Vol 42, No 9 (2016)

From analysis of time series obtained on the numerical solution of a plane problem on the motion of a body with an elliptic cross section under the action of gravity force in an incompressible viscous fluid, a system of ordinary differential equations approximately describing the dynamics of the body is reconstructed. To this end, coefficients responsible for the added mass, the force caused by the circulation of the velocity field, and the resisting force are found by the least square adjustment. The agreement between the finitedimensional description and the simulation on the basis of the Navier–Stokes equations is illustrated by images of attractors in regular and chaotic modes. The coefficients found make it possible to estimate the actual contribution of different effects to the dynamics of the body.

The results of experiments on initiating explosive transformations in layer samples of high-energy materials, which were first irradiated with beta particles, with a pulsed electron beam are reported. The potential to adjust the susceptibility of high-energy materials to an electron beam by performing preparatory ionization treatment is demonstrated.

The interaction of high-power pulsed microwave radiation with a plasma jet formed by a discharge in an ablative capillary is studied. A significant influence of microwave radiation on the plasma jet flow is found. Depending on the intensity of the initial perturbation of the jet, different scenarios of its evolution downstream are possible: attenuation or amplification accompanied with the development of turbulence up to the disruption of the flow if a certain threshold of the energy action is exceeded. A significant influence of the plasma jet and its state on the spatial position of the microwave energy release zone is found.

The dependence of elastic moduli for different directions on the nonstoichiometry with respect to carbon atoms in octahedral interstices of face-centered cubic crystalline lattice is established for the first time for metastable tungsten carbide (β-WC_1–x phase). It is shown that with decreasing content of carbon atoms in the tungsten carbide lattice it is compressed, which is accompanied by the growth of the contribution of metallic component, thus determining higher density of the coating material and change of elastic characteristics for different crystallographic directions. This makes it possible to obtain carbide coatings with the required ratio of elastic constants via corresponding technological regimes, which is especially important in formation of coatings with predominant crystallite growth orientation.

Using mass-resolved ion scattering spectrometry, spectra of Ne⁺ ions scattered at an angle of 120° from the surface of GaP in the energy range of 0.4–1.96 keV have been studied in detail. In the spectra, in addition to the peaks of elastic binary Ne⁺/P and Ne⁺/Ga collisions, the peak of sputtered neon ions has been found, as well as the wide peak (a “hump”), the energy of which slightly depends on the energy of primary ions and the intensity considerably increases with an increase in this energy. In our opinion, the main contribution to this peak is made by neon ions that undergo multiple collisions with gallium and phosphorus atoms on the surface and deeper layers of the sample and keep their charge due to reionization processes.

Penetration into boron carbide of an elongated high-speed projectile in the form of a copper jet produced by an explosion of a cumulative charge is studied. The efficiency of absorption of a copper jet in different brittle materials for evaluating their protective ability is compared. Conditions for the absence of the influence of the lateral unloading wave on the penetration zone, which provide the minimum penetration depth, are determined.

We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8–2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1–5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800–830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5–10.5 GPa at an elastic modulus of 400–550 GPa.

We consider the impingement of a gas jet on a liquid surface in a stable oscillatory regime, where by the jet-induced cavity shape in various phases of oscillations is periodically reproduced with high precision. This regime is observed during gas jet impingement at an angle of 30°–40° relative to the surface of a liquid with viscosity above 1 Pa s. A mechanism of the impingement of gas jet on liquid in the oscillatory regime is described that accounts for variation of the shape of the cavity on the liquid surface. It is established that oscillations exhibit a relaxation character. It is a specific feature of the oscillatory process that the gas stream flowing out from cavity separates from the surface of liquid. Stable oscillations in the “gas jet–liquid” system can be used for contactless measurement of the physical properties (in particular, viscosity) of liquids.

We have determined the curvature of a beam of coherent electromagnetic radiation and its angular and linear deviation in a rotating microsatellite representing a Luneburg lens in the optical segment of accuracy augmentation for new-generation global navigation satellite systems.

A new high-sensitivity X-ray diffraction technique for studying local surface deformations caused by crystal defects is described. The method is based on analysis of the shape of “bending interference fringes” (BIFs) in the Bragg geometry of X-ray diffraction. The obtained results show that the BIF method allows one to qualitatively assess very weak local deformations of a crystal surface with local bending radii of crystallographic planes from several dozen to several hundred meters.

We have studied the influence of PdO content in resistive Ag/Pd films (consisting of this oxide and Ag–Pd solid solution) on photocurrent dependent on the sign of circular polarization of the exciting radiation. The photocurrent was excited by nanosecond pulsed laser radiation with a 532 nm wavelength and measured in the direction perpendicular to the plane of laser beam incidence onto the film. The content of PdO in the film was varied by electrolytic reduction of Pd from PdO in sulfuric acid solution. Raman spectroscopy and X-ray diffraction measurements showed that reduced PdO content in the film leads to nonlinear decrease in the magnitude of photocurrent. It is established that photocurrent is also observed when PdO is fully absent on the film surface. The obtained results suggest that the nature of photocurrent in Ag/Pd films is related to the structure of Ag–Pd solid solution.

For asymmetric three-barrier resonance-tunneling structures with thin high barriers, the dependence of the integral transmission coefficient on the amplitude and frequency of strong high-frequency resonance fields during two-photon transitions has been studied in the approximation of an electron distribution function weakly varying at energies on the order of several widths of the quantum level. It is established that, despite the strong dependence of the shape and width of resonance levels on the microwave field amplitude, the general pattern of integral electron–photon interaction in strong fields changes but little in a broad range of variation of the level widths and field amplitudes.