Информатика, вычислительная техника и управление. Рубрика в журнале - Сибирский аэрокосмический журнал
On necessary and sufficient conditions of simply reducibility of wreath product of finite groups
Статья научная
A finite group is considered to be real if all the values of its complex irreducible characters lie in the field of real numbers. We note that the above reality condition is equivalent to the fact that each element of the group is conjugate to its inverse. A finite group is called simply reducible or a SR-group if it is real and all the coefficients of the decomposition of the tensor product of any two of its irreducible characters are zero or one. The notion of a SR-group arose in the paper of R. Wiener in connection with the solution of eigenvalue problems in quantum theory. At present, there is a sufficient amount of literature on the theory of SR-groups and their applications in physics. The simplest examples of SR-groups are elementary Abelian 2-groups, dihedral groups, and generalized quaternion groups. From the point of view of a group theory questions of interest are connected first of all with the structure of simply reducible groups. For example A. I. Kostrikin formulated the following question: how to express the belonging of a finite group to the class of SR-groups in terms of the structural properties of the group itself. Also, for a long time it was not known whether a simply reducible group is solvable (S. P. Stunkov's question). A positive answer to the last question was obtained in the works of L. S. Kazarin, V. V. Yanishevskiy, and E. I. Chankov. Questions concerning the portability of the properties of a group to subgroups, factor groups, and also their preservation in the transition to direct (Cartesian) and semidirect products or wreath products are always of interest. The paper proves that the reality of H is the necessary condition of simply reducibility of the wreath product of the finite group H with the finite group K and the group K must be an elementary Abelian 2-group. We also indicate sufficient conditions for simply reducibility of a wreath product of a simply reducible group with a cyclic group of order
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On remote sensing of the Earth by spacecraft
Статья научная
Remote sensing is a process which implies collecting information about an object. Due to their properties, satellite images are widely used in both practical and scientific fields. Satellite imagery is used in research aimed at the comprehensive study of natural resources, the dynamics of natural phenomena, and in the tasks of environmental protection. Special attention is paid to the use of space information for daily operational monitoring of the state of the environment in the implementation of geo-ecological monitoring of regions. In particular, this poses the problem to find the regions of the earth's surface with the characteristics determined by the considered parameters using the values of established parameters at certain points of the earth's surface. In this paper, we consider the special case of this problem when the given four points of the earth's surface determine the regions of the earth's surface (the so-called kernels of generalized squares) that have a specified configuration (square).
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Optimizing the readability of tests generated by symbolic execution
Статья научная
Taking up about half of the development time, testing remains the most common method of software quality control and its disadvantage can lead to financial losses. With a systematic approach, the test suite is considered to be complete if it provides a certain amount of code coverage. At the moment there are a large number of systematic test generators aimed at finding standard errors. Such tools generate a huge number of difficult-to-read tests that require human veri- fication which is very expensive. The method presented in this paper allows improving the readability of tests that are automatically generated using symbolic execution, providing a qualitative reduction in the cost of verification. Experi- mental studies of the test generator, including this method as the final phase of the work, were conducted on 12 string functions from the Linux repository. The assessment of the readability of the lines contained in the optimized tests is comparable to the case of using words of a natural language, which has a positive effect on the process of verification of test results by humans.
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Restoration of information on the group by the bottom layer
Статья научная
The question of the possibility of restoring information on the group by its bottom layer is considered. The problem is classical for mathematical modeling: restoration of missing information on the object employing part of the saved data. This problem will be solved in the class of layer-finite groups. A group is said to be layer-finite if it has a finite number of elements of every order. This concept was first introduced by S. N. Chernikov. It appeared in connection with the study of infinite locally finite p-groups in the case when the center of the group has a finite index in it. The bottom layer of the group G is the set of its prime order elements. By the bottom layer of the group, you can sometimes restore the group or judge about the properties of such a group. Among these results one can name those that completely describe the structure of the group by its bottom layer, for example: if the bottom layer of the group G consists of elements of order 2 and there are no non-unit elements of other orders in the group, then G is the elementary Abelian 2-group. V. P. Shunkov proved that if the bottom layer in an infinite layer-finite group consists of one element of order 2, then the group G is either a quasicyclic or an infinite generalized quaternion group. We will restore the information on the group by its bottom layer. This problem will be solved in the class of layer-finite groups. Group G is said to be recognizable by the bottom layer if it is uniquely recovered by the bottom layer. Group G is said to be almost recognizable over the bottom layer if there is a finite number of pairwise nonisomorphic groups with the same bottom layer as in group G. Group G is said to be unrecognizable by the bottom layer if there is an infinite number of pairwise nonisomorphic groups with the same bottom layer such as in group G. In this work conditions under which the group is recognized align the bottom layer have been established.
