Internal Stabilization of a Mutualistic Reaction Diffusion System

We study the internal stabilization of steady-state solutions to a 2-species mutualistic reaction diffusion system via finite-dimensional feedback controllers. Our main idea is to use different internal controllers to stabilize different steady-state solutions. The controllers axe provided by considering LQ problems associated with the lineaxized systems at steady-state solutions.     

Slow Time-periodic solutions of the cubic-quinitic Ginzburg-Landau equation

In this paper, the Ginzburg-Landau equation with small complex coefficients is considered. A translation is introduced to transform the Ginzburg-Landau equation into a dynamical system. Moreover, the existence and the properties of the equilibria are discussed. The spatial quasiperiodic solutions disappear due to the perturbation are proved. Finally, several types of heteroclinic orbits are proposed and numerical analysis are provided.     

A Slow Transient Diffusion in a Drifted Stable Potential

We consider a diffusion process X in a random potential of the form , where is a positive drift and is a strictly stable process of index with positive jumps. Then the diffusion is transient and converges in law towards an exponential distribution. This behaviour contrasts with the case where is a drifted Brownian motion and provides an example of a transient diffusion in a random potential which is as “slow” as in the recurrent setting.      

Reconstruction of the Space-dependent Source from Partial Neumann Data for Slow Diffusion System

Consider a linear inverse problem of determining the space-dependent source term in a diffusion equation with time fractional order derivative from the flux measurement specified in partial boundary. Based on the analysis on the forward problem and the adjoint problem with inhomogeneous boundary condition,a variational identity connecting the inversion input data with the unknown source function is established.The uniqueness and the conditional stability for the inverse problem are proven by wea...     

一类切换线性系统的慢切换镇定设计

研究一类线性切换系统的慢切换镇定设计问题.基于时间驱动和状态反馈驱动相结合的思想,在系统存在稳定凸组合的基础上介绍了非保守的切换设计.对切换线性系统设计了两种新的切换规则,分别使系统渐近稳定和指数稳定在设计的切换规则下,类李雅普诺夫函数在状态反馈期允许增加固定的比例.切换设计不仅能降低切换频率还能给出状态驱动持续时间的一个下界.最后,数例仿真验证了切换设计的有效性.     

Global Null Controllability of the 1-Dimensional Nonlinear Slow Diffusion Equation

The authors prove the global null controllability for the 1-dimensional nonlinear slow diffusion equation by using both a boundary and an internal control. They assume that the internal control is only time dependent. The proof relies on the return method in combination with some local controllability results for nondegenerate equations and rescaling techniques.     

输入带有时滞的线性系统的镇定

考虑带有输入时滞的线性系统的镇定问题.通过把时滞写成一阶传播方程,带有输入时滞的镇定问题转化为常微分方程和一阶双曲方程组成的串联系统的镇定问题.与现有Backstepping方法不同,文章给出了新的变换,其核函数是一阶倒向向量值常微分方程,这使得控制的设计更加简单.文章给出了新的状态反馈控制器,并证明了闭环系统解的适定性和指数稳定性.数值模拟说明,给出的方法是非常有效的.     

Study on a Cross Diffusion Parabolic System

This paper considers a kind of strongly coupled cross diffusion parabolic system,which can be usedas the multi-dimensional Lyumkis energy transport model in semiconductor science.The global existence andlarge time behavior are obtained for smooth solution to the initial boundary value problem.When the initialdata are a small perturbation of an isothermal stationary solution,the smooth solution of the problem under theinsulating boundary condition,converges to that stationary solution exponentially fast as time goes to infinity.     

一类反应扩散方程组的局部能控性

本文证明了一类反应扩散方程组平衡解的局部精确能控性.     

