Статьи журнала - Siberian Aerospace Journal
Все статьи: 363
Статья научная
If a system of differential equations admits a group of continuous transformations, then the system can be represented as a set of two systems of differential equations. As a rule, these systems have a smaller or-der than the original system. The first system is automorphic, characterized by the fact that all its solutions are obtained from a single solution using transformations of this group. The second system is permissive, its solutions, under the action of the group, pass into themselves. The resolving system carries basic infor-mation about the source system. Automorphic and resolving systems, two-dimensional stationary elasticity equations are studied in this work. They are systems of the first-order differential equations. Infinite series of conservation laws for a resolving system of equations and an automorphic system are constructed for the first time in this work. Since the two-dimensional system of elasticity equations is linear, there are infinitely many such laws. In this paper, an infinite series of linear conservation laws with respect to the first derivatives is constructed. It is these laws that made it possible to solve the first boundary value problem for the equations of elasticity theory in the two-dimensional case. These solutions are constructed in the form of quadratures, these quadratures are calculated along the contour of the studied area.
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Constraint handling genetic algorithm for feature engineering in solving classification problems
Статья научная
Feature engineering in machine learning is a promising but still insufficiently studied direction. Creating new feature space from an original set allows to increase accuracy of the machine learning algorithm chosen to solve complex data mining problems. Some existing selection methods are capable of simultaneously increasing accuracy and reducing feature space. The reduction is an urgent task for big data problems. The paper considers a new machine learning approach for solving classification problems based on feature engineering methods. The design of informative features is carried out using extraction and selection methods. Based on the initial data, new sets of characteristics have been created, which include the original characteristics and characteristics obtained by the method of principal components. The choice of an effective subset of informative features is implemented using a genetic algorithm. In order to avoid overfitting and the creation of trivial classifiers, restrictions are imposed on the fitness function of the genetic algorithm, requiring a certain number of features of the original sample, as well as a certain number of features obtained by the principal component method. A comparative analysis of efficiency of the following classification algorithms is carried out: k-nearest neighbors, support vector machine, and a random forest. Efficiency research experiments are carried out by solving applied binary classification problems from the UCI Machine Learning repository of machine learning problems. The macro F1-score was chosen as an efficiency criterion. The results of numerical experiments show that the proposed approach outperforms the solutions obtained using the original data set and the performance of random feature selection (the low bound for the results). Moreover, the accuracy enhancement is obtained for all types of problems (data sets that have more features than values). All results are proved to be statistically significant.
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Construction of high-precision low-dimensional MgFE using local approximations and generating FE
Статья научная
Composite structures (bodies), in particular, plates, beams, shells, are widely used in aviation and rocket and space technology. To analyze the stress state of elastic composite bodies (CB), the method of multigrid finite elements (MMFE) is effectively used, which is implemented on the basis of the Lagrange functional (in displacements). When constructing a multigrid finite element (MgFE), briefly a standard MgFE, using known procedures, a small base grid is used, which can be arbitrarily small, and large ones nested in a small one. The fine grid is generated by the partition of the MgFE, which takes into account its inhomogeneous, micro-inhomogeneous structure within the framework of the micro-passage. Large grids are used to reduce the dimension of the MgFE. The following is typical for a standard MgFE. Any large grid of a standard MgFE and corresponding approximations of displacements are determined on its entire region. This leads to an increase in the dimension of the standard MgFE with an increase in its order of accuracy, since in this case approximations of high-order displacements are determined on large grids. To reduce the error of solutions, high-precision MgFE are used, i. e., of a high order of accuracy, which have a large dimension. However, the use of high-precision MgFE is difficult, since they