Technical Physics最新文献

We consider the effect of failures in the transceiver modules on the characteristics of a phased antenna array. Built-in monitoring circuits are proposed and conclusions are drawn concerning the possibility of detecting failures in modules and correcting the characteristics of the radiation pattern of the antenna.

This study presents a method of X-ray photoelectron spectroscopy that facilitates the analysis of both photoelectron peaks excited in vacuum without inelastic energy losses, as well as the adjacent energy loss regions. Using this method, the changes in the allotropic modifications of carbon materials subjected to helium plasma exposure, simulating conditions at the plasma-wall interface in nuclear fusion reactors, as well as deuterium plasma exposure in the EAST tokamak, were comprehensively investigated. Additionally, the effects of helium plasma on the fine-grained dense graphite grade FDG-8 were examined. The results indicate that the surface of the FDG-8 graphite sample exposed to plasma transitions to a structure resembling pyrolytic graphite. Furthermore, the graphite utilized as first-wall material in the EAST tokamak was analyzed. Findings demonstrated that operating graphite materials in the EAST tokamak leads to a transformation of the near-surface layers of graphite into amorphous diamond-like structures, which in turn results in the formation of diamond crystals on the surface of the graphite. Consequently, the carbon coating on the EAST tokamak acquires dielectric properties, rendering such coatings unsuitable for use as plasma-facing materials. The study also discusses the potential for developing graphite-based coatings with properties essential for effective first-wall materials.

Experimental data on total normal emissivity ε_tn of manganese in the temperature interval 423‒1823 K are presented. This study covers all stable solid-phase polymorphs and liquid state of the metal. It has been found that the temperature dependence of ε_tn is consistent with phase transitions in the material. The stepwise variation of parameter ε_tn in going to the liquid phase has been observed. Comparing experimental data with results calculated based on Foote’s approximation has shown that this approximation is hardly applicable to materials with pronounced allotropy. Results reported in this paper may find application in pyrometry and high-temperature metallurgical processes.

The results of numerical 3D modeling of free-convective heat-transfer processes in a small-sized “warm baseboard”-type heating systems are reported. The thermal and hydrodynamic parameters of the heated air flow are calculated for the vertical channel of the baseboard system, which is formed by two horizontal hot tubes with transverse ribs. The criterion dependences of the effective coefficient of heat transfer from the main structural and mode parameters of the system to air being heated are obtained. It is shown that due to the presence of tubes in the channel between the ribs, the heat-transfer coefficient that can be calculated using the found correcting factor decreases. The optimal values of the gap between the ribs and heating tube diameter, which ensure the maximal specific (per unit length) heat flux from the surrounding medium, are determined. Comparison of the calculated data with experimental results shows their satisfactory coincidence. The obtained results can serve as the basis for developing the methods for designing such heat-exchange heating systems. It is shown that the proposed optimal geometrical parameters of the baseboard system ensure a considerable increase in the heat power as regards the maximal values (by 30–40%) and in the possible range of variation of the specific heat power of baseboard system as compared to the known variants of such systems.

The adhesive strength of coatings prepared by electric arc metallization from a flux-cored wire consisting of a steel shell and a FeCr + Al charge has been studied. From experimental data, a number of process factors have been revealed and a functional dependence that makes it possible to substantiate metallization conditions optimal for the growth of high adhesive strength coatings has been derived.

The purpose of this work is to study the effect of the imbalance of the supply voltage on the service life of an asynchronous motor (AM) with a short-circuited rotor. The main attention is paid to the dynamics of changes in the service life of low-voltage asynchronous electric motors of several series depending on the level of voltage imbalance. Asynchronous electric motors of the classic (4A and AI) and upgraded (5A and AI) series serve as objects under study. Efficient and reliable operation of electric motors is characterized by the service life of the insulation of the windings. A qualitative assessment of the operational reliability of AM is determined by the accuracy of forecasting the real life of their service. Thus, it becomes obvious that the adequate assessment of the operational reliability of low-voltage asynchronous electric motors operating under conditions of low-quality supply voltage directly depends on the complex study of such an external factor as the imbalance of the supply voltage. The problems of the study are solved using the SimPowerSystems software of the Matlab/Simulink interactive programming environment. The research was carried out on asynchronous motors with a short-circuited rotor of classic (4A132S4 and AIR160S8) and upgraded (5A132M6 and AIR132S4) series at P_l = 7.5 kW and a rated rotation rate of n = 1500 rpm. Physical processes of the electric motors are simulated using variations in the negative-sequence voltage imbalance factor (K_2U) from 0 to 5% with a step of 1%. The simulated results are used to construct diagrams of the change in the service life of AM versus external effect. The study based on the SimPowerSystems computer modeling makes it possible to predict changes in the service life of AM, estimate the limits of permissible values of the negative-sequence voltage imbalance factor, and compare electric motors with respect to stability against an external factor. A comprehensive solution of problems related to improvement of the operational reliability of low-voltage asynchronous electric motors is among the priority tasks, mainly aimed at efficient functioning of the electrical complex with an electric-motor load. A detailed assessment and analysis of the effect of imbalance of supply voltage on the operational reliability of low-voltage asynchronous electric motors are performed. The results of the study are discussed, and recommendations for the use of asynchronous electric motors in the presence of imbalance of the supply voltage are formulated.

We describe the techniques and results of measurements of the thermal density of the plasma flux to the test materials in experiments on controlled nuclear fusion. The heat flux has been measured using three different methods: based on the Fourier law (temperature difference in the line of thermocouples in the bulk of the sample), the Stefan–Boltzmann law of radiation (for high temperatures on the surface facing the plasma), and from the temperature difference and the cooling fluid flow rate at the inlet and outlet of the sample cooling system. Experimental values have been obtained for the coefficient of heat-transfer from the helium plasma to the tungsten sample surface.

We describe the algorithm of tangential velocity selection of moving targets with the introduction of the additional synthesis channel displaced relative to the main channel for radars with a synthesized aperture.

An algorithm for implementing a matched filter on a FPGA for a phase-code-shift keyed signal is described. Using complex signals in onboard radar stations allows achieving higher resolution in range and speed, and using a matched filter for such a signal increases the signal-to-noise ratio (SNR).

In this study, we consider the synthesis of a surfactant from an oleochemical raw material. Physicochemical properties of the resulting substance are investigated to determine the optimal targeted application in industry. Using IR spectroscopy, the reaction mixture is tested during the synthesis for different reagent ratios to determine more exactly the structural formula of the obtained chemical compound.