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Статья научная
The research work presents the results of computer simulation of mass loading influence represented by two metal layers on variations in the dispersion modes of the Lamb and SH elastic waves phase velocity in the piezoelectric lay- ered structures Me/ZnO/Me and Me/AlN/Me depending on the elastic wave frequency and the ratio of the metal layer thickness to the piezoelectric layer thickness. The studied materials of the piezoelectric layers have a set of such sig- nificant properties as large values of the electromechanical coupling coefficient for piezoelectrics and significant val- ues of phase velocities for bulk waves and surface acoustic waves. Aluminum (Al) and molybdenum (Mo) are consid- ered as metal layer materials, which are most often used in the manufacturing of acoustic electronic devices. For both types of structures it was revealed that only the Lamb elastic wave modes have localized maxima of S sensitivity. It was found that the value of changing in the elastic wave phase velocity depends on the ratio of the metal layer acoustic im- pedance and the piezoelectric plate material. The maximum sensitivity values of elastic wave modes are achieved with Al/AlN/Al configuration, i.e., in a system with low acoustic impedance values of the bulk longitudinal wave for the layer and piezoelectric plate materials. The results of the simulation can be used in the development of various acousto- electronic devices, including some components of the rocket and space technology electronic base.
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Статья научная
The S-box is the most important component of modern cryptographic algorithms which largely determines the quality of cryptographic transformation. The modern method of estimating the S-boxes quality employs their representation as component Boolean functions to which cryptographic quality criteria are applied. Such criteria include: nonlinearity, correlation immunity, an error propagation criterion, and a strict avalanche criterion. Nevertheless, it is obvious that a cryptanalyst is not constrained in the ways of representing the cipher components, in particular, using the functions of many-valued logic. The design features of modern cryptographic algorithms allow their representation in the form of 4-logic functions, which determines the need to research cryptographic properties of the S-boxes represented as component 4-functions. In the literature today there are methods for measuring the nonlinearity of 4-functions; nevertheless, there are no similar methods for researching the differential properties of 4-functions, in particular, involving their compliance with the strict avalanche criterion. In this paper the strict avalanche criterion is generalized to the case of 4-functions and the compliance of the S-boxes component 4-functions of the “Magma” cryptoalgorithm to the strict avalanche criterion has been researched. All balanced 4-functions of length N = 16 satisfying the strict avalanche criterion were synthesized using the restricted brute-force method. The basic properties of the constructed class of 4-functions are determined, and bijective S-boxes based on them are constructed. It has been established that S-boxes of length N = 16 satisfying the strict avalanche criterion, both in terms of component Boolean functions and in terms of 4-functions, also possess optimal nonlinear properties. This circumstance allows us to recommend S-boxes satisfying the strict avalanche criterion of component 4-functions for use in modern cryptographic algorithms.
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Structure, network protocols of the Internet of things for quality production control
Статья научная
The subject of research is the model and structure of the Internet of things (IoT) network for product quality control in industry and agriculture. The purpose of the article is to analyze communication protocols and structures of IoT networks. The method of analysis and structural design of IoT networks is applied. The field of application is automation of monitoring products of enterprises of the aerospace industry. The article provides an overview and analysis of existing IoT technology; it considers the protocols and composition of IoT networks, and provides variations in the structures of building such networks. 4 levels of IoT architecture are described, as well as the communication protocols are used. The directions of building the Internet of things network for product quality control are defined. A multi-agent model of such system is presented, for the implementation of which the structure of the IoT network is given. The structure of a multigent system (MAS) for monitoring product quality in industry and agriculture includes many agents, such as product quality agents, communication agents, database agents, agents for analyzing information received from sensor agents, and decision-making agents. This MAS implements functions to ensure the required class of product quality and it is based on building a local network of the Internet of things. The research proposes an algorithm for processing information in such an IoT network. Analyzers (sensors) product qualities will be periodically polled and their values will be recorded in the server database. The decision-making subsystem sends data on product quality compliance to the enterprise administrator on a mobile device. The server structure is implemented using cloud IoT platforms, for which a brief overview is provided. The one IoT network implementation is developed using LTE NB-IoT technology. This approach can be used in the aerospace industry for product quality control within automation 4.0.
