Статьи журнала - Siberian Aerospace Journal
Все статьи: 387
The method of the automation of the plasmotron movement by six-axis robotic manipulator
Статья научная
The article presents a method for automating the creation of trajectories of the plasmotron movement by a six-axis robotic manipulator. The automation system was created on the basis of an industrial robot from KUKA. The automation of the creation of trajectories of the plasmatron over the surface of the part is implemented as follows: the trajectory of the plasmatron is created in a graphic editor in the .dwg format. The created file is loaded into the CAM program for CNC machines. A CAM program converts a vector or an area specified by vectors into a control command in g-code format, which is then converted to KRL by a program written in the Python programming language. The development of the program consisted of two stages: the creation of rectilinear movements and the creation of curvilinear movements. The result of the method is presented.
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The method of the disk friction determining of low mass flow centrifugal pumps
Статья научная
Low mass flow centrifugal pumps are currently widely used in the energy supply system of liquid rocket engines, the engines of correction, docks, consisting of on-Board power sources on-Board sources power supply system of fuel components in the in gas generator systems for inflating fuel tanks, and in temperature control systems of aircraft and spacecraft. When designing low mass flow centrifugal pumps for aerospace purposes, methods for calculating and optimizing the flow rate are often used corresponding to the design methods of full-size centrifugal pumps, which limits the mode and design potential of pumps and affects their energy characteristics and reliability. Reliability requirements often lead to the need to reserve units and fuel-supply systems. Despite the large amount of research works, the issues of reliable design of low mass flow centrifugal pumps with high energy and operational parameters for spacecraft and aircraft remains an urgent task. The article analyses the operational parameters of low mass flow centrifugal pumps used in aircraft and spacecraft power systems. Taking into account working fluid used and the temperature range, it was found that a laminar rotational flow with Reynolds number characteristic Re 103 3105 is realized in the lateral cavity between the impeller and the pump housing. The determination of power losses on disk friction of the impeller technique is developed taking into account design features and the applied schemes. Equations for determining the disk friction coefficients are consistent with the dependencies obtained by other authors. The obtained equations for the laminar rotational flow made it possible to determine the dependences for the resistance moment and the disk friction power of the impeller determining of a low mass flow centrifugal pump.
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The possibility of using methane-hydrogen fuel in converted gas turbine engines for power plants
Статья научная
Taking into account the fact that recently the topic of using methane-hydrogen mixtures as a fuel for gas turbine engines used in power plants has been actively developed, it is necessary to have engineering methods for calculating the fuel system and combustion chamber of engines operating on such fuel. The paper proposes the methodology that allows performing such calculations. A gas turbine unit (GTU) based on a converted aircraft engine NK-16ST was taken for the calculation. The calculation according to this method is carried out in three stages. At the first stage the composition is selected and the thermophysical characteristics of the gas under consideration are determined. At the second stage the fuel system is calculated, the consumption characteristics of the engine fuel system and the combustion chamber system are built. The consumption characteristics built for natural gas and for methane-hydrogen mixture are compared. The analysis makes it possible to develop recommendations for optimizing the design of the fuel supply equipment and fuel nozzles in terms of changing the volume of internal channels. At the third stage the combustion chamber is calculated and recommendations about the need to change the flame tube head or redistribute air along the flame tube length are made. The volumetric heat intensity parameter is used to estimate the sufficiency of the available volume of the flame tube for operation on methane-hydrogen mixture and to determine the gas average temperature in the combustion zone of the combustion chamber. The possibility of operation of the NK-16ST gas turbine unit on a methane-hydrogen mixture was confirmed on the basis of the results of the work performed. It was also concluded that in order to supply large volumes of methane-hydrogen mixture in comparison with natural gas, it is required to increase the size of fuel pipelines, metering and control units and fuel nozzles.
