The assumptions of mathematical models for calculating the crack resistance of reinforced concrete structures are considered. For each of them, an analysis was carried out to determine whether they correspond to reality throughout the entire life cycle of the structure: from the hardening of the concrete mix to destruction. Based on the results of the analysis, it was proposed to use only one single calculation at the level of standards to assess the crack resistance of structures - according to the crack opening width, acrc. So, for example, at a certain value of acrc, the structure will still remain airtight (the cracks will be non-through), and if this value is exceeded, it will not. At the same time, the calculations already available in the norms for limiting permeability and the safety of reinforcement will still remain in demand. At the junction of the theory of damage accumulation and nonlinear fracture mechanics, a compressed algorithm is proposed for possibly taking into account the influence of cracks at all scale levels of the concrete structure, the key for which is the normalization of the statistical parameters of the distribution of discontinuities by diameters, lengths, openings, depths, directions, distances between discontinuities, etc.

Keywords: reinforced concrete, crack resistance, cracking moment, crack width, plasticity coefficient, damageability, non-linear fracture mechanics

The article studies the relevance of online tutoring, considers various existing systems for organizing online tutoring, identifies their strengths and weaknesses, and identifies the most relevant functions of the considered services. The design of the architecture of the developed software product is considered. The goals for further research are defined.

Keywords: online tutoring, tutor, online learning, design patterns, application architecture, information system

This article describes methods for measuring the characteristics of drinking water using microwave technologies, provides their comparative characteristics, advantages and disadvantages. The advantages of research by resonance methods are shown, the prospects for their application for further research are shown. Dielectric constant of substances, its influence on resonance.

Keywords: microwave technologies, resonant and non-resonant methods, water purification, drinking tests, dielectric constant

In this paper, based on Russian and foreign experience in mathematical modeling of photovoltaic installations, the authors consider the approaches to the construction of these models. The relevance of the research is confirmed by the wide spread of electric energy sources using solar energy. The scheme of photovoltaic element substitution and the dependences describing the processes occurring in it are given. The authors conclude that despite the large number of various mathematical models of photovoltaic elements, all of them can be grouped into two categories. The first category includes models that consider photovoltaic panels as a separate element, and the second category includes models where the photovoltaic panel is a component of a generating complex. Despite the difference in the analyzed approaches, the authors single out a number of parameters that characterize the operation of a photovoltaic panel and are sufficient to obtain simulation results with the required accuracy.

Keywords: photovoltaic panel, mathematical modeling, substitution scheme, distributed generation, power generation

The article discusses the features of the use and applicability of identification of parameters of the equivalent circuit of an submersible electric motors. The possibilities of technical implementation with a given accuracy are evaluated for definition the parameters of submersible electric motors substitution circuits under various external influences, as well as when designing submersible electric motors as an integral part of the electro-technical complex of electrical submersible pump units.

Keywords: submersible electric motor, electrical submersible pump unit, identification of parameters of the equivalent circuit of an asynchronous electric machine, mathematic simulation, crude oil production

The application of the gas-dynamic method with the use of nonlinear dynamics to the calculation of an underground structure built into the lower floor on the impact of an air shock wave is considered, taking into account the collapse of the above-ground part of the building. It is known that one of the impacts on built-in underground structures designed to protect the population and territory from natural and man-made emergencies is the impact of a possible collapse or blockage from a higher building when exposed to an air shock wave. This task is relevant because the current methods are based on linear static calculation methods and involve certain assumptions, including when calculating for collapse, and all this can lead to difficult to estimate errors in the calculation results. Therefore, when solving these problems, which are highly non-linear and the processes under consideration themselves are fast, it is necessary to consider the use of more adequate and accurate methods based on more rigorous formulations, which is the gas-dynamic method using nonlinear dynamics.

Keywords: emergency explosive effects, air shock wave, impulse effects, non-linear gas dynamics, compression phase, rarefaction phase, underground structures, “Ambient” elements, Eulerian grids, progressive collapse, collapse of structures, destruction of structure

The testing of technique for modeling the local atomic structure and X-ray absorption spectra for zinc ions in an aqueous solution in the presence of arachidic acid has been adjusted. Models of the local structure of zinc with different coordination geometries are considered: planar, pyramidal, tetrahedral, and octahedral. The cases of increasing distances between the zinc ion and water molecules in the plane and in the axial direction are simulated for octahedral coordination. It has been established that the most probable change in the local structure of the zinc environment in solution in the presence of arachidic acid is the removal of water molecules from zinc ions in the axial position and their further replacement with the formation of a bond with the carboxyl group of arachidic acid.

