The study is devoted to the generalization of the existing world experience on the impact of recycled polyethylene terephthalate (PET) products when they are added to concrete on its characteristics. Analysis of the available data shows the effectiveness of the use of PET fiber in a concrete matrix in order to recycle plastic waste, facilitate concrete structures, save cement consumption and improve the strength characteristics of concrete. But the researchers did not come to a consensus on the effective consumption of fiber during reinforcement, the influence of the shape of the fibers used on the properties of fiber concrete, as well as the areas of application of this material.

Keywords: concrete, concrete matrix, fiber, dispersed reinforcement, polyethylene terephthalate, tensile strength, compressive strength

This article contains the results of a study of the strength characteristics of building mortars of various compositions based on magnesia binder (magnesia oxychloride cement). The results obtained: the final compressive strength (28-day) within the studied compositions is from 12 to 45 MPa, the kinetics (rate) of strength growth on the first day of hardening is from 22 to 38%, on the third day of hardening – 33-68%, on the seventh day – from 50-88%, and about 120% from the design (28-day) with further hardening.

Keywords: magnesia oxychloride cement, magnesia binder, magnesia mortar, magnesia concrete, caustic magnesite, magnesium chloride, compressive strength, strength set kinetics

A periodic semiconductor structure is considered, consisting of tunnel-uncoupled quantum wires (QW) based on InSb containing impurity centers. The uniform magnetic field is directed along the QW axis. For the case of light polarization transverse with respect to the QW axis in the framework of the dipole approximation, in the effective mass approximation, an analytical expression for the impurity absorption coefficient of light is obtained taking into account the dispersion of the QW radius described by the Gauss function. It is shown that on the spectral curve constructed in the Maple program, for given parameters of the QW and the semiconductor structure, there is a sequence of resonant maxima with a doublet structure. The cyclotron frequency determines the distance between the maxima in the doublet, and the frequency of the doublets on the spectral curve is determined by the hybrid frequency. With an increase in the magnetic field, the dynamics of the edge of the impurity absorption band is observed, which can be used to create detectors of optical radiation in a wide range of wavelengths and will make it possible to identify such semiconductor structures. It is also possible to obtain valuable information about the parameters of the QW and the band structure of the semiconductor from the spectral curve

Keywords: impurity absorption coefficient, quantum wire, low-dimensional semiconductor structures, impurity center

The paper studies the problems of heat transfer intensification in shell-and-tube heat exchangers used in the heat supply of buildings. The solution to this problem is to use the circulation of the coolant flow in a pulsed mode, with different frequency pulsations. Based on experimental studies to determine the efficiency of a shell-and-tube water-to-water heat exchanger, a method has been proposed, in accordance with which it has been proved that the pulsed mode, compared to the stationary one, is the most effective in terms of key indicators, such as the heat transfer coefficient and thermal power.

Keywords: intensification, heat transfer, heat exchanger, coolant, fluctuations, efficiency, thermal power

The article presents the results of computational studies that are part of the authors' comprehensive research on the development of a methodology for predicting the resistance of steel fiber concrete to thermal effects at NPP facilities with various parameters of dispersed reinforcement. The studies were carried out using selected models to describe the processes of thermal deformations and changes in the most important properties of steel fiber based on previously obtained experimental and calculated data on thermal changes of steel fiber on an optimized cement-sand matrix with five types of steel fiber with a volume content of 0.5% to 6% after heating at 110-1100 oC. Based on calculations in accordance with the accepted hypothesis and the selected models, the dependences of thermal changes in the properties of steel fiber concrete relative to matrix changes from the calculated changes in linear dimensions due to the formation of cracks in the fiber concrete are established. The dependences of thermal changes in the linear dimensions of steel fiber concrete due to the formation of cracks on the ratio of the calculated unreliaxed tensile structural stresses in the matrix to the tensile strength of the matrix are established. Based on the performed studies, a method for predicting thermal deformations, changes in mass, linear dimensions due to the formation of cracks, strength, water resistance of steel fiber concrete, based on thermal deformations and changes in the properties of the matrix, parameters of dispersed reinforcement is formulated.

Keywords: steel fiber concrete, prediction of resistance to thermal effects, cracking, thermal changes in linear dimensions and properties

The article collects and structures information about the effect of chemical additives on the properties of concrete and concrete mix. The relevance of topic is due to the fragmentation of the background information and the lack of data on the study of new additives. The presentation of information in the form of a morphological table simplifies the selection of additives and reduces the risk of errors in the selection of concrete composition. Mineral additives were not considered in this article.

Keywords: construction materials, concrete, concrete mix, chemical additives, concrete properties, concrete composition, modified concrete

Electroretinography is a hightly informative method for diagnosing heterogeneous diseases associated with disorders of the vascular structures. This article describes the biomedical ophthalmic signal of an electroretinogram using wavelet analysis. The spectral characteristics of the signal, the time-frequency picture of the wavelet scalogram are estimated, and approaches to the automation of signal analysis using the available Python libraries are described. The description of the formation of wavelet scalograms of signals using the cwt function of the PyWT library has been formalized. The Gaussian wavelet of the 8th order is chosen as the basic function of the wavelet transform. In order to automate the analysis of wavelet scalograms, the sequence of determining the connectivity of segments using the connectedComponents function from the library of computer vision algorithms, image processing, and general-purpose numerical algorithms with open source OpenCV is described.