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System analysis of dynamic problems of anisotropic plasticity theory
Статья научная
Dynamic problems are the least studied area of plasticity theory. These problems arise in various fields of engineering and science, but the complexity of the original differential equations do not allow to develop accurate solutions and correctly solve numerical boundary value problems. This is even more typical of dynamic equations of anisotropic plasticity. Anisotropy reduces the group of symmetries allowed by the equations, and therefore narrows the number of invariant solutions. One-dimensional dynamic plasticity problems are well studied, but two-dimensional problems cause insurmountable mathematical difficulties due to the nonlinearity of the basic equations, even in the isotropic case. The study of the symmetries of the plasticity equations allowed us to find some exact solutions. The most known solution was found by B. D. Annin, who described the unsteady compression of a plastic layer made of isotropic material by rigid plates. Annin's solution is linear in two spatial variables, however, it includes arbitrary functions of time. Symmetries are also used in the proposed work. Point symmetries are first calculated for dynamic plasticity equations in the anisotropic case and are presented in the paper. The Lie algebra generated by the found symmetries appeared to be infinite-dimensional. This circumstance made it possible to apply the method of constructing new classes of nonstationary solutions. Symmetry can transform the exact solution of stationary dynamic equations in non-stationary solutions. The framed solutions include arbitrary functions and arbitrary constants. The outline of the article is as follows: according to the method of Lie group of point symmetries allowed by the equations of anisotropic plasticity is calculated. Two classes of new stationary invariant solutions are framed. These stationary solutions, by means of transformations generated by point symmetries, are transformed into new non-stationary solutions. In conclusion, a new self-similar solution of unsteady equations of anisotropic plasticity is framed; Annin's solution is generalized for the anisotropic case. The framed solutions can be used to describe the compression of plastic material between rigid plates, as well as to test programs, designed to solve anisotropic plastic problems.
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The Cayley graphs of finite two-generator burnside groups of exponent 7
Статья научная
For the first time the definition of the Cayley graph was given by the famous English mathematician Arthur Cayley in the XIX century to represent algebraic group defined by a fixed set of generating elements. Now the Cayley graphs are widely used both in mathematics and in applications. In particular, these graphs are used to represent computer networks, including the modeling of topologies of multiprocessor computer systems (MCS) - supercomputers. This is due to the fact that Cayley graphs possess many attractive properties such as regularity, vertex transitive, small diame- ter and degree at a sufficiently large number of vertices in the graph. For example, such a basic network topology as the ”ring”, ”hypercube” and ”torus” are the Cayley graphs. One of the widely used topologies of MCS is a k- dimensional hypercube. This graph is given by a k-generated Burnside group of exponent 2. This group has a simple structure and is equal to the direct product of k copies of the cyclic group of order 2. Now the Cayley graphs of groups of exponent 3, 4, and 5 have already been studied. In this paper we research the Cayley graphs of some finite two- generated Burnside groups of exponent 7. The computation of the diameter of the Cayley graph of a large finite group is a solvable but very difficult problem. In the general case the problem of determining the minimal word in a group is NP-hard ( nondeterministic polynomial ). Thus, in the worst case, the number of elementary operations that must be per- formed to solve this problem is an exponential function of the number of generating elements. Therefore, to effectively solve problems on Cayley graphs having a large number of vertices, it is necessary to use MCS.
