In this work, the effective thermal conductivity of porous materials is studied by a numerical method. A technique for designing an insulating material with specified geometric characteristics is proposed, which makes it possible to predict the thermal conductivity of porous insulation with sufficient accuracy. The design of foamed porous heat-insulating materials was based on the 3D Voronoi tessellation. The effective thermal conductivity of porous media was determined for twenty structures with different geometric characteristics. The thermophysical properties of the material corresponded to melamine. To verify the numerical solution, the effective thermal conductivity of the melamine sponge was determined experimentally. One regular structure and three irregular structures were compared with each other. The porosity of the insulating structures ranged from 0.722 to 0.987, the fiber diameter ranged from 0.0489 mm to 0.1259 mm. A theoretical solution is proposed for determining the effective thermal conductivity of regular structures. The technique proposed in the work can be used to design heat-insulating materials based on additive technologies, with specified heat-insulating and structural properties.
Keywords: effective thermal conductivity, porous structure, porous insulating material, 3D Voronoi tessellation
In this work, a theoretical determination of the transfer coefficient of millimeter-wave mixers based on resonant tunneling diodes is carried out. The analysis of the conditions for optimizing the transmission coefficient of microwave mixers using resonant tunneling diodes as nonlinear elements is carried out. The optimal constant voltage is determined, at which the amplitude of the local oscillator, required to obtain the maximum transfer coefficient of the mixer, will have the smallest value, and the coefficient itself will be the largest.
Keywords: gain, mixer, millimeter wave, frequency conversion, local oscillator amplitude, modified Bessel functions, stability factor, resonant frequency, bandwidth
The paper considers the quasi-stationary motion of a viscous compressible fluid in the gap of a thrust bearing with a nonlinear contour of the support surface of the slider. It is assumed that the slider is stationary, and the guide with the molten surface moves in the direction of narrowing the gap at a time-dependent speed. Well-known equations are used for the solution: the equation of motion of a compressible fluid, the equation of continuity, the equation of state and the equation describing the profile of the molten contour of the support ring. The case is considered for the extreme and non-extreme case, that is, when the parameter of the specific heat of melting tends to infinity and vice versa. As a result of an accurate self–similar solution, the main operational characteristics are determined - velocity and pressure fields, load capacity and friction force. The problem of the stability of the movement of the support ring is also solved. The final stage of theoretical calculation methods is numerical analysis.The analysis of its results showed that the modified design of the thrust sliding bearing, taking into account additional factors, has a bearing capacity value exceeding the standard designs by 8-11% in the range of load-speed modes studied. The coefficient of friction is reduced by 9-13%.
Keywords: quasi-stationary flow, extreme case, metal coating, non-standard support profile, hydrodynamic mode, stability of the guide movement
The simplest, most reliable and sufficiently accurate method of dosing bulk products is batch dosing by volume using measuring containers. The article considers a mathematical model of a volumetric dispenser. The combination of several methods of regulating the supply of bulk materials during batch dosing is ensured by building an accurate model of the drum dispenser.
Keywords: mathematical model of a drum dispenser, dosing process, friction, dynamic coefficient of friction, static coefficient of friction, bulk material
The object of the research is the utilization heat exchanger. The purpose of the work is to develop a design of a heat exchanger (HA) used to recover the heat of exhaust gases from a gas turbine unit (GTU) with an increased thermal power. In the process of work, the calculation and numerical modeling of the new design of the heat exchanger was carried out. The result of the research was the design of a gas-air heat exchanger, which requires 6.5% less flow rate of the coolant (exhaust gases) compared to the prototype.
Keywords: heat exchanger, heat utilization, energy efficiency of a gas turbine unit, numerical modeling, gas-air heat exchanger
The global global trend in the development of modern computer technologies contributes to the introduction of BIM technologies in the design, construction and operation, working with a single model of a building or structure throughout the entire life cycle. The challenges that arise in the design and construction process stimulate the development of digital technologies, and those, in turn, require continuous study and improvement of knowledge in these areas. To maximize the effectiveness of projects and the implementation of architectural thought by means of information technology, new requirements for the work of architects are emerging. In this direction, it is necessary to train architects and designers of a new generation and to retrain long-time practitioners. In this paper, we have considered the advantages and disadvantages of the transition of the full cycle of architectural and construction design in IT modeling. We studied the issue of rapid identification of shortcomings and instability of the design of the projected building due to the integration of programs: ArchiCAD, SAPPHIRE, LIRA-CAD.
