Vol 61, No 11 (2016)

A high-frequency capacitive discharge is simulated in the geometry of a plasma accelerator with closed electron drift. It has been shown that, in such a discharge, as in a dc discharge, an azimuthal electron drift takes place and a potential drop is formed at the discharge channel exit, which leads to the emergence of an accelerated ion beam from the channel.

The effect of the crystallographic orientation of a single crystal hollow cylinder on features of creation and evolution of plastic deformation in it under conditions of high-speed axisymmetric load is studied. An advantage of the proposed loading scheme is the simultaneous implementation of all loading variants within the chosen crystallographic base plane of the cylinder and reaching different degrees of deformation over the cross section of the sample. Using the molecular-dynamic modeling, the difference in deformation properties of the loaded sample has been shown depending on the chosen crystallographic orientation of the base plane. Results of the investigation can be used to understand the main mechanisms of the plastic deformation of crystalline bodies.

The dependence of the Nusselt number on the Rayleigh number at the stage preceding the turbulent regime of convection is substantiated and obtained in analytic form. At this stage, the Nusselt number can be described by the power dependence on the Rayleigh number, which contains five constants. One of these constants is the same for all liquids and is the critical Rayleigh number Ra_cr = 1700 ± 51. The remaining four constants are strictly individual for each type of liquid. For liquid helium, the critical Rayleigh number Ra_cr = 35000 ± 4000 has the threshold value (Ra₁^mix)th = 37 085.75. This value is determined by the small ratio of the diameter of the vessel to its height, as well as the formation of a cylindrical convection cell at the bottom of the vessel with a mode number of 2 and a radial number determined by the fourth root of the firstorder Bessel function of the first kind.

We have considered the spatially homogeneous problem of the behavior of an ion admixture in a background gas after applying a harmonic electric field with arbitrary parameters for various laws of interaction of particles. The Boltzmann equation has been solved using the modified method of moments. The ion distribution function and its first moments have been analyzed. It has been shown that the universal analytic expressions for the current density and the ion energy that we derived earlier for a small field amplitude-tofrequency ratio have a considerably wider range of applications.

A method is described that allows one to study the conductivity dynamics of a channel produced by explosion of a wire at the stage of electrical breakdown. Experimental data have been presented for the expansion rate of the conductivity channel in extended (up to 1.9 m long) arbitrarily shaped gapes that were produced by an exploding copper wire 90 µm in diameter. The initial stored energy and applied voltage were, respectively, 2.7–3.7 kJ and 8–10 kV. It has been shown that the expansion rate of the conductivity channel coincides with the propagation rate of a shock wave and is inversely proportional to the square root of its radius and propagation time. The radius of the shock wave is a linear function of the square root of its propagation rate. Experimental data are in satisfactory agreement with the calculated results obtained by Lin [18] in terms of the model of an intense shock wave. It has been shown that the diameter of the conductivity channel depends on the position of the trailing edge of the shock wave.

Ni_48.8Fe_51.2 and Ni₇₀Co₃₀ alloys are subjected to cold rolling at a reduction of 98.8–99.0% and are annealed in a dc magnetic field of up to 29 T and without a field at various temperatures. The effect of a magnetic field on the structure and the crystal texture is studied. The application of a magnetic field is found to retard recovery processes and the early stages of recrystallization. At the stage of grain growth, the number of orientations with an easy magnetization direction increases and the grain size increases provided that the easy magnetization direction coincides with the main texture of the material. If the easy magnetization direction does not coincide with the texture, the grain growth in a field is decelerated and the texture sharpness decreases.

The elastocaloric effect (ECE) is experimentally studied in latex rubber subjected to the periodic action of a tensile force. The ECE is measured as a function of the relative elongation and the cycle frequency up to 4 Hz. Three cycle frequencies in which different thermodynamic processes, namely, elastocaloric cooling, self-heating, and a decrease in the ECE, occur are revealed. The maximum measured value of ECE in latex rubber reaches 14 K at a relative strain of 700% in the frequency range 0.1–0.3 Hz. The possibility of practical application of latex rubber for elastocaloric cooling is discussed.

