Статьи журнала - Siberian Aerospace Journal
Все статьи: 330
6-aperiodic words over the three-letter alphabet
Статья научная
The work is devoted to the study of sets of aperiodic words over a finite alphabet. A set of such words can be considered as some kind of finite formal language. W. Burnside raised the issue of local finiteness of periodic groups. The negative answer was given only sixty years later by E. S. Golod. Soon S. V. Aleshin, R. I. Hryhorczuk, V. I. Sushchanskii constructed more examples confirming the negative answer to Burnside's question. Finiteness of the free Burnside group of period n was established for periods two and three (W. Burnside), for period four (W. Burnside, I. N. Sanov), for period six (M. Hall). The infinity of such a group, for odd indicators exceeding 4381, is established in the work of P. S. Novikov and S. I. Adyan (1967), and for odd indicators exceeding 664 in the book by S. I. Adian (1975). A more intuitive version of the proof for odd n > 1010 was proposed by A. Yu. Olshansky (1989). In this article, we consider the set of 6-aperiodic words. In the monograph by S. I. Adyan (1975) it was shown the proof of S. E. Arshon (1937) theory that there are infinitely many three-aperiodic words of any length in the two-letter alphabet. In the book of A. Y. Olshansky (1989), a proof of the infinity of the set of six-aperiodic words is given and an estimate of the number of such words of any given length is obtained. Here we try to estimate the function of the number of six-aperiodic words of any given length in a three-letter alphabet. The results obtained can be useful for encoding information in space communication sessions.
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A routing algorithm for the Cayley graphs generated by permutation groups
Статья научная
The purpose of this work is to create an effective routing algorithm on the Cayley graphs of permutation groups, superior in its characteristics to an algorithm using an automatic group structure. In the first section of the article we describe the auxiliary algorithm A–1 which allows numbering elements of a given permutation group. In the second section we present the algorithm A–2 for calculating the routing table on the Cayley graph and algorithm A–3 for determination the optimal route between two arbitrary vertices of the graph. Estimates of time and space complexity are also obtained for these algorithms. In the third section we describe the algorithm A–4 for calculation the minimal word of a group element. It is proved that the computational complexity of the algorithm will be proportional to the length of the input word. The fourth section presents the results of computer experiments for some groups of permutation groups, which compare the time for calculating the minimum words using algorithm A – 4 and an algorithm based on the construction of an automatic group structure. It is shown that A – 4 is much faster than its competitor.
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Статья научная
Many developers of new high-thrust solid-propellant rocket engines are faced with the problem of acoustic instability of combustion. The phenomenon of resonant combustion of solid fuel is associated with a number of specific features. The cavities of the combustion chambers of such engines have complex geo-metric shapes. The gas channel is long enough. Its length usually exceeds five or more calibers. The thick-ness of the flame front is measured in micrometers and the combustion zone is localized over the open fuel surface. The flame front often turns out to be capable of amplifying pressure perturbations at the frequency of one of the acoustic eigenmodes if the wave antinode falls on a thin combustion zone. The oscillatory process can be regular or sporadic. Resonances of the longitudinal acoustic mode are most often observed. However, there were cases of simultaneous oscillation of two modes. In some cases, during the operation of the engine, the amplitude of the resulting oscillations began to decrease and the combustion process be-came almost quasi-stationary. Self-oscillatory processes in the combustion chambers of solid propellants have a threshold sensitivity to pressure overshoots. The vibration amplitudes can be several tens of percent, sometimes reaching the nominal working pressure in the chamber. The amplitude-frequency characteristics of the oscillations are sensitive to the composition of the fuel, responding to changes in the chemical com-position, as well as to the mechanical properties of the fuel. The regions of unstable regimes are definitely related to the geometry of the gas cavity. Together with pressure fluctuations, the combustion process is influenced by gas-dynamic factors, significant non-uniformity of the gas flow parameters along the length of the channel, its turbulence, and other factors. When designing solid-propellant rocket engines, it is nec-essary to estimate the frequencies of the natural acoustic resonances of the combustion chambers. The article discusses a technique for determining the frequencies of natural resonances of the first and second tone of the longitudinal mode of acoustic vibrations in the combustion chambers of solid propellant rocket engines. The gas path of the combustion chamber is divided into homogeneous sections, for which the solutions of the wave equation are presented. To determine the natural frequencies and distribution of vibrational pressures and velocities, the method of “stitching” acoustic fields at the boundaries of the cavi-ties was used.
