HILBERT空间中散逸动力系统一般线性方法的散逸稳定性

１．引言 １９９４年,Ｓｔｕａｒｔ与 Ｈｕｍｐｈｒｉｅｓ［４,５］首先考察了用 Ｒｕｎｇｅ－Ｋｕｔｔａ方法求解 Ｒｍ中的散逸动力系统（２．１）－（２．２）时数值解是否继承真解具有的散逸稳定性,并表明代数稳定且不可约的 Ｒｕｎｇｅ－Ｋｕｔｔａ方法是散逸稳定的且有一有界吸引集．１９９６年,本文作者［１］把这一工作推广到了两类特殊的一般线性方法．１９９７年,Ｈｉｌｌ在［３］中证明了Ａ－稳定是单支方法散逸稳定的充要条件,在［２］中又把文［４,５］的工作推广到了 Ｈｉｌｂｅｒｔ空间中的散逸动力系统（２．１）－（…     

广义KdV—Burgers方程吸引子的谱逼近

１引言近年来．随着对无限维动力系统研究的深入,人们对非线性发展方程解的渐近性态了解得越来越多．例如对某些耗散的非线性发展方程,象Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程、Ｋｕｒａｍｏｔｏ－Ｓｉｖａｓｈｉｎ－ｓｋｙ方程等都存在整体的吸引子．系统的渐近性质和系统的复杂性完全由整体吸引子所确定（详细请参见［３］）．与此同时,这类系统的有限维逼近也是人们非常关心的问题,在这方面已有许多工作,如Ｊ．Ｋ．Ｈａｌｅ等人在［５］中基于有限元方法研究了某些非线性发展方程．得到了近似吸引子是上半连续的;Ｃ．Ｍ．Ｅｌｌｏｔｔａ…     

一个与G－分次环和G－集的Smash积有关的Maschke－Type定理

对任意群Ｇ，［１］研究了有单位元１的Ｇ－分次环与有限可迁Ｇ－集的Ｓｍａｓｈ积．在本文中，我们对任意可迁Ｇ－集Ａ讨论了具有局部单位元的Ｇ－分次环与Ｇ－集Ａ的Ｓｍａｓｈ积，证明了有关的一个Ｍａｓｃｈｋｅ－ｔｙＰｅ定理．推广了［２］［３］中的一些重要结果．     

浅水方程近岸行为的数值模拟

二维浅水流动几乎仅在水平方向上,这一特点容许在数学形式上对ＮＳ方程进行简化：通过描述水流运动的平均行为而使得问题降低一维［１０］,从而在数值上表现为大大减少计算量,这一相对简单性正是浅水方程之所以吸引如此多的计算数学家和流体力学家关注的原因之一．通过降维而减少计算量的思想在深水方程中表现为通过边界积分法而捕捉气液交界面的行为［１］． 浅水方程的数值模拟在计算机出现的早期就开始得到应用．在本世纪四十年代后期,Ｃｈａｒｎｅｙ等人就利用它做了大气的数值模拟［２］,Ｈａｎｓｅｎ数值模拟了海洋流动［５］．…     

铁磁链Landau-Lifshitz方程的显式差分法

正如在研究流体动力学时,Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程起着十分重要的作用一样,在对于非平衡态磁学的研究中,描述连续铁磁体自旋场发展过程的 Ｌａｎｄａｎ－Ｌｉｆｓｈｉｔｚ方程［１］起着十分重要的作用［２］．一九九三年,美国和印度签署了一个大约 ２８０万美元的合作研究计划,在三年的时间里,对Ｌａｎｄａｕ－Ｌｉｆｓｈｉｔｚ铁磁链方程进行研究．在无阻尼的情况下,它为一完全可积的孤立子系统［３,４,５］。很多物理学家研究了它的孤立子解的存在性、逆散射方法以及相互碰撞［３,４,５］．关于解的存在性, Ａｌｏｎ…     

方程u_(tt)=u_(xxt) f(u_x)_x初边值问题的差分法

１．引言方程是在国内外引起广泛关注的一类重要的非线性发展方程．文［１］在函数ｆ（ｓ）满足局部 Ｌｉｐ－ｓｃｈｉｔｚ条件及单调性条件（ｆ（ｓ２）－ｆ（ｓ１））（ｓ２－ｓ１）＞ ０的假设下得到了（１．１）初边值问题整体弱解的存在与唯一性;文［２］用 Ｇａｌｅｒｋｉｎ方法,研究了（１．１）的初边值问题,周期边值问题和初值问题,并在函数ｆ’（ｓ）下方有界的假设下得到了整体强解的存在与唯一性． 本文在有限区域 ＱＴ＝［０,１］×［０,Ｔ］（Ｔ＞ ０）上讨论方程（１．１）带有初值条件和边值条件（ｕ（ｘ,ｔ）为未知…     

