一种改进的超收敛与外推的方法

1.引 言 由于采用高精度算法能大大提高有限元计算的精度,因此有许多专家对它进行了多方面研究,取得了一批卓有成效的成果[16]研究有限元高精度的方法主要有两种: （1）美国H.A.Schatz.B.wahlbin[4,5]等发现的直接考察u-uh或　（u-uh）在局部对称点所具有的超收敛性的方法. （2）中国林群,朱起定[1,2],陈传淼[3]等所发现的通过研究uI-uh或　（uI-uh）所具有的整体超收敛与外推性质来得到u-uh或　（u-uh）在剖分点与其他某些特殊点的超收敛与外推性质.     

基于超收敛和外推方法的一类新的瀑布型多重网格方法

本文运用有限元超收敛理论和外推技巧提出了一类求解椭圆型方程的新的瀑布型多重网格方法(ACMG).数值结果表明新方法具有超收敛性.     

奇异摄动问题的一致收敛离散方法解的一致高阶精度外推

本文讨论基于整体误差一致展开式的一致收敛离散方法解的一致高阶精度外推.将该方法应用于非自共轭问题的Il'in-Allen-Southwell格式,我们得到了二阶一致收敛的外推解,并用数值计算说明该结论.     

机械求积法及其外推算法求解Helmholtz非线性边界积分方程

当Helmholtz微分方程转化为非线性边界积分方程后,可以利用机械求积法求得近似解,此方法具有较高的收敛精度阶O(h3)和较低的计算复杂度.构造机械求积法时,一个非线性方程系统通过离散非线性积分方程得到.此外,每个矩阵元素的值都不需要计算任何奇异积分.根据渐近紧理论和Stepleman定理,整个系统的稳定性和收敛性得到了证明.利用h3-Richardson外推算法,收敛精度阶可以提高到O(h5).为了求解非线性方程组,利用Ostrowski不动点定理研究了Newton的解的收敛性.几个算例从数值上说明了本算法的有效性.     

奇异摄动对流扩散方程组的参数一致的二阶有限差分格式

针对一类奇异摄动对流扩散方程组,在■网格上构造了经典的迎风有限差分格式,并利用闸函数方法证明了数值方法为一阶收敛.在此基础上,设计了一个Richardson外推格式,并严格证明了外推方法的精度为二阶一致收敛.数值实验验证了本文的理论结果.     

一种求解无约束极值问题的无记忆拟牛顿算法

§1.引言 求无约束极值常用的方法,有CG算法、变尺度算法以及拟牛顿算法等等.变尺度算法虽然收敛速度快,但是存贮量大(为O(n~2))。CG算法所需存贮量(为O(n))虽小,但在收敛速度上一般不如变尺度法.因此,本文探索收敛速度快且所需存贮量小的算法,以     

从圆周率计算到有限元外推技术

有限元方法是科学工程计算中备受欢迎的方法,而外推技术又在其它领域中证明是提高计算精度、节省计算量的强有力技术.可是,几十年来由于种种原因,有限元的外推被认为是不可思议的,直到1980年前后由国内一些人的工作开始才改变了这个传统观点.得到出人意料的结果.本文从圆周率计算开始介绍什么是外推技术,由浅入深,直至到最后介绍有限元外推理论的最新结果,力求浅显易懂.     

广义神经传播方程一个新的超收敛估计及外推

主要目的是研究双线性元对一类非线性广义神经传播方程的逼近.并利用积分恒等式及插值后处理技巧,导出H~1模及L~2模意义下的超逼近性和超收敛结果.同时,通过构造一个新的外推格式,得到了与线性问题精度完全相同的外推结果,进一步拓宽了双线性元的应用范围.     

一类非线性双曲积分微分方程的类Carey元超收敛和外推

利用非协调三角形类Carey元对一类非线性双曲积分微分方程进行了超收敛分析和外推.基于单元的特殊性质,线性三角形元的高精度分析结果,平均值和导数转移技巧,以及插值后处理技术,得到了半离散格式能量模意义下具有O(h~2)阶的超逼近性质和整体超收敛结果.同时,通过构造一个合适的辅助问题,运用Richordson外推格式,导出了具有O(h~4)阶的外推结果.     

非线性色散耗散波动方程双线性元的高精度分析

针对一类非线性色散耗散波动方程研究了双线性元逼近.基于该元的高精度分析和插值后处理技巧,对于半离散格式,在精确解的合理正则性假设下得到了H~11模意义下最优误差估计及超逼近性和超收敛结果.同时,通过构造一个新的外推格式,导出了具有三阶精度的外推解.最后,建立了一个全离散逼近格式及研究其解的超逼近性.     