form discrete models of high-dimensional bodies. In this paper, we propose a method of local approximations (MLA) for constructing high-current MgFE of small dimension (short - small-sized MgFE), which are used to calculate elastic homogeneous and CB by MgFE. Two types of small-sized MgFE are considered. Small-sized MgFE of the 1st type are designed on the basis of standard ones with the use of local approximations of displacements, which are determined on the subdomains of standard MgFE, of the 2nd type - with the use of finite element generators (FE). The brief essence of the construction of small-sized MgFE of the 1st type is as follows. According to the MLA, we define a smaller Н grid on the V0 region of the standard MgFE than its base one. The V0 region is represented by the boundary and inner regions. The boundary (inner) regions have a common boundary, which does not degenerate into a point (do not have a common boundary), with the V0 region. On the boundary (inner) regions, we define large grids that are embedded in a small Н grid and generate local approximations of small (high) order displacements. On the V0 region, using local approximations of the displacements of the boundary and inner regions, we construct the MgFE. Then, using the condensation method, we express the movements of the internal nodes of the MgFE through the movements of the nodes lying on its boundary, i.e. on the boundary of the V0 region. As a result, we obtain a high-precision Vp MgFE of small dimension, i.e. a small-sized MgFE of the 1st type, the dimension of which is equal to the dimension of the standard one. It is important to note that with an increase in the order of accuracy of the Vp MgFE, its dimension does not change, i.e. it does not increase, and therefore it is called a highprecision MgFE of small dimension, i.e. small-sized. The procedure for constructing small-sized MgFE of the 1st type is described in detail. As is known, the calculation of the static strength of structures is reduced to determining the maximum equivalent stresses for them, the determination of which with a small error for CB is an urgent problem. Calculations show that small-sized MgFE of the 1st type generate maximum equivalent stresses in CB, the errors of which are 25 50 smaller than the errors of analogous stresses obtained using standard ones, on the basis of which small-sized, i.e. small-sized MgFE of the 1st type are more effective than standard ones. The use of small-sized MgFE of the 1st type in MMFE calculations makes it possible to determine the maximum equivalent stresses with a small error for large CB partitions. The construction of small-sized MgFE of the 2nd type is shown, which are designed on the basis of standard high-precision MgFE with the use of generating FE. A small-sized MgFE of the 2nd type has the same order of accuracy as the standard one, but its dimension is smaller than the dimension of the standard one. The advantage of small-sized MgFE of the 2nd type is that they give rise to discrete CB models of smaller dimension than standard ones.
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Contact algorithm measurement method for current crystals area grown by Czokhralski method
Статья научная
For crystals grown from the liquid melt according to the Czochralski method when monitoring and controlling the current crystal area based on the contact measurement method, the requirements for improving the accuracy of measuring the crystal area on the cylindrical part of the growth are determined. To eliminate errors due to the accuracy of stabilization of the melt level in the crucible, an algorithm for the operation of the crystal growing unit is proposed which is performed by the programm using the control system. The evaluation time of the control signal on the growing crystal cylindrical part is taken as the sampling time of a given number of crucible movement pulses. The calculation of the control signal starts at the time of the melt level sensor closure, the calculation of the control signal ends at the time of the melt level sensor closure as well, provided that a given number of crucible movement pulses is sampled. The control signal evaluation time in the previous control cycle is used in the current cycle to calculate the melt level sensor closing and opening pause. In the control system at the moment of the contact sensor closure a pause of the closed and the same subsequent pause of the open state of the level sensor is held. During pauses, the status of the contact sensor is not analyzed by the control system and the control of the crucible ascent occurs at a slowed down and accelerated rate of the crucible ascent during “conditionally” closed and “conditionally” open states of the level sensor. The control system is permanently reset at the end of each control cycle. The program control system provides the above algorithm for controlling the process of growing crystals from the liquid melt according to the Czohralski method, at the same time the accuracy of determining the current area of the grown crystal is about 1 %.
