Objective. The purpose of the study is to illuminate the obtained experimental research data, measurement technique, as well as the design of a la-laboratory bench for full-scale tests of thermoelectric system (TES) for uneven cooling of electronic boards.

Method. The article describes the experimental set-up and measurement procedure of laboratory thermoelectric system for electronic circuit boards cooling. The experimental stand is made on the basis of the measuring equipment of the laboratory of semiconductor thermoelectric devices and devices of Daghestan State Technical University.

Result. We obtained plots of time dependences of temperature changes in thermoelectric system checkpoints at different thermoelectric battery (TEB) supply currents. Determined were the temperature dependences of the thermoelectric elements of the electronic board simulator at their non-uniform cooling on the parameters of FEB and working substance as well as the time variation of the temperature of the shell of the vessel with the working agent.

Conclusion. As a result of full-scale tests of the device it was found that the use of a cooling system reduces the temperature of heat-generating elements to acceptable values. In particular, the temperature of heat sources decreases to 345 K and 344 K (from 428 K and 396 K) if the total heat-generating power of the electronic board is 120 W. At the same time, the temperature background created by the heat-generating elements in the nearby areas of the electronic board simulator also decreases. The discrepancy between the results of calculations carried out beforehand and the experiment was estimated to be 8%.

Objective. The aim of the study was to determine the dependence of the distributions of average integral hydraulic resistances and convective heat transfer in turbulent flow in pipes with small (short channel) and large (long channel) sequences of semicircular periodic protrusions based on numerical solutions of the Reynolds equation systems, closed using Menter's shear stress transfer models, and energy equations on a multi-scale intersecting structured grid.

Method. The calculation technique based on finite volume solutions of the Reynolds equation, closed using the Menter shear stress transfer model and the energy equation on a multi-scale intersecting structured grid, made it possible, with acceptable errors, to calculate the average coefficients of hydraulic resistance and heat transfer in a pipe with different quantities annular semicircular ledges.

Result. Analytical comparisons were made of the calculated ratios for relative heat transfer and hydraulic resistance on the number of protrusions in channels with different values of relative heights of turbulators h/D, relative steps between turbulators t/D, different values of the Reynolds criteria Re, with other equivalent parameters, which showed that in in which case the qualitative deviations of the above characteristics are carried out monotonously, and in which case they are accompanied by extrema or inflections, and also showed cases of qualitative changes in the calculated characteristics. With the transition from 30 protrusions to 50, as a rule, only quantitative differences occur for the relative parameters of hydraulic resistance and heat transfer, and their qualitative changes are insignificant; with a further transition from 50 protrusions to 100, their quantitative changes also become insignificant.

Conclusion. The nature of the patterns of distributions of the mean integral characteristics of flows and heat transfer for a channel with protrusions of various numbers must be taken into account for a short channel. An analysis of the calculated information obtained showed that when moving from a short channel with turbulators to a long one, most often, there is an increase in relative heat transfer and a decrease in relative hydraulic resistance, which justifies the advantage, from the point of view of intensification, of heat transfer by turbulence of the flow of the last channels in relation to the first channels.

Objective. The aim of the study is to modernize the design of the exhaust system of gas turbine engines (GTE) in order to reduce aerodynamic losses using numerical methods (CFD methods) for simulating the flow of exhaust gases.

Method. The directions of modernization were chosen by considering the pattern of the flow of exhaust gases (separated flow zones and vortex flows) in the exhaust system during numerical modeling (Computational Fluid Dynamics). The modernization of the exhaust system consists in profiling the axial diffuser and changing the design of the gas collector.

Result. The profiling of the axial diffuser was performed using numerical simulation methods. The design of the gas collector was changed based on the technical solution proposed by V.B. Yavkin. Numerical simulation of the flow of exhaust gases in the modernized exhaust device was performed. To evaluate the results of modernization in numerical models of the modernized design and prototype, the values of aerodynamic losses at the outlet of the axial diffuser and gas collector were determined.

Conclusion. CFD modeling made it possible to obtain data on the structure of the exhaust gas flow in the upgraded exhaust system, to see the pattern of the distribution of velocities and pressures. The results of the numerical experiment showed a decrease in pressure losses in the exhaust system by 11% relative to the prototype.