On the fractional-order logistic equation

The topic of fractional calculus (derivatives and integrals of arbitrary orders) is enjoying growing interest not only among mathematicians, but also among physicists and engineers (see [E.M. El-Mesiry, A.M.A. El-Sayed, H.A.A. El-Saka, Numerical methods for multi-term fractional (arbitrary) orders differential equations, Appl. Math. Comput. 160 (3) (2005) 683–699; A.M.A. El-Sayed, Fractional differential–difference equations, J. Fract. Calc. 10 (1996) 101–106; A.M.A. El-Sayed, Nonlinear functional differential equations of arbitrary orders, Nonlinear Anal. 33 (2) (1998) 181–186; A.M.A. El-Sayed, F.M. Gaafar, Fractional order differential equations with memory and fractional-order relaxation–oscillation model, (PU.M.A) Pure Math. Appl. 12 (2001); A.M.A. El-Sayed, E.M. El-Mesiry, H.A.A. El-Saka, Numerical solution for multi-term fractional (arbitrary) orders differential equations, Comput. Appl. Math. 23 (1) (2004) 33–54; A.M.A. El-Sayed, F.M. Gaafar, H.H. Hashem, On the maximal and minimal solutions of arbitrary orders nonlinear functional integral and differential equations, Math. Sci. Res. J. 8 (11) (2004) 336–348; R. Gorenflo, F. Mainardi, Fractional calculus: Integral and differential equations of fractional order, in: A. Carpinteri, F. Mainardi (Eds.), Fractals and Fractional Calculus in Continuum Mechanics, Springer, Wien, 1997, pp. 223–276; D. Matignon, Stability results for fractional differential equations with applications to control processing, in: Computational Engineering in System Application, vol. 2, Lille, France, 1996, p. 963; I. Podlubny, A.M.A. El-Sayed, On Two Definitions of Fractional Calculus, Solvak Academy of science-institute of experimental phys, ISBN: 80-7099-252-2, 1996. UEF-03-96; I. Podlubny, Fractional Differential Equations, Academic Press, 1999] for example). In this work we are concerned with the fractional-order logistic equation. We study here the stability, existence, uniqueness and numerical solution of the fractional-order logistic equation.     

On finite groups with a reducible permutability-graph

We characterize finite groups in which the permutability-graph has more than one connected component.Research partially supported by G.N.S.A.G.A. of C.N.R. and M.U.R.S.T. of Italy.     

Computational and approximate methods of optimal control

Approximate methods of solving problems of optimal control are classified and analyzed, and their domain of applicability is indicated. Among the special problems the problem of the choice of optimal trajectories for aircraft is considered.Translated from Itogi Nauki i Tekhniki, Matematicheskii Analiz, Vol. 14, pp. 101–166, 1977.The authors of the survey are grateful to N. N. Bolotnik, M. Yu. Borodovskii, G. G. Egiyan, V. A. Korneev, V. M. Mamalyga, A. A. Mironov, Yu. R. Roshchin, and A. P. Seiranyan for their assistance in compiling the bibliography and to R. P. Soldatova and I. S. Kheiker for their help in the shaping of the paper.     

Some common fixed point theorems for weakly compatible mappings

Jungck's [G. Jungck, Compatible mappings and common fixed points, Int. J. Math. Math. Sci. 9 (1986) 771-779] notion of compatible mappings is further extended and used to prove some common fixed point theorems for weakly compatible non-self mappings in complete convex metric spaces. We improve on the method of proof used by Rhoades [B.E. Rhoades, A fixed point theorem for non-self set-valued mappings, Int. J. Math. Math. Sci. 20 (1997) 9-12] and Ahmed and Rhoades [A. Ahmed, B.E. Rhoades, Some common fixed point theorems for compatible mappings, Indian J. Pure Appl. Math. 32 (2001) 1247-1254] and obtain generalization of some known results. In particular, a theorem by Rhoades [B.E. Rhoades, A fixed point theorem for non-self set-valued mappings, Int. J. Math. Math. Sci. 20 (1997) 9-12] is generalized and improved.     

Short Book Reviews

Problems in Linear Algebra, by I. V. Proskuryakov. Mir Publishers, Moscow, 1978= 453 pp.

Inequalities: Theory of Majorization and its Applications. by A. W. Marshall and I. Olkin. Academic Press, 1979, 569 pp.

