The results of studying the effect on the crystal structure and magnetic properties of compounds based on NiMnSb when Ni cations are replaced by Fe and Co cations are presented. The solid solution Ni_1–xM_xMnSb (M = Fe, Co) systems were synthesized by the method of solid-phase reactions. With the help of X-ray diffraction analysis, the presence of a concentration structural transition was established. Using the ponderomotive method, it was found that the temperatures of the “magnetic order – magnetic disorder” phase transformation decrease as nickel is replaced by iron and cobalt. The field dependences of the specific magnetization demonstrate the typical behavior of a magnetically soft ferromagnet. The results of an experiment on the study of the crystal and magnetic structure of solid solutions of the Ni_0.90M_0.10MnSb (M = Fe, Co) systems using thermal neutron diffraction in the temperature range of ~(3–300) K are presented. It is found that the studied compositions exhibit ferromagnetic ordering along the c axis. On the spectra of Ni_0.90Co_0.10MnSb solid solutions in the region of 2Θ  = 28.6° the appearance of a reflection indicating the formation of antiferromagnetic ordering is observed. Within the framework of the density functional theory, an ab initio calculation of the magnetic moments for Ni_1-xM_xMnSb (M = Fe, Co; x = 0; 0.125; 0.250) was carried out. The results of theoretical calculations predict the existence of magnetic moments for Fe and Co ions, and they are antiferromagnetically coupled to the spins of Mn and Ni ions.

Effect of rapid thermal annealing conditions on the specific resistance of the ohmic contacts of Ti/Al/Ni/Au metallization with layer thicknesses of 20/120/40/40 nm to the GaN/AlGaN heterostructure with a two-dimensional electron gas on a sapphire substrate has been discovered by transmission line measurement. Rapid thermal annealing of the samples was carried out by the contact heating from the sapphire substrate side in a nitrogen atmosphere at the temperature range from 750 to 1000 °C for 30, 60, and 90 s. It has been discovered that the dependence of the specific contact resistance on the temperature contains two temperature optimums, at which the specific contact resistance of the ohmic contact is less than 1 ⋅  10^–4 Ohm⋅ cm². The appearance of the first temperature optimum is due to the decrease of the distance from the diffusion front of the low-resistance layer of intermetallic compounds formed during the rapid thermal annealing of the Ti/Al/Ni/Au metallization to the region of the two-dimensional electron gas. Outside the first temperature optimum, an increase in the specific contact resistance of up to 9 ⋅  10^–3 Ohm⋅ cm² is observed, due to the absorption of the AlGaN layer by a low-resistance layer of intermetallic compounds, which leads to the degradation of the two-dimensional electron gas under the contacts and deterioration of its conductive properties. The second temperature optimum is due to the passage of the diffusion front of the two-dimensional electron gas region and the establishment of a side contact between the low-resistance intermetallic layer and the two-dimensional electron gas, which leads to the decrease in the specific contact resistance. With an increase in the fast thermal annealing time from 30 to 90 s the shift of the interval of the first temperature optimum from 800 to 775 °C for the lower boundary and from 825 to 800 °C for the upper boundary, and for the second temperature optimum from 875 to 850 °C for the lower boundary, and from 950 to 875 °C for the upper boundary is observed, which is due to an equivalent increase in the diffusion depth of the Ti/Al/Ni/Au metallization components. The results obtained can be used in the technology for creating GaN-based products with a two-dimensional electron gas.

Electrochemical coatings with a tin-copper alloy were obtained by the method of non-stationary electrolysis. The influence of the parameters of the pulsed-reversed currents (duty cycle, frequency, ratio of the duration of the forward and reverse pulses) on the kinetics of the process, structure, composition, functional and protective properties of deposits has been established. Pulsed electrolysis makes it possible to shift the coprecipitation potentials of alloy metals, expand the limits of the currents used, and form deposits at their high instantaneous values. The copper content in the coatings obtained on the unipolar pulsed current varies in the range of 3.31–4.77 wt.%, and on the pulse-reversed 1.59–1.69 wt.% (2.87 wt.% at direct current). Deposition on pulsereversed currents makes it possible to increase the solder spreading coefficient from 96.38 to 98.20 % and reduce the value of the contact electrical resistance of the coatings from 2.0133 to 1.5067 mOhm compared to the deposits obtained with the direct current. Coatings obtained on the pulsed current with the frequency of 10 Hz and the duty cycle of 3.33 with a copper content in an alloy close to eutectic, have a high coefficient of solder spreading and low contact resistance and are recommended for use in radio and microelectronic equipment for soldering movable and fixed electrical contact connections. 