Objective. The aim of the study is to build finite-difference models that can be used to test the bending vibrations of a rod under various fastening conditions, solving the problem in the frequency or time domain.

Method. The study is based on the application of the finite difference method and the finite element method.

Result. The necessity of application is substantiated and the technique of mathematical modeling is proposed for the design engineering of radio-electronic means operating under conditions of dynamic external influences. The significance of the use of discrete models and the peculiarities of their creation for studying the dynamics of certain constructs of electronic equipment are analyzed. The concept of studying simple models of bar structures for the analysis and verification of the theoretical positions of constructing models of structures is proposed. The features in the development of models for the calculation of natural shapes and frequencies of bending vibrations of rods are shown.

Conclusion. Assessment of vibration strength and vibration resistance of non-stationary structures of radio-electronic means is possible by methods and means of mathematical modeling used as test models to test various hypotheses and theoretical positions in the study of the dynamics of complex structures and the design of radio-electronic means.

Objective. Formulate the general principles for the construction and operation of an integrated electronic document management system, as well as list the possibilities of document management automation.

Method. The article is based on methods of working with electronic documents, methods of searching, processing and storing information, methods of automating various office functions.

Result. The potential advantages of electronic document management systems are identified, which are the improvement of documentary support for intra-organizational and external communications in order to improve the regulation and coordination of operational activities, mutual agreement and adjustment of management decisions.

Conclusion. The widespread use of electronic document management systems will make it possible to distribute their functional content as an information environment for management, control and collective interaction. There are specifics of electronic documents, especially in terms of legal force, validity, storage methods, use of open forms and recording standards for the exchange of electronic documents. At the same time, the legal justification for certifying the authenticity of electronic documents using an electronic digital signature or using a system of contracts between participants in an electronic exchange is of great importance. Electronic documents have a physical and logical structure that do not coincide with previous ideas about a document as a rigid, unchanging structure of information and its carrier.

Objective. The aim of the study is to build and optimize a computer model of the antenna using software packages for electrodynamic modeling.

Method. The study is based on dynamic modeling methods.

Result. In this paper, the dependences of the width of the radiation pattern on the curved Vivaldi antenna with a mirror arrangement of the petals are obtained. Graphs of the dependence of the radii of curved petals and aperture values on the width of the radiation pattern in two planes for frequencies of 3 and 24 GHz are plotted. Curve radius, antenna aperture and lower antenna height are plotted as functions of the maximum beamwidth for 24 GHz and the minimum beamwidth for 3 GHz. The obtained dependencies were approximated for two planes θ = 900 (antenna aperture plane) and φ = 00 (plane perpendicular to the antenna aperture plane). By means of regression analy sis, analytical descriptions and graphs of dependences of the maximum beamwidth for 24 GHz and the minimum beamwidth for 3 GHz, on the radii of the curves, aperture and the height of the lower curve of the antenna lobe were obtained.

Conclusion. The resulting mathematical model makes it possible to obtain the values of the radius of the curve, the opening and the lower height of the antenna lobes for different frequencies, as a result, to build a Vivaldi antenna with the desired topology.

Objective. The aim of the study is to solve the problems of constructing logicallinguistic (fuzzy) models for controlling the trajectory movement of complex dynamic objects.

Method. To build logical-linguistic (fuzzy) control models, theories of fuzzy sets and algorithms of L. Zadeh were used.

Result. The process of constructing logical-linguistic (fuzzy) models for controlling the trajectory movement of complex dynamic objects using the theory of fuzzy sets and fuzzy algorithms is given. A marine mobile object (MMO) operating in an uncertain environment was used as a control object in the work. It is shown that logical-linguistic (fuzzy) MPO control models can be built taking into account the rich practical experience of a navigator who does not have special knowledge, expressed by them in a qualitative form for building fuzzy control models.

