The paper presents a control algorithm for an adaptive hydro-pneumatic spring with smooth changes in the elastic characteristic during the impact of various kinds of dynamic and kinematic disturbances. Analysis of the control object, which allowed to propose a common structure of the automatic control system, was performed. Particular attention was paid to description of control principles inherent to the computing device; the main constraints in the synthesis of the desired elastic properties were also emphasized. Basic options for controlling electro-hydraulic equipment, which can be used in the control system, were described; their brief comparison was conducted. The final part of the article demonstrated working capacity of the developed algorithm by testing it on a mathematical model of a hydro-pneumatic spring. The authors draw a conclusion that the developed control method has several advantages over traditional control methods and could be implemented, using a hardware base available for the domestic industry.

The authors consider extracting combined with swaging and distribution as a method to intensify the processes of sheet metal forming allowing to produce a conical workpiece which has a funnel-shaped opening with a large coefficient of deformation for one technological transfer in one molding tool. During the study of extracting combined with swaging and distribution computer modeling AutoForm software was used. The authors consider influence of friction on the process of forming; they evaluated changes in thickness of the funnel-shaped opening and in