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The process of nanomodifying cast aluminum alloy ingots for components of aerospace vehicles
Статья научная
Currently, increasing attention has been paid to such a class of materials as nanopowders (NP) of chemical compounds, which are ultra-thin formations of not more than 100 nm in size. Such attitude to these materials is explained by the fact that they have unique physical, chemical and mechanical properties significantly different from the properties of materials of the same chemical composition in a massive state, and these properties can be transferred to some extent from them or with their participation to the products. The existing methods of introducing NP into metal melts could not be used due to their special properties in comparison with coarse powders, and therefore a new method of their introduction into the melt was developed, excluding direct contact of NP particles with oxygen and unhindered penetration of particles into the melt through the oxide layer. The essence of the method was as follows. In the aluminum container filled up with aluminum particles or deformable aluminum alloys D1 or D16 and various NP (nitrides, carbides, oxides, etc.), and this composition was pressed into the rod, with its help NP was introduced into the melt during casting of aluminum ingots and deformable aluminum alloys. The results of the study showed that this excludes the appearance of cracks in the ingots, as well as improves their technological and mechanical properties.
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Статья научная
Today, protective coatings are applied to almost all parts and components of engineering products in order to ensure high performance properties of machines, with the lowest economic cost. The method of plasma spraying allows to apply heat-resistant coatings on a different kind of basis, in addition to a wide variety of materials. Therefore, rocket and space engineering is primarily interested in the method. In modern conditions of high rate of mechanical engineering development engineers must develop and put into operation products within the shortest possible period of time. As a rule, engineers select the modes of plasma spraying using the method of selecting the empirical relationship between the properties of the coatings and the values of the specified parameters of plasma spraying, which suggests conducting a huge number of experiments. That is why we see the need to find new methods for selecting the plasma spraying parameters, which are based on mathematical and analytical apparatus. We set the task to study and show the applicability and prospects of the proposed method. In the work we carried out the operations of spraying nichrome coating, at different values of the arc current. We studied the adhesive strength of the coatings obtained and their microstructure. We showed the relationship between the arc current and the adhesion of the coatings using their microstructure. These studies have made it possible to exclude a large number of experiments, which usually establish an empirical relationship between the values of the input parameters of the deposition process and the values of the characteristics of the coatings obtained. In the future, we assume that the database of such relationships will make it possible to fully use this method in engineering industries.
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Статья научная
The most important resource for improving the performance of parts is the reduction of the surface roughness. One of the promising ways to reduce the surface roughness is the abrasive extrusion processing. When developing the AEP technology, it is necessary to know the flow rate (pressure) of the WE, which depends on the viscosity of the latter. In turn, the viscosity of the WE is determined by its temperature. The temperature of the working environment at AEP can be calculated if the coefficients of thermal conductivity and thermal diffusivity of the WE are known. The working environment for AEP consists of two components, therefore, the coefficient of thermal conductivity can be calculated by known formulas. However, the calculation error is significant, therefore, the experimental determination of the abovementioned coefficients is required. The installations for the coefficients research have been presented, the methods of conducting experiments have been developed. After mathematical processing of the experiments results by means of the AdvanceGrapher v. 2.11, the dependences of the thermal conductivity and thermal diffusivity on the abrasive concentration have been obtained. The studies of the thermophysical properties of the working environment have shown that the values of thermal conductivity and thermal diffusivity of the WE are mainly determined by the concentration of abrasive grains in the working environment. The direct dependence of these coefficients on the degree of filling the working environment with abrasive grains has been established.