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Статья научная
In practice problems, which consist in the search of the best (optimal) solution according to the different irredundant and contradictory (conflicting) criteria, called multi-objective problems, are of frequent occurrence. One of the most commonly used methods for solving this kind of problems consists in combination of all criteria into the single one by using some linear relation. However, despite the simplicity of this method, solving problems with its help may cause other problems related to the determination of the mentioned linear combination, namely related to the determination of the weight coefficients for each criterion. The incorrect selection of these coefficients may lead to non-optimal solutions (according to the Pareto theory). In this regard, recently various population-based algorithms have been proposed for solving the described problems, which are the modifications of these population-based algorithms for solving single- objective optimization problems. This article describes the developed modifications of the Differential Evolution algorithm (DE) for solving multi-objective unconstrained optimization problems based on the well-known NSGA (Nondominated Sorting Genetic Algorithm) and MOEA/D (Multiobjective Evolutionary Algorithm Based on Decomposition) schemes, which use the Pareto theory. The investigation into the efficiency of the Differential Evolution algorithm for solving multi-objective optimization problems in relation to the chosen mutation operator of the original DE algorithm and to the multi-objective scheme was conducted. The developed modifications were tested by using some well-known multi-objective real-valued optimization problems with 30 variables, such as ZDT1, ZDT2, ZDT3, etc. The practical problem of spacecraft control contour variant choice was solved as well. The experimental results show that better results were achieved by the Differential Evolution algorithm with the simplest mutation operators combined with the NSGA scheme. Thus, the applicability of the described modification for solving practical multi-objective optimization problems was demonstrated.
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To nonparametric identification of dynamic systems under normal operation
Статья научная
The problem of nonparametric identification of linear dynamic objects is being investigated. In contrast with para- metric identification, the case is analyzed when equations describing a dynamic object are not specified according to the parameters. Moreover, the identification problem is analyzed under normal object operation, opposite to the previ- ously known nonparametric approach based on Heaviside function input to the object and further Duhamel integral application. An arbitrary signal is inputted to the object during normal operation and weight function realizations are represented by observations of input-output object variables measured with random interferences. 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 dis- crete 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 into the Duhamel integral, we obtain a nonparametric model of a linear dynamical system of unknown order. The article also describes the case of nonparametric model constructing when a delta-shaped function is inputted to the object. It was interesting to find out how delta-shaped function might differ from the delta function. The weight function was determined in the class of nonparametric Nadaraya-Watson estimates. Nonparametric models were investigated by means of statistical modeling. In general, nonparametric models have shown sufficient efficiency in terms of accuracy prediction by nonparametric model in relation to the actually measured output of the object. Evi- dentally, the accuracy of nonparametric models reduces with the growing influence of interference from the meas- urement of input-output variables or the discreteness of their measurement. Previously proposed nonparametric al- gorithms consider the case when Heaviside function was applied to the object, which narrows the scope of nonpara- metric identification practical use. It is important to construct nonparametric model of a dynamic object in condi- tions of normal operation.
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To the task of controlling a group of objects on the basis of information technologies
Статья научная
To participate the TPP with cross-section communications in the general primary frequency control, it is necessary to have a working main regulator. The main regulator is designed to maintain the steam pressure in the major steam line of the TPP at a given level, which is a difficult task. At the TPP with cross-connections, the steam produced by the boilers enters the major steam line. To maintain the pressure in the major steam line, it is necessary to control the heat load of the working boilers. Traditional solutions to construct the main regulator found no use, as have a number of disadvantages, not allowing exploiting a system of automatic control. Looking at the steam pressure control system in the major steam line from the bottom to up, it is possible to identify disadvantages that prevent the effective operation of the main regulator at each level. At the lower level of the main regulator, there are controllers of heat load of boilers, built according to the scheme task-heat. Heat load controllers are designed to maintain heat release in the boiler fur- nace at the required level. The heat signal is the sum of the signals for the steam flow of the boiler and the rate of change in the steam pressure in the boiler drum. Such a structure does not allow maintaining the invariance of the heat signal under external disturbances effectively, as sharp changes of the steam pressure in the major steam line lead to a "false" operation of the controllers. At the upper level there is the main regulator itself, which maintains the steam pressure in the major steam line at a given level and corrects the tasks to the controllers of the heat load of the boilers. The simultaneous identical effect on the heat load of the boilers cannot be optimal from the point of view of the criteria for assessing the quality of regulation, since the dynamic properties of the boilers, such as the gain, the transition time constant and the transport delay are individual for each boiler. However, in 2006-2008, the attempt to build an updated main regulator that takes into account the shortcomings of the traditional scheme was made. The basis of the structure of the main regulator is still parametric and, as a result of ten-years’ experience, shortcomings in the operation of the updated main regulator were identified. The shortcomings, in most cases, consist in need of frequent corrections of adjusting coefficients of system because of the change of dynamic properties of an object during the operation. In fact, the same problems related to the parametric structure of the regulator remain. Up-to-date information technologies made it possible to introduce adaptive process control systems that allow to count an extended number of signals entering the system and to form control actions, based on both current and historical data of the technological process. The use of the latest information technologies and modern hardware in the control of complex multi-connected units that solve not only the problems of process control, but also the problem of improving the economic and environmental performance of enterprises, should become a new step in the development of automatic control systems.
