The key parameter of any cooling system is the heat transfer coefficient. The article deals with the issue of studying the dependence of the thermal resistance of the heat exchanger of a liquid cooling system based on ferrofluids and the heat transfer coefficient on the parameters of the fluid flow and the magnetic field in the heat exchanger. The study was carried out by numerical simulation and thermophysical experiment. A feature of the considered cooling system is the coolant. A ferromagnetic liquid based on Fe3O4 magnetites and propylene glycol is used as a coolant. As a result, a numerical model for calculating the heat transfer coefficient for an experimental liquid cooling system is obtained. The influence of the magnetic field on the thermal resistance of the system and the heat transfer coefficient of the wall-liquid at various magnitudes of the magnetic field strength is estimated. An experimental dependence has been obtained showing an increase in the heat transfer coefficient up to 12.5% when a magnetic field is applied.
Keywords: numerical model of heat transfer, liquid cooling system, Laplace equation, thermal management, CPU, ferrofluid, percolation, heat transfer coefficient, nanofluid, magnetic field, electronics cooling
The article discusses the effect of photon drag (EPI) of electrons in a semiconductor quantum wire (QW) with hydrogen-like impurity centers and Kane's dispersion law, located in a longitudinal magnetic field. An analytical expression for the drag current density is obtained in the effective mass approximation, and its spectral dependence is investigated for various values of the magnetic field B and the parameters of the QW upon scattering by a system of potentials of short-range impurities. It was assumed that the QW has the shape of a circular cylinder, on the axis of which hydrogen-like impurity centers are localized. It is shown that, in the one-band approximation, taking into account the nonparabolicity of the dispersion law leads to significant dynamics of the threshold of the spectral curve. The spectral dependence is characterized by a pronounced Zeeman effect. The possibility of using an ESP for the development of photodetectors of optical radiation with a sensitivity controlled in a magnetic field is discussed.
Keywords: electron dragging by photons, quantum wire, hydrogen-like impurity centers, dragging current, dipole approximation
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
Due to the constant increase in production, new structural materials development and growing rates of non-renewable resources consumption, the issue of increasing the machinery resource is urgent. Thus, it is necessary to develop technologies for spraying coatings that improve the functional characteristics of products, in particular, impact strength, microhardness, resistance to wear, corrosion and other environmental factors by modifying the surface layer structural-phase state. These technologies application is necessary in strategically important industries, such as machine tool manufacturing, aerospace, automotive, shipbuilding, chemical, energy, etc. This article is devoted to the facility development for multicomponent nanocomposite coatings sputtering. The design and commissioning of such a facility requires a high time and material resources investment. In this regard, it is necessary to use modern computer software systems that allow simulating multiphysics processes that take place during the facility operation. The simulation of the cathode-anode unit was carried out. Based on the simulation results it was shown that it is necessary to take into account the physical processes in the interelectrode region when designing the plasma spraying unit, since the resource of the cathode-electrode unit and the productivity of the sputtering process directly depend on the parameters of the discharge and the resulting plasma jet. Thus, high temperature and current density, as well as the arc spot abrupt movement, lead to increased wear and failure of the copper nozzles. The maximum values of the temperature and velocity of the plasma jet during spraying were 32000 K and 1800 m/s, respectively.
Keywords: plasma spraying, multicomponent nanocomposite coatings, multiphysics processes, mathematical modeling
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
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 presence of vibration loads in any node or unit almost always leads to negative consequences in one way or another. Vibrations affect both biological objects and materials. High level of vibrations, under certain conditions can even lead to the destruction of the surfaces of parts and node as a whole. The purpose of these studies was to study the vibration-absorbing ability of zinc electroplating, used to restore the seating holes of the housing parts of machines. The main task was to determine the presence and the level of vibration-absorbing ability of zinc in relation to grey cast iron SCh18. The research was carried out on a laboratory prototype of a gearbox (gear reducer) with the use of vibration sensors and an oscilloscope. As a result, the vibration damping ability of galvanic zinc was proved and the comparative level of vibration damping in comparison with Cr18 cast iron was determined. For this study, zinc was electroplated from sulfuric acid electrolyte on the inner surface of the cast iron shells. First, readings were taken without zinc plating, then a 0.1 mm zinc layer was applied and readings were taken. After obtaining the data, the zinc layer was removed mechanically, the next 0.2 mm coating layer was applied and the readings were taken. The process was repeated with a coating interval of 0.1 mm until the zinc electroplating thickness of 0.6 mm was reached.
