The problem of experimental research of the parameters of the propeller-motor group of an unmanned aerial vehicle (agrodrone) is considered. An analysis of the work performed by agrodrones in agriculture, as well as popular serial models of agrodrones produced by well-known global companies, including in the Republic of Belarus, has been carried out. A description of the design of the experimental stand, specially designed for testing the operation of the agrodrone power plant under conditions as close as possible to the real operating conditions in which the agrodrone has to operate, is given. The main structural elements of the test bench and measuring instruments that are used to conduct experimental studies of the operation of the propeller and its electric drive are described. The results of the research are presented in the form of quantitative values of the vibration parameters of the propeller-motor group of the agrodrone at given values of the input parameters of the electric drive control system, taking into account the influence of external factors. It is shown that the values of the parameters characterizing the vibrations of the propeller-motor group of the agrodrone can be different depending on the operating modes of the engines and changes in external conditions. Based on the results obtained, it was concluded that when formulating  the mathematical formulation of the modeling problem, it is necessary to take into account the influence of random factors  on the control system of the agrodrone, including vibrations caused by the operation of the agrodrone engines.

As an object of this study, the coatings were used, which are composed of self-fluxing nickel-based alloys or compositions containing them, formed in a hybrid technological process with two main stages: spraying by the plasma method and subsequent remelting – by the gas-flame method or laser heating. An experimental measurement of their resistance to abrasive wear under conditions of boundary friction with the introduction of lubricants has been carried out for the coatings obtained in this process. At the same time, the influence of the coating composition and the remelting method on the wear value measured by the artificial base method has been investigated. To evaluate the dynamics of structure formation in the surface layer subjected to mechanical loads during the friction, X-ray diffraction analysis, metallographic method, and scanning electron microscopy in the electron diffraction mode have been used. After the laser remelting stage, it is possible to obtain coatings with wear resistance that is twice or more superior to the level for sprayed coatings of the same composition processed by the gas flame method. Wear of the coating surface has been found to occur through the mechanism of fatigue failure of the least hard component of the coating, i. e., the nickel-containing intermetallic phase, with the formation of an island-type film of hard crystallites of the carbide-boron phase weakly bound to the coating base, which ultimately leads to cracking of particles of this phase and their crumbling from the surface. The durability of layers obtained after the laser remelting stage can be increased, according to experimental data, by reducing the grain size of the phases in the coating and its texturing, as well as increasing the concentration of alloying elements in the composition of the metal-containing binder phase of the coating. The use of alloying additives leads to an additional increase in wear resistance by 2–4 times. This is due, depending on the type of additives, with an increase in the amount of the hardening phase while maintaining the plasticity of the matrix (coatings with chromium carbide additives), the degree of alloying of the nickel matrix (by the tungsten carbide and boron carbide additives), as well as the presence of a finely dispersed carbide-boride component, which reduces the processes of deformation and scratching.

Elevators are potentially dangerous objects and, despite the fairly high safety of modern elevators, which is regulated by industrial safety rules, State Standards and manufacturer’s instructions, the requirements for elevators are constantly becoming more stringent. According to clause 5.6.1.1 (b) and clause 5.6.6 of GOST [All-Union State Standard] 33984.1–2016, it is required to prevent overspeeding when moving the cabin in both directions (up and down). To meet this requirement, elevators can be equipped with two single-acting speed limiters, one of which activates single-acting safety devices located on the car, and the second on the elevator counterweight. However, this solution leads to duplication of the safety system (in addition to two speed limiters and safety catches, two tensioners, two speed limiter ropes and a double number of limit switches are additionally required). This can only be justified in cases where there are used premises under the pit of the elevator shaft, for example an underground parking lot. This paper discusses elevator safety devices that meet the new requirements of modern domestic and foreign standards (EN 81–20:2014): double-acting safety devices and speed limiters, a system for preventing unintentional movement of the car (counterweight). Catchers and a speed limiter are interconnected devices that prevent the cabin (counterweight) from falling in the event of a break or when the supporting ropes are weakened, and also stop the cabin (counterweight) if the speed is unacceptable. However, as practice has shown, cases of uncontrolled upward movements of the elevator and while the elevator is parked with open doors are possible. This leads to accidents and injuries to passengers. The proposed designs of the limiter and catcher allow this to be avoided. Recommendations are proposed for modernizing old elevators, and, as a result, increasing their level of safety.

