Irregular dynamics of a chain of circle maps with quasiperiodic excitation

An analysis is made of the spatial evolution of quasiperiodic regimes in a chain of coupled circle maps. Mechanisms for the appearance of strange nonchaotic dynamics and the properties of irregular attractors are analyzed. Pis’ma Zh. Tekh. Fiz. 23, 73–79 (April 12, 1997)     

Global reconstruction from nonstationary data

One-dimensional time series of a dynamical system with slowly varying parameters are investigated. For estimation of the characteristics of the attractors of such a system which exist for fixed values of the parameters, it is proposed to “cut out” from the time series short segments that belong to the individual attractors and to use them to reconstruct a model dynamical system. Pis’ma Zh. Tekh. Fiz. 25, 74–81 (May 26, 1999)     

Phase multistability in quasiperiodically driven systems

The influence of quasiperiodic driving on phase multistability in coupled Feigenbaum oscillators is investigated. Various new effects associated with strange nonchaotic attractors are observed. Pis’ma Zh. Tekh. Fiz. 25, 49–56 (November 26, 1999)     

Unbounded increase in the dimension of chaotic attractors in linear filtering

An analysis is made of the limiting possibilities for adding complexity to chaotic oscillations in high-order filters. It is found that the limiting dimension of chaotic oscillation attractors in linear filters may increase to infinity, so that deterministic chaotic test oscillations with any desired dimension can be generated. “Kolledzh” State Education and Science Center Pis’ma Zh. Tekh. Fiz. 23, 8–13 (April 12, 1997)     

Application of Mel’nikov’s method for estimating the efficacy of external signals on complex nonlinear systems with strange attractors

Mel’nikov’s method is used as a criterion for determining the condition for the onset of stochastization in nonlinear dynamical systems with strange attractors. Analytical conditions for the onset of stochastization in Duffing systems and Lorenz systems are obtained, from which one can synthesize a control signal ensuring the required behavior of the system. A mathematical experiment is carried out which confirms the correctness of the theoretical analysis. Pis’ma Zh. Tekh. Fiz. 23, 40–45 (December 12, 1997)     

Nonlinear stage of instability evolution in a monostable active medium

A theoretical analysis is made of the nonlinear stage of instability evolution in a monostable active medium described by a “reaction-diffusion” type equation. The boundary of that region of the medium in which instability develops propagates at constant velocity. Group-theoretical analysis of the problem yields an analytic expression for the propagation velocity of this boundary. The results may be important for the analysis of instability evolution in a wide range of active media. Pis’ma Zh. Tekh. Fiz. 24, 10–15 (July 26, 1998)     

Lifetimes of Chaotic Attractors in a Multidimensional Laser System

Abstract

The lifetimes of chaotic attractors at crises in a multidimensional laser system are studied. This system describes the CO₂ laser with modulated losses and is known as the four-level model. The critical exponents which are related to the lifetimes of the attractors are estimated in terms of the corresponding eigenvalues and the measured characteristic lifetimes in the model. The critical exponents in this model and those of its centre manifold version are in good agreement. It is conjectured that generically in the four-level model the critical exponents are close to ½ at crises. In addition, predictions of the simpler and popular two-level model are compared with those of the above-mentioned models     

Indication of the presence or absence of convective motion in water by nuclear magnetic resonance

Nuclear magnetic resonance was used to determine the characteristic parameters for the evolution of an ensemble of gas bubbles in a liquid exposed to microwave irradiation. These parameters can be used to determine whether convective motion takes place in the liquid. It is observed that a liquid may be “strengthened” by low-intensity radio waves. Pis’ma Zh. Tekh. Fiz. 24, 87–90 (September 26, 1998)     

Dynamic recrystallization in a near-eutectic Pb-Sn-Ag alloy under thermal cycling

An analysis is made of the behavior of solders under thermal cycling. Dynamic recrystallization can be used to explain the evolution of the microstructure of soldered joints during operation. Pis’ma Zh. Tekh. Fiz. 24, 28–31 (May 12, 1998)     

Domain instability in an ensemble of dislocations during plastic deformation of crystals

An analysis is made of the nonlinear dynamics of perturbations of the dislocation density and elastic field using a proposed evolution model which takes into account the negative velocity sensitivity of the deforming stresses. As a result of the evolution of domain instability, it is observed that periodic and isolated solutions (solitons) exist for the initial variables. Pis’ma Zh. Tekh. Fiz. 24, 42–48 (April 26, 1998)     

