A Finite Difference Scheme for Blow-Up Solutions of Nonlinear Wave Equations

<正>We consider a finite difference scheme for a nonlinear wave equation,whose solutions may lose their smoothness in finite time,i.e.,blow up in finite time.In order to numerically reproduce blow-up solutions,we propose a rule for a time-stepping, which is a variant of what was successfully used in the case of nonlinear parabolic equations.A numerical blow-up time is defined and is proved to converge,under a certain hypothesis,to the real blow-up time as the grid size tends to zero.     

KAM Theory for Partial Differential Equations

In the last years much progress has been achieved in KAM theory concerning bifurcation of quasi-periodic solutions of Hamiltonian or reversible partial differential equations.We provide an overview of the state of the art in this field.     

傅种孙先生在北京师大附中

1 傅种孙先生简介 1.1 傅先生基本情况介绍 傅种孙先生(1898～1962)1898年2月27日生于江西省高安县.1920年在北京高等师范学校数理部毕业,留母校附中(即现北京师大附中)任教;1921年任母校数理部的讲师;1928年任教授:抗日战争以前,曾先后兼任北京女子师范大学,北平大学女子文理学院,北京大学,辅仁大学教授;1933年当选北平(北京)市数学会理事长秘书;1935年当选中国数学会评议委员兼<数学杂志>编辑;1945年11月至1946年8月在牛津大学、1946年9月至1947年11月在剑桥大学考察;1947～1962年任北京师范大学数学系教授,1956年前曾兼系主任;在1949～1957年间,曾任北京师范大学教务长(3年)及副校长(5年);1952～1957年任北京市人民代表大会代表,中国数学会及其北京市分会常务理事,<中国数学杂志>及其后身<数学通报>总编辑;1962年1月18日病逝于北京.     

Local Unstable Entropy and Local Unstable Pressure for Partially Hyperbolic Endomorphisms*

In this paper, local unstable metric entropy, local unstable topological entropy and local unstable pressure for partially hyperbolic endomorphisms are introduced and investigated. Specially, two variational principles concerning relationships among the above mentioned numbers are formulated.     

A Direct Method of Moving Planes to Fractional Power SubLaplace Equations on the Heisenberg Group

We give the direct method of moving planes for solutions to the conformally invariant fractional power sub Laplace equation on the Heisenberg group.The method is based on four maximum principles derived here.Then symmetry and nonexistence of positive cylindrical solutions are proved.     

Nonconforming Finite Element Methods for the Constrained Optimal Control Problems Governed by Nonsmooth Elliptic Equations

In this paper,nonconforming finite element methods(FEMs)are proposed for the constrained optimal control problems(OCPs)governed by the nonsmooth elliptic equations,in which the popular EQr1 ot element is employed to approximate the state and adjoint state,and the piecewise constant element is used to approximate the control.Firstly,the convergence and superconvergence properties for the nonsmooth elliptic equation are obtained by introducing an auxiliary problem.Secondly,the goal-oriented error estimates are obtained for the objective function through establishing the negative norm error estimate.Lastly,the methods are extended to some other well-known nonconforming elements.     

智慧窗

1 趣解等式七个文字与三个拼音字头组成了一道加法等式,你能否把它们分别换成0～9的数字. (相同文字、字母必须要换相同的数字)使其等式成立吗? (上海市长宁路476弄8号1602室(200042) 张刘福) 2 质数趣题请将5～20各数分别填入圆圈内,使每相邻的两个数之和都是质数.试试看,你能填出     

Hölder,Sobolev,weak-type and BMO estimates in mixed-norm with weights for parabolic equations

We prove weighted mixed-norm Lqt(W2,px)and Lqt(C2,αx)estimates for 10,x∈Rn.x∈Rn,The coefficients a(t)=(aij(t))are just bounded,measurable,symmetric and uniformly elliptic.Furthermore,we show strong,weak type and BMO-Sobolev estimates with parabolic Muckenhoupt weights.It is quite remarkable that most of our results are new even for the classical heat equation?tu?Δu+u=f.     

ON THE DIFFERENTIAL AND DIFFERENCE INDEPENDENCE OFΓANDζ

In this paper,we study the algebraic differential and the difference independence between the Riemann zeta function and the Euler gamma function.It is proved that the Riemann zeta function and the Euler gamma function cannot satisfy a class of nontrivial algebraic differential equations and algebraic difference equations.     

PRECISE VALUES OF THE BLOCH CONSTANTS OF CERTAIN LOG-p-HARMONIC MAPPINGS

The aim of this article is twofold.One aim is to establish the precise forms of Landau-Bloch type theorems for certain polyharmonic mappings in the unit disk by applying a geometric method.The other is to obtain the precise values of Bloch constants for certain log-p-harmonic mappings.These results improve upon the corresponding results given in Bai et al.(Complex Anal.Oper.Theory,13(2):321-340,2019).     