Keywords: electrophysiology, epr, electroretinogram, erg, wavelet analysis, decision support system, connected components, Otsu method, retinal dystrophy

The relevance of this study lies in the fact that the mutual influence of existing transport facilities and the newly erected underground part will be taken into account and the ways to minimize the geomechanical impact on each other will be determined. The subject of the study is the stress-strain state of the system ""structure - massif - structure"". The purpose of the study is to minimize the mutual influence of the subway, the railroad and the underground part of the designed building.

Keywords: geotechnical screen, mathematical modeling, FEM, underground structure, mutual influence, stress-strain state, subway station, minimization of influence

The transition of the construction industry to a higher level of competitiveness is due to the implementation and application of digital technologies. Traditional methods of processing incoming information are not effective for managing so much information that modern construction organizations produce. The article discusses the use of digital twins technology in the implementation of investment and construction projects. The purpose of this article is to identify the positive and negative aspects of the introduction of this technology in the activities of design and construction organizations. The main problems in the implementation of information technologies in construction organizations are analyzed. The main differences between information modeling technology and digital twins technology are presented. The advantages for the participants of investment and construction activities from the introduction of digital twins in the implementation of projects are given.

Keywords: BIM technology, digital twin, investment and construction project, digitalization

In the past few years, such objects have begun to be taken outside the city limits and rebuilt in new, undeveloped territories. And on the vacated territory, a new development begins with the intensive development of underground space. The strategic innovative approach to the implementation of projects for the development of the modern city released by the industrial territory is an urgent answer to the question of a completely new understanding of the comfortable environment, in which everything is involved: zoning of the development territory, laying new roads (city streets), underground structures and communications, transport accessibility, environmental friendliness of construction. Without understanding that the problem of forming a living space is complex, in the end, comfortable conditions of human existence will not be obtained. Various modern green building standards are based on this.

Keywords: redevelopment, green standard, BREEAM, industrial territories, industrial facilities, reconstruction, renovation, complex development of the territory, certificate

The effect of a zeolite support on the physicochemical properties of cobalt catalysts prepared by the precipitation method and calcined at 400°C was studied. The values of the specific surface of the catalysts, the degree of cobalt reduction, and the dispersion of the metal were determined, and the presence of functional groups on the surface of the catalysts was determined by BET, TPV, TPD-H2, and IR spectroscopy.

Keywords: catalyst, cobalt oxide, hydrocarbons, dispersion, active surface

A semiconductor quantum wire (QW) containing an impurity center described in the framework of a hydrogen-like model is considered. The possibility of using InSb QW in photodetectors of infrared optical radiation is discussed. The QW is modeled as a geometrically symmetric cylinder, on the axis of which an impurity center is located at an arbitrary point, with which the origin of the cylindrical coordinate system is associated, in which calculations are performed. It is assumed that the magnetic length is much smaller than the effective Bohr radius - the case of a strong magnetic field. This approximation made it possible to make the impurity potential effectively one-dimensional and obtain analytically accurate calculation results. In the effective mass approximation, in the dipole approximation, an expression is obtained for the matrix elements of the optical transitions of an electron from the impurity ground state to the size-quantized QW states for the case of transverse light polarization and the Kane dispersion law of charge carriers.

Keywords: matrix elements of optical transitions, effective mass method, quantum wire, dipole approximation, size-quantized states

The article provides an overview of construction technologies for the construction of multi-storey residential buildings, taking into account the speed of construction and the quality of structures. A summary table of various types of construction is presented, advantages and disadvantages are identified.

Keywords: construction production, optimization, constructive solution, method of construction of buildings, block, panel, large-block, monolithic frame, monolithic, modular, comparison, analysis, advantages, disadvantages

This arcticle are devoted to the modernization of housing and communal system based on the technology of "Smart Grids". The methology of developing an assessment of the effectiveness of the project of the modernization of housing and communal services facilities using the technology of "Smart Grids" is given. It from the publication that the use of "Smart Grids" technology provides energy and economic efficiency in the development of the city's energy system

Keywords: Smart grids, "Smart City", centralized heat supply systems, individual heat supply, evaluation of the economic modernization project, key performance indicators

Frameless arched coverings are one of the varieties of prefabricated structures for various needs: sports facilities, hangars for various equipment, warehouses for vegetable storage, etc. They are economical compared to other structures, since due to their light weight they do not require massive foundations, compared to frame and wall structures and can be laid with a small depth, which in turn saves on land work. Due to this, they arouse interest in their design and in the development of structural improvements, especially for conditions with a sharply continental climate with high precipitation and strong winds. In this paper, frameless arched coverings made of U-shaped profiles were considered, depending on the span of the coating and on the method of insulation for the sharply continental climate of the Republic of Khakassia. As a result, we have received that constructive solutions are required to strengthen these coatings for large spans, for example 15, 20 and 25 meters, or measures to reduce the snow load on the coating.

Keywords: frameless arched coverings, U-shaped arched profile, sharply continental climate of the Republic of Khakassia, polyurethane foam, mineral wool