We obtained the analytical expressions for the mean square deviation of errors in estimating the angular coordinates of the target for quasi-optimal algorithms of processing the fluctuating signals in radar meters with a scanning multichannel receiving system under external interference. Analytical estimates are based on the construction and circulation of the Fisher information matrix with a joint estimation of the direction of arrival and power of the fluctuating reflected signal at the output of the isotropic receiving antenna and a parabolic approximation of the mean value of the decisive statistic in the vicinity of the target direction for the processing algorithm, which provides for an estimate of the average power of the reflected signal by the least square method. The research demonstrates the convergence of exact and approximate analytical estimates and the results of computer modeling. We present the results of studying the accuracy of determining the angular coordinates of the reflected signal for typical space-energy cases. It is shown that the estimation error of the angular coordinates of the reflected signal are unbiased, and at small intervals of the correlation of the reflected signal the probability density of estimation error of the target azimuth exhibits normal distribution. In case of large correlation intervals, the distribution significantly differs from normal and acquires a large positive kurtosis and asymmetry with their values depending on the angular differences of the interference source and the target. The obtained expressions can be used to evaluate the effectiveness of quasi-optimal radar meters in the conditions of external interference and in the complex modeling of radar facilities with such meters included.

The authors developed an infrared (IR) cabin with biotechnical feedback, which solves the problems of increasing the efficiency and safety of IR heating procedure. The target audience for the developed IR cabin includes two groups: 1) young people who embrace an active lifestyle (using the IR cabin for health purposes); 2) mature and elderly people, including those with cardiovascular diseases (using the IR cabin for therapeutic purposes). The research conducted determines the effective mode of infrared radiation exposure to a human body. To assess the effectiveness of exposure the authors propose a coefficient equal to the ratio of weight loss of the user to the maximum operating temperature in the infrared cabin at body level. It is established that a person experiences effective heating at the working temperature of air inside the IR cabin (at body level) in the range from 40 to 42 °C. This temperature regime already contributes to intense sweating, but does not yet lead to discomfort and undesirable load on the cardiovascular system. The beginning of the IR heating should be considered the moment when the IR cabin reaches the operating temperature of 40 °C. Based on the monitoring of indicators of the thermal conditions of the IR cabin, it is necessary to automatically maintain the temperature range from 40 to 42 °C during IR heating. Control of the user's physiological parameters during IR therapy and automatic correction of the power of IR radiators will make the IR heating procedure safe for users. The developed IR cabin can be used in health resort and healthcare institutions of the Republic of Belarus.

The paper is dedicated to influence of the rapid thermal treatment of the gate dielectric at a temperature of ~1100 °С on the electrical parameters of the programmable time device with a correction of 512PS8. As the analyzed parameters of the given integrated circuit, the authors have selected breakdown voltage, gate leakage current, charge value of the gate dielectric breakdown with its thermal field tests performed. The breakdown voltage of the p-channel of the test transistor was measured by applying the linear voltage sweep from 0 to -100 V with the step of -0,5 V with the grounded drain and source. The leakage current of the gate Ig leak was determined at the gate voltage of -20 V. For evaluation of the charge properties of the gate dielectric of devices the, the thermal field tests were performed. The quality and reliability of the gate dielectric the authors the breakdown charge control was carried out (Q_bd). It is shown that the rapid thermal treatment of the gate dielectric at a temperature of ~1100 °С during 7 s with its presence on the non-working side ensures the breakdown charge value of 2,040 C/cm², and with its absence - 2,230 C/cm², while during the standard process of creating the given integrated circuit this value constitutes 1,230 C/cm². This means that the most efficient influence on the improvement of quality and reliability of the gate dielectric is ensured by its rapid thermal treatment when missing the silicon dioxide on the non-working side of the wafer. As compared with the standard process of their fabrication, carrying out such treatment allows 5,29 times reduction of the gate leakage current, 3,50 times reduction of the charge states and 1,07 times enhancement of the reliability of the p-channel transistor, and for the n-channel transistor the given values constitute 10,67, 3,50 and 1,81 times, respectively. It is established that the reliability improvement for the CMOS integrated circuits of time devices during the rapid thermal treatment of the gate dielectric is determined by a step-up of its breakdown charge owing to the more perfect microstructure of dielectric, resulting in the rebuild of the charge states both in the bulk and on the boundary with silicon.