Keywords: architectural environment, information technology, integration, BIM, design, IT modeling, construction
The article presents the results of the development of the combined medical measuring device - an ophthalmopneumogoniometer, with the help of which it is possible to measure intraocular structures and pressure . Based on the results of the analysis of the subject area, the author proposed a structural diagram of the device, considered technical solutions of its individual elements.
Keywords: ophthalmopneumogoniometer, ophthalmogoniometry, intraocular pressure, eye optics
The paper studies the issue of the influence of the quality of the computational triangular grid on the accuracy of calculations in various computational problems. There is a well-known example of Schwartz, which shows that the approximation of a smooth surface by a polyhedral surface can give very large errors for calculating the surface area. This is due to the quality of the constructed triangulation of the surface. Therefore, it is natural to expect that there is some connection between a certain triangulation characteristic and the accuracy of solving some computational problem. In the presented article, as such a characteristic, a value is chosen - the average value of the minimum sine of the angle of all triangles of the computational grid. In the course of numerical experiments, the Dirichlet problem for the Laplace equation in a circular ring was solved, in which the error of the approximate solution was calculated (the gradient descent method was used to find a solution to the corresponding variational problem.). For the ring, a series of triangulations was constructed with a uniform division along the angle and a non-uniform division along the radius in polar coordinates. In this example, a linear dependence of the error on was shown. The article presents both the results of the calculation with different values and the calculation of the correlation coefficient of the studied quantities.
Keywords: boundary value problem, Delaunay triangulation, calculation accuracy, Dirichlet problem, mathematical modeling, triangular mesh, minimum triangle angle, piecewise linear approximation, variational method, Laplace equation
This article considers one of the parts of the development of a device for determining the magnetic characteristics of ferromagnetic materials with a shape memory effect. A functional diagram of the device has been developed. The operation of the device was simulated and the behavior of the shape memory alloy was studied. The error in determining the magnetic characteristics of the FMSF using the magnetizing setup of the developed device did not exceed 0.25%.
Keywords: magnetostrictive materials, basic magnetization curve, magnetic shunt, magnetic flux
This article discusses the development of a magnetometer calibration device, which is controlled by a microcontroller, Arduino [1, 2], which can receive, process and transmit the necessary commands to the peripheral part of the installation using the written program code. The need for buffer circuits and elements allows you to control I / O devices. With their help, interface hardware is implemented. Structural and functional diagrams of the device were developed. And also the calculation of the parameters of the Helmholtz coils was carried out, their 3D model was built. With the help of the Gaussmeter, a full-scale experiment was carried out, which confirmed the operability of the device and its effectiveness.
Keywords: control and measuring device, induction, Helmholtz coils, gaussmeter
This article discusses the development of a digital weather station with the measurement of geomagnetic field parameters. The advantage of the developed device is the possibility of simultaneous stable and correct operation of several sensors (namely 15), measurement accuracy at long distances (up to 300 meters). Structural and functional diagrams of the device have been developed. The voltage regulator of the device is designed in the Micro-Cap circuit analysis program. Experimental studies of the finished device were carried out.
Keywords: digital weather station, geomagnetic field, magnetic sensor, Arduino
This article discusses the development of a control and measuring system for reading barcodes from printed circuit boards in the production process. A functional diagram of the device was designed. A full-scale experiment was carried out to determine the working distance and angles for reading barcodes. It was revealed that the developed system has competitive advantages over analogues in a higher barcode reading speed and work with different barcode inclination angles.
Keywords: control and measuring system, bar code, printed circuit boards, laser range finder
This article considers the development of an information-measuring system for determining the thermophysical parameters of electrical devices. The developed functional diagram of the device is presented. Experimental studies were carried out in the COMSOL program. As a result of an experimental study of the transfer of heat from one part of the electromagnet to another, namely from the magnetizing coil, through the core to the environment, it was concluded that the best location of the temperature sensors is in the upper part of the body of the electromagnet EM-34-5. The data obtained can be used to determine the thermophysical parameters, in solving problems of the theory of inverse problems of heat transfer and heat transfer.
