Сomposite materials based on the epoxy resin–W system with varying W content (0–80 %) were obtained using the method of chemical curing. Microstructural investigations of the samples showed that with increasing W content there is a more uniform distribution of grains in the epoxy resin matrix could be observed. Agglomeration of W grains is noted for samples with filler content up to 40 %. Statistical analysis of the grain size of the initial W powder revealed that the probable diameter of W grains is 475 nm. The values of effective and relative densities of the experimental samples were obtained using the Archimedes method. The effective density varied from 1.16 to 4.36 g/cm³ with W powder content rising. The relative density values received ranged from 91 to 94 %, indica ting that there were no significant defects in the samples. X-ray diffraction analysis showed the presence of vcc-W and WO₂ phases, indicating the oxidation of W in the thin surface layer of the powder. Calculation in Phy-X/PSD software allowed to evaluate the gamma radiation shielding efficiency for the epoxy resin–W system composite materials in 0.8–2.5 MeV energy range. It was observed that samples with filler content of 60 and 80 % were the most suitable for radiation shielding. It was found that the addition of W powder to the epoxy matrix contributed to the reduction of half attenuation layer values by 3.5 times from 9.448 to 2.672 cm for samples with 0 and 80 % W content, respectively, for 1.25 MeV radiation energy. The obtained results demonstrate the high efficiency of the proposed composite materials for shielding gamma radiation, which makes them a perspective candidate for manufacturing radiation shields.

Fiber-optic sensors for identifying liquids and determining the concentration of solutions have been studied with the possibility of using various types of single-mode optical fibers produced by industry and widely used in optical cables and telecommunications to create sensors for identifying liquids and determining the concentration of solutions. To identify liquids with different refractive indices and determine the concentration of substances dissolved in water, the peak value of the reflectograms of the optical fiber located at the interface between the optical fiber core and the environment can be used as an information parameter. The value of the information parameter depends on the refractive index of the liquid in which one end of the optical fiber is located. The parameters of fiber-optic sensors for identifying liquids and determining the concentration of solutions were studied by optical reflectometry in different wavelength ranges of optical radiation with a duration of reflectometer probe pulses from 25 to 300 ns. It has been established that the fiber-optic sensor can operate at any wavelength of optical radiation corresponding to the transparency windows of the optical loss spectrum of the optical fiber. The influence of the length of the optical fiber between the recording device and the place where the concentration of a liquid solution is determined using a fiber-optic sensor was studied. The possibility of creating a fiber-optic sensor for determining the concentration of the liquid solutions based on optical fibers has been demonstrated.

Research has been carried out on the formation of tubular aluminum oxides by local electrochemical anodization in aqueous solutions of organic acids such as formic, citric, tartaric, malic and others. Self-ordered nanostructures formed this way can be used in the manufacture of various optical devices. Tubular aluminum oxides formed by local electrochemical anodization in organic acids have a high concentration of anionic complexes containing carbon atoms over 10 at.%. Studies of reflection spectra showed effective anti-reflection properties of films with a specular reflection coefficient of 0.7–1.4 %.

The use of dual-gate field-effect transistors located on the base matrix crystal MH2XA031, controlled by a p–n junction needed to reduce the input current of operational amplifiers is studied. Typical circuits of operational amplifiers, containing: source repeaters connected to the inputs of the operational amplifier on complementary bipolar transistors; input differential stage on p-JFET with a “current mirror” load on n–p–n-transistors; input differential in the form of a “folded cascode” on a p-JFET are analyzed. To minimize the input current, it is re commended to use bootstrapped feedback to keep the drain-to-source voltage of the input JFETs low, independent of the input common-mode voltage, and to connect only the top gate of the dual-gate JFET to the op-amp input. The electrical circuits for MH2XA031 elements and the results of circuit simulation of the developed amplifiers, called OAmp10J, OAmp11.1, OAmp11.2, are presented. Accounting the established features of the input stages and operating modes of active elements in circuit design will allow to create an operational amplifier with the required combination of basic parameters.

The possibilities of improving the output characteristics of the helitron in two directions have been studied – increasing the efficiency in the phase selection mode of electrons and increasing the operating frequency through the use of a multi-lamella electrodynamic system (increasing the azimuthal index n of the operating mode). The results obtained during the experiments indicate the unique capabilities of the helitron at very high harmonics of the electron orbital frequency: up to n = 96, the device has an acceptable efficiency for low-power generators in the electron phase selection mode. This opens up prospects for using such a generator in the millimeter wavelength range. However, in this range, instead of a high-frequency multi-lamella line, an azimuthally corrugated rod with a depth of longitudinal grooves ∆r = λ/4 should be used. This is most effective in providing thermal conditions.

Analytical relations and a methodology for calculating the performance indicators of communication and multimedia broadcasting systems using multi-position modulation types (QAM-M, FM-M, FM-M, CHMS-M, AM-M, OFM-M) and multi-stage coding based on non-systematic convolutional codes and non-binary block Reed-Solomon codes are proposed. The relations obtained are common for studies of noise immunity, corrective capacity, energy and information efficiency of systems, depending on the requirements for reception reliability, modulation format, type of codes used and their parameters. The calculation of the characteristics of systems with cascade composite coding is carried out in a closed form and does not require the use of complex computer simulation procedures.

