关于广义积分定义的一个注记

广义积分作为定积分的推广 ,在高等数学中有着较为广泛的应用 .但许多高等数学方面的教材(甚至有些数学分析教材 )对于广义积分定义的处理还有失严谨 .如文献 [1 ],[2 ],[3 ]在给出函数f( x)在无穷区间 [a,+∞ )上的广义积分的定义时 ,都是采用如下的叙述方式 :定义 1　设函数 f( x)在区间 [a,+∞ )上连续 ,取 b>a,如果极限 limb→ +∞∫baf ( x) dx存在 ,则称此极限为函数 f ( x)在无穷区间 [a,+∞ )上的广义积分 ,记作∫+∞a f ( x) dx ,即∫+∞a f ( x) dx =limb→ +∞∫baf ( x) dx.这时也称广义积分∫+∞a f ( x) dx收敛 ;如果上述极限…     

紧摄动连续映象

Let X, Z be normed spaces and Ω a bounded open set in X. Suppose that I:Ω→Z is a fixed continuous bounded mapping. We discuss the properties essential and nonessential of f(x) = I(x) - F(x), see [1] p.245, where F:?Ω→Z continuous and compact.     

关于几乎处处可微函数的一个问题

设f(x)是定义在[a,b]上的绝对连续函数,M[a,b]是可测集.众所周知,如果 mf(M)=0 (m表示Lebesgue测度),则f′(x)在M中几乎处处等于0(例如参见文献[17]).Varberg推广了上述结果,在[2]中他证明了f(x)绝对连续的条件可用f(x)连续且具有有界变差的条件来代替.在[2]之末,Varberg发问:f(x)连续性的条件是否可以除去?如果答案是肯定的,那末f(x)具有有界变差的条件是否可用f′(x)几乎处处存在的条件来代替?     

集值映象的不动点与系统的周期解

本文研究局部凸空间中集值映象的不动点定理,并用于如下的系统(Ⅰ)的周期解研究 x′(t)=f(1,x(t)) (1) §1 引言 设X为(Hausdorff)局部凸空间(简记为LCS); 关于T的不动点,有以下两个重要结果:[1]中的定理4.5.1;[3]中的Glicksberg不动点定理,它们都要求△=Ω为凸集。但前者还要求T单值连续且T(△)在△的某紧子集中;后者还要求T为K映象(即T为闭的,且对任一x∈△,T(x)为不空紧凸集)且△为紧的。     

Browder-Petryshyn型严格伪压缩映象复合迭代算法的收敛性

<正>1引言设E是实Banach空间,E*为E的对偶空间,〈·,·〉表示E与E*之间的广义对偶对.正规对偶映象J:E→2~(E*)定义为J(x)={f∈E*:〈x,f〉=‖x‖~2=‖f‖~2},x∈E.用j表示J中的单值映象.用F(T)表示映象T的不动点集.定义1.1设E是实Banach空间,K是E的非空凸子集,T:K→K是一个映象,则称T是Lipschitz的,若存在L0,使得,x,y∈K,有‖Tx-Ty‖≤L‖x-y‖.称     

平均值函数的性质及应用

设函数 f (x)在 (-∞ , ∞ )上连续 ,当 x≠ 0时 ,我们称 F(x) =1x∫x0 f (t) dt为 f (x)在 [0 ,x]上的平均值函数 ,本文将介绍平均值函数 F(x)的若干性质并举例说明其应用 .一、F(x)的性质性质 1　 f(x)是 [0 ,x](或 [x,0 ])上的有界函数 ,F(x)也是 [0 ,x]或 [x,0 ]上的有界函数 .性质 2　若 f (x)为奇 (偶 )函数 ,则 F(x)也为奇 (偶 )函数 .性质 3　若 f(x)是周期为 T(T>0 )的周期函数 ,则limx→ ∞1x∫x0f (t) dt=1T∫T0f (t) dt (1 )　　　性质 4　若 f(x)为单调递增 (减 )函数 ,则 F(x)也为单调递增 (减 )函数 .性质 5　若对任意…     

导算子连续和一致连续的充要条件

专著[1]论及导算子连续和一致连续的充要条件,给出过于下的定理。 设T_r={x|‖x-x_o‖0)有界.(见[1]36面定理3.8) 本文改进了以上结果。     

反常积分敛散性的根值判别法

由于积分与级数在理论上是统一的,因此有关正项级数的根式判别法可被推广以判别无穷限积分和瑕积分的敛散性.设f(x)是[a,+∞)上的非负函数,li mx→+∞xf(x)=ρ,则当ρ1时,反常积分∫a+∞f(x)dx收敛,而当ρ1时,反常积分∫a+∞f(x)dx发散;设f(x)是(a,b]上的非负函数,a为瑕点,xli→ma+(f(x))x-a=ρ,则当ρ1时,反常积分∫abf(x)dx收敛,而当ρ1时,反常积分∫baf(x)dx发散.     

