The results of study of the giant magnetoresistance coefficient (GMR) in multilayer micro- and nanowires based on successively alternating ferromagnetic (Co, CoNi and NiFe) and diamagnetic (Cu) layers are presented in the paper. The samples were obtained by electrochemical deposition into the matrix pores. Aluminum oxide was used as matrices. To establish the influence of the aspect ratio, matrices of two types were used: with a pore diameter of 8 µm and 170–200 nm and a variable thickness from 10 to 60 µm. Investigations of the GMR coefficient were carried out by measuring the current-voltage characteristics in external magnetic fields up to 130 mT. When using type I matrices (pore diameter 8 μm), a positive GMR coefficient (an increase in electrical resistivity in an external magnetic field) was noted, while when using type II matrices (pore diameter 170–200 nm), a negative GMR coefficient was established (a decrease in electrical resistance in an external magnetic field). This is due to the enhancement of the interactions of spin-polarized electrons in the magnetic layers through the copper layer through the RKKY exchange with an increase in the aspect ratio. A significant effect of the composition of the ferromagnetic layer (Co, CoNi, and NiFe) on the value  of the GMR coefficient is noted. The maximum value of the negative GMR coefficient (up to –27.5 %) was established for the CoNi-based nanowire system. The use of multilayer micro- and nanowires, electrolytically deposited in a matrix of aluminum oxide with the ability to control the GMR coefficients, opens up perspective use of these objects as sensitive elements (sensors) of a constant magnetic field, as well as devices for storing magnetic information with a vertical principle. 

Sr2FeMoO6–δ single-phase samples without Fe/Mo cations superstructural ordering (P) and with Curie temperature 407 K were obtained by the solid-phase technique. According to the XRD data, the growth dynamics of the parameter P is nonlinear. In this case, the process of reaching maximum values of P (Pmax) is long and its rate is several times lower than the change of the oxygen index 6–δ. It was found that with increasing temperature of isothermal annealing, P increases and reaches maximal values 88 % at T = 1320 K for 120 h, Pmax = 92 % at T = 1420 K for 100 h, while Pmax = 90 % at T = 1470 K for 45 h. One can assume that the lower values of Pmax at T = 1470 K than at T = 1420 K are due to the influence of thermal energy on the destruction of chain ordering of Fe and Mo cations placed in staggered order. Based on the analysis of P time dependences, two relaxation processes can be found and the dP/dt = ¦(t) can be divided into two regions – I and II. In the region I the relaxation time is shorter than that in the region II. The point is that the ordering of cations in the –O–Fe–O–Mo–O chains in the region I requires atomic displacements by approximately one interatomic distance, whereas in the region II cation displacements occur over long distances with the formation of long[1]chain long-range ordering.

Onboard the International Space Station (ISS), as a part of the “Uragan” Earth exploration experiment, various observation devices are used, including photo and video spectral equipment, the orientation of which is carried out manually by the crew through the portholes. However, severe limitations are imposed on the planning of such experiments, primary related to the necessity taking into account the crew’s daily routine and the availability of time allocated for scientific experiments. The solution for expanding the ability to conduct experiments is the employing of automated orientation platforms (OP). One of these OPs is the video spectral equipment orientation system SOVA-1-426. A method for orientation angles forecasting of optical instruments for pointing at predefined objects on the Earth’s surface with SOVA-1-426 is presented. Moreover, in the described method, in addition to the coordinates of the center of mass, the current orientation of the ISS is taken into account, which makes it possible to perform the forecast with better precision. Taking into account the ISS orientation is carried out through the use of the ISS rotation quaternion to control the platform in automatic mode. The presented method for the orientation angles forecasting of high-resolution photo-camera aboard the ISS by employing SOVA-1-426 allows its automatic alignment on the Earth’s surface objects with accuracy up to seven kilometers. The described method is implemented in software and is currently used in the SOVA-1-426 OP aboard the ISS for the remote sensing of the Earth’s surface.

The problem of increasing the efficiency of coding of halftone images in the space of bit planes of differences in pixel values obtained using differential coding (DPCM – Differential pulse-code modulation) is considered. For a compact representation of DPCM pixel values, it is proposed to use a combined compression encoder that implements arithmetic coding and run-length coding. An arithmetic encoder provides high compression ratios, but has high computational complexity and significant encoding overhead. This makes it effective primarily for compressing the mean-value bit-planes of DPCM pixel values. Run-length coding is extremely simple and outperforms arithmetic coding in compressing long sequences of repetitive symbols that often occur in the upper bit planes of DPCM pixel values. For DPCM bit planes of pixel values of any image, a combination of simple run length coders and complex arithmetic coders can be selected that provides the maximum compression ratio for each bit plane and all planes in general with the least computational complexity. As a result, each image has its own effective combined encoder structure, which depends on the distribution of bits in the bit planes of the DPCM pixel values. To adapt the structure of the combined encoder to the distribution of bits in the bit planes of DPCM pixel values, the article proposes to use prediction of the volume of arithmetic code based on entropy and comparison of the obtained predicted value with the volume of run length code. The entropy is calculated based on the values of the number of repetitions of ones and zero symbols, which are obtained as intermediate results of the run length encoding. This does not require additional computational costs. It was found that in comparison with the adaptation of the combined encoder structure using direct determination of the arithmetic code volume of each bit plane of DPCM pixel values, the proposed encoder structure provides a significant reduction in computational complexity while maintaining high image compression ratios.

