入了锰、钴的镍基γ固溶体,该固溶体是高温高压合成过程中促使金刚石转变的催化相。     

带组约束可靠性网络最优化问题的精确算法

本文提出了一种求解带组约束串-并网络系统最优冗余问题的精确算法.该算法利用拉格朗日松驰和Dantzig-Wolfe分解法得到问题的上界,并结合动态规划求解子问题.算法采用一种有效的切割和剖分方法,以逐步缩小对偶间隙和保证收敛性.数值结果表明该算法对于求解带组约束可靠性最优化问题是很有效的.     

Shallow flow simulation on dynamically adaptive cut cell quadtree grids

A computationally efficient, high‐resolution numerical model of shallow flow hydrodynamics is described, based on dynamically adaptive quadtree grids. The numerical model solves the two‐dimensional non‐linear shallow water equations by means of an explicit second‐order MUSCL‐Hancock Godunov‐type finite volume scheme. Interface fluxes are evaluated using an HLLC approximate Riemann solver. Cartesian cut cells are used to improve the fit to curved boundaries. A ghost‐cell immersed boundary method is used to update flow information in the smallest cut cells and overcome the time step restriction that would otherwise apply. The numerical model is validated through simulations of reflection of a surge wave at a wall, a low Froude number potential flow past a circular cylinder, and the shock‐like interaction between a bore and a circular cylinder. The computational efficiency is shown to be greatly improved compared with solutions on a uniform structured grid implemented with cut cells. Copyright © 2006 John Wiley & Sons, Ltd.     

Piezoresistive effect in p-type polycrystalline diamond films

The piezoresistive effect of boron-doped polycrystalline diamond films was analyzed and discussed by the famous M-S polycrystalline model. It is found that the valence bands splitting-off and the grain-boundary scattering are the main factors responsible for the piezoresistive effect in the p-type polycrystalline diamond films. The gauge-factor calculation formula including the effect of both background scattering and grain-boundary scattering were obtained, and the calculation results are in accordance with the experimental results. Project supported by the National Naturl Sciences Foundation of China (Grant No. 69486001).     

Dynamic Elasticity of Cubic Diamond

Previously, the structure of the carbon allotrope glitter has been disclosed, and a theory accompanying the structural report as to its bulk modulus at pressure predicted it would be among the hardest materials possible. The dynamic elasticity theory developed in that paper, involving the forces generated in elastic chemical bond deformations resulting from applied mechanical forces, is here applied to the cubic diamond lattice. Stresses, both lateral and axial, contribute to the bulk modulus of cubic diamond at pressure. The ultimate strength of the cubic diamond lattice, in the approximations of the dynamic elasticity theory presented in this paper, is estimated to be in excess of 1 TPa, at modest bond length deformations of about 0.1 ?, and when including the zero pressure bulk modulus B ₀ in the computation. In particular, the dynamic elasticity model predicts the hardest direction of cubic diamond will be for an isotropic mechanical force applied along 〈111〉 directions of the structural unit cell.     

Effect of pressure on electrical resistance of WSe<Subscript>2</Subscript> single crystal

The results of electrical resistance measurements under pressure on single crystals of WSe₂ are reported. Measurements up to 8.5 GPa are carried out using Bridgman anvil set up and beyond it using diamond anvil cell (DAC) up to a pressure of 27 GPa. There is no clear indication of any phase transition till the highest pressure is reached in these measurements.     

偶数维的线性化Navier—Stokes方程解之逐点估计

道德对偶数维线性化Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程的格林函数作出估计，再用格林函数得出了其解的逐点估计。     

炸药爆轰合成超细金刚石机理的研究概况

 从实验探索、理论研究和数值模拟三方面对利用炸药分子中的碳合成超细金刚石的机理进行了系统的总结与分析，并介绍了目前这个领域的一些有待研究的问题。     

用脉冲多弧离子放电技术镀制类金刚石薄膜及其化学结构和物理特性

利用脉冲多弧离子镀膜技术，以石墨为阴极镀制的无定形碳膜，其化学结构可用Raman光谱仪进行。薄膜的硬度和电阻率物理特性，可用常规方法测量。