Stable amplitude chimera states and chimera death in repulsively coupled chaotic oscillators

Amplitude chimera states, representing a spontaneous symmetry breaking of a population of coupled identical oscillators into two distinct clusters with one oscillating in spatial coherent amplitude, while the other displaying oscillations in a spatially incoherent manner, have been observed as a kind of transient dynamics in the process of transition to the in-phase synchronization in coupled limit-cycle oscillators. Here, we obtain a kind of stable amplitude chimera state in the chaotic regime of a system of repulsively coupled Lorenz oscillators. With the increment of the coupling strength, the coupled oscillators transit from spatiotemporal chaos to amplitude chimera states then to coherent oscillation death or chimera death states. Moreover, the number of clusters in amplitude chimera patterns has a power-law dependence on the number of coupled neighbors. The amplitude chimera and the chimera death states coexist at certain coupling strength. Moreover, the amplitude chimera and the amplitude death patterns are related to the initial condition for given coupling strength. Our findings of amplitude chimera states and chimera death states in coupled chaotic system may enrich the knowledge of the symmetry-breaking-induced pattern formation.     

Effect of coupling,synchronization of chaos and stick-slip motion in two mutually coupled dynamical systems

In this work, we study the synchronization of two coupled chaotic oscillators. The uncoupled system corresponds to a mass attached to a nonlinear spring and driven by a rolling carpet. For identical oscillators, complete synchronization is analyzed using Lyapunov stability theory. This first analysis reveals that stability area of synchronization increases with the values of the coupling coefficient. Numerical simulations are shown to illustrate and validate stick-slip and chaos synchronization. Some cases of anti-synchronization are detected. Curiously, amplification of fixed point either regular or chaotic is observed in the area of anti-synchronization. Furthermore, phase synchronization is studied for nonidentical oscillators. It appears that for certain values of the coupling coefficient, coincidence of the phases is obtained, while the amplitudes remain uncorrelated. Contrarily to the case of complete synchronization, it does not exist a threshold of the coupling from which phase synchronization could appear. Besides, when we add the modified tuned mass damper on the structure, the behavior of the system can change including the appearance of synchronization, particularly in the region of fixed point. More precisely, complete synchronization is improved in the region of fixed point, while the damage of synchronization is observed when the velocity of the carpets is less than \(0.30\) .     

Periodic orbits,basins of attraction and chaotic beats in two coupled Kerr oscillators

Kerr oscillators are model systems which have practical applications in nonlinear optics. Optical Kerr effect, i.e., interaction of optical waves with nonlinear medium with polarizability χ ⁽³⁾ is the basic phenomenon needed to explain, for example, the process of light transmission in fibers and optical couplers. In this paper, we analyze the two Kerr oscillators coupler and we show that there is a possibility to control the dynamics of this system, especially by switching its dynamics from periodic to chaotic motion and vice versa. Moreover, the switching between two different stable periodic states is investigated. The stability of the system is described by the so-called maps of Lyapunov exponents in parametric spaces. Comparison of basins of attractions between two Kerr couplers and a single Kerr system is also presented.     

Stationary and non-stationary chimeras in an ensemble of chaotic self-sustained oscillators with inertial nonlinearity

We study spatial structures arising in an ensemble of Anishchenko–Astakhov chaotic self-sustained oscillators with non-local coupling. Diagrams of the regimes realizing in this system are constructed numerically. The peculiarities of formation of chimera states appearing with decreasing the coupling strength are analyzed. A new type of the chimera state which is born from the traveling wave regime is demonstrated.