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Two-dimensional thermal model of the thermal control system for nonhermetic formation spacecraft
Статья научная
Based on the proposed computational model including a two-dimensional system of equations of thermal balance characteristic of the surface of thermal control system of nonhermetic formation spacecraft the algorithm and the cal- culation program of the temperature control system are developed. It allows to calculate integrated thermal parameters and conduct simulations of the system response. We consider the case of a two-dimensional problem, when arising tem- perature gradients in the transverse direction (Y-axis) and longitudinal direction (X-axis) is taken into account, while the conductive heat transfer inside the skin along the X-axis of the profile of the liquid circuit of the thermal control system is neglected. In this case the transverse gradient (along the Y-axis) is formed by Fourier heat conduction equa- tions through characteristic surfaces, while the longitudinal gradient (along the X-axis) is determined by the heat and mass transfer processes by the refrigerant flow in the liquid ring circuit. The number of docking thermal balances (equations) and, accordingly, the determined temperatures are correlated by the constructive elements of the spacecraft thermal control system: radiation surfaces (N - North, S - South); structural honeycomb panels; heat pipes; liquid circuit.
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Use of conservation laws to solve the problem of load wave in an elastoplastic rod
Статья научная
The process of propagation of plastic deformations in a semi-infinite elastic plastic rod caused by dynamic loading applied to the end of the rod, which is not decreasing in time, is considered. The equations are written in the Lagrangian coordinate system. It is assumed that during deformation there is no lateral bulging of the rod and that the influence of transverse deformations of the rod on the process of propagation of longitudinal waves is negligible. At the initial moment, the rod is in a deformed and dormant state. Small deformations of the rod are considered. The density of the rod during deformation does not change. The only non-zero component of the stress tensor will be the component along the ox axis, non-zero components of the strain tensor will be the components along the Ox, Oy axes. As a result, a system of two quasilinear first-order homogeneous equations is constructed. The equations are hyperbolic. They are built for performance and ratio on them. Next, the equations are written in terms of Riemann invariants. For the equations constructed, the conservation laws are found in the case when the current remaining depends only on the functions sought. As a result, a system of linear equations with coefficients depending only on the required functions is obtained. Тhe construction of conservation laws is reduced to the solution of the boundary value problem for the known Euler-Poisson-Darboux equations. This problem is solved with the help of Riemann functions. The conservation laws allowed us to find the coordinates of the points of intersection of characteristics, and thus to solve the problem. In conclusion, the article considers the case when one of the characteristics crosses the line on which the initial conditions are given. In this case, as is known, the Cauchy problem cannot be solved. This leads to a procedure which, with the help of conservation laws, makes it possible to find out the solvability of the Cauchy problem. It is reduced to the solution of a simple integral equation by the method of successive approximations.
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Using signals of navigation satellites in the monitoring of the earth covers
Статья научная
The features and capabilities of remote sensing of earth covers by means of signals of navigation satellites are pre- sented. The methods of reflectometry of the surfaces of earth covers and radioscopy of forest canopy are described. The options for using the signals of GLONASS, GPS systems are considered. Test measurements of interference diagrams were carried out on 5 test platforms from heterogeneous soil surfaces: salt marshes and asphalt; water surfaces of sa- line and freshwater bodies in summer, including ice cover of small thickness in the period of autumn freeze-up. The method of radioscopy helped obtain the data on the spatial and temporal characteristics of attenuated signals of the GLONASS and GPS satellites in the pine forest. Estimates of the linear attenuation coefficients of the signals passing through a forest canopy with a coordinate reference were made. The results obtained are the basis for the development of methods and technologies for continuous monitoring of the characteristics and state of earth covers by means of sig- nals of navigation satellites for solving a wide range of applied tasks.