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About non-parametric identification of partial-parametred discrete-continuous process
Статья научная
The paper considers a new class of models under conditions of incomplete information. We are talking about multidimensional discrete-continuous processes for the case where the components of the vector of output variables are stochastically dependent. The nature of this dependence is a priori unknown, but for some channels the a priori information corresponds to both nonparametric and parametric type of the initial data in the process under study. Such a situation leads to a system of nonlinear equations, some of which will be unknown, while others are known accurate to the vector of parameters. The main purpose of the model is to determine the forecast of output variables with known input, and for implicit nonlinear equations it is only known that one or another component of the output depends on other variables that determine the state of the object. Thus, a rather nontrivial situation arises when solving a system of implicit nonlinear equations under conditions where in one channel of a multidimensional system equations themselves are not in the usual sense, while in others they are known up to parameters. Therefore, an object model cannot be constructed using the methods of the existing identification theory as a result of a lack of a priori information. If it was possible to parameterize the system of nonlinear equations, then with a known input this system should be solved, since it is known and the parameterization stage is over. However, in this case it is still necessary to evaluate parameters. The main content of this article is the solution of the identification problem in the presence of a partially-parameterized discrete-continuous process, despite the fact that the parameterization stage cannot be overcome without additional a priori information on the process under study. In this regard, the scheme for solving the system of nonlinear equations can be represented as a certain sequential algorithmic chain. First, on the basis of the available training sample, including all components of the input and output variables observation, a residual vector is formed. After that, an estimate of the object output with known values of the input variables is constructed based on the estimates of Nadarai-Watson. Thus, for given values of the input variables of such a process, it is proposed to carry out a procedure for evaluating the forecast of output variables in accordance with the developed algorithmic chain. Numerous computational experiments, studying the proposed models of partially-parameterized discrete-continuous processes have shown their rather high efficiency. The article presents the results of computational experiments illustrating the effectiveness of the proposed technology for predicting values of output variables from known input variables.
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Actuator made of a material with a shape memory effect for transformable space structures
Статья научная
Transformable structures represent a special class of large space systems. They are delivered into orbit in a tightly packed state. When the required parameters of the orbit are reached, their deployment or trans-formation is carried out. The shape of the transformed structure is rigidly fixed upon completion of the transformation process. At the same time, shock loads occur on its constituent elements. The complication of design schemes and the increase in the dimensions of modern transformable space systems due to the increase in their operational functionality leads to the necessity of improving their mass characteristics. At present, many variants of transformable structures of space antennas have been developed abroad and in our country, the ratio of the mass of mirrors to their areas has decreased to 0.5.–1.5 kg/m2. Further im-provement of transformable space structures is possible with the use of materials with the shape memory effect to create actuators that ensure controlled shock-free deployment of these structures from the transport state to the working position Experimental and theoretical studies of the actuator model made of titanium nickelide material have confirmed the fundamental possibility of its use for the deployment of promising transformable space structures. During the tests, the main characteristics of the actuator model were determined, namely: the actuation force, the working stroke and the actuation time.
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Additional screening tests at the testing technical center for ground power equipment
Статья научная
When testing a spacecraft in a thermal vacuum chamber, special attention is paid to ensuring guaranteed continuous power supply to the spacecraft for a long time (up to several months). The de-energization of the spacecraft can lead to the failure of thermal control systems, up to the complete failure of the spacecraft worth several billion rubles. During the operation of ground power equipment, the necessary data on the intensity and types of failures in the operation of this ground power equipment were obtained, the result of which led to an increase in the test time and the risks of failure of the spacecraft at this stage. As a result of collaborative work of JSC “Academician M. F. Reshetnev Information Satellite Systems” and Research Institute of Automation and Electromechanics of Tomsk State University of Control Systems and Radioelectronics on the analysis of failure statistics obtained during operation, a technical task was worked out to develop methods for increasing the uptime of ground power equipment manufactured. One of the key requirements for the new generation of ground power equipment being manufactured is to ensure a high reliability indicator – “uptime”. Experience in the field of additional screening tests of electro-radio parts before their installation in a spacecraft allows us to propose a method for determining the quantitative value of the decreasing coefficient of screening tests using a method for evaluating the coefficients characterizing the degree of difference between radio-electronic products that have successfully passed additional screening tests and received ones from the factory manufacturer. As a result of the calculations of the decreasing coefficient and the mathematical calculations of the uptime, it is possible to determine the effect of the decreasing coefficient of screening tests on improving the reliability of ground power equipment. High requirements for uptime of ground power equipment for electrical tests of the spacecraft have led to the need for additional screening tests in special testing technical centers, where the verification of indicators of the number of failures by confidence probabilities should be carried out. The introduction of additional screening tests in the technological process of ground equipment manufacturing is the next step in the methods of increasing reliability.
