具有性别结构的交错扩散捕食者-食饵模型整体解的存在性和稳定性

应用能量估计方法和Gagliardo-Nirenberg型不等式证明一类具有性别结构的交错扩散捕食者-食饵模型的整体解的存在性和一致有界性,并通过构造Lyapunov函数给出该模型正平衡点全局渐近稳定的充分条件.     

含时滞的非自治单种群扩散模型的概周期解的存在性与全局吸引性

研究了含离散时滞的非自治单种群扩散模型的概周期解的存在性与全局吸引性.通过应用微分方程比较原理和不等式估计方法以及构造适当的Lyapunov函数的方法得到了系统的持久性,概周期解存在唯一性,渐进稳定性以及全局吸引性的充分条件.     

一类糖酵解模型正平衡解的存在性分析

研究生化反应中具有代表性的一类糖酵解模型.运用先验估计讨论非常数正平衡解的不存在性,得到非常数正平衡解存在的必要条件.在常数平衡解Turing不稳定的基础上,利用度理论方法和解的先验估计,进一步给出非常数正平衡解存在的充分条件.     

三种群食物链交错扩散模型古典解的整体存在性和收敛性

应用能量估计方法和bootstrap技巧证明了空间维数不超过5时一类带自扩散和交错扩散项的三种群Lotka-Volterra食物链模型古典解的整体存在性.当反应函数的系数满足一定条件时通过构造Lyapunov函数给出了该模型解的收敛性.     

一个肿瘤侵入模型的定性分析

本文研究由Gatenby和Gawlinski提出的一个肿瘤侵入模型.该模型是一个强耦合的退缩型反应扩散方程组.本文在α12为零,0≤α21＜1的情况下,对该模型进行严格的数学分析.所获结果包括两个方面:(1)解的整体存在性.主要应用了逼近方法,H.Amann关于一般拟线性方程和这类方程与常微分方程耦合而成的广义抛物型方程组解的存在性理论,以及积分估计技术.如何建立解的积分估计是获得这个问题解的整体存在性的关键. (2)解的渐近性态.该模型有EP1,EP2,EP3和EP4四个稳态解,其中EP1和EP2两个平凡稳态解在任何情况下都不稳定.通过构造Lyapunov函数,我们证明了,在一定条件下EP3全局渐近稳定,从而时变解在时间趋于无穷时将趋于EP3,而在相反的条件下EP4全局渐近稳定,从而时变解在时间趋于无穷时将趋于EP4     

一类带有扩散与时滞的流行性传染病模型的行波解

讨论了一类带有扩散与时滞的流行性传染病模型的行波解的存在性.首先,将系统的行波解的存在性问题转化为一个二阶常微分方程组的单调解的存在性问题;应用单调方法和不动点方法,进一步地将问题转化为方程组的上下解的构造问题;应用所建立的引理与定理,通过构造适合的上下解,证明了系统单调行波解的存在性.     

奇摄动问题中脉冲状解的“缝接法”

讨论了一类含有脉冲状解的奇摄动边值问题.由于这类问题自身的不稳定性而无法采用微分不等式方法.利用边界层函数法构造了形式渐近解,并运用"缝接法"证明了问题解的存在性以及进行了余项估计.     

一类广义耦合的非线性波动方程组时间周期解的存在性

研究了一类广义耦合的非线性波动方程组关于时间周期解的问题.首先利用Galerkin方法构造近似时间周期解序列,然后利用先验估计和Laray-Schauder不动点原理,证明近似时间周期解序列的收敛性,从而得到该问题时间周期解的存在性.     

二维空间格上的具有静止阶段的反应扩散系统的整体解

研究一类二维空间格上的具有静止阶段的反应扩散系统的整体解,这里整体解指的是定义在整个空间和时间上的古典解.构造合适的下解和上估计式,利用比较原理,并利用连接稳定态和不稳定态的空间不依赖解和具有不同波速与传播方向的行波解,证明了整体解的存在性和一些定性性质.     

一类Chemostat捕食模型正周期解的存在性

讨论了一类Chemostat捕食模型在一定条件下正周期解的存在性问题.运用周期抛物型算子理论、Schauder估计和分歧理论得到了该模型正周期解存在的充分必要条件.     