We report on the electric transport properties of Si heavily doped with Sb in the temperature range of 1.9 - 3.0 K and at current density of J < 0.2 A/cm². Based on the analysis of the current - voltage characteristics, the resistance values at different current densities are obtained. It was found that an increase in current changes the sign of the temperature coefficient of resistance. At J < 0,045 А/cm², the temperature coefficient of resistance is positive, whereas when the current density exceeds the value of 0,045 А/cm² it becomes negative. To explain this current crossover in the sign of the temperature coefficient of resistance, we performed Hall measurements at a temperature of 2 K, which allowed us to determine the values of the concentration of charge carriers and their mobility. Based on these measurements and taking into account the concentration instability model, we obtained current dependences of the parameters describing the electric transport in semiconductors, such as activation energy, non-equilibrium concentration of charge carriers, mobility, and scattering time of conduction electrons. As a result of the analysis, it was found that the change in the sign of the temperature coefficient of resistance with an increase in current can be explained by the exchange of electrons between the upper Hubbard band, formed by the capture of injected electrons by neutral impurity atoms, and the edge of the conduction band. In this case, delocalization of electronic states occurs with an increase in current. The data obtained are in good agreement with the proposed hypothesis. Possible delocalization mechanisms are considered by analyzing the electron scattering time. As a result, it was found that electron-electron interactions caused by the Coulomb potential are dominant.

In modern clinical practice, the assessment of the state of blood microcirculation and the diagnosis of microcirculatory disorders are extremely relevant in a variety of diseases: in cardiology, diabetology, oncology, dermatology, dentistry, surgery and resuscitation. Microcirculatory disorders are very diverse both in their pathogenesis and in clinical manifestations. Therefore, in the pattern of various diseases and extreme conditions, as well as in the correction of microcirculatory disorders the methods are needed for both operative assessment of the state of blood flow at tissue level and for its long-term monitoring. The interest in the study of the microvascular bed of the circulatory system is sparked by the significant role of capillaries in the implementation of the basic processes of the body's vital activity, in the trophic support of organs and their direct participation in tissue and cellular respiration. The health and life expectancy of a person depend on the coordinated work of the heart, large blood lines, and microcirculation vessels. The authors have studied modern optical methods for diagnosing microcirculation. The feasibility of using the speckle imaging method for noninvasive rapid assessment of the state of the microvasculature of human surface biological tissues has been substantiated. To implement the speckle-visualization method, methodological and software have been developed. The processing parameters that are most optimal from the point of view of the ratio of spatiotemporal resolution and computation time have been experimentally substantiated. The purpose of this work is the experimental testing of the developed methodological and hardware speckle imaging for the diagnosis of microcirculation of human surface biological tissues. The authors have carried out the studies of the state of microcirculation in the superficial blood vessels of the skin during physiotherapeutic procedures and in the imitation of pathology. The results of the studies have proved the feasibility of using the developed software for a high-quality diagnosis of the state of microcirculation of human surface biological tissues: primary changes in microcirculation are revealed, further changes to occur during physiotherapeutic procedures are visualized.

Photocatalytic active materials are very popular in the modern trend of increasing the environmental friendliness of production processes and vital activities. Effective photocatalysts are the oxides of certain metals (titanium, tungsten, zinc, etc.), which can be obtained by electrochemical methods. The additional use of photolithography to force irregularities on the surface of the photocatalyst with a given configuration increases the efficiency of purifying aqueous solutions under the influence of ultraviolet and visible radiation. The purpose of this work is to study the effect of substrate structuring on the liquid flow as part of a model experiment. Modeling in the COMSOL Multiphysics® software package was performed using the finite element method in the approximation of an absolutely incompressible fluid and a k-ε turbulence model. The results obtained made it possible to increase the efficiency of photocatalytic water purification in a flow system in the presence of a photocatalyst with a surface containing configuration elements in the form of ribs with gaps. The optimal dimensions of the ribs according to the results of estimating the liquid flow rate and the region of effective mixing were: rib height h = 0.25-1 mm, rib width w = 1 mm, intercostal gap g = 5 mm. The millimeter range of configuration elements' dimensions makes their manufacture simpler in comparison with the elements of micron and submicron dimensions and helps to expand the options for the technologies used to produce photocatalytic active substrates. In addition to photolithography and electrochemical methods, it is also possible to use chemical etching and sol-gel technology to obtain combined photocatalysts with a given surface configuration.

