常微分方程(组)的高次积分因子与高次积分及其微分特征列集算法

考虑了一般微分方程(组)高次积分和其微分特征列集(吴方法)机械化确定算法.首先提出微分方程的积分因子和首次积分的推广高次积分因子与其对应的高次积分的概念.其次给出了由高次积分因子确定其对应的高次积分的计算公式,使确定高次积分的问题转化为求高次积分因子的问题.再其次对确定高次积分因子的问题,给出了微分特征列集算法.最后用给定的算法确定了二阶和三阶微分方程拥有高次积分的结构定理,并给出了具体的算例和结论.     

S-积分与Gronwall不等式

S-积分是利用Thomson的局部系定义的一种广义Riemann积分.本文证明了针对S-积分的Gronwall-Bellman不等式.作为特例,我们也获得了针对Henstock积分和Burkill近似连续积分的Gronwall-Bellman不等式.     

无穷区间反常积分中值定理的推广

积分中值定理是微积分中的重要内容之一.传统的积分中值定理是建立在定积分的概念上,而对反常积分很少涉及.文中从对无穷区间上连续函数的性质分析出发,建立和证明了无穷区间反常积分的中值定理.它是对反常积分理论和教学方面的有力补充.     

一类特殊的Riemann-Liouville分数阶积分的几何意义

主要研究阶数等于0.5的Riemann-Liouville (RL)分数阶积分的几何意义.通过变量替换,证明了0.5阶RL积分等价于沿着圆弧的曲线积分.对于同一个积分,如果沿着曲线观察,此积分是曲线积分;如果沿着坐标轴观察,此积分是分数阶积分.此结论说明,分数阶微积分提供了一种观察客观世界的新角度.另外,应用分数阶理论求解了一个关于转动惯量的问题,此实例说明分数阶现象是广泛存在的.     

利用重积分求解一元积分

对于一些难以求解的一元积分，可以将被积函数或者被积函数中的一部分转化为另外一个定积分或者广义积分，这样就将一元定积分变成了多元函数的重积分，再通过交换积分顺序就可以得到原积分的结果.以几个典型的积分为例，利用这种方法，最终求得积分结果.     

弹性力学问题解唯一的边界积分方程

从积分方程式出发,应用基本解的特性分析,说明在力边值问题中,位移边界积分方程和面力边界积分方程的位移解不唯一.提出了位移解唯一的条件,建立了唯一解的位移边界积分方程和面力边界积分方程.实例计算结果表明唯一解的边界积分方程是有效的.     

对称性在积分学中的应用

如果能充分利用积分区域的对称性和被积函数的奇偶性,高等数学中许多积分的计算过程将得到简化.总结并借助实例说明对称性在高等数学定积分、重积分以及曲线与曲面积分计算中的应用.     

平坦外平行体的平均曲率积分的均值(英文)

本文研究了Rn中平坦的外平行体的平均曲率积分.利用积分几何的方法和凸体理论的相关知识,得到了这些平均曲率积分的均值.作为推论,我们得到了这些平均曲率积分所对应的均质积分的均值.     

凸体的弦幂积分公式

本文研究了高维欧氏空间中凸体的弦幂积分问题.利用积分的方法,获得了凸体弦幂积分的几个积分公式.     

一类对偶积分方程组正则化为第一类含对数核的Fredholm奇异积分方程组解法

引入辅助未知函数及辅助未知函数的积分关系式,表示原未知函数,将对偶积分方程组退耦.应用Sonine第一有限积分公式,实现化为Abel型积分方程组,应用Abel反演变换并化简,正则化为含对数核的第一类Fredholm奇异积分方程组.由此给出奇异积分方程组的一般性解,进而获得对偶积分方程组的解析解,同时严格地证明了,对偶积分方程组和由它化成的含对数核的奇异积分方程组的等价性,以及对偶积分方程组解的存在性和唯一性.     

On the existence and uniqueness of a generalized solution of the mixed problem for the wave equation with the second and third boundary conditions

We prove the uniqueness of a generalized solution of an initial-boundary value problem for the wave equation with boundary conditions of the third and second kind. In addition, we find a closed-form expression for the analytic solution of that problem with zero initial data. The result plays an important role in the investigation of the boundary control problem. We show how to use the obtained solution for the investigation of the boundary control problem in the case of subcritical time intervals for which the solution of the boundary control problem, if it exists at all, is unique. We obtain necessary and sufficient conditions for the existence of a unique solution in a class admitting the existence of finite energy.     

On the numerical solution of a nonlocal boundary value problem for a degenerating pseudoparabolic equation

We study a nonlocal boundary value problem for a degenerating pseudoparabolic third-order equation of the general form. For the solution of the problem, we obtain a priori estimates in differential and difference form, which imply the stability of the solution with respect to the initial data and right-hand side on a layer as well as the convergence of the solution of the difference problem to the solution of the differential problem.     