Problems in Linear Algebra, by I. V. Proskuryakov. Mir Publishers, Moscow, 1978. 453 pp. Inequalities: Theory of Majorization and its Applications. by A. W. Marshall and I. Olkin. Academic Press, 1979, 569 pp. Introduction to Numerical Analysis. by F. Stummel and K. Hainer. Scottish Academic Press (in United States, Columbia University Press), 1980. 282 pp., soft cover.

Introduction to Numerical Analysis. by F. Stummel and K. Hainer. Scottish Academic Press (in the United States, Columbia University Press), 1980. 282 pp., soft cover.     

Book reviews

L.N. TREFETHEN and D. BAU, III,Numerical Linear Algebra,SIAM, Philadelphia, 1997G.-C. ROTA,Indiscrete Thoughts,Birkhäuser, Boston, 1997D.E. KEYES, A. SAMEH and V. VENKATAKRISHNAN, eds.Parallel Numerical Algorithms,Kluwer, Dordrecht, 1997A. KIRSCH,An Introduction to the Mathematical Theory of Inverse Problems,Springer, New York, 1996L.F. SHAMPINE, R.C. ALLEN, Jr. and S. PRUESS,Fundamentals of Numerical Computing,Wiley, New York, 1997C.W. UEBERHUBERNumerical Computation, 2 vols.Springer, Berlin, 1997W.G. McCALLUM et al.Multivariate Calculus,Wiley, New York, 1997ZHI-QUAN LUO, JONG-SHI PANG and D. RALPH,Mathematical Programs with Equilibrium Constraints,Cambridge University Press, Cambridge, 1996P.R. POPIVANOV and D.K. PALAGACHEV,The Degenerate Oblique Derivative Problem for Elliptic and Parabolic Equations,Akademie Verlag, Berlin, 1997     

A modified halpern-type iteration algorithm for totally quasi-?-asymptotically nonexpansive mappings with applications

The purpose of this article is to modify the Halpern-type iteration algorithm for total quasi-?-asymptotically nonexpansive mapping to have the strong convergence under a limit condition only in the framework of Banach spaces. The results presented in the paper improve and extend the corresponding results of [X.L. Qin, Y.J. Cho, S.M. Kang, H. Y. Zhou, Convergence of a modified Halpern-type iterative algorithm for quasi-?-nonexpansive mappings, Appl. Math. Lett. 22 (2009) 1051-1055], [Z.M. Wang, Y.F. Su, D.X. Wang, Y.C. Dong, A modified Halpern-type iteration algorithm for a family of hemi-relative nonexpansive mappings and systems of equilibrium problems in Banach spaces, J. Comput. Appl. Math. 235 (2011) 2364-2371], [Y.F. Su, H.K. Xu, X. Zhang, Strong convergence theorems for two countable families of weak relatively nonexpansive mappings and applications, Nonlinear Anal. 73 (2010) 3890-3906], [C. Martinez-Yanes, H.K. Xu, Strong convergence of the CQ method for fixed point iteration processes, Nonlinear Anal. 64 (2006) 2400-2411] and others.     

某些加权复合算子之不变子空间的存在性

本文研究某些加权复合算子之非平凡不变子空间的存在性。特别地,证明了每个亚正规加权复合算子均有非平凡的不变子空间并且提出了一个新概念,称其为本性可逆变换。对于概率空间上本性可逆变换所确定的加权复合算子,给出其非平凡不变子空间存在性的一个等价刻画。     

On second-order directional derivatives of value functions

Directional derivatives of value functions play an essential role in the sensitivity and stability analysis of parametric optimization problems, in studying bi-level and min–max problems, in quasi-differentiable calculus. Their calculation is studied in numerous works by A.V. Fiacco, V.F. Demyanov and A.M. Rubinov, R.T. Rockafellar, A. Shapiro, J.F. Bonnans, A.D. Ioffe, A. Auslender and R. Cominetti, and many other authors. This article is devoted to the existence of the second order directional derivatives of value functions in parametric problems with non-single-valued solutions. The main idea of the investigation approach is based on the development of the method of the first-order approximations by V.F. Demyanov and A.M. Rubinov.     

Binary formally self-dual odd codes

Most of the research on formally self-dual (f.s.d.) codes has been developed for binary f.s.d. even codes, but only limited research has been done for binary f.s.d. odd codes. In this article we complete the classification of binary f.s.d. odd codes of lengths up to 14. We also classify optimal binary f.s.d. odd codes of length 18 and 24, so our result completes the classification of binary optimal f.s.d. odd codes of lengths up to 26. For this classification we first find a relation between binary f.s.d. odd codes and binary f.s.d. even codes, and then we use this relation and the known classification results on binary f.s.d. even codes. We also classify (possibly) optimal binary double circulant f.s.d. odd codes of lengths up to 40.