NiCrBSi激光熔敷层组织及腐蚀磨损行为

应用５ｋｗ—ＣＯ２激光器在４５钢基材上进行镍基合金激光熔敷处理．观察并测定了激光熔敷层的组织及显微硬度分布，着重探讨了该合金激光熔敷层在不同条件下的腐蚀磨损行为．试验结果表明，在酸性介质中，激光溶敷层的腐蚀磨损速率随介质浓度及冲击速度的提高而线性增加，其中冲击速度影响较为显著．激光熔敷层的腐蚀磨损失效是以磨料磨损为主，失效机制是显微切削并伴随着凿削磨损。     

中国与东欧经济改革比较研究

原中央计划经济国家近年的经济改革导致不同的结果：东欧国家的经济衰退和中国的经济高速增长．本文利用描述性统计方法表示正在进行经济改革的某些国家的各种经济性能指标，并调查与考察了中央计划经济国家改革的理论、时机、速度、规模及先后次序．     

Parallel (M−N)SVD algorithms on the SIMD computers

LetA bem byn matrix,M andN be positive definite matrices of orderm andn respectively. This paper presents an efficient method for computing (M?N) singular value decomposition ((M?N) SVD) ofA on a cube connected single instruction stream-multiple data stream (SIMD) parallel computer. This method is based on a one-sided orthogonalization algorithm due to Hestenes. On the cube connected SIMD parallel computer witho(n) processors, the (M?N)SVD of a matrixA requires a computation time ofo(m ³logm/n).     

松散岩堆细-宏观强度关系与围岩压力

中国西南某铁路隧道围岩体为大孔隙率松散巨型岩堆体,是典型的非连续性颗粒材料,已不能用基于连续介质的经典土力学去解决其本构问题.为了从细-宏观角度研究松散岩堆的强度特性和围岩稳定性,从颗粒材料力学对致密砂土的力学分析出发,通过分析得出了松散岩堆的平面咬合模型的变形模式是点-面接触作用,推导出由岩堆内部岩块单元的摩擦角主导的宏观强度关系式;提出了松散岩堆岩体单元之间的咬合作用模型,得到松散岩堆咬合力关系,岩块单元间的细观摩擦角对宏观强度有较大影响;从适合破碎围岩的普氏理论出发,结合岩堆细观强度公式,得出了松散岩堆自然平衡拱轴线的计算方法,通过计算某铁路隧道围岩压力,验证了计算公式的合理性.     

Different time slices for different degrees of freedom in Feynman path integration

A general scheme is presented for using different numbers of ‘time slices’ for different degrees of freedom in a path integral evaluation of the Boltzmann operator for a large molecular system. This will be particularly useful, for example, in evaluating the ‘quantum instanton’ rate constant [cf. W.H. Miller, Y. Zhao, M. Ceotto, S. Yang. J. Chem. Phys., 119, 1329 (2003)] for H atom transfer reactions, or any applications involving atoms with largely differing masses.     

Metal and annealing atmospheres dependence of resistive switching in metal/Nb0.7wt%-SrTiO3 interfaces

We investigated the resistance switching (RS) effect of metal/Nb-doped SrTiO₃ interfaces under different treating conditions. Two types of I–V characteristics appeared due to the modification of Schottky-like barrier and the formation of insulating layer. According to X-ray photoelectron spectroscopy analysis, the change in interface potential barrier was contributed to the migration of oxygen vacancies and electrons trapping/detrapping of carriers in the vicinity of interface. Nonlinear fitting is applied to the curves to study the conduction mechanism of metal/NSTO. For “barrier height” style, Schottky emission and Poole–Frenkel (P–F) emission are dominating; for “insulating layer” style, space-charge-limited current, controls the conduction.     

α粒子散射实验的计算机模拟

利用计算机的计算和作图功能对α粒子散射实验进行了模拟．由于采用了面向对象的编程语言C Builder，使得软件的使用非常简单，只要用户任意设定实验的参数，计算机就会模拟出α粒子在各种情况下的散射现象．便于学生对α粒子散射实验进行深入的研究。     

The extension of fixed point theorems for set valued mapping

In this paper, the Menger Probabilistic n-metric space is presented, some fiex point theorem for set valued mapping are extended to Menger probabilistic n-metric space.     

Nonlinear uzawa methods for solving nonsymmetric saddle point problems

In [A new nonlinear Uzawa algorithm for generalized saddle point problems, Appl. Math. Comput., 175(2006), 1432–1454], a nonlinear Uzawa algorithm for solving symmetric saddle point problems iteratively, which was defined by two nonlinear approximate inverses, was considered. In this paper, we extend it to the nonsymmetric case. For the nonsymmetric case, its convergence result is deduced. Moreover, we compare the convergence rates of three nonlinear Uzawa methods and show that our method is more efficient than other nonlinear Uzawa methods in some cases. The results of numerical experiments are presented when we apply them to Navier-Stokes equations discretized by mixed finite elements.     

圆锥曲线焦点弦性质的推广

本文利用圆锥曲线的统一方程,将文[1]中圆锥曲线特殊的焦点弦性质推广到了一般的焦点弦的情形。