W^12[a,b]空间中线性变系数常微分方程组的精确解

该文利用再生核空间的技巧，在Ｗ＾１２「ａ，ｂ」空间中给出了微分方程组：｛ｕ′ｉ（ｘ）＋∑ｎｊ＝１ａｉｊ（ｘ）ｕｊ（ｘ）＝ｆｉ（ｘ）ｕｉ（ａ）＝ｕ＾（０）ｉｉ＝１，２，…，ｎ。的精确解，利用精确解给出了便于用计算机计算的近似解。     

对称本原有向图的广义本原指数集

本文证明了全体ｎ阶对称本原有向图的第ｋ个第一类（１≤ｋ＜ｎ－１）、第二类（１≤ｋ≤ｎ－１）和第三类（２≤ｋ≤ｎ－１）广义本原指数的指数集分别是｛１，２，…，ｎ－２＋ｋ｝和｛１，２，…，２（ｎ－ｋ）｝，其中「ａ］表不小于ａ的最小整数，［ｂ］表不大于ｂ的最大整数。     

再生核空间偏微分方程解析数值解

１．引言 偏微分方程的近似解法一直是数值计算的重要内容之一。随着计算机的发展,各种实用的新方法也不断涌现．本文在再生核空间Ｈ　（Ｄ）中给出二阶偏微分方程边值问题解析形式的级数解,该级数解具有如下特点：１．级数截断就可直接得到解析数值解;２．解析数值解的误差在空间范数意义下单调下降． 设 Ｄ＝［ａ, ｂ］ ｘ ［ｃ, ｄ］是 Ｒ２中的任一矩形域, Г为边界,０,ｕ（ｘ,ｙ）∈Ｌ２（Ｄ）且是实的绝对连续函数,中规定内积如下： 范数定义为： 山中已证明码（利是一个再生核函数空间,其再生校函数研Ｘ,认（,…表达式…     

关于一类和式的估值

设｛ａｎ｝为递增的正项等差数列：ａｎ＝ａ１＋（ｎ－１）ｄ，ｎ∈Ｎ，其中ｄ，ａ１＞０，本文讨论和式ｎｋ＝１１ａｋ＝１ａ１＋１ａ２＋…＋１ａｎ的估值，并解决文［１］中遗留的问题．定理１设ｄ≤２ａ１，则对任意ｎ∈Ｎ有ｍｎ≤ｎｋ＝１１ａｋ＜Ｍｎ①其中Ｍｎ...     

非线性发展方程解的渐近性的构造过程

本文借助Ｂａｎａｃｈ空间中的新不等式，通过迭代过程ｘｎ＋１＝ｘｎ－ａｎＡｘｎ（ｘ０∈Ｄ（Ａ），ｎ＝０，１，２，…）研究非线性发展方程ｄｕ／ｄｔ＝－Ａｕ解的渐近性，构造性地证明了，在一定条件下｛ｘｎ｝的极限点就是该发展方程的平衡点，推广了文献［１］的结论。     

1999年全国高中数学联合竞赛试题及参考答案

一、选择题１．给定公比为ｑ（ｑ≠１）的等比数列｛ａｎ｝,设ｂ１＝ａ１＋ａ２＋ａ３,ｂ２＝ａ４＋ａ５＋ａ６,…,ｂｎ＝ａ３ｎ－２＋ａ３ｎ－１＋ａ３ｎ,…,则数列｛ｂｎ｝（　　）．　（Ａ）是等差数列　　（Ｂ）是公比为ｑ的等比数列　（Ｃ）是公比为ｑ３的等比数列　（Ｄ）既非等差数列又非等比数列解　由题设,ａｎ＝ａ１ｑｎ－１,则　ｂｎ＋１ｂｎ＝ａ３ｎ＋１＋ａ３ｎ＋２＋ａ３ｎ＋３ａ３ｎ－２＋ａ３ｎ－１＋ａ３ｎ＝ａ１ｑ３ｎ＋ａ１ｑ３ｎ＋１＋ａ１ｑ３ｎ＋２ａ１ｑ３ｎ－３＋ａ１ｑ３ｎ－２＋ａ１ｑ３ｎ－１＝ａ１ｑ３…     