The changes of distances less than ~10–21 are registered during the gravitational wave experiment. This feature determines the minimum size of experimental installations and the frequency range of gravitational wave detectors. To expand the frequency range and increase the sensitivity of gravitational interference detectors, it is necessary to increase the linear dimensions of the detector significantly as big as Earth and even more. The Republic of Belarus has experience in the development, launch and operation of satellites, the use of which can significantly increase the linear dimensions of the gravitational space detector. The satellite systems as a space detector of gravitational waves S-LIGO-NxR-zy are considered. The S-LIGO-NxR-zy space gravitational wave detector is a system of laser interferometers consisting of x number of satellites with given z-type orbits, in orbit of planet N of the solar system. The interferometers in such systems are identical to interferometers with oscillating mirrors due to the complex satellite motion. The purpose of this work is to study the influence of the kinematic parameters of satellites on the detected signal in the S-LIGO-E2R-z2 system. The configuration of the space detector determines the set of satellite orbits, direction and initial phase of movement. The detector signals depend on the instantaneous distance between the satellites and can be described as periodic functions. There are obtained the equations that describe the periodic changes in the signal between satellites as a result of their relative motion, depending on the initial conditions for launching the satellites. The general case for arbitrary oriented orbits and two special cases for collinear and orthogonal circular orbits in space gravitational wave detectors S-LIGO-E2R-z2-p and S-LIGO-E2R-z2-o are considered in the paper. The graphs of the dependences of the detected signal on the kinematic parameters of the satellites of the detectors S-LIGO-E2R-z2-p and S-LIGO-E2R-z2-o are presented. It is shown that the detected signals contain sections of zero intensity, and the duration and frequency of sections of zero intensity are related to the kinematic parameters of satellites.

The purpose of the work was to substantiate a mathematical model of the signal reflected from moving radar target at the time of its observation, which determines the need to take into account the range migration and its derivatives up to the third order, inclusive, and the Doppler frequency migration, and the basic algorithm of long-term coherent accumulation for the reflected signal. The algorithm provides for the calculation of the “fast” spectra samples, within each repetition period, time, the phase alignment of the spectra samples by multiplying by the correcting phase factors determined by the expected parameters of the target movement and the number of the repetition period, the summation of the spectral samples in the “slow” time, the multiplication of the result by complex frequency response of a matched filter of a single signal and performing an inverse Fourier transform. The performance of the algorithm is illustrated by the results of computer simulation.

The total probability formula for continuous random variables is the integral of product of two probability density functions that defines the unconditional probability density function from the conditional one. The need for calculation of such integrals arises in many applications, for instant, in statistical decision theory. The statistical decision theory attracts attention due to the ability to formulate the problems in a strict mathematical form. One of the technical problems solved by the statistical decision theory is the problem of dual control that requires calculation of integrals connected with the multivariate probability distributions. The necessary integrals are not available in the literature. One theorem on the total probability formula for vector Gaussian distributions was published by the authors earlier. In this paper we repeat this theorem and prove a new theorem that uses more familiar form of the initial data and has more familiar form of the result. The new form of the theorem allows us to obtain the unconditional mathematical expectation and the unconditional variance-covariance matrix very simply. We also confirm the new theorem by direct calculation for the case of the simple linear regression.

 The algorithm of detection of acoustic noise provided by an unmanned aerial vehicle (UAV) in the noise background due to wind is synthesized in the article. Creation of the algorithm has been carried out using the Neyman – Pearson lemma. The algorithm assumes a combination of the stages of wind noise coherent compensation and coherent accumulation of UAV’s acoustic noise sound pressure impulses. The coherent accumulation time matches doubled time of fluctuation correlation resulted by experimental research of acoustic noise of different types of  UAVs. Efficiency of the developed algorithm of UAV detection depends on flight velocity, foreshortening, amount of blades and rotor turnovers of UAV as well as weather conditions. For the probability of a false alarm value of 10–4, the probability of correct UAV detection value of 0.9 is provided wherein signal-to-noise ratio has a value of 8 dB. These indicators correspond the detection range of 200 to 300 meters. The obtained results allow discussions about perspective of acoustic UAVs detection systems adaptation. 

