Convergence of Global and Bounded Solutions of Some Nonautonomous Second Order Evolution Equations with Nonlinear Dissipation

In this paper we study the asymptotic behavior of solutions of the following nonautonomous wave equation with nonlinear dissipation.

$\left\{\begin{array}{ll} u_{tt}+\vert u_{t}\vert^{\alpha}u_{t}-\Delta u +f(u)=g(t,x),\quad{\rm in}\,\mathbb{R}_{+}\times\Omega,\\ \qquad\qquad u(t,x)=0,\quad\, {\rm on}\,\mathbb{R}_{+}\times\partial\Omega,\end{array}\right.$

where f is an analytic function, α is a small positive real and g(t, ·) tends to 0 sufficiently fast in L ²(Ω) as t tends to ∞.

We also obtain a general convergence result and the rate of decay of solutions for a class of second order ODE containing as a special case

$\left\{\begin{array}{ll} \ddot{U}(t)+\Vert\dot{U}(t)\Vert^{\alpha}\dot{U}(t)+\nabla F(U(t))=g(t),\quad t \in \mathbb{R}_+,\\ \qquad U(0)=U_{0}\,\in \mathbb{R}^{N},\quad\dot{U}(0)=U_{1}\in \mathbb{R}^{N}. \end{array}\right.$

     

A Remark on the Convergence of Global and Bounded Solutions for a Semilinear Wave Equation on ∝ N

We give a new and easier proof for the result of Feireisl [Fe1] concerning the convergence of global and bounded solutions of the wave equation with small initial energy. We also prove that the convergence takes place with an exponential decay.     

柔性作动器驱动的非线性系统随机振动的最优有界控制

柔性作动器具有低刚度、大变形等特征,这一方面使主结构具备了强的环境适应性,另一方面也使主结构易受外界微扰影响,从而降低其操作精度．本文以介电弹性体作动器驱动的单自由度非线性系统为研究对象,通过即时微调电压,抑制系统在平衡位置附近的随机振动．通过随机平均法降低系统维数,将原系统的控制问题转化为关于慢变过程的控制问题;结合随机动态规划原理及控制约束导出最优有界控制策略．该策略具干摩擦形式,具有能量耗散本质,在抑制系统振动的同时提高了系统的稳定性．数值研究表明：最优有界控制策略具有良好的控制效果、控制效率及较高的鲁棒性．     

Global Solutions of Systems of Nonlinear Impulsive Volterra Integral Equations in Banach Spaces

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｔｈｅｏｒｙｏｆｉｍｐｕｌｓｉｖｅｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｓｈａｓｂｅｅｎｅｍｅｒｇｉｎｇａｓａｎｉｍｐｏｒｔａｎｔａｒｅａｏｆｉｎｖｅｓｔｉｇａｔｉｏｎｓｉｎｒｅｃｅｎｔｙｅａｒｓ (ｓｅｅ [1 ] ) .Ｉｎｐａｐｅｒ [2 ] ,ＧｕｏＤａ＿ｊｕｎｅｓｔａｂｌｉｓｈｅｄｓｏｍｅｅｘｉｓｔｅｎｃｅｔｈｅｏｒｅｍｓｏｆｅｘｔｒｅｍａｌｓｏｌｕｔｉｏｎｓｆｏｒｎｏｎｌｉｎｅａｒｉｍｐｕｌｓｉｖｅＶｏｌｔｅｒｒａｉｎｔｅｇｒａｌｅｑｕａｔｉｏｎｓｏｎａｆｉｎｉｔｅｉｎ…     

一种微机电非线性耦合系统奇点稳定性研究

工程中许多微机电系统都采用电容驱动原理，这类结构实际上存在着强烈的静电和机械两个物理场的非线性耦合，因此系统的动态特性比较复杂。本文基于一种扭转微镜系统，通过数值分析方法，研究其非线性动态特性，根据理论分析和数值计算证明该系统在相平面中存在两个奇点，一个是稳定中心，一个是鞍点，且两个奇点位置均随施加电压的变化而逐渐靠近，从而得出系统的静态分叉点；同时分析了有阻尼和无阻尼时电压的变化对相轨道的影响，以及阻尼对吸合电压的影响，吸合电压随阻尼的增大而提高，这些研究结果不仅对扭转微镜的设计和应用提供了理论和方法，而且对用电容驱动的微机电系统的设计亦有参考价值。     

Stability and Boundedness Results for Solutions of Certain Third Order Nonlinear Vector Differential Equations

In this paper, we investigate the asymptotic stability of the zero solution and boundedness of all solutions of a certain third order nonlinear ordinary vector differential equation. The results are proved using Lyapunov’s second (or direct method). Our results include and improve some well known results existing in the literature.     