The confrontation between radar stations and radio electronic countermeasure systems leads to constant advancements on both sides as electronics continue to develop. This multifaceted confrontation determines the success of each side primarily based on the comprehensiveness of analysis and the correctness of the adopted system decisions. Occasionally, decisions are made in pursuit of quality, resulting in success in one aspect but failure in another. One such example is the transition to building radar stations based on true coherence principles. This work highlights the issue of protecting radar stations with true coherence from simulative interference. A method is presented for protecting against “near” simulative interference, which is the most dangerous and is generated between the radar stations and an aerial vehicle equipped with a radio electronic countermeasure systems. The method is based on combining an impulse probing signal with a random initial phase and coherent inter-period accumulation of the received signal.

Low probability of intercept performance of direct-sequence spread-spectrum system with chaotic spreading sequences is investigated. The energy detectors, synchronous and asynchronous, coherent and non-coherent structures are studied here to detect the presence of chaotic direct-sequence spread-spectrum signals. Simple detection approach using a binary correlation function to detect nonbinary chaotic sequences is proposed. The expressions of detection probabilities of chaotic spreading signals are derived. Comparisons between systems using chaotic and binary sequences are given in terms of the low probability of intercept performance, and the performance improvement with chaotic spreading sequences is observed.

It is shown that during digital beamforming in a subaperture antenna array of highly informative space radars with synthetic aperture, it is necessary to provide a procedure for equalizing the time delays of the subaperture output signals for transmission and reception. It has been established that losses in the signal-to-noise ratio on a radar image of a point target for a typical aperture size at an elevation angle of 0.7 m and a signal spectrum width of 600 MHz reach 2.1 and 7.5 dB for off-nadir angles of 21° and 50°, respectively. Recommendations are formulated for equalizing time delays for transmission and reception based on spectral processing. Simulation results are presented.

Measuring the parameters of the antenna pattern is an urgent task in the development and operation of radio engineering systems. This problem can be solved by various methods of antenna measurements. In this case, depending on the radiation zone of the antenna, two main groups of measurement methods are distinguished: methods of direct measurements in the far-field and methods of reconstructive measurements in the near-field. Methods of antenna measurements in the far-field, which allow obtaining direct results, are the most developed and simple, since in the case of the far-field, the angular distribution of the field, regardless of distance, is characterized by a radiation pattern. Methods of the near-field are based on measuring the amplitude-phase distribution of the orthogonal components of the electromagnetic field in the near zone with subsequent recalculation of the parameters and restoration of the spatial radiation pattern of the antenna under study. The comparative analysis of the main groups of antenna measurement methods shows that at the present stage of their development, due to a number of advantages, measurement methods in the near-field with subsequent reconstruction of the radiation pattern of the studied antenna in the far-field are most widely used.

Determination of optical, mechanical and electrical characteristics is one of the decisive factors in the design of instrumentation structures of thermal uncooled bolometer-type detectors (microbolometers). The paper presents the results of optimization calculations by means of computer simulation of absorption, transmittance and reflection spectra of device structures of microbolometers based on thermosensitive vanadium oxide film by finite-difference time-domain method (FDTD). The characteristics of the investigated microbolometer structure were checked for compliance with mechanical and electrical requirements for this class of devices.

The method for studying the biomechanics of breathing has been developed to determine the volume of inhaled and exhaled air. The technique is based on recording the movements of the walls of the chest and abdomen of a person during breathing. A video camera was used to record movements of the chest and abdominal walls, with a spirometer used as the reference method for measuring lung volumes. According to the proposed technique, studies were conducted among 63 people (age – 18–26 years, body mass index ranged from 18.1–32.6 kg/m², height – 160–192 cm). Statistical processing of the results showed a strong relationship between the measured volu mes and the relative deviations of the walls of the human chest and abdomen. The developed technique for studying the biomechanics of breathing can be used for indirect assessment of lung volumes.

The article deals with the problem of three-dimensional reconstruction of the human lumbar spine using the Marching Cubes and Dual Contouring surface triangulation algorithms for subsequent planning of a surgical intervention based on the analysis of digital computed tomography images. 3D reconstructions of the human lumbar spine are presented, as well as the results of a comparative analysis of the developed methods according to the following criteria: mesh generation speed; the number of generated cells; the absence of conflict situations (intersections of the surface). The optimal algorithm for solving the problem is determined on the basis of a comparative analysis.

The purpose of this article is to perform analytical and prognostic studies on the recognition of Alzhei mer’s disease based on decoded text speech data using machine learning algorithms. The data used in this article is taken from the ADReSS 2020 Challenge program, which contains speech data from patients with Alzhei mer’s disease and healthy people. The problem under study is a binary classification problem. First, the full texts of the interviewees were extracted from the transcribed texts of the speech data. This was followed by training the model based on vectorized text features using a random forest classifier, in which the authors used the GridSearchCV method to optimize hyperparameters. The classification accuracy of the model reached 85.2 %.

Searching for faulty, and therefore operating in abnormal mode, solar panels at a power plant is an urgent task in the context of the development and growth of the share of solar energy in electricity generation. The research is aimed at developing and evaluating the effectiveness of a new methodology and software algorithm for searching for anomalies in the operation of solar panels based on the results of a digital twin created and trained using telemetry data from a solar power plant. The methodology is based on studies of deviations in power values at the point of maximum efficient operation of the solar panel, calculated by the digital twin, from the average statistical values for the power plant. Using the proposed methodology, over six months of direct observations, 16 anomalies in the operation of the solar panels of the power plant were discovered and confirmed. It has been established that when analyzing deviations of normalized power values at the maximum power point P_N, it is possible to detect solar panels that have defects or operate with loss of efficiency.