Conclusion. Logicallinguistic control models make it possible to ensure the movement of a marine moving object along a given trajectory with a quality of the controlled process sufficient for practical purposes under conditions of various external disturbances and drift of the parameters of the controlled object. The use of fuzzy control algorithms can significantly reduce the cost of computer time compared to the optimal search algorithm with an acceptable deterioration in the quality of the process and ensure the implementation of the control process in real time.

Objective. The purpose of the study is to determine the coordinates of the earthquake hypocenter with the simultaneous determination of the seismic wave velocity.

Method. The study is based on the use of figures of the fourth and second order - the Cassini oval and hyperbola, figures of the second order - ellipse and hyperbola and combined methods that allow, at given seismic wave velocities, according to three seismic sensors, to determine the coordinates of the earthquake hypocenter. In this case, the velocities are assumed to be known a priori. According to the readings of the fourth seismic sensor, and for given seismic wave velocities, the distance from the fourth seismic sensor to the hypocenter is determined. Again, according to the coordinates of the fourth seismic sensor and the hypocenter coordinates calculated from the three seismic sensors, the distance between them is calculated. If the seismic wave velocities do not correspond to the true ones, a discrepancy will appear between the two calculated values of the distances from the hypocenter to the fourth seismic sensor. By varying the velocities of seismic waves when calculating the coordinates of the hypocenter, we achieve a minimum discrepancy.

Result. The problem of determining the coordinates of the earthquake hypocenter with the simultaneous determination of seismic wave velocities is solved. The error distribution densities in determining the coordinates of the earthquake hypocenter and seismic wave velocities are obtained.

Conclusion. The proposed method makes it possible to increase the accuracy of determining the coordinates of the earthquake source, as well as to refine the values of seismic wave velocities.

Objective. The article substantiates the need for digital simulation of emergency impact in the study of the stability of a building to progressive collapse by creating a simulator of local destruction.

Method. To ensure the unique architectural appearance of the projected multifunctional high-rise complex, a complex shape has been developed with recesses in which elevator shafts are located. The principle of control of the structure due to the influx of external energy is observed. Energy conversion and the necessary protection is provided by the presence in the spatial frame of the building of balancing connections near architectural recesses, which allow stabilizing the state of a complex system. The spatial rigidity of the structural scheme of a high-rise building is ensured by the use of symmetrically located diaphragms and stiffening cores, rigid nodes for interfacing with the supporting structures of outrigger systems.

Result. The calculation algorithm for progressive collapse includes the calculation of the stress-strain state of the building frame elements during normal operation. An analogue of the emergency action is created by excluding from the design model the bearing element, the instantaneous removal of which is modeled by a force with the opposite sign, determined by the results of the calculation in the normal operation stage.

Conclusion. The stress-strain state of the frame, which occurs during local destruction, is a criterion for resistance to progressive collapse. The question of the need and the established form of outrigger floors in relation to a specific building has been investigated. The dependence of the dynamic characteristics when changing the structural solutions of the frame of a unique building is given.

Objective. The purpose of this work is to develop a methodology for an objective assessment of the environmental safety of construction sites and development areas.

Method. The study is based on a conceptual approach to assessing the environmental safety of construction sites and territories.

Result. A methodology for assessing the environmental safety of construction objects is proposed; the criteria for assessing the development area are determined; methods for solving the problems of development of territories and their environmental safety are proposed. As a method of assessment, the coefficient "degree of real estate concentration" was developed and adopted. The concepts of "environmental reserve", "threshold of environmental safety", "sustainable state range" are introduced, which makes it possible to reliably assess the possibilities of territories for the placement of construction objects with different technogenic potential.

Conclusion. It is necessary to legislate, as a mandatory procedure, the procedure for assessing the “degree of concentration of real estate” in administrative territories, especially when planning the construction of a housing stock under the renovation program, when allocating land for new construction, when assessing the environmental impact in the design and examination of construction projects.

Objective. The aim of the study is to identify metallic impurities in fine dust (PM_2.5) in the residential area of Srednyaya Akhtuba (Sredneakhtubinsky rayon, Volgogradskaya oblast) exposed to the anthropogenic factor (expanded clay production) in a comparative characteristic with a relatively clean zone (garden non-profit partnership (SNT)) by indicators the number of particles (NPM_2.5, %) and their mass fraction (D (dPM_2.5), %).

