SCIENCE & EDUCATION

The authors propose a method of increasing accuracy control of computing systems in sonar complexes. This method allows to increase methodical validity of a control system by using simulation modeling of signals from sonar complex devices in real time. This article presents a brief analysis of the structure and main working principles of the monitored item; the main potential problems are emphasized along with the causes of their occurrence; application area of the proposed method was determined. This method could be applied to technical control of products in industry and to debugging of on-board software of sonar complexes and development of new promising algorithms of sonar signal processing.

This article considers stochastic control systems with impulses that are generated by hyper-Erlangian flows of events and lead to discontinuities of system trajectories. The authors solve the problem of finding a probability density function for the system state. The solution is based on usage of the spectral form of mathematical description. The purpose of this paper is to develop a spectral method for analysis of this kind of systems, based on function expansion by a series of orthonormal functions. This approach simplifies the process of solving analysis problems, making it convenient for use of modern high-performance computers.

The problem of information security in automated systems is considered in this article. Various approaches to restriction of access to information resources were analyzed. An authorization algorithm was developed; the algorithm uses images which a human will be able to recognize but which an intellectual "program robot" will not be able to recognize. Basic types of distortions of reference images were chosen. It is proposed to apply a dynamic neural network as a peculiar filter allowing one to reject images with high probability of recognition. Hopfield’s recurrent network was used in the implementation of the algorithm.

Change of the independent variable (time-scaling) gives an additional degree of freedom for equivalence conversions of dynamical systems. Affine system transformation to the canonical form is a standard technique in the design of nonlinear control systems. In this paper transformations of a stationary affine system to the canonical form, using time-scaling, were investigated. Integratable and non-integratable changes of the independent variable were considered. It was shown, that the affine system can't be transformed to the canonical form using integratable time-scaling. Conditions of the possibility of transformation to the regular canonical form using non-integratable time scaling were obtained for single-input affine systems of the third order.

This is the second paper in the series of four works dedicated to design of parallel mechanisms for orientation of the space observatory “Millimetron”. In this article the authors stated a problem of “Millimetron” observatory's antenna orientation with the use of a parallel hexapod-based multi-sectional manipulator. The manipulator was designed in Solid Works software package. The Manipulator's 3D-model created in NX5 with the use of “Kinematic Simulation of Mechanisms” software package is introduced in this work. Software for solving direct and inverse kinematic problems was designed. A model of the guided five-section manipulator developed in MatLab Simulink software package is also described.

Influence of harmonic noise on phase-lock loop (PLL) leads to distortion of received information and a loss of PLL stability. This article analyzes effects of harmonic interference on synchronization processes in the second order PLL system. Analysis of signal grabbing and interference capturing cases was carried out in this work; projections of a phase path onto planes, which illustrate the specified modes, were also obtained. By analyzing phase planes, equations of capturing signal and interference were obtained. Dependence diagrams of the signal-to-noise ratio and frequency error are presented along with a bifurcation diagram. Application compares critical values ​​of the PLL parameters obtained by different methods.

This article deals with a review of modern interactive methods for solving the multi-objective optimization problem. The most advanced class of interactive methods is represented by techniques based on estimations offered by the system of multi-objective optimization of alternatives. Depending on the form of the decision maker’s estimates one can separate two classes of interactive methods: methods based on estimations of DM’s preference function and methods based on the pairwise comparison of solutions. Precisely these two classes of interactive methods are described in more detail in this article; directions for their further development are proposed.

 In this article the authors consider experimental evaluation of reducing computational complexity of algorithms of ultra-graph operations. According to the results of theoretical analysis of the algorithms of ultra-graph operations, procedures, which introduce the greatest contribution to their computational complexity, were defined; ways of its reducing were selected. With the help of special software contribution of optimizing transformations to reducing computational complexity of vertex addition was estimated. Experimental results showed high efficiency of the conversion process - total reduction of computational complexity of the algorithm was up to 87%.

The authors research the method of algebraic attack on stream ciphers based on solution of algebraic equations. The method is applied to a stream cipher constructed according to the disposable pad scheme. The authors consider types of key stream generators needed to construct stream ciphers. The key stream is a pseudo-random bit sequence which is combined with the original message to get the ciphertext. The algebraic method of finding the key of the key stream is described in the article. A program that generates a key stream and a system of equations to analyze the stream cipher was developed. The authors found maximum parameters of the stream cipher, the analysis of which can be carried out by software in several first elements of the key stream, its output function and changes of memory state.

The author describes an algorithm of a multi-variant evolutionary synthesis which combines advantages of genetic algorithms and genetic programming, based on a sequential operator structure of chromosome and templates (patterns, skeletons) of algorithms and a given set of pairs of input - output data. Influence of many variants of estimating chromosomes and the degree of the template’s specialization on search algorithm efficiency in the evolutionary synthesis was investigated. The author obtained estimates of the algorithm complexity and compared them with ones for the standard method of the evolutionary synthesis; this comparison showed a significant (by several times) decrease in search time by using the multi-variant evolutionary synthesis algorithm.