     

Impact of node dynamics parameters on topology identification of complex dynamical networks

This paper aims at investigating the topology identification problem of complex dynamical networks with varying node dynamics parameters and fixed inner coupling matrices. In particular, by employing the unified chaotic system as node dynamics, this work further explores the influence of continuously changing node dynamics parameters on topology identification of complex dynamical networks with different coupling strengths. Results show that for sufficiently small or large coupling strengths, the performance of topology identification is not affected by the change of node parameters. Specifically, for small enough coupling strengths, the topological structure can be completely identified regardless of the change of node parameters, while for sufficiently large coupling strengths, the connectivity (presence and absence of connections) cannot be successfully identified. Furthermore, for certain coupling strengths, with the increase of node dynamics parameters, the topology identification varies from completely unidentifiable to partially or event completely identifiable. Therefore, the synchronization-based topology identification depends on node dynamics. Even for the same node dynamical model, different parameters can have a significant impact on identification results. Furthermore, for networks consisting of chaotic oscillators defining node dynamics, small coupling strengths are conducive to topology identification. A broader conclusion is that projective synchronization, rather than just complete synchronization, is an obstacle to the network topology identification. The findings in this paper will add to our understanding of conditions for identifying topologies of complex networks.     

Diffusive coupling, dissipation, and synchronization

We consider the synchronization of diffusive coupled systems in situations where the synchronization is a consequence of the dissipation in the coupling as well as ones where there is an interaction between the inherent damping in the subsystems and the coupling. It is not required that the subsystems be identical, and they are allowed to have chaotic dynamics. Both discrete and continuous versions are discussed. We also consider coupled oscillators where the dynamics of each oscillator is determined by circuitry across a lossless transmission line.     

Complexity and emergence of wave dynamics in a chain of sequentially interconnected Chua circuits

This paper considers an ensemble of Chua oscillators bidirectionally coupled in a ring geometry where locally coupled circuits form a closed loop of signal transmission. The spontaneous dynamics of this system is studied numerically for different coupling strength. A transition from periodic to chaotic regimes is observed when the coupling decreases. In the former situation, characterized by high coupling, all the circuits oscillate with pseudo-sinusoidal dynamics on periodic attractors; in the latter they evolve on the same-type of chaotic attractor with a progression of the dynamics from the Chua's spiral to the double scroll as the coupling decreases. The emerging global dynamics is markedly different in the two cases and a phase transition between highly ordered and highly disordered global dynamics is observed. Synchronization and traveling waves moving along the ring are identified in the non-chaotic regime, while spatio-temporal chaos results for very low coupling. Complex patterns formation appears at the “edge of chaos”, for a small couplings interval after the transition between these two regimes.     

Integrability and Lie symmetry analysis of deformed $${\varvec{N}}$$ N -coupled nonlinear Schrödinger equations

Nonlinear Dynamics - We investigate the transition between oscillatory and amplitude death (AD) states and the existence of death islands in intrinsic time-delayed chaotic oscillators under the...     

The complete synchronization condition in a network of piezoelectric micro-beams

This work deals with the dynamics of a network of piezoelectric micro-beams (a stack of disks). The complete synchronization condition for this class of chaotic nonlinear electromechanical system with nearest-neighbor diffusive coupling is studied. The nonlinearities within the devices studied here are in both the electrical and mechanical components. The investigation is made for the case of a large number of coupled discrete piezoelectric disks. The problem of chaos synchronization is described and converted into the analysis of the stability of the system via its differential equations. We show that the complete synchronization of N identical coupled nonlinear chaotic systems having shift invariant coupling schemes can be calculated from the synchronization of two of them. According to analytical, semi-analytical predictions and numerical calculations, the transition boundaries for chaos synchronization state in the coupled system are determined as a function of the increasing number of oscillators.

