The Interference Slow Wave in a Poroacoustic Biot Layer

It is shown that in a poroacoustic Biot layer placed inside an elastic medium, for any parameters of the model an interference slow wave exists. For low frequencies, the wave has very weak attenuation and the polarization of it coincides with the direction of the layer. This is evidence for the possibility of mapping subtle collectors inside an elastic medium in crosshole measurements. Bibliography: 7 titles.     

Duality transformations for general bi-isotropic (nonreciprocalchiral) media

The transformation is defined to leave a given bi-isotropic medium invariant, whence it is self-dual in this transformation. It is shown that duality transformations always exist in pairs, labeled as left-hand and right-hand transformations. Self-dual fields are seen to be generalizations of the wave fields E± applied in the analysis of reciprocal chiral media. It is demonstrated that plane wave propagation and reflection problems in bi-isotropic media can be solved easily in terms of self-dual field decompositions. Nonreciprocity is seen to give rise to effects like polarization rotation in reflection, which cannot be interpreted in terms of reciprocal chiral media     

Structural instability during rolling of tungsten in terms of nonlinear thermodynamics

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 47–55, March, 1991.     

Millimeter waves for short-range multimedia communication systems

A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes the propagation characteristics, the transmission techniques, and the multiple access protocols into account. The definition of service-oriented metrics is emphasized. Three different real scenarios operating at MMW are investigated with a unified perspective: intelligent transport systems, wide-band local-area networks, and local multipoint distribution systems for interactive video services. The role played by the MMW band in the development of these services is discussed. In each scenario, accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out in order to join suitable service-quality levels. The methodology considered is based on both analytical and semianalytical tools for performance evaluation     

Effect of high pressures on the mechanical and electrical properties of barium chalcogenides

In this work, on the basis of a semiempirical model of bonding forces that allows for three-particle interaction and uses the pseudopotential method, the mechanical and electrical properties of barium chalcogenides are studied at hydrostatic pressure. Equations of state are formulated from hydrostatic compression, parameters of the type B1–B2 structural phase transitions are calculated, the change in the energy band spectrum under the influence of the pressures is studied, and an estimate is made of the critical amount of compression that induces a dielectric-metal phase transition. The results obtained are in agreement with the available data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 44–52, November, 1991.     

Behavior of electron spin in an external axisymmetric electrostatic field

The self-orientation of the spin of an ultrarelativistic electron in an external axisymmetric focusing electrostatic field is investigated qualitatively. The conditions under which a collective phenomenon of this kind occurs and its nature are clarifiedTranslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–17, February, 1991.     

Two sources of excitation of photoluminescence of porous silicon

The change occurring in the photoluminescence spectra and the photoluminescence excitation spectra during aging of porous-silicon samples in air and in vacuum has been investigated. It was found that the character of the photoluminescence changes occurring during aging depends on the wavelength of the exciting light: In the case of excitation in the visible-range band of the luminescence excitation spectrum (λ_exc>490 nm) the photoluminescence decreases and in the case of excitation in the ultraviolet band it predominantly increases. It is shown that the two bands of the luminescence excitation spectrum (visible and ultraviolet) correspond to two different objects on the surface of the porous layer. Fiz. Tekh. Poluprovodn. 31, 908–911 (August 1997)