Статьи журнала - Сибирский аэрокосмический журнал
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Modeling of spectroerergetic characteristics of space objects in the optical range
Статья научная
In connection with the emergence of abnormal situations at the stage of launching space vehicles (SV) for various purposes (AngoSat-1, Telkom-3, Phobos-Grunt, etc.), the problems of timely detection of such situations and remote monitoring of the technical condition of SV are of vital importance. To assess the feasibility of solving this class of problems with the use of optronic equipment (OE), it is necessary to have a priori information on the spectroenergetic characteristics (SEC) of a SV and associated backgrounds for the projected angles and conditions of observation in the operational spectral ranges of the OE taking into account the illumination by the Sun and the Earth. Due to the adapta- bility of mathematical modeling to the high degree of variability of the above factors, this method can be considered as a rational one for obtaining dynamic SEC (signatures) of SV for observation conditions that change during an or- bital flight. The technology of SEC modeling of space objects (SO) with the use of FemRad dedicated software (DS) is pre- sented, which provides the production of SO SEC taking into account the indicatrices of the scattering of optical radia- tion from materials and coatings of the external surface of the object, the dynamics of its thermal regime and the condi- tions of illumination by the Sun and Earth during the orbital flight. The advantage of the presented technology is the compatibility of the developer’s own software solutions with the widespread application programs of finite element analysis. In particular, the known CAD and CAE tools - SolidWorks, ANSYS, Gmsh - are used to develop grid geometric 3D models of SO. The method for parametric approximation of the measured indicatrices of scattering of optical radiation from mate- rials and coatings of SO on the basis of a given model of roughness is considered. The main provisions of the DS meth- odology for calculating the heat flux of the “Earth-atmosphere” system, as well as the fluxes of reflected and scattered solar radiation falling on the SO in the range 0.2-20 µm, are presented. The results of modeling the dynamic SEC of a typical SO in the infrared (IR) range are given as an illustration of the application of the DS.
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Статья научная
One of the promising areas for improving the methods of manufacturing structural elements of rocket and space technology is the use of selective laser melting technology which represents a unique opportunity to manufacture metal products by melting powder and producing a one-piece solid phase structure. However, pores and other structural defects can appear in the formed element during laser sintering which causes a decrease in the strength characteristics of the parts produced. An important step in the additive technologies introduction is the development of methodology for the preliminary prediction of the strength characteristics of manufactured structural elements under the influence of mechanical loads with the help of mathematical modeling. The methodology for estimating the material strength reduction of a rocket-space technology element obtained using additive technologies by simulating a porous structure and calculating the characteristics of the stress-strain state is presented. The proposed mathematical model and the methodology for calculating the specimen loading on the basis of the distortion energy theory allow calculating the stress-strain state in the process of numerical simulation for different values of the pore diameter. The reduction in yield strength due to the material porosity of the part is estimated using a coeffi- cient equal to the ratio of equivalent stresses arising when a load is applied to a specimen manufactured using traditional and additive technologies. The value of the introduced coefficient characterizes the structure of the grown product and is considered as a function of the random arrangement of pores in the specimen under study. The appearance of pores is the result of a combination of factors: the composition and dispersion of the original metal powder, feed rate, removal distance and laser power during sintering, part orientation and sintering direction, the height of the level of powder deposited on a special base before sintering, etc. The paper evaluates the reduction in strength for the working part of a series of tensile test specimens grown from metal powder of different dispersity. The non-linear nature of the dependence of the yield strength on the particle diameter of the original metal powder is established. The maximum value of the yield strength corresponds to the specimen with the minimum value of the total surface area of the pores.
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Статья научная
A design of controlled diffractive optical elements based on electro-optic effect is suggested. The influence of the electro-optical crystal orientation, the direction of light wave propagation and the electric field distribution on the characteristics of controlled diffractive optical elements is considered. The efficiency indicators of controlled diffraction elements structure and material are proposed and their values for the basic elements are calculated.
