Vol 61, No 5 (2016)

We propose a system of concealed information transfer based on a delayed feedback oscillator with switchable chaotic regimes. The proposed system is analyzed numerically and experimentally. The dependences of the bit error rate during transmission of a binary information signal on the signal-to-noise ratio, attenuation of the signal in the communication channel, and the duration of the time interval during which a bit is transferred are constructed. The high stability of the system to noise and amplitude distortions of a signal in the communication channel is demonstrated.

The effect of the initial pressure of multicomponent bubble media on the conditions of initiation, the structure, the velocity, and the pressure of detonation waves is experimentally studied. The variation of the initial pressure of a bubble medium is found to be an effective method to control the parameters of bubble detonation waves.

The transition of a low-current discharge with a self-heated hollow cathode to a high-current discharge is studied, and stability conditions for the latter in the pulsed–periodic mode with a current of 0.1–1.0 kA, pulse width of 0.1–1.0 ms, and a pulse repetition rate of 0.1–1.0 kHz are determined. The thermal conditions of the hollow cathode are analyzed, and the conclusion is drawn that the emission current high density is due to pulsed self-heating of the cathode’s surface layer. Conditions for stable emission from a plasma cathode with a grid acting as a plasma boundary using such a discharge are found at low accelerating voltage (100–200 eV) and a gas pressure of 0.1–0.4 Pa. The density of the ion current from a plasma generated by a pulsed beam with a current of 100 A is found to reach 0.1 A/cm². Probe diagnostics data for the emitting and beam plasmas in the electron source are presented, and a mechanism behind the instability of electron emission from the plasma is suggested on their basis.

We report on the results of investigation of a plasma switch with complete grid control in a discharge with a cathode spot on the liquid-metal cesium cathode without grid diaphragming. The retention of the working area of the grid relative to the anode area leads to an order-of-magnitude increase in the switching anode current (up to 20 A/cm² over the anode area) and a substantial (up to 100 V and higher) increase in the switching voltages. The use of the cathode jet makes it possible to reduce the working pressures of cesium vapor (down to 10^–3 Torr). We discuss the results of analysis of peculiarities of grid discharge quenching in such a switch, which make it possible to determine possible reasons for limitation of the working parameters of the switch and the ways of their further increase.

The radiation resistance of nanostructured TiN, TiAlN, and TiAlYN coatings is studied after 500-keV He⁺ ion irradiation in the fluence range 5 × 10¹⁶–3 × 10¹⁷ ions/cm². The radiation-induced changes in the phase composition, the structure, the lattice parameters, the morphology, and the mechanical properties of coatings are investigated. Blistering is found to be absent, and the radiation fluence is shown to affect the strength properties of the thin coatings nonlinearly. A significant decrease in the grain sizes is detected upon ion irradiation, which causes an increase in the microhardness and the radiation resistance of the coatings. The TiN, TiAlN, and TiAlYN coatings are found to be radiation-resistant coatings, which do not undergo serious degradation during high-fluence ion irradiation.

The effect of holes on the band formation and the serrated deformation in planar specimens of aluminum–magnesium alloys AlMg5 and AlMg6 is studied by high-speed video filming of moving deformation bands. It is found that the concentration of an elastic field near a hole causes early nucleation of macrolocalized deformation bands and decreases the critical deformation of the first stress drop. Differences between the spatial–temporal patterns of deformation bands near holes under various deformation conditions are revealed.

Nanostructuring of crystals into domains under uniform compression, the ductility of a solid nanostructure under pressure, and the bimodal distribution of domain size are explained based on the dependence of the surface energy and surface pressure on the shape, size, and density of a nanocrystal.

A mixing gasdynamic laser with nonuniform arc excitation is investigated using a model setup. Tentative analysis of the results indicates the appropriateness of using plasmatrons to improve the efficiency of mixing gasdynamic lasers by making carbon dioxide molecules vibrationally more nonuniform. In addition, a plasmatron serves as a preionization source both for a fast-flow gas-discharge laser and for a gasdynamic laser with combined pumping.

We consider the main characteristics of a cell converting the energy of β radiation from a tritium source into electric energy. For such a cell, we propose that the design and technology used for preparing a-Si:H-based solar cell panels be employed.

The change of the immitance of the metal–insulator–metal memristive structures based on SiO_x, which is observed during electroforming and resistive switching, confirms the formation of conducting channels (filaments) in the insulator during forming and their rupture upon a transition of the structure to a highresistance state. The observed switching of the differential capacitance and conductivity synchronously with the switching of current (resistance) can substantially extend the functional applications of memristive devices of this type.

Electronic and optical properties of 2D conducting carbon supracrystals are studied. The band structure is calculated using the tight-binding method. One sample is classified as semimetal, and the remaining samples are classified as narrow-band-gap semiconductors. The optical conductivity of the supracrystalline structures is calculated. It is demonstrated that the conductivity of semimetal supracrystals may be substantially higher than the grapheme conductivity. Complex refractive indices of the supracrystals are estimated.

We construct a model for the formation of a dislocation cluster and its evolution after the detachment of the head dislocation. The results obtained with the help of this model are used for calculating the acoustic emission signal accompanying the stages of cluster formation and breakdown. The elastic stresses in the signal under investigation are estimated. The data on relaxation of elastic stresses in the sample containing the cluster are reported.

An algorithm for the calculation of electrostatic field in an arbitrary region of acceleration in the mass reflector using the criterion of an increase in the spatiotemporal focusing is presented. Nonuniform accelerating field providing spatiotemporal focusing of the third and fourth orders in the presence of uniform field in the reflector is calculated for a mass reflector with ionization on the surface of target. The effect of the size of input window of detector on the resolution in the presence of nonuniform field in (i) ion source and (ii) ion source and reflector is considered.

The magnetic properties and texture of 90-nm-thick polycrystalline Fe/SiO₂/Si(100) films magnetron-sputtered under different working gas pressures are investigated. It is shown that when the pressure declines, the magnetization of the films may grow by 50%, whereas the ferromagnetic resonance linewidth and the coercive force may decrease by more than an order of magnitude. Such variations of the magnetic properties correlate with a Fe(110) to Fe(200) change in the film texture and with the columnar to quasi-uniform microstructure transition.

The structure of the temperature field in a liquid-metal heat-transfer fluid flowing through a T-shaped mixer is studied experimentally. The experiments are carried out using Rose’s alloy as a working fluid. To find the temperature distribution over the wall of a working section, IR thermography is applied. It is shown that the wall temperature distribution in the zone where fluid flows with different temperatures mix is heavily nonuniform. The temperature distribution substantially depends on the ratio between the hot and cold fluid flow rates. The results can be used to verify the thermal hydraulic computational codes for fluid metal flows.

We analyzed the atmospheric pressure plasma jet excited in air and nitrogen by a barrier discharge. The source forming stable plasma jets of length up to 4 cm in air and nitrogen is constructed, and its energy and spectral characteristics are measured.