One of the types of finishing operations of machining the surface of products made of metal materials is hard turning, which is carried out at elevated turning modes. When processing steels hardened to high hardness, in processing modes with the ma-nifestation of all the features characterizing hard turning, a lot of heat is released, which turns into chips during turning, while the values of the cutting force decrease, which is associated with the softening of the active surface 

layers of the processed material and its subsequent plasticization, which leads to a decrease in cutting forces in the contact zone. A significant interest both from a scientific and practical point of view is the issue of changing the cutting temperature and processing parameters in hard turning modes. The paper presents experimental research results and empirical dependences of the radial component of the cutting force and temperature on cutting speed and feed per revolution, at a fixed cutting depth in the modes of hard turning of hardened steel. The research has been carried out on an experimental installation specially designed for this purpose, consisting of a lathe and a stand for recording, monitoring and analyzing dynamic processes (in the form of a signal from the cutter) during turning. A cutter with replaceable ceramic cutting plates was used as a test tool, and the material of the workpieces for the research was HVG steel, subjected to heat treatment for a hardness category of 55 HRC. Computer and mathematical processing of the results obtained using the least squares method was carried out, which allowed us to derive calculation formulas for determining the values of the studied factors. The optimal values of the factors corresponding to the minimum value of the radial component of the force and the cutting temperature are determined.

The paper describes a solution technique for direct and inverse problems of modeling the process of magnetic abrasive finishing (MAF) of semiconductor wafers. Solution of the direct problem enables calculation of allowance removal function for the prescribed machining parameters, and solution of the inverse problem enables determination of machining parameters required for realization of the prescribed allowance removal function.  The direct problem is solved by means  of Preston equation, which is usually used for description of material removal rate when polishing optical parts. The inverse problem is considered in a matrix formulation, and its least squares solution is determined by means of generalized inverse Moore-Penrose matrix. Based on the solution of the direct problem with constant values of kinematic and magnetic machining  parameters shows that MAF with constant values of machining parameters does not ensure uniformity of material removal.  On the basis of numerical examples it is shown that close to uniform material removal can be ensured by control of magnetic machining parameters with the law of variation determined from solution of the inverse problem. It is demonstrated that the smoothness of solution of the initial ill-conditioned inverse problem can be improved by means of Tikhonov’s regularization, which in turn technically simplifies control of machining parameters

The paper presents the research results of the influence of the electrical characteristics of a pulsed microwave magnetron power supply on the microwave discharge generation conditions, determined by the operating mode of the generating  system as a whole. Plasma was formed in a vacuumized reaction-discharge volume located inside a rectangular resonator chamber. Depending on the operating modes of the microwave magnetron power supply, studies have been conducted for three modes of microwave discharge plasma generation: pulsed mode with a duty factor S ≈ 2; pulsed mode with  a duty factor S ≈ 1.15; continuous mode. Probe measurements of the microwave power in the microwave discharge plasma volume and its local conductivity have been carried out. The paper presents  the dependence of the power of microwave energy in the central area of the reaction-discharge quartz  chamber of a microwave plasmotron on the amount of power consumed by the microwave magnetron, as well as the distribution of the electrical component of the microwave discharge plasma along the length and cross-sectional plane of the working volume. It has been established that for all studied modes of operation  of the power source, with an increase in the power consumption of the microwave generator system, an increase in the microwave power recorded in the central region of the plasma discharge is characteristic. The continuous generation mode is characterized by a decrease in the uneven distribution of electromagnetic energy along the axis of the discharge chamber.  It is shown that the transition from a pulsed to a continuous mode of microwave plasma discharge generation at the same level of power consumption by the generating system is characterized by a decrease in the value of the registered microwave power in the microwave discharge plasma volume and an increase in its local conductivity in particular areas of the reaction-discharge volume.

The problem of calculating a ring slab on piles on an elastic foundation is considered, provided that a part of the slab is in the same plane. A similar problem arises in practice when calculating the pile-slab foundation of chimneys of a thermal power plant. The calculation is performed using the method of B. N. Zhemochkin – a mixed method of structural mechanics, where the unknown forces in the cut connections of B. N. Zhemochkin at the contact of the slab and the elastic base, the linear and angular displacements of the introduced pinching on the slab, the springs that simulate the piles and the unknown forces that cause movement of part of the annular slab in one plane. The external vertical force and moment are considered as known. A system of linear algebraic equations has been formed in a general form to solve the problem. The results are obtained for a circular pile-slab foundation of a chimney. Graphs are presented of the distribution of contact stresses, displacements for several sections of the foundation slab, forces in piles and external loads that cause movement of a part of the slab in one plane. The results obtained can be included in the regulatory documents of the Republic of Belarus and the Russian Federation.