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Algorithm for correcting camera pan and tilt on aircraft based on recorded video
Статья научная
Due to the difficulties that arise when using satellite navigation systems at airfields at present, and the insufficient accuracy of inertial navigation systems, optical measuring systems have again begun to be used to carry out trajectory measurements. However, existing measuring systems have a number of disadvantages. The purpose of this work is to describe a method for increasing the accuracy of trajectory measurements obtained by the goniometric method. The article reviews the main algorithms currently used in trajectory measurements and their shortcomings. An algorithm for frame-by-frame post-flight processing of recorded video from cameras of an optical-electronic measuring complex is proposed. A description of the implementation of this algorithm is given, taking into account the specifics of graphical software interfaces for processing user of the algorithm’s input. The proposed algorithm allows, after carrying out trajectory measurements, without time restrictions, to correct pan and tilt of the platform at each moment in time. The proposed algorithm makes it possible to increase the accuracy of trajectory measurements when testing aircraft, both already carried out and future ones. The proposed algorithm can also be used to obtain would-be pan and tilt of the camera when implementing a goniometric direction-finding complex using fixed wide-angle optical cameras. For example, when measuring the radiation patterns of an aircraft's onboard antennas using a quadcopter-meter to determine its position in space at each moment in time. The article also presents the main advantages and disadvantages of the algorithm, makes proposals for its improvement, and suggests possible areas of its application.
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Algorithmic and software of the system profiling the actions of users of the information system
Статья научная
The paper describes the software of the system for profiling the actions of users of the information system. This profiling system is aimed at solving the problem of trust in users of information systems. The system should regulate access to protected resources by analyzing user behavior. The algorithmic component of the system is represented by a user behavior model and a general system operation algorithm. The user behavior model is based on the apparatus of Markov chains Software implementation allows in practice to obtain the foundations of the proposed approach to work. At the development stages, the choice of software architecture is carried out. The client-server architecture was chosen as a reasonable decision. The software component of the user activity profiling system consists of five separate software modules. At the end of development, a brief testing of the components is carried out. The novelty of this work lies in the proposal of an approach that uses the profiling of user actions as an additional determining factor in managing access to objects, as a way to strengthen the basic measures “Controlling access of subjects to access objects” in the order system of FSTEC of Russia.
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Alternative method of solar simulation for thermal vacuum tests of spacecraft
Статья научная
Solar simulators based on gas-discharge xenon lamps, used to obtain the thermal state of objects for thermal vacuum testing of spacecraft, are one of the key, most complex and energy-consuming elements of test equipment. Complexity of the optical system, the large number of optical elements, the need for constant monitoring of their condition, tuning and adjustment by highly qualified personnel significantly complicate obtaining of required luminous characteristics, mainly spatial uniformity of irradiance. Another common drawback is their low energy efficiency, which does not exceed 10 %. We proposed an alternative method of solar simulation using solid-state luminous sources – high-efficiency LEDs, with their placement without a bulky and complex optical system directly in a thermal vacuum chamber. At the same time, one of the most difficult problems of adapting to the conditions of thermal vacuum tests is to provide the necessary luminous characteristics. The required wavelength range, spectral match is obtained by combining assemblies of high-efficiency LEDs of six different wavelengths and halogen lamps. We carried out a number of experiments, including measuring the luminous characteristics of alternative luminous sources and mathematical modeling of the matrix emitter. As a result, the possibility of using the proposed method for thermal vacuum tests of spacecraft was confirmed; the luminous characteristics of the model meet the requirements, and in terms of uniformity of irradiance and energy efficiency, they significantly exceed those of traditional solar simulators.
