Within the framework of the Ginzburg - Landau theory, a study is conducted of the local equilibrium expressions for the free energy and Gibbs potential of a superconductor of the second kind (arbitrarily shaped) in an external field and carrying a transport current. It is shown how the London magnetic field $H_L$ and the intrinsic field $H_V$ of vortex filaments may be determined in this general case. Terms isolated from expressions for the thermodynamic potentials are proportional to the circulation sums $H_V$(in the case of free energy) or $H_V$ + + $2H_L$ (in the case of the Gibbs potential) along closed circuits that bound sections connecting the axial lines of the vortex filaments to the superconductor surface. If $H_V$,$H_L$≪$H_{c2}$, these terms yield the basic (dependent on the configuration of the vortex filaments) contribution to the thermodynamic potentials.
Show AbstractA loop diagram with a single "weak" and two "vector" vertices is computed within the framework of a proposed asymptotic treatment of the Green's electron function for a strong magnetic field. The process of two - photon production of neutrino pairs is studied, and their angular distribution and total production cross section are found. The contribution of this process to the neutrino luminosity of pulsars is estimated.
Show AbstractAn exact solution of the evolution problem for a boson packet in a " model " ideal infinitely extended crystal constructed of identical twolevel centers is obtained and studied: dissipative and temperature effects are ignored. A technique is proposed for the microscopic desrcription of the dynamics of the propagation of both long - wave as well as short - wave emission packets, as a result of which qualitative features of processes in the case of different ratios of the scale of microscopic inhomogeneities to the emission wavelength are identified.
Show AbstractПредлагается численный метод расчета функции распределения электронов по энергиям в однородных постоянном и высокочастотном полях, основанный на сведении уравнения для функции распределения к рекуррентной последовательности линейных краевых задач. Рассмотрена роль электрон-ионных столкновений, и показано, что неучет этого процесса при одновременном учете электрон-электронных столкновений приводит к грубым ошибкам в коэффициентах переноса. Иллюстрируется влияние различных предположений о виде интеграла неупругих столкновений на результаты расчета в постоянном и высокочастотном полях. Представлены результаты численного расчета в плазме Хе.
Show AbstractДается формулировка и обоснование специального регулярйзирующего алгоритма для решения обратных задач, связанных с моделированием процесса индукционной закалки стальных образцов. Приводятся результаты численного решения задач об определении плотности источников и закона теплообмена на поверхности образца, а также результаты моделирования процесса в целом, позволяющие выбрать оптимальный режим.
Show AbstractИсследованы спектры ИК-стимуляции BaS-фосфоров. На основании сравнения полученных экспериментальных данных с расчетами по эмпирическим формулам предполагается, что вся структура в спектрах ИК-стимуляции связана с электронными центрами окраски, образованными собственными дефектами BaS.
Show AbstractA piezoelectric hydroacoustic radiator consisting of a discrete periodic structure with assemblies whose inertial elements are piezoelectrically active and whose elastic elements are passive is considered. Formulas for the resonance frequencies of the radiator and the oscillation amplitudes of its radiating surface are analyzed. Optimal phase shifts between the voltages fed to the piezoelectric elements are found. Experimental results are presented for the case of a three-assembly structure that demonstrates that the above systems may be used as multifrequency radiators.
Show AbstractThe form of amatching transition is determined by the wave propagation equation for a rod of variable cross section and must correspond to a deep enough local minimum of the local (in a specified frequency band) mismatch factor. The fundamental system of solutions of this equation is used, so that it is possible to find the mismatch factor. Then, based on some initial approximation, the form of the transition is determined by means of the method of steepest descent. In the article, examples are considered which relate to the most interesting case of short transitions, to which a nonmonotone relation between the radius of the bar and the longitudinal coordinate corresponds.
Show AbstractThe ordering energy is computed by means of the pseudopotential method for Mg-In and Mg-Cd alloys. The computation results are compared to the ordering energy determined from diffuse scattering of X - rays. Over significant concentration intervals, the theoretical and experimental values of the ordering energy for the first coordination sphere are close in magnitude.
Show AbstractResonance absorption in $MnCl_2$ corresponding to the low-frequency branch of the antiferromagnetic resonance is studied. Measurements are performed at frequencies of 9.2 and 38 GHz in the temperature region 1.4- 4.2° K. The experimental data are compared to the conclusion of the theory of light-plane antiferro magnetics. Effects which tend to alter the size of the gap in the low-frequency branch are discussed.
Show AbstractA five-wave model of coherent Raman mixing is considered for the case in which a test wave with frequency $ω_t$ is scattered by vibrations of the medium $ω_o$ both in the stokes ($ω_t$ → $ω_ir$ = $ω_t$ - $ω_o$) and in the anti-Stokes ($ω_t$ → $ω_α$ = $ω_t$ + $ω_o$) region in the case of pumping of forced lattice vibrations($ω_p$ → $ω_sin$ = $ω_p$ - $ω_o$). The fifth wave ($ω_ir$ or $ω_o$) is important to take into account for media with relatively weak dispersion (for example, gases). An analytic and numerical study of the model is performed for experimental conditions with production of tuned infrared radiation in hydrogen. It is shown that the inclusion of a fifth wave ($ω_a$) radically alters the pattern of interaction due to strong energy pumping into this wave. An approximate solution of the coherent Raman mixing equations is obtained, making it possible to compute the frequency conversion efficiency as a function of the field frequencies, gas pressure, and pumping intensity.
