Two families of liapunov functions for functional differential systems

Two families of Liapunov functions are employed to study the global stability and boundedness of functional differential systems. New stability and boundedness theorems are obtained. Applications of these theorems to some nonlinear differential systems with infinite delay are discussed. Project supported by the National Science Foundation of China Under Grants 69871005     

一类二阶系统的定性分析

本文借助于Liapunov第二方法获得了一类二阶系统的若干定理,并推广了[1]的结果．应用获得的定理还解决了实际问题．     

Maps between classifying spaces of Kac-Moody groups

We classify up to homotopy the self-maps of the classifying space of any non-affine Kac-Moody group of rank two.     

时变线性系统的稳定性

本文把文[1]、[2]的变换技巧推广到变系数线性系统(i=1,…,n),用函数方法,研究了n=2、3时零解的稳定性,得到了零解稳定的若干判据.有关系数a_(ij)(t)不必都限制为有界.     

一类一维混沌映射的拓扑条件

20世纪中期以来,人们在物理、天文、气象等领域中发现了大量的混沌现象.这些新发现引发了近几十年来对混沌现象的研究.由于它的困难程度和在解决实际问题中的巨大价值,对混沌现象的研究成为动力系统乃至数学中的一个长期的前沿和热点研究方向.混沌现象最本质的特征是初值敏感性,保证有初值敏感性的一个充分条件是系统具有正Lyapunov指数.因此研究系统是否具有正Lyapunov指数成为研究系统是否出现混沌的重要方法.从拓扑角度给出了一类一维映射出现混沌现象的充分条件.从拓扑的角度来研究,将加深对此类映射出现混沌的机理的认识.研究此类映射,最重要的是研究临界点、临界点轨道及它们的相互关系.我们采用临界点的逆像建立拓扑工具,使用这一拓扑工具分析临界点轨道与临界点的复杂关系,研究临界点逆轨道的运动形态、相应开集的拓扑特征,进而导出系统出现混沌的拓扑特征及它与Lyapunov指数之间的关系.     

一维m次多项式实映射的窗口分析

本文利用作者提出的代数分析法［１］首次严格地给出了一维ｍ次多项式实映射的周期Ｎ轨道窗口个数ＭＮ（ｍ）的显式计算公式，并严格地证明了在反对称映射中存在的对称周期２Ｎ轨道的轨道数目ｒ２Ｎ（ｍ）等于通过周期倍分叉产生的周期２Ｎ轨道的轨道β２Ｎ（ｍ）等结论。     

On the stability of Invariant Capital Stock in a two-dimensional planning model

In this paper, we study the stability of two types of Invariant Capital Stocks which are shown to exist in a two-dimensional planning model. It is shown that, for each type of Invariant Capital Stock, there is a critical discount factor such that when the discount factor falls below it, the corresponding Invariant Capital Stock will become unstable.     

线性离散大系统的稳定性

本文直接运用线性范数型Liapunov函数处理线性定常和时变离散大系统的稳定性,得到了渐近稳定若干判别准则.     

Stability of Hyperbolic and Nonhyperbolic Fixed Points of One-dimensional Maps

We present a complete theory for the stability of non-hyperbolic fixed points of one-dimensional continuous maps. As well as we give simple criteria for the global stability of general maps without using derivatives.     

Topological Anosov Maps of Non-compact Metric Spaces

Let X be a metric space. We say that a continuous surjection f: X→X is a topological Anosov map (abbrev. TA-map) if f is expansive and has pseudo-orbit tracing property with respect to some compatible metric for X. This paper studies the properties of TA-maps of non-compact metric spaces and gives some conditions for the map to be topologically mixing.     

Stability and chaos in a class of 2-dimensional spatiotemporal discrete systems

This paper is concerned with a class of 2-dimensional spatiotemporal discrete systems (2d spatiotemporal discrete systems), or 2-dimensional and 2-directional discrete systems (2d-2D discrete systems). Some sufficient conditions for this system to be stable and some illustrative examples for this system to be chaotic in the sense of Devaney and of Li-Yorke are derived and discussed.     

The Box counting Dimension of Invariant Sets for Iterated Function Systems

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A generalization of the cellular indecomposable property via fiber dimension

The cellular indecomposable property, introduced by Olin and Thomson in 1984 [11], is well known for the Dirichlet space, but it fails trivially for the vector-valued case. The purpose of this paper is to use the fiber dimension to reformulate the property such that it naturally extends the scalar-valued case, yet fix the vector-valued case in a meaningful way. Using the new formulation, we are able to generalize several previous results to the vector-valued setting. In particular, we extend a theorem of Bourdon relating the cellular indecomposable property and the codimension-one property to codimension-N. Several of our results appear to be new even for the Hardy space over the unit disc.     

Geometric Transient Solutions of Autonomous Scalar Maps

Smooth autonomous scalar maps with locally asymptotically stable equilibria have families of asymptotically constant solutions which decay geometrically to the equilibria. Locally, all transients converging to the equilibria have this form.     

On the comparison of the stability and control problem of differential systems

This paper deals with notions which allow us to compare the degree of developments of dynamic systems. The classical definition of stability can be obtained by comparing the considered system with the trivial equation [Xdot] ¦ 0. In the linear cases, this definition leads to the comparison of the top essup - exponents of these systems. We are also concerned with the control problem of Lyapunov exponents for choosing “a stablest system”. The existence of optimal controls is proved     

Contours of Liapunov functions

As is well known, the stability of a dynamical system in two dimensions may be demonstrated in a very intuitive fashion from the existence of a suitable positive-definite Liapunov function, providing the contours of this function in a neighborhood of the stable point are Jordan curves. It is shown that the Liapunov function will certainly have this property if the stable point is an isolated stationary point in the sense of the Clarke calculus, but a counterexample is given if this assumption is weakened to the stable point being an isolated local extremum.This work was carried out with the support of the Natural Sciences and Engineering Council of Canada, which is gratefully acknowledged.     

On the existence of an invariant measure for Markov-Feller operators

Let X be a Polish space and P a Markov operator acting on the space of Borel measures on X. We will prove the existence of an invariant measure with respect to P, provided that P satisfies some condition of a Prokhorov type and that the family of functions is equi-continuous with respect to the Prokhorov distance at some point of the space X. Moreover, we will construct a counterexample which show that the above equi-continuity condition cannot be dropped.     

Self-oscillations of a third order PLL in periodic and chaotic mode and its tracking in a slave PLL

The dynamics of a third order phase locked loop (PLL) with a resonant low pass filter (LPF) has been studied numerically in the parameter space of the system. The range of stable synchronous operating zone of the PLL, expressed in terms of system and signal parameters, is estimated. The obtained results are in agreement with the analytically predicted results in the literature. The PLL dynamics in the unstable region is found to have a sequence of period doubling bifurcation and chaos. In the master–slave mode of operation of two 3rd order PLLs, the slave PLL can track the periodic as well as chaotic dynamics of the master PLL for a narrow range of effective frequency offset when other design parameters are within the stable zone as predicted for an isolated PLL. The synchronization of the master and slave PLLs in this condition is proved to be a generalized one using the auxiliary slave system approach. Experimental observations on prototype hardware circuits for an isolated PLL and for a master–slave PLL arrangement are also given.