一类A(α)稳定的k阶线性k步法公式

本文给出了一类与Gear方法类似的k阶线性k步法隐式公式.作者还求出了公式的分数形式的系数,阶数和局部截断误差主项系数,并验证了2-6步公式都具有A(α)稳定的,计算出了它们的幅角α.最后用对比数值实验验证了公式确实是稳定的,并且适合于求解刚性常微分方程.     

一类A(α)稳定的κ阶线性κ步法公式

本文给出了一类与Gear方法类似的κ阶线性κ步法隐式公式.作者还求出了公式的分数形式的系数,阶数和局部截断误差主项系数,并验证了2-6步公式都具有A(α)稳定的,计算出了它们的幅角α.最后用对比数值实验验证了公式确实是稳定的,并且适合于求解刚性常微分方程.     

一类显式的k阶线性k步法基本公式

本文给出了一类比Adams-Bashforth方法的局部截断误差主项系数小和绝对稳定区间大的显式k阶线性k步法基本公式.作者求出了公式的分数形式的精确系数,阶数和局部截断误差主项系数,给出了3-9步公式的绝对稳定区间,构造了由新公式的4阶显式公式和一个同阶隐式基本公式组合而成的特殊预估-校正方法,它的绝对稳定区间大于预估公式而且等于校正公式, 比著名的Adams-Bashforth-Moulton预估校正方法的绝对稳定区间大, 最后用数值试验对结果进行了验证,适合于求解常微分方程初值问题.     

一类隐式的k+1阶线性k步法

本文首先给出了一类比Adams-Moulton方法的绝对稳定区间大的隐式k+1阶线性k步法基本公式.求出了3-9步新公式的分数形式的精确系数,阶数,局部截断误差主项系数和绝对稳定区间,然后构造了由4阶隐式新公式和同阶显式Nyström公式组合而成的预估-校正方法,比著名的Adams-Bashforth-Moulton和Nyström-Adams-Moulton预估校正方法的绝对稳定区间大,最后用对比数值试验对结果进行了验证.     

具有A(α)-稳定的Adams-Moulton公式类型

给出了含参数的3阶3步法的A(α)-稳定的Adams-Moulton类型公式族.同时求出了公式的精确分数形式的系数,阶数和局部截断误差主项系数,计算出了它们的幅角α,最后用对比数值实验验证了公式是稳定的,并且适合于求解刚性常微分方程.     

基于k字位置序列的蛋白质序列分析方法及其应用

基于蛋白质序列的κ-字位置序列,利用标准化的κ-字区间平均距离和改进的标准化的κ-字区间平均距离的方法作为蛋白质序列的数字特征,并给出了比较蛋白质序列相似性的方法.最后,运用这两种方法分析了9个物种的ND5蛋白质序列和8个物种的ND6蛋白质序列的相似性,并利用交叉验证得出基于改进的标准化的κ-字区间平均距离的方法的准确度比基于标准化的κ-字区间平均距离的方法的准确度高.     

一类含时滞的抛物方程

的解当t→+∞时关于x∈Ω一致趋于零的问题,以下简称为解的一致渐近稳定性问题。本文给出了一致渐近稳定的充分必要条件。这里α、τ、κ、σ为非负常数,κ~2+σ~2≠0.α,b为常数.△为拉普拉斯算子。x∈R~n,     

牛顿科茨公式计算超奇异积分的误差估计

超奇异积分的数值计算是边界元方法中的重要的课题之一,本文得到了牛顿科茨公式计算任意阶超奇异积分误差估计,当误筹函数中的Sκ(p)(Τ)=0时,便得到超收敛现象,并给出了Sκ(p)(Τ)之间的相互关系.相应的数值算例验证了理论分析的正确性.     

高阶常型微分算子自伴域的辛几何刻划

考虑高阶常型实系数微分算子ι(y)=n↑∑↑k=0(pn-ky^(κ))^(κ)(x∈[α,b])。利用辛几何，对ι（y）的自伴域进行了分类，给出了ι（y）自伴域是κ－级的充要条件（0≤κ≤n）。     

半群P_n(k)的正则性和Green关系

设P_n是X_n={1,…,n}上的部分变换半群.对任意1≤k≤n,令P_n(k)={α∈P_n:(x∈dom(α)x≤k■xα≤k},则易验证P_n(k)是P_n的子半群.刻画了半群P_n(k)的正则元的特征,并且描述了这个半群上的Green关系.     

