Numerical simulation of the translational nonequilibrium zone behind a shock-wave front

The translational nonequilibrium zone in a shock wave is considered for a gas consisting of light particles and a small addition of heavy particles. The gas is taken to be two-dimensional, and long-range forces are assumed to be absent. In the framework of this approximation, a program for molecular dynamics simulation of the gas is developed. It is applied to calculate a particle distribution function in the shock wave, to analyze the time evolution of the distribution function, and to study its dependence on the gas composition.     

Modulation of the phase difference between polarization modes in single-mode fibers

Mechanisms of polarization modulation in a single-mode fiber that modulate the phase difference between polarization modes without affecting their amplitudes are considered. A coefficient that characterizes the efficiency of cylindrical piezoceramic modulators and is independent of their resonant properties is introduced. Analytical expressions for this coefficient for different modulation mechanisms are derived. The lateral pressure on the fiber is shown to provide the highest efficiency. For isotropic fibers, a modulator with a squeezing covering, which increases significantly its efficiency, is studied. For anisotropic fibers, the most appropriate way of phase difference modulation is longitudinal extension, in which case the birefringence axes do not have to be matched. In most cases, the measured and predicted efficiencies are in good correspondence.     

Stimulated raman scattering in fiber-optic communication lines

Stimulated Raman scattering (SRS) in a long-distance fiber-optic communication line with wavelength-division multiplexing (WDM) is studied theoretically at a high power of the signal transmitted. A new criterion for determining the SRS threshold is used to calculate the critical input power versus the number of optical channels and frequency separation between them. The theoretical model is verified experimentally. SRS interaction between two channels in a communication line with an SRS amplifier for which the optical waveguide of the line serves as a nonlinear medium is measured.     

Relict Neutralinos in the Hot Universe

Russian Physics Journal -     

On the Efficiency of Nonchain Electric-Discharge HF (DF) Lasers

Russian Physics Journal -     

Magnetic Properties of Iron-Based Amorphous Metal Wires

It has been studied how the conditions of machining and the elastic tensile stresses affect the magnetic properties of amorphous metal wires of composition Fe₇₅Si₁₀B₁₅ produced by drawing from a melt. The magnetic characteristics of wires subjected to both thermal treatment and treatment with a continuous electric current of different magnitude have been investigated. The residual induction of wires is their magnetic parameter most sensitive to the conditions of treatment. The dependences of the residual induction on temperature and on the magnitude of the treating electric current are qualitatively similar. The greatest changes in residual induction are observed in the range of treating electric currents from 0.5 to 0.8 A, which can be associated with the processes of structural relaxation and crystallization occurring in the wires. The run of the dependence of the residual induction on the magnitude of tensile stresses is nonmonotonic in character and is determined by the level of internal hardening stresses of the test wires.     

Addition to the Solution of the Problem on the Motion of a Free Nonrelativistic Electron in a Magnetic Field

In addition to the solution of the quantum mechanical problem on the motion of a free electron in a magnetic field, given by L. D. Landau in his pioneering work, this quantum mechanical problem is solved in view of the fact that the sum of the components of the free kinetic energy of an electron along two axes is a periodic quantity varying identically within the boundaries of every Landau energy level. This periodicity is a consequence of the quantized motion of an electron in a plane normal to the direction of the external magnetic field.     

Calculation of the Characteristics of an Infinite Linear Queue for a Doubly Stochastic Incoming Stream

In the present paper, the mathematical expectation and variance of the number of queries in an infinite linear queue are calculated for the Poisson synchronous doubly stochastic stream of incoming queries with two intensity states.     

Measurements of Time-Varying Characteristics of Optical Signals and Inhomogeneities of Tested Substances with Additional Phase Modulation

The problem of investigation of the amplitude and phase structure of a time-varying probing optical signal and the structure of time-varying inhomogeneities of a substance tested by this signal is considered. The analysis is concerned, in particular, with determination of the structure of signals and processes with resolution in the pico- and femtosecond range. The scheme used for the analysis is based on registration of four spatially separated spectra of the studied radiation. The spectra are formed in a four-channel scheme with a twin-wave Michelson interferometer and a spectral device. Modulators based on electrooptical crystals (perovskites) are placed in the channels. The sum spectra are formed: without modulators, with the effect of either of the modulators, and with both of them affecting the radiation. The effect of the studied substance implies either modulating the radiation (in this case it is described by multiplication) or redistributing the radiation (then it is described by convolution).