Method. The selection of particles (PM_2.5) from the leaves of apricot trees and the preparation of aerosol suspensions was carried out according to international methods. The identification of the number and mass fraction of particles was carried out on the basis of the optical method according to GOST R 56929-2016.

Result. The obtained values for the studied parameters were checked by the Wilcoxon T-test and were found at a significance level of p <0.05. In the residential area of Srednyaya Akhtuba, 35 times the mass fraction (D (dPM_2.5), % of particles (PM_2.5) exceeded the conditionally clean zone) and a slight increase in the number of particles (2 times) were found.

Conclusion. Based on the results obtained metal impurities in fine dust (PM_2.5) in the residential area of Srednyaya Akhtuba and environmental risks for the population living there are predicted. It is necessary to improve the system of protection of the urban economy at the enterprises for the production of expanded clay, etc., located in the industrial zone of Srednyaya Akhtuba.

Objective. Development of a method for calculating the bearing capacity of twolayer reinforced cement shells for force and temperature effects in a fire. These structures consist of a fire-retardant layer made of vermiculite concrete, as well as a carrier layer of fine-grained concrete reinforced with mesh.

Method. The solution is carried out in a physically nonlinear formulation using the deformation theory of concrete plasticity by G.A. Geniev. In obtaining the resolving equations, the theory of shallow shells by V.Z. Vlasov is used. The physically nonlinear problem reduces to the sequential solution of elastic problems for a structure whose physicomechanical parameters are functions of the x, y, z coordinates. The solution is carried out by the finite element method in combination with the Newton-Raphson method. The dependence of the characteristics of construction materials on temperature is taken into account. The temperature field is assumed to be a function of only one z coordinate, and the finite difference method is used to determine it.

Result. the results of numerical simulation of full-scale experiments in a fire chamber for single-layer and two-layer shells are presented. Some deviations are revealed, caused on the one hand by inaccuracies of the experiment and errors of the theory on the other hand.

Conclusion. A significant influence of the boundary conditions on the process of deformation of the structure was found. When the support contour was fixed along x and y, a shell bend up was observed, which was consistent with experimental data, and in the case of a freely sliding support contour, the structural points moved exclusively downward. In general, the agreement between the results and experimental data is quite good, which allows us to use the methodology for calculating real structures.

Objective. The purpose of this study is to substantiate the methodology for static calculation of light coatings for large-span structures with lenticular membrane-pneumatic lenses, including racks at individual points of the span, using the step-iterative method of parameter increments.

Method. The study involves the phased application of the finite element method (FEM), the universal equation of state of gas and the improved Euler-Cauchy numerical procedure, taking into account the geometric nonlinearity of systems and the physical nonlinearity of the elastic work of air in lenses and taking into account the aftereffect of excess air pressure.

Result. A comparison is made in terms of rigidity and load-bearing capacity of membrane-pneumatic lenses, reinforced with individual posts, with the corresponding flexible membrane-pneumatic lenses of the classical type.

Conclusion. In the presence of racks, the effect of a significant increase in the rigidity and bearing capacity of lenticular membrane-pneumatic systems is observed for large spans. The distance between the posts along the building can be adjusted during the design and thereby regulate the effect of strengthening the system. The maximum deflections of the lenticular-shaped membrane-pneumatic system reinforced with struts are much less than the maximum deflections of the lenticular membrane-pneumatic system of the classical type under the action of the calculated snow load of the first and second limit states.

Objective. The aim of the study is to find rational ways to change the total energy consumption spent on cement production in terms of 1 m3 of concrete.

Method. To obtain reliable data, experimental and laboratory methods for testing cement were used.

Result. Tests have shown that at constant concrete strength, the consumption of cement per 1 m³ of concrete decreases with an increase in the specific surface of the binder, especially significantly in the case of Portland slag cement. The calculation results show that with an increase in the specific surface area of cements, the total energy consumption for their production, referred to 1 m³ of concrete of the same strength, decreases, and most significantly with an increase in the specific surface area of cements from 300 to 400 m² /kg and less from 400 to 500 m² /kg.