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An algorithm for fast multiplication of elements in 2-groups based on the Zhegalkin polynomials
Статья научная
Network design for a multiprocessor computing system or data center is an important problem where the search for graph models that have attractive topological properties and allow the use of efficient routing algorithms is carried out. Cayley graphs have the indicated properties, in particular such as high symmetry, hierarchical structure, recursive design, high connectivity and fault tolerance. The definition of the Cayley graph implies that the vertices of the graph are elements of some algebraic group. Selecting a group and its generating elements allows us to obtain a graph that meets the necessary requirements for diameter, degree of vertices, number of nodes, etc. A large number of scientific articles and monographs are devoted to solving this problem. The goal of this work is to create an algorithm for fast multiplication of elements in finite 2-groups whose exponent is 2n. The first section of the article provides a theoretical justification for the algorithm for fast multiplication in finite 2-groups. It is shown that elements of these groups can be represented in the form of bit strings, and their multiplication is carried out based on the Zhegalkin polynomials. The second section presents the pseudocode of the algorithm on the basis of which the Zhegalkin polynomials are calculated. The third section demonstrates an example of obtaining the Zhegalkin polynomials for a two-generated group of exponent 4. In conclusion, the prospects for using the algorithm on the real hardware are discussed.
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Статья
The authors propose an approach to research tests of copra-spring stand, designed for testing rockets and spacecraft on inertial forces of a pulse character. The authors present the design of the stand, consisting of two main parts: mobile and stationary. The authors present a method for calculating the magnitude of the load factors and the oscillation frequency of the test object, and calculate the parameters for adjusting the spring stiffness. They describe the possibility of carrying out dynamic tests for imitating transient loads that hermetic structures such as modules of habitable orbital stations, loaded by internal pneumatic pressure, withstand during their lifecycle. The authors present the results of research tests when the stand without any additional weight was falling from the height of 20, 35 and 50 mm. They determine the levels of axial and transverse accelerations on the envelope of the stand and the lower ring. A comparison of the original and filtered signal from the load factor sensors obtained in each test case was made. The authors present the results of calculating accelerations of the moving part of the stand using the video processing of the experiment. To determine the position of the stand envelope they developed special software. The essence of the software was to determine the coordinate of the border of the color change from the frame height from a light color to a darker one using averaging in rows. The authors show that the results of a comparison of manual frame-by-frame measurement and data obtained by the software method indicate a sufficient convergence of the results using a drop from the height of 20 mm experiment. The comparison of axial loads obtained by various methods is given, when the moving part of the stand is thrown from the height of 20, 35 and 50 mm, respectively. The zero time points for the video and accelerometers were determined so that the first maximum is reached simultaneously. According to the results of research tests, the authors describe the development and validation of the finite element model of the stand. The calculations were carried out in a nonlinear formulation, which makes it possible to correctly take into account the loading of the stand at all stages, using the method of direct solution of the equations of motion. The authors show the results if calculating the time dependences of displacements and load factors at the sensor installation places and a comparison with the experimental results, which shows a good convergence.
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Analysis of corporate network cyber threats based on parallel processing of Netflow data
Статья научная
Public services of various organizations are subject to constant cyber attacks, which increases information security risks. Network traffic analysis is an important task to ensure the safe operation of network infrastructure, including corporate networks. This paper provides an overview of the main approaches for analyzing network traffic, it provides the related work and points out the shortcomings of the existing work. Here is a method is to analyze network traffic data using the Netflow protocol, which allows traffic data to be stored at the L3 layer of the OSI model. A feature of the study is the use of long observation periods. When storing data over long time intervals, the logs become large, which requires parallelization for primary data processing. The authors developed a cross-platform software package for distributed processing of network activity logs, which was used to analyze the network activity of the corporate network of the Krasnoyarsk Scientific Center for 2021–2022. A diagram of the software package is shown, its capabilities and operating features are described. Data sources for analysis and processing methods are provided. In this paper the authors formulated and formalized heuristic criteria for the anomaly of network traffic, which identify the presence of possible network attacks, and extracted datasets on the network activity of various application-level protocols. For the obtained data sets, statistical indicators were calculated, information about anomalous network activity was obtained for two years. In this research, we tested the previously proposed method for comparing the cyber threats risks for different time intervals, which showed a significant increase in risks for 50% of indicators in 2022. Comparisons of monthly intervals over different years showed similar increases in risk. Therefore, the method has shown its efficiency and can be used in other areas in which there are groups of criteria for independent indicators. The authors have proposed plans for further development of methods for analyzing network activity.