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Автоматизированная настройка регуляторов для АСУТП в среде визуального моделирования Simintech
Статья научная
Для успешного протекания технологического процесса требуется постоянное поддержание технологических параметров на требуемом уровне, что обеспечивается применением автоматизированных систем управления технологическими процессами (АСУТП). Классическим решением данной задачи является применение управляющих устройств различного типа, выбор которых напрямую зависит от рассматриваемой системы и предъявляемых к ней требований. Лидирующую позицию среди регуляторов АСУТП последние десятилетия занимает пропорционально-интегрально-дифференцирующий (ПИД) регулятор, эффективность применения которого в технологическом процессе определяется быстродействием и точностью его работы. Данные качества напрямую зависят от правильности настройки параметров регуляторов, для синтеза которых необходимо использование современных систем автоматизированного проектирования. В работе рассматривается метод автоматизированной настройки ПИД-регулятора динамической системы высокого порядка с обратной связью на примере системы автоматического регулирования температуры в помещении. В качестве среды разработки модели системы, а также процесса ее анализа и оптимизации используется современная российская среда динамического моделирования технических систем SimInTech, используемая на ряде предприятий атомной, нефтеперерабатывающей и аэрокосмической отраслей. Приведены основные компоненты системы, передаточные функции ее элементов. Дано поэтапное описание процесса создания проекта из типовых блоков и субмоделей программного обеспечения, взаимодействующих через единую базу данных сигналов с применением встроенного языка программирования. Подробно описано и проиллюстрировано использование встроенного блока оптимизации среды визуального моделирования SimInTech для автоматизированного поиска параметров регулятора ПИД-типа. Перечислены выявленные в ходе реализации проекта преимущества и недостатки данного метода настройки.
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Автоматизированная система обнаружения аномалий периодических электрических сигналов
Статья научная
Целью работы является разработка автоматизированной системы обнаружения аномалий периодических электрических сигналов с улучшенными характеристиками скорости и эффективности поиска. Для решения поставленной цели проведен анализ проблемы обнаружения аномалий периодических электрических сигналов, измеренных от электронной аппаратуры, и обоснована ее актуальность. Разработана аппаратно-программная система обнаружения аномалий периодических электрических сигналов, которая позволяет автоматизировать процесс испытаний и повысить эффективность обнаружения неисправностей электронной аппаратуры различного назначения. Улучшение означенных характеристик достигнуто за счет нового метода испытаний, лежащего в основе реализации предложенной системы и защищенного патентом Российской Федерации на изобретение, а также за счет качественной реализации программного и аппаратного обеспечения. При решении поставленных задач применены методы алгебры-логики, математической статистики и объектно-ориентированного программирования. Изложены результаты разработки аппаратуры и программного обеспечения, а также алгоритмов испытаний. Описана программа для электронной вычислительной машины, реализующая управление предложенной аппаратнопрограммной системой.
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Алгоритм быстрого умножения элементов в 2-группах на основе полиномов Жегалкина
Статья научная
Проектирование сети многопроцессорной вычислительной системы или дата-центра представляет собой важную проблему, в рамках которой осуществляется поиск моделей графов, обладающих привлекательными топологическими свойствами и позволяющих применять эффективные алгоритмы маршрутизации. Указанными свойствами, в частности такими, как высокая симметрия, иерархическая структура, рекурсивная конструкция, высокая связность и отказоустойчивость, обладают графы Кэли. Например, такие базовые топологии сети, как «кольцо», «гиперкуб» и «тор», являются графами Кэли. Определение графа Кэли подразумевает, что вершины графа являются элементами некоторой алгебраической группы. Выбор группы и ее порождающих элементов позволяет получить граф, отвечающий необходимым требованиям по диаметру, степени вершин, количеству узлов и т. д. Решению данной задачи посвящено большое количество научных статей и монографий. Для исследования графов Кэли, в первую очередь, необходимо разработать быстрые алгоритмы умножения элементов в данных группах. Такие алгоритмы помогают осуществлять эффективную маршрутизацию на соответствующих графах Кэли. Цель настоящей работы - создать алгоритм быстрого умножения элементов в конечных 2-группах, т. е. в группах периода 2n. В первом разделе статьи дано теоретическое обоснование алгоритма. Показано, что элементы данных групп могут быть представлены в виде битовых строк, а их умножение осуществляется на основе полиномов Жегалкина. Во втором разделе представлен псевдокод алгоритма, на основе которого вычисляются полиномы Жегалкина. На первом этапе алгоритма вычисляется pc-представление группы, на основе которого получают полиномы Холла. На заключительном этапе полиномы Холла преобразуются в полиномы Жегалкина. В третьем разделе продемонстрирован пример получения полиномов Жегалкина для двупорожденой группы периода 4. В заключении рассматриваются перспективы применения алгоритма на реальных вычислительных устройствах. Отмечается, что предложенное представление элементов группы в форме битовых векторов позволяет применять их даже на самых примитивных микроконтроллерах.