Artificial indoor ice rinks are complex and expensive engineering structures that are widely used for hosting various public and sports events, such as ice shows, hockey, figure skating, speed skating, etc. The presence of large audiences at all these events contributes to the widespread dissemination of information through various forms of advertising. As experience has shown, this primarily involves various banners and team logos placed within the ice surface. The latter obviously affects 

the temperature regime of the ice covering, as banners alter the heat transfer resistance of the ice layer. Furthermore, strict requirements for temperature field parameters on the ice surface are established for each type of event (by international federations of ice hockey, figure skating, speed skating, including international rules). To study the impact of advertising banners on the temperature regime of the ice surface, both natural experiments on a standard-size ice rink in a multifunctional sports arena for 15,000 spectators and numerical solutions of the heat conduction differential equation for ice with advertising banners were conducted. The research confirms that advertising banners on ice rinks have a significant impact on the temperature regime of the ice, which in turn affects the quality of the ice and the conditions for holding sports competitions. Adhering to recommendations regarding the choice of banner materials and colors, as well as effective management of the cooling system, can help minimize the negative consequences of banners on ice quality.

. Within the framework of ensuring the country's energy security and pursuing a policy of decarbonization of the economy in the Republic of Belarus, it is assumed to maximize the use of its own fuel and energy resources (TER). However, the question of choosing the type of heat source in centralized heat supply  systems when using local fuels (LF) remains open.  The commissioning of the Belarusian Nuclear Power Plant and the relatively high unit cost of power generation capacities running on LF inclines the scales to use boiler houses as heat sources. Based on the world experience in the development and application of heating as the most energy-efficient solution in the field of heat supply, this problem has been studied in the conditions of Belarus. It is shown that the electric capacity of mini-thermal power plants using traditional LF connected to the unified system of the country is less than 100 MW, and the main technologies implemented at mini-thermal power plants using LF in the Republic of Belarus are traditional steam power plants with water steam as the working fluid (11 power plants) and steam power plant with organic Rankine cycle (ORC) (3 power plants). Geographically, mini- thermal power plants operating on LF are located evenly throughout the entire territory of the Republic of Belarus. The number of hours of use of the installed capacity of renewable energy sources (RES) of the Republic of Belarus has been determined. Energy sources based on organic waste and biomass (over 4,000 hours per year) and on hydro resources (about 3,500 hours per year) have a clear advantage, for which indicator of the number of hours of installed capacity use is much higher than for solar and wind power installations. In addition, biomass generating capacities have the lowest coefficient of electricity supply to the combined  energy system. Based on the analysis of modern trends in the development of energy, technical and economic “attractiveness factors” for the construction of heating systems for heat supply on LF in the conditions of Belarus have been formulated, which, in addition to traditional factors (substitution of imported fuel – natural gas and oil), include improvement of the quality and reliability of energy supply to consumers in remote locations, development of polygeneration, reduction of losses  of electric energy for its transport, participation in covering the electric load schedule of the unified power system, and also indicated the possibility of creating an energy hub on the basis of a mini-thermal power plant, structured for the integration  of energy sub-sectors, distributed generation sources and the option of generating “green” energy carriers.

One of the most widespread technical systems in the world is underground steel pipeline communications (heat pipelines, main and distribution oil and gas pipelines, etc.). Accordingly, reliability assessment of such technical systems and their components is of great theoretical and practical interest. At the modern level of development, reliability calculation has become a mandatory stage in the design and diagnostics (during operation) of any technical systems in ge-neral, and in particular pipeline systems. A reliable calculation, either explicitly or implicitly,  is always based on the model of the object being calculated. It is the adequacy of the model to the real physical relations and processes inside the technical object that determines the accuracy and practical value of calculation methods. It is proposed to consider a single linear section of an underground steel pipeline as a complex technical system of unequal elements from the point of view of reliability – the main element (steel pipe) and auxiliary  protective elements combined into subsystems (blocks). The algorithm for calculating  the reliability of the object is based on the method of  block diagrams, taking into account the influence of the aftereffect  of the failure of an auxiliary element (elements) on the reliability parameters of the main element, which more adequately reflects the specific features of the design and operation of steel pipelines compared with the applied static models. The variants of structural design of a steel underground gas pipeline with a protective insulation coating and with complex corrosion protection (insulation and electrochemical protection) are considered, for which refined formulas are obtained for calculating the main reliability (failure-free) indicators.