Existence and Stability of Positive Solutions for an Elliptic Cooperative System

By discussing the properties of a linear cooperative system, the necessary and sufficient conditions for the existence of positive solutions of an elliptic cooperative system in terms of the principal eigenvalue of the associated linear system are established, and some local stability results for the positive solutions are also obtained.     

Positive and Nontrivial Solutions for the Urysohn Integral Equation

We establish new criteria for the existence of either positive or nonzero solutions of the Urysohn integral equation. We also discuss the existence of an interval of positive eigenvalues and sufficient conditions for the existence of at least a positive eigenvalue with a nonzero or positive eigenfunction for the Urysohn integral operator. Among others, we employ techniques based on fixed point index theory for compact maps, which are new for this type of equation.     

Local and Global Existence of Solutions to Initial Value Problems of Nonlinear Kaup-Kupershmidt Equations

This paper is devoted to studying the initial value problems of the nonlinear Kaup Kupershmidt equations δu/δt ＋ α1 uδ^2u/δx^2 ＋ βδ^3u/δx^3 ＋ γδ^5u/δx^5 = 0, （x,t）∈ E R^2, and δu/δt ＋ α2 δu/δx δ^2u/δx^2 ＋ βδ^3u/δx^3 ＋ γδ^5u/δx^5 = 0, （x, t） ∈R^2. Several important Strichartz type estimates for the fundamental solution of the corresponding linear problem are established. Then we apply such estimates to prove the local and global existence of solutions for the initial value problems of the nonlinear Kaup- Kupershmidt equations. The results show that a local solution exists if the initial function u0（x） ∈ H^s（R）, and s ≥ 5/4 for the first equation and s≥301/108 for the second equation.     

The Existence of Weak Solutions to the 2D Euler Equations with Initial Vorticity in BMO

We shall prove that there exists a weak solution to the 2D Euler equations with initial vorticity in BMO and initial velocity in L^∞.     

Global Existence and Blow-up of Solutions to Multi-dimensional （n ≤ 5） Viscous Cahn-Hilliard Equation

In this paper we consider the viscous Cahn-Hilliard equation with spatial dimension n ≤5, and established global existence of weak solutions for small initial value and blow-up of solutions for any nontrivial initial data.     

Existence and Exponential Stability of Almost Periodic Solution for Hopfield Neural Network Equations with Almost Periodic Imput

By constructing Liapunov functions and building a new inequality, we obtain two kinds of sufficient conditions for the existence and global exponential stability of almost periodic solution for a Hopfield-type neural networks subject to almost periodic external stimuli. In this paper, we assume that the network parameters vary almost periodically with time and we incorporate variable delays in the processing part of the network architectures.     

Standing Waves of the Inhomogeneous Klein-Gordon Equations with Critical Exponent

This paper is concerned with the standing wave in the inhomogeneous nonlinear Klein- Gordon equations with critical exponent. Firstly, we obtain the existence of standing waves associated with the ground states by using variational calculus as well as a compactness lemma. Next, we establish some sharp conditions for global existence in terms of the characteristics of the ground state. Then, we show that how small the initial data are for the global solutions to exist. Finally, we prove the instability of the standing wave by combining the former results.     

Existence and Asymptotic Behavior of Radially Symmetric Solutions to a Semilinear Hyperbolic System in Odd Space Dimensions

This paper is concerned with a class of semilinear hyperbolic systems in odd space dimensions. Our main aim is to prove the existence of a small amplitude solution which is asymptotic to the free solution as t→-∞in the energy norm, and to show it has a free profile as t→ ∞. Our approach is based on the work of [11]. Namely we use a weighted L∞norm to get suitable a priori estimates. This can be done by restricting our attention to radially symmetric solutions. Corresponding initial value problem is also considered in an analogous framework. Besides, we give an extended result of [14] for three space dimensional case in Section 5, which is prepared independently of the other parts of the paper.     

Existence of Weak Solutions of Two-dimensional Euler Equations with Initial Vorticity in Lorentz Space L （2,1） （ R^2）

Some estimates on 2-D Euler equations are given when initial vorticity ω0 belongs to a Lorentz space L(2, 1). Then based on these estimates, it is proved that there exist global weak solutions of two dimensional Euler equations when ωo ∈ L(2, 1).     

On a Solution of the Quaternion Matrix Equation X - A X B = C and Its Application

This paper first studies the solution of a complex matrix equation X - AXB = C, obtains an explicit solution of the equation by means of characteristic polynomial, and then studies the quaternion matrix equation X - A X B = C, characterizes the existence of a solution to the matrix equation, and derives closed-form solutions of the matrix equation in explicit forms by means of real representations of quaternion matrices. This paper also gives an application to the complex matrix equation X - AXB =C.     

