In this paper, heat transfer in a staggered tube bundle under steady and pulsating flow conditions is analyzed using numerical simulation. The numerical study was conducted for tube bundles with 5, 10, and 15 longitudinal rows. The Reynolds number Re and the Prandtl number Pr were 3400 and 3 respectively. Flow pulsations were characterized by both symmetrical and asymmetrical reciprocating flow. The effect of pulsations was estimated using the product of the relative dimensionless pulsation amplitude and the Strouhal number A/DSh, which corresponded to values of 0.1, 0.25, and 0.4. The numerical study was conducted using Ansys Fluent. The flow hydrodynamics in the tube bundle was described using the Reynolds-averaged unsteady Navier-Stokes equations. Based on the results of numerical simulation, it was found that the effect of pulsations on heat transfer in the tube bundle varies depending on the number of longitudinal rows. It is shown that an increase in the number of rows leads to a decrease in the Nusselt number ratio in a pulsating flow compared to a steady flow. It is established that the thermal-hydraulic efficiency increases with an increase in the number of rows. It is shown that asymmetric pulsations are more effective than symmetric ones for intensifying heat transfer when taking into account energy costs

Keywords: heat transfer intensification, staggered tube bundle, heat transfer, numerical simulation, flow pulsations

A comparative analysis of quality control procedures for incoming construction materials and products in Russia and China is conducted. The study examines the regulatory and legal frameworks, as well as the specific characteristics of organizing and documenting incoming quality control in both countries. Similarities and differences in approaches to ensuring construction quality, preparation of accompanying documentation, and maintenance of incoming inspection logs are analyzed. The prospects for digitalization of document management processes in the construction industry and the need for further research into the organizational aspects of construction quality assurance are discussed.

Keywords: construction supervision, incoming quality control, regulatory framework, as-built documentation, Russia, China

The purpose of this work is to study the applicability of the U-Net architecture for automatically determining the contours of natural skins using the TensorFlow and Keras libraries in Python. A software application has been developed based on methods including OpenCV libraries, as well as a model for implementing a deep convolutional neural network. The dataset for training and testing the network was created using augmentation. Training was carried out using the stochastic gradient descent method after splitting the data sample into training and test images. In the future, the results obtained will be used to create an automated system that will make it possible to determine the contours of the skin and its defects, which in turn will open up the possibility of calculating the useful area of ​​the skin and creating an automated layout of patterns taking into account the identified defects.

Keywords: computer vision, edge detection, natural skin, machine learning, convolutional neural networks, U-Net architecture, deep learning

The rocks that form a natural geological reservoir for underground gas storage, during the operation of UGS, are exposed to prolonged cyclic loads caused by periodic injections and withdrawals of natural gas. At the same time, it is possible to develop and accumulate residual deformations in rocks that cause irreversible changes in the properties of rocks and this must be taken into account when designing and operating UGS.

Keywords: underground gas storage, geomechanical modeling, cavern, salt massif, deformations

the work is devoted to a comparative analysis of various calculation and mathematical models among themselves. The calculation of the frame joint of reinforced concrete structures is performed: a pylon and a cantilever beam. Three methods for performing the calculation of this joint are proposed: an analytical method, a rod FEM model and a volumetric FEM model. The analysis of the calculation results is performed: a comparison of internal forces and calculated reinforcement. The consequences of a superficial analysis of the structure and simplification of calculation models are shown using the example of damage to a real structure under the action of operational loads.

Keywords: reinforced concrete console, structure calculation, node calculation, Lira 10, Russian software, optimal design of reinforced concrete structures, reinforcement analysis

This paper discusses the influence of the turbulence model selection in predicting heat transfer in tube bundles in two- and three-dimensional settings. Numerical studies were performed for in-line and staggered tube bundles using Ansys Fluent software with three RANS turbulence models (k-ω SST, RSM EWT, and RNG k-ε) and a laminar solver. The tube lengths l in three dimensions were 0.5D and 3D, with a fixed tube diameter D. The Reynolds number Re ranged from 100 to 2900. The results showed that the turbulence model selection affects the qualitative flow pattern in tube bundles, with two-dimensional structures predominating in the flow regardless of the turbulence model selection. Therefore, the tube length has virtually no effect on the ability to predict heat transfer intensity. It is shown that when using the laminar solver, the effect of the bundle tube length can be significant depending on Re and the bundle layout. Good agreement with experimental data is obtained for the RSM EWT and RNG k-ε EWT models. For a staggered bundle, when choosing the k-ω SST model, satisfactory agreement with experimental data is observed, while the heat transfer of the in-line bundle is significantly underestimated. The use of the laminar solver in a steady-state formulation is justified for a pronounced laminar flow, at Re < 1000 with a further increase in Re, it is necessary to use a unsteady formulation with sufficient time and mesh resolution.

