Heat of formation of solid solution of alkali halides

Based on a semicontinuum model, the electrostatic, the polarisation, and the repulsive energy change of a lattice is calculated numerically, as a function of the relaxation of the nearest neighbouring ions of a substitutional impurity in an alkali halide crystal. It is found that for a particular displacement, the total energy change of the lattice is a minimum. Thus the heat of formation of a dilute solid solution is obtained. Here, we report calculations on the heat of formation of the following systems-Na⁺ in LiCl, Li⁺ in NaCl, K⁺ in NaCl, Na⁺ in KCl, Rb⁺ in NaCl, Na⁺ in RbCl, F^? in NaCl, Cl^? in NaF. Br^? in NaCl and Cl^? in NaBr.     

Approximate diagonalization of the energy operator of a system of interacting particles

The present work considers a method of diagonalization of the energy operator of a system of valence electrons in a simple model of a semiconductor, and in a simple model of a metal. The results obtained are used in the theory of superconductivity and in the theory of superfluidity.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 43–47, December, 1971.     

Effects of noise on detection of amplitude increments of sinusoidal vibration of the skin.

Vibrotactile thresholds for detecting a 300-Hz signal in the presence of both a 300-Hz sinusoidal pedestal and a background noise were measured as a function of the amplitudes of the pedestal and noise. Threshold increased monotonically as a function of the amplitude of the noise, but was a nonmonotonic function of the amplitude of the sinusoidal pedestal. Negative masking, in which the pedestal facilitated detection of the test stimulus, was observed in the absence of background noise and in the presence of subthreshold background noise when the pedestal was near or below threshold. Negative masking disappeared when the experiment was conducted in the presence of moderately intense to intense background noise. The results are consistent with a peripheral high-energy threshold for taction.     

Formation of a crystallographically oriented colony of products of eutectoid decomposition in the process of plastic deformation of steel by drawing

Methods of transmission electron microscopy and EBSD analysis have been used to study the evolution of the structural state of a eutectoid steel in the process of plastic deformation by drawing. It has been established that the reason for steel embrittlement is in the formation in the former grains of the high-temperature phase of a specific element of the structure, namely, a crystallographically oriented colony of products of eutectoid decomposition, including a conglomerate of morphological colonies with a common orientation along the cleavage plane of one of the constituents of the eutectoid. The process of its formation means multiple changes in the scale of the structure and, therefore, increase in the temperature threshold of the material brittleness.     

CSR切割磁铁设计

兰州重离子加速器冷却储存环(HIRFL CSR)由一个主环(CSRm)和实验环(CSRe)构成.两个储存环的束流注入与引出都需要借助于切割磁铁的导向来完成.介绍了CSR的切割磁铁的物理设计和二维场计算. In order to satisfy the requirement of beam injection and extraction of CSR, four magnetic septums will be used in the accelerator. In the design, the shape of the lamination is optimized by 2-D magnetic field calculation. Also, in order to decrease the leakage field and obtain a satisfied field distribution, a special auxiliary coil and a shield iron plate are considered and as well as the construction of the septum leg is treated in a special way. As a result, the leakage field is almost...     

Analysis of optical signals of the pico-and femtosecond ranges and of the character of action of a probed medium on the radiation

The solution of the phase problem in optics as applied to the analysis of time-dependent signals and the character of action of a medium under study on the probing radiation is considered using a two-beam interferometer with phase modulation in one of the channels and a spectral device. The analysis relates, in particular, to ultrashort signals and processes. To ensure a frequency shift in the interferometer channel, an electro-optic crystal of the type of ferroelectric perovskites was used as a modulator. The analysis of errors for the amplitude and phase structures determined is performed.     

Model of stochastization of the oscillatory regime of superradiance

Based on the analysis of the experimental data on the observation of the fluorescence and superradiance of praseodymium ions in a matrix of lanthanum trifluoride, a model of superradiance of three-level radiators with two close upper levels is developed in the mean-field approximation and studied. The uppermost level is coherently pumped by an ultrashort pulse of electromagnetic field, after which the excitation is transferred to the close energy level, from which the superradiance transition occurs to the lower level. In limiting cases, the considered model is reduced to the known models of superradiance and describes the ordinary regimes of monopulse and multipulse (oscillatory) superradiance. However, in a certain region of parameters, the model under discussion describes such a multipulse superradiance signal in which electromagnetic field spikes composing it follow in time with random intervals and amplitudes, so that the regime of regular chaotic dynamics is demonstrated in a single superradiance signal. In a certain time interval, the proposed model can be described by the Lorenz equations with the parameters corresponding to the chaotic dynamics of spikes composing the superradiance signal. The presented results of the numerical simulation of the model equations qualitatively correspond to the picture of stochastic pulsations observed experimentally.     

Qualitative analysis of the formation of T-domains under the condition of the existence of a single R-reference system

We examine the origination of a T-domain in a spherically symmetric configuration. The following assertion is proved: If a single R-reference system can be introduced in the whole connected R-domain, where each remote observer can determine an arbitrarily large interval of coordinate R-time, then the boundary between the R-and T-domains (the R-T boundary) is formed by isotropic world lines. Certain characteristic features of the solution describing the origination of a T-domain can hence be mentioned, namely: There are throats in the T-domain; in the R-neighborhood of a definite part of the R-T boundary the reference system applicable in the whole space-time domain under consideration is broadened; the R-T boundary is a surface on which the time R-coordinate takes on an infinitely large value in the limit.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 15–18, May, 1981.     