Keywords: information-measuring system, electrical devices, thermophysical parameters, COMSOL
An integrated information-measuring system is presented, which includes: a personal computer, special software, a set of sensors, an analog-to-digital and digital-to-analog converter, which makes it possible to investigate corrosion processes. Some possibilities of using modern information technologies in the workshop on physics and electrochemistry are shown. An experiment was carried out to study metal corrosion and its suppression using a traditional installation and a modified one using modern information technologies.
Keywords: software package, metal corrosion, natural experiment, integrated system, information technology
This article considers one of the parts of the development of the input control device for film capacitors. Structural and functional schemes have been developed. The results of modeling the measuring circuit in the Microcap software package are presented. The results of the model experiment confirm the correctness of the calculations.
Keywords: input control, film capacitors, Arduino, Microcap, diagnostics
The article presents the calculation of various variants of corrugated rollers with different characteristics of wall shelf thicknesses and comparison with the standard adopted I-beam used in construction. The main requirement when comparing options is the maximum deflection of the studied beams with a deflection in the reference beam based on the calculation in the Ansys software package, which calculates models using the finite element method.
Keywords: corrugator, finite element method, Ansys software package, comparison of variants, modeling, I-beam, beam
The work is devoted to the study of the possibilities of ensuring the unconditional achievement of the goals of industrial enterprises with a combination of modal management and linear regulation with cost optimization in the operational and tactical management of quality management systems. The commonality of dependencies in modal control and linear regulation is shown. An approach to the combination of modal control and linear regulation is proposed, including the determination of the possibilities for changing the elements of the system matrix, as well as the search for optimal or rational solutions based on cost accounting. The application of this approach is considered on the example of the activity of an industrial enterprise. It is established that modal control has no advantages over linear control, since it is used to increase the stability of systems. The performance of quality management systems can be ensured when it is transferred to an unstable mode of operation, however, the use of this mode cannot exceed two to three years.
Keywords: quality management system, modal management, linear regulation, optimization, enterprise potential, personnel resistance
The global economy growth and active industrial development are limited, among other things, by the capabilities of existing technology. The potential for improving the functional characteristics of classical materials is practically exhausted, and the widespread use of new composite materials and high-enthalpy alloys is limited by the high cost and complexity of the technological process of their manufacture and processing. Knowledge of the materials physical-mechanical, thermophysical and chemical characteristics proves that the surface structural-phase state in many cases is crucial in the processes of wear, fracture, chemical and thermal destruction. Thus, the issue of developing technologies and equipment for modifying the surface layer and creating multicomponent coatings, including nanocomposite ones, is urgent. Current article presents the results of a study devoted to the creation of a facility for such coatings deposition by plasma spraying. One of the key elements of technological equipment for this method is a vacuum chamber, which is exposed to intense thermal stress during operation. Thus, the issue of designing a cooling system is relevant. To reduce the material and time resources at the design and experimental development, the temperature state of the chamber was simulated. It is shown that to ensure safe operation, it is advisable to use water cooling. The simulation results confirm the operability of the vacuum chamber cooling system under operating conditions. The following operating parameters were determined: the inlet pressure is 0.6 MPa, the water flow rate is 2 l/s, and the mass average temperature of the outlet water is about 40°C.
Keywords: plasma spraying, thermal state simulation, vacuum chamber, cooling system
Simulation modeling of protective circuits of a DC transistor electronic device is considered. It is shown that simulation modeling is one of the advanced research methods. The application of the Simulink program for this purpose is justified. The transistor switching device is considered from the point of view of overvoltages arising when the current is switched off. A simplified circuit of the switching device necessary for conducting research is given. A complete diagram of the Simulink model is given. Protection schemes using resistors, capacitors and varistors are given. The magnitude of overvoltages on a transistor with a different combination of protective circuits is investigated. The dependences of the overvoltage magnitude on the switched current for various combinations of protective circuits are given. The dependences of the overvoltage magnitude on the parameters of the elements of the protective circuits are given. The conclusion about the necessary structure of protective circuits is formulated.
