Mutual synchronization and desynchronization of Lorenz systems

The dynamics of two symmetrically coupled Lorenz systems is investigated by means of a numerical experiment. A bifurcation analysis of the synchronization process is presented. The results are compared with numerical experiments. It is shown that changing the coupling can synchronize or desynchronize the subsystems. Pis’ma Zh. Tekh. Fiz. 24, 22–30 (April 12, 1998)     

Phase synchronization of switching processes in stochastic bistable systems

The concept of an analytic signal is used to show that the stochastic synchronization of bistable systems corresponds to locking of the instantaneous phase of the oscillations in complete agreement with the classical theory of phase synchronization. Pis’ma Zh. Tekh. Fiz. 24, 12–19 (August 12, 1998)     

Appearance of generalized synchronization in mutually coupled beam-plasma systems

The phenomenon of generalized synchronization onset between mutually coupled beam-plasma systems (Pierce diodes) with supercritical currents has been discovered. It is established that the appearance of a synchronous regime is related to the change in one Lyapunov exponent from a positive to negative value. The results of the analysis are confirmed by the nearest-neighbor method.     

Transient processes during synchronization of coupled bistable oscillators with chaotic dynamics

Transient processes in a chain of nonidentical Chua oscillators resistively coupled via nonlinear elements admitting cubic approximation have been numerically simulated in cases of mutual and unidirectional coupling. It is demonstrated that the transient processes during both mutual and induced (unidirectional) chaotic synchronization are enhanced with increasing detuning between the oscillatory circuits of partial subsystems and suppressed with increasing coefficient of coupling. The time of establishment of a synchronous operation regime in the case of mutual coupling is, under otherwise identical conditions, shorter than in the case of unidirectional coupling. The dependence of the duration of establishment of a synchronous operation regime on the moment of coupling switch-on is considered.     

Phase synchronization of switching processes in a stochastic bistable system with an aperiodic external influence

The synchronization of switching in a stochastic bistable system perturbed by a chaotic signal is analyzed. The effect is described in terms of the classical theory of phase synchronization. Pis’ma Zh. Tekh. Fiz. 24, 14–21 (September 26, 1998)     

Duration of the process of complete synchronization of two coupled identical chaotic systems

We consider the time required for complete synchronization of two identical one-way coupled van der Pol-Duffing oscillators occurring in the regime of dynamic chaos. The influence of the initial phase difference between oscillators on the duration of the process of complete synchronization has been studied. At a fixed phase of chaotic oscillations of the self-excited drive oscillator, the period of time (past the coupling onset) during which the complete synchronization regime is established depends on the phase of the self-excited response oscillator.     

Chaotic synchronization in a system of inductively coupled oscillators

A system of two inductively coupled chaotic oscillators is considered. Normalized equations of motion for oscillators with arbitrary parameters are derived in the case of a cubic approximation of the nonlinear elements. The results of a numerical analysis of the features of interaction between chaotic coupled nonidentical subsystems are presented and a realistic experiment is described.     

Noise-induced binary synchronization in nonlinear systems

The phenomenon of noise-induced binary synchronization has been discovered in two independent dynamical systems generating aperiodic binary signals under the action of a common noise source. The presence of a synchronous regime was confirmed by the calculation of Lyapunov exponents for the two systems. The mechanism of development of the noise-induced binary synchronization regime has been found. A relation of the observed regime to binary generalized synchronization is established.

     

Influencing factors of synchronization in manufacturing systems

Manufacturing systems exhibit two types of synchronisation phenomena: logistics and physics. Previous research has established synchronisation measures for both types and has shown that they are related to the due date performance. However, there is a lack of knowledge about the factors triggering synchronisation emergence as well as a holistic understanding of synchronisation effects on logistics performance. Thus, this research aims to further explore the relation between synchronisation, its influencing factors and its effect on logistics performance. Based on a profound literature review, we derive first hypotheses on the cause-and-effect-relationships between structural and dynamic properties of a manufacturing system and the emergence of logistics and physics synchronisation as well as logistics performance. By conducting a discrete-event simulation study on diverse manufacturing system types (line, flow shop and job shop production), we are able to test these hypotheses. We conclude that manufacturing network architecture as a structural property as well as processing time variability and system workload as dynamic properties may be exploited for an advanced and synchronisation-oriented manufacturing system design.     

Generalized synchronization in a system of coupled klystron chaotic oscillators

The phenomenon of generalized chaotic synchronization has been studied in a system of two unidirectionally coupled chaotic oscillators modeling two-sresonator klystron autooscillators. A mechanism explaining the observed behavior is presented.     

A new color image encryption scheme based on chaos synchronization of time-delay Lorenz system

In this paper, a new image encryption scheme is presented based on time-delay chaos synchronization. Compared with existing methods, a new method is proposed and a lot of coupled items can be taken as zero items to simplify the whole system. A simple linear controller is introduced to realize time-delay chaos synchronization and image encryption. The positions of the image pixels are firstly shuffled and then be hidden in the carrier image. The address codes of the chaotic sequences are adopted to avoid the disturbances induced by the initial value and computer accuracy error. Simulation results for color image are provided to illustrate the effectiveness of the proposed method. It can be seen clearly that the system can converge quickly and the image can be encrypted rapidly.     