The article presents the results of quantum-mechanical computer simulation. The purpose of studying the electronic and magnetic properties of twenty crystalline structures based on perovskites of transition metals with the general formula ABO₃ (where A - Ca, Ce, Y, Na; B - Ti, Ta, Nb, Mn, Fe ion; O - oxygen ion) is to assess the possibility of using this group of materials in modern electronic devices. Systematization of fundamental characteristics will allow further describing of the physical mechanisms that occur in structures. Calculations of the fundamental properties of crystals were performed using first-principle methods based on the density functional theory (Density Functional Theory - DFT). The VASP software package (Vienna Ab initio Simulation Package) was used as the simulation tool, which is designed to perform quantum-mechanical calculations. As a result of the simulation, the following characteristics of perovskites of transition metals were established: ABO₃ unit cells have cubic syngony; a number of compounds have a magnetic moment (from 0.26 to 4.39 p®); an analysis of the band structures shows the presence of compounds with a semiconductor (band gap from 1.65 to 2.99 eV) and metallic type of conductivity. The direct-gap type of conductivity was established for only CeTiO₃ compound. The results obtained quantitatively and qualitatively characterize the electronic and magnetic properties of crystalline structures based on ABO₃ perovskites and can be used to develop methods for calculating the basic electrophysical parameters of promising electronic components.

The purpose of the work is to develop the design of a mobile solar power plant with automatic biaxial positioning of solar cells. The authors have developed the algorithm for the operation of a mobile solar power plant and the design of the control unit for the solar cell positioning system. Research and development of a solid-state model of the mobile solar power plant were done using the SolidWorks computer-aided design system. The design optimization for the solar power plant was carried out using computer engineering research. The design optimization of the parts was carried out by the method of generative design. Optimization of the control unit layout was carried out according to the results of studying the thermal processes that occur during steady-state operation using the Flow Simulation SolidWorks research module. It is established that the natural air cooling of the electronic control unit of the mobile solar power plant with this arrangement of elements is optimal and sufficient to ensure its operation in climatic zone B1. The design of the control unit housing ensures IP66 protection. The effect of wind load on the strength characteristics of load-bearing structures has been investigated. The research has established pressurized and turbulence zones, the value of equivalent stresses and deformations in load-bearing structures when exposed to wind speeds of up to 8 points (15 m/s) on the Beaufort scale. The design and materials of the supporting structures of the mobile solar power plant are determined taking into account minimum weight and dimensions, strength characteristics and ease of transportation. Using generative design, a topological analysis of the load-bearing elements of the mobile solar power plant was carried out, which allowed the reduction of their mass by 30 % while maintaining the required design strength.

The paper analyzes the parameters of silicon avalanche LEDs and their use for electron-optical signal transmission systems. The advantages of silicon avalanche LEDs are shown, among which high speed and compatibility with silicon technology should be highlighted. Experimental avalanche LEDs based on nanostructured silicon were fabricated and studied. The results of controlling the electroluminescence spectrum of avalanche LEDs due to the choice of production conditions to form nanostructured silicon are presented. It was found that the temperature of the substrate during the deposition of the surface nanocomposite aluminum + silicon film affected the size of the formed silicon nanoparticles determining the spectral characteristics of avalanche LEDs. This allows shifting the maximum of their emission spectrum to a shorter wavelength region of the visible range due to the forming of smaller silicon nanoparticles. The authors have developed an optical interconnection system consisting of avalanche LEDs based on nanostructured silicon and a microchannel silicon wafer used to transmit a light signal. The study of various operating modes of the developed optoelectronic system was performed and an increase in the efficiency of optocouple based on avalanche LEDs to 0.2% due to the pulsed operating mode was achieved. It is shown that the efficiency of the optocouple increases with LED current and it is the pulsed mode of its operation that is characterized by the maximum current, which is due to more efficient removal of Joule heat in the intervals between pulses, ensuring stable operation of the entire system. The results obtained open up new opportunities for the development of optical interconnections between silicon chips and silicon optoelectronics in general.

The self-heating effect is a major problem for gallium nitride electronic, optoelectronic and photonic devices. Average temperature increase and non-uniform distribution of dissipated power in the gallium nitride high electron mobility transistor lead to the forming of a hot spot in the vicinity of the conducting channel and to degradation of the drain current, output power and gain, as well as poor reliability. The purpose of this work is to develop the design using numerical simulation and to study the thermal phenomena that occur in the gallium nitride high-electron mobility transistor with a graphene-based heat removal system. The objects of the research are the structures fabricated on sapphire, silicon and silicon carbide substrates. The subject of the research is the electrical, frequency and thermal characteristics of the gallium nitride high-electron mobility transistor with a graphene-based heat removal system. The calculation results show that the integration of a graphene-based heat removal element into the design of the high electron mobility transistor can effectively mitigate the self-heating effect and thus improve the device performance. The advantage of the proposed concept is that the graphene-based heat removal element is structurally connected with a heat sink and aims at removing heat immediately from the maximum temperature region, providing an additional heat escape channel. The obtained results can be used by the electronics industry of the Republic of Belarus for developing the hardware components of gallium nitride power electronics.

