We have studied residual mechanical stresses of SiN_x films deposited on silicon substrates from a SiH₄-NH₃-He gaseous mixture in an inductively coupled plasma reactor at a deposition temperature of 150 °C. By varying the flow rate ratio of the reacting gases, the power of the plasma source and the pressure in the reaction chamber, it is possible to obtain SiN_x films with tensile or compressive residual stresses. The stress drift was estimated within four weeks after film deposition. It has been shown that for nitride films with residual stresses initially close to zero, an increase in the level of compressive stresses to (–300) MPa is observed during storage.

Excitation equations for longitudinal-azimuthally irregular waveguides are formulated taking into account losses in the walls. The inner surface of the waveguide walls is given by an arbitrary smooth function b(ϕ, z). The coordinate transformation method replaces the original cylindrical coordinate system r, ϕ, z with a new one ρ, ϕ, z, where ρ = r/(b(ϕ, z)). The new system defines the waveguide boundary as ρ = 1 = const, i. e. the waveguide geometry transforms as a regular cylinder. Taking these functions into account, the standard procedure of the incomplete Galerkin method is used to determine the amplitudes of partial waves. The resulting general equations can be used in the calculation and optimization of both microwave and EHF electronic devices of various types, as well as passive microwave devices of various applications.

The article discusses the development of the theory of the multidimensional matrices in the part regarding the symmetrical multidimensional matrices. The symmetry property is considered in terms of the structure of the multidimensional matrix. The so called kq-dimensional symmetrical matrices are considered along with the multidimensional symmetrical matrices, i. e. the matrices symmetrical to the multi-indices containing q indices. Unit, unit symmetrical and unit kq-symmetric matrices are considered. The matrices inverse to the multidimensional matrices with respect to the unit, unit symmetrical, and unit kq-symmetrical matrices are defined. It is proven that the matrices, inverse to the multidimensional matrices with respect to the unit symmetrical and unit kq-symmetrical matrices are the Moore–Penrose matrices. The distinct instances are given.

The developed model of a resistive-transistor thermoelectric converter, the technique for identifying its parameters and the results of circuit simulation using the proposed model of an RMS-DC converter are considered. The electrical circuit of the RMS-DC converter is given, the dependences of the conversion error on the input voltage level obtained by circuit modeling, on the basis of which the main requirements for reducing the error are formulated. The application of operational amplifiers of the OAmp11.2 type with input junction field-effect transistors, previously developed on the master slice array МН2ХА031, makes it possible to implement a precision RMS-DC converter in the form of a microassembly containing two crystals of the ПН001 thermoelectric converter, one МН2ХА031 crystal with a signal processing circuit and external filter capacitors. Circuit simulation showed that such a converter remains operational at an absorbed dose of gamma radiation equal to 1 Mrad and exposure to a neutron fluence of 1 ⋅ 1013 n/cm2 .

Experimental studies of nonlinear properties of low-power radio-frequency amplifiers similar to those used in 4G/5G mobile communication equipment of the FR1 frequency range are carried out. The measurements of the characteristics of the amplifiers are performed by using the double-frequency testing technique at frequencies of the n7 band (2500–2570 / 2620–2690 MHz), which is allocated in Belarus for 4G mobile communication systems, and the n78 band (3300–3800 MHz), which is planned to be used in Belarus for 5G mobile communications. Based on the results of the measurements of double-frequency characteristics of the amplifiers, their single-tone amplitude characteristics, as well as two-tone characteristics and values of the dynamic range of 3-, 5-, 7-, and 9th order intermodulation in the first harmonic zone, high-order polynomial models of transfer characteristics of the investigated amplifiers are synthesized. The synthesized models are suitable for use in a wide dynamic range of input signals in case of simultaneous modeling of nonlinear effects of all kinds that pose a danger to radio reception in a complex electromagnetic environment created in the frequency bands of mobile (cellular) communications: both “subtle” effects (intermodulation) and “rough” effects (desensitization, cross-modulation). When using the technology of discrete nonlinear analysis of the behavior of radio equipment in a complex electromagnetic environment, the obtained models provide high efficiency of simulation and quantitative analysis of nonlinear processes and radio interference occurring in 4G/5G/6G radio equipment and networks in a complex electromagnetic environment.

The research, described in the article, relates to the field of technical diagnostics – one of the components
of the process of repairing electronic equipment. The main reasons that influence the correct operation of radioelectronic equipment are identified, and the types of technical malfunctions that arise during its operation
are identified. The types of faults in printed circuit units have been identified and systematized, a classification
of methods for their diagnosis has been made, an algorithm for contactless monitoring of the performance of radioelectronic equipment elements has been developed, and a device structure for its implementation has been proposed.

The analytical dependence of the phases and values of intercomponent phase relations of the harmonic components of vibration displacement of misaligned shafts on their displacement has been presented in the article. Harmonic vibrations of the shafts were modeled using a Lagrangian connecting vibration displacement and forces acting in the system. For ease of derivation, the Lagrangian is rewritten in complex form. The resulting algebraic equations connect the complex amplitudes of vibration components with the amplitudes of periodic forces at the same frequencies and the parameters of the mechanical system (stiffness, damping). The amplitudes of periodic forces are related to the magnitude of the shafts angular and parallel misalignment according to the accepted model. Calculation of intercomponent phase relations values is used to get rid of the random initial phase shift caused by the choice of the timing reference. The magnitude of the effect produced by the misalignment of the shafts on the amplitudes and values of the intercomponent phase relations of the signal components is estimated. The obtained resultcan be used to construct devices for estimation shaft displacements and devices for assessing the condition of equipment based on the analysis of vibration signals.ls.