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Статья научная
The article discusses formalization of the problem of heterogeneous distributed information processing systems (HDIPS) software and hardware configuration management. A formal description of possible optimality criteria for the HDIPS software and hardware configuration is given. The HDIPS model in terms of queuing theory is proposed. The problem of allocating the HDIPS computational resources is formulated as a transport problem according to time criterion with atomic needs. The algorithm for solving this problem is proposed and the boundaries of its applicability to the HDIPS are determined. To meet the selected optimality criterion, the analysis of the HDIPS software and hardware configuration applying its formal model, using the queuing theory methods is presented. HDIPS is presented as a queuing network, where each computing node and route control unit is a mass service system. The problem of computing resource allocation in HDIPS is presented as a transport problem according to the time criterion with atomic needs. The least time algorithm for indivisible needs takes into account the indivisibility condition.
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Multi-grid finite elements in calculations of multilayer oval cylindrical shells
Статья научная
The method of finite elements (FEM) is actively used in calculations of composite shell constructions (rotation shells, circle and oval cylindrical shells), which are widely used in space-rocket and aviation equipment. To calculate multi-layer oval cylindrical shells three-dimensional curvilinear Lagrange multi-grid finite elements (MGFE) are suggested. When building a k-grid finite element (FE), k nested grids are used. The fine grid is generated by the basic split of MGFE that takes into account its complex heterogeneous structure and shape. On k-1 large grids the move functions used for decreasing MGFE dimension are determined. The stress-strain state in MGFE is described by the elasticity theory three-dimensional task equations (without introduction of additional hypotheses) in local Cartesian coordinates systems. The procedure of building shell-type Lagrange MGFE with the use of Lagrange polynomials presented in curvilinear coordinate systems is demonstrated. With the size reduction of discrete models MGFE have constant thickness equal to the thickness of the shell. The Lagrange polynomials nodes coincide in thickness with the MGFE large grid nodes and are located on the shared borders of different module layers. The use of such MGFE generates approximate solutions sequences that uniformly and quickly converge to precise solutions. The main advantages of MGFE are as follows: they form discrete models with the dimension 102-106 times smaller than the basic models dimension and they generate small error solutions. Examples of calculations are given for four- and three-layer oval shells of various thickness and shape under both uniform and local loading with the use of 3-grid FE. Comparative analysis of the obtained solutions with the solutions built with the help of the software package ANSYS shows high efficiency of the suggested MGFE in calculations of multi-grid oval shells.
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Статья научная
In this paper we apply multi-objective optimization approach to find a Pareto optimal ensemble of neural network classifiers, which is used for solving the emotion recognition problem. Pareto set of neural networks is found by optimizing two conflicting criteria: maximizing emotion classification rate and minimizing the number of neural network neurons. We implemented several ensemble fusion schemes - voting, averaging class probabilities and adding auxiliary meta-classification layer. The number of audio and video features extracted from raw video sequences for analysis is quite large, so we also applied multi-objective approach in order to find the optimal subset of features. The optimized criteria in this case are maximizing classification rate and minimizing the number of features. The multi-objective approach to neural network parameter optimization and to feature selection was compared to the classic single-objective optimization approach on several datasets. According to experimental results, multi-objective approach to neural net optimization provided on average 7.1 % higher emotion classification rate than single-objective optimization. Applying multi-objective approach to feature selection as well helped to improve the classification rate by 2.8 % compared to single-objective approach, by 5.4 % compared to using principal components analysis, and by 13.9 % compared to not using dimensionality reduction at all. Taking into account the obtained results, we suggest using multi-objective approach to machine learning algorithms optimization and feature selection in further research connected with emotion recognition problem and other complex classification tasks.