The aim of the work is analyzing the results of an experimental research of a charge-sensitive amplifier with an adjustable conversion coefficient and a base level recovery circuit fabricated on the master slice array MN2XA030 for silicon photomultiplier tubes. The amplifier is called ADPreampl3. The parameters were measured on a small batch of chips in the amount of 20 samples. In the process of measuring the main parameters of the amplifier, the signal from the SiPM Photonique equivalent circuit was fed to the amplifier input. In the course of measuring the parameters, it was revealed that the spread of the baseline level for the FOut output ranged from -24 to 276 mV with an average value of 85.6 mV. In this case, a voltage changing in the FOoutShift node from -3 to 3 V is sufficient to establish a base level value of FOut output close to zero. When the recovery scheme is disabled, the spread of the basic level for OutA output is from 300 to 800 mV. When the OutAShift output is connected to the zero-voltage bus the average base level for OutA output is 3.72 mV and for OutAinv output it is minus 2.42 mV. The base level at the outputs OutA and OutAinv smoothly changes in the range of ± 0.9 V. At maximum gain, the dynamic range of ADPreampl3 exceeds 20 dB, however, at the same time, the conversion coefficient depends on the value of the input charge. To register large input charges, it is recommended to reduce the output pulse by reducing the voltage at the Gain pin or process the signal from the FOut pin. The output parameters of the experimental samples are compared with the results of computer simulation. The discrepancy between the results of modeling and measurements, peak time and propagation delays of the amplifier signal was revealed. Based on this, a decision to adjust the SPICE parameters of the elements used in the simulation was made.

The paper is dedicated to investigation of the influence of rapid thermal treatment on the microstructure of platinum silicide. The Pt films 43.7 nm thick were applied on the substrates of the monocrystal silicon by means of the magnetronic sputtering of platinum with the purity of 99.95 % on the МРС 603 set-up with the cryogenic pumping to the pressure not worse than 5*10-5 Pa. As an operating medium, argon was used with the purity of 99.933 %. Rapid thermal treatment of samples was performed in the thermal balance conditions by irradiating the non-working side of the wafer with the incoherent light flow in the nitrogen atmosphere during 7 s at the temperatures of 200-550 °C. The irradiation source in the set-up was represented by the quartz halogen incandescent lamps. The comparative analysis was done through the traditional long thermal treatment of the platinum films at a temperature of 550оС for 30 min in the nitrogen atmosphere. Investigations of the platinum silicide microstructure were performed by means of the transmission electron microscopy which demonstrated that the increase in the RTT temperature initiates first the annealing of defects on the inter-grain boundaries, which is evident from the more distinct contrast from the grains, and then one can observe their growth reflecting the forming of the new phase (silicide one). Such progress of changes of the platinum silicide microstructure and of the size of the grains with the increase in treatment temperature is determined by the heat of its forming. As the Pt2Si phase forming heat is minimum and constitutes 10.4-16.8 Kkal/atom of metal, and for PtSi - 15.7-25.5 Kkal/atom of metal, then the forming of a stable PtSi structure requires a higher temperature. The authors carried out calculations of the activation energy of the diffusion synthesis of platinum silicide during rapid thermal treatment. The calculations show that it is 0.37 eV smaller, than during the long thermal treatment. This means that in this case this process is subject to acceleration related to the rupture of the silicon-silicon bonds and electron excitation in silicon under the influence of the photon flow.

To protect electronic systems from the wide-band pulses of electromagnetic radiation, it is proposed to use the shields designed based on needle-punched and felt materials, including those with impregnating liquids. The shielding characteristics of the obtained shields were measured using a test complex of pulsed electromagnetic fields operating on the principle of reproducing ultrashort electromagnetic pulses of vertical (horizontal) polarization with the amplitude at the beginning of the working area of at least 5 and 50 kV/m. The test complex included voltage pulse generators, high-voltage coaxial cables, an antenna feeder, a digital field indicator, a cable and a remote control button. The effective frequency band of the pulse was from 130 MHz to 2.31 GHz. The pulse power at the beginning of the work was 5.34 MW. In each test, 5 packs of pulses were emitted and pulse amplitudes were measured. Each burst of pulses had a duration of 1 s. The pulse frequency in the packet was 1 kHz. The shielding efficiency averaged over the effective frequency band was calculated and the error was determined. The values of electromagnetic pulse shielding efficiency were obtained, which equaled 9.4.15.5 dB for a needle-punched material with a carbon additive, and 9.7...12.4 dB for felt fabric with a layer of polymer metallized film, which allows using them to design the shields to protect electronic systems from the destructive effects of electromagnetic weapons.