Keywords: arachidic acid, lipid layer, local atomic structure, X-ray absorption spectroscopy, total external reflection, zinc, biomembrane, finite difference method, monolayer

Pipe fittings, which are one of the main elements of any type of pipeline networks, can be used for various purposes: shut-off, reverse, safety, control, separating, shutting off, etc. In order to control the performance of this element, it is necessary to carry out various tests in the prescribed manner, the main ones being pneumatic. This study is devoted to the development of equipment for in-plant pneumatic testing of rotary check valves for pipeline systems of hazardous production facilities with ultra-high parameters of the working environment. For this design of the installation, the simulation of the stress-strain state of the elements of the installation was carried out, as well as the gas-dynamic calculation of the test circuit of the installation.

Keywords: rotary check valve, pipeline fittings, pipeline system, mathematical modeling, finite element method, strength analysis, stress-strain state, computational fluid dynamics, pneumatic testing, technological pneumatic installation

This article presents the results of the study, the impact of recreation on a person, the functions of recreation are presented and studied, classifications are proposed and, taking this into account, the types of recreational activities are derived.

Keywords: industrial buildings, interior space, architecture, recreational areas, interior gardening, architectural forms

Currently, Russian Railways (RZD) is characterized by an increase in the weight of trains, an expansion of the fleet of sections with high-speed movement of electric rolling stock. All this leads to the complication of the modes of operation of the power supply system, increased responsibility and possible damage from the downtime of trains. Of particular importance are the monitoring systems of the contact network, as an element of the power supply system that does not have a reserve. A significant number of Russian Railways sections are subject to the formation of ice and, as a result, possible serious operational risks and costs. One of the directions of minimizing the damage from the formation of ice and measures to eliminate it, according to the authors, is automation. The article provides an assessment of the possibility and directions of automating the fight against ice on the basis of ice detection systems at the early stages of education.

Keywords: power supply system, correct functioning, automation, ice detection system, contact network monitoring

The article discusses the features of international transport corridors passing through the territory of the countries of the Eurasian Economic Union, analyzes the potential and problems of their development, identifies their prospects for the implementation of large transport and logistics projects. Despite the great attention of scientists from different countries to the issues under study, the issues of the functioning of international transport corridors and their integration into the global transport system require further study.

Keywords: logistics, logistics directions, transport corridors, Eurasian Economic Union, transport routes

The importance of inert mineral additives for the development of modern concrete technology is considered. The results of a study of the influence of the dosage of limestone powder on the consistency and strength of fine-grained concrete with different ratios of its components are presented. It was established that in concretes with a high content of superplasticizer, the proportion of mineral additives in mixed cement is the main technological factor in controlling the strength characteristics of concrete.

Keywords: fine-grained concrete, mineral powder, inert mineral additive, superplasticizer, mix consistency, strength, strength control

The article highlights a number of problems that accompany the process of managing the property complex of the territory of the municipality. Issues related to the accounting and analysis of the state of objects of the property complex are considered. The need for systematic research is noted to justify decisions on the use of the city as a resource that provides a comfortable and safe space for life. Improving the process of managing the property complex is an urgent task for the development of cities around the world. An analysis of foreign experience indicates a common understanding of the criteria for the quality of the urban environment and the goals of the reorganization of urban space. When planning the development of urbanized territories, the peculiarities of the city, natural and climatic conditions are not always taken into account, which has a detrimental effect on the quality of the urban environment. It is shown that the effectiveness of the management of the property complex depends on the correct choice of the strategy for involving objects in the economic turnover, restoring their functional significance and ensuring environmental safety. To select effective solutions when solving issues of the use of the territory, it is proposed to use the method based on fuzzy sets, as the most optimal in conditions of high uncertainty and complexity of the processes under consideration.

Keywords: property complex management, decision-making methods, urban environment, urban space, natural and climatic conditions, urbanized territory, resources

The possibilities of using modern information technologies in teaching graphic disciplines in the conditions of the spread of coronavirus infection (COVID-19) are considered.

Keywords: engineering, graphic disciplines, COVID-19, information technology

The article describes the architectural techniques used in the process of developing case studies for assessing the professional skills of students, implemented as part of the educational process of the RSTU. The decision to use the interface as the center of architecture is justified. Possible problems in the process of developing the interface of the specified software are described, and ways of solving them are also presented. Thanks to the presented methods of building the project architecture, you can get rid of the main drawbacks associated with the dependence of the program code of the implemented product on the user interface. Increase the scalability and reliability of the application, while maintaining the overall quality and functionality.

Keywords: interface, user interface, architectural solution, loaded interface, software, pattern, messagebroker, coroutine, pseudo-stream, case