Banach空间中的广义Hη增生算子及其在变分包含中的应用

在Banach空间中,引入和研究了新的广义H-η-增生算子,对广义m-增生算子与H-η-单调算子提供了一个统一的框架．还定义了广义H-η-增生算子相应的预解算子,并且证明了其Lipschitz连续性．作为应用,考虑了涉及广义H-η-增生算子的一类变分包含问题的可解性．利用预解算子方法,构造了一个求解变分包含的迭代算法．在适当假设下,证明了变分包含解的存在性和由算法生成的迭代序列的收敛性．     

Approximation of Generalized Szasz—Mirakjan Operator

Ａｐｐｒｏｘｉｍａｔｉｏｎ　ｏｆ　Ｇｅｎｅｒａｌｉｚｅｄ　Ｓｚáｓｚ－Ｍｉｒａｋｊａｎ　ＯｐｅｒａｔｏｒＣｈｅｎｇＨａｉｌａｌ（程海来）（ＡｎｈｕｉＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇｙ）Ａｂｓｔｒａｃｔ：Ｉｎｔｈｉｓｐａｐｅｒ，ｔｈｅａｕｔｈｏ...     

ON SOLVING PERIODIC BOUNDARY PROBLEM OF SEMILINEAR SYSTEMS WITH A ONE-PARAMETER IMBEDDING

The paper is concerned with solving periodic boundary problem of semilinear systems, which will be differentiably embedded into an one-parameter family of operators. The solution of the systems is then found by continuing the solution curve of operator homotopy. When the Newton-Kantorovich's procedure is applied to the cor     

On the Behavior of the Four Order Iteration in Euler's Family Near a Zero

The aim of this paper is to study the local convergence of the four order iteration of Euler's family for solving nonlinear operator equations. We get the optimal radius of the local convergence ball of the method for operators satisfying the weak third order generalized Lipschitz condition with L-average. We also show that the local convergence of the method is determined by a period 2 orbit of the method itself applied to a real function.     

UPWIND SPLITTING SCHEME FOR CONVECTION-DIFFUSION EQUATIONS

1　ＩｎｔｒｏｄｕｃｔｉｏｎＣｏｎｖｅｃｔｉｏｎ ｄｉｆｆｕｓｉｏｎｅｑｕａｔｉｏｎｉｓａｆｕｎｄａｍｅｎｔａｌｅｑｕａｔｉｏｎｄｅｓｃｒｉｂｉｎｇｔｈｅｐｒｏｃｅｓｓｏｆｆｌｕｉｄｔｒａｎｓ ｆｅｒ,ｆｏｒｅｘａｍｐｌｅ ,ｕｎｄｅｒｇｒｏｕｎｄｗａｔｅｒｃｏｎｔａｍｉｎａｔｉｏｎ ,ｄｉｓｐｌａｃｅｍｅｎｔｉｎｐｏｒｏｕｓｍｅｄｉａ[1,2 ] ,ａｎｄｓｏｏｎ .Ｆｏｒｏｖｅｒｃｏｍｉｎｇｔｈｅｎｕｍｅｒｉｃａｌｉｎｓｔａｂｉｌｉｔｙｏｆｆｉｎｉｔｅｄｉｆｆｅｒｅｎｃｅｍｅｔｈｏｄｏｒｆｉｎｉｔｅｅｌｅｍｅ…     

The order-preserving convergence for spectral approximation of self-adjoint completely continuous operators

This paper discusses the order-preserving convergence for spectral approximation of the self-adjoint completely continuous operator T.Under the condition that the approximate operator Th converges to T in norm,it is proven that the k-th eigenvalue of Th converges to the k-th eigenvalue of T.(We sorted the positive eigenvalues in decreasing order and negative eigenvalues in increasing order.) Then we apply this result to conforming elements,nonconforming elements and mixed elements of self-adjoint elliptic differential operators eigenvalue problems,and prove that the k-th approximate eigenvalue obtained by these methods converges to the k-th exact eigenvalue.     

一类混合遗传算法的收敛性研究

针对遗传算法的有效性一般是通过数值实验来说明这一问题,本文在三个假设的条件下给出了一类混合遗传算法依概率收敛的证明,而且得到了在此算法的框架下通过改变子种群Ⅱ的变异算子而不改变依概率收敛特性的结论.     

二维Vilenkin型系统的Dirichlet核的加权平均

对二维Vilenkin型系统,我们定义加权平均极大算子T(i.e.Tf:=supn=(n1,n2)∈P2,β-1n1/n2β|Hnf|),并证明此算子是弱(1,1)型、强(p,p)型(1p∞)以及(H,L)型,其中Hnf表示部分和的加权平均,H表示Hardy空间.借用此结果得到序列Hnf是几乎处处收敛于可积函数f.     

求解非线性算子方程的加速迭代格式

研究非线性算子方程的近似求解方法.首先对通常的求解非线性方程加速迭代格式进行推广,得到高阶收敛速度的加速迭代格式,最后把这种加速迭代格式推广到非线性算子方程的求解中去,利用非线性算子的渐进展开,证明了这种加速格式具有三阶的收敛速度.     

Criterion for uniform invertibility of families of strong approximations to one-dimensional singular integral operators with continuous coefficients

A criterion is obtained for the applicability of the approximation method based on strongly approximating operator families converging to a one-dimensional singular integral operator with coefficients continuous in the circle. Some special cases are considered. Translated fromMatematischeskie Zametki, Vol. 62, No. 3, pp. 430–439, September, 1997. Translated by A. M. Chebotarev