关于高等数学中几个易错命题的举例说明

本文通过构造具体的典型例子对高等数学中的几个易错命题进行了阐述和说明.对无限多个无穷小量的和与积的性质进行了探讨,举例说明了无限多个无穷大量的乘积不一定是无穷大量.给出了无限乘积运算时仍然是无穷大量或无穷小量的充分条件.这有助于更好地理解无穷大量和无穷小量两个概念的本质内涵,也有助于认识无限运算和有限运算的根本差异.     

再论无穷多个无穷小量的乘积

对文[6]提出的质疑给出回答,表明由于不同的无穷小量趋近于0的速度有快有慢,因此无穷多个无穷小量的乘积∏∞k=1{x_n~(k)}∞n=1,有可能不是无穷小量(其中对每个正整数k,{x_n~(k)}_(n=1)~∞表示极限为0的数列),而验证∏∞k=1{x_n~(k)}∞n=1是否是无穷多个无穷小量的乘积,只需验证对每个正整数k,当n→+∞时,{x_n~(k))_(n=1)~∞是否趋近于0,而无需考虑函数列{{x_n~(k)}_(n=1)~∞}_(k=1)~∞的极限limk→∞x_n~(k)是不是无穷小量.进而,对无穷多个无穷小量的乘积是无穷小量或不是无穷小量给出了一些充分条件,     

无穷多个无穷小量乘积的探讨

文献[1,2,3]举出反例来证明无穷多项无穷小的乘积不一定是无穷小.本文主要是对这三个反例合理性的置疑.     

关于无穷大和无穷小的几个问题

讨论了无穷大量、无穷小量和无界量之间的关系,以及无穷多个无穷小量的和与积问题     

无限个无穷小量的乘积是无穷小量吗?

<正> 在高等数学“无穷小量”的教学中,讲了有限个无穷小量的乘积为无穷小量的定理。很自然会提出这样的问题:无限个无穷小量的乘积是否为无穷小量?初看起来,似乎应该是无穷小量。但是,实际上并非如此。本文谈一个对此问题的看法。     

常数项无穷乘积的性质及判定法

无穷乘积是研究数串级数的一种方法，在无穷乘积里极限的近似值是由反复乘新的因子形成的．本文主要讨论无穷乘积的性质及收敛的判定法．     

模糊数无穷乘积

在定义了区间无穷乘积、模糊数无穷乘积及其收敛的基础上 ,利用 [3]中得到的关于模糊级数收敛的某些结论 ,得出模糊数无穷乘积与实数无穷乘积理论类似的结果 ,从而说明本文定义的模糊数无穷乘积确为实数无穷乘积的推广。     

一个有关函数单调性命题的推广

对文[1]给出的一个函数单调性的判别命题进行推广,得出两个无穷小量之比的单调性的判别命题1,2.利用结果可简便判别两个无穷小量之比的单调性及证明不等式     

谈《无穷多个无穷小量之积》

在各教程中,关于无穷小量的基本性质中都提到“有限个无穷小量之积仍然是无穷小量”,但对“有限”这个条件,均未加讨论。在教学中,不少青年教师和学生都曾提出这样的问题:“有限”这个条件可以去掉,理由是:如果α,α_1,α_2,…,α_m都是无穷小量,于是乘积α·α_1为较α的高阶的无穷小量。以此类推,α·α_1…α_n     

无穷小量在1~∞型极限中的应用

通过无穷小量讨论1∞型极限是否存在,并且介绍一种用无穷小量的等价代换快速求解1∞型极限的方法     

探寻等价无穷小关系的几种方法

介绍利用导数建立等价无穷小关系的三个方法，并举例说明．     

An Analog of the Sauer Theorem

In this paper, we present an analog of the Sauer theorem for projectively equivalent surfaces in the class of infinitely small equiareal deformations that pointwise preserve the spherical image of the surface.     

The Equivalence of Ergodicity and Weak Mixing for Infinitely Divisible Processes

The equivalence of ergodicity and weak mixing for general infinitely divisible processes is proven. Using this result and [9], simple conditions for ergodicity of infinitely divisible processes are derived. The notion of codifference for infinitely divisible processes is investigated, it plays the crucial role in the proofs but it may be also of independent interest.     

Explicit estimates for the asymptotics of subexponential infinitely divisible distribution functions

In this paper, order-sharp explicit estimates are first obtained for the asymptotics at infinity of a wide class of subexponential infinitely divisible distributions. Translated fromMatematicheskie Zametki, Vol. 67, No. 2, pp. 295–301, February, 2000.     

Equivalence of measures induced by infinitely divisible processes

We find sufficient conditions for the equivalence of two measures on function space induced by infinitely divisible processes. The processes are not assumed to be stochastically continuous or to have independent increments. The theorem proved here is equivalent to known results in the special case of stochastically continuous processes with independent increments.     

The limiting distribution for the infinitely deep dam with a Markovian input

The paper outlines a case for taking greater interest in the bottomless, or infinitely deep, dam model in Hydrology. It then shows that for such a model with unit withdrawals and an ergodic Markov chain input process the limiting distribution of depletion, when this exists, is a zero modified geometric distribution. This result generalises the well known result for independent inputs. The technical conditions required for the proof are satisfied for finite state space input processes and are shown to be satisfied by certain infinite state space input processes. These include as special cases examples which have a negative binomial limiting input distribution.     

一类二阶常微分方程初值问题的无穷多解性

应用分离变量法,得到了一类二阶微分方程初值问题存在无穷多个非负解的充分必要条件,并给出了所有的无穷多个非负解．。     

Analytic implementation of the duals of some spaces of infinitely differentiable functions

Using the Fourier-Laplace transform for functionals, we describe the duals of some spaces of the infinitely differentiable functions given on convex compact sets or convex domains in ?^N and such that the growth of their derivatives is determined by weight sequences of a general form.     

Local Theorems for the Markov Binomial Distribution

Considering the Markov binomial distribution, we study the accuracy of infinitely divisible approximations. A local version of the Kolmogorov first uniform theorem is obtained. Possible approximations in total variation are discussed.     

INFINITELY MANY SOLUTIONS FOR AN ELLIPTIC PROBLEM INVOLVING CRITICAL NONLINEARITY

We study the following elliptic problem:{-div(a(x)Du)=Q(x)|u|2-2u+λu x ∈Ω ,u=0 on ΩUnder certain assumptions on a and Q, we obtain existence of infinitely many solutions by variational method.