Energy concentration for the Landau–Lifshitz equation

For the Landau–Lifshitz equation on a domain with three space dimensions, we consider energy concentration phenomena arising in the context of weakly convergent sequences of solutions. The concentration measure can be interpreted as a family of generalized curves. We establish a connection to a geometric flow.     

Solutions to the Landau–Lifshitz system with nonhomogenous Neumann boundary conditions arising from surface anisotropy and super-exchange interactions in a ferromagnetic media

We study the solutions to the Landau–Lifshitz system in a bilayered ferromagnetic body when super-exchange and surface anisotropy interactions are present at the interface between the layers. We prove the existence of weak solutions in infinite time and strong solutions in finite time.     

Weak martingale solutions to the stochastic Landau–Lifshitz–Gilbert equation with multi-dimensional noise via a convergent finite-element scheme

We propose an unconditionally convergent linear finite element scheme for the stochastic Landau–Lifshitz–Gilbert (LLG) equation with multi-dimensional noise. By using the Doss–Sussmann technique, we first transform the stochastic LLG equation into a partial differential equation that depends on the solution of the auxiliary equation for the diffusion part. The resulting equation has solutions absolutely continuous with respect to time. We then propose a convergent $\theta$-linear scheme for the numerical solution of the reformulated equation. As a consequence, we are able to show the existence of weak martingale solutions to the stochastic LLG equation.     

A numerical method for the Landau–Lifshitz equation with magnetostriction

We present a numerical scheme for Landau–Lifshitz–Gilbert equation coupled with the equation of elastodynamics. The considered physical model describes the behaviour of ferromagnetic materials when magnetomechanical coupling is taken into account. The time‐discretization is based on the backward Euler method with projection. In the numerical approximation, the two equations are decoupled by a suitable linearization in order to solve the magnetic and mechanic part separately. The resulting semi‐implicit scheme is linear and allows larger time‐steps than explicit methods. We prove stability and error estimates for the presented time discretization in 2D. Finally, we test the accuracy of the scheme on an academic numerical example with known exact solution. Copyright © 2005 John Wiley & Sons, Ltd.     

Error estimates for a semi-implicit numerical scheme solving the Landau-Lifshitz equation with an exchange field

^** Email: Ivan.Cimrak{at}ugent.be We study the Landau–Lifshitz (LL) equation describingthe evolution of spin fields in continuum ferromagnets. We considerthe 3D case when the effective field arising in the LL equationincludes exchange interaction, the most challenging case. Thissetting corresponds to the pure isotropic case without a demagnetizingfield. We derive some regularity results for the exact solutionto the LL with Neumann-type boundary conditions. We modify thenumerical scheme studied by A. Prohl in two dimensions and weprove error estimates for this scheme in three dimensions.     

Lienard方程周期解、概周期解的存在性

本文考虑Ｌｉｅｎａｒｄ方程ｘ”十ｆ（ｘ）ｘ’＋ｇ（ｘ）＝ｅ（ｔ），我们得到：当且时，对于任意周期或概周期。数ｅ（ｔ），它有周期或概周期解．而对于Ｌｉｅｎａｒｄ方程ｘ”＋ｆ（ｘ）ｘ’＋ｃｘ＝ｅ（ｔ），我们得到：当ｃ＞０且时，对于任意周期、或概周期函数ｅ（ｔ），它有周期或概周期解．     

On the dynamics of predator-prey models with the Beddington–De Angelis functional response, under Robin boundary conditions

The paper concerns the Beddington–De Angelis predator-prey model, under Robin boundary conditions. General properties—such as boundedness, uniqueness and existence of invariant regions—are obtained. Linear stability (instability) threshold of the equilibrium state S (biologically meaningful) and diffusion-driven instability (Turing effect) are studied. In the framework of nonlinear L ²-energy stability, conditions guaranteeing stability and local attractiveness are obtained.      

一类里卡提方程的两个周期解的存在性和稳定性

研究了一类里卡提方程,得到了方程的两个周期解的存在性和稳定性的充分性条件.     

阿贝尔方程的周期解的存在性和稳定性(英文)

考虑阿贝尔非线性微分方程,得到阿贝尔方程的三个周期解的存在性,并得到其中两个周期解的全局吸引性.     

时滞微分方程概周期解的存在唯一性

应用Liapunov泛函研究时滞微分方程慨周期解的存在唯一性，去掉了要求预先知道系统存在一个有界解的限制条件．