Show AbstractAn electrostatic method of excitation and registration of torsional vibrations of mechanical cylindrically-shaped cavities made of sapphire is described. Calculated amplitudes of the excited vibrations and the transducer response are given. Torsional vibrations of a sapphire cavity with Q-factor 7.5-10$^7$ is achieved at room temperature.
Show AbstractThe structure of an irregularly broadened band at 1445 cm$^{-1}$ in cyclohexane is resolved by means of coherent Raman ellipsometry. The threshold capabilities of the method for the purpose of resolving superposed Raman lines are discussed.
Show AbstractThe article establishes an empirical relation between the thermal capacity of rock-forming minerals and their mean atomic weight M based on existing experimental data. The basic conclusions are as follows. 1. In a given class of minerals, the mean atomic thermal capacity is a constant, while the specific thermal capacity is proportional to the mean atomic weight. 2. The mean atomic thermal capacity decreases with increasing complication of the compound (increase in the number of atoms in the molecule), which, is equivalent to a decrease in $с_{р}$ with M remaining constant. 3. The specific thermal capacity of minerals that form rocks of the crust and upper mantle is a constant at 300°K and equal to 0.18 cal/g °K to within about 5%.
Show AbstractA device and technique which may be used to measure the group of thermal properties of substances as well as the heat of fusion in the temperature range 800-2000°K using samples shaped as massive cylinders with external heating in regular regimes of the second and third kinds is described. Formulas are obtained from a solution of the thermal problem and the inclusion of initial conditions which may be used to compute the thermal capacity, thermal conductivity, thermal diffusivity in the regular regime of the second kind by means of a single temperature transducer. Results from a trial of the device with samples of graphite, copper, and silver are presented.
Show AbstractThe influence of impurities in water on the development of association processes and the structure of the resulting associates of rhodamine 6G molecules is studied in the article. Depending on the quantitative content of water at low temperatures, it is possible for two types of associates to form, in which the molecules are combined either by means of water molecules or by dispersion interaction. It is shown that temperature shifting of the maxima of the long-wave color absorption bands at low water contents is attributable to the variation in the concentration of the water molecules, which have solvate shells of different compositions.
Show AbstractThe concentration dependence of the absorption spectra of ethanol solutions of rhodamine 6G at low temperatures is studied. It is established that under these conditions two types of associates may form. Associates with a general solvate shell typically manifest a new band in the absorption spectrum which appears as a consequence of a shift of the electronic levels of monomer molecules created by the field of nearby molecules. Associates consisting of molecules with individual solvate shells have lesser absorptivity than the monomer molecules. Molecules are joined into such associates as a consequence of dispersion interaction.
Show AbstractSpatially in homogeneous collective oscillations of domain boundaries are examined in a magnetostatic approximation for the case of a singlecrystal magnetic dielectric sample with plastic two - phase domain structure. It is proposed that the spatial period of the oscillations is somewhat greater than the domain width, and that the displacements of all the boundaries are related by means of the demagnetizing field. A dispersion relation is obtained for plane waves of the boundary displacements. The spectrum of inhomogeneous oscillations of boundaries analogous to the Walker modes in the saturation region is computed for the case of a spherical sample.
Show AbstractA steady - state Raman scattering theory is developed for conditions of simultaneous scattering of excitation in the forward and backward directions. The influence of the return Stokes component on the effectiveness of coherent Raman shifts is studied.
Show AbstractThe influence of heat treatment in a vacuum and in oxygen on the optical and electrical properties of amorphous crystalline films of Pb$_{0,8}$ Sn$_{0,2}$Te is investigated. The influence of oxide phases on crystallization and the variation in the stoichiometric composition of the films are found.
Show AbstractTemperature dependences of the capture of charge carriers photo- injected from a semiconductor onto electronic oxide traps in the Ge—GeO$_2$ system are studied. It is shown that transport of photo - injected charge carriers along localized tail states is performed by means of a skip mechanism.
Show AbstractThe angular and radial dependences of the acoustic pressure field for different values of the wave dimension $kr_0$ and attenuation in the material of a sphere are computed as a result of an exact solution using a BESM - 6 computer of a diffraction problem for a plane acoustic wave affected by a liquid sphere. Excitation of the natural vibrations of the sphere at definite values of $kr_0$ lead to a sharp variation of these dependences. At the n - th resonance, the angular dependence of scattering is determined by the dominant Legendre polynomial $P_n$, which leads to an increase in the number and amplitude of the secondary maxima, as well as to a significant increase in the maximum at θ = 0° (direction of mirror reflection). Attenuation in the material of the sphere leads to "stabilization" of the radial and angular pressure distributions, thereby converting the lens into a wide - band focusing system. The selection of material for this sphere with wave resistance ¯pc equal to the wave resistance of the surrounding liquid pc, does not eliminate the resonance nature of the focusing effect with $¯pc^{2}$ /$рс^{2}$ ≠ 1 (i.e., in the case of different compressibilities of the external and internal liquid).
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