Near-wall electron instability of a plasma flux

Experimental data are obtained which indicate some characteristic features of the plasma-surface interaction leading to the emission of electrons from the walls of the accelerating channel and the evolution of a specific beam instability of the plasma flux. Pis’ma Zh. Tekh. Fiz. 23, 47–52 (May 26, 1997)     

Vortex structures in a ceramic under high-velocity impact

A finite-element method in a two-dimensional axisymmetric formulation is used to analyze the characteristics of shock-wave processes in a ceramic plate under the impact of a high-speed cylinder. It is established that a vortex structure is formed and the evolution of the vortices is investigated. Pis’ma Zh. Tekh. Fiz. 23, 86–90 (December 26, 1997)     

Multistable generation of monochromatic radiation in solid-state lasers

It is shown that a solid-state laser with unpumped sections of action medium which act as a saturable absorber, may operate in a stable, single-mode cw lasing regime. The establishment of lasing in a particular mode under steady-state conditions depends on the initial conditions of transient evolution. Pis’ma Zh. Tekh. Fiz. 24, 89–92 (February 26, 1998)     

Nonequilibrium structural transitions as a mechanism of turbulence

A possible mechanism for turbulence is proposed and substantiated for the first time, whereby turbulence is considered as a nonequilibrium transition in ensembles of defects of the microscopic shear type, which are treated as real defects in the molecular structure of liquids. A statistical foundation is given for the evolution equations for the tensor order parameter, which characterizes an ensemble of such defects and has the meaning of nonequilibrium fluctuations of the strain rate. The types of macroscopic fluctuation modes of the strain rate are determined as self-similar solutions of the evolution equations for this tensor order parameter under conditions of nonequilibrium transitions, and qualitative correspondences are established between these solutions and real scenarios for the transition to turbulence. The Kolmogorov scaling laws (the natures of the “viscous” and “ inertial” intervals) are explained for fully developed turbulence. Pis’ma Zh. Tekh. Fiz. 23, 81–88 (July 12, 1997)     

Evolution of the morphological structure of a two-dimensional cluster obtained with a linear microparticle trajectory in the diffusion-limited aggregation regime

Two-dimensional diffusion-limited aggregation of spherical microparticles was achieved experimentally as a result of their rectilinear motion (“ballistic aggregation”) at a “water-air” interface. A percolation cluster was obtained and the evolution of its morphological parameters was studied under compression. A change in the orientation of the cluster pores and a nonlinear coalescence and breakup process were observed. A fabrication technology is proposed for monolayer films similar to the Langmuir method. Pis’ma Zh. Tekh. Fiz. 25, 80–85 (December 12, 1999)     

Characteristic time for the evolution of instability of a droplet charged to the Rayleigh limit

The nonlinear problem of the capillary oscillations of a charged droplet is solved to estimate the characteristic time for the evolution of instability of a droplet carrying critical charge. It is observed that breakup is delayed because of the hydrodynamic inertia of the droplet. Pis’ma Zh. Tekh. Fiz. 25, 41–45 (August 12, 1999)     

Characteristics of microwave beam breakdown in nitrogen and oxygen

The time evolution of the electron density in microwave discharges in nitrogen and oxygen has been investigated. It is shown that the kinetic processes of electron detachment from negative ions or associative ionization of electronically excited gas molecules play a significant role in the interaction between above-threshold microwave radiation and a discharge plasma. Pis’ma Zh. Tekh. Fiz. 23, 74–80 (May 26, 1997)     

Modulation of capillary oscillations of a charged drop of low-viscosity liquid by its elastic oscillations

A second-order linear differential equation describing the temporal evolution of the amplitudes of capillary waves in a drop of low-viscosity liquid with elastic properties is given with a complex coefficient multiplying the first derivative. It is shown that the capillary oscillations of the drop are modulated by its oscillations associated with the relaxation of the viscosity of the liquid. Pis’ma Zh. Tekh. Fiz. 24, 83–87 (April 12, 1998)     

Distribution laws for microplastic deformations

Calculations and construction of bispectra are used to show that the deviation of the probability density of microplastic deformations from a normal distribution law is a measure of the evolution of synchronization effects and a measure of the completeness of the relaxation processes determining the plasticity of the material. Pis’ma Zh. Tekh. Fiz. 24, 28–30 (July 26, 1998)