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Статья научная
Материалы с различными экзотическими электромагнитными характеристиками широко изучались в последние десятилетия, чтобы удовлетворить растущий интерес в различных областях, включая визуализацию, телекоммуникации, использование энергии и т. д. В качестве особенно многообещающего кандидата электромагнитные метаматериалы проявляют электромагнитные свойства, недоступные природным материалам, в связи с тем, что киральная среда (метаматериал) представляет собой совокупность равномерно распределенных в изотропной диэлектрической среде проводящих зеркально-асимметричных (киральных) элементов. Помимо материала, из которого изготовлен киральный элемент, важнейшую роль играет и его форма. Именно поэтому так важно исследование новых видов киральных элементов, а также определение электродинамических свойств киральных метаматериалов на их основе. В работе рассматривается решение задачи определения коэффициентов отражения и прохождения при падении плоской электромагнитной волны на планарный слой кирального метаматериала на основе многозаходных проводящих элементов типа спирали с учетом структурных параметров метаматериала, который представляет собой матрицу из тонкопроволочных идеально проводящих элементов в виде N взаимно ортогональных спиралей. Для определения параметров кирального метаматериала на основе составных спиральных элементов, рассмотрено построение частной математической модели составного элемента на основе произвольного числа спиральных элементов в пространственной конфигурации, а также метаматериала на основе матрицы таких элементов. Предложен алгоритм вычисления постоянных распространения волн с круговыми поляризациями в указанном метаматериале. Из представленных расчетов можно отметить, что исследуемая метаструктура на одной частоте может выполнять роль частотно-селективного защитного экрана, не прозрачного для излучения вблизи основной резонансной частоты.
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Анализ киберугроз корпоративной сети на основе параллельной обработки данных Netflow
Статья научная
Публичные сервисы различных организаций подвергаются постоянным кибератакам, что повышает риски информационной безопасности. Анализ сетевого трафика является важной задачей для обеспечения безопасного функционирования сетевой инфраструктуры, в том числе корпоративных сетей. В данной работе представлен обзор основных подходов для анализа сетевого трафика, приведены смежные работы, указаны недостатки существующих работ. Одним из методов является анализ данных сетевого трафика с использованием протокола Netflow, который позволяет сохранять данные о трафике на уровне L3 модели OSI. Особенностью исследования является использование длительных периодов наблюдения. При сохранении данных на длительных временных интервалах журналы имеют большой объем, что требует распараллеливания для первичной обработки данных. Авторами разработан кросс-платформенный программный комплекс распределенной обработки журналов сетевой активности, который использовался для анализа сетевой активности корпоративной сети Красноярского научного центра за 2021-2022 гг. Показана схема программного комплекса, описаны его возможности и особенности функционирования. Приведены источники данных для анализа и методика обработки. В работе были сформулированы и формализованы эвристические критерии аномальности сетевого трафика, которые сигнализируют о наличии возможных атак на сеть, также выделены датасеты по сетевой активности различных протоколов прикладного уровня. Для полученных наборов данных были рассчитаны статистические показатели, на основе которых получена информация об аномальной сетевой активности в течение двух лет. В работе проверен предложенный ранее авторами метод сравнения рисков киберугроз для различных временных интервалов, показавший существенное увеличение рисков для 50 % показателей в 2022 г. Сравнение месячных интервалов за различные годы показало аналогичное увеличение риска. Таким образом, метод доказал свою работоспособность и может применяться в других областях, в которых существуют группы критериев независимых показателей. Авторы привели планы по дальнейшему развитию методики анализа сетевой активности.
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