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Analysis of the ADS-B airspace monitoring system
Статья научная
One of the most important aspects of flight safety is awareness of AC air position (AC is the short for aircraft). The leading method of stating AC airspace location is the use of radar systems – primary, secondary, combined primary – secondary surveillance radars-though radar systems have significant drawbacks. However, at present, more advanced technologies are also in use, for example, ADS-B and multilateration. This article is focused on ADS-B broadcasting. Global coverage, low cost, great amount of obtainable information makes Automatic Dependent Surveillance – Broadcast a highly efficient system. Application of the method for AC air positioning is equally effective for helicopters, especially for those operated by special emergency services. As for the infrastructure of air navigation, the research in this sphere is focused on surveillance systems necessary for reliable control of increasing air traffic. The problem of better awareness of AC air position is still acute and has always been the object of extensive research. At present, homemanufactured civil aviation helicopters are practically never equipped with ADS-B transponders, and hardly ever use the available resources of transceiver-based surveillance systems. The objective of the analysis presented is to demonstrate the applicability of Flightradar system options, as well as implementation of ADS – B transponders for helicopter fleet. Operating surveillance systems like Flightradar may considerably increase flight safety by improving the awareness of helicopters current air position.
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Статья научная
The force measuring device is a part of the bench force measurement system required for direct meas-urement of the rocket engine thrust during the test. One of the common types of force-measuring device calibration systems is a lever-type calibration device. The simplicity of the kinematic scheme is one of the main advantages of its use as a calibration system. Along with this, the disadvantages of this scheme are concentrated in the supporting elements of the lever system, since it is the wear of the supports that leads to the accumulation of a systematic error of the entire system with a proportional deterioration in the accura-cy of the force measurement process. The aim of the work was to analyze the features of prismatic supports used as part of a lever-based calibration device of a force-measuring device, as well as to simulate the stress-strain state of a model of a real prismatic support used in an existing force-measuring system. The work considers the closest theoretical information associated with calculating the stress distribution in the wedge and half-plane in accordance with the plane problem of the theory of elasticity. The selection of the mechanical properties of materials was carried out depending on the specified hardness indicators, as well as the modeling of the contact problem in a given prismatic support, depending on the angle of inclination of the prism in relation to the pad, using the static analysis of the Solidworks Simulation software package. In this work the calculation results are given and also conclusions are drawn.
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Статья научная
The subject of research of this paper is anomalies in the final products of the International GNSS Service (IGS), namely in the orbits and clock drifts of navigation satellites (NSs). The purpose of research is to de-termine the influence of such anomalies on the accuracy of solving the precise point positioning (PPP) problem. The method of approximation by polynomials of high degrees previously proposed by the authors is used as a method for detecting and distinguishing anomalies in the orbits of navigation satellites. The methodology recommended by the IGS is used in solving the PPP problem. The proposed method for de-tecting and distinguishing anomalies in orbits is applied to the analysis of anomalies in the orbits of GPS navigation satellites. The examples of anomalies that can be detected using the proposed method are dem-onstrated. The brief statistical analysis and comparison of the frequencies of anomalies occurrence in the orbits of GPS navigation satellites published by various IGS analytical centers from 2010 to 2018 are pre-sented. It is shown that orbital anomalies occurring at the boundaries of daily intervals are, as a rule, cor-related with anomalies in clock drifts and have a partially mutually compensating effect on the solution of navigation problems. Experiments showed that when solving the PPP problem, anomalies significantly in-crease the root-mean-square deviation (RMSD) of the solution residual. Two options for solving the prob-lem with anomalous orbits are considered: the exclusion of satellites with anomalous boundaries of daily intervals from the solution and the "correction" of the anomaly in the orbit. The most natural method of correcting orbits (changing the orbit in order to remove large anomalies) at the boundaries of the daily segments of the published final orbits was tested. The exclusion of satellites with anomalies in the orbit turned out to be the most effective from the point of view of PPP problems, since attempts to "correct" the orbit more often led not to a decrease in the RMSD of the pseudorange residuals, but to its increase, which is associated with correlated anomalies in the navigation satellite clock drift. According to the research results, we can conclude: before solving the PPP problems, it is necessary to study the orbits and the navi-gation satellites clocks drifts for the presence of anomalies by the proposed methods and, if possible, to exclude such satellites from the data used to solve the PPP problem. Our proposed methods for detecting and accounting for anomalies in the orbits and clocks of navigation satellites, in addition to obvious appli-cations to solving ground navigation problems, are also applicable to monitoring the quality of the space and ground segments of the GLONASS and GPS systems.