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Control and regulation equipment of electric power system for a prospective piloted transport system
Статья научная
The aim of this work is to consider solving complex of tasks focused on fulfilling the complicated tactical and technical requirements for regulation and monitoring equipment (RME) of electric power supply system (EPS) for a prospective spacecraft. These requirements are imposed due to the need to ensure high reliability of the equipment during operation under the influence of external factors (vacuum, vibro-impact loads, radiation, absence of convective cooling), as well as to achieve high mass-dimensional parameters of the equipment and its high functionality The complexity of problem solving lies in the need to ensure conflicting requirements – high levels of energy density, weight and size characteristics, reliability and durability. These problems fully apply to the RME of the EPS for a prospective piloted transport system (PPTS) which design example shows ways of solving abovementioned problems. The most rational way of solving these contradictions is to increase the specific energy indicators of the main components of the RME devices – power converters, which can be achieved by using modern power electronic elements, using new materials and semi-finished products, for example, printed circuit boards with a metal heat sink, as well as increasing the layout density design. Determining solution is to select an optimal structure of the power converter, which provides the best efficiency. An additional way to reduce the mass-dimensional indicators of the RME is the use of a digital control method, the collection of telemetric information, and the receiving and processing of commands. At the same time, on the contrary, to ensure the specified reliability of the equipment, it is necessary to use excess reservation at the element level – for power components, and the principles of majority reservation at the functional block level – for control and telemetry schemes. Using the example of RME, developed by CJSC “Orbita”, the main EPS parameters of a new generation spacecraft are shown and most important power supply subsystems are considered in the article: the solar energy control subsystem and the power storage subsystem, ways to build them for meeting specified requirements, taking into account the proposed solutions. As a result of this work, the optimal structures of power converters – the current regulator of the solar battery and the current regulator of the battery – were selected, the basic principles of power components reservation ensuring the operability of the equipment in case of a single failure of any component without loss of performance and deterioration of RME parameters as a whole are shown. Block-modular construction method is used for optimal layout and high reliability of the RME, it ensures uniform heat removal from electronic components, which is especially important in vacuum conditions, minimum dimensions and mass optimization of the RME, as well as high mechanical strength of the structure. The implemented principles of building the RME for PPTS using this approach will allow to increase the active lifetime (ALT) and reliability of the spacecraft with a simultaneous decrease in mass and dimension parameters.
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Статья научная
In this paper, we consider the concept of using methods for calculating and designing rocket engine power plants for conversion modeling of local energy in the Arctic and northern regions of the Kras-noyarsk Territory, with an obvious generalization to neighboring administrative formations with similar climatic and structural and logistical conditions. The proposed structure contains power generation units linked to both industrial woodworking waste and natural and industrial thermal tails, identified as sources of low-potential heat, as well as modern low-power reactor plants of block maintenance-free design. The unifying element of power plants is a turbo generator, designed with the use of unconventional, often waste and natural low-grade heat.
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Статья научная
The known methods of treatment of wastewater generated in rocket and space technology production using electroplating technologies do not allow to ensure the maximum permissible concentration of metal ions in treated water, or are expensive or difficult to operate. The general toxic, embryotropic and muta-genic effect of metals is well studied. These metals, getting together with water to food products in living organisms, are able to accumulate in them, causing the pathogenesis of heart diseases, brain, liver, and cancerous tumors in people. Iron ions are part of wastewater of most industries, which requires increased control and development of effective methods of wastewater treatment. The article presents a technique for conducting experiments, a method of combined water purification, including electrochemical action and adsorption, is considered. The results of studies of this method of wa-ter purification from iron ions are presented. The dependence of the degree of purification on the specific amount of electricity passing through the purified water, the strength of the electric field and the settling time is revealed. With Qav = 4.7 Kl/l, E = 1058 V/m, using quartz sand as an adsorbent and settling time for 24 hours, the concentration of iron ions decreased from 1.65 to 0, 82 mg/l. The proposed combined cleaning method requires inexpensive and affordable materials and is easy to operate.