 The relevance of the study of automatic sensitivity control systems (ASC) is determined by their demand for the creation and modernization of radio receiving paths (RRP) with increased noise immunity for radar systems, radio navigation and radio communication. The article analyzes typical attenuating ASCs, which are traditionally widely used to match the dynamic range (DR) of the RRP with the DR of a group radio signal, determined by the current state of the electromagnetic environment at the receiving system location. The fundamental possibility of increasing the noise immunity of RRPs with attenuating ASCs is shown on the basis of the current analysis of the resulting output signal in the IF main filter band. At the same time, it was found that the procedure for determining the optimal value of the attenuator transmission coefficient is characterized by low response speed. In addition, an increase in noise immunity in a RRP with such ASC leads to a significant loss of sensitivity. To overcome the disadvantages of attenuating ASCs, structures that implement the exchange of the transmission coefficient of the RRP to DR and linearity are proposed. Studies of various possible ASC structures have shown that with a proportional exchange of the transmission coefficient for the DR, an improvement in the noise immunity of the RRP is provided while maintaining a high sensitivity of the system. An original ASC system is proposed, which is invariant to the sampling step of the transmission coefficients of controlled elements with increased performance. The considered structural solutions and algorithms make it possible to optimize the technical appearance of RRPs for radar, radio navigation and radio communication with increased noise immunity and to adapt their characteristics to the conditions of nonstationary electromagnetic environment. 

The model and the description of the numerical assessment of uncertain (fuzzy) controls in the implementation of the crisis management in the so-called "gray area", combining transient states of the system, is presented in the article. The behavior of the economic (financial) system is described by a multidimensional vector, for example, the Altman five-factor model. The estimates given by this model are distributed over three ranges, corresponding to the stable state of the system, the negative state, and the "gray area" in which the trajectory of movement towards the bankruptcy zone is outlined and consisting of the states which can be evaluated by means of fuzzy variables, characterizing proximity to the bankruptcy zone. According to the values of these state variables, controls must be implemented to bring the system into a stable favorable zone. The general apparatus for determining crisis management strategies is sufficiently developed, at the same time, the determination of the numerical characteristics of these controls, as an independent task, requires further formalization and development of numerical methods. This article contains one possible formalization  and its implementation using the analytical library of the Python language. The presented model and algorithm are quite universal and can be relatively simply adapted taking into account the specific features of the problem. A distinctive feature of the approach proposed in the article, for example in comparison with neural network models, is a decrease in the degree of subjectivity in the choice of the control rules. This degree is determined here not by the function of the corresponding fuzzy measure, but by the weight coefficients of the significance of crisis management options and the real resources for their implementation. 

 An effective method for preventing the operation of computer network nodes for organizing a botnet is proposed. A botnet is a collection of devices connected via the Internet for the purpose of organizing DDoS attacks, stealing data, sending spam and other malicious actions. The described method implies the detection of generated domain names in DNS queries using a neural network with parallel organization of convolutional and bidirectional recurrent layers. The effectiveness of the method is based on the assumption that generated domain names are used to create a botnet for merging. Experiments confirm that the proposed neural network is superior to the accuracy of existing counterparts on the UMUDGA dataset. The estimation of the quality of recognition of generated domain names using ROC analysis is calculated for a trained neural network. The article also formulates a model for controlling detectors using a partially observable Markov decisionmaking process to block infected nodes of a computer network. The search for the optimal policy for the formulated model by means of Q-learning of value agents is proposed. A comparative analysis of the average, minimum and maximum value of actions taken by agents in the process of interacting with the environment is carried out.

А further development of the radial klynoorotron idea – klynotron with symmetric conical radial corrugated resonator mirrors, is presented in the article. Strong coupling volume and surface resonance fields in the double conical mirrors in such a device is formed due to which the synchronous harmonic field is in the entire intermirror space. All saying above makes it possible to use a wide electronic flow. The conical mirror geometry provides a klynotron effect. As a result, not only the permissible device power is increased, but also its efficiency in comparison with a conventional radial klynoorotron. The article presents the calculating results of the Goratron at b0 = 0.51. The solution of the two-dimensional boundary value problem for the potential
V(r, z) = rBj(r, z), which determines Goratron resonator axisymmetric oscillation Em01, was carried out by standard packages for solving general partial differential equations using finite elements. The distribution analysis Er(r, z), Ez(r, z), Bj(r, z) shows that the field periodic component exists in the entire space between the comb mirrors. Given feature allows to use a wide (up to l/4) electron flow. Goratron electron flow model
contains 16 layers along z, the equations of motion were relativistic. The electronic efficiency averaged over all layers is more than 30 %, which is 1.5 times higher than that obtained in the radial klynotron efficiency calculations.