卷 63, 编号 5 (2018)

A thermal model of the laser ablative destruction of materials is considered. The method of moments is used to numerically solve nonstationary heat-conduction equation for 1D system. The solution makes it possible to analyze the dynamics of several parameters that characterize the laser ablation, in particular, surface temperature and characteristic thermal length.

Numerical methods are used to study a spatially distributed system of two nonlinear stochastic equations that simulate interacting phase transitions. Conditions for self-oscillations and waves are determined. The 1/f and 1/k spectra of extreme fluctuations are formed when waves emerge and move under the action of white noise. The distribution of the extreme fluctuations corresponds to the maximum entropy, which is proven by the stability of the 1/f and 1/k spectra. The formation and motion of waves under external periodic perturbation are accompanied by spatiotemporal chaotic resonance in which the domain of periodic pulsations is extended under the action of white noise.

The possibility of passing from some characteristic physical parameters (stagnation enthalpy, temperature, pressure, density, etc.) to other preset parameters is investigated within the problem of control over a radial source (vortex) in the regime of the Mach number maintained constant by energy input and an external force (radial electric field in the given case). The variations of the total enthalpy upon the variation of the energy- and force-similarity parameters are demonstrated in the case when the force per unit mass and per unit volume is specified for identical convection current and conduction current, as well as for a conducting current prevailing over the convection current, and vice versa. In the limit of a negligibly small convection current or a conduction current, a transition to analytic solutions is demonstrated for the case of a purely energy action and a purely force action. Analytic dependences of the velocity increment (kinetic energy), temperature, and total enthalpy on the intensities of the external force and energy input, on the Mach number, and on the length of the zone of action are obtained.

We have studied the dynamics of the plasma glow of pulsed discharges (sliding surface discharge and combined volume discharge with plasma electrodes) in the nanosecond range (100–12 000 ns) in stationary air and in the flow behind the front of a plane shock wave with Mach numbers 1.7–5.0 in the shock tube channel. The temporal characteristics of the flow, the radiation spectra, and the discharge currents in air are compared in the pressure range 5–150 Torr, a pulsed voltage of 20–30 kV, and a current of about 1 kA. It is shown that the time of current under various conditions does not exceed 400 ns, and the duration of the glow can reach a few microseconds. It is shown that as a result of energy supply near the planar shock wave front, the decay of discontinuities occurs with the formation of shock waves and contact surfaces. The positions of the plasma glow regions are compared with the positions of discontinuity surfaces of numerically calculated gasdynamic parameters in the flow.

We present the results of studies of the plasma source based on the coaxial accelerator with the slothole channel geometry for plasma acceleration and working gas inlet into the accelerator via the electrodynamic valve. The plasma parameters at the output of the accelerator are measured. The slot-hole channel of the accelerator created higher jet pressure, as compared to the coaxial channel, especially at large distances from the source. The jet pressure reached 10⁶ N/m² at a distance of 0.7 m. The source created moderately pure plasma for a current below 80 kA. The density was (2.5–5) × 10²² m^–3, which was higher than the density obtained with the coaxial gun.

The efficiency of removal of volatile organic impurities in air by a pulsed corona discharge is investigated using model mixtures. Based on the method of competing reactions, an approach to estimating the qualitative and quantitative parameters of the employed electrophysical technique is proposed. The concept of the “toluene coefficient” characterizing the relative reactivity of a component as compared to toluene is introduced. It is proposed that the energy efficiency of the electrophysical method be estimated using the concept of diversified yield of the removal process. Such an approach makes it possible to substantially intensify the determination of energy parameters of removal of impurities and can also serve as a criterion for estimating the effectiveness of various methods in which a nonequilibrium plasma is used for air cleaning from volatile impurities.

Experimental investigation of the low-temperature plasma of a gas discharge initiated in an interelectrode gap where one electrode is a liquid jet cathode and the other is a metallic anode has been carried out. Data are presented for the physical and spectral characteristics of the discharge and plasma composition. The electron concentration and temperature, as well as the vibrational and rotational temperatures of the heavy component have been estimated. The form and type of the discharge and also gas-hydrodynamic and thermal processes at the interface are described.

Structure, optical properties, and resistance to sputtering are studied for a reflecting Mo-coating that is fabricated using magnetron deposition with simultaneous low-energy ion sputtering at the deposition rate that is higher than the etching rate. A Mo-polycrystalline mirror is used as a substrate. It is shown that the coating exhibits textured nanocrystalline structure with a relatively low spread of crystallite sizes and high resistance to sputtering. It is also demonstrated that the spectral reflection coefficient of such a Mo-coating differs from the spectral reflection coefficient of polycrystalline and single-crystalline Mo and the difference results from the effect of the structure of coating on its optical properties. A theoretical model of the coating formation is proposed.

Data are presented of plane-wave experiments aimed at determining the dynamic strength of 3M titanium alloy with a surface processed by a microsecond electron beam. It has been found that the dynamic strength of processed specimens is higher than that of unprocessed specimens. Metallographic examination of test specimens has revealed spallation macrofracture inside the unprocessed specimens and spallation microfracture at the interface between the hardened layer and the substrate in the beam-processed specimens.

The leading edge erosion of a low-energy high-current electron beam injected into a low-energy neutral gas in a magnetic field has been investigated. The system’s parameters at which a virtual cathode arises, the erosion duration of the beam leading edge, and the time of complete charge neutralization have been determined.

Mass-spectrometry of negative ions is used to study dissociative electron capture by molecules of several nucleosides, simplest di- and tripeptides, and modified dipeptides. Energy domains and efficiencies of dissociative capture are determined for the objects under study, and threshold energies of several fragmentation processes are estimated. It is shown that cytidine and peptides are stable against fragmentation due to simple bond breaking at electron energies ranging from ~0 to 1 eV.

A new method for adaptive filtration of experimental EEG signals in humans and for removal of different physiological artifacts has been proposed. The algorithm of the method includes empirical mode decomposition of EEG, determination of the number of empirical modes that are considered, analysis of the empirical modes and search for modes that contains artifacts, removal of these modes, and reconstruction of the EEG signal. The method was tested on experimental human EEG signals and demonstrated high efficiency in the removal of different types of physiological EEG artifacts.

We have analyzed the isotope separation in a high-frequency plasma circulating centrifuge operating with a product flow. The rotation of a weakly ionized plasma is ensured by a rotating magnetic field, while the countercurrent flow (circulation) is produced by a traveling magnetic field. We have calculated the dependences of the enrichment factor and the separative power of the centrifuge on a product flow. The optimal characteristics of the separation unit have been determined.