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Статья научная
Electrical discharge machining and electrochemical machining of metals are used in the production of parts for aircraft and rocket technology, especially electrical discharge machining. A type of electrical discharge machining, electrical contact machining, is used in metallurgy. The paper investigates a combined method of metal machining, including electrical contact and electrochemical methods using vibration of the electrode tool. This method is used for copying and piercing operations in the manufacture of parts from metals that are difficult to machine mechanically. The peculiarity of the above-mentioned method of electrical machining is the formation of surface roughness of the metal being machined due to anodic dissolution and the electrical discharge machining process. The side surface of the workpiece is formed due to electrochemical processes. The end surface is formed due to electrical contact machining. Based on literature data for pulsed electrochemical machining and experiments, expressions for calculating the roughness parameter of the side surface are obtained. The formula takes into account the time of anodic dissolution for one period of oscillation of the cathode tool, the voltage on the electrodes and the concentration of the electrolyte. The calculation of the roughness parameter of the end surface is carried out similarly to the expression for electrical discharge machining, but instead of the duration of the electric pulse, the duration of contact of the electrodes is used. The experiments carried out confirmed the correctness of the expressions used and made it possible to obtain the dependence of the coefficient on the vibration frequency of the cathode-tool.
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Статья научная
A mathematical model describing the dynamics of a resonant converter with a T-shaped oscillatory circuit in the mode of power supply from a current source, which is a simplified model of a solar battery, is analyzed. It is shown that increasing the output filter capacity to improve the quality of transients is an ineffective measure. As an alternative measure, it is proposed to supplement the output circuit of the converter with an additional low-pass filter. A linearized equivalent circuit of the upgraded converter has been developed. It has been found that the quality of the transients of the input and output circuits of the converter is practically independent of the inertial properties of the converting T-shaped oscillatory circuit due to the fact that the time constant of the input and output filters is much greater than the constant of the rise time of the circuit current. It is shown that the device in question is a current-to-voltage converter not only in statics, but also in dynamics, and the equivalent circuit of the input circuit of the converter, without taking into account the input filtering capacity, is described by an electrical circuit that is dual to the output circuit of the converter. The developed equivalent circuit makes it possible to increase the speed of computer simulation of transient processes in the converter tenfold. The adequacy of the proposed approach is confirmed by modeling the transients of a resonant transducer in the Matlab 2021b software package. It has been found that the use of an additional low-frequency output filter significantly reduces the time of transients, reduces the amplitude of the input voltage transition, and also improves the mass-dimensional characteristics of the converter.
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Статья научная
Today, the scope of application of electric propulsion systems for orbit correction and spacecraft’s attitude control is rapidly expanding due to their high efficiency compared to liquid jet systems. The main elements of electric jet systems are plasma or ion thrusters. To ensure power supply of such thrusters, complex electronic power processing systems – power processing units (PPU) – are used. These units are capable to operate for a long time (up to 15 years or more) in a high vacuum environment and generate sufficiently high accelerating voltages – from 300 V and higher. PPU’s comprise various EEE-parts, mainly in the case design. As a rule, the technology of their production is such that air or nitrogen is initially located inside the housing at atmospheric pressure. During the operation of the unit, the non-absolute hermeticity causes pressure decrease inside EEE housings. Due to high voltages applied, this can lead to electrical breakdowns between current-carrying ele-ments inside the parts, their failure with the subsequent failure of the functional blocks of the unit. The paper considers the physical principles of the breakdown occurrence inside EEE-parts cases. The results of non-hermiticity measurements of several types of HV EEE-parts are presented. The dynamics of the pressure drop to the values dangerous from the point of view of breakdown event and the relevant occurrence duration are esti-mated. It is shown that duration of being exposed to the pressure-dangerous conditions can be as long as space-craft service lifetime. It can make difficult to use packaged gas-filled EEE-parts at the level of units intended to operate in non-pressurized compartments of spacecraft. Recommendations are provided for selecting the design of EEE parts with an operating voltage of about 300 V or more, as well as circuit solutions used to develop high-voltage equipment intended to operate in vacuum environment.