Recurrent motions and global attractors of non-autonomous Lorenz systems

This paper is devoted to the study of dynamics of non-autonomous Lorenz systems. These systems are formulated and investigated in the context of non-autonomous dynamical systems. First, we prove that such systems admit a compact global attractor and characterize its structure. Then, we obtain conditions of convergence, under which all solutions of the non-autonomous Lorenz systems approach a point attractor. Third, we derive a criterion for existence of almost periodic, quasi-periodic, periodic, and recurrent motions. Finally, we prove a global averaging principle for non-autonomous Lorenz systems.     

Nonautonomous attractors of switching systems

Switching systems formed by switching between a finite number of autonomous ordinary differential equations are formulated as abstract nonautonomous dynamical systems driven by the shift operator on the space of switching controls. A metric is proposed for such switching controls and the space of switching controls with a given positive dwell time is shown to be compact. This allows known results on pullback attractors for nonautonomous dynamical systems to be applied to switching systems including conditions which ensure that a pullback attractor exists and is also a forward attractor. In particular, this provides a conceptual framework for investigating the asymptotic behaviour of switching systems beyond the usual case in which the asymptotic stability of the zero solution under switching is considered.     

Polarization dynamics and non-equilibrium switching processes in ferroelectrics

Time- and temperature-dependent effects are critical for the operation of non-volatile memories based on ferroelectrics. In this paper, we assume a domain nucleation process of the polarization reversal and we discuss the polarization dynamics in the framework of a non-equilibrium statistical model. This approach yields analytical expressions which can be used to explain a wide range of time- and temperature-dependent effects in ferroelectrics. Domain wall velocity derived in this work is consistent with a domain wall creep behavior in ferroelectrics. In the limiting case of para-electric equilibrium, the model yields the well-known Curie law. We also present experimental P-E loops data obtained for soft ferroelectrics at various temperatures. The experimental coercive fields at various temperatures are well predicted by the coercive field formula derived in our theory.     

Nanoscopic processes of current-induced switching in thin tunnel junctions

In magnetic nanostructures, one usually uses a magnetic field to commute between two resistance (R) states. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current, preferably of low intensity. Such current-induced switching (CIS) was recently observed in thin magnetic tunnel junctions and attributed to electromigration of atoms into/out of the insulator. Here, we study the CIS, electrical resistance, and magnetoresistance (MR) of thin MnIr/CoFe/AlO/sub x//CoFe tunnel junctions. The CIS effect at room temperature amounts to 6.9% R-change between the high and low states and is attributed to nanostructural rearrangements of metallic ions in the electrode/barrier interfaces. After switching to the low R-state, some electromigrated ions return to their initial sites through two different energy channels. A low (high) energy barrier of /spl sim/0.13 eV (/spl sim/0.85 eV) was estimated. Ionic electromigration then occurs through two microscopic processes associated with different types of ions sites/defects. Measurements under an external magnetic field showed an additional intermediate R-state due to the simultaneous conjugation of the MR (magnetic) and CIS (structural) effects.     

The time of synchronization of oscillations in two coupled identical subsystems

The mechanism of synchronization of oscillations in two identical coupled flow systems has been studied. The time (past the coupling onset) during which a synchronous oscillation regime is established depends on the oscillation phase difference between the subsystems. Variation of the coupling parameter leads to a change in the character of dependence of the synchronization time on the phase difference. Several types of synchronization processes are revealed, which are realized for various values of the coupling parameter.     

Boundary of generalized synchronization in two unidirectionally coupled tunnel diode generators

The boundary of generalized synchronization regimes in a system of two unidirectionally coupled oscillators based on tunnel diodes has been studied. Peculiarities in the behavior of the boundary are found in the region of relatively large detunings between eigenfrequencies of the two subsystems. The character of this behavior and physical mechanisms leading to the onset of generalized synchronization regimes in the system are explained based on the analysis of evolution of the spectrum of oscillations in the response subsystem.     

Photon storage with nanosecond switching in coupled quantum well nanostructures

Photon storage with nanosecond switching was implemented with indirect excitons in coupled quantum well nanostructures. The storage and release of photons was controlled by the gate voltage pulses. The nanosecond write and readout times were much shorter than the storage time, which reached microseconds. Furthermore, the presented control of excitons on a time scale much shorter than the exciton lifetime demonstrates the feasibility of studying excitons in in situ controlled electrostatic traps.     

The synchronization and entanglement of optomechanical systems

We investigate synchronization and entanglement in two coupled cavity optomechanical systems. The classical synchronization, quantum synchronization and entanglement of the two cavity fields and the two mechanical oscillators are analysed, respectively. Our results show that the two cavity resonators are synchronization without entanglement, while the two mechanical oscillators are entangled with quantum-phase synchronization. We conclude that the quantum synchronization and entanglement have no affirmatory relationship although they are both signature of correlation.