高维空间中半线性波动方程的Sobolev指数

ＧｕｓｔａｖｏＰｏｎｃｅ与ＴｈｏｍａｓＣ．Ｓｉｄｅｒｉｓ［４］猜测对一些具有特殊非线性项的半线性波动方程，如ｕｔ－△ｕ＝ｕｋ（Ｄｕ）α（ｘ∈Ｒｎ，ｋ∈Ｚ＋，ｌ＝｜α｜２），其中Ｓｏｂｏｌｅｖ指数会在ｎ２与（ｎ２＋１）之间．文［４］中，在ｘ∈Ｒ３时，回答了这一问题．本文在ｎ３维空间中，得到了半线性波动方程ｕｔ－△ｕ＝ｕｋ（Ｄｕ）α（ｘ∈Ｒｎ，ｋ∈Ｚ＋，ｌ＝｜α｜２）的Ｓｏｂｏｌｅｖ指数为ｍａｘ｛ｎ２＋１２，（ｎ２－１）·ｌ－３ｌ－１＋２｝，此数确实在区间［ｎ２＋１２，ｎ２＋１］中．     

贪婪t－相交有限序列族

设Ｆ为有限序列族，对ａ＝（ａ１，ａ２，…，ａｎ）∈Ｆ，ａｉ为整数且０≤ａｉ≤ｓｉ（整数），记ｓ（ａ）＝｛ｊ｜１≤ｊ≤ｎ，ａｊ＞０｝，ｓ（Ｆ）＝｛ｓ（ａ）｜ａ∈Ｆ｝，及Ａ｛１，２，…，ｎ｝时Ｗ（Ａ）＝Пｉ∈Ａｓｉ．称Ｆ为贪婪ｔ－相交，如对任何ａ，ｂ∈Ｆ，至少有ｔ个ａｉ，ｂｉ＞０，且Ｗ（Ａ）≥Ｗ（（｛１，２，…，ｎ｝－Ａ）＋Ｂ）对任何Ａ∈Ｓ（Ｆ）及ＢＡ（｜Ｂ｜＝ｔ－１）成立．本文得到当ｓ１＞ｓ２＞…＞ｓｎ时的最大贪婪ｔ－相交有限序列族．     

关于二阶线性递归数列的周期性

关于二阶线性递归数列的周期性肖振纲（湖南岳阳师专４１４０００）对于给定初始值Ｘ１，Ｘ２，并由二阶线性递归关系（其中ａ，ｂ均为常数）：所确定的数列｛Ｘｎ｝的周期性问题，文［１］，［２］，［３］分别就ａ，ｂ均为实数的情形进行了探讨，得到了一些富有启发性的...     

对概率论中一个大数律证明题的讨论

在我国出版或翻译出版的一些概率论习题集中有这样一道题：设｛ξｎ｝为具有相同的数学期望、方差（有界）的随机变量序列,且当ｉ≠ｊ时Ｅ（ξｉξｊ）≤０,证明｛ξｎ｝服从（弱）大数律．参见［１］、［２］．按照有些书提示的证明方法,可设对任意ｎ有Ｅξｎ＝μ,Ｄ...     

Exact MAX-2SAT solution via lift-and-project closure

We present a new approach for exact solution of MAX-2SAT problems based on a strong reformulation deduced from an optimal continuous solution over the elementary closure of lift-and-project cuts. Computational results show that this formulation leads to a reduced number of nodes in the branch-and-bound tree and short computing times.     

Minimum node covers and 2-bicritical graphs

The problem of finding a minimum cardinality set of nodes in a graph which meet every edge is of considerable theoretical as well as practical interest. Because of the difficulty of this problem, a linear relaxation of an integer programming model is sometimes used as a heuristic. In fact Nemhauser and Trotter showed that any variables which receive integer values in an optimal solution to the relaxation can retain the same values in an optimal solution to the integer program. We define 2-bicritical graphs and give several characterizations of them. One characterization is that they are precisely the graphs for which an optimal solution to the linear relaxation will have no integer valued variables. Then we show that almost all graphs are 2-bicritical and hence the linear relaxation almost never helps for large random graphs.This research was supported in part by the National Research Council of Canada.     