Keywords: simulation, Simulink, switching device, overvoltage, transistor, protective circuit, varistor
The article provides a consideration of the prospects of replacing the lateral stability stabilizer with a pneumatic balloon in the suspension together with body level sensors relative to the road surface.
Keywords: public transport, bus, spring - air suspension, body level sensor
Transportation is one of the most important stages in the management of cement delivery, which accounts for 60% of total costs. Thus, a slight improvement in the collection and processing of data on the operation of concrete mixers can have a significant impact on the overall savings spent on the work of companies engaged in transportation. On the other hand, the movement of heavy vehicles carrying cement mixture leads to the spread of air pollution and damage to the road surface in case of excessive loading. Therefore, the issue of determining the route of the vehicle to achieve this goal is very important. In this study, the routing process of concrete mixers was modeled using random routing problems and genetic algorithms. The simulation results showed that the genetic algorithm converges to the optimal answer. On the other hand, the volume of the cost function decreases from 1,177,500 rubles to 158,900 rubles. due to the optimization of the mentioned model, and the performance result led to the appearance of the shortest possible path. With the help of the algorithm, all the parameters of sustainable development management are achieved, including reducing air pollution, reducing fuel consumption and reducing the destruction of the road surface. Finally, thanks to the integration of the GLONASS/GPS software, the output data of the algorithm was mapped to the map.
Keywords: optimization of routes, fuel efficiency, reduction of emissions, preservation of the integrity of the road surface, optimization, logistics, modeling, special car, urban operation
The article proposes a method for analyzing and assessing the quality of wheat seeds by classifying their images using artificial intelligence, namely a convolutional neural network. The architecture of a deep convolutional neural network was proposed, an image base was created for training and testing the proposed neural network, training and testing of the neural network was carried out in Tensorflow. Conclusions about the efficiency of image classification are made and areas of use of the proposed method for analyzing and assessing the quality of wheat seeds are proposed.
Keywords: convolutional neural networks, artificial intelligence, image classification
Agents of the transport and logistics market (TLM) in the implementation of their activities implement solutions aimed at maintaining and developing their position in the market through active interaction with counterparties (cooperation, diversification of capital and activities) in changing environmental conditions. The limited volume of transport services and changes in its structure require formalization and systematization of possible actions of agents. The paper provides an analysis of the factors influencing the activity of TLM agents, their formalization and schematic solutions for the implementation of their activities.
Keywords: transport and logistics market, activity, market agent, stability, formal model, efficiency indicator, profitability of services, logistics chain, volume of transport work, railway transport
An overview of the rationale for the use of lightweight multi-hollow floor slabs is given. Technological and design features of multi-hollow floor slabs are considered. The possibilities of rational use and labor intensity of lightweight hollow floor slabs are presented. On the basis of existing technologies, calculation methods for lightweight hollow slabs and current norms, the calculation of monolithic slabs in the Lira software package was carried out. The work of floor slabs with spans equal in two directions is considered. It was found that regardless of the span of the floor slab, the effect of reducing its own weight exceeds the effect of reducing the cruelty of the section. The total deflection from the floor slab's own weight and payload on it for hollow slabs is lower than for solid slabs of the same span.The conducted numerical experiment allows us to establish the limits of the effectiveness of the use of lightweight multi-hollow monolithic floor slabs, upon reaching which the use turns out to be significantly more profitable than the use of traditional girderless floors.
Keywords: constructive scheme, software package, overlap, building, multi-cavity plate, calculation, labor intensity, design
The paper proposes a method for preparing a dataset for training and testing neural networks in the MATLAB environment using the Image Processing Toolbox package of functions. An example of the implementation of this technique for preparing a dataset for training convolutional neural networks to classify wheat seeds into high-quality and low-quality classes according to its images is given. This technique was used to obtain a dataset of 900 images, which were successfully used to train and test the convolutional neural network.
Keywords: dataset, convolutional neural networks, artificial intelligence, image classification