The article introduces the technique for manufacturing flexible electromagnetic shields based on resistive materials (powdered charcoals and sheet foil), as well as the results of experimental justification of the use prospects of this technique in the development of new functional materials. This justification consisted of: 1) manufacturing of the experimental samples in accordance with the presented technique; 2) carrying out the measurements of the electromagnetic radiation reflection and transmission coefficient values in the frequency range of 0.7–17.0 GHz of the manufactured experimental samples. It was discovered that flexible electromagnetic shields based on the powdered charcoals manufactured in accordance with the presented technique are characterized by the electromagnetic radiation reflection coefficient values in the frequency range of 0.7–17.0 GHz, reaching –10.0 dB, when electromagnetic radiation reflection coefficient values reach –20.0 dB . Due to this fact it is possible to recommend to use them in order to ensure electromagnetic compatibility of radioelectronic equipment and to protect people from exposure to radiation, emitted by such equipment, as well as to hide ground objects from detection in the radar wavelength range. 

In the work, with the help of numerical simulation, the values of technological parameters are established, which provide effective two-beam laser cleaning of quartz raw materials. The optimization of two-beam laser cleaning of quartz raw materials was performed using the MOGA genetic algorithm in the ANSYS Work-bench program. Using the face-centered version of the central compositional plan of the experiment, a regression model of two-beam cleaning of quartz raw materials was obtained. The power density of a laser with the wavelength of 10.6 μm, the power density of a laser with the wavelength of 1.06 μm, the radius of a quartz particle, the radius of an impurity particle, and the processing time were used as variable factors. The maximum temperatures of quartz particles with impurities and quartz particles without impurities were used as responses. The regression model was tested. The results obtained allow us to conclude that there is a necessary correspondence between the regression model and the finite element analysis data. An assessment of the influence of processing parameters on the maximum values of the temperature of quartz particles was made. Optimization of two-beam laser cleaning of quartz raw materials was carried out according to the criterion of minimum processing time when reaching the maximum temperatures of quartz particles with an admixture of the melting temperature and limiting the maximum temperatures of quartz particles without an admixture to values below the melting temperature. Optimization was performed for two combinations of quartz and impurity particle sizes. The parameters obtained as a result of optimization and the parameters obtained as a result of finite element modeling are compared. The maximum relative error of the results obtained using the MOGA algorithm did not exceed 2.5 % when determining the maximum temperatures. As a result of the simulation, processing parameters have been established, the use of which will provide an increase in the productivity of two-beam purification of quartz raw materials.

A histogram filter with smoothing parameter settings is discussed in the article. The histogram filter can be effectively applied in the problems of identification (recognition) of distribution laws for small amounts of data. The smoothing parameter is determined taking into account the available a priori information regarding the proposed distribution law. The relationship between the mathematical expectations of the chi-square fit criterion of the standard estimation histogram and the use of the histogram filter has been determined. This ratio is determined by the smoothing factor. The numerical value of the smoothing coefficient depends on the following parameters: the amount of data, the number of grouping intervals, and the shape parameters of the distribution law. The paper analyzes the feasibility of using a histogram filter, depending on the ratio of the above parameters. The dependence of the smoothing coefficient on the specified parameters allows one to determine the relationship between the number of data grouping intervals and their volume. The histogram filter is an easy-to-implement tool that can be easily integrated into any open distribution law identification (recognition) algorithm

A method for selecting spoofing signals in consumer equipment with a multichannel antenna system is proposed. The method provides for consistent filtering of the received signals at the outputs of all antenna system elements and by ranging codes of all navigation satellites, detection and measurement of the time delay of the true and false navigation signals in each code channel by the output signal of one of the antenna system elements, measurement of the phase difference of the signals at the outputs of the antenna system elements and the selected reference element for the estimated time delay in each channel by code. Compensation of spoofing signals is carried out in the spatial domain by estimating the correlation matrix of processes at the outputs of the antenna system channels by the corresponding countdown of code channel signals after matched filtering and forming of a weight vector while minimizing the output power of spoofing signals by directly inverting the estimate of the correlation matrix and carrying out weight processing of the adopted implementation. The simulation results are presented, confirming the efficiency of the method.

The article presents the study results of the possibilities of expanding the working frequency band of a patch antenna, due to the broadband matching. As a systematic approach, a generalized Darlington method is proposed using flexible approximating functions with increased variable properties. These properties are necessary for the solvability of the system of restrictions on the agreement limits. The results of synthesis by the generalized Darlington method using flexible approximations provide a matching band of 10 %, but have an increased sensitivity of the values of concentrated elements. A synthesis technique in a distributed element basis is also presented. In the synthesis of a matching chain on distributed elements, the Richards transform for homogeneous microstrip lines is used. A comparison of theoretical and experimental results of antenna matching is presented. Synthesis on distributed elements provided a 17 % band with a minimum number of matching elements. The synthesis technique in the distributed element basis can be used to match a wide class of vibrator and slot antennas, the dimensions of which are multiples of a wavelength quarter. 

