Vol 60, No 2 (2017)

Using MD computer simulations, the interaction of hydrogen impurity with the (100) and (111) twist boundaries in Ni and Pd is investigated. It is shown that twist boundaries can act as hydrogen traps, though less efficient compared to vacancies and edge dislocations. According to the data obtained, the energy of hydrogen bonding with the twist boundaries is not higher than 0.1 eV for both metals under study.

The physical processes occurring in the coal – natural gas system under the gas pressure release were studied experimentally. The possibility of gas hydrates presence in the inner space of natural coal was shown, which decomposition leads to an increase in the amount of gas passing into the free state. The decomposition of gas hydrates can be caused either by the seam temperature increase or the pressure decrease to lower than the gas hydrates equilibrium curve. The contribution of methane released during gas hydrates decomposition should be taken into account in the design of safe mining technologies for coal seams prone to gas dynamic phenomena.

The paper examines heat capacity of the polymer composite based on a large number of multiwall carbon nanotubes (95%/5%) in the temperature range of 300 K ≤ Т < 450 K in the course of heating and cooling. It identifies the anomalies of heat capacity and thermal diffusion that are responsible for structural phase transitions of the first order.

The paper deals with research carried out into plastic deformation of a heavy-wall pipe made of nanoparticle reinforced copper-based alloy. We present an original approach which combines methods of crystal plasticity and deformable solid mechanics, thereby allowing to study the stress-strain state of the heavy-wall pipe strengthened with incoherent nanoparticles using a homogeneous internal pressure. Dependences are constructed for the yielding area and the pressure, the limit of elasto-plastic resistance is obtained for the heavy-wall pipe and its deformation degree is described. It is shown that the particle size has an effect on strength properties of the material.

Parameters of high-temperature water vapor spectral lines presented in the well-known spectroscopic databases are discussed. As a reliability criterion for parameter values, recent experimental data on the transmittance measured with spectral resolution of 1 cm^–1 at Т ~ 1000 K are employed. As a result of our analysis, 156 spectral lines were revealed (12 of them were found previously) in the HITEMP2010 database the use of which in calculations of the transmittance leads to considerable deviations (≥20%) from the available experimental data. The line intensities determined by this method exceed by 3 times and more the data presented in other spectroscopic bases. Additionally, the line intensities from the HITEMP2010 database in the spectral range 10–6000 cm^–1 are completely compared with the result of semiempirical calculation at the high temperature available from the literature. The hot bands for which the relative deviation of the integral intensities exceeds 10% at T = 1302 K are identified. It is established that as a whole, the most reliable integral hot band intensities are contained in the HITEMP2010 database. This is confirmed by their least deviations from the measured transmittance at high temperatures. As a result, it is demonstrated that to obtain the best coincidence (Δ_av = 2.64%) with the measured data in the range 1000–2000 cm^–1 in calculation based on the HITEMP2010 database, the parameter values recommended in the present work for lines with overestimated intensities and different distribution of the temperature coefficients must be used.

The object of the present investigation is the ammonia molecule the knowledge of the properties of which is important for solving numerous problems of astrophysics, physics, and chemistry of atmospheres of Earth, planets of the solar system, and exoplanets, nondestructive testing, and many other problems of science and technology. The parameters of the ground vibrational state of the NH₂D and NHD₂ molecules are determined.

Possible quantum effects, induced by the torsion of spacetime described by its pseudotrace \( {\overset{\smile }{Q}}^i=\frac{1}{6}{\upvarepsilon}^{iklm}{Q}_{klm} \), and by a vortex gravitational field described by its angular velocity \( {\upomega}^i=\frac{1}{2}{\upvarepsilon}^{iklm}{e}_{ak}{e}_{lm}^a \) of rotation of the tetrad field \( {e}_a^k\left({x}^i\right) \), are considered. Toward this end, the vacuum averages \( <0\left|{T}_k^i\right|0> \) of the energy-momentum tensor \( {T}_k^i \) of the quantized scalar field are calculated. A thorough-going analogy between physical effects induced by these two physical objects is revealed both on the classical and on the quantum level.