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Статья научная
Modern liquid rocket engines of low thrust (LRELT) represent complex engineering struc-tures, which are subject to very high requirements in terms of efficiency, reliability, and cost-effectiveness. To confirm the characteristics of the developed designs, a comprehensive set of tests for prototype samples is required, allowing their operability to be verified under conditions close to real-life operation. As part of this work, a thermodynamic calculation of the LRELT chamber for fuel components such as liquid kerosene and gaseous oxygen was conducted. The injector calculation method used in this work is based on the application of similarity criteria. This allows the transition from small-scale injectors to those suitable for full-scale testing, including stand tests using the “hydroflush” method. For testing, a specialized test rig was created, allowing the testing of injectors manufactured using modern additive technologies, such as 3D printing from polymer materials. This not only reduces the cost of creating prototypes but also accelerates the testing process. The injector tests on the stand play a crucial role in verifying their operability. This testing method allows studying the behavior of injectors in condi-tions as close to operational as possible. In this study, injectors manufactured using additive technologies from polymer plastic were used. The use of such materials in the early stages of testing helped to reduce costs and time resources for producing prototype samples. During the tests, the injectors were subjected to liquid at a specified pressure differential, which allowed their operability and fuel distribution uniformity to be assessed. The results of the tests demonstrated a high degree of correlation between theoretical calculations and actual data. The injectors showed stable operation corresponding to the calculated characteristics, and also proved their suitability for further development stages. The use of additive technologies in the manu-facturing of the injectors confirmed its effectiveness, allowing the prototype production cycle to be short-ened and costs reduced. Moreover, the “hydroflush” method proved to be a reliable means of verifying and validating the working characteristics of the injectors, which is an important step toward their implementa-tion in real-world operations. Thus, the proposed methodology, which includes the use of similarity criteria and additive technologies, significantly simplifies the process of development and testing, improves accuracy, and brings the results closer to real operating conditions. This is especially important for increasing the reliability and quality of final products used in rocket and space technology, contributing to a reduction in operational risks.
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Design of a flexible spoke for a spacecraft umbrella antenna
Статья научная
Umbrella type antennas are often used in modern spacecraft. Their advantage is the possibility of compact placement during orbital insertion. At the same time, they must provide the necessary stability when deployed in space. Antenna stiffness mainly depends on the stiffness of the spokes, the design of which is a complex task of scientific research. Spacecraft antennas must provide functional performance and, at the same time, have a minimum mass. The cardinal direction of improvement of space antennas consists in application of new structural materials. Composites are characterized by high specific mechanical properties, which allow to create structures with a high degree of weight perfection. The problem is related to the presence of a large number of design parameters that affect the performance of composite structures in a complex way. Determining the optimal combination of these parameters for each structure and a particular design case leads to the need for a complex numerical experiment based on specialized algorithms, methods and programs. The aim of the study is to design a composite spoke for the umbrella antenna of a spacecraft, providing the required load-bearing capacity and maximum stiffness at a given mass limit of the structure. It involves the development of finite element models of the composite spoke of various designs, which would include the possibility of optimizing the design parameters by the criteria of strength, load-bearing capacity and stiffness. As a result of numerical experiment, the ways of increasing the bearing capacity and stiffness of the deployed spacecraft antenna are determined.
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Design of a multifunctional electric propulsion subsystem of the spacecraft
Статья научная
A common way to form an electric propulsion subsystem of the spacecraft is to create specialized equipment or to select the most suitable one from the ready-made ones. However, there are cases when the use of existing equipment is not optimal enough and leads to an unjustified increase of the subsystem mass. Therefore, the ques-tion of creating a minimum equipment set possibility from which it would be possible to form propulsion subsys-tems in optimal way is of interest. The set of tasks, variants of use and possible schemes of placing orbital cor-recting propulsion on the spacecraft are presented. The list of necessary propulsion subsystem elements is pre-sented as follows: a thruster block, a tank, a xenon feed unit, a power processing unit consisting of a power unit and switching units, the complete set of cables and pipelines, the software and mechanical devices for control of the thrust vector (as an option). The necessary capacity of propellant tanks for the tasks of correction and rais-ing of the satellite to GEO with a high-pulse Hall thruster is defined: for orbit correction tasks – up to100 kg, for orbit correction and raising to GEO tasks – up to200 kg. Necessary angle rates of mechanical devices for con-trol of the thrust vector are defined taking into account possible schemes of placing thrusters on the spacecraft. It is shown that in cases when it is required to apply two or more thrusters to increase overall thrust, it is more preferable in the weight aspect to apply a combination of power and switching units instead of monoblock type of power processing units, and advantage can reach tens of kilograms. Provided the listed set of functional units is created, the offered concept will make it easy to form propulsion subsystems of the spacecraft for solving a wide range of tasks. It will reduce the time and money spent on creation of propulsion subsystem for new space-crafts.