Measurement of the parameters of the natural waveguide mode

The possibilities of using the decomposition of natural waveguide modes in a shallow-water sea in case there is a sound velocity gradient into sinusoidal modes of an ideal waveguide is grounded. The applicability range of such decomposition is shown. Dispersion in signals of the modes presented in such a way is determined by mathematical reversal without a test source. The structure of discrete modes in a natural waveguide is determined without utilizing the bottom parameters and sound velocity’s distribution over the waveguide depth. The coefficient of the mode signal’s correlation with the measured parameters of the mode signal and a real signal, introduced into it, is shown to be 0.973. The signals from a point emitter positioned at the depth of 50 m in the frequency range of 90–280 Hz in a shallow-water sea (the Barents Sea, a 120 m depth, a 7 km distance), received by a vertical antenna array comprising 32 receivers spaced equidistantly with a 3-m step are used in the experiment. A real signal has been successfully reversed using a mathematical model.     

Optimization of focusing of linearly polarized light

We show that, by adding a π-phase shift to one-half of a linearly polarized beam, the roles of the transversal and longitudinal field components of the focused beam are interchanged, resulting in better focusing of the longitudinal component in the direction perpendicular to the phase jump line. For this component the scheme produces a spot with FWHM >15% smaller than a spot generated with either linearly or radially polarized light for any NA. The scheme has a similar advantage when applied to circularly polarized light, and it holds for both a plane wave and a realistic case of a Gaussian incident beam. This technique may find applications when using recording media responsive to the longitudinal field only, particularly in read/write for optical storage where the resolution in one transverse dimension is most important.     

Computer simulation of arising of diploid genomes

The haploid–diploid cycle where, under unfavorable conditions the population becomes diploid, is modeled by a Monte-Carlo method in the framework of the Jan–Stauffer–Moseley hypothesis. Diploidy and sex may have first arisen as a way to escape death, when a simple unicellular individual is threatened by too many deleterious mutations. Using a bit string model, we find that in a system where competition is present (through the Verhulst factor), diploids dominate. In this case the transition from haploid to essentially diploid population takes place in a short time interval reminiscent of phase transitions in physical systems.     

Formation of a sequence of ultrashort signals in a collision of pulses consisting of a small number of oscillations of the light field in nonlinear optical media

Collisions of pulses consisting of a small number of oscillations and propagating in a nonlinear optical medium unidirectionally but with different group velocities because of a difference in the spectral composition are considered. It is shown that, at intensities of radiation ensuring the superbroadening of its spectrum, the interaction of two pulses can result in the formation of a quasi-discrete spectral supercontinuum whose temporal structure is described by a sequence of ultrashort signals with a nearly rectangular shape.     

Gravitational interaction of a vector field with account of the nonmetricity of space-time

The gravitational interaction of a vector field is investigated in a space with the nonmetricity described by the Weyl vector. The analogue of the Coulomb law for the electrostatic field of a point charge is found in such a space. It is shown that taking account of the nonmetricity of space-time leads to the appearance of a nonlinearity in a massive vector field, resulting in the sine-Gordon and shine-Gordon equations. The screening of the vector-field mass as a consequence of its interaction with the nonmetricity is clarified. The solution for the Reissner-Nordström problem in a Weyl space is obtained, which asymptotically coincides with the solution of the same problem in general relativity, but nowhere does it possess singularities apart from at the origin. The obtained results show that it is reasonable to take account of the nonmetricity when describing the gravitational interaction of a vector field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 50–54, August, 1984.     

One method of describing the transfer of energy of the kinetic degrees of freedom to the electronic states of molecules

An analysis is made of the process of transferring the kinetic energy of highly excited vibrational terms of a molecule to an electronic state of one of its constituent atoms. This is done by utilizing a wave equation for the effective wave functions of the atom, corresponding to mixed states, in which the velocity of this atom relative to the neighboring atoms in the molecule enters as a parameter. An expression is found for the excitation probability in the case of a hydroge-like atom in the resonant approximation. State University, Omsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 20–26, September, 1996.     

Influence of the opening angle of a conical supersonic nozzle on the structure of initial interval of non-isobaric jet

The ideal gas exhaustion from an infinite volume into a gas at rest through a supersonic conical Laval nozzle is considered. The problem was solved numerically by steadying in time in a unified formulation for the regions inside the nozzle and in the ambient environment. In such a statement, the nozzle outlet section is no internal boundary of the region under consideration, and there is no need of specifying the boundary conditions here. Local subsonic zones arising in the flow lie inside the region under consideration, which eliminates the possibility of using a marching technique along one of the coordinates. The numerical solution is constructed by a unified algorithm for the entire flow region, which gives a possibility of obtaining a higher accuracy. The computations are carried out in the jet initial interval, where, according to monograph [1], the wave phenomena predominate over the viscous effects. The exhaustion process is described by the system of gas dynamics equations. Their solution is constructed with the aid of a finite difference Harten’s TVD (Total Variation Diminishing) scheme [2], which has the second approximation order in space. The second approximation order in time is achieved with the aid of a five-stage Runge-Kutta method. The solution algorithm has been parallelized in space and implemented on the multi-processor computer systems of the ITAM SB RAS and the MVS-128 of the Siberian Supercomputer Center of SB RAS. The influence of the semi-apex angle of the nozzle supersonic part and the pressure jump between the nozzle outlet section and the ambient environment on the flow in the initial interval of a non-isobaric jet is investigated in the work. A comparison with experimental data is presented. The computations are carried out for the semi-apex angles of the nozzle supersonic part from 0 (parallel flow) to 20 degrees. For all considered nozzles, the Mach number in the nozzle outlet section, which was computed from the one-dimensional theory, equaled three. Computations showed that in the case of flow acceleration in a conical supersonic nozzle, its geometry is one of the main factors determining the formation of the jet initial interval in ambient environment.