一类反应扩散系统的分歧与斑图

本文研究了一类发生在密闭容器中的不可激活的高次自催化反应扩散系统．在适当的条件下,用渐进近似的方法讨论了系统平衡态的稳定范围;用多重尺度的方法证明了当扩散系数λ充分小时,系统出现两种类型的斑图,一类是由Hopf分歧引出的驻波斑图;另一类是由 Pitchfork分歧引出的定波斑图．进一步还讨论了,在分歧点附近,对于大于空间或等于空间波数的小扰动,斑图是局部稳定的,而小于自身空间波数的小扰动,斑图是不稳定的．     

一维广义Ginzburg－Landau方程的指数吸引子

本文在[1]的基础上,得到了一维广义Ginzburg-Landau方程的指数吸引子的存在性。     

一类竞争扩散系统的二重固有值分岐

本文讨论一类反应扩散方程组,它刻画了栖息在同一有界区域内的两个种群的群体密度的变化状况.我们以种群的出生率α和b作分歧参数,讨论了在二重固有值处的分歧并得到了存在性及稳定性的结果.     

复合弹性系统边界反馈镇定的Riesz基方法

考虑一个航天器控制实验室实验模型的振动镇定问题。证明了高阶微分线性反馈的闭环系统是一个Riesz系统,即系统存在一列广义本征函数列构成状态空间的Riesz基。从而系统的谱确定增长条件成立。在此过程中,简单的导出了系统本征值的渐近展开式。并因些推论出系统的指数稳定性的条件。     

Ginzburg-Landau equation with magnetic effect in a thin domain

We study the Ginzburg-Landau equation with magnetic effect in a thin domain in , where the thickness of the domain is controlled by a parameter . This equation is an Euler equation of a free energy functional and it has trivial solutions that are minimizers of the functional. In this article we look for a nontrivial stable solution to the equation, that is, a local minimizer of the energy functional. To prove the existence of such a stable solution in , we consider a reduced problem as and a nondegenerate stable solution to the reduced equation. Applying the standard variational argument, we show that there exists a stable solution in near the solution to the reduced equation if is sufficiently small. We also present a specific example of a domain which allows a stable vortex solution, that is, a stable solution with zeros. Received: 11 May 2001 / Accepted: 11 July 2001 /Published online: 19 October 2001     

Inhomogeneous Current States in a Gauged Two-Component Ginzburg-Landau Model

We consider the energy bounds of inhomogeneous current states in doped antiferromagnetic insulators in the framework of the two-component Ginzburg-Landau model. Using the formulation of this model in terms of the gauge-invariant order parameters (the unit vector n, spin stiffness field ρ², and particle momentum c), we show that this strongly correlated electron system involves a geometric small parameter that determines the degree of packing in the knots of filament manifolds of the order parameter distributions for the spin and charge degrees of freedom. We find that as the doping degree decreases, the filament density increases, resulting in a transition to an inhomogeneous current state with a free energy gain.__________Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 1, pp. 182–189, July, 2005.     

Hopf Bifurcations in a Predator-Prey Diffusion System with Beddington-DeAngelis Response

This paper is concerned with a two-species predator-prey reaction-diffusion system with Beddington-DeAngelis functional response and subject to homogeneous Neumann boundary conditions. By linearizing the system at the positive constant steady-state solution and analyzing the associated characteristic equation in detail, the asymptotic stability of the positive constant steady-state solution and the existence of local Hopf bifurcations are investigated. Also, it is shown that the appearance of the diffusion and homogeneous Neumann boundary conditions can lead to the appearance of codimension two Bagdanov-Takens bifurcation. Moreover, by applying the normal form theory and the center manifold reduction for partial differential equations (PDEs), the explicit algorithm determining the direction of Hopf bifurcations and the stability of bifurcating periodic solutions is given. Finally, numerical simulations supporting the theoretical analysis are also included.     

Ginzburg-Landau Vortices in Inhomogeneous Superconductors

We study the vortex convergence for an inhomogeneous Ginzburg-Landau equation, -Δu = ∈^{-2}u(a(x) - |u|²), and prove that the vortices are attracted to the minimum point b of a(x) as ∈ → 0. Moreover, we show that there exists a subsequence ∈ → 0 such that u_∈ converges to u strongly in H¹_{loc}(\overline{Ω} \ {b}).     

Slow Initial Convergence of GMRES for SUPG Discretized Convection‐Diffusion Problems

When GMRES [6] is applied to streamline upwind Petrov Galerkin (SUPG) discretized convection‐diffusion problems, its residual norms typically exhibit an initial period of slow convergence. For a model problem we offer a quantitative explanation of this behavior and relate it to the boundary conditions.