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Design of an atmospheric aerostatic probe for Venus exploration
Статья научная
Venus is the second planet from the Sun and the closest to Earth. Its atmosphere is the dens-est, and the temperature on the surface of Venus is the highest of all the planets in the Solar System. Due to convection and thermal inertia of the dense atmosphere, the temperature on Venus does not change significantly between the day and night sides of the planet. The temperature of the upper layers of the atmosphere is about –45 °C. The minimum surface temperature is at least 400 °C. The pressure on the surface of the planet is 90 times higher than at the surface of the Earth. Due to the complexity of the functioning of spacecraft (SC) on the surface, the planet remains virtually unexplored. However, at an altitude of just over 50 km there is the tropopause – the boundary between the troposphere and the mesosphere. Here, the conditions are most similar to the conditions on the surface of the Earth. This is the optimal area for SC, where the temperature and pressure will be similar to those on Earth. It is most advisable to send balloon probes to this area to collect scientific information. The aim of the study is to develop a design for an aerostat probe that will provide long-term transmission of information from the tropopause of the Venusian atmosphere. The work includes a ballistic calculation of the descent trajectory of the spacecraft in the Venusian atmosphere and the trajectory characteristics. To determine the parameters of the descent trajectory, a program was written to calculate the differential equations of motion of the atmospheric probe. The work includes a design for an atmospheric probe and the order of its operation.
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Design of the fastening assembly of the guys on the power spokes reflector
Статья научная
Currently, global communication systems are developing towards mastering high frequency bands for organizing high-speed information transmission channels, which requires large-sized antenna systems with reflectors up to 50 meters. Most of the technical solutions used for assembling large-sized reflectors are based on technological volumetric templates that geometrically completely imitate the necessary reflective surface of the reflector. The mass of such templates increases in cubic dependence on the increase in the diameter of the reflector, which is why it becomes more and more laborious to use them when assembling large-sized antennas due to the increase in the dimensions and weight of the templates. The purpose of the study is to design the attachment point for guy wires on the power spoke of the re-flector for a "templateless" assembly. The spoke is a composite isogrid structure on which arms are fixed for attaching power units. The fastening unit is an assembly unit consisting of a bracket and clips and al-lows you to precisely adjust the necessary pull tension force to fix the cord in the working position without the use of one-piece fastening methods. The analytical approach and finite element analysis were adopted as research methods. Using an ana-lytical calculation, the maximum tensile force of the guys in the designed unit was determined, thereby set-ting the maximum load for its operation. The coefficient of friction between the cord and the clamp in each individual case is determined experimentally. After simplifying the design and construction scheme of the bracket, the analytical calculation was carried out for a three-dimensional rod frame. To confirm the results of the calculation, a finite element model of the bracket was built and its static analysis was carried out. For the developed model of the bracket, the maximum stresses were determined and their comparative analysis was carried out with the results obtained analytically. With the help of solid modeling, the mass and overall characteristics of the braces fastening unit are determined. The limiting ranges of tension forces and the materials used in the knot, as well as its strength characteristics, were determined. This unit can be used in the "templateless" method of assembling a reflector for a wide range of large antennas, it has high manufacturability and versatility.