A new expression for the scattering matrix in local quantum field theory is obtained on the basis of a generalized formulation of the microcausality condition. This expression is relativistically covariant, unitary, and causal and coincides with the generally accepted expression (the T-exponential) in the case when ultraviolet (UV) divergences are absent in the latter. Conditions are formulated, under the fulfillment of which the elements of the constructed matrix do not contain UV divergences. By way of an example, the probability amplitude of the particle–particle transition for a model with ℒ(x) = λ : φ³(x): in the second-order perturbation theory is found.

The application of four light pressure models, including the standard model, two empirical models with different degrees of complexity, and physical-empirical model taking into account the optical properties of the spacecraft (SC) surface for prediction of SC motion and determination of its orbits is analyzed. The accuracy of these models used to determine the orbits of the GLONASS satellite system and the stability of the model parameters are estimated.

In a temperature range of 9–200 K, temperature dependences of the differential resistance of space-charge region in the strong inversion mode are experimentally studied for MIS structures based on Cd_xHg_1–xTe (x = 0.22–0.40) grown by molecular-beam epitaxy. The effect of various parameters of structures: the working layer composition, the type of a substrate, the type of insulator coating, and the presence of a near-surface graded-gap layer on the value of the product of differential resistance by the area is studied. It is shown that the values of the product R_SCRA for MIS structures based on n-CdHgTe grown on a Si(013) substrate are smaller than those for structures based on the material grown on a GaAs(013) substrate. The values of the product R_SCRA for MIS structures based on p-CdHgTe grown on a Si(013) substrate are comparable with the value of the analogous parameter for MIS structures based on p-CdHgTe grown on a GaAs(013) substrate.

Birefringence and dichroizm of a porous aluminum oxide layer filled with titanium dioxide is calculated for the model of an effective medium. Oblique incidence of ordinary and extraordinary waves is considered. A dependence of the layer transmittance on the angle of electromagnetic wave incidence is compared with the available experimental data. The sensitivity of the experimental technique suggested previously to the change of the refractive index of the pore filler is investigated.

The one-dimensional Fokker–Planck–Kolmogorov equation with a special type of nonlocal quadratic nonlinearity is represented as a consistent system of differential equations, including a dynamical system describing the evolution of the moments of the unknown function. Lie symmetries are found for the consistent system using methods of classical group analysis. An example of an invariant-group solution obtained with an additional integral constraint imposed on the system is considered.

Results of numerical experiment on modeling of the atmospheric-pressure plasma formed during the spark-to-glow discharge transition in helium in low-current non-stationary plasmatron are presented. The numerical experiment is performed using the developed 2D physical and mathematical plasma model in the drift-diffusion approximation. Results of numerical calculation of the dynamics of discharge evolution are confirmed by the experimental data on the atmospheric-pressure plasma dynamics formed in the plasmatron during the spark-to-glow discharge transition. It is demonstrated that with preset initial conditions characteristic for spark breakdown, further discharge evolution leads to the formation of the near-cathode zone of the potential drop and the pulsed behavior of the electric current of the discharge. After the current pulse, the discharge transforms into the quasi-stationary mode with parameters characteristic for the glow discharge with monotonically increasing electric current and transverse dimensions of the plasma column.

Growth of SiSn compounds with a Sn content from 10 to 35% is studied. The morphology and surface structure of the SiSn layers are examined and the kinetic diagram of the morphological state of SiSn films is established in the temperature range of 150–450°C. During the growth of SiSn films from 150 to 300°C, oscillations of specular beam were observed. For the first time, periodic multilayer SiSn/Si structures with pseudomorphic monocrystalline SiSn layers with the Sn content from 10 to 25% are grown. The c(8×4) and (5×1) superstructures are identified during the growth of Si on the SiSn layer and the conditions are determined for the formation of the desired Si surface structure by controlling the growth temperature. From the diffraction reflection curves, the lattice parameter, the SiSn composition, and the period in the multilayer periodic structure are defined, which with high precision correspond to the specified values.

Using transmission electron microscopy, the structure of domain walls is investigated in Fe_0.2–Ni_0.8 alloy and nickel nanofilms. It is shown that it is controlled not only by the film thickness but also by the angle between the magnetization vector I_s and the easy magnetization axis. Applying an external magnetic field along the hard magnetization axis, the field values at which the domain wall structure varies are considered. As the domain wall density becomes higher, the field interval, where magnetization variations occur, is found to increase sharply.