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1.
在脑血动脉瘤的临床研究中,Willis环脑动脉血管瘤系统(Willis aneurysm system,WAS)起着重要作用,分数阶WAS尽管能进一步加深该系统的机理刻画,但是不能描述原因不明的迟发性动脉瘤.鉴于此,本文提出分数阶Willis环脑迟发性动脉瘤时滞系统(fractional Willis aneurysm system with time-delay,FWASTD)并验证了其有效性;利用时间序列图、相图、Poincaré截面等证实了FWASTD的混沌特性;研究时滞对于系统的重要生理参量的影响,发现了血流阻力系数在时滞状态下对系统稳定的重要性;根据分数阶时滞系统的稳定性理论,设计相应线性控制器,对FWASTD进行了有效控制,同时也探讨了时滞系统的自同步控制.本文完善了脑动脉瘤系统的理论基础. 相似文献
2.
The object of this paper is to reveal the relation between dynamics of the fractional system and its dimension defined as a sum of the orders of all involved derivatives. We take the fractional Lorenz system as example and regard one or three of its orders as bifurcation parameters. In this framework, we compute the corresponding bifurcation diagrams via an optimal Poincaré section technique developed by us and find there exist two routes to chaos when its dimension increases from some values to 3. One is the process of cascaded period-doubling bifurcations and the other is a crisis (boundary crisis) which occurs in the evolution of chaotic transient behavior. We would like to point out that our investigation is the first to find out that a fractional differential equations (FDEs) system can evolve into chaos by the crisis. Furthermore, we observe rich dynamical phenomena in these processes, such as two-stage cascaded period-doubling bifurcations, chaotic transients, and the transition from coexistence of three attractors to mono-existence of a chaotic attractor. These are new and interesting findings for FDEs systems which, to our knowledge, have not been described before. 相似文献
3.
M. Lücke 《Journal of statistical physics》1976,15(6):455-475
The dynamics of the Lorenz model in the turbulent regime (r>r
T is investigated by applying methods for treating many-body systems. Symmetry properties are used to derive relations between correlation functions. The basic ones are evaluated numerically and discussed for several values of the parameterr. A theory for the spectra of the two independent relaxation functions is presented using a dispersion relation representation in terms of relaxation kernels and characteristic frequencies. Their role in the dynamics of the system is discussed and it is shown that their numerical values increase in proportion to r. The approximation of the relaxation kernels that represent nonlinear coupling between the variables by a relaxation time expression and a simple mode coupling approximation, respectively, is shown to explain the two different fluctuation spectra. The coupling strength for the modes is determined by a Kubo relation imposing selfconsistency. Comparison with the experimental spectra is made for three values ofr. 相似文献
4.
利用单模激光Lorenz系统实现混沌反控制 总被引:1,自引:0,他引:1
利用Lyapunov函数方法,对混沌反控制问题进行了研究.以单模激光Lorenz系统和描述心脏搏动的Bonhoeffer-Van der Pol系统为例,设计了一种控制器,成功地使Bonhoeffer-Van der Pol系统混沌化.给出了控制器的具体设计方案以及单模激光Lorenz系统与Bonhoeffer-Van der Pol系统状态之间误差系统的结构.仿真结果表明,在控制器的作用下,Bonhoeffer-Van der Pol系统所有状态变量严格地跟踪了单模激光Lorenz系统的混沌轨迹,对应的相空间中Bonhoeffer-Van der Pol系统的轨迹也由极限环转变为与单模激光Lorenz系统的轨迹完全相同的混沌吸引子,Bonhoeffer-Van der Pol系统严格地跟踪了单模激光Lorenz系统混沌的动态行为. 相似文献
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Local bifurcations of stationary points and limit cycles have successfully been characterized in terms of the critical exponents of these solutions. Lyapunov exponents and their associated covariant Lyapunov vectors have been proposed as tools for supporting the understanding of critical transitions in chaotic dynamical systems. However, it is in general not clear how the statistical properties of dynamical systems change across a boundary crisis during which a chaotic attractor collides with a saddle. This behavior is investigated here for a boundary crisis in the Lorenz flow, for which neither the Lyapunov exponents nor the covariant Lyapunov vectors provide a criterion for the crisis. Instead, the convergence of the time evolution of probability densities to the invariant measure, governed by the semigroup of transfer operators, is expected to slow down at the approach of the crisis. Such convergence is described by the eigenvalues of the generator of this semigroup, which can be divided into two families, referred to as the stable and unstable Ruelle–Pollicott resonances, respectively. The former describes the convergence of densities to the attractor (or escape from a repeller) and is estimated from many short time series sampling the state space. The latter is responsible for the decay of correlations, or mixing, and can be estimated from a long times series, invoking ergodicity. It is found numerically for the Lorenz flow that the stable resonances do approach the imaginary axis during the crisis, as is indicative of the loss of global stability of the attractor. On the other hand, the unstable resonances, and a fortiori the decay of correlations, do not flag the proximity of the crisis, thus questioning the usual design of early warning indicators of boundary crises of chaotic attractors and the applicability of response theory close to such crises. 相似文献
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8.