一类含有稳定参数的Adams型隐式方法及其新算法

§1.引言 数值积分Stiff常微分方程初值问题,其积分过程的稳定性相当重要.用传统的数值方法,如Adams方法等,为保证计算稳定性,积分步长受到相当的限制.在stiff常微分方程初值问题的数值解法中,Gear方法是目前最通用的方法之一.但是,当阶p大     

一类多值多导数方法的收敛性与稳定性

1 引言 对于多值多导数方法,由于其多值多导的结构特点有利于提高解的精度,以及其包容性大,它包含了当今常用的多种常微数值方法,诸如:线性多步法,单支方法,多步多导方法,多(单)步Runge—Kutta方法,多导Runge-Kutta方法以及混合方法等.因此收敛性与稳定性的研究具有重要的实践意义和广泛的理论指导意义,也正因如此,这方面的研究工作引起了众多数值工作者们的兴趣,近年来,多值多导法求解刚性问题的B—收敛及其非线性稳定性的研究工作巳获得较大进展,其相应成果可参见文献[1—3],在文献[4,5]中笔者则针对Banach空间中一类非刚性问题-K~((p))类问题,分别探讨了多步多导法及单支方法的收敛性     

A Class of Multistep Method Containing Second Order Derivatives for Solving Stiff Ordinary Differential Equations

In this paper a general k-step k-order multistep method containing derivatives of second order is given. In particular, a class of k-step (k+1)th-order stiff stable multistep methods for k=3-9 is constructed. Under the same accuracy, these methods are possessed of a larger absolute stability region than those of Gear's [1] and Enright's [2]. Hence they are suitable for solving stiff initial value problems in ordinary differential equations.     

High-order splitting methods for separable non-autonomous parabolic equations

We consider the numerical integration of non-autonomous separable parabolic equations using high order splitting methods with complex coefficients (methods with real coefficients of order greater than two necessarily have negative coefficients). We propose to consider a class of methods that allows us to evaluate all time-dependent operators at real values of the time, leading to schemes which are stable and simple to implement. If the system can be considered as the perturbation of an exactly solvable problem and the flow of the dominant part is advanced using real coefficients, it is possible to build highly efficient methods for these problems. We show the performance of this class of methods on several numerical examples and present some new improved schemes.     

Passive Runge–Kutta Methods—Properties, Parametric Representation, and Order Conditions

In this paper, a new class of Runge–Kutta methods is introduced. Some basic properties of this subgroup of algebraically stable methods are presented and a complete parametric representation is given. Necessary and sufficient order conditions for lower order methods as well as sufficient order conditions for higher order methods are derived yielding a significantly reduced number of conditions when compared with general Runge–Kutta methods. Design examples conclude this paper.     

一类中立型延迟积分微分方程Runge-Kutta方法的稳定性

讨论了一类非线性中立型延迟积分微分方程Runge-Kutta方法的稳定性.在适当的条件下证明了运用Runge-Kutta方法求解这类方程既是数值稳定的也是渐近稳定的.     

Multilevel Schwarz methods for elliptic problems with discontinuous coefficients in three dimensions

Summary. Multilevel Schwarz methods are developed for a conforming finite element approximation of second order elliptic problems. We focus on problems in three dimensions with possibly large jumps in the coefficients across the interface separating the subregions. We establish a condition number estimate for the iterative operator, which is independent of the coefficients, and grows at most as the square of the number of levels. We also characterize a class of distributions of the coefficients, called quasi-monotone, for which the weighted -projection is stable and for which we can use the standard piecewise linear functions as a coarse space. In this case, we obtain optimal methods, i.e. bounds which are independent of the number of levels and subregions. We also design and analyze multilevel methods with new coarse spaces given by simple explicit formulas. We consider nonuniform meshes and conclude by an analysis of multilevel iterative substructuring methods. Received April 6, 1994 / Revised version received December 7, 1994     

Second derivative general linear methods with inherent Runge–Kutta stability

In this paper, we find some relationships among the coefficients matrices of second derivative general linear methods (SGLMs) which are sufficient conditions, but not necessary, to ensure the methods have Runge–Kutta stability (RKS) property. Considering these conditions, we construct some A– and L–stable SGLMs with inherent RKS of orders up to five. Also, some numerical experiments for the constructed methods in variable stepsize environment are given.