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Статья научная
Feature selection is a quite important step in data analysis. Extracting relevant attributes may not only decrease the dimensionality of the dataset and, consequently, reduce time costs spent on the next stages, but also contribute to the quality of the final solution. In this paper we demonstrate some positive effects of the usage of a heuristic feature selection scheme which is based on a two-criterion optimization model. The approach proposed is applied to the speech-based emotion recognition problem, which is currently one of the most important issues in human-machine interactions. A number of high-dimensional multilingual (English, German, Japanese) databases are involved to investigate the effectiveness of the technique presented. Three different multi-objective genetic algorithms and their cooperative modifications are applied as optimizers in combination with classification models such as a Multilayer Perceptron, a Support Vector Machine and Logistic Regression. In most cases we may observe not only a dimensionality reduction, but also an improvement in the recognition quality. To avoid choosing the most effective multi-objective genetic algorithm and the best classifier, we suggest applying a heterogeneous genetic algorithm based on several heuristics and an ensemble of diverse classification models.
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Multigrid finite elements in the calculations of multilayer cylindrical shells
Статья научная
An effective numerical method for calculating linearly elastic multilayer cylindrical shells under static loading implemented on the basis of Finite Element Method (FEM) procedures using the multilayer curved Lagrangian multi- grid finite elements (MFE) of the shell type was proposed. Such shells are widely used in rocket-space and aircraft engineering. MFE are developed in local Cartesian coordinate systems based on small (basic) shell partitions that take into account their heterogeneous structure, irregular shape, combined loading and fixing. The stress strained state (SSS) in the MFE was described by the equations of the three-dimensional elasticity problem without using the addi- tional kinematical and static hypotheses, which allow one to use MFE for the shells of various thicknesses to be calcu- lated. The procedure of constructing the Langrage polynomials in local curvilinear coordinate systems used to develop the shell MFE is presented. The displacements in the MFE were approximated by the power and Lagrange polynomials of different orders. When constructing a n -grid finite element (FE), n ≥ 2, n-nested grids were used. The fine grid was generated by the basic partition of the MFE; the other (coarse) grids were used to reduce its dimension. According to the method, the nodes of the coarse MFE grids are located on the common boundaries of the different modular layers of the shell. The proposed law of the expansion in the number of discrete models using MFE with a constant thickness, multiple of the shell thickness, provides a uniform and rapid convergence of approximate solutions, allowing one to frame solutions with a small error. Multigrid discrete models have 103…106 times less unknown MFE than the basic ones. The implementation of the MFE for multigrid models requires 104…107 times less computer storage space than for the reference models, which allows one using the proposed method to calculate some large shells. An example of calculating a multilayer cylindrical local loading shell of irregular shape was given. In the calculation, three-grid shell - type FE, developed on the basis of the reference models having from 2 million to 3.7 billion of the nodal MFE unknowns were used. To study the approximate solution convergence and error, a well-known numerical method was used.
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Multilevel evaluation of quality interactive electronic technical manuals for aviation technology
Статья научная
The method of multi-level quality assessment of interactive electronic technical manuals (IETM) for aircraft con- tains the main approaches, methodological and logical-mathematical tools for the implementation of multiparameter evaluation of the quality of electronic content of these manuals. The paper postulated that the goal of assessing the quality of IETM for aviation equipment is to obtain a consolidated conclusion on the degree of satisfaction of the need to create interactive electronic technical manuals in the conditions of vagueness of the initial expert data used for evaluation. It is shown that the quality assessment of interactive electronic technical manuals for the operation and repair of aviation equipment is obviously linked to non-numeric or “soft” measurements, due to the fuzzy nature of the initial qualimetric data obtained from an expert. In this version, “measurement” should be understood as a manipulation in which some strictly ordered quality gradations correlate in accordance with the IETM for the operation and repair of aviation equipment properties. In the role of quantitative measurement results, not only real numbers are considered, but also other algebraic groups that necessarily have an order relation between their elements, that is, a similarity of the inequality relation between numbers. The multi-level quality assessment of interactive electronic technical manuals for aeronautical engineering consists of the following steps: 1. Imagery of numerical vectors of values of elementary quality indicators; 2. Calculation of ranks that determine the significance of quality indicators in their compositions based on fuzzy and (or) insufficient initial data on the compositional significance of more particular indicators in the composition of more aggregated indi- cators: 3. Calculation of elementary indicators values and ratings of importance based on numerical vectors, for the analyzed performance of IETM on the operation and repair of aircraft, the values of the integral quality indicator, as the weighted arithmetic average of mathematical similar to a particular indicators.