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Статья научная
The rapid development of electric-powered aircraft (with electric and hybrid power plants, including unmanned ones) is determined by the following advantages: reduction of harmful effects on the environment, reduction of noise exposure, reduction of maintenance costs. However, the development of such aircraft is hindered, in addition to organizational and legal difficulties, also by technical ones, the key of which are: low power-to-weight ratio of the aircraft (compared to piston and jet aircraft), electrification, underdeveloped infrastructure of airports and airfields. One of the options for solving the problem of increasing the power and energy efficiency of an unmanned aerial vehicle (UAV) with electric traction is the installation on board of a chemical-kinetic energy storage (rotating battery packs), with the possibility of using static electrification to recharge batteries. This system allows you to implement a continuous consumption / recovery cycle during the flight. The design was developed and a simplified assessment of the energy and technical characteristics of a promising UAV based on the selection of static electricity was given. The principle of operation of the static electricity extraction system based on rotating battery packs is shown, the main advantages over traditional systems of energy storage / recovery of aircraft are given. The results of the calculation and research of a prototype (a promising unmanned aerial vehicle) are presented, showing the versatility of the design, high operational and technical characteristics, as well as recommendations for the practical application of the developed UAV design. The results obtained are the initial stage of promising work to improve unmanned aerial vehicles and electric-powered aircraft systems. The low weight and size characteristics, as well as the unusual principle of operation of the static electricity extraction system based on a rotating battery packs allows it to be used as an autonomous power source for unmanned aerial vehicles, which allows in the future to extend this principle of energy consumption for any electric-powered aircraft. This work is an important stage in the development of highly efficient power plants operating on unconventional principles of energy production, which, on the one hand, expands the field of research of storage/ recovery/ consumption systems in modern aircraft construction, on the other hand, gives a powerful impetus to the development of engineering and scientific thought in the field of unmanned aircraft construction.
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The use of the inverse transformation method for time series analysis
Статья научная
In modern conditions of technology development, signs of systemacity are manifested to one degree or another in all areas, so the use of system analysis is an urgent task. In this case, the main factors in this situation are data processing and prediction of the state of a system. Mathematical modeling is used as a prediction method for a given subject area. A mathematical model is a universal tool for describing complex systems representing the approximate description of the class of phenomena of the external world expressed by mathematical concepts and language. The mathematical model can be represented as a set of systematic components and a random component. In this article, the object of prediction is the irregular random component of a model, which reflects the impact of numerous random factors. The origin, nature and laws of variation of the random variable are known, therefore, to simulate its behavior or predict its future value, one needs high degree of certainty to establish the form of continuous distribution function of the random variable. The empirical distribution function is calculated using the sample of random variable values. This empirical function is close to the values of the desired unknown function of distribution. The resulting empirical function is discrete, therefore it is necessary to apply piecewise linear interpolation to obtain a continuous distribution function. The predicted random component of time series has been included in the initial regression model. In order to compare augmented and initial regression models, several values were excluded from the time series and new prediction was built. The value of the average approximation error for assessing the quality of the model is calculated. The augmented regression model proved to be more effective than the original one.
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Thermal emission and pyroelectric current in manganese chalcogenides
Статья научная
Manganese chalcogenides, which are promising for the manufacture of thermoelements, are being studied. The current is measured in the temperature range of 80–500 K, in the absence of external voltage, which can be caused by a temperature gradient (thermopower), a change in electrical polarization (pyroelectric current), piezoelectric current (when the sample is deformed, a potential difference arises) or thermionic emission (thermal emission current) . Temperatures of current anomalies and their relationship with thermionic current and polarization current are found. A change in electrical polarization with temperature will cause a pyroelectric current. Compensation for excess electrical charge will result in local electrical polarization. Partial decompensation will cause the formation of an electric field in the sample. The critical temperatures for the disappearance of electric polarization were determined for different concentrations. In the region of concentration of thulium ions flowing through the lattice, the activation nature of the thermionic current was established and the activation energy was found. The pyroelectric current has a smaller value compared to the thermionic current. The current mechanism is determined by the emission of electrons from deep traps and the temperatures of the maximum thermionic current correlate with the temperatures at which IR absorption disappears. The electric current density and its value depend on the type of substituted rare earth element are calculated.