One of the methods for measuring the direction of arrival of an electromagnetic wave from a radio source by an automatic direction finder with a small antenna base and a limited number of channels of the radio receiving path is proposed. The problems that arise during the implementation of this method are listed, and suggestions for their solution are presented. A block diagram has been obtained and a layout of a radio direction finder has been created, in which the processing device is implemented using a two-channel LimeSDR transceiver. The results of the radio direction finder test for detecting and evaluating the direction of an unmanned aerial vehicle are presented.

Traffic management in modern intelligent transport systems includes monitoring the actual traffic situation in real time (volumes, speeds, incidents, etc.) and management or controlling transport traffic using this information. At the same time, cars as intelligent transport systems components must be equipped with communication capabilities for exchanging information with other vehicles (V2V) and with road infrastructure (V2I). All this is connected with the presence of special equipment connected to the on-board network for local data collection, which can be exchanged between cars and with a central communication station using wireless Internet. At the same time, the issue of developing the traffic organization algorithms themselves is still open. This problem can be solved with the help of game theory, a fairly new but rapidly developing part of modern mathematics. Unlike optimization theory, which studies the possibilities of constructing an optimal solution for the entire system as a whole, game theory studies ways to optimize individual benefits in competition with other persons (events) that rationally seek to satisfy their own benefits. The problem of “smart” regulation of intersections is quite difficult to solve, it combines the efforts of scientists from different fields of knowledge. However, the rapid development of ICT technologies and their rapid application to transport tasks makes it possible to develop some approaches to optimize the current situation at the intersection.

The article discusses the issue of controlling a four-wheeled mobile robot with omnidirectional wheels
of the mecanum type. An analysis of the rotational motion of the omnidirectional mecanum wheel was carried
out, based on its kinematics. For a specific robot with certain overall parameters, a graph of changes in the radius
of the mecanum wheel depending on the angle of its rotation was constructed. Kinematic and dynamic models
of a mobile four-wheeled robot have been compiled, taking into account its geometric characteristics. The presented expressions are a mathematical description of the behavior of a mobile robot in statics and dynamics. Based
on the obtained models, the principles of operation of the motion control system for a four-wheeled mobile robot
on omnidirectional wheels of the mecanum type are formed.

This article proposes the formalized methodology for model-based design of mobile platform management systems. The methodology is based on an alternative approach to development, when the model of controlled object is firstly created as a design tool, and then control algorithms are developed. This allows to find the most successful algorithms and select control parameters that are close to optimal in the process of model-based design. As examples, two typical tasks from the field of mobile platform management are given - braking and steering control. The proposed methodology has sufficient unification to be used in the design of control systems for mobile platforms of various types, with different positioning systems, principles of navigation and autopiloting.

Methods for modeling the interaction of electromagnetic radiation with a carbon nanostructured composite containing various structural elements, such as carbon fibers, nanoparticles, air gaps, and transition shells are considered. It is shown that for effective and adequate modeling of the interaction of electromagnetic radiation with a carbon nanostructured composite, it is necessary to create software due to the presence of a large set of input parameters, as well as the complexity of calculations. Functional requirements for the software are formulated, reflecting the choice of models and the presence of a convenient interactive interface. The architecture of the software that implements models of interaction of electromagnetic radiation with a carbon nanostructured composite is described, and the software implementation (class structure, methods, user interface) is considered. The developed code is based on proven physical and mathematical models, which make it possible to obtain results close to experimental data. The software architecture allows to effectively manage the modeling process, and also includes the ability to modify models and take into account new structural elements. An interactive interface for users has been developed that allows to easily manage the model parameters and analyze the results of numerical experiments.

The problem of compression of the dynamic range of infrared images is considered. To improve the quality of tone mapping of infrared images when their dynamic range is compressed and to simplify the control over the reproduction characteristics of infrared images, a dynamic range conversion algorithm based on adaptive histogram equalization with edge inversion is proposed. The essence of the algorithm consists in double reduction of the dynamic range of the infrared image with intermediate stretching, compression and overlapping of edges with inversion. To select the brightness interval and the degree of its stretching, the proposed algorithm uses the asymmetry coefficient. The algorithm makes it possible to improve some global and interval indicators of image reproduction quality by superimposing the edges of the histogram.

A developed mathematical model is presented for constructing a map of the location of areas that make up the background environment for optical-electronic systems. A feature of the proposed model is that when determining which class a particular pixel belongs to, the class values of neighboring pixels, as well as the spatial position of the pixel, are simultaneously taken into account. Quantitative assessments of the adequacy of this model and existing mathematical image models capable of constructing maps of the location of areas are given. The proposed model was compared with the Markov model, block Markov model, Gibbs model, block Gibbs model and doubly stochastic model with level quantization. Adequacy assessment was carried out using an artificial neural network developed by the authors, which evaluates the similarity of two images using a normalized similarity index ranging from 0.0 to 1.0, and its k-fold cross-validation. The comparison results showed that the developed model, according to the calculated indicator, is at least three times better than the known ones.