Keywords: load, vibration, vibration-absorbing capacity, electroplating, substrate, vibration velocity, vibration acceleration, oscillograms, sulfuric acid electrolyte, zinc coating, gray cast iron
This article is devoted to the study of concentrations of carbon monoxide (II), phenol, formaldehyde, aliphatic hydrocarbons in the premises of buildings, including the assessment of the regularities of their vertical distribution in the height of buildings at different times of the day from vehicles. Research is necessary to develop a program for electronic computers, which is necessary for the design of construction projects.
Keywords: помещения, оксид углерода (II), фенол, формальдегид, углеводороды алифатические, здания, время суток
An analysis of the accident rate on gas pipelines is given. Mathematical dependences of the volume of gas entering the atmosphere during the degassing of a gas pipeline section are given. Based on the existing nomogram for determining the gas compressibility factor for main gas pipelines, a nomogram for natural gas transported through gas distribution networks was constructed.
Keywords: gas pipelines, accident rate, degassing, gas bleeding, gas compressibility factor
The article analyzes the impact of the transition to distance learning on the academic performance of students of the Institute of Computer Science, Electronics and Robotics. The disciplines are identified, the development of which does not cause difficulties in the remote format and disciplines to which such technologies are difficult to apply. Based on the findings, recommendations are given to improve the quality of education at the Institute.
Keywords: quality, distance technologies, academic performance, control card, alternative attribute
The results of the studies show that the manufacturer of composite materials for the consumption of reinforced concrete structures depends and produces materials for reinforcement, material properties and their quality. Such a thing requires the study of properties, fixing in the structure of materials. The article is devoted to the appeal. A program has been specially developed for influencing structures with unexplored, but the most popular composite materials in Russia, in particular, in the Rostov region. Certain parameters of reinforced structures that will be checked during the testing process. The program of the experiment was designed in such a way as to capture the most important reinforced concrete structures used in construction.
Keywords: concrete, reinforced concrete, composite material, carbon fiber reinforced plastic, external reinforcement, deformations, compressed elements
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
In the production of petroleum products, the study of IR absorption spectra is most often used to analyze the properties of a mixture. The priority of this method is due to the fact that the characteristics of the IR spectrum are directly related to the nature (structure and chemical composition) of the absorbing substance, and also depend on the aggregate state of the substance, temperature, pressure, etc. The unambiguity of the relationship between the molecular structure of a substance and its IR spectrum allows us to determine the composition of the mixture. For this purpose, calibration models should be built that connect the IR spectrum with the value of the quality indicators of petroleum products. The paper considers the methods of creating calibration models proposed by various authors, presented in well-known literary sources. To create calibration models in this paper, it is proposed to use the method of principal components and neural network modeling. Also, in order to increase the reliability of the automated control system for compounding motor fuels, it is proposed to use virtual analyzers (VA) of quality indicators of communication models, the quality indicator calculated from the calibration models of the flow analyzer with the corresponding technological variables of the compounding process. The output of the calibration models is also used for adjusting the VA.
Keywords: Oil refining, IR spectrometer, quality indicators of petroleum products, flow IR quality analyzer, calibration models of the analyzer, virtual quality analyzer
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
The article discusses the use of mathematical modeling of the transmission of a car in the Simulink environment. Studies of the influence of individual transmission factors on the functional parameters of the KAMAZ 4308 car have been carried out. Differential equations describing the operation of the transmission are solved in a matrix way, allowing to study the dynamics of the car taking into account the moments of inertia of the engine, transmission and individual wheels of the car.
Keywords: transmission, wheeled vehicle, clutch, differential, gear ratio, simulation, maximum speed