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Three-component aerodynamic load cells
Статья научная
The article examines the effect of flow on models studied in wind tunnels. To determine the force effect of the flow on the model under study, a more accurate and reliable method of directly measuring forces and moments using aerodynamic strain gauge balances is proposed. When solving a plane problem for a symmetrical model at zero slip angle, a design of three-component scales is proposed that measures the lift force, the drag force and the pitching moment. To eliminate the interaction between the supporting devices and the model, which causes disturbances in the flow near the model, the scales are located outside the model and the working part of the wind tunnel. The components of the aerodynamic force and moment acting on the model are measured using resistance strain gauges, which convert the deformation of the elastic element into a change in electrical resistance, which is measured by an instrument connected to an appropriate measuring circuit. The choice of strain gauges as weight elements is due to their very small size and weight, the ability to measure very small relative deformations of elastic elements, low inertia, which makes it possible to measure not only static but also dynamic loads, and the possibility of remote measurements. To compensate for the influence of various sources of errors, increase sensitivity and ensure greater measurement accuracy, the strain gauges are connected via a bridge circuit and included in all four arms of the bridge. Deformation of the horizontal measuring beam causes a change in resistance not only in the strain gauges that measure the pitching moment, but also in the strain gauges designed to measure the lift force. Since the design of the scales does not allow for electrical separation of these components, the influence of the pitching moment on the magnitude of the lift force is determined during the calibration process and is assessed using a special influence graph constructed from the results of calibration data. In strain gauge measurements, the output values of forces and moments acting on the model under test are obtained in the form of corresponding readings from a device that measures electrical signals proportional to the applied forces. To convert instrument data into values of forces and moments, a joint calibration of scales and instruments is carried out in order to obtain calibration coefficients. Additional components of aerodynamic forces and moments created by the holder are determined by purging it in the presence of the model. Calculated dependencies for determining the components of the aerodynamic impact are given. The values of the coefficients of aerodynamic forces and moments are given in the flow coordinate system. The pledge has been given.
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Статья научная
Ensuring high reliability of unique high-critical products at the design stage is an actual task that the aerospace industry faces. For high reliability indicators, at the design stage, it is necessary to ensure the basic property of the product – its strength, with a high probability of non-destruction. It is provided by introducing the corresponding coefficients – «safety coefficient» and «margin of safety» into the strength calculations. The necessity in these coefficients is based on the spread of values of external loading factors: magnitude of forces, combination of forces, kind of actions, place of connection, etc. In this case, the safety coefficient is related to external factors. The margin of safety refers to internal factors: the spread of the mechanical characteristics of the product material, the spread of the geometric dimensions of the product, etc. To determine, with a given probability, the safety coefficient and margin of safety, it is necessary to know their dependence on the combination of spread of external and internal factors. The purpose of this work is to determine the mathematical connection between the internal factors of the spread and the safety coefficient, external factors of the spread and the margin of safety, the combination of these factors and the probability of non-destruction of structures. In this work the values of internal and external factors, which affect the strength and probability of non-destruction of the product and have the boundaries of the spread of their values, using the tools of probability theories, were characterized as random variables, the values of which are determined by the distribution density, expected value and variance. I this work there was found a high dependence of the product strength on the spread of its geometric characteristics and tools were defined to determine the total spread of the values of the main strength characteristics of the product with a given probability of non-destruction. The practical significance of the results of this work can be achieved in the aerospace industry, in particular, at the design stage of unique high-critical products.
