Izvestiya of Saratov University.
ISSN 1817-3020 (Print)
ISSN 2542-193X (Online)

Научный отдел

Anishchenko-Astakhov self-sustained oscillator as one of the basic models of deterministic chaos

In the present review the conditions of appearing chaotic self sustained oscillations are formulated and a radio-technical scheme of a generator realizing these conditions is given. The equations of Anishchenko-Astakhov's generator are derived and analyzed. A special attention is paid to the interrelation between the generator's equations and Theodorchik and Van der Pole classical models.

Modelling the dynamics of photonic crystal broad-area surface emitting laser

The lasers beam dynamics in photonic crystal laser is investigated numerically. The decomposition of transverse field distribution in terms of orthogonal modes of photonic crystal structure is used. The relation between the transverse structure of output beam and struc ture of pump region is demonstrated. The modification of the trans verse distribution of the pump allows to control of excitation of se lected transverse mode families. 

Heterophase semiconductors underaction of irradiations

The history and current state of our heteropfiase photoconducting CdS-PbS films investigations are observed. Films were prepared by the vacuum evaporation method from the materials with limited mu tual solubility. Reasons of increased degradation stability with respect to radiation (in particular y- and electronic irradiations) are found out. Degradation stability is explained by diversion of recombination flow from wide-gap phase to narrow-gap. Radiation stimulated defects also move to narrow-gap phase.

Classical analysis of recombination of antihydrogen in a strong magnetic field

Basing on numerical simulation of classical trajectories, the influence of a strong magnetic field on the rate of the spontaneous radiative recombination of antihydrogen atoms in cold antiproton-positron plasma is theoretically studied under the conditions of the ATHENA and ATRAP experiments carried out in CERN. The effect of the mag netic field is estimated by Monte-Carlo calculation of the change in the cross section of the positron hitting the near-nucleus region with the radius typical for the atomic ground state.

Nonstationary excitation of open structures

The nonstationary theory of excitation for open resonators, waveguides and waveguide transformers has been developed. The open structures which are contained dielectric, magnetic and metallic bodies have been considered.

Optical biomedical diagnostics

This paper presents an overview on optical biomedical diagnostics. It discusses briefly the history of the problem. The main attention is paid to description of the modern methods of optical medical diagnostics based on spectrophotometry, fluorescence, Doppler spectroscopy, elastic, quasi-elastic and Raman scattering spectroscopies, as well as optothermal and optoacoustic effects.

Cluster synchronization destruction and chaos in an inhomoceneous active medium

We show that in an inhomogeneous self-sustained oscillatory medium the destruction of perfect clusters of partial synchronization, that is induced both by varying the control parameter and by noise, leads to the onset of chaotic behavior. We study the mechanisms of chaos formation in both cases. It is demonstrated that as parameters change, the transition to chaos in the deterministic medium can result from a hard (subcritical) period-doubling bifurcation and can be accompanied by intermittency.

Unary function of hard sphere distribution near ideal wall

Hard sphere system upon ideal wall was analyzed using equilibrium statistic physics methods. The integration equation for oneparticle distribution function of coordinate region is received. Resolve of obtaining equation we analyzed. Numerical results illustrating particles local relative density depending of distance to the wall are showed.  

Radiotechnical Methods for the Analysis of the Multifrequency Working Regimes of the Beam Devices with Longitudinal Interaction

The survey of the radiotechnical methods for the nonlinear amplifiers analysis is conducted. The presentation of the nonlinear amplifier as typical radiotechnical link, consisting of input and output filters and inertionless nonlinear amplifier, is proposed. The methods of the identification of the radiotechnical link elements are described. The problem of registration of amplitude-to-phase conversion is discussed. The possibility of the successful description of the multifrequency working regimes of the microwave amplifiers using the proposed model is demonstrated.

Vibronic spectra and structure of exited states of polyatomic molecules

The methods of determination of molecular model parameters in exited electronic states are considered. Structural-dynamic models polyatomic molecules are developed using a semi-empirical method of hybridized atomic orbitals. It is shown that the electronic-vibrational spectra make it possible to identify the tautomeric forms in different phases states, taking into account the intermolecular interaction.