一个肿瘤生长自由边界问题的研究

本文研究一个描述肿瘤生长的自由边界问题.这个自由边界问题是对Byrne和Chaplain相应肿瘤生长模型的一个改进,研究了该问题解当t→∞时的渐近状况,证明了未血管化的肿瘤体积不会无限制地增大,它或者趋于消失,或者趋于一个休眠态,依营养物浓度的大小和抑制物浓度的大小而定.     

一个肿瘤生长自由边界问题解的渐近性态

该文研究根据Byrne和Chaplain的思想建立的一个描述抑制物作用下无坏死核肿瘤生长的数学模型, 这个模型是一个非线性反应扩散方程组的自由边界问题. 作者运用反应扩散方程理论中的上下解方法结合自由边界问题的迭代技巧, 研究了解的渐近性态, 在营养物消耗函数f、抑制物消耗函数g和肿瘤细胞繁衍函数S的一些一般条件下,证明当常数c₁,c₂(肿瘤细胞分裂速率和营养物、抑制物扩散速率的比值)都非常小时,在一定的初边值条件下肿瘤趋于消失,在另外一些初边值条件下肿瘤半径趋于一个常数,进而时变解将趋于一个稳态解.     

肿瘤生长的自由边界问题

本文介绍肿瘤生长的自由边界问题这一新兴研究方向的研究内容和进展状况.文章首先介绍肿瘤生长的数学建模历史、最新进展和一些重要的肿瘤生长模型,这些模型的数学形式是偏微分方程的自由边界问题.之后介绍近几年人们对这些自由边界问题所做严谨数学理论分析获得的一些主要成果,并简单介绍了证明这些成果用到的数学理论和方法.     

一个药物作用肿瘤生长自由边界问题整体解的存在唯一性

该文研究一个描述药物作用下肿瘤生长的数学模型,这个肿瘤模型是对Jackson模型的一个改进,其数学形式是由一个二阶非线性抛物型方程与两个一阶非线性偏微分方程组耦合而成的自由边界问题.通过运用抛物型方程的L~P理论与一阶偏微分方程的特征方法,并利用Banach不动点定理,证明了该问题存在唯一的整体经典解.     

一个肿瘤生长自由边界问题解的整体存在性和唯一性

该文研究一个反应扩散方程组的自由边界问题,它来源于描述抑制物作用下无坏死核肿瘤生长的数学模型.作者运用抛物型方程的L_p理论和压缩映照原理,证明了这个问题局部解的存在唯一性,然后用延拓方法得到了整体解的存在唯一性.     

一种未血管化肿瘤生长模型整体解的证明

研究了一种未血管化肿瘤生长模型的自由边界问题,模型与此类其它模型有着明显的不同,它引入新的运动项来描述肿瘤内细胞的运动,反映了肿瘤内细胞运动的"接触抑制"性质.运用Banach不动点理论和抛物型方程的L~P理论,证明了模型存在唯一整体解.     

一种肿瘤生长自由边界问题整体解的存在唯一性

研究了一种肿瘤生长模型中自由边界问题，该肿瘤生长模型异于其它此类模型之处就在于采用了新的方式来描述繁衍细胞和休眠细胞的运动．运用抛物型方程的Lp理论和不动点原理，证明了该模型存在唯一的整体解．     

一个反应扩散方程的自由边界问题

该文研究了一个描述原细胞生长的反应扩散方程的自由边界问题.利用非线性分析中的线性化思想和偏微分方程的估计理论,证明了该自由边界问题局部古典解的存在唯一性.     

一个时滞肿瘤生长的自由边界问题

研究了一个时滞肿瘤生长自由边界问题,它来源于描述考虑了由于肿瘤细胞分裂速率变化引起肿瘤细胞生长环境的变化而引起的肿瘤细胞凋亡的肿瘤生长模型.在这个问题中考虑两种因素引起肿瘤细胞消亡:一种是肿瘤细胞度过固有的生命周期后自身的凋亡,另一种是肿瘤细胞的分裂速率变化引起生长环境的变化而引起的肿瘤细胞的凋亡,第二种消亡具有时滞.研究了该问题解的非负性,稳态解的存在唯一性和渐近性以及周期解的存在性.     