Energy Method for Computing Periodic Solutions of Strongly Nonlinear Autonomous Systems with Multi-Degree-of-Freedom

In this paper with the use of conservation of average energy, a newmethod for computing the periodic solutions of strongly nonlinearautonomous systems with multi-degree-of-freedom is suggested. Thismethod cannot only decide the existence, but also give the approximateexpressions of the periodic solutions.     

The Existence Stability and Approximate Expressions of Periodic Solutions of Strongly Nonlinear Nonautonomous Systems with Multi-Degree-of-Freedom

Based upon the conservation of average energy a theorem about the periodic solutions of strongly nonlinear nonautomous systems with multi-degree-of freedom is proved. This theorem can not only decide the existence and stability of the periodic solutions, but at the same time can also give their first-order and second-order approximate expressions.     

Effect of External Excitations on a Nonlinear System with Time Delay

The trivial equilibrium of a two-degree-of-freedom autonomous system may become unstable via a Hopf bifurcation of multiplicity two and give rise to oscillatory bifurcating solutions, due to presence of a time delay in the linear and nonlinear terms. The effect of external excitations on the dynamic behaviour of the corresponding non-autonomous system, after the Hopf bifurcation, is investigated based on the behaviour of solutions to the four-dimensional system of ordinary differential equations. The interaction between the Hopf bifurcating solutions and the high level excitations may induce a non-resonant or secondary resonance response, depending on the ratio of the frequency of bifurcating periodic motion to the frequency of external excitation. The first-order approximate periodic solutions for the non-resonant and super-harmonic resonance response are found to be in good agreement with those obtained by direct numerical integration of the delay differential equation. It is found that the non-resonant response may be either periodic or quasi-periodic. It is shown that the super-harmonic resonance response may exhibit periodic and quasi-periodic motions as well as a co-existence of two or three stable motions.     

Global analysis of some epidemic models with general contact rate and constant immigration

An epidemic models of SIR type and SIRS type with general contact rate and constant immigration of each class were discussed by means of theory of limit system and suitable Liapunov functions. In the absence of input of infectious individuals, the threshold of existence of endemic equilibrium is found. For the disease-free equilibrium and the endemic equilibrium of corresponding SIR model, the sufficient and necessary conditions of global asymptotical stabilities are all obtained. For corresponding SIRS model, the sufficient conditions of global asymptotical stabilities of the disease-free equilibrium and the endemic equilibrium are obtained. In the existence of input of infectious individuals, the models have no disease-free equilibrium. For corresponding SIR model, the endemic equilibrium is globally asymptotically stable ; for corresponding SIRS model, the sufficient conditions of global asymptotical stability of the endemic equilibrium are obtained.     

一类多自由度非线性动力系统周期解的定性分析

应用摄动法的思想和子空间映射的技巧，给出一类多自由度非线性动力系统周期解的存在性、唯一性和稳定性的判别法。该法把问题归结为初等积分的计算。其主要特点是计算简单，应用方便。文后给出了两个例子。     

Weakly Nonlinear Analysis of Convection of a Two-Layer System with a Deformable Interface

The onset of convection in a two-layer system heated from above and below is considered within the framework of the generalized Boussinesq approximations. In the longwave approximation an amplitude equation describing large-scale convective motions accompanied by a deformation of the interface is derived. Two types of steady-state regimes are revealed and their stability is studied.The presence of deformable interfaces and nonuniform heating can initiate instability of the fluid in the gravity field. The interaction between these mechanisms is of considerable theoretical interest. This explains the numerous publications devoted to these themes.     

Global Existence of Solutions in H4 for a Nonlinear Thermoviscoelastic Equations with Non-monotone Pressure

We consider a one-dimensional continuous model of nutron star, which is described by a compressible thermoviscoelastic system with a non-monotone equation of state, due to the effective Skyrme nuclear interaction between particles. We will prove that, despite a possible destabilizing influence of the pressure, which is non-monotone and not always positive, the presence of viscosity and a sufficient thermal dissipation can yield the global existence of solutions in H ⁴ with a mixed free boundary problem for our model.      