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To the question of forecasting the technical condition of low-thrust liquid rocket engines
Статья научная
In the rapidly developing space and rocket industry, spacecrafts are being equipped with low-thrust liquid rocket engines. Нigh requirements are imposed on the reliability, efficiency and economy of fuel use for this type of rocket engine. To ensure monitoring of the characteristics of spacecrafts, a functional diagnostic system is used, which includes telemetry and analytical data processing. Telemetry performs the functions of receiving and transmitting information. Information processing is carried out in computer centers located on the spacecraft and the Earth. The most promising computing tool capable of predicting time series and classifying a large amount of interconnected data is considered an artificial neural network. In this regard, the subject of research in the work is data processing methods based on an artificial neural network. The purpose of the work is to develop a method for forecasting the technical condition of low-thrust liquid rocket engines using an artificial neural network. The relevance of research on the use of a neural network in the system of functional diagnostics of low-thrust liquid rocket engines for spacecraft is explained in the introduction. In the main part, an analysis of many telemetric data of the rocket engine is carried out and their strength in the forecast of the main diagnostic parameters is determined. It is proposed to use traction, specific impulse, and temperature of the structure as diagnostic parameters. The prognostic capabilities of the neural network were investigated and a schematic diagram of a method for predicting the technical condition of a low-thrust liquid rocket engine was developed. In the developed method, at the first stage, the neural network performs the approximation of the function and extrapolates the time series of telemetric data; the second stage determines the probable class of the technical condition of the engine. The conclusion outlines a plan for further experimental research in the study area and provides recommendations on the development and improvement of algorithms for functioning of artificial neural networks as part of the functional diagnostics system of the spacecraft. Due to the generalized nature of the methodological schemes, the results of the work can be applied to any type of rocket engines and used at all enterprises of the rocket and space industry of the corresponding profile.
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To the task of controlling a group of objects on the basis of information technologies
Статья научная
To participate the TPP with cross-section communications in the general primary frequency control, it is necessary to have a working main regulator. The main regulator is designed to maintain the steam pressure in the major steam line of the TPP at a given level, which is a difficult task. At the TPP with cross-connections, the steam produced by the boilers enters the major steam line. To maintain the pressure in the major steam line, it is necessary to control the heat load of the working boilers. Traditional solutions to construct the main regulator found no use, as have a number of disadvantages, not allowing exploiting a system of automatic control. Looking at the steam pressure control system in the major steam line from the bottom to up, it is possible to identify disadvantages that prevent the effective operation of the main regulator at each level. At the lower level of the main regulator, there are controllers of heat load of boilers, built according to the scheme task-heat. Heat load controllers are designed to maintain heat release in the boiler furnace at the required level. The heat signal is the sum of the signals for the steam flow of the boiler and the rate of change in the steam pressure in the boiler drum. Such a structure does not allow maintaining the invariance of the heat signal under external disturbances effectively, as sharp changes of the steam pressure in the major steam line lead to a "false" operation of the controllers. At the upper level there is the main regulator itself, which maintains the steam pressure in the major steam line at a given level and corrects the tasks to the controllers of the heat load of the boilers. The simultaneous identical effect on the heat load of the boilers cannot be optimal from the point of view of the criteria for assessing the quality of regulation, since the dynamic properties of the boilers, such as the gain, the transition time constant and the transport delay are individual for each boiler. However, in 2006–2008, the attempt to build an updated main regulator that takes into account the shortcomings of the traditional scheme was made. The basis of the structure of the main regulator is still parametric and, as a result of ten-years’ experience, shortcomings in the operation of the updated main regulator were identified. The shortcomings, in most cases, consist in need of frequent corrections of adjusting coefficients of system because of the change of dynamic properties of an object during the operation. In fact, the same problems related to the parametric structure of the regulator remain. Up-to-date information technologies made it possible to introduce adaptive process control systems that allow to count an extended number of signals entering the system and to form control actions, based on both current and historical data of the technological process. The use of the latest information technologies and modern hardware in the control of complex multi-connected units that solve not only the problems of process control, but also the problem of improving the economic and environmental performance of enterprises, should become a new step in the development of automatic control systems.