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Статья научная
In this article authors are considering information security data integrity problem relevant for electronic archive management. In high-tech industry large electronic photo archives arise as a part of quality management. Photofixation applied for responsible operations control, documenting technological process, fixing the components state on input and output control, incongruities registration. An image substitution or reuse possibility makes necessary electronic archive proto document integrity control. These illegal actions can be both the result of an operator’s mistake and motivated by intentional defect concealment. As a solution authors suggest an electronic archive organizing method for storing photo documents. The method based on a digital watermark labeling of full-color images with orthogonal Zernike moments calculated for certain image points (and their neighborhoods). Suggested method can prevent watermark destruction by geometric image transformation (rotation, compressing, reflection etc.). Digital watermark contains both information about technological process on current image and information about other images – this fact allows talking about integrity of the whole photo documents set. One of the most important method characteristic is image format invariability and making additional metadata files unnecessary which allows user to apply standard software for a further work with photo document.
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Статья научная
To analyze the stress-strain state of homogeneous and composite bodies (CB), the method of multigrid finite elements (MMFE) is effectively applied, which uses multigrid finite elements (MgFE). MMFE gener-ates multigrid discrete models of small dimension, in which the inhomogeneous structure of bodies is taken into account within the framework of a micro-approach using MgFE. Basic discrete models (BM), taking into account the heterogeneous structure of bodies, have a high dimension. To reduce the dimensionality of discrete models of bodies, MMFE is used. However, there are BM CB (for example, BM bodies with a mi-cro-inhomogeneous structure), which have such a high dimension that the implementation of MMFE for such BM, due to limited computer resources, is difficult. In addition, for multigrid discrete models of high dimension, the MMFE generates numerically unstable solutions, which is associated with the error of com-puter calculations. To solve these problems, it is proposed here to use fictitious discrete models in calcula-tions, the peculiarity of which is that their dimensions are smaller than the dimensions of BM CB. In this paper, we propose a method of fictitious discrete models (MFDM) for calculating the static strength of elastic composite bodies with an inhomogeneous, micro-inhomogeneous regular structure. MFDM is implemented using MMFE with adjusted strength conditions application which takes into ac-count the error of approximate solutions. The MFDM is based on the position that the solutions that meet the BM CB differ little from the exact ones, i. e. we consider these solutions to be accurate. The calculation of CB by MFDM is reduced to the construction and calculation of the strength of ficti-tious discrete models (FM), which have the following properties. FM reflecst: the shape, characteristic dimensions, fastening, loading and type of inhomogeneous structure of the CB, and the distribution of elas-tic modulus corresponding to BM CB. The dimensions of FM are smaller than the dimensions of BM CB. The sequence consisting of FM converges to BM, i. e. the limiting FM coincides with BM. Calculations show that the convergence of such a sequence ensures uniform convergence of the maximum equivalent stresses of the FM to the maximum equivalent stress of the BM CB, which allows the application of such FM in the calculations of elastic bodies for strength. Two types of FM are considered. The first type is scaled FM; the second type is FM with variable char-acteristic sizes. In this paper, the FM of the second type is considered in detail. Calculations show that the implementation of MMFE for FM with one, two or three variable characteristic sizes leads to a large sav-ing of computer resources, which allows the use of MFDM for bodies with a micro-inhomogeneous regular structure. Calculations for the strength of CB according to MFDM require several times less computer memory than a similar calculation using BM CB, and does not contain a procedure for grinding BM. The given example of calculating the strength of a three-dimensional composite beam according to MFDM us-ing FM with three variable characteristic dimensions shows its high efficiency.