STUDY FOR THE BIFURCATION TOPOLOGICAL STRUCTURE AND THE GLOBAL COMPLICATED CHARACTER OF A KIND OF NONLINEAR FINANCE SYSTEM (Ⅰ)

Based on the mathematical model of a kind of complicated financial system, all possible things that the model shows in the operation of our country’s macro-financial system were analyzed, such as balance, stable periodic, fractal, Hopf-bifurcation, the relationship between parameters and Hopf-bifurcations,and chaotic motion etc. By the changes of parameters of all economic meanings, the conditions on which the complicated behaviors occur in such a financial system, and the influence of the adjustment of the macro-economic policies and adjustment of some parameter on the whole financial system behavior were analyzed. This study will deepen people’s understanding of the lever function of all kinds of financial policies.     

On the Long-Time Behaviour of Solutions to the Navier–Stokes–Fourier System with a Time-Dependent Driving Force

In this paper, we give a complete characterization of the asymptotic behaviour of solutions to the Navier–Stokes–Fourier system. We show that either the driving force behaves asymptotically as a gradient of a scalar function, in which case any solution tends to a static state, or the total energy goes to infinity with growing time.     

STUDY FOR THE BIFURCATION TOPOLOGICAL STRUCTURE AND THE GLOBAL COMPLICATED CHARACTER OF A KIND OF NONLINEAR FINANCE SYSTEM(Ⅱ)

Based on the work discussed on the former study, this article first starts from the mathematical model of a kind of complicated financial system, and analyses all possible things that the model shows in the operation of our country’s macro-financial system: balance, stable periodic, fractal, Hopf-bifurcation, the relationship between parameters and Hopf-bifurcation, and chaotic motion etc. By the changes of parameters of all economic meanings, the conditions on which the complicated behaviors occur in such a financial system, and the influence of the adjustment of the macro-economic policies and adjustment of some parameter on the whole financial system behavior have been analyzed. This study will deepen people’s understanding of the lever function of all kinds of financial policies.     

Global Attractor for a Wave Equation with Nonlinear Localized Boundary Damping and a Source Term of Critical Exponent

The paper addresses long-term behavior of solutions to a damped wave equation with a critical source term. The dissipative frictional feedback is restricted to a subset of the boundary of the domain. This paper derives inverse observability estimates which extend the results of Chueshov et al. (Disc Contin Dyn Syst 20:459–509, 2008) to systems with boundary dissipation. In particular, we show that a hyperbolic flow under a critical source and geometrically constrained boundary damping approaches a smooth finite-dimensional global attractor. A similar result for subcritical sources was given in Chueshov et al. (Commun Part Diff Eq 29:1847–1876, 2004). However, the criticality of the source term in conjunction with geometrically restricted dissipation constitutes the major new difficulty of the problem. To overcome this issue we develop a special version of Carleman’s estimates and apply them in the context of abstract results on dissipative dynamical systems. In contrast with the localized interior damping (Chueshov et al. Disc Contin Dyn Syst 20:459–509, 2008), the analysis of a boundary feedback requires a more careful treatment of the trace terms and special tangential estimates based on microlocal analysis.      

一类平面自治非线性时滞控制系统的多稳态和混沌

众所周知,平面自治系统即使具有光滑非线性存在,系统也不会出现复杂的动力学行为。本文研究这样的系统存在时滞时,时滞量对系统的动力学行为的影响。通过对一个平面自治非线性系统引入时滞反馈,得到数学模型。利用泛函分析和平均法建立系统平衡态随时滞量变化的失稳机理,研究表明：时滞量平面自治系统动力学行为的影响是本质的．时滞量不但可以使系统出现Hopf分岔,产生周期振动。而且还可以使系统出现多稳态的周期运动或周期吸引子,这些共存的吸引子相碰是导致系统复杂的动力学行为,包括概周期和混沌运动。     

On the Asymptotic Solutions of Boundary Value Problems for a Class of Systems of Nonlinear Differential Equations (I)

A new method is applied to study the asymptotic behavior of solutions of boundary value problems for a class of systems of nonlinear differential equations . The asymptotic expansions of solutions are constructed, the remainders are estimated. The former works are improved and generalized.     

Double Hopf Bifurcations and Chaos of a Nonlinear Vibration System

A double pendulum system is studied for analyzing the dynamic behaviour near a critical point characterized by nonsemisimple 1:1 resonance. Based on normal form theory, it is shown that two phase-locked periodic solutions may bifurcate from an initial equilibrium, one of them is unstable and the other may be stable for certain values of parameters. A secondary bifurcation from the stable periodic solution yields a family of quasi-periodic solutions lying on a two-dimensional torus. Further cascading bifurcations from the quasi-periodic motions lead to two chaoses via a period-doubling route. It is shown that all the solutions and chaotic motions are obtained under positive damping.