半线性热方程整体解的存在性与非存在性

本文研究半线性热方程的初值问题ｕｔ－Δｕ＝ｕγ（γ＞１），ｕ（ｘ，０）＝φ（ｘ）的非负古典解与Ｌｐ解的整体存在性、非存在性与ｂｌｏｗ－ｕｐ．首先，利用归一化的高斯函数得到了一些新的解的非整体存在的充分条件，这些条件对古典解与Ｌｐ解是普遍适用的；然后又讨论了某些非负整体解的存在性．本文不但得到了一些新的结果，而且还简化和统一了某些已知结果的证明．     

一阶中立型差分方程非振动解的分类

讨论了中立型差分方程的非振动解.首先由非振动解的渐进性质把非振动解分成两类.其次分别给出存在这两类非振动解的充分条件.最后给出例子说明定理的应用.     

奇异扰动的p-Laplace方程非负非平凡解和正解的结构

精确地刻画了某些奇异扰动的p-Laplace方程非负非平凡解和正解的结构．利用上下解方法证明，方程存在很多非负非平凡的尖峰解和正的过渡尖峰解．当参数充分小时还对每个尖峰解支集的上下界进行了估计．     

四阶边值问题的非负解

讨论了一类四阶非线性常微分方程两点边值问题非负解的存在性.利用锥不动点指数理论得到了方程存在非负解的充分条件.     

一类具有HollingⅢ型食饵—捕食系统的周期解存在性

利用重合度理论中的延拓定理研究非自治周期食饵—捕食系统的非平凡周期解存在性,给出了周期解存在的充分条件.     

一类高阶非线性中立型差分方程组非振动解的存在性

研究了一类高阶非线性中立型差分方程组非振动解的存在性.利用Banach空间的压缩映象原理,获得了该方程组存在非振动解的充分条件.     

一类二阶脉冲微分方程三点边值问题三个非负解的存在性

研究一类二阶脉冲微分方程三点边值问题三个非负解的存在性,利用Leggett-Williams不动点定理得到了方程三个非负解存在的充分条件.     

非线性年龄结构种群的平衡解

讨论一类总数依赖非线性年龄结构种群模型的动力特性，给出了系统的一个等价问题，并讨论了系统的平衡解和非平衡解，得到了平衡解和非平衡解存在的充要条件。     

一类非线性反应扩散方程组的定性分析

本文对化学反应理论中出现的一类非线性反应扩散方程组进行定性分析。文中证明了发展方程组的非负解的存在唯一性以及平衡方程组的非负解的存在性;分析了非负平衡解的渐近稳定性。讨论表明,在齐次的第三类边值条件下,方程组的平凡解是渐近稳定的;但对于齐次的Neumann边值条件,平凡解不渐近稳定。对于一般情况文中给出了非负平衡解渐近稳定的充分条件。最后证明了在扩散系数b_4(i=1,2,3)足够大时,非负平衡解是渐近稳定的。     

一类分数阶脉冲微分方程Dirichlet边值问题非平凡解的存在性

研究了一类带有脉冲的分数阶微分方程Dirichlet边值问题非平凡解的存在性.通过利用变分法和Morse理论证明了此分数阶脉冲微分方程至少存在一个非平凡解.     

On the convective Cahn-Hilliard equation with degenerate mobility

In this paper, we study the existence of weak solutions for the convective Cahn-Hilliard equation with degenerate mobility. Based on the Schauder type estimates, we establish the global existence of classical solutions for regularized problems. After establishing some necessary uniform estimates on the approximate solutions, we prove the existence of weak solutions. The nonnegativity and the finite speed of propagation of perturbations of solutions are also discussed.     

Existence of solutions of the nonautonomous abstract Cauchy problem of second order

In this paper the existence of solutions of a nonautonomous abstract Cauchy problem of second order is considered. Assuming appropriate conditions on the operator of the equation, we establish the existence of mild solutions and, in some cases, we construct an evolution operator associated to the homogeneous equation. Using this evolution operator we obtain existence of solutions for the inhomogeneous equation. Finally, we apply our results to study the existence of solutions of the nonautonomous wave equation.     

Multibump solutions for discrete periodic nonlinear Schrödinger equations

In this paper, we study the existence of multibump solutions for discrete nonlinear Schrödinger equations with periodic potentials. We first reduce the existence of multibump homoclinic solutions to the existence of an isolated homoclinic solution with a nontrivial critical group. Then, we study the existence of homoclinics with nontrivial critical groups for both superlinear and asymptotically linear discrete periodic nonlinear Schrödinger equations, and we provide simple sufficient conditions for the existence of homoclinics with nontrivial critical groups in the positive definite case. As an application, we get, without any symmetry assumptions, infinitely many geometrically distinct homoclinic solutions with exponential decay at infinity.     

中立型泛函微分方程的周期解

对于中立型泛函微分方程,证明了解的毕竟有界性蕴含周期解的存在性,把常微分方程中著名的Yoshizawa周期解存在定理推广到中立型泛函微分方程,然后利用所得结果给出一类产生于电力系统的中立型时滞泛函微分方程周期解存在惟一与吸引的条件。     

三维空间中半线性波动方程组的整体解和自相似解

本文证明了一类半线性波动方程组Cauchy问题整体解的存在唯一性．特别地,证明了自相似解的存在唯一性．同时还得到了渐近自相似解．     

Nagumo and Landesman-Lazer type conditions for nonlinear second order systems

We study the existence of solutions for a nonlinear second order system of ordinary differential equations under various boundary conditions. Assuming suitable Nagumo type conditions we prove the existence of at least one solution applying the method of upper and lower solutions. Moreover, using topological degree methods we prove the existence of solutions under Landesman-Lazer type conditions.     

On the existence of periodic solutions for differential inclusions

In this paper we study the existence of periodic solutions for differential inclusions. We prove existence theorems under various sets of hypotheses for both the nonconvex and convex problems. Also we show the existence of extreme solutions. Some feedback control systems are also considered.     

Existence of solutions of non-autonomous second order functional differential equations with infinite delay

In this paper the existence of solutions of a non-autonomous abstract retarded functional differential equation of second order with infinite delay is considered. Assuming the existence of an evolution operator corresponding to the associate abstract Cauchy problem of second order, we establish the existence of mild solutions of the functional equation. Furthermore, we study the existence of classical solutions of the abstract Cauchy problem of second order and we apply these results to establish the existence of classical solutions of the functional equation. Finally, we apply our results to study the existence of solutions of the non-autonomous wave equation with delay.     

Periodic Solutions of Classical Hamiltonian Systems without Palais-Smale Condition

In this paper, we study the existence of periodic solutions for classical Hamiltonian systems without the Palais-Smale condition. We prove that the information of the potential function contained in a finite domain is sufficient for the existence of periodic solutions. Moreover, we establish the existence of infinitely many periodic solutions without any symmetric condition on the potential function V.     

The studies of systems of variational inclusions problems and variational disclusions problems with applications

In this paper, we study existence theorems of solutions for systems of variational inclusions problems and systems of variational disclusions problems. From these existence results, we establish existence theorems of solutions for systems of generalized vector quasiequilibrium problems and systems of quasioptimization problems.