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Статья научная
Carbon nanostructures have been in the focus of world science for more than 25 years, since the discovery of fullerenes in 1985, single-walled carbon nanotubes in 1993, graphene in 2004, graphene quantum dots in 2004. Graphene is a monocrystalline graphite films (2D material) with a thickness of several atoms that are stable under environmental conditions and they have excellent electronic, mechanical, chemical, thermal and optical properties. All over the world, research and development of new methods of using graphene in various fields such as energy, oil production, materials science, and electronics are actively carried out. Currently, the use of graphene-containing materials as modifiers for the creation of durable and effortless materials in aviation, automotive and other branches of engineering is an urgent problem. It is advisable to introduce graphene particles into the composition of composite materials using their stable dispersions in a liquid medium. The production of colloidal graphene suspensions is effective in many cases using the method of liquid phase exfoliation of graphite. The paper presents the results of studying the physico-chemical properties of aqueous graphene suspensions obtained by liquid-phase exfoliation of natural graphites using high-speed hydrodynamic technology. Graphite grades GK-1 and GAK-2 (Grafitservice, Chelyabinsk, Russia) are crystalline graphites obtained by enrichment of graphite ores and joint enrichment of natural graphite ores and graphite-containing waste from metallurgical industries, respectively. Graphite suspensions were prepared in distilled water with 1 wt.% graphite, surfactant was added to some samples, processing time (3–120 min), rotor rotation speed (4 000–11 000 rpm). The resulting graphene suspensions were investigated by XRD, by electron microscopy and sedimentation analysis methods. The particle size was determined using the DT-1202 electroacoustic spectrometer. The presence of multilayer graphene is confirmed by comparing the results of XRD with the literature data. Along with multilayer graphene, the presence of graphene dots was detected. Aqueous graphene suspensions for graphites with different sedimentation times have been obtained. For graphite GAK-2 – six days, for graphite GK-1 – 90 days, for graphite GK-1 + surfactant – 6 months.
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Application of optically black lightabsorbing coating on aluminum and titanium alloys
Статья научная
The paper presents an analysis of methods for obtaining an optically black light-absorbing coating by microarc oxidation on valve metal alloys. The formulation of a universal electrolyte and processing modes for the formation of an optically black coating on aluminum and titanium alloys are revealed. The dependences of the parameters of the processing modes on the properties of coatings are established. The resulting oxide layer has a high degree of blackness and has a homogeneous structure. The results of the study can be used when applying optically black MDO coating on products of rocket and space technology.
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Статья научная
Trends in the development of the spacecraft (SC) industry pose increasingly complex problems for mechatronic systems. Due to the complexity of the assembly processes of large-sized transformable struc-tures (LTC) and solar panels, the current methods of structures deployment are becoming less reliable and relevant. In addition, the development of orbital stations leads to the emergence of a whole range of new problems. Using mechatronic manipulators is one of the promising approaches. However, the functionality of their application is severely limited by the algorithms for moving the effector and manipulating objects predetermined during development. In this regard, there is a need to develop new approaches to finding and determining the shape of the target object, for further calculation of the algorithm for its interaction with the mechatronic manipulator gripper. The paper presents a method for reconstructing the three-dimensional shape of objects, based on using a computer vision system. A stereo camera is used to obtain the spatial characteristics of the scene. Based on the data obtained, the scene is divided into several independent geometric surfaces, followed by stage-by-stage processing by neural network algorithms. The required parameters of the target objects are ex-tracted at each stage of the algorithm. YOLACT EDGE is used as a neural network architecture, which performs semantic segmentation and classification of objects. The correlation of the spatial characteristics of the target objects and the replacing three-dimensional model can be considered as a separate problem. To ensure this correlation, the neural network architecture was supplemented with the branch "Keypoints mask", which provides a prediction of the positions of the keypoints of objects that unambiguously deter-mine the spatial characteristics of the target object. As a result, the system obtained is able to provide the construction of a three-dimensional map of the swept area in real time. In addition, based on the received telemetric information, it is possible to calculate the trajectory of the manipulator's effector and its interaction with objects.
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