With the increasing integration of the solar energy system into interconnected lines, solar energy systems have a great impact on power quality issues. This study describes the design of single phase inverters that are used to utilize a solar power system and analyze their performance. This article focuses on modeling a single phase inverter. An inverter is a circuit that converts DC power supplies to AC power supplies. The model is implemented using the MATLAB Simulink software with the SimPower System Block Set based on computer simulation. FFT analysis is used to find harmonic distortion using MATLAB Simulink software

Based on the reference thermodynamic data, a four-component Fe-Zr-Al-Si system is constructed and its mathematical model of the phase structure is created. As a result, it turned out that it consists of 12 elementary tetrahedra. For each of the tetrahedra, analytical equations are defined, with the help of which it is possible to determine the location in the factor space of the general system of compositions of various metal melts with the calculation of their standard phase compositions. The breakdown of the overall system is carried out taking into account congruent connections. The sum of the relative volumes of elementary tetrahedra is equal to one (1.00000), which confirms the correctness of the tetrahedron. Quasi-volumes in the Fe-Zr-Al-Si system are established, which simulate the compositions of the metal products formed during the smelting of various ferrosilicocyrconium alloys during the reduction process . As a result, it was found that the alloy with a 25% Zr content is modeled by the Si-Fe2Al5-FeSi2 - Zr6Si5 tetrahedron, and the alloy compositions with 35 and 50% Zr are decomposed in the Si-Fe2Al5-FeSi2 - Zr6Si5 and Zr5Si3-Fe-Fe2Al5-FeSi tetrahedra, respectively.

The electrohydraulic method of natural diatomite enrichment based on separation of the clay component under the influence of plasma energy arising at a short electric discharge is applied for the first time. Special computer technology is developed for the first time, using the portable navigator Montana series 600 by Garmin, Google Earth and Garmin Base Camp programs to make a contour and area of diatomaceous rocks on Zhalpak territory. Comprehensive study of enriched diatomite using spectral, microscopic, X-ray diffractometric, silicate (chemical), elemental and thermal methods of analysis were carried out. Independent methods of analysis show almost identical results for the degree of diatomite enrichment with silicon oxide (SiO2), being in the range of 78÷81.8%. Based on the results of spectral analysis it can be concluded that the electrohydraulic method is very effective in cleaning diatomite from calcium (CaO) and sulfur (SO3) oxides to the level of 0.21% and 0.18% respectively.

The paper provides a literature review on the mechanisms of damping in alloys. The goal of the authors was to obtain the maximum damping with the minimum alloying. Samples of alloys in cast, annealed and quenched form were investigated. According to the research findings, the characteristics of the damping properties of the alloys are provided and the possible reasons for the high values ​​of the damping parameters are explained. An analysis of the nature of non-metallic inclusions shows that very small non-metallic inclusions do not result in high damping. A very high content of medium-sized non-metallic inclusions leads to low sound emission. High alloying with elements such as Mn, Ni, Nb, Al, one percent each, 1.5% Cr, 1.5% V, 0.5% Mo, 0.5% Ti, 0.5% Cu, does not always provide increased damping properties.

In recent years, many researches have been able to redefine the use of the most basic and richest renewable resource – biomass, especially lignocellulose. This article presents the results on the production of lignin from sawdust waste, as well as the production of lignin fibers by electrospinning. A technique has been developed for the extraction of lignin and the production of inexpensive electroformed fibers from lignin with high performance characteristics for energy storage. The obtained samples (lignin and lignin fibers) were examined by physicochemical methods, such as: IR spectroscopy, Raman spectroscopy, Optical microscopy, Electron microscopy (SEM), Elemental analysis.