G-集分次模与Morita Context

对任意群Ｇ， Ｈ≤Ｇ，［１］研究了Ｇ－分次环Ｒ与有限可迁Ｇ－集的ｓｍａｓｈ积.在本文中我们对任意可迁Ｇ－集，讨论了一个关于Ｒ（Ｈ）与ｓｍａｓｈ积Ｒ＃Ｇ／Ｈ的Ｍｏｒｉｔａ ｃｏｎｔｅｘｔ，从而推广了［２］，［３］，［４］给出的关于Ｇ－分次环及其与群Ｇ的ｓｍａｓｈ积的一些重要结果．     

粘流－无粘干扰流动理论变分问题迭代序列的收敛性和算子方程性质

本文证明了粘流－无粘干扰流动理论［１，２］基本控制方程─—简化的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程变分问题几种迭代序列的收敛性，并探讨了其算子方程的性质。本文的结论对于简化Ｎ－Ｓ方程的数值计算具有指导意义。     

环状区域中的轴对称Kuramoto-Sivashinsky方程的整体吸引子

在本文中，环状区域中的轴对称Ｋｕｒａｍｏｔｏ－Ｓｉｖａｓｈｉｎｓｋｙ方程的有限维整体吸引子被得到了．     

高维空间中半线性波动方程的Sobolev指数

ＧｕｓｔａｖｏＰｏｎｃｅ与ＴｈｏｍａｓＣ．Ｓｉｄｅｒｉｓ［４］猜测对一些具有特殊非线性项的半线性波动方程，如ｕｔ－△ｕ＝ｕｋ（Ｄｕ）α（ｘ∈Ｒｎ，ｋ∈Ｚ＋，ｌ＝｜α｜２），其中Ｓｏｂｏｌｅｖ指数会在ｎ２与（ｎ２＋１）之间．文［４］中，在ｘ∈Ｒ３时，回答了这一问题．本文在ｎ３维空间中，得到了半线性波动方程ｕｔ－△ｕ＝ｕｋ（Ｄｕ）α（ｘ∈Ｒｎ，ｋ∈Ｚ＋，ｌ＝｜α｜２）的Ｓｏｂｏｌｅｖ指数为ｍａｘ｛ｎ２＋１２，（ｎ２－１）·ｌ－３ｌ－１＋２｝，此数确实在区间［ｎ２＋１２，ｎ２＋１］中．     

θ-方法求解广义延时微分方程系统的GP-稳定性

本文研究了用θ方法求解广义延时微分方程系统的GP 稳定性,分析了θ方法的稳定性型态.证明了基于Lagrange插值的θ方法是GP 稳定的当且仅当1/2≤θ≤1.单支θ方法是GP 稳定的当且仅当θ=1.     

Numerical controllability of fractional dynamical systems

In this paper, we provide a computational procedure for controlled state and steering control for linear and nonlinear fractional dynamical systems of order 1 < α ≤ 2 in finite-dimensional spaces using the Mittag-Leffler matrix function and the iterative technique. Some numerical examples are provided to illustrate the results.     

Positive role of multiplication noise in attaining complete synchronization on large complex networks of dynamical systems

In this paper, the role of multiplicative noise in attaining complete synchronization on large complex networks of dynamical systems is investigated by theoretical analysis and numerical simulations. Based on the stability theory of stochastic differential equation, we prove that the multiplicative noise plays a positive role in attaining synchronization if the complex networks of dynamical systems are bounded. Moreover, the theoretical result shows that smaller second eigenvalue of coupling matrix is of benefit in attaining complete synchronization. To demonstrate the correctness of theoretical results, the coupled Lorenz systems, Hindmarsh–Rose neuronal systems and Rössler-like systems are performed as numerical examples.     