Optimal node disjoint paths on partial 2-trees: A linear algorithm and polyhedral results

We present anO(p · n) algorithm for the problem of finding disjoint simple paths of minimum total length betweenp given pairs of terminals on oriented partial 2-trees withn nodes and positive or negative arc lengths. The algorithm is inO(n) if all terminals are distinct nodes. We characterize the convex hull of the feasible solution set for the casep=2.We gratefully acknowledge the referee's many helpful suggestions to improve the presentation of this paper.     

W_2~1空间中的最佳数值原函数

求数值原函数问题,是对离散形式给出的实函数u(x)(即仅给出u(x)在有限多个点上的函数值),求其近似原函数F_n(x),而且当节点无限加密时,F_n(x)收敛于u(x)的原函数F(x).例如微分方程的数值解法,实质上就归结为求数值原函数问题.通常     

ANALYSIS OF THE LIMIT CYCLE OF A GENERALISED VAN DER POL EQUATION BY A TIME TRANSFORMATION METHOD

Abstract

The properties of the limit cycle of a generalised van der Pol equation of the form ü + u = ε (1—u²ⁿ)u, where ε is small and n is any positive integer, are investigated by applying a time transformation perturbation method due to Burton. It is found that as n increases the amplitude of the limit cycle oscillation decreases and its period increases. The time transformation solution is compared with the solution derived using the method of multiple scales and with a numerical solution. It is found that, to first order in ε, the time transformation solution for the limit cycle agrees better with the numerical solution than the multiple scales solution. Both perturbation solutions give the same result for the period of the limit cycle to second order in ε. The accuracy of the time transformation solution decreases as n increases.     

On Birkhoff interpolation (0;2) case

P. Turán and his associates^[2] considered in detail the problem of (0,2) interpolation based on the zeros of π_n(x). Motivated by these results and an earlier result of Szabados and Varma^[9] here we consider the problem of existence, uniqueness and explicit representation of the interpolatory polynomial R_n(x) satis fying the function values at one set of nodes and the second derivative on the other set of nodes. It is important to note that this problem has a unique solution provided these two sets of nodes are chosen properly. We also promise to have an interesting convergence theorem in the second paper of this series, which will provide a solution to the related open problem of P. Turán.     

不定方程x~2+y~2=z~2的若干推广与统一解法

本文对不定方程x2+y2=z2给出了四个推广,并用一种统一的解法对这四个推广给出了解答.     

L2 ASYMPTOTIC FOR THE EQUILIBRIUM SOLUTION OF THE F-M EQUATIONS IN THE SPACE-PERIODIC CASE

The L² exponetial asymptotical stability for the equilibrium solution of the F-M equations in the space-periodic case (n = 2) is considered. Under some assumptions on the external force, it can be shown that the weak solution of F-M equations with initial and boundary conditions in space-periodic case approaches the stationary solution of the system exponetially when time t goes to infinite.     

Grid approximation of singularly perturbed parabolic reaction-diffusion equations on large domains with respect to the space and time variables

In an unbounded (with respect to x and t) domain (and in domains that can be arbitrarily large), an initial-boundary value problem for singularly perturbed parabolic reaction-diffusion equations with the perturbation parameter ε² multiplying the higher order derivative is considered. The parameter ε takes arbitrary values in the half-open interval (0, 1]. To solve this problem, difference schemes on grids with an infinite number of nodes (formal difference schemes) are constructed that converge ε-uniformly in the entire unbounded domain. To construct these schemes, the classical grid approximations of the problem on the grids that are refined in the boundary layer are used. Schemes on grids with a finite number of nodes (constructive difference schemes) are also constructed for the problem under examination. These schemes converge for fixed values of ε in the prescribed bounded subdomains that can expand as the number of grid points increases. As ε → 0, the accuracy of the solution provided by such schemes generally deteriorates and the size of the subdomains decreases. Using the condensing grid method, constructive difference schemes that converge ε-uniformly are constructed. In these schemes, the approximation accuracy and the size of the prescribed subdomains (where the schemes are convergent) are independent of ε and the subdomains may expand as the number of nodes in the underlying grids increases.     

OSCILLATION CONVERGENT THEOREMS FOR THE V^2-INTEGRAL

The V^t-integral as defined in[2], which is eqnivalent to M^2-integrsl as defined in Trigonometre series by Zygmund is used to sum trigonometric seies in[1]. In this paper, some convergent theorems of V^2-integral are established.