The paper studies a mathematical model of a function that can be restored by integrals. In order to reduce image distortion during reconstruction, the representation of the desired function in the form of a sum of Gauss functions is proposed. A software package has been developed to study the model. The parameters and type of the grid giving the smallest error in this model are determined.

Keywords: mathematical modeling, inverse problem, Radon transform, image reconstruction, Gauss function, computed tomography

Cementation studies focus almost exclusively on the movement of carbon, described through the diffusion equations, often with constant coefficients and without regard to temperature. This approach does not allow, to take into account the further diffusion of carbon into the workpiece in a lower temperature range at the stage preceding quenching. The paper describes the modeling of the diffusion saturation of steel by carbon in the cementation process, taking into account the influence of temperature on the example of a numerical solution of the gear cementation problem using the COMSOL Multiphysics program. It was shown that the finite element mathematical calculation of the process of saturation of austenite with carbon during cementation gives good agreement with experimental data, and finite element analysis methods can be used for multivariate calculation of the carbon content in austenite after diffusion saturation

Keywords: carbon diffusion, carburization, COMSOL Multiphysics, numerical modeling, carbon distribution, carburization, Fick diffusion law, mass transfer, heat transfer, gear, finite element method

The article presents materials on the study of increasing the operational life of steel ropes. The methods of lubrication of steel ropes, as well as the resistance characteristics of the applied lubricants, under various operating conditions, were studied. An experimental study of the effect of molybdenum disulfide on the operational characteristics of steel ropes. The concept of a useful model for the formation of a surface layer of a solid lubricant coating based on molybdenum disulfide on steel ropes in the process of their production is proposed.the mode of operation of the Elevator equipment in each cycle. The structure of the algorithm for the formation of accumulated loads and their equivalent value during a given period of operation is substantiated. The proposed method can be used as a simulation model in determining the required amount of repair impacts in the maintenance of passenger elevators

Keywords: steel rope, rope lubrication solid lubricants, vibration mechanochemical solid lubricant coating, molybdenum disulfide, utility model

the article analyzes various options for the device of floors in low-rise construction, considered various modern systems of prefabricated monolithic floors. The advantages and disadvantages of modern different types of floors in low-rise construction are described.

Keywords: Monolithic slab, composite slab, the precast-monolithic slabs, comparison, advantages and disadvantages, technology construction

The paving slab market analysis and development prospects for the Rostov Region are given in this article. The market prospects are considered from the point of view of paving slab manufacturers on their participation in government programs of a modern urban environment formation and improvement. The main changes in the product specifications requirements are considered taking into account the enactment of GOST 17608-2017 instead of GOST 17608-91. We analysed the pricing policy of large manufacturers of paving slabs operating in the Rostov Region. Then we also considered the prospects of paving slab sales for municipal projects and in the private segment. We also reviewed the government programs for creation of a comfortable urban environment and their financing in the Rostov Region, as well as cooperation prospects between the municipal government and business in terms of concession agreements. Finally, we defined the main consumer categories for the paving slabs and the consumption structure of the paving slabs market.

Keywords: paving flag, paving slabs, improvement, modern urban environment, the formation of a modern urban environment, paving

The simulation of a multilayer structure in the finite element Ansys complex is considered. The design consists of 10 layers, each of which has certain specific properties. The model is an imitation of the soil base pavement. We consider the simulation in the form of a simplified, flat statement of the problem. The analysis of the oscillations under impact. The wave field of displacements at a given part of the structure is analyzed. Based on a numerical experiment, an approach to estimating the characteristics of a layer is constructed.

Keywords: multi-layer construction, vibration diagnostics, simulation, FEM, Ansys, pulse action, dynamics, fluctuations

The article presents the results of testing samples of welded joints of polyethylene pipes for crack resistance at various temperatures. It is shown that in the weld zone a decrease in the stress intensity factor is observed up to 27% compared with the base material.

Keywords: Polymer, polyethylene, pipe, stretching, crack resistance, low temperatures, brittle failure, crack, welding, welded joint, fusion zone

The article conentrates on the problem of synchronization the pseudo-noise sequence in direct sequence spread spectrum systems. Authors propose a method for transmitting information and synchronizing signals on a single carrier frequency, which allows data transmission in complex coditions in radio channel. A brief review of existing solutions for time synchronization direct sequence spread spectrum systems is carried out. The proposed solution is considered in terms of data transmission in broadband systems in the conditions of negative signal-to-noise ratio, while the limitations of the usage of this solution are also considered. A simulation of the scheme that implements the proposed synchronization method is carried out, and the requirements for the signal-to-noise ratio in the information and synchronization channels are determined. The proposed method can find application in systems with code division multiplexing, including modern IoT systems.

Keywords: time synchronization, direct sequence spread spectrum, broadband communication systems, Internet of Things, BER

Paper presents a review of scientific works investigating of effect of carbon nanotubes (CNT) concentration on electrical conductivity and pizeresistive properties of concrete. Different values of the percolation threshold for nanomodified concrete obtained by different authors are given. Recommendations for specifying the favorable concentration of nanotubes in composites are considered. As a result of review a need for additional dedicated research for the assessment of relation between favorable CNT concentration and their characteristics, method for the producing of composite and conditions of its application is stated.