Keywords: convective heat transfer, in-line tube bundle, staggered tube bundle, computational simulation, turbulence modeling

The work is devoted to the study of the temperature distribution and equivalent voltage on the surface of a thermal radiation receiver during experimental and computational series. The experiments showed a qualitative and quantitative coincidence of the temperature data obtained by thermal imaging with the results of numerical modeling. The average error was 0.5℃, with a maximum deviation of 1.5℃ at individual points, which is due to edge effects and thermal insulation features. The computational model reproduces the main characteristics of the temperature field, including the effect of shielding, using a relatively low density of the computational grid. As part of the verification of the numerical model, the analysis of grid convergence was carried out, as well as the control of residuals and control of solution parameters were performed.

Keywords: heat exchanger, numerical and analytical calculation, convective and radiant heat transfer, efficiency improvement, outgoing flue gas, heat recovery, gas-liquid heat exchanger, numerical modeling, mathematical model, ANSYS Workbench software

The calculation of the coefficients of the linear best method for restoring the second derivative at zero of a bounded analytical function given in a unit circle by the values of the function and its derivative at specified points forming a regular polygon centered at zero is pointed in that paper. It also determines the error of the best method and finds the corresponding extreme function. It is proved that the extremal function is unique. At the end of the work, formulas are got that can be used to calculate the coefficients of the linear best method. In finding of these formulas, the method of duality of extreme problems was applied, which was deeply developed by S.Y. Havinson. It is proved that these coefficients are the only one.

Keywords: optimal recovery, error of the best method, linear best method, coefficients of the linear best method

Eye tracking (oculography) is a technology that allows recording the direction of human gaze on a visual stimulus. It’s application can provide researchers with valuable data on which elements of the environment are most attractive in various contexts, in areas such as marketing, psychology, etc. The aim of this work is to identify the pattern of human attention distribution on visual stimulus objects of different sizes using eye tracking technology. A webcam was used to record the subjects’ gaze movements while they were studying experimental images. The results of the experiments showed that larger objects in visual stimuli receive higher attention priority than smaller objects. This observation is true for both human-created works and images created by artificial intelligence (Kandinsky 3.1 is used in this study). The obtained results of the study will improve our understanding of how people perceive visual information, which can contribute to the creation of more effective approaches to interface development.

Keywords: eye tracking technology, attention priority, region of interest, number of eye gaze registrations, artificial intelligence, Vincent Van Gogh

Radiative cooling is an innovative and highly promising passive cooling technology that allows surfaces to dissipate heat via infrared radiation directly into the cold outer space. Unlike traditional cooling methods that require an external energy source, radiative cooling operates autonomously, offering a sustainable and energy-efficient alternative for temperature control. This natural process has attracted considerable attention in recent years due to its potential to mitigate the growing energy demands associated with air conditioning and refrigeration, which contribute significantly to global energy consumption and environmental degradation.

Keywords: radiation cooling, temperature, atmospheric window, air conditioning, energy efficiency, passive cooling, calcium carbonate, barium sulfide, boron nitride, titanium dioxide

The paper presents the formulation of problems of minimization and maximization of a linear functional with inequality constraints on the vector of admissible program motions and equality constraints specified by a linear manifold. An analytical solution is synthesized that determines the projection operator for solving the specified mathematical programming problems with equality constraints and inequalities. An analytical solution is obtained that determines the boundary values ​​of the Lagrange multiplier for the synthesized projection operator. The correctness of the obtained solution is illustrated.

Keywords: mathematical programming, linear functional, projection operators, admissible program motions, stabilization of program motions, SimInTech

The article considers a variant of constructing a digital twin model for diagnostics of operation of a mechanical gear transmission - a reducer consisting of a pair of cylindrical gears. The basis of the considered digital twin model is an adaptive learning vibration mathematical model of the static operating mode when gears rotate at a constant speed. The vibration signals of the reducer, recorded by accelerometers and effective for detecting and diagnosing faults, are used as the main information measured at the facility. The detected faults are cracking, wear, chipping and pitting of teeth. A special feature of the implemented digital twin is the ability to simultaneously detect faults of several teeth at once, both on the driving and driven gears, by time and frequency characteristics, as well as the ability to determine the main technical data of a specific reducer by vibration characteristics.

Keywords: diagnostic mathematical model, digital twin, vibration diagnostics, mechanical gearbox, tooth defect, diagnostic signal, vibration power spectrum, synchronously averaged time characteristic

The work is devoted to the description of the effectiveness of the use of geographic information systems (GIS) for the analysis of demographic processes. GIS allows you to take into account the spatial reference of the estimated indicators, simulate various demographic processes such as migration flow, natural population growth, and have tools for creating analytical maps and spatial analysis. All of the above significantly improves the results of the analysis of demographic processes and makes it possible to identify patterns of various situations depending on their location. The paper provides a geospatial analysis of demographic processes in the Southern Federal District (SFD). The QGis GIS has developed a project in which a map of the Southern Federal District territory is visualized with linked up-to-date statistical information, cartograms reflecting natural population growth and migration processes of the Southern Federal District for 2023-2024 are built. Based on the developed project, a geospatial analysis was carried out, reflecting the spatial and temporal features of demographic processes and trends in their development.

Keywords: geoinformation system, demographic process, geospatial analysis, QGis, cartogram