多孔催化剂非线性扩散—反应边值问题的近似解

基于大参数的假设提出了求解多孔催化剂内部非线性扩散—反应边值问题近似解的方法。在近似解的基础上，得到了计算有效因子的数学表达式。针对幂函数型动力学方程和Langmuir－Hinshelwood型动力学方程，计算了三种不同形状催化剂颗粒的有效因子。计算结果表明有效因子近似解与用数值方法求得的数位解在较宽多数范围内很吻合。本文提出的有效因子计算方法使用方便，计算快速。     

Approximation of NURBS Curves and Surfaces Using Adaptive Equidistant Parameterlzatlons

Non-uniform rational B-spline (NURBS) curves and surfaces are very important tools for modelling curves and surfaces. Several important details, such as the choice of the sample points, of the parameterization, and of the termination condition, are however not well described. These details have a great influence on the performance of the approximation algorithm, both in terms of quality as well as time and space usage. This paper described how to sample points, examining two standard parameterizations: equidistant and chordal. A new and local parameterization, namely an adaptive equidistant model, was proposed, which enhances the equidistant model, Localization can also be used to enhance the chordal parameterizatfon, For NURBS surfaces, one must choose which direction will be approximated first and must pay special attention to surfaces of degree 1 which have to be handled as a special case.     

A RBF Network Learning Scheme Using Immune Algorithm Based on Information Entropy

A hybrid learning method combining immune algorithm and least square method is proposed to design the radial basis function(RBF) networks. The immune algorithm based on information entropy is used to determine the structure and parameters of RBF nonlinear hidden layer, and weights of RBF linear output layer are computed with least square method. By introducing the diversity control and immune memory mechanism, the algorithm improves the efficiency and overcomes the immature problem in genetic algorithm. Computer simulations demonstrate that the RBF networks designed in this method have fast convergence speed with good performances.     

An approximate analytical solution to the ultrafiltration profile in a hemodialysis process between parallel porous plates

In a hemodialysis process, the blood that runs through straight channels exchanges substances with the dialysate through a semi-permeable membrane. The waste products, such as urea and creatinine, are therefore removed from the plasma by the membrane. In the analysis of this process, determination of the ultra-filtration profile along the porous membrane surface remains a difficult problem. In this work, an analytical solution to the derivation of such a profile was detailed, and the feasibility of this solution was discussed. The ultra-filtration profile was found to be in a cosine shape.     

求解磁流体过非线性伸缩薄板的变分—Adomian迭代方法(英文)

基于变分迭代方法和Adomian多项式,提出求解非齐次常微分方程初值问题的一种变分—Adomian迭代法(VAIM),并且把它应用于求解磁流体(MHD)边界层流对应初值问题的级数解.通过Padé近似值和几何轨迹对所得结果与已有解进行比较,显示该方法是非常有效的,并且能够适用于其它非线性边界层问题.     

应用Haar小波和算子矩阵求定积分的近似值

将Haar小波与算子矩阵有效结合,对被积函数进行恰当的离散,把一些不易求得原函数的定积分问题转化成计算常数矩阵的乘积。由于矩阵的乘积可以直接用MATLB来实现,从而使得计算简便,最后给出数值算例验证了方法的有效性。     

Dynamic replication strategies in data grid

Dynamic data replication is a technique used in data grid environments that helps to reduce access latency and network bandwidth utilization. Replication also increases data availability thereby enhancing system reliability. In this paper we discuss the issues with single-location strategies in large-scale data integration applications, and examine potential multiple-location schemes. Dynamic multiple-location replication is NP-complete in nature. We therefore transform the multiple-location problem into several classical mathematical problems with different parameter settings, to which efficient approximation algorithms apply experimental results indicate that unlike single-location strategies our multiple-location schemes are efficient with respect to access latency and bandwidth consumption, especially when the requesters of a data set are distributed over a large scale of locations.     

“装箱问题的一种新的近似算法”的一个注记

一维装箱问题(Bin-Packing)是一个著名的NP难的组合问题,具有极其广泛的应用背景,受到了深入细致的研究,取得了许多好的成果.2004年孙春玲等1对一维装箱问题给出一个新的近似算法,称作交叉算法,证明该算法达到一维装箱问题的最好的近似值3/2.       

浅谈近似值的取值方法

通常情况下求近似值的取值方法都是“四舍五人”法。如：125600省略万后面的尾数是13万，而124300省略万后面的尾数是12万。但值得注意的是求近似值必须按要求保留有效位数。如：2．9998保留三位小数是3．000，保留两位小数是3．00，保留一位小数是3．0，保留整数是3。又如：2．0004保留三位小数是2．000，保留两位小数是2．00，保留一位小数是2．0，保留整数是2。前面两个例子中的几个数值，表面上看是一样的，其实表示的意义不同，只是它们的近似值相等。[第一段]     

标准椭圆形封头曲率半径的近似值

根据四心圆法做椭圆的基本原理归纳出了标准椭圆封头曲率半径的近似值，从而简化了标准椭圆形封头的画法。