Vol 61, No 4 (2018)

Comparative results of modeling of the phenomenon of a high-voltage discharge in nitrogen at atmospheric pressure based on two theoretical approaches: hydrodynamic and kinetic descriptions of electrons in discharge plasma are presented. The detailed spatiotemporal pattern of the development of coaxial gas-filled diode breakdown with formation of runaway electrons in it is described. It is demonstrated that the switching characteristics of the subnanosecond discharge are reliably modeled within the limits of both hydrodynamic and kinetic descriptions of electron components, whereas the parameters of runaway electrons can reliably be calculated only using the kinetic description.

An overview of our original studies and the results reported in the literature on the investigation of variations in structure, phase composition, mechanical and other properties of metallic materials under external impacts is made, including their high-pressure processing by large (severe) plastic and megaplastic deformation, explosion loading, and irradiation with ultra-short laser pulses.

With the help of an applied software package written by the authors, we have averaged the effective total barotropic coefficient κ = (–λ + p)/(λ + ε) of the classical scalar field and the cosmological term and have shown that during cosmological evolution for sufficiently large values of the cosmological constant the Universe transitions from the inflationary stage to a nonrelativistic stage, and then, after a plateau, it transitions to a later inflationary stage.

Possible realistic means of formation of wormholes are considered and investigated. As a realization of such, it is proposed to apply self-gravitating physical fields having a vortex character. In the present paper, we consider using a stationary vortex electric field. We show that within the framework of Einstein’s theory of gravitation, a self-gravitating vortex electric field can induce the formation of wormholes. We also show that the combined use of a vortex electric field and a vortex magnetic field improves the traversability of the obtained wormholes since their throat radii are significantly increased.

A result of calculation of the topological properties of the Universe and its large-scale substances is presented. An equation for calculating values of the Hubble constant of the substances of the Universe, and of the Universe and the Galaxy, Sun, and Earth has been obtained for the first time. Their age and the time of one full cycle and of five cycles of expansion and compression of the Universe are calculated. A new hypothesis about the formation of the relic background of the Universe is proposed. The infinity of its evolution in time is proven.

A method for improving asteroid orbits by gradual replacement of observations with their simulated values is considered. The method consists in successive rejection from processing of observations with maximal residuals and replacement of these observations with their values calculated in the last iteration of the process of orbit improvement. In addition, the traditional method of gradual rejection of observations with maximal residuals that does not preserve any information on these observations is considered. The accuracies of the methods are compared for a number of improvements of orbits of asteroids Nos. 115489 and 179699 from observations of their separate oppositions and pairs of oppositions. It is demonstrated that the method of replacement of observations with simulated values yields as a whole more exact results in comparison with the traditional methods of observation rejection.

The paper studies the loss of stability of high-temperature, homogenous plastic deformation of alloys with L1₂ structure during the super-localization process. Using methods of mathematical simulation, a joint effect of geometric and physical factors on the stability loss of plastic deformation is analyzed under the tensile and compressive stresses. The properties of elements of the deformable medium are detected, at which the macroscale loss of stability is observed in relation to homogenous plastic deformation. It is found that super-localized plastic compressive deformation occurs when physical softening is ahead of the geometric strengthening. Under the tensile stress, the loss of stability of homogenous plastic deformation always occurs due to necking because the geometric softening begins before physical.

The paper examines a technique for producing metal-cutting ceramics from the plasmadynamic synthesis product using the spark plasma sintering technology. It studies the dependence of physico-mechanical properties of ceramics on the mixture parameters. Increase in bulk density and effect produced by this increase are well observed when comparing the sintering process curves. Movable die displacement for non-activated powder is 3.5 mm, while powder activation allowed reaching the 1.75 mm displacement, other conditions being equal. Hardness of produced materials measured by Vickers method was 21 GPa for non-activated powder and 17 GPa for activated powder at relative densities of sintered ceramic workpieces in relation to osbornite monocrystal of 92% and 93.5% respectively. Significant increase in density of the sintered body is ensured mainly by elimination of the raw material agglomeration.