     

Phase Dependent Mechanosensitivity in Cardiomyocytes

Cardiomyocytes are mechanosensitive. In the functioning heart, discrete sets of cardiac oscillators maintain stable relative phase dynamics and mechanical coupling between each other through the elastic tissue. A few questions that remains elusive to date are, how strong is the coupling and how tunable is their dynamics, whether this coupling is phase dependent, and if so, at what phase of cardiac dynamics is the coupling most dominant. In other words, at which phase of its dynamics a cardiac cell is most sensitive to forces and deformations induced by its neighbors. Here we address these questions by culturing rat cardiomyocytes on a stretchable substrate. We apply cyclic stretch on the substrate with a range of frequencies in the vicinity of the intrinsic beating frequency of the cell cluster. We find that the cell cluster can synchronize its dynamics with that of the substrate within 25% of its intrinsic frequency in less than a minute. However, it takes much longer time to return to its intrinsic frequency after removal of substrate stretch. With increasing substrate frequency, the cluster tends to catch up, and beats with a range of frequencies between the intrinsic and the applied with wide variation in relative phases. This allows us to measure phase dependent mechano-sensitivity of the cardiac cluster to the periodic deformation of the substrate that is critical to produce stable relative phase dynamics. We find that cardiac cells are most mechano sensitive when they are at 1/2 of their phase. This phase dependence might be mediated by the ion channels active at this phase of the dynamics. This study identifies a functional output of sub-second scale mechanotransduction with the potential to enhance or reinforce cardiac contractile dynamics.

     

控制混沌振动的逆系统方法

本文研究了控制混沌振动的逆系统控制。建立了单自由度混沌振动的逆系统控制。以一个呈现混沌姿态运动的航天器动力学模型为例说明了该控制律的应用。最后将该控制律多自由度非线性动系统。     

Lyapunov spectrum of chaotic maps with a long-range coupling mediated by a diffusing substance

We investigate analytically and numerically coupled lattices of chaotic maps where the interaction is non-local, i.e., each site is coupled to all the other sites but the interaction strength decreases exponentially with the lattice distance. This kind of coupling models an assembly of pointlike chaotic oscillators in which the coupling is mediated by a rapidly diffusing chemical substance. We consider a case of a lattice of Bernoulli maps, for which the Lyapunov spectrum can be analytically computed and also the completely synchronized state of chaotic Ulam maps, for which we derive analytically the Lyapunov spectrum.     

Parameter estimation for chaotic systems using a geometric approach: theory and experiment

A method for estimating model parameters based on chaotic system response data is described. This estimation problem is made challenging by sensitive dependence to initial conditions. The standard maximum likelihood estimation method is practically infeasible due to the non-smooth nature of the likelihood function. We bypass the problem by introducing an alternative, smoother function that admits a better-defined maximum and show that the parameters that maximize this new function are asymptotically equivalent to maximum likelihood estimates. We use simulations to explore the influence of noise and available data on model Duffing and Lorenz oscillators. We then apply the approach to experimental data from a chaotic Duffing system. Our method does not require estimation of initial conditions and parameter estimates may be obtained even when system dynamics have been estimated from a delay embedding.     

Adaptive nonsingular terminal sliding mode control for synchronization of identical Φ 6 oscillators

The main goal of this paper is to propose the adaptive nonsingular terminal sliding mode controllers for complete synchronization (CS) and anti-synchronization (AS) between two identical ?? ⁶ Van der Pol or Duffing oscillators with presentations of system uncertainties and external disturbances. Unlike directly eliminating the nonlinear items of synchronized error system for sliding mode control schemes in the literature, the proposed adaptive controllers can tackle the nonlinear dynamics without active cancellation. The controllers can be implemented without known bounds of system uncertainties and external disturbances. Meanwhile, the feedback gains are not determined in advance but updated by the adaptive rules. Sufficient conditions are given based on the Lyapunov stability theorem and numerical simulations are performed to verify the effectiveness of presented schemes. The results show that the chaotic synchronization can be achieved accurately by the chattering free control.     

Nonlinear dynamics and small damping signal control of chaos in a model of flow-induced oscillations of cylinders

Nonlinear dynamics of flow-induced oscillations of cylinders is investigated. The approach in our paper is made to introduce an harmonic forced vibration in the coupling term of the structural equation since this may be the consequence of approximating the potential force that could act as a periodic excitation. The method of multiple scales is used to determine the steady state responses. Amplitude and phase modulation equations as well as external force-response and frequency-response curves are obtained. We show that harmonic excitation can induce resonance phenomena in the oscillation of the structure for a range of frequencies of potential force, and also lock-in phenomena appear in the structure part. Also, we find that the structure can be damaged as the amplitude of the potential excitation increases. Numerical simulations confirm the existence of chaotic vibration in the system, a small damping signal control is used to suppress it since it may cause fatigue in the system. The model developed is expected to yield better results for structure in water.     