Small-angle X-ray scattering is used to prove the formation of silver nanoparticles with sizes of 5–11 nm in siver/polyacrylonitrile nanocomposites synthesized via photopolymerization of a mixture containing silver, acrylonitrile, and photoinitiator. Optical spectra of nanocomposites obtained under different conditions are studied. The absorption spectra exhibit maxima at wavelengths of 420–450 nm related to the surface plasmon resonance of silver nanoparticles. IR spectra of the nanocomposites prove the formation of polyacrylonitrile in the course of the photopolymerization of monomer. The formation of metal nanoimpurities in polymer matrix leads to an increase in the intensity of photoluminescence and Raman scattering of polyacrylonitrile.

The temperature dependence of forward and reverse branches of the current–voltage characteristic of the semiconductor structure of a photoelectric converter with an n⁺–p-junction based on single-crystal silicon and an antireflective porous silicon film on the front surface has been studied. The presence of several current flow mechanisms has been revealed. It has been demonstrated that traps that emerge in the process of the formation of the porous silicon film have a considerable effect on the current flow processes in the semiconductor structure under consideration.

Multilayer systems consisting of layers of hybrid quantum dots are fabricated. The quantum dots with the CdSe/CdS core/shell structure are chemically synthesized and deposited on the surface of quartz glass that contains ion-synthesized silver nanoparticles in the near-surface region. Silver nanoparticles exhibit optical absorption owing to the localized surface plasmon resonance. Variations in the photoluminescence intensity of the layer related to an increase in the distance from the quartz surface with metal nanoparticles are studied. An increase in the photoluminescence intensity is observed under excitation in the spectral region of the plasmon absorption of silver nanoparticles. An optimal distance between the layers is determined to maximize the enhancement of the photoluminescence of quantum dots in the presence of the near field of metal nanoparticles.

We consider an effective method for increasing the total efficiency of relativistic Cherenkov generators, viz., recuperation. It has been found that, for a generator with an efficiency smaller than 15%, recuperation makes it possible to obtain an increase in the efficiency that exceeds 50% (from 12% to 68%). In generators with initially high efficiency (more than 50%), recuperation may turn out to be ineffective.

The method of the envelope equation has been developed to describe the stability of the motion of ions in a quadrupole mass filter in the presence of periodic excitations of the feeding voltage. Dynamic equations that describe the variations in the envelope of ion vibrations in the vicinity of the vertex of the first common stability region have been obtained and reduced to the form of the Mathieu equations. The splitting of the stability diagram of the motion of ions into stability islands due to excitation has been described. The results of the approximate theory have been confirmed by an exact analysis of the stability diagram for rational values of the relative excitation frequency. The boundaries of the applicability domain for the developed theory limited by first-order resonances have been determined.

The growth of graphene and graphite films on nickel surface under conditions for ultrahigh-vacuum carburization and subsequent annealing is studied at film thicknesses ranging from a single layer to ≈1000 layers. The cooling of nickel carburized at a temperature of 900–1500 K leads to the growth of graphene and thin graphite films the thickness of which depends on the carburization temperature and the growth temperature of the films. Dissolution of nickel with graphite film in diluted sulfuric acid makes it possible to separate the film from the sample. The graphite film thickness amounts to ˜0.4 µm at carburization and growth temperatures of 1500 and 1100 K, respectively.

We analyze the estimate of the drag coefficient error obtained in aeroballistic experiment. Technical solutions, schemes, and devices for increasing the informative character of the experiment and reducing the error in the drag coefficient determination are proposed.

A significant increase in the binding energy of the singlet ground state of biexciton (of spatially separated electrons and holes) in a nanosystem that consists of CdS quantum dots grown in a borosilicate glass matrix has been predicted; the effect is almost two orders of magnitude larger than the binding energy of biexciton in a sulfide cadmium single crystal.

Effect of laser annealing on electrical and optical properties of zinc oxide films is analyzed. The films are fabricated using the plasma-chemical deposition under low pressure. ZnO amorphization under modifying irradiation is demonstrated.

A new method is implemented in order to measure the concentration of CO₂ and inhalation anesthetic sevoflurane eliminated through the skin during surgery. The concentration of inhalation anesthetic has been measured during general combined anesthesia (sevoflurane, fentanyl) and total intravenous anesthesia (propofol, fentanyl). The dependence of the concentration of CO₂ and the inhalation anesthetic from the relaxation of smooth muscles in the walls of blood vessels under the effect of sevoflurane and propofol and on the stress response to surgical injury has been revealed for the first time.

Discharge with a liquid nonmetallic cathode (tap water) in atmospheric-pressure air flow has been experimentally studied. This discharge is a modification of the previously investigated discharge with liquid nonmetallic electrodes. The design of the discharge unit has been described and some investigation results have been presented.