Weak and smooth solutions to incompressible Navier-Stokes-Landau-Lifshitz-Maxwell equations

Considering the Navier-Stokes-Landau-Lifshitz-Maxwell equations, in dimensions two and three, we use Galerkin method to prove the existence of weak solution. Then combine the a priori estimates and induction technique, we obtain the existence of smooth solution.     

Nonlinear elliptic differential equations with multivalued nonlinearities

In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is defined on all ℝ. Assuming the existence of an upper and of a lower solution, we prove the existence of a solution between them. Also for a special version of the problem, we prove the existence of extremal solutions in the order interval formed by the upper and lower solutions. Then we drop the requirement that the monotone nonlinearity is defined on all of ℝ. This case is important because it covers variational inequalities. Using the theory of operators of monotone type we show that the problem has a solution. Finally in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity. Using the critical point theory for nonsmooth locally Lipschitz functionals we prove the existence of at least two nontrivial solutions (multiplicity theorem).     

M/M~B/1排队模型的时间依赖解的存在唯一性

应用线性算子的积分半群理论证明 M/MB/1排队模型的时间依赖解的存在唯一性 ,其次推出 M/M/1排队模型的时间依赖解的存在唯一性 .     

浅水波方程的初边值问题

本文用Kato关于拟线性演化方程的初值问题的存在性定理证明了浅水波方程在半无界直线上初值问题局部解的存在性。用解的先估计证明了整体解的存在性或解的Blow-up性质，并给出了解关于x的渐近估计。     

一类四阶非线性抛物型方程的初边值问题

本文证明一类四阶非线性抛物型方程初边值问题整体广义解的存在性和唯一性,以及解的渐近性质,最后给出解爆破的充分条件.     

Blowup,Global Fast and Slow Solutions for a Semilinear Combustible System

In this paper, we investigate a semilinear combustible system $u_t-du_{xx}=v^p, v_t-dv_{xx}=u^q$ with double fronts free boundary, where p ≥ 1, q ≥ 1. For such a problem, we use the contraction mapping theorem to prove the local existence and uniqueness of the solution. Also we study the blowup and global existence property of the solution. Our results show that when pq › 1 blowup occurs if the initial datum is large enough and the solution is global and slow, whose decay rate is at most polynomial if the initial value is suitably large, while when p › 1, q › 1 there is a global and fast solution, which decays uniformly at an exponential rate if the initial datum is small.     

Nonlinear Elliptic Differential Equations with Multivalued Nonlinearities

In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is de_ned on all . Assuming the existence of an upper and of a lower solution, we prove the existence of a solution between them. Also for a special version of the problem, we prove the existence of extremal solutions in the order interval formed by the upper and lower solutions. Then we drop the requirement that the monotone nonlinearity is defined on all of . This case is important because it covers variational inequalities. Using the theory of operators of monotone type we show that the problem has a solution. Finally, in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity. Using the critical point theory for nonsmooth locally Lipschitz functionals we prove the existence of at least two nontrivial solutions (multiplicity theorem).     

On the two-dimensional cauchy problem of a hyperbolic system

In this paper, we prove the global existence of generalized solutions to a two-dimensional Cauchy problem of a hyperbolic system by introducing a new definition of generalized solution. Moreover, the solution may involve delta-wave.     

Differential equations with limit-periodic forcings

The present paper is concerned with scalar differential equations of first order which are limit periodic in the independent variable. Some tools provided by the theories of exponential dichotomies and periodic differential equations are applied to prove that, in a generic sense, the existence of a bounded solution implies the existence of a limit periodic solution.

     

Almost automorphic solutions for some partial functional differential equations

In this work, we study the existence of almost automorphic solutions for some partial functional differential equations. We prove that the existence of a bounded solution on R⁺ implies the existence of an almost automorphic solution. Our results extend the classical known theorem by Bohr and Neugebauer on the existence of almost periodic solutions for inhomegeneous linear almost periodic differential equations. We give some applications to hyperbolic equations and Lotka-Volterra type equations used to describe the evolution of a single diffusive animal species.