准周期外力驱动下Lorenz系统的动力学行为

本文研究了准周期外力驱动下Lorenz系统的动力学行为，发现当外强迫的振幅达到某一个临界值时，系统的动力学行为将会发生根本性的变化，由此揭示了产生非混沌奇怪吸引子(Strange Nonchaotic Attractor, SNA)的一个新机制：准周期外强迫振幅的加大导致系统由奇怪的混沌吸引子转变为SNA，系统的相空间最终被压缩至一个准周期环上.并且本文的结果表明，外强迫的临界振幅与Lorenz系统Rayleigh数的大小成正比，而其受外强迫频率变化的影响并不大. 关键词： 准周期 Lorenz系统 非混沌奇怪吸引子     

The simplest case of a strange attractor

It is shown that stochastic motion of strange attractor type may arise in a system with stable limit cycle if the perturbation of the system is periodical. Analytical and numerical analyses of the conditions for the strange attractor are developed.     

Dissipation effect on chaos onset in a two-resonance overlap case

The problem of two-resonance interaction is considered in the dissipative case. A strange attractor is shown to appear under certain conditions. Hierarchy substructures are obtained when the strange attractor degenerates.     

Structure of strange attractor and homoclinic bifurcation of two-dimensional cubic map

The structure of a strange attractor of the two-dimensional cubic map with jacobian J is investigated in the cases J ≈ 0 and J ≈ 1. The strange attractor has a selfsimilar three-belt structure. The threshold of homoclinic bifurcation is calculated for J ≈ 1.     

NUMERICAL ANALYSIS OF A CHAOTIC SYSTEM

This paper further proves that a single spiral strange attractor can be observed in an extremely simple autonomous electrical circuit by computer simulation. It is of third order and has only one nonlinear element: a three-segment piece-wise linear resistor. The digital analyses show that the strange attractor has peculiar features compared with other third-order differential systems.     

Conversion of a chaotic attractor into a strange nonchaotic attractor in an one dimensional map and BVP oscillator

In this paper we investigate numerically the possibility of conversion of a chaotic attractor into a nonchaotic but strange attractor in both a discrete system (an one dimensional map) and in a continuous dynamical system — Bonhoeffer—van der Pol oscillator. In these systems we show suppression of chaotic property, namely, the sensitive dependence on initial states, by adding appropriate i) chaotic signal and ii) Gaussian white noise. The controlled orbit is found to be strange but nonchaotic with largest Lyapunov exponent negative and noninteger correlation dimension. Return map and power spectrum are also used to characterize the strange nonchaotic attractor.     

Two-parameter families of strange attractors

Periodically driven two-dimensional nonlinear oscillators can generate strange attractors that are periodic. These attractors are mapped in a locally 1-1 way to entire families of strange attractors that are indexed by a pair of relatively prime integers (n(1),n(2)), with n(1)>/=1. The integers are introduced by imposing periodic boundary conditions on the entire strange attractor rather than individual trajectories in the attractor. The torsion and energy integrals for members of this two parameter family of locally identical strange attractors depend smoothly on these integers.     

Scaling of intermittent behaviour of a strange nonchaotic attractor

We describe a type of intermittency present in a strange nonchaotic attractor of a quasiperiodically forced system. This has a similar scaling behaviour to the intermittency found in an attractor-merging crisis of chaotic attractors. By studying rational approximations to the irrational forcing we present a reasoning behind this scaling, which also provides insight into the mechanism which creates the strange nonchaotic attractor.     

Strange Nonchaotic Attractors in a Time-Delay System

A nonchaotic attractor is observed in an infinite-dimensional system which is related to optical bistability and described by a nonlinear time-delay differential equation. The observed nonchaotic attractor is characterized by the strange trajectory of attractor but with negative value for the largest Lyapunov exponent, as well as the Fourier power spectra.     

五维对流模式吸引子的Lyapunov谱

利用Lyapunov谱的算法,计算了五维对流非线性动力系统吸引子的Lyapunov谱及奇怪吸引子的维数。     

Strange attractors are classified by bounding Tori

There is at present a doubly discrete classification for strange attractors of low dimension, d(L)<3. A branched manifold describes the stretching and squeezing processes that generate the strange attractor, and a basis set of orbits describes the complete set of unstable periodic orbits in the attractor. To this we add a third discrete classification level. Strange attractors are organized by the boundary of an open set surrounding their branched manifold. The boundary is a torus with g holes that is dressed by a surface flow with 2(g-1) singular points. All known strange attractors in R3 are classified by genus, g, and flow type.     

A strange attractor in stationary coherent states

An example of the realization of a strange attractor in stationary coherent states is given.     

