Technical Physics最新文献

In this study, the possibility of using Surfi-Sculpt technology for relief modification of the tungsten surface on a technological electron-beam equipment with an accelerating voltage of 60 kV and an electron gun of the ELA-60 type is investigated. The electron beam power density sufficient for intense evaporation of tungsten and obtaining a relief surface is determined. The dynamics of the surface relief growth rate is analyzed using a six-point star scanning as a function of the electron beam velocity and direction.

Using CST MWS 2023 software, modeling of the S-parameters and the radiation patterns (RPs) of antenna arrays (AAs) based on rectangular graphene microribbons in the THz range has been carried out. It is shown that the unique property of graphene AAs is the possibility of electronic frequency scanning and multiband operation regime, as well as an increase in the gain factor, narrowing of the main RP lobe, a decrease in the level of the side RP lobes with an increase in the value of the chemical potential (from 0.2 to 1.0 eV), and their dependences on the number of AA emitters.

The paper deals with aspects of the development of a methodological approach to normalizing the supply voltage quality in an electrical network by developing an algorithmized method for determining the rational installation location of symmetrization equipment in a motor-loaded electrical complex. The developed method makes it possible to implement processes aimed at ensuring efficient operation of the electrical complex in the presence of an electric motor load under low-quality supply voltage conditions. The proposed method based on software provides design procedures for calculating various options for symmetry and for choosing the most cost-effective technique. Attention is focused on the main criteria for evaluating decisions made in designing the location of symmetrization equipment in the electrical complex. The architecture and basic functional features of the application software as a tool for implementing the calculation method are reviewed. The software is intended for electrical calculations in the design, modernization, and operation of electrical networks. It includes drawing schematic diagrams of sections of electrical complexes with installed symmetrization equipment. The results are presented of experimental studies demonstrating the effectiveness of the developed method in solving problems of voltage symmetry in the supply electrical network. It is obvious that the developed approach based on automatic selection of locations for symmetrization equipment depending on the operating conditions of electric motor load makes it possible to automate the design procedures for voltage normalization in the electrical network. It minimizes voltage asymmetry in power supply and contributes to improving the operational reliability of low-voltage asynchronous motors. The study findings and prospects of using the developed approach are considered both for solving complex design problems and for the economic justification of local design solutions. A detailed analysis and formalization of the study results with relevant conclusions were carried out.

The aim of the work is to evaluate the effect of bone matrix modification by supercritical CO₂. The efficiency of bone matrix treatment with a supercritical fluid is established. Optimal parameters of the sterilization process are identified.

The characteristics of phase equilibria in cytane−propane/butane and diphenyl−propane/butane systems have been investigated in the temperature interval 403–443 K and the pressure range 1.0−6.8 MPa using a high-pressure optical cell. Type-I phase behavior has been found.

A method is proposed for determining the transport characteristics used in the macroscopic heat- and mass-transfer equations for multicomponent media. The method has been based on the kinetic theory of gases. To generalize this theory to a multicomponent medium, its approximation by a basic binary medium has been used. In this study, a two-level approach has been developed, which combines the description of macroscopic processes in multicomponent gaseous media with the microscopic description based on the Boltzmann equation.

Background. The relevance of the topic of this work is due to the need to reduce the level of penetrating interference and improve the quality of the useful signal received by the on-board active interference station. Goal. Improving the quality and functional parameters of on-board frequency-selective systems and structures by adjusting the amplitude–frequency characteristics (AFCs) of filters. Methods. The system analysis of the main parameters, modeling of the frequency characteristics of attenuation and the standing wave voltage coefficient, expert assessments, and research tests have been used. Materials. To improve the characteristics of the filters, it is proposed to adjust (control) the AFCs of the filters. The schemes and topologies of correctors are given. It is shown that with the help of thin-film and thick-film correctors, various frequency response distortions can be eliminated, the slope of the characteristic can be adjusted, and the depth of the AFC dip can be changed. Results. The proposed schemes, designs, and topologies of correctors make it possible to adjust the slope of the characteristics up to 16 dB, change the depth of their dip, maintain the voltage standing wave ratio within 1.35–2.5 in the operating frequency range, reduce the frequency response nonuniformity to 0.2 dB, and the noise factor to 2.3–2.4 dB. To ensure such a level of performance during the adjustment process, it is required to carry out an individual combined adjustment of the resistors in the range from –10% to +30% or functional adjustment according to a template. At the same time, the flare discharge method provides a higher time stability of the frequency response adjustment indicators and a higher yield of suitable products as compared to the laser method. Conclusions. The proposed method of adjusting the AFCs of the filters in a frequency-selective system makes it possible to improve the quality of the useful signal received by the active interference station. Adjusting the frequency response by adjusting the resistances of the corrector resistors by the flare discharge method provides a higher temporal stability of the parameters than the laser adjustment.

The paper presents studies devoted to the study of the heat capacity of propylene homopolymers and propylene–ethylene copolymers, comparison of the data obtained with the composition of macromolecules and the molecular weight of polymers. The paper considers the influence of the molecular weight and ethylene groups on the specific heat capacities of polypropylenes, found by differential scanning calorimetry.

The influence of montmorillonite on the polymerization and properties of photocurable resin has been investigated. It has been shown that montmorillonite added to the binder composition does not retard the curing reaction and does not suppress UV curing. Montmorillonite improves the elasticity modulus and does not influence the glass transition temperature of UV-cured compositions.

The problem of hemodynamics (i.e., blood circulation in vessels resulting from the difference in the hydrostatic pressures in different parts of the circulatory system) has been investigated. For the differential problem in the hemodynamic model of heart, a difference scheme has been constructed and the convergence of the approximate solution to the exact solution has been substantiated. A numerical solution is obtained for the model problem of a single-chamber heart.