An Iterative Method for Finding the Least Solution to the Tensor Complementarity Problem

In this paper, we are concerned with finding the least solution to the tensor complementarity problem. When the involved tensor is strongly monotone, we present a way to estimate the nonzero elements of the solution in a successive manner. The procedure for identifying the nonzero elements of the solution gives rise to an iterative method of solving the tensor complementarity problem. In each iteration, we obtain an iterate by solving a lower-dimensional tensor equation. After finitely many iterations, the method terminates with a solution to the problem. Moreover, the sequence generated by the method is monotonically convergent to the least solution to the problem. We then extend this idea for general case and propose a sequential mathematical programming method for finding the least solution to the problem. Since the least solution to the tensor complementarity problem is the sparsest solution to the problem, the method can be regarded as an extension of a recent result by Luo et al. (Optim Lett 11:471–482, 2017). Our limited numerical results show that the method can be used to solve the tensor complementarity problem efficiently.     

Problem with integral condition for a partial differential equation of the first order with respect to time

We investigate the problem with inhomogeneous integral condition for a homogeneous partial differential equation of the first order with respect to time and, in the general case, of infinite order with respect to the space variable with constant coefficients. We prove the existence and uniqueness of a solution of the problem in a class of quasipolynomials of the special form. We construct a solution of this problem with the use of the differential-symbol method. In the case of existence of a nonunique solution of the problem, we propose formulas for the construction of a particular solution of the problem.     

The planar Dirichlet problem for the Stokes equations

The Dirichlet problem for the Stokes equations is studied in a planar domain. We construct a solution of this problem in form of appropriate potentials and determine the unknown source densities via integral equation systems on the boundary of the domain. The solution is given explicitly in the form of a series. As a consequence we determine a solution of the Dirichlet problem for a compressible Stokes system and a solution of a boundary value problem on a domain with cracks. Copyright © 2011 John Wiley & Sons, Ltd.     

To the Solution of the Hilbert Problem with Infinite Index

In this paper, we obtain a generalization of the method of regularizing multipliers for the solution of the Hilbert boundary-value problem with finite index in the theory of analytic functions to the case of an infinite power-behaved index. This method is used to obtain a general solution of the homogeneous Hilbert problem for the half-plane, a solution that depends on the existence and the number of entire functions possessing mirror symmetry with respect to the real axis and satisfying some additional constraints related to the singularity characteristic of the index. To solve of the inhomogeneous problem, we essentially use a specially constructed solution of the homogeneous problem whereby we reduce the boundary condition of the Hilbert problem to a Dirichlet problem.     

Dirichlet problem for the Helmholtz equation in an exterior two-dimensional domain with cuts without matching conditions at the cut endpoints

The Dirichlet problem for the Helmholtz equation in a plane exterior domain with cuts is considered for the case in which functions defined on opposite sides of the cuts in the Dirichlet boundary condition do not necessarily satisfy the matching conditions at the cut endpoints and the solution of the problem is not necessarily continuous at the endpoints of the cuts. We give a well-posed statement of the problem, prove existence and uniqueness theorems for a classical solution, derive an integral representation of the solution, and use it to study its properties. We show that the Dirichlet problem in the considered setting does not necessarily have a weak solution, although there exists a classical solution. We derive asymptotic formulas describing the behavior of the gradient of the solution at the endpoints of the cuts.     

On the properties of solutions of the harmonic Dirichlet problem in a two-dimensional domain with cuts

We consider the Dirichlet problem for the Laplace equation in a plane domain with smooth cuts of arbitrary form for the case in which the solution is not continuous at the endpoints of the cuts. We present a well-posed statement of the problem, prove the existence and uniqueness theorems for the classical solution, obtain an integral representation of the solution, and use it to analyze the properties of the solution. We show that, as a rule, the Dirichlet problem in this setting has no weak solutions, even though there exists a classical solution.     

Solvability of the stationary heat convection problem for a high-viscosity fluid

We study the stationary heat convection problem in the Boussinesq approximation. We derive a priori estimates for its solution. We prove existence and uniqueness theorems for a weak solution of the problem and analyze the smoothness of a weak solution for raised smoothness of the problem data. We consider the two- and three-dimensional cases.     

Convolution solutions of an abstract stochastic Cauchy problem

We study convolution solutions of an abstract stochastic Cauchy problem with the generator of a convolution operator semigroup. In the case of additive noise, we prove the existence and uniqueness of a weak convolution solution; this solution is described by a formula generalizing the classical Cauchy formula in which the solution operators of the homogeneous problem are replaced by the convolution solution operators of the homogeneous problem. For the problem with multiplicative noise, we find a condition under which the weak convolution solution coincides with the soft solution and indicate a sufficient condition for the existence and uniqueness of a weak convolution solution; the latter can be obtained by the successive approximation method.