The article deals with the issues of matching a waveguide transmission line with millimeter wave diodes. The implementation of the transition of a rectangular waveguide to a microstrip switching line in the form of a line of the fin-line type is described. The computer simulation results of the transmission coefficient module of the developed element and the standing wave coefficient by voltage separately for the transition from a rectangular waveguide to a microstrip transmission line and as part of an amplitude detector are shown. A joint application of the developed element with a microstrip detector based on a Schottky diode in the frequency range from 118.1 to 178.4 GHz is proposed. The results of measuring its parameters and the results of determining the sensitivity are given, as well as the evaluation of the results obtained is performed. The obtained results proved the possibility of using the matching element of a waveguide transmission line with a diode in the millimeter wavelength range. 

The paper presents a comparative analysis of the IPv4 and IPv6 data transfer protocols to ensure a given quality of service (QoS). As parameters of QoS, the bandwidth and the associated transmission rate, as well as the amount of delay and jitter – delay variations are analyzed. The main disadvantages and advantages of both protocols are presented in the form of a table. A model of real interaction between networks operating on the basis of IPv4 and IPv6 protocols has been developed and implemented. The throughput, delay and jitter were measured for an IPv4-based network and an IPv6-based network for various packet sizes (MTU) for UDP and TCP traffic. Conclusions are drawn concerning the possibility and prospects for using the IPv6 protocol to provide a given quality of service. 

This paper presents the analysis results of the iterative numerical algorithms use for roots calculating of nonlinear equations systems (Levenberg-Marquardt, Newton’s algorithm, modified Newton’s algorithm, sequential iterations and gradient descent) describing the process of spatial rectangular coordinates calculating of radio emission sources in the angle-difference-rangefinder passive location complexes with different configurations (containing from 2 to 4 receivers). The main objectives of the work include determining optimal number of receiving points and choosing the most effective way to transform the coordinates of the observed parameters vector (a set of range differences and angular coordinates estimates of objects emitting radio signals in relation to the receiver spatial location of the system) into a measured parameters vector (spatial rectangular coordinates of the observation object). The criteria for further comparison of the using analyzed algorithms results were determined by the following characteristics: working area of the passive location complex (the part of the space within which the targets coordinates estimates deviation from their true values does not exceed the maximum allowable values); average error of calculating the target spatial coordinates in the working area; number of coordinate calculating stages of radio sources in the studied part of the space. The results of a comparative analysis of the obtained numerical values by the selected criteria allowed us to conclude that the optimal implementation is the implementation of the angle-difference-rangefinder passive location complexes consisting of four receiving points and the use of the Levenberg-Marquardt algorithm for calculating the spatial coordinates of radio emission sources. 

The generation frequency is ω ≈ kω_н in classical gyrotrons, where ω_н = еB₀/m is the electron cyclotron rotation frequency in a uniform longitudinal magnetic field with induction B₀, e is the electron charge, m is the electron mass, k = 1, 2, 3… is the cyclotron frequency working harmonic number. Thus, the generation frequency ω being tuned is possible only by changing B₀. This way is very inconvenient. It’s necessary a solenoid additional (control) winding. That difficulty can be eliminated in gyrotrons with crossed fields - electric ₀ and magnetic ₀, here ₀ ⊥ ₀. The frequency can be tuned by changing E₀. This possibility can be realized at least two ways: a gyrotron based on a coaxial resonator with radial field E₀; a four-mirror gyrotron on traveling Т-waves with transverse in respect the traveling wave direction to uniform crossed fields – electric ₀ and magnetic ₀. The single-screw electron flow has a rotation frequency , for the first gyrotron type, where , , ΔV is the potential difference between the inner (radius b₁) and outer (radius b₂) coaxial conductors, r₀ is the electron flow rotation radius. Thus, the generation frequency ω ≈ kω_н is determined by both B₀ and ΔV. Moreover, at ΔV = 0 the device becomes a classical high-orbit gyrotron, at B₀ = 0 a classical helitron. Therefore, at B₀ ≠ 0 and ΔV ≠ 0 it should be called a gyrohelitron, the generation frequency of which is tuned electrically - by changing ΔV. The article presents the design schemes of a gyrohelitron and a two-beam four-mirror gyrotron. In both cases, piezoelectric devices realize synchronous tuning of the frequency, just it allows the devices becoming fully electrically controllable. The following results were obtained for the gyrohelitron. Resonator field – H₂₁₁, interaction on the second harmonic ω_s; a) narrow-band tuning 10 %: maximum efficiency – 55 %, minimum efficiency – 25 %; β₀ = v₀/c = 0.27; q = v_0⊥/v_|| = 2; b) broadband tuning 58 %: maximum efficiency – 18 %, minimum efficiency – 14 %; β₀ = v₀/c = 0.2; q = v_0⊥/v_|| = 2. The given results for the gyrohelitron indicate that it is promising to use electrical frequency tuning in a coaxial gyro-BWT and the amplification band in a gyro-TWT, since these devices do not require piezoelectric tuning of electrodynamic structures.