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1.前言微分代数方程(EEES)是经常出现于实际问题中的一类方程.其数值求解已成为常微分方程数值求解领域十分活跃的一个方向.目前微分代数方程求解的数值方法主要是nunge-Kutta型方法及BDF方法.Runge-Kutta型方法在网,问中有详细的介绍.Hairer等人据此编制了软件RADAU,而目前使用最广泛的软件还是PetZold等编制的DASSL.DASSL使用的方法为BDF方法,它在微分代数方程中的应用最早可以追述到Gear的开创性工作问.BDF方法一个很大的优点是刚性稳定.然而对于非刚性的微分代数方程,刚性稳定已不是主要考虑的因素.因此… 相似文献
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A.Mehaute和F.Utreras(1994)给出了一种平面函数型保凸插值构造光滑曲线的方法(以下简称为M-U方法).本文在利用其方法本质的基础上,给出了一种平面上参数型保凸插值构造光滑曲线的方法,同Mehaute和Utreras的方法一样,这里的方法也有局部性.另外这种方法还可以构造平面上的封闭曲线. 相似文献
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关于线性回归模型的有偏估计 总被引:3,自引:0,他引:3
有偏估计方法是近代回归分析的常用方法.本文研究了几种常用的有偏估计方法,澄清了这些方法的区别和联系.对有偏估计的一些关键点进行研究,给出了一种新的岭参数确定法和一种新的主成分概念,并讨论了这些方法的优良性.为了提高有偏估计的效率,提出了用比例因子规范模型的方法.最后,给出了说明本文方法的数值例子. 相似文献
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在鹪有关竞赛问题时.常引进三角函数.利用三角函数的变换和性质进行求鹪.是一种很有效的解题方法.对思路的显明,难点的突破,典型实用.同时也是一种技巧性很强的鹪题方法. 相似文献
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有关凸函数的一个定理的改进证明 总被引:1,自引:1,他引:0
文[1].P5.引理1.1.3的证明过程比较复杂、难以理解,本文用另外一种方法(利用函数的单调性、凹凸性和拉格朗日中值定理)对该定理进行了证明.其证明方法比文[1]的证明方法简单、明了,并对定理的结论进行了推广. 相似文献
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本文研究了多项式环上的素模中的生成基理论和方法.通过建立新的约化准则,得到了模中生成基的结构和机械化计算方法.对于低维情形给出了素模中生成基的充分必要条件.文中的方法本质地简化了传统的模中Grobner基方法.文中同时介绍了该方法在样条理论研究中的应用,并给出了一些计算例子. 相似文献
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A set-covering problem is called regular if a cover always remains a cover when any column in it is replaced by an earlier column. From the input of the problem - the coefficient matrix of the set-covering inequalities - it is possible to check in polynomial time whether the problem is regular or can be made regular by permuting the columns. If it is, then all the minimal covers are generated in polynomial time, and one of them is an optimal solution. The algorithm also yields an explicit bound for the number of minimal covers. These results can be used to check in polynomial time whether a given set-covering problem is equivalent to some knapsack problem without additional variables, or equivalently to recognize positive threshold functions in polynomial time. However, the problem of recognizing when an arbitrary Boolean function is threshold is NP-complete. It is also shown that the list of maximal non-covers is essentially the most compact input possible, even if it is known in advance that the problem is regular. 相似文献
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A new inexact-restoration method for nonlinear programming is introduced. The iteration of the main algorithm has two phases. In Phase 1, feasibility is improved explicitly; in Phase 2, optimality is improved on a tangent approximation of the constraints. Trust regions are used for reducing the step when the trial point is not good enough. The trust region is not centered in the current point, as in many nonlinear programming algorithms, but in the intermediate more feasible point. Therefore, in this semifeasible approach, the more feasible intermediate point is considered to be essentially better than the current point. This is the first method in which intermediate-point-centered trust regions are combined with the decrease of the Lagrangian in the tangent approximation to the constraints. The merit function used in this paper is also new: it consists of a convex combination of the Lagrangian and the nonsquared norm of the constraints. The Euclidean norm is used for simplicity, but other norms for measuring infeasibility are admissible. Global convergence theorems are proved, a theoretically justified algorithm for the first phase is introduced, and some numerical insight is given. 相似文献
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斯钦 《数学的实践与认识》2008,38(8):151-157
图G的k元点集X={x1,x2,…,xk}被称为G的k-可序子集,如果X的任意排列都按序排在G的某个圈上.称G是k-可序图,如果G的每一个k元子集都是G的k-可序子集.称G为k-可序Hamilton图,如果X的任意排列都位于G的Hamilton圈上.研究了3-连通3-正则图的可序子集的存在性问题. 相似文献
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Stephen J. Sugden 《Applied Mathematical Modelling》2004,28(12):1635-1082