Conclusion. To reduce the energy intensity of concrete, it is necessary to use cements ground much thinner than they are ground at cement plants in open-type mills, despite the increase in energy consumption. Cements with high fineness of grinding can reduce the cycle of heat and moisture treatment of concrete products. Reducing the cycle allows to increase the turnover of molds and labor productivity at precast concrete plants, as well as further reduce energy consumption for the production of prefabricated reinforced concrete structures.

Objective. The targets of modern construction require the search and development of new efficient technologies. The main trend in building architecture is the creation of spectacular (buildings-symbols, objects of competitions of countries) objects and structures that attract the attention of people and add to the list of unique attractions. To implement such projects, it is necessary to introduce high-tech advanced techniques, which is the electrostatic method of manufacturing fiberreinforced concrete.

Method. The paper considers a new method of forming products and structures from fiber-reinforced concrete using electrostatics. An important place in the method is occupied by the physics of interfacial phenomena, namely wetting and capillary effects. The electrostatic deposition of layers of dry concrete mixture on the shaping frame occurs with the help of electrostatic sprayers.

Result. This method allows saving cement, due to the use of a water-cement ratio close to the theoretical value. The issue of compaction of applied layers of dry concrete mix due to wetting with water with surface-active additives is discussed. In this regard, the kinetics of filling through and dead-end capillaries with water and other aspects of the new technology are considered. A hydrophilic binder has been developed using calcium lignosulfonate additive, which makes it possible to demonstrate the effectiveness of the electrostatic method in the future.

Conclusion. The processes of wetting and the kinetics of liquid filling capillaries and channels of various shapes between the particles of the dry concrete mixture, as well as the compaction of the powder system as a result of moisture, will make it possible to realize difficult and unique projects in reality. The developed hydrophilic cement based on the surface-active additive LST (0.25%) contributes to the effect of interfacial electrostatic adhesion, thereby improving the properties of fiber-reinforced concrete.

Objective. Cementing oil and gas wells at a sufficiently large depth and at high temperatures is a rather complex and energy-intensive process that requires the use of special cement. The review material on oil well cements confirms the responsibility of choosing this binder, which can guarantee the safe process of drilling, plugging and operating oil wells. The classification of well cement is given, because it is known that when cementing free space in a well, specialists face various difficulties associated with temperature changes, density differences in the earth's crust.

Method. The studies were carried out in accordance with the normative documents GOST 310.3-76 Cements. Methods for determining normal density, setting time and uniformity of volume change; GOST 1581- 2019 Oil-well portland cements. Specifications; GOST 310.4-81 Cements. Methods for determining the ultimate strength in bending and compression.

Result. The properties of grouting cement PCT-I100 were studied, to slow down the setting of the mortar mixture for 10-14 hours, additives "Sulfatsel" and "NTF" retarders were introduced into the binder system with mixing water. The research results showed that the use of retardant additives slowed down the hardening of the system in the first 10 hours, but after setting, the cement stone quickly gained the missing strength. The water demand of oil well cement is quite high 33–35%, which is mandatory for obtaining a mobile mortar mixture, taking into account its injection by pumps into the space of an oil well

Conclusion. The purpose of grouting cement confirms the responsibility and importance of selecting a binder for plugging wells and is determined by various factors, in particular, hydrogeological conditions, temperature, groundwater level in the layers of the earth's crust.

Objective. The aim of the study is to evaluate the effectiveness of trussed beams with two posts.

Method. Many numerical examples are carried out and variant design of trussed beams with various structural characteristics is carried out. Appropriate tables are compiled.

Result. The analysis of the influence of various design parameters on the own weight and the cost of the metal of a trussed beam with two posts was carried out. Various tables have been compiled that show the effectiveness of a trussed beam with optimal characteristics. The constructed tables allow us to draw a conclusion about the effectiveness of the optimal parameters of trussed beams with two posts.

Conclusion. The proposed technique and algorithm testify to the effectiveness of the considered design. Saving steel, as well as reducing the cost of metal of trussed beams with two posts compared to conventional beams, reaches 40-50%.