A generalized Lorenz system

A 14-dimensional generalized Lorenz system of ordinary differential equations is constructed and its bifurcation sequence is then studied numerically. Several fundamental differences are found which serve to distinguish this model from Lorenz's original one, the most unexpected of which is a family of invariant two-tori whose ultimate bifurcation leads to a strange attractor. The strange attractor seems to have many of the gross features observed in Lorenz's model and therefore is an excellent candidate for a higher dimensional analogue.On leave from Department of Mathematics, Howard University, Washington, DC, USAThe National Center for Atmospheric Research is sponsored by the National Science Foundation     

A special type of attractor and transitions in a delayed system

We discuss strange nonchaotic attractors (SNAs) in addition to chaotic and regular attractors in a quasiperiodically driven system with time delays. A route and the associated mechanism are described for a special type of attractor called strange-nonchaotic-attractor-like (SNA-like) through T² torus bifurcation. The type of attractor can be observed in large parameter domains and it is easily mistaken for a true SNA judging merely from the phase portrait, power spectrum and the largest Lyapunov exponent. SNA-like attractor is not strange and has no phase sensitivity. Conditions for Neimark-Sacker bifurcation are obtained by theoretical analysis for the unforced system. Complicated and interesting dynamical transitions are investigated among the different tongues.     

Bifurcations of tori and phase locking in a dissipative system of differential equations

In a system of ordinary differential equations, obtained through a seven-mode truncation of the plane incompressible Navier-Stokes equations, a two-dimensional torus undergoes first two period-doubling bifurcations and then a transition to a strange attractor. This strange attractor, of Liapunov dimension larger than three in a wide parameter interval, is characterized by a power spectrum which retains the two fundamental frequencies of the original torus superimposed on a broad, jagged background. As the Liapunov dimension goes down towards two, an interesting phenomenon of phase locking occurs, which gives rise to an alternation of chaotic and periodic behavior.     

On the realization of the Hunt-Ott strange nonchaotic attractor in a physical system

The object of investigation is a system consisting of two coupled nonautonomous van der Pol oscillators the characteristics frequencies of which differ by a factor of 2. The system is subjected to an external action in the form of slow periodic modulation of an oscillation-controlling parameter and also to an additional action at a frequency that is in an irrational relation with the modulation frequency. It is shown that the variation of the oscillation phase over a modulation period can be approximated by a 2D map on a torus that has a robust (structurally stable) Hunt-Ott strange nonchaotic attractor. Calculations of the quantitative characteristics of the attractor corresponding to the initial set of nonautonomous coupled oscillators (such as phase sensitivity exponent, structures and scaling of rational approximations, as well as Lyapunov exponents and their parameter dependence) confirm the presence of the Hunt-Ott strange nonchaotic attractor.     

A universal strange attractor underlying the quasiperiodic transition to chaos

We use a Monte Carlo approach to study the universal properties associated with the breakdown of two-torus attractors for arbitrary winding numbers. We demonstrate that the renormalization equations have a universal strange attractor, compute its critical exponents, and discuss its structure. The fractal dimension of this attractor is 1.8±0.1.     

On the Dynamics of a Model with Coexistence of Three Attractors: A Point,a Periodic Orbit and a Strange Attractor

For a dynamical system described by a set of autonomous differential equations, an attractor can be either a point, or a periodic orbit, or even a strange attractor. Recently a new chaotic system with only one parameter has been presented where besides a point attractor and a chaotic attractor, it also has a coexisting attractor limit cycle which makes evident the complexity of such a system. We study using analytic tools the dynamics of such system. We describe its global dynamics near the infinity, and prove that it has no Darboux first integrals.     

均匀湍流中的奇怪吸引子

本文对于实测的湍流信号采用延迟坐标重建相空间技术计算了它的关联维数,熵和最大Лялнов指数,从而指出这是一种受随机噪声干扰的确定性的混沌现象,它在相空间的吸引子是一个随机噪声背景上的奇怪吸引子。     

Nonlinear parametric effects and dynamic chaos in a nonautonomous oscillating system with a nonlinear capacitance

A mathematical model is constructed of a nonautonomous dynamic system containing a nonlinear capacitance and possessing a four-dimensional phase space. A numerical investigation is performed of branching processes and phenomena accompanying variations in the frequency and amplitude of an external force. The existence of complex dynamic processes that are a combination of a nonlinear force resonance and a parametric resonance is demonstrated. It is found that both a strange chaotic and a strange nonchaotic attractor exist in the phase space. It is shown that, in the case of a single-frequency external force, the latter attractor exhibits the property of roughness. The results of numerical calculations are confirmed by the results of laboratory experiments.