In this article the process of two-dimensional autoregression of (1,1) order is considered. Distribution of the renovating field of the autoregressive model is assumed to be unknown. The author found the asymptotically locally most powerful tests for verifying the hypotheses about coefficients of the autoregressive field, based on the approximate rank index marks. Estimation of the autoregressive model parameters based on the ranks of observation residuals was build. Consistency and asymptotic normality of these estimations was proved. The conclusion was drawn on the advantage of the constructed estimation over the least squares estimation if the renovating field has normal logistic and double exponential distribution, while rank index marks correspond to Gaussian density.

The authors propose an algorithm for hashing data, basing on the increase in entropy during simulation of physical processes. The two-dimensional Ising model was selected as a system. The Ising model was studied with the use of the Metropolis algorithm. A computer experiment was carried out in order to detect collisions and determine the avalanche effect. The model’s preferred parameters such as temperature and size were identified experimentally. It was shown that the avalanche effect becomes large enough when the temperature is higher than the critical one by 28%. The dimension of the system must be chosen depending on the size of the output digest. It was also shown that the two-dimensional Ising model has sufficient mixing properties for cryptographic hash functions. The authors conducted a comparison with common algorithms MD5 and SHA-1. The developed hash algorithm is scalable, unlike traditional hash algorithms.

 The article deals with a three-objective optimization of slotted filter geometry produced by an innovative method of deforming cutting. This method was developed by Professor N.N. Zoubkov from BMSTU. The multiobjective problem is solved by using the interactive PREF method proposed by the authors. This method is based on the assumption that a decision maker (DM) is able to provide, in some form, preference information related to various solutions proposed by multiobjective optimization software. The DM’s utility function is approximated by a neural network. This work presents a three-objective optimization problem statement of filter design, a short description of an interactive method and its software implementation along with results of computational experiments. 

The aim of the work is to investigate kinematics of a single-section parallel “dodekapod” manipulator. The “dodekapod” is an extension of a hexapod and has 12 degrees of freedom. In the article, direct and inverse kinematic problems of the “dodekapod” were solved with the use of the Yaw, Pitch and Roll transformation method. Using matrix of transformation, one can express position and orientation of any plane in two ways: by a directed vector or by transformation parameters. The particle swarm optimization method (PSO) was applied to solving a direct kinematic problem. Results of this work subsequently are used to find the workspace of the “dodekapod”, and also to solve the problem of its dynamics.

This article describes methods of decision-making theory which allow the decision maker to analyze various promising ways of upgrading a LAN server in detail and chose the best one; these ways are selected by a working group of experts. Recommendations are proposed on use of given methods in practice. A wide range of server’s operating parameters is taken into account along with nameplate engineering data. Practical guidelines on numerical composition of initial promising variants of upgrading a LAN server are also given. An example that demonstrates potentials of the proposed method is provided in the article.

In this paper the author introduces a family of cryptographic hash functions based on using generalized cellular automata. The structure of the proposed functions is a dendrogram which includes a one-way pseudorandom function built with the use of a generalized cellular automaton whose graph is a Ramanujan graph. The local link function of the cellular automata is a balanced function with large nonlinearity and some additional properties. The family of proposed hash functions may find practical application in a number of information security tasks, including authentication, integrity, digital signature, etc.

This paper is an introductory start of a series of four papers dedicated to design of parallel mechanisms for orientation of the space observatory «Millimetron». General description of the «Millimetron» project is provided in this paper. Variations of the space observatory design concepts are considered. The whole series of papers is briefly described. The «Millimetron» project is aimed at creation of a space observatory with a 10-meter cryogenic radar telescope which is capable of working within the waveband from 20 mm to 20 um. The «Millimetron» observatory is designed for conducting investigations of various types of highly sensitive objects (single telescope mode) and record high angular resolution (ground-space interferometer mode) within the infrared and millimeter ranges of wave length. Very high sensitivity of a space telescope is achieved by means of cryogenic cooling of an antenna reflector, thermal shields and receiving equipment with liquid helium.

Many modern methods of synthesis of controllers haven’t become widely applied. It is explained by a variety of reasons, among which one can list lack of simple and clear communication between the minimized functional and quality indicators put into practice, and also unreasonable complexity of the synthesized controller. At the same time in industry simple controllers of low order are in demand. In this article the problem of synthesis of minimal order controllers is considered. These controllers provide the given quality of a linear continuous system at uncertainty of object parameters. Synthesis is carried out with the use of quality indicators which are very simply expressed through coefficients of a characteristic polynomial.

In the present article authors analyze a topical problem of automated formation of control and monitoring materials the contents of which would most completely meet the requirements of the theory of pedagogical monitoring. Key shortcomings of existent widely applied methods of automated test formation are given. The authors introduce a hypothesis of necessity for recording results of semantic-logical analysis of training materials during formation of control and monitoring materials. They present a model of functional dependences of mutual importance of educational elements and scales of groups of control tasks according to their difficulties. On the basis of pilot studies of the developed method, they draw a conclusion on its consistency.

A method of improving computer systems for simulating a real time hydro-acoustic situation was developed. This method reduces the cost of hardware and laboriousness of software development of the modeling system while maintaining adequacy requirements for the mathematical model. The article gives a brief analysis of the acoustic systems structure. Relevance of the problem, scope, limitations and efficiency evaluation of the method were defined. Practical application of the method is possible in design of monitoring and diagnosing computer sonar systems, software development and tests of sonar guidance algorithms.