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Torsion of prismatic orthotropic elastoplastic rods
Статья научная
Conservation laws were introduced into the theory of differential equations by E. Noether more than 100 years ago and are gradually becoming an important tool for the study of differential equations systems. Not only do they allow you to qualitatively investigate the equation, but, as the authors of this article show, they also enable you to find exact solutions to the boundary value problems. For the equations of the iso-tropic theory of elasticity, the conservation laws were first calculated by P. Olver. For the equations of the theory of plasticity in the two-dimensional case, the conservation laws were found by one of the authors of this article and used to solve the main boundary value problems of the plasticity equations. Later it turned out that the conservation laws can also be used to find the boundaries between elastic and plastic zones in twisted rods, bent beams, and deformable plates. The proposed work found conservation laws for equations describing the orthotropic elastic state of the twisted straight-line rod. It is assumed that the remaining current depends linearly on the voltage tensor component. In the workit was also found an endless series of laws of preservation, which allows you to find an elastic-plastic boundary, which arises when twisting the orthotropic rod.
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Turn of an elastic-plastic rod under pressure that varies linearly along the forming
Статья научная
The article continues a series of articles devoted to the use of the method of conservation laws of differential equations for solving problems in the mechanics of deformable solids. Elastoplastic problems in the mechanics of a deformable solid take into account the nonlinear relation-ship between stresses and deformations under the influence of various loads. Such problems arise in structures where materials are characterized by different physical properties; taking into account elastic-plastic deformations is important for predicting the operation of structures, as well as for ensuring their durability. Currently, solutions to elastoplastic problems continue to be the focus of researchers' attention. New analytical approaches to solving these problems are emerging, and numerical methods are being improved. The authors contribute to solving the problems of mechanics of deformable solids using conservation laws. The use of conservation laws makes it possible to reduce the finding of the stress tensor components at each point to a contour integral along the boundary of the region under consideration, which makes it possible to construct a previously unknown elastoplastic boundary. The article considers an elastoplastic rod of constant cross-section, which is under the influence of li-near hydrostatic pressure and a pair of forces that twist it around a central axis coinciding with the oz axis. The lateral surface of the rod is stress-free and in a plastic state. The constructed conservation laws allow us to find the components of the stress tensor. The components of the stress tensor make it possible to determine the elastoplastic boundary in the rod under consideration.
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Статья научная
Autonomous navigation is very important in many fields and applications and it specifically depends on global positioning system (GPS) measurements which may not be accessible in some areas. This will directly affect the autonomous navigation and sequentially this will lead to problems according to the function of autonomous navigation. In this research, generalized regression neural network (GRNN) which is a variation to radial basis neural networks, was used to compensate global positioning system (GPS) measurements in case of GPS absences to increase accuracy of autonomous navigation parameters (basically location and velocity) of object. GRNN is integrated with loosely coupled Extended Kalman Filter (EKF). Location, velocity, orientation parameters and biases of sensors are estimated. The evaluation of this methods was conducted using dataset from Internet, two simulations for the GPS measurements outages were made (first outage periods were 35 and 60 seconds) to evaluate the behavior of GRNN, the results shows that using GRNN in GPS absence is effective and robust, it outperformed the only loosely coupled EKF method.
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Using of the contour method to solving the problem of optimal traffic distribution in the network
Статья научная
The purpose of this work is to create a method for solving the problem of optimal traffic distribution in a network using the contour data analysis method. In the first section of the work, the principle of converting any available network to a contour form is explained, and the case is considered both for networks without loss and for networks with losses. The second section shows in a general way the method of bringing the network in contour form to a system of non-linear inequalities, by solving which one can obtain a certain distribution of traffic in the system. In the final section, using the M/M/1/N queuing system as an example, the solution of the problem of optimal traffic distribution according to the loss minimization criterion is shown. The initial data for the task were the incidence matrix, service intensity and buffer dimension for communication channels. A feature of the proposed algorithm is the search for a contour matrix, for the compilation of which it is proposed to use loss edges as elements of the spanning tree of the graph, which allows you to immediately determine the contour matrix using the concept of a fundamental cycle of a graph. This approach to optimal traffic distribution reduces the number of variables used compared to the known methods based on loopless routes, and also does not require their preliminary search, since they are determined from the dimension of the incidence matrix of the simulated network graph.
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