Chaos synchronization of two different chaotic complex Chen and Lü systems

This paper investigates the phenomenon of chaos synchronization of two different chaotic complex systems of the Chen and Lü type via the methods of active control and global synchronization. In this regard, it generalizes earlier work on the synchronization of two identical oscillators in cases where the drive and response systems are different, the parameter space is larger, and the dimensionality increases due to the complexification of the dependent variables. The idea of chaos synchronization is to use the output of the drive system to control the response system so that the output of the response system converges to the output of the drive system as time increases. Lyapunov functions are derived to prove that the differences in the dynamics of the two systems converge to zero exponentially fast, explicit expressions are given for the control functions and numerical simulations are presented to illustrate the success of our chaos synchronization techniques. We also point out that the global synchronization method is better suited for synchronizing identical chaotic oscillators, as it has serious limitations when applied to the case where the drive and response systems are different.     

Dynamical Order in Systems of Coupled Noisy Oscillators

We investigate a dynamical order induced by coupling and/or noise in systems of coupled oscillators. The dynamical order is referred to a one-dimensional topological structure of the global attractor of the system in the context of random skew-product flows. We show that if the coupling is sufficiently strong, then the system exhibits one dimensional dynamics regardless of the strength of noise. If the coupling is weak, then it is shown numerically that the system also exhibits one dimensional dynamics provided the noise is sufficiently strong. We also show that for any coupling and any noise, the system has a unique rotation number and hence all the oscillators tend to oscillate with the same frequency eventually (frequency locking). Dedicated to Professor Pavol Brunovsky on the occasion of his 70th birthday.     

The research on Cournot–Bertrand duopoly model with heterogeneous goods and its complex characteristics

This paper details the research of the Cournot–Bertrand duopoly model with the application of nonlinear dynamics theory. We analyze the stability of the fixed points by numerical simulation; from the result we found that there exists only one Nash equilibrium point. To recognize the chaotic behavior of the system, we give the bifurcation diagram and Lyapunov exponent spectrum along with the corresponding chaotic attractor. Our study finds that either the change of output modification speed or the change of price modification speed will cause the market to the chaotic state which is disadvantageous for both of the firms. The introduction of chaos control strategies can bring the market back to orderly competition. We exert control on the system with the application of the state feedback method and the parameter variation control method. The conclusion has great significance in theory innovation and practice.     

Complex dynamics and targeted energy transfer in linear oscillators coupled to multi-degree-of-freedom essentially nonlinear attachments

We study the dynamics of a system of coupled linear oscillators with a multi-DOF end attachment with essential (nonlinearizable) stiffness nonlinearities. We show numerically that the multi-DOF attachment can passively absorb broadband energy from the linear system in a one-way, irreversible fashion, acting in essence as nonlinear energy sink (NES). Strong passive targeted energy transfer from the linear to the nonlinear subsystem is possible over wide frequency and energy ranges. In an effort to study the dynamics of the coupled system of oscillators, we study numerically and analytically the periodic orbits of the corresponding undamped and unforced hamiltonian system with asymptotics and reduction. We prove the existence of a family of countable infinity of periodic orbits that result from combined parametric and external resonance interactions of the masses of the NES. We numerically demonstrate that the topological structure of the periodic orbits in the frequency–energy plane of the hamiltonian system greatly influences the strength of targeted energy transfer in the damped system and, to a great extent, governs the overall transient damped dynamics. This work may be regarded as a contribution towards proving the efficacy the utilizing essentially nonlinear attachments as passive broadband boundary controllers. PACS numbers: 05.45.Xt, 02.30.Hq