The problems of the behavior of superconducting infinite plane-parallel plate and cylinder in an external magnetic field are solved in the approximation of the model of surface currents. The latter, in contrast to the conventional notation, enter as the currents of superconducting electrons into the boundary conditions for the magnetic induction. Surface currents are understood as the volumetric current flowing in the thickness of the near-surface layer, which is associated with the thickness of the London penetration depth of the field and currents into the thickness of the superconductor. It is shown that in this case, a jump in the magnetic quantities occurs at this thickness. The calculated average magnetization of the magnet is reduced to the strength of the external field. The proportionality coefficient, which is reasonable to call the mean magnetic susceptibility, turns out to be not exactly equal to –1, but has a slightly less value, because the field does not weaken immediately. The possibilities of experimental verification of the obtained effect are discussed.

High-resolution infrared spectrum of the ³⁴SO₂ molecule is recorded with a Bruker IFS-120 HR Fourier spectrometer. More than 3000 transitions (with J^max = 60 and \( {K}_a^{\mathrm{max}} \) = 19) are assigned as a result of analysis. The Watson Hamiltonian is used as a theoretical model. The experimental intensities of 700 single rovibrational lines of the υ₂ band are analyzed.

A relationship is established between singular solutions of the Clairaut equation in the theory of ordinary differential equations and singular solutions of the Clairaut equation in the theory of partial differential equations. It is shown that exact relationships exist between Legendre transformations in classical mechanics and Clairaut equations.

The problem of Mandelstam–Brillouin scattering in the region bounded in the direction of pump wave propagation and infinite in the transverse direction is considered. Such situations can arise, for example, in plasma heating or diagnostic problems. Since the time of scattered radiation escape for the examined geometry upon scattering at a certain angle increases substantially, this effect compensates for a decrease in the nonlinear feedback coefficient upon oblique scattering and leads to instability development. Since the convective losses at scattering angles close to π/2 are small, collisional absorption of waves plays an important role in this case. The instability increments are calculated taking into account not only the convective losses, but also the collisional wave attenuation.

Using the methods of electron diffraction microscopy and X-ray diffraction analysis, the influence of alloying of the austenitic steel, Grade 110H13, with chromium and vanadium, as well as high-melting, ultrafine-grained TiO₂, ZrO₂ powders and Na₃AlF₆ cryolite on its structural-phase state and microstructure is investigated. It is shown that the matrix of non-modified steel is completely austenitic and consists of an iron-based solid solution and the interstitial (C, N, O and other) and substitutional (Cr, V and other) atoms simultaneously. Alloying with chromium and vanadium changes neither its phase composition nor defect structure, while alloy modification results in qualitatively new structural features: γ → ε-transformation, high-intensity microtwinning, defect structure changes, and a sharp increase in the scalar dislocation density. The features of the deformation-induced microtwinning and ε-martensite plates identified in the modified steel promote revealing additional microtwin systems in the matrix γ-phase, which result in structural changes making it possible to classify it as a γ′-phase. It is found out that an introduction of modifying additions gives rise to the following sequence of structural-phase transformations: γ→γ′→(γ′ +ε). The experimental data obtained demonstrate that as a result of modification the crystal lattice transits into a low-stability state. This transition is accompanied by marked structural-phase changes consisting in the formation of several microtwin systems and γ → ε-transformation. These structural-phase changes in the modified steel are due to the crystal-lattice transition into the low-stability state, followed by new structural-phase alterations.

Using quasiclassical kinetic theory, nonlinear phenomena under the formation of space-charge polarization in crystals with hydrogen bonds (HBC) are investigated. From the solution of the nonlinear system of Fokker-Planck and Poisson equations with blocking electrodes, it is established that for the mathematical description of the relaxation polarization in HBCs in weak fields (100-1000 kV/m) and at high temperatures (T> 350 K), it is sufficient to use a linear approximation of perturbation theory. Theoretically, it was found that at the first odd frequency of the alternating field, nonlinear effects caused by the interaction of relaxation modes of various frequency orders start to appear. The diffusion and mobility coefficients are calculated taking into account both mechanisms of the protons transitions (thermally activated and tunneling transitions) through a parabolic potential barrier. A recurrence expression is constructed for calculating complex amplitudes of relaxation modes generated at an arbitrary frequency (multiple to the fundamental frequency) of the alternating field in an arbitrary approximation of perturbation theory. The proposed scheme for solving the kinetic equation can be applied to other crystals with ionic conductivity similar to HBCs in the type and properties of the crystal lattice.

The absorption coefficient of the rovibrational 2υ₂–υ₂ band of the ³⁴SO₂ molecule localized in the region 350–850 cm^–1 is studied for the first time. An analysis of the above-mentioned band allows positions of the rovibrational lines and quantitative values of the absorption coefficients to be determined.