带有自由边界的反应扩散系统解的整体存在与爆破（英文）

本文研究一类带耦合非线性反应项的反应扩散系统的自由边界问题.为简便起见,假设条件和解都是径向对称的.首先,利用压缩映射定理,给出正解的局部存在性和唯一性.然后,考虑解的爆破性质和长时间行为.     

离子声波方程的初值问题

本文讨论由Ott E.等建立的机械模型,并给出了该模型初值问题存在整体性弱解的证明。     

用初等行变换求线性矩阵方程的通解

本文通过建立通解矩阵的概念 ,给出了用初等行变换求线性矩阵方程 Am× n Xn× s=Bm× s的通解的方法 .     

Oscillation of neutral delay difference equations of second order with positive and negative coefficients

This paper is concerned with a class of neutral difference equations of second order with positive and negative coefficients of the forms

Multiple periodic solutions for system of first-order differential equation

Sufficient conditions have been obtained for the existence of at least two non-negative periodic solutions to a system of first-order nonlinear functional differential equations. Applications to some ecological models are given.     

Bifurcations and exact traveling wave solutions of the equivalent complex short-pulse equations

In this paper, we study the traveling wave solutions for a complex short-pulse equation of both focusing and defocusing types, which governs the propagation of ultrashort pulses in nonlinear optical fibers. It can be viewed as an analog of the nonlinear Schrodinger (NLS) equation in the ultrashort-pulse regime. The corresponding traveling wave systems of the equivalent complex short-pulse equations are two singular planar dynamical systems with four singular straight lines. By using the method of dynamical systems, bifurcation diagrams and explicit exact parametric representations of the solutions are given, including solitary wave solution, periodic wave solution, peakon solution, periodic peakon solution and compacton solution under different parameter conditions.     

The existence and nonexistence of entire positive solutions of semilinear elliptic systems with gradient term

We show the existence and nonexistence of entire positive solutions for semilinear elliptic system with gradient term Δu+|∇u|=p(|x|)f(u,v), Δv+|∇v|=q(|x|)g(u,v) on RN, N?3, provided that nonlinearities f and g are positive and continuous, the potentials p and q are continuous, c-positive and satisfy appropriate growth conditions at infinity. We find that entire large positive solutions fail to exist if f and g are sublinear and p and q have fast decay at infinity, while if f and g satisfy some growth conditions at infinity, and p, q are of slow decay or fast decay at infinity, then the system has infinitely many entire solutions, which are large or bounded.     

渐近线性算子方程的四种类型的解

利用拓扑度理论及不动点指数理论,讨论了渐近线性算子方程的四种类型的解(即零解、正解、负解和变号解)的存在性,并将这一抽象结果应用于微分方程两点边值问题.     

A class of discrete time generalized Riccati equations

In this paper, a class of discrete-time backward non-linear equations defined on some ordered Hilbert spaces of symmetric matrices is considered. The problem of the existence of some global solutions is investigated. The class of considered discrete-time non-linear equations contains, as special cases, a great number of difference Riccati equations both from the deterministic and the stochastic framework. The results proved in the paper provide the sets of necessary and sufficient conditions that guarantee the existence of some special solutions of the considered equations as: the maximal solution, the stabilizing solution and the minimal positive semi-definite solution. These conditions are expressed in terms of the feasibility of some suitable systems of linear matrix inequalities (LMI). One shows that in the case of the equations with periodic coefficients to verify the conditions that guarantee the existence of the maximal or the stabilizing solution, we have to check the solvability of some systems of LMI with a finite number of inequations. The proofs are based on some suitable properties of discrete-time linear equations defined by the positive operators on some ordered Hilbert spaces chosen adequately. The results derived in this paper provide useful conditions that guarantee the existence of the maximal solution or the stabilizing solution for different classes of difference matrix Riccati equations involved in many problems of robust control both in the deterministic and the stochastic framework. The proofs are deterministic and are accessible to the readers less familiarized with the stochastic reasonings.