Pull-in and pull-out effects in synchronization of chaotically modulated oscillations

We study the synchronization effects of chaotically modulated oscillations of two unidirectional coupled chaos generators based on a typical phase-locked system. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Institute of Applied Mathematics and Cybernetics, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1525–1530, December, 1998.     

Bifurcations of oscillations of the membrane potential and the use of mappings for modeling electrically coupled neurons

In this paper, we present the results of a qualitative analysis of a generalized system of three differential equations that represent the neuron model. The main nontrivial bifurcation sets leading to the appearance of complex motions, i.e., bursts, are given. A two-dimensional mapping that models the flows generated by this system, which is considered to be the simplest model of a neuron, is proposed. The chaotic dynamics of diffusely coupled neurons is studied using the coupled mappings. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State Univesity of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1572–1580, December, 1998.     

Analysis of regularization processes in an ensemble of coupled chaotic oscillators

We study how the collective dynamics of an ensemble of active coupled elements depends on the number of connections between them. We use Chua’s nonlinear oscillators as elements of this ensemble and assume nonlinear coupling. Regularization and suppression of oscillations in the transition from global to local coupling are examined. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1558–1564, December, 1998.     

Dynamics of spatial structures in arrays of nonlocally coupled bistable units

We present the results of investigation of a dynamical system consisting of nonlocally coupled bistable units. The dynamics of spatial structures in an array with a gradually increasing coupling coefficient is studied. The formation of spatial structures in the case of strong nonlocal coupling between units is examined. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Volga State Academy of Water Transport, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1581–1585, December, 1998.     

Complex oscillations in a system of coupled autogenerators with phase control

We study dynamical modes and bifurcations in a two-loop self-oscillatory system with phase control. The evolution of self-excited oscillations as a function of the initial frequency detuning is presented. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Applied Mathematics and Cybernetics, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1604–1611, December, 1998.     

Method of local statistical equivalence and induced transitions in dynamical systems perturbed by weak noise

We propose a method of local statistical equivalence which in some cases reduces, under condition of small noise intensity, the analysis of the statistical characteristics of noise-induced transitions in dynamical systems to solution of a similar problem in simpler systems. For a system of coupled analytical bistable elements, we found analytical expressions (and compared them with the results of numerical simulation) to estimate the average times of transitions due to changes in the parameter, as counterparts of nonstationary phase transitions of the first and second order. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp 1543–1550, December, 1998.     

Nonlinear dynamics of a backward-wave tube under the condition of competition of two modes

We study the nonlinear dynamics of backward-wave tubes in the regime of interaction of an electron flux with two transverse modes. In the region where the threshold values of parameters are slightly exceeded, one can observe a stationary single-mode oscillation when the other mode is suppressed, which is in good agreement with experimental observations of the competition of two modes in the relativistic backward-wave tube. It is shown that nonlinear competition can lead to the establishment of a single-mode stochastic regime of oscillation in the wide range of parameters in which the conditions of stochastic self-modulation are fulfilled for each mode individually. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1565–1571, December, 1998.     

Estimation of the global stability domain in a chain of correlated phase-locked systems by the methods of image recognition theory

We formulate the problem and present the results of estimation of the global stability domain of the equilibrium state in a chain of correlated phase-locked systems by the methods of image recognition theory. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1612–1615, December, 1998.     

Nonstationary processes in a gyrotron with reflections from output-section inhomogeneities

We study the influence of some types of reflections on oscillatory processes in gyrotrons. Estimates of the conditions of oscillation stability in the presence of a reflected signal are given. The processes in a gyrotron with a fixed structure of the RF field are numerically simulated. The enhancement of the signal spectrum in the presence of reflections is studied. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1616–1622, December, 1998.     

Synchronized oscillations in a system of two coupled van-der-pol-duffing oscillators

The results of analysis of the periodic solutions obtained within the framework of complete and truncated equations for a system of identical Van-der-Pol-Duffing oscillators with nonlinear coupling are compared. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1531–1536, December, 1998.     