Edgar Knobloch 《Journal of statistical physics》1979,20(6):695-709
We use the theory of stochastic differential equations with rapidly fluctuating coefficients to study the statistical dynamics of the Lorenz model in the turbulent region. On the assumption that the system is ergodic we are able to calculate self-consistently several basic statistical quantities in terms of the parameters of the model. Our results are in good agreement with numerical computations.Supported financially by the Summer Study Program in Geophysical Fluid Dynamics at the Woods Hole Oceanographic Institution. 相似文献
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Chaotic dynamics of the fractional-order Ikeda delay system and its synchronization 总被引:3,自引:0,他引:3 下载免费PDF全文
In this paper we numerically investigate the chaotic
behaviours of the fractional-order Ikeda delay system. The results show
that chaos
exists in the fractional-order Ikeda delay system with order less than 1.
The lowest order for chaos to be able to appear in this system is found
to be 0.1. Master--slave
synchronization of chaotic fractional-order Ikeda delay systems with linear
coupling is also studied. 相似文献
11.
《Physics letters. A》2006,354(4):305-311
In this Letter we numerically investigate the chaotic behaviors of the fractional-order Lü system. A striking finding is that the lowest order for this system to have chaos is 0.3, which is the lowest-order chaotic system among all the found chaotic systems reported in the literature to date. Period-doubling routes to chaos in the fractional-order Lü system are also found. Master–slave synchronization of chaotic fractional-order Lü systems with linear coupling is also studied. 相似文献
12.
The transition from a steady domain structure to turbulence in the electroconvection system of a nematic under the action
of a constant electric field is studied using the methods of optical and acoustic responses. The chaotic dynamics is investigated
both by conventional methods (Fourier signal spectrum) and by methods of nonlinear dynamics. From the quantitative estimates
of basic characteristics of the chaotic behavior (namely, the correlation dimension, leading Lyapunov exponent, K-entropy, and embedding dimension), one can conclude that temporal chaos arises in the system, giving rise to a strange attractor,
as the control parameter increases at ɛ ≥ ɛ
c
≈ 0.5. The fact that the distribution of laminar domains in the liquid-crystal layer depends on their length under the conditions
of developed turbulence indicates that the dynamics of the nematic demonstrates the intermittent behavior. 相似文献
13.
Based on reliable numerical approach, this Letter studies the chaotic behavior of the fractional unified system. The lowest orders for this system to have a complete chaotic attractor (the attractor covers the three equilibrium points of the classical unified system) at different parameter values are obtained. A striking finding is that with the increase of the parameter α of the fractional unified system from 0 to 1, the lowest order for this system to have a complete chaotic attractor monotonically decreases from 2.97 to 2.07. Because of the inherent attribute (memory effects) of fractional derivatives, this finding reveals that the chaotic behavior of fractional (classical) unified system becomes stronger and stronger when α increases from 0 to 1. Furthermore, this Letter introduces a novel measure to characterize the chaos intensity of fractional (classical) differential system. 相似文献
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C. O. Weiss 《Optical and Quantum Electronics》1988,20(1):1-22
Chaotic emission of lasers theoretically predicted long ago has only recently been experimentally verified. A review of experiments on various laser types is given. 相似文献
16.
定义一个动态窗口,以Lorenz模型为预报方程,通过对落入动态窗口中的粒子数和平均预报X分量随积分时间演化规律的分析,从另一个角度初步研究了Lorenz系统的可预报性问题,并讨论了高斯白噪声对系统可预报性的影响.结果表明,落入动态窗口中的粒子数在一定程度上反映了系统的可预报性,处于不同区域的初值集合预报时限各不相同,且不同区域内的初值对于小扰动的敏感程度不一样;对于不同区域内的初值集合,高斯白噪声对系统的可预报时限的影响各不相同.
关键词:
可预报性
Lorenz
动态窗口 相似文献
17.
James H. Curry 《Communications in Mathematical Physics》1978,60(3):193-204
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 相似文献
18.
Mohammad Saleh Tavazoei 《Physica D: Nonlinear Phenomena》2008,237(20):2628-2637
In this paper, based on the stability theorems in fractional differential equations, a necessary condition is given to check the existence of 1-scroll, 2-scroll or multi-scroll chaotic attractors in a fractional order system. This condition is proposed for incommensurate order systems in general, but in the special case it converts to the condition given in the previous works for the commensurate fractional order systems. Though the presented condition is only a necessary (and not sufficient) condition for the existence of chaos it can be used as a powerful tool to distinguish for what parameters and orders of a given fractional order system, chaotic attractors can not be observed and for what parameters and orders, the system may generate chaos. It can also be used as a tool to confirm or reject results of a numerical simulation. Some of the numerical results reported in the previous literature are confirmed by this tool. 相似文献
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We consider a nonlinear oscillator of the Duffing type with fractional derivative of the order 1相似文献