关于非凸函数的共轭函数问题

[2]中给出了如下引理([2]中编号为9.2.7): 设S是E_n中非空紧集,f:S→E_i是下闭的,则f_c_0(x)=f″(x),x∈H(S). 但[2]中的证明是不正确的.因为在证明过程中实际上用到了f的凸性,而引理中的f无凸性假定.本文用其他方法证明这一结论,同时还得到了有关非凸函数共轭函数的其他性质. 为讨论方便起见,对某些记号和结论略作说明:     

关于Szász-Mirakjan型算子的加权逼近

设S_n(f;x)表示如下的Sz(?)sz-Mirakjan算子:S_n(f;x)=sum from k=0 to ∞ f(k/n)S_(nk)(x),这里S_(nk)(x)=e~(-nx)(nx)~k/k!,x∈[0,∞),f∈C_[0,∞),C_[0,∞),表示在[0,∞)上连续且有界之函数集,1983年在[1]中给出了Sn(f;x)在一致逼近意义下的特征刻划,为讨论L_p逼近,[2]中引进了如下的Sz(?)sz-Mirakjan-Kantorovich算子:     

Affine Generalized Quadrangles – An Axiomatization

The complement of a geometric hyperplane of a generalized quadrangle is called an affine generalized quadrangle. Since a geometric hyperplane of a generalized quadrangle is either an ovoid or the perp of a point or a subquadrangle, there are three quite different classes of affine generalized quadrangles. The article proposes seven axioms (AQ1)–(AQ7) characterizing affine generalized quadrangles as point-line geometries. Certain subsets of the seven Axioms together with certain conditions distinguish what kind of hyperplane complement is realized. By just (AQ1)–(AQ6), finite affine generalized quadrangles are characterized completely.     

Derivatives of generalized farthest functions and existence of generalized farthest points

The relationship between directional derivatives of generalized farthest functions and the existence of generalized farthest points in Banach spaces is investigated. It is proved that the generalized farthest function generated by a bounded closed set having a one-sided directional derivative equal to 1 or −1 implies the existence of generalized farthest points. New characterization theorems of (compact) locally uniformly convex sets are given.     

高阶Lagrange中值定理“中值点”的渐近性

借助Stirling数研究了高阶Lagrange微分中值定理在f(n+1)(a)=0或f(n+1)(a)不存在时的“中值点”的渐近性,并给出了渐近性估计式.     

A class of generalized shift-splitting preconditioners for nonsymmetric saddle point problems

In this paper, a class of generalized shift-splitting preconditioners with two shift parameters are implemented for nonsymmetric saddle point problems with nonsymmetric positive definite (1, 1) block. The generalized shift-splitting (GSS) preconditioner is induced by a generalized shift-splitting of the nonsymmetric saddle point matrix, resulting in an unconditional convergent fixed-point iteration. By removing the shift parameter in the (1, 1) block of the GSS preconditioner, a deteriorated shift-splitting (DSS) preconditioner is presented. Some useful properties of the DSS preconditioned saddle point matrix are studied. Finally, numerical experiments of a model Navier–Stokes problem are presented to show the effectiveness of the proposed preconditioners.     

Exact solutions of the one-dimensional generalized modified complex Ginzburg–Landau equation

The one-dimensional (1D) generalized modified complex Ginzburg–Landau (MCGL) equation for the traveling wave systems is analytically studied. Exact solutions of this equation are obtained using a method which combines the Painlevé test for integrability in the formalism of Weiss–Tabor–Carnevale and Hirota technique of bilinearization. We show that pulses, fronts, periodic unbounded waves, sources, sinks and solution as collision between two fronts are the important coherent structures that organize much of the dynamical properties of these traveling wave systems. The degeneracies of the 1D generalized MCGL equation are examined as well as several of their solutions. These degeneracies include two important equations: the 1D generalized modified Schrödinger equation and the 1D generalized real modified Ginzburg–Landau equation. We obtain that the one parameter family of traveling localized source solutions called “Nozaki–Bekki holes” become a subfamily of the dark soliton solutions in the 1D generalized modified Schrödinger limit.     

环上矩阵广义Moore-Penrose逆的存在性

讨论带有对合反自同构*有单位元的结合环R上矩阵的广义Moore-Penrose 逆,给出了环R上矩阵的广义Moore-Penrose逆存在的几个充要条件．特别,得到了环 R上矩阵A的关于M和N的广义Moore-Penrose逆存在的充要条件是A有分解A= GDH,其中D2=D,(MD)*=MD,(GD)*MGD+M(I-D)和DHN-1(DH)*+ (I-D)M-1均可逆．     

广义模糊子半环的广义模糊双(内)理想

给出了广义模糊子半环的广义模糊双(内)理想的概念.运用截集、模糊子集的和与积得到了广义模糊子半环的广义模糊双(内)理想的等价条件及性质,同时还得到了在半环的同态映射下同态像及同态原像的性质.当λ=0,μ=1时,得到一般意义下的模糊子半环的模糊双(内)理想的相应结果.     

区域函数的广义导数及其应用

本文以[7]的基本概念为基础,并根据Clarke的广义导数[1],以及Lasotra和Strauss[6]的多值函数f(x)的广义微分D_f(x)的定义.从而建立了区域函数F(x)的广义导数D_F=∪∩{G(x)?B(R),?x∈B(R);G(x)=F_x=F(x)}讨论了区域函数F(x)的广义导数的存在性;建立了区域函数的广义Fréchet导数存在的必要充分条件.     

Nest代数上的在零点广义可导映射

设A为B（H）的子代数,　是A到B（H）的线性映射,我们说　在0点广义可导（广义双边可导）,如果对任意的S,T∈A且ST=0（ST=0或TS=0）,有　（ST）=　（S）T+S　（T）-S　（I）T.本文主要得到如下结果:（1）有限Nest代数上的每个范数拓扑连续的在0点广义可导的线性映射是广义内导子;（2）若N是完备Nest且H_　 H,则algN上的每个范数拓扑连续的在0点广义双边可导的线性映射是广义内导子.     

广义谱分解与亏损矩阵幂的算法

提出了亏损矩阵广义谱分解概念,所得广义特征矩阵具有类似若当链的性质AA(h)i=λiA(h)i+A(h+1)i.亏损矩阵可分解成A=∑si=1(λiA(0)i+A(1)i),由Am=∑si=1∑mh=0Chmλm-hiA(h)i可生成线性方程组,求出各A(h)i,进而计算A的较大次幂Am.介绍了广义谱分解在计算矩阵幂级数中的应用.