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Multilingual technology. System aspects of its organization and usage
Статья научная
System aspects of multilingual adaptive-training technology organization and usage to train multilingual vocabulary are considered. Information vocabulary support of the technology is presented. Its realization is directed at the architectural layer of rules primary, corresponded to the functions of adaptive-training model and multilingual term basis.
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Necessity and challenges of the Russian financial sector modernization
Статья научная
In the article the possibilities of the Russian financial sector modernization for entering the sustainable development trajectory are considered. It touches upon the issues of the division of the Bank of Russia into two functions – a monetary regulator and a body responsible for the creation of a macroprudential supervision system. The questions of the state-owned banks share growth in the Russian banking system, the establishment of the adequate minimum level of capital and the creation of a three-level banking system are examined.
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New exact solutions which describe 2-dimensional velocity field for Prandtl’s solution
Статья научная
New velocity fields are found for the well-known Prandtl's solution which describes pressing of a thin layer of plastic material between two parallel stiff and rough plates. The method of construction of other velocity fields is considered.
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Non-parametric algorithms of reconstruction of mutually ambiguous functions from observations
Статья научная
We consider the task of reconstruction of the regression function from observations with errors. Under parametric uncertainty conditions this problem is solved in the following sequence: first the type of regression function with accu- racy to parameters is set, then the next stage is the estimation of these parameters based on training sample elements. The main problem that arises is choosing a parametric structure, i. e. the choice of parameters with an accuracy to the vector of parameters. At the same time more or less inaccuracy can be allowed, descriptions of many variables func- tions with accuracy to parameters cause particular difficulties. Another known way of solving such problems, which is the nonparametric estimation of regression function from observations, in this case the stage of choosing a parametric equation of the regression function is missing. A number of publications is devoted to this area including monographs where the results are in most cases related to the asymptotic properties of the regression function. The article considers the task of reconstruction of mutually ambiguous functions of many arguments from observa- tions with random errors in the conditions of nonparametric uncertainty. This problem has been insufficiently studied, although it has a significant importance in the identification and control of objects of a Wiener and Hammerstein class. The control theory widely uses already known mutually ambiguous specifications that describe the work of items with a loop of hysteresis, backlashes and others. Some modifications of nonparametric estimates of mutually ambiguous fea- tures including multidimensional are given. A series of computing experiments have been conducted where for simplic- ity reasons the simpliest mutually ambiguous curves were taken, parametric structure of these curves for the algorithms was unknown, only observation was known. Numerical studies covered two cases: different sample sizes and various disturbances affecting the studied processes. The reconstruction of mutually ambiguous dependency plays an important role in the development of robots and various robotic systems moving on in an undefined or unknown terrain. As sepa- rate blocks the considered algorithms can be useful in devices that are used in the aerospace industry.