A model of a neuron with oscillatory activity below the excitation threshold

We propose a dynamic model of a neuron with spontaneous periodic oscillations below the excitation threshold. Such neurons, in particular, play an important role in the problem of coordination of motions by the brain specifying the universal rhythm of muscular contractions. The model is constructed on the basis of the known model dynamic systems and is described by a system of fourth-order differential equations. A good qualitative agreement between the model dynamics and experimental data for the actual neurons is obtained. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1623–1635, December, 1998.     

Defects and drift of structures in parametrically excited capillary ripples

The onset of defects is experimentally studied in a system of capillary waves parametrically excited in a thin layer of liquid with different bottom topography. It is shown that the onset of defects occurs through the excitation of bounded wave-field regions corresponding to the areas with higher depths. The drift of defects and structures is associated with the near-bottom mass flow generated by rapidly decaying surface waves. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998) Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1537–1542, December, 1998.     

Detection of weak signals against the background of active noise fields scattered in an inhomogeneous medium. II. General case

In this paper, we study the specifically nonlinear functions of a detector, which are required for the non-Gaussian law of distribution of scattered noise. Antiaircraft Command High School, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 10, pp. 1314–1325, October 1998.     

On the use of dielectric gratings in compressors of electromagnetic radiation pulses

We present a theoretical study of dielectric diffraction gratings of high electric strength, which can be used in compressors of electromagnetic-field pulses. The theory is based on the numerical solution of the equations of an electromagnetic field using the integral-equation method. Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 747–757, June, 1998.     

Dynamics of complex-shape traveling pulses in a fitz hugh-nagumo system with modulated parameters

The dynamics of traveling-pulse solutions is studied for a Fitz Hugh-Nagumo model with modulated parameters. The boundaries of the modulation depth of the system parameters where these solutions still exist are found by numerical simulation. The compensation effect of the parameter modulation acting on the stability of such solutions is obtained. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, (998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1586–1592, December, 1998.     

Some results of measurement of atmospheric temperature and density using artificial periodic inhomogeneities of the ionospheric plasma

We present the preliminary results of measurement of atmospheric temperature and density at the E-region heights near Nizhny Novgorod in the 1990–1991 period (λ=56.15°N, ϕ=44.3°E). The monthly mean temperature and density are given in the height interval 100–110 km for September and October 1990. The temporal variations of temperature and density, associated with the propagation of acoustic-gravity and internal waves, are presented. The influence of natural turbulence on the measurement accuracy has been analyzed. The method is based on the generation of artificial periodic inhomogeneities (APIs) by a powerful radio wave and registration of the amplitudes of pulse probe radio waves backscattered by APIs. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 348–357, March, 1998.     

Investigation of wave motions in the lower ionosphere by the method of resonance scattering of radio waves from artificial periodic inhomogeneities

We present the results of studies of wave motions at lower-ionosphere altitudes by a new method based on measurements of the velocity of vertical motion of plasma by the variation of the phase of the signal that is backscattered from artificial periodic inhomogeneities of electron density (ionospheric arrays). The method allows us to study processes with different time scales and periods of from several dozens of seconds to some hours or longer. In the course of long-term 1990–1991 observations conducted near Nizhny Novgorod we determined some dynamic and spectral characteristics of internal gravity waves. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 3, pp. 308–321, March, 1997.     

Microwave radiometric sensing of the upper atmosphere above Nizhny Novgorod

We describe the equipment and methods of observation of variation of the state of some stratospheric and mesospheric gas components and present the results of measurements of the time and space ozone variations at altitudes of from 20 to 70 km above Nizhny Novgorod: the seasonal and diurnal variation and “ozone clouds.” The seasonal variation of ozone content at altitudes exceeding 22 km and the vertical distribution of ozone are compared with the measurement results obtained from the TOMS and CRISTA satellites. We also show the results of observations of mesospheric carbon monoxide. Institute of Applied Physics of the Russian Academy of Sciences. Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 11, pp. 1405–1423, November, 1998.     

Study of wind characteristics at heights of 200 to 800 meters using a decimeter sodar

The results of the experiment carried out in July–August 1997 using a two-position sodar are reported. Different types of intensity and spectrum variations of scattered acoustic signals have been obtained. The possibilities of using the sodar for the study of atmospheric turbulence and search of signals caused by “Fresnel” scattering from “plane” irregularities are discussed. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 7, pp. 841–848, July, 1998.