The view factor (angle factor) for a differential inclined plane in the case of a radiating source of radially Gaussian intensity is considered. This information is useful for modelling of solar radiation in certain applications. The view factor is expressed in terms of two integrals, one of which is obtained in closed form in terms of special functions, and the other is approximated. A compact estimate for the view factor is presented which is suitable for machine computation. While the relative error associated with the final estimate is typically less than 0.01%, and in all cases, less than 0.2%, the method is easily extended to yield even greater accuracy. 相似文献
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Heteroscedasticity checks for regression models 总被引:1,自引:0,他引:1
For checking on heteroscedasticity in regression models, a unified approach is proposed to constructing test statistics in
parametric and nonparametric regression models. For nonparametric regression, the test is not affected sensitively by the
choice of smoothing parameters which are involved in estimation of the nonparametric regression function. The limiting null
distribution of the test statistic remains the same in a wide range of the smoothing parameters. When the covariate is one-dimensional,
the tests are, under some conditions, asymptotically distribution-free. In the high-dimensional cases, the validity of bootstrap
approximations is investigated. It is shown that a variant of the wild bootstrap is consistent while the classical bootstrap
is not in the general case, but is applicable if some extra assumption on conditional variance of the squared error is imposed.
A simulation study is performed to provide evidence of how the tests work and compare with tests that have appeared in the
literature. The approach may readily be extended to handle partial linear, and linear autoregressive models. 相似文献
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W. B. Gearhart 《Journal of Optimization Theory and Applications》1979,28(1):29-47
A general framework is presented in which the relation of the set of noninferior points and the set of compromise solutions is studied. It is shown that the set of compromise solutions is dense in the set of noninferior points and that each compromise solution is properly noninferior. Also, under convexity of the criteria space, a characterization of the properly noninferior points in terms of the compromise solutions is presented. In this characterization, the compromise solutions depend continuously on the weights. Use of the maximum norm is studied also. It is shown that a subset of these max-norm solutions, obtained by taking certain limits of compromise solutions, is dense and contained in the closure of the set of noninferior points. 相似文献
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王坤仁 《数学年刊A辑(中文版)》2003,(4)
一个有限群G被称为ST-群,如果对于它的子群 H、K和L有H在K中S-半正规,K在L中S-半正规,则H总在L中S-半正规,本文证明:有限群G是一个可解ST-群的充要条件是G的任一 Sylow子群的每个子群皆在 G中 S-半正规或 Abnormal。 相似文献
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INDEPENDENT-SET-DELETABLE FACTOR-CRITICAL POWER GRAPHS 总被引:3,自引:0,他引:3
原晋江 《数学物理学报(B辑英文版)》2006,26(4):577-584
It is said that a graph G is independent-set-deletable factor-critical (in short, ID-factor-critical), if, for every independent set 7 which has the same parity as |V(G)|, G-I has a perfect matching. A graph G is strongly IM-extendable, if for every spanning supergraph H of G, every induced matching of H is included in a perfect matching of H. The k-th power of G, denoted by Gk, is the graph with vertex set V(G) in which two vertices are adjacent if and only if they have distance at most k in G. ID-factor-criticality and IM-extendability of power graphs are discussed in this article. The author shows that, if G is a connected graph, then G3 and T(G) (the total graph of G) are ID-factor-critical, and G4 (when |V(G)| is even) is strongly IM-extendable; if G is 2-connected, then D2 is ID-factor-critical. 相似文献
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树状网络上的Web代理服务器最优放置问题 总被引:1,自引:0,他引:1
一般网络上Web代理服务器(Web proxy)最优放置问题是一个NP困难问题.此文讨论树状网络上的最优放置问题,改进了已有结果,得到了一个时间复杂度为O(nhk)的多项式时间算法,这里n为网络结点数,h为树的高度,而k为要放置的代理服务器个数. 相似文献