不稳定型二阶中立型方程正解的存在性与有界振动

本文研究一类不稳定型二阶中立型微分方程正解的存在性与有界振动．证明了在一定条件下不稳定型二阶中立型方程总存在无界正解，并给出了保证其方程的一切有界解都振动的充分条件，改进了文［１，２］中的有关条件．     

一类具正负系数中立型方程的正解

研究一类具有正负系数的中立型微分方程,得到了这类方程存在正解的充分条件和存在有界正解的充要条件,并据此给出了其存在无界正解的充分条件。     

三阶非线性非自治中立型时滞差分方程正解存在性定理

研究了一类三阶非线性变系数非自治中立型变时滞差分方程正解的存在性,给出了该类方程存在最终正解的几个充分条件,推广了已有文献的某些结果.     

一类三阶非线性中立型分布时滞微分方程的振动性北大核心

研究一类三阶非线性中立型分布时滞微分方程的振动性.利用算子和积分技巧分别给出了不存在引理中提到的i)型正解和ii)型正解的判定条件,进而借助适当的比较定理,建立了判别该类方程振动的若干新的充分条件,所得定理推广和改进了最近文献中的若干结果.结果充分反映了时滞在方程振动中的影响作用.     

中立型时滞差分方程的振性与正解存在性

本文研究了一类中立型时滞差分方程的振动性和正解存在性，获得了该方程所有解振动的“Sharp”条件及存在正解的一个充分条件．     

一类具有欧拉形式的中立型微分方程的振动性

研究具有欧拉形式的无界时滞中立型微分方程解的振动性，给出了方程振动的几个充分条件。     

一类三阶非线性中立型分布时滞微分方程的振动性

研究一类三阶非线性中立型分布时滞微分方程的振动性.利用算子和积分技巧分别给出了不存在引理中提到的i)型正解和ii)型正解的判定条件,进而借助适当的比较定理,建立了判别该类方程振动的若干新的充分条件,所得定理推广和改进了最近文献中的若干结果.结果充分反映了时滞在方程振动中的影响作用.并给出具体例子用以说明主要结论     

一类具有排斥型奇性的中立型Linard方程周期正解的存在性

利用Mawhin重合度拓展定理,研究一类具有排斥型奇性的中立型Linard方程周期问题.在强奇性条件下,获得周期正解存在性的新结果.本文允许方程在无穷远点具有不定型奇性,改进了已有文献中的相关结论.     

一类二阶非线性中立型差分方程的振动性

研究了二阶非线性中立型差分方程Δ2(xn+pxn-l)+qnf(xn-k)=0的振动性,获得了该类方程振动的三个充分性定理.所得结果将一阶非线性中立型差分方程已有振动性的相应结论推广到了二阶非线性中立型差分方程.     

不稳定的二阶中立型差分方程的振动性

我们研究不稳定的二阶中立型差分方程解的振动问题Δ2[x(n)+px(n-τ)〗+q(n)x(g(n))=0,n>n0(1)建立了不稳定的二阶中立型差分方程(1)无界解的振动准则.     

Positive solutions of a nonlocal singular elliptic equation by means of a non-standard bifurcation theory

We consider a nonlocal elliptic equation arising in a prey–predator model whose nonlocal term is singular. We use the Leray–Schauder degree to prove the existence of an unbounded continuum of positive solutions emanating from the trivial solution. As application, we study nonlocal and singular elliptic equations of the type logistic and Holling–Tanner.     

两端固定的奇异梁方程的多重正解

设 n 是一个任意的自然数. 证明了一个两端固定的奇异梁方程的 n 个正解的存在性, 其中非线性项是一个Carathéodory 函数. 主要工具是涉及非线性项的高度函数与锥压缩锥拉伸型的 Krasnoselskii不动点定理. 进一步的研究表明,如果非线性项在零点和无穷远处的增长极限均为无界函数, 该方程仍可能具有正解.     

The influence of a metasolution on the behaviour of the logistic equation with nonlocal diffusion coefficient

In this paper we use the bifurcation method and fixed point arguments to study a logistic equation with nonlocal diffusion coefficient. We prove the existence of an unbounded continuum of positive solutions that bifurcates from the trivial solution. The global behaviour of this continuum depends strongly on the value of the nonlocal diffusion coefficient at infinity as well as the relative position between the refuge of the species and the weight of the diffusion coefficient. Moreover, we show the complexity of the structure of the set of positive solutions using fixed point arguments.     

Persistence of travelling wave solutions of a fourth order diffusion system

In this paper the extended Burgers–Huxley equation with the fourth-order derivative is considered. First, the convergence to the uniform steady state is proved, which means the solution of the equation with positive initial data will remain positive for time t sufficiently large. Then, the persistence of the travelling wave solution for the extended equation on the unbounded domain is investigated. We have proved that this solution will persist under small perturbation of the equation.     

Stability estimates for a class of semi-linear ill-posed problems

We study a final value problem for a nonlinear parabolic equation with positive self-adjoint unbounded operator coefficients. The problem is ill-posed. The regularized equation is given by a modified quasi-reversibility method. For this regularization solution, the Hölder type stability estimate between the regularization solution and the exact solution is obtained.     

Positive solutions for Neumann problems with indefinite and unbounded potential

We consider semilinear Neumann equations with an indefinite and unbounded potential. We establish the existence and uniqueness of positive solutions. We show that our setting incorporates as special cases several parametric equations of interest (such as the equidiffusive logistic equation).     

Discounted dynamic programming with unbounded returns: Application to economic models

In this paper, we study discounted Markov decision processes on an uncountable state space. We allow a utility (reward) function to be unbounded both from above and below. A new feature in our approach is an easily verifiable rate of growth condition introduced for a positive part of the utility function. This assumption, in turn, enables us to prove the convergence of a value iteration algorithm to a solution to the Bellman equation. Moreover, by virtue of the optimality equation we show the existence of an optimal stationary policy.     

Global structure of positive solution sets of nonlinear operator equations

In this paper we investigate the existence of unbounded maximal subcontinua of positive solution sets of some nonlinear operator equations that bifurcates from infinity. The main feature of the paper is that the nonlinearity may not be of asymptotically linear type and may not be positone. The methods used to show our main results are different from that of Rabinowitz’ well-known global bifurcation theorems and that of some other related papers. We first obtain a sequence of unbounded subcontinua located in a pipe that bifurcates from nontrivial solutions by using a topological degree argument. Then using a result on subcontinua of superior limit in metric spaces we obtain the main results concerning unbounded maximal subcontinua of positive solution sets of the nonlinear operator equation. The main results can be applied to the semipositone problems to obtain the existence of positive solutions.     

一类非线性无界时滞差分方程正解的不存在性

研究一类非线性无界时滞差分方程及其对偶方程，给出了方程不存在正解的充分条件，所得结论改进了有关的结果。     

Nonlinear Integroparabolic Equations on Unbounded Domains: Existence of Classical Solutions with Special Properties

Classical solvability is established for a certain nonlinear integrodifferential parabolic equation, on unbounded domains in several dimensions. The model equation of the Fokker-Planck type represents a regularized version of an equation recently derived by J. A. Acebrón and R. Spigler for the physical problem of describing the time evolution of large populations of nonlinearly globally coupled random oscillators. Precise estimates are obtained for the decay of convolutions with fundamental solutions of linear parabolic equations on unbounded domains in R ⁿ . Existence of a classical solution with special properties is established.