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Detection of information system objects interaction with DGA domains
Статья научная
Currently, malware developers are actively using domain name generation technique called DGA to es-tablish communication between malware and its command centers. Domain name generation in accord-ance with the given algorithm allows malicious software to bypass information protection tools blacklists, thus making blacklists ineffective, and establish a communication channel to receive control commands and parameters, as well as to transfer information from the information system to external resources con-trolled by attackers. Thus, it is necessary to develop new approaches to DGA generated domain names de-tection using DNS traffic of an information system. During the research, the authors have developed a solution for detecting information objects interaction with DGA domains based on the use of machine learning. The detection of this interaction occurs in two stages. On the first stage the classification task is being solved for each DNS name from overall infor-mation system DNS stream. On the second stage, for each DNS name classified as DGA, corresponding DNS query is being enriched using data from external sources and a final decision about the malicious nature of the query to resolve this DNS name is being made, followed by a notification of a security admin-istrator via e-mail channels. The paper describes the process of developing a classifier based on machine learning, defines the input data of the DNS name necessary for classification, presents the results of classifier training on a repre-sentative set of test data. The logic of making a decision about the malicious nature of DNS queries has been substantiated. The developed solution was tested using an experimental stand. Some recommenda-tions for correct classifier operation support are proposed. The application of the developed solution will make possible posteriori detection of information interac-tion of malicious software working on compromised information objects with the servers of attackers com-mand and control centers.
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Determination of coupling loss factors for beams connected at an angle
Статья научная
The use of a statistical energy method for the analysis of dynamic systems assumes that coupling loss factors of subsystems must be known. Coupling loss factors show what part of energy moves from one subsystem to another. They are included in the system of energy balance equations and must first be determined analytically, experimentally or numerically. The most promising of the listed methods is a numerical one. In particular, this paper uses a finite element method. The purpose of this study is to determine the coupling loss factors of two subsystems in two versions of their relative positions. The basis is the model of an L-shaped connection of two beams, which is quite common in such studies. L-shaped connections of structural parts are often found in building structures, but in other industries, such as the development of space and aviation technology, structural elements are often connected at an angle other than 90°. Since energy methods (EMs) can also be applied to aerospace industry, when developing approaches to analyzing structures using such methods, it is useful to know how the energy parameters of a system, in particular coupling loss factors, change depending on the fact at what angle their components are connected. The paper considers two system configurations: in the first, the beams are connected at a right angle, in the second - at an angle of 45°. The coupling loss factors of the beams are calculated for both system configurations. Conclusions are drawn about the possibility of disseminating the results obtained to more complex structures, namely spacecraft structures.
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Статья научная
The article describes the results of tests that have been carried out at the manufacturing plant of refrig-eration devices. These results have made it possible to estimate the capability of using a new method of testing refrigeration devices for compliance with the standards established by GOST, which determine the specific heat and power properties of each refrigeration device, depending on its type (single-chamber or with two-chambers, with one compressor or with two, etc.), passing acceptance tests. The graphs of the active power of the device will be presented when it is connected to the power supply network and the de-pendence of the change in the power graph depending on time will be described, the signs of the graphs of faulty refrigeration devices will be described, indicating the cause of the malfunction. The authors indicate the parameters by which it is proposed to compare the obtained power graphs with the reference graphs obtained when testing reliably serviceable refrigeration devices. Based on the results of comparing certain values of the parameters characterizing the device it is proposed to judge the compliance of each individu-al refrigeration device with the standard. It also provides a description of the algorithm that will be used to determine the compliance of the refrigeration device with the established parameters of heat and power characteristics that determine its performance. The implementation of this algorithm will be carried out by writing an appropriate program for the programmable logic controller (PLC).