A natural order in dynamical systems based on Conley–Markov matrices

We introduce a natural order to study properties of dynamical systems, especially their invariant sets. The new concept is based on the classical Conley index theory and transition probabilities among neighborhoods of different invariant sets when the dynamical systems are perturbed by white noises. The transition probabilities can be determined by the Fokker–Planck equation and they form a matrix called a Markov matrix. In the limiting case when the random perturbation is reduced to zero, the Markov matrix recovers the information given by the Conley connection matrix. The Markov matrix also produces a natural order from the least to the most stable invariant sets for general dynamical systems. In particular, it gives the order among the local extreme points if the dynamical system is a gradient-like flow of an energy functional. Consequently, the natural order can be used to determine the global minima for gradient-like systems. Some numerical examples are given to illustrate the Markov matrix and its properties.     

Adaptive synchronization in tree-like dynamical networks

Synchronization in an array of coupled identical nonlinear dynamical systems have attracted increasing attention from various fields of science and engineering. In this paper, we investigate the synchronization phenomenon in tree-like dynamical networks. Based on the LaSalle invariant principle, a simple and systematic adaptive control scheme with variable coupling strength is proposed for the synchronization of tree-like dynamical networks without any knowledge of the concrete structure of isolate system. This result indicates that synchronization can be achieved for strong enough coupling if there exists a system (located at the root of the tree) which directly or indirectly influences all other systems. Furthermore, the main result is applied to several Lorenz chaotic systems coupled by a tree. And numerical simulations are also given to show the effectiveness of the proposed synchronization method.     

Martelli’s Chaos in Inverse Limit Dynamical Systems and Hyperspace Dynamical Systems

In this paper we investigate Martelli’s chaos of inverse limit dynamical systems and hyperspace dynamical systems which are both induced from dynamical systems on a compact metric space. We give the implication of Martelli’s chaos among those systems. More precisely, we show that inverse limit dynamical system is Martelli’s chaos if and only if so is original system, and we prove that hyperspace dynamical system is Martelli’s chaos implies original system is Martelli’s chaos if the orbit of every single point set of original system is unstable in hyperspace dynamical system.     

Stability of random attractors under perturbation and approximation

The comparison of the long-time behaviour of dynamical systems and their numerical approximations is not straightforward since in general such methods only converge on bounded time intervals. However, one can still compare their asymptotic behaviour using the global attractor, and this is now standard in the deterministic autonomous case. For random dynamical systems there is an additional problem, since the convergence of numerical methods for such systems is usually given only on average. In this paper the deterministic approach is extended to cover stochastic differential equations, giving necessary and sufficient conditions for the random attractor arising from a random dynamical system to be upper semi-continuous with respect to a given family of perturbations or approximations.     

Global Existence and Blow-up for a Parabolic System with Nonlinear Boundary Conditions

This paper deals with the global existence and blow-up of positive solutions to the systems: u_t = ∇(u^∇u) + u¹ + v^a v_t = ∇(v^n∇v) + u^b + v^k in B_R × (0, T) \frac{∂u}{∂η} = u^αv^p, \frac{∂v}{∂η} = u^qv^β on S_R × (0, T) u(x, 0) = u_0(x), v(x, 0} = v_0(x) in B_R We prove that there exists a global classical positive solution if and only if l ≤ l, k ≤ 1, m + α ≤ 1, n + β ≤ 1, pq ≤ (1 - m - α)(1 - n - β),ab ≤ 1, qa ≤ (1 - n - β) and pb ≤ (1 - m - α).     

广义同步化流形的Holder连续性

证明了两个不同的混沌系统线性耦合时能实现广义同步化,在一定条件下广义同步化流形是Holder连续的.采用的思想是Temam的无穷维动力系统的惯性流形理论的改进.在线性耦合下两个混沌系统具有吸收集和吸引子的基础上,通过定义在一个函数类上的映射满足Schauder不动点定理,从而得到广义同步化流形,该广义同步化流形具有不变性.又证明了存在分数维的指数吸引子,指数吸引子与广义同步流形的交集具有指数吸引性.数值仿真证实了理论的正确性.在驱动系统和响应系统外引入辅助系统,辅助系统与响应系统的完全同步化表明了驱动系统和响应系统的广义同步化.     

查甫雷金方程的唯一性定理(Ⅲ)

<正> 考虑下列混合型方程的唯一性问题K(y)u_(xx)+u_(yy)=0(K(0)=0;当y≠0时,dK/dy>0).(1)所考虑的区域由三条曲线围成.其一是双曲区域中由原点引出的特征线Г_1,它满足下面方程