Keywords: concrete, sensor, carbon nanotubes, percolation threshold, electrical conductivity, monitoring of stress-strain state

The article describes the principles of the method of x-ray photoelectron spectroscopy. There is described a method for the possible application of the XPS method in fire-technical expertise. There ar given criteria for determining the type of short circuit on electrical products removed from the fire. Depending on the conditions of the occurrence of the circuit of the conductors changes their chemical composition. There are describe of the implementation of existing methods of analysis used in fire laboratories. There given a brief description of the main components of the time-of-flight spectrometer, including an x-ray tube, time-of-flight energy analyzer, and the principles of their operation. Application of the principle of aggregation of spectrometer elements makes it possible to simplify the adaptation of the method of X-ray photoelectron spectroscopy to solving problems in the field of fire safety. There is describe experimental technique in the author’s spectrometer.

Keywords: X-ray spectrometer, x-ray tube, photoelectron spectrum, vacuum system, short circuit, fire-technical expertise, time-of-flight energy analyzer

The paper presents the research results of the influence of materials, which change a phase on the exterior surface of the outer shell, on forming of the heat flow mean value for one year, calculated on change of the exterior temperature per every three hours. The correlation between heat flow and characteristics of the phase-change material was studied. Such materials increase heat lag of the outer shell and allow reducing the amount of electric energy required to keeping of indoor climate. The paper presents the research results of the influence of materials, which change a phase on the exterior surface of the outer shell, on forming of the heat flow mean value for one year, calculated on change of the exterior temperature per every three hours. The correlation between heat flow and characteristics of the phase-change material was studied. Such materials increase heat lag of the outer shell and allow reducing the amount of electric energy required to keeping of indoor climate. Based on the implementation of the method of math planning of experiments the sufficient math model of the dependence of the heat flow density on the material coating thickness, latent heat of transition, heating capacity value and thermal conductivity before and after phase change was made. The mathematical model coefficients were interpreted and best values of very factors based on desirability function were determined. Based on these data the selection of the material with phase-change temperature of about 0 0C for Krasnoyarsk was made.

Keywords: energy efficiency, heat flow, heat saving, heat-storing material, phase-change heat storing, phase-change material

In this article there analyzed the three step approach in a modified spectral characteristics evaluation method using discrete transformations of Walsh and method of parametric spectral analysis of Proni. There briefly described the method based on the method of parametric spectral analysis of Proni, describing the positive and negative qualities. It is also proposed to apply a discrete change of Walsh and Hadamard. There suggested the use of three step procedure. Applying of Walsh discrete transformation will simplify and reduce the computational procedures. When applying these transformations for analysis of mathematical models of processes with similar characteristics, it is proposed to calculate the templates, and then to compare these templates. And templates for each group are invited once to calculate parameters using a modified Prony method or Prony and Berga combined method. Later on using Walsh transforms it is necessary to compare the results obtained with the available templates.

Keywords: modeling, spectral analysis, Proni method, method of Walsh, the model order discretization step response duration

The paper presents the results of studies of the effect of ion-argon bombardment in vacuum on the spectral distribution of the photoconductivity of CdS crystals in the region of the fundamental absorption edge and on the current-voltage characteristic of the semiconductor under study. In the course of research, characteristic changes were found in the spectral distribution of the photoconductivity of a CdS crystal in the edge region of the spectrum and in its current-voltage characteristic at room temperature. It was shown that low-dose ion-argon bombardment leads to an increase in photosensitivity, as well as to a change in the spectral distribution of the photocurrent beyond the absorption edge of a semiconductor. It was found that the exposure of the sample, after exposure to it with argon ions, leads to the relaxation of the photoconductivity spectra of CdS crystals in the direction of the initial distribution. The observed spectral changes are associated with a decrease in the surface concentration of the recombina-tion centers, as well as with an increase in the number of near-surface donor self-defective centers, caused by the action of argon ions on the surface of CdS crystals. Exposure of the CdS crystal under investigation in the air, after exposure to it with argon ions, leads to a reverse increase in the number of recombination centers on the sample sur-face due to the interaction of the surface of the semiconductor with oxygen contained in the air.

Keywords: ion-argon bombardment, photoconductivity spectra, CdS crystals, surface recombination, current-voltage characteristic

Biphasic composite materials were synthesized near the La0.7Sr0.3MnO3-based percolation threshold and the second phase, which is an inorganic or organic compound — polyvinyl acetate, paraffin, carboxymethylcellulose, sucrose, and ultrafine silver particles. For composites with an organic matrix, the magnetoresistance values ​​do not exceed 2%, and for composites with silver particles - 8%. The values ​​of isotropic negative magnetoresistance for ceramic samples of 80% LSMO / 20% GeO2 (mass%) reach 13% in a 15 kOu magnetic field with a sensitivity of about 1% / ke in the low-field region. High chemical and radiation stability of these glass composites should be noted. The magnetoresistive properties of such compounds slightly decreased after 60 days of being in water with a salinity of 35 ppm. Composites of 80% LSMO / 20% GeO2 were exposed to X-rays with a dose of 7 Sv from the Co57 source. The magnetoresistive properties and electrical resistance of these composites did not change after that.

Keywords: lanthanum strontium manganite, ceramic two-phase material, one-step synthesis, radiation exposure, magnetoresistance, percolation threshold, dielectric constant, barrier layer, spin-dependent tunneling, spin polarization

The article considers the modeling of wind impact on the objects of parametric architecture. To determine the optimal shape of the surface, the evolution of the analytical surface shaping, formed by congruent curves in parallel planes, obtained by the rotation of the reulault triangle with a plane perpendicular to the axis of rotation, is studied. Based on the results of a numerical experiment using the finite element method, the rational analytical surface of the object of parametric architecture, resistant to wind, is determined. The dynamic characteristics of the object of parametric architecture are obtained. Recommendations are given to clarify the methods of determining the wind load for buildings and structures of complex geometric shape.

Keywords: parametric architecture; wind load; modal analysis; pulsation component; building frame; finite element method