Improving hydrometallurgical methods for processing copper-containing sulfide natural materials is an urgent task due to the increasing environmental problems, depletion and complexity of the composition of processed raw materials. The kinetic regularities of the process of extracting copper into solution from the solid phase of bornite by alkaline solutions of glycine and hydrogen peroxide are investigated. The kinetics was studied at room temperature and a concentration of 0.1 M hydrogen peroxide. The glycine concentration varied from 0.1 to 1.0 M. In the studied pH range of the medium (8÷11), glycine exists in the form of glycinate anions that react with Cu2+ ions to form a stable copper (II) glycinate, which contributes to the effective extraction of copper from the mineral into the solution. The introduction of an oxidizer – hydrogen peroxide into the system significantly increased the extraction of Cu2+ ions into the solution. The degree of extraction of copper from bornite in the first 10 minutes varied in the range from 29 to 37 %. The results of the conducted studies allow us to consider alkaline solutions of glycine and hydrogen peroxide as a promising solvent reagent for leaching copper from sulfide mineral raw materials.

This paper considers the optoelectronic properties of porous nanostructured silicon obtained by electrochemical etching method. It was noted that the electrolyte concentration affects the depth of porosity, while the anodizing current density affects the density and size of crystallites, as well as the photoluminescence spectra. The results of the Raman measurement showed a low-frequency shift of the wavenumber on the 504 cm-1 line, which changes the frequency difference Δω to 16 cm-1 wavenumber units, while the cross-sectional diameter of the nanocrystallites is distributed from 2.3 nm to 4.3 nm.

Recognizing a person's actions based on video, as well as their psychological and emotional state, including students, is a complex and urgent task that has social significance. The pace of technological development and the growing interest of experts at home and abroad show that the automation of determining psychoemotional reactions is a practical and popular area of research. This article describes various methods on this topic, briefly describes and analyzes modern systems that recognize human emotional behavior. The existing methods of recognizing human behavior, emotional artificial intelligence, which allows computers to recognize and interpret human emotions and respond to them, are analyzed. The camera reads the person's state, and the neural network processes the data to determine emotions. In addition, recent research papers published during 2019 and 2020 are included to present the latest advances in this field.

The article is devoted to the study of cryptographic properties of S-boxes. S-box is a function that accepts n bits at the input, converts them according to a certain algorithm and returns m bits at the output. n and m are not necessarily equal. S-boxes are one of the main components of modern cryptographic algorithms that determine their nonlinearity. To protect cryptographic algorithms from various types of attacks, S-boxes must meet a number of criteria. The purpose of this work is to study the existing cryptographic properties of S-boxes, which will allow us to further analyze the existing criteria that S-boxes must meet and make a reasonable choice of a set of criteria for optimal S-boxes. This article provides an overview of the main properties of S-boxes that are important in the formation of optimality criteria. Differential uniformity, difference distribution table, nonlinearity, linear distribution table, algebraic degree, algebraic immunity, algebraic complexity, avalanche effect, strict avalanche effect, distance to strictly avalanche effect, completeness, linear structures, balancedness, correlation immunity, bit independence criterion, propagation criterion, period, number of fixed points and opposite fixed points, cycles, inversions, increases, boomerang connection table, boomerang difference table are considered. The existing methods of generating S-boxes with the necessary optimal characteristics are also considered.

The empirical model proposed by us makes it possible to calculate the thickness of the surface of a high-entropy alloy and the anisotropy of its surface energy. Cubic equiatomic compounds with an fcc structure were taken for the study. It was found that these structures in the surface layer have an average thickness of about 2 nm, which represents 5-6 monolayers, which are confirmed by reconstruction or relaxation of the alloy surface. These structures are nanostructured formations. It turns out that the thickness of the surface of these layers is approximately the same as the thickness of the surface of amorphous metals layers. They also have approximately the same hardness of 500-800 HV, but 2-3 times higher than the hardness of stainless steels - 200-400 HV. From our point of view, there is much in common between high-entropy alloys and amorphous metals, despite the fact that the former are crystalline, and the latter are amorphous. In the proposed empirical model, it is shown that the maximum surface energy is attained in the [111] plane. It is also shown that the melting temperature of different faces becomes different and, with a decrease in the particle size, it changes according to the hyperbolic law.