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Nonparametric identification of dynamic systems under normal operation
Статья научная
The research gives nonparametric identification algorithms under the conditions of incomplete a priory information. The identification case differs from the previously known ones due to the fact that, besides the control action, an uncontrollable variable, but a measurable one, impacts on the object input. In contrast to parametric identification, the research considers the situation when the equations describing dynamic objects are not given with accuracy to the parameters. In this case, there are some features to study while getting the recovery characteristics of various object channels. The main characteristic is that the transition response of a channel is taken when the other channel is in a stable position. Moreover, the identification problem is analyzed under normal object operation, opposite to the previously known nonparametric approach based on Heaviside function input to the object and further Duhamel integral application. An arbitrary signal is input to the object during normal operation as a result we have a corresponding response of the object output. It should be noted that the measurements of the input and output variables are carried out with random noise. As a result, we have a sample of input-output variables. As linear dynamical system can be described by the Duhamel integral, with known input and output object variables, corresponding values of the weight function can be found. This is achieved by discrete representation of the latter. Having such realization, nonparametric estimate of the weight function in the form of the nonparametric Nadaraya-Watson estimate is used later. Substituting this with the Duhamel integral, we obtain a nonparametric model of a linear dynamical system of unknown order. The article also describes the case of constructing nonparametric model when a delta-shaped function is input to the object. It is interesting to find out how delta-shaped function might differ from the delta function. The weight function is determined in the class of nonparametric Nadaraya-Watson estimates. Previously proposed nonparametric algorithms consider the case when Heaviside function is applied to the object; this narrows the scope of nonparametric identification practical use. It is important to construct nonparametric model of the dynamic object under conditions of normal operation.
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Numerical investigation of the problem of cohesive running soils punching shear
Статья научная
A special mathematical model generalizing the classical model of the elasticity theory is used for the analysis of directions of the deformations localization in samples of soils with different strengths. Numerical solution of the problems is carried out by means of iterative process, the equations of the elasticity theory with initial stresses being solved on each step thereof on the basis of the finite-element method.
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Статья научная
Method of improvement of operational properties of surfaces is considered. Under study is the applicability of high- frequency electromagnetic field for metal heating and melting with a view to its subsequent modification. 2D numerical modeling of the processes during the modification of the substrate surface metal layer is carried out. The substrate surface is covered with a layer of specially prepared nano-size particles of refractory compounds, which are active crystallization centers after the penetration into the melt. The distribution of the electromagnetic energy in the metal is described by empirical formulas. The proposed mathematical model is used to consider the processes including heat- ing, phase transition and heat transfer in the molten metal, the nucleation and growth of the solid phase in the presence of a modifier material in the melt. Melting of the metal is considered at the Stephan’s approximation, and during solidi- fication all nano-size particles are assumed to be centers of volume-consecutive crystallization. The flow in the liquid is described by the Navier-Stokes equations in the Boussinesq approximation. The movement of the markers models the distribution of nano-size particles in the melt. According to the results of numerical experiments, the flow structure in the melt was evaluated versus the characteristics of induction heating and the amount of surface-active impurities in the metal. The modes of the induction-pulse action are detected: they promote creating the flows for the homogeneous dis- tribution of modifying particles in the melt. Found that the application of high frequency electromagnetic field for heat- ing and melting of metals allows to modify the metal deeper in comparison with the use of a laser.
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OLAP-технология как средство мониторинга образовательного процесса
Статья научная
Без тщательного мониторинга образовательного процесса в высшем учебном заведении невозможно всесторонне оценить достижения студента. В целях мониторинга предложено использовать технологию многомерного анализа данных OLAP. Рассмотрен пример внедрения OLAP-технологии в учебный процесс на уровне дисциплины.
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Статья научная
The development of oil deposits in the Evenki Autonomous Area is connected with study of the properties and quality index of extracted crude oil and oil fuels. The ecological requirements to oil products become more stringent today. Measures for lower oil extraction costs, oil processing and equipment exploitation are also to be met. Therefore, the study of crude oil and oil fuel properties is very important.
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Статья научная
The possibility of factorial analysis application in theestimation of the state of information systems security is considered. The procedure of selection and classification of factors as well as calculation of factors influence on the resultant indicator size are described.
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On calculation of moment of resistance in canals of low-rate centrifugal pumps
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In our calculations we make use of the system of equations for turbulent boundary-layer pulses in projections onto the cylindrical coordinate axes. We have performed transformations and integration of equations in the presence of accepted assumptions on the flow core motion pattern and compared the theoretical results with the empirical data.
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