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Determination of the digital controller’s characteristics of the switched-mode power converters
Статья научная
The development of spacecrafts equipment is on the way to digitalization. In particular, energy spacecraft conversion devices are being modernized by introducing digital automatic control systems instead of analog ones. This leads to an increase in the efficiency of the power supply system, but at the same time, there is a need to create methods to determine characteristics that will confirm with a high degree of accuracy and conformity of the manufactured sample with the technical requirements specified during its design. The article describes the features of functioning and methodology for determining digital control channel of a pulse voltage converter’s characteristics. The proposed approach is a toolkit for verifying the correct implementation of both the hardware parts of the control channel and the controller, which is a program code implemented on digital control devices. The technique is based on determining the degree of responses correspondence to typical external influences of a hardware-implemented control channel and its model. Based on the transfer functions of the IIR and FIR digital filters, using standard built-in models, the control channel of the pulse voltage converter corresponding to the tested hardware-implemented device is simulated in the package Matlab Simulink. The basic principles of building the software architecture experiment are described. A block diagram of the test complex has been developed, including sources of external influence, control channel, and a test management tool (in this case, a personal computer). An example of applying such a technique to verify the parameters of the developed PID controller is given. Operability and accuracy of the proposed method to determine characteristics of the control channel by reaction to a sequence of rectangular pulses, and by constructing the AFCL are experimentally shown. Application of this verification method to production conditions will allow a complete check of individual central control units (CCU) of energy-converting equipment with closed feedbacks even at the stage of devices development, which will eliminate errors in the implementation of regulators in control loops.
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Статья научная
The main function of a thermal control system (TCS) is to maintain the temperature at nodal points of a spacecraft in given ranges due to redistribution of thermal energy and the discharge of excess thermal energy into space. TCS may have a different design and principle of operation. One of the most common options is TCS using a liquid circuit (LC) and pumping coolant circulation. In the development of promising design-layout schemes for instrument compartments of nonhermetic formation spacecraft, it becomes necessary to state and solve new problems associated with the creation of computational and mathematical models of intermediate convective heat transfer in a fluid circuit. For systems of integral equations of a LC thermal model with fairly complex topographic boundaries and connections, the justification and use of the defining (equivalent) thermal resistance seems to be a compromise of counting implementation of a system that simulates a TCS with integration along the length of the LC. In this paper, for the computational model of the liquid circuit of the thermal control system, including the system of equations of two-dimensional thermal balance of the characteristic surfaces of a nonhermetic formation spacecraft, a method of calculating the determining thermal resistances was proposed and implemented. This method includes the calculation of the complex heat transfer coefficient and the local heat transfer coefficient to the heat carrier flow. The approach considered in this paper allows us to obtain a numerical solution for the distribution of heat flows and temperatures of liquid circuits with complex topographic boundaries and connections with minimal loss of accuracy. The determination of the local heat transfer coefficient makes it possible to take into account the influence of changes in the temperature of the coolant flow on the overall picture of convective heat exchange.
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Developing the laboratory test bench of fuel three-point measurement
Статья научная
The development of digital technology allows continuous improvements in many areas. This paper reflects the development of a new fuel measurement method. To measure the fuel, the authors propose three fuel sensors and a computational element to simulate the position of the fuel level in space with further calculating the volume of fuel, to reduce errors due to the fuel meters operation. The main advantage of this system is the elimination of errors arising from the evolution of an aircraft, as well as its uneven movement. The paper demonstrates a phased development of a laboratory test bench to study the three-point method to measure fuel. In the course of the work, a vessel is assembled to simulate the fuel tank of the aircraft. The vessel is a glass container with submersible measuring sensors. Also, the research contains calculation of the bridge electrical circuit to compute a voltage value at each sensor. In the test, transformer fluid substitutes fuel, since it acted as a dielectric. The program code for the microcontroller is recorded. The proposed method has several advantages in comparison with traditional methods of measuring the fuel level; a mathematical model is presented, on the basis of which the level of fuel in the aircraft fuel tank is measured.
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Development of SEM method for analysis of organ-containing objects using inverse opals
Статья научная
The purpose of this study is to test the possibility of using inorganic macroporous structures of inverse opal in sample preparation for scanning electron microscopy of biological objects. As an absorbent substrate we used silica inverse opals prepared by a sol-gel method to study the biological objects. The process of manufacturing the inverse opal involves a complex multi-stage technological process. First, we synthesized submicron spherical particles from polymethylmethacrylate by the method of emulsifier-free emulsion polymerization of methylmethacrylate in an aqueous medium in the presence of a diazoinitiator. This method can be used to obtain an ensemble of particles with high monodispersity, the average size of which can vary in the range from 100 to 500 nm. Then, by self-assembly technique, we deposited the beads of polymethylmethacrylate into ordered matrices (templates), mainly with a face-centered cubic lattice. The resulting mesoporous structures, called artificial opals or colloidal crystals, had lateral dimensions of about 10 × 10 × 2 mm. Then we heat-treated the opals to 120 °C to harden the template before being impregnated with the precursor. Further, we impregnated the opals with silica sol with a particle size distribution from 1 to 5 nm, obtained by hydrolysis of tetraethoxysilane in the presence of hydrochloric acid, and then, after curing and drying the impregnating composition in air at room temperature, we multi-stage fired them up to 550 °C at normal pressure in the air atmosphere to remove all organic components. As a result, the macroporous metamaterial (the so-called inverse opals) with an open system of pores up to 400 nm in size, occupying about 80 % of the volume, were obtained. We studied lactic acid bacteria of cucumber brine and human red blood cells with TM4000 Plus, SU3500 and S-5500 scanning electron microscopes. Auxiliary substance for the sample preparation was ionic liquid VetexQ EM (Interlab LLC). We showed that it is possible to use the inverse opal as an absorbent substrate for sample preparation and rapid analysis in scanning electron microscopy without pre-drying, chemical treatment, or temperature exposure. To improve imaging in the electron microscope, we used sputter coater to cover the inverse opal surface with a thin film of platinum. The use of ionic liquid in combination with the absorbent porous medium allows preserving an original shape of the biological structures. Using the human red blood cells and lactic acid bacteria, we showed that it is possible to carry out of the morphological analysis of the cells using various scanning electron microscopes. We found that on the basis of the inverse opal, there is a fundamental possibility of creating the absorbent substrate suitable for repeated use in the study of the biological objects. At the same time, trace remnants of previous samples remaining after annealing the plate do not introduce significant distortions when conducting new series of observations. In this study, we obtained high-quality electronic micrographs of the biological objects with high resolution and contrast. At the same time, due to the use of the inverse opals as the absorbent substrate, time and financial costs for research are reduced.
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Development of a human-machine interface for cascade control mills in obtaining nepheline ore charge
Статья научная
Aluminum and alloys based on it are the main materials for space engineering, both in the production of vehicle parts, and in the organization of power supply and electronics. The raw material for producing aluminum is alumina. Alumina production is a multi-stage process that includes the processing of raw materials in various ways: mechanically, thermally, chemically. Mechanical processing of raw materials is the first stage of production, it includes a crushing department and a batch preparation department. The preparation of the charge from nepheline ore for further stages of production takes place in mills with the addition of limestone and recycled solution. The ratio of the components entering the mills directly affects the composition of the charge and the quality of the final product. At the same time, the required quality of the charge is not always ensured, since the costs of the components are set by a person based on the re-sults of a rare chemical analysis performed by the laboratory with a delay. The aim of the work is to improve the control of the mill when receiving a mixture of nepheline ore. A virtual mill control program and a mnemonic diagram were developed in the TIA Portal software environ-ment using the S7-1500 microprocessor controller. A system for automatic control of the lime and alkaline modules of the raw charge has been developed. The control program is built on the basis of calculating the moisture content of the charge, as well as the al-kaline and limestone modules, depending on the composition of the ore, limestone, as well as the feed rates of circulating water, ore and limestone to the mill. The mnemonic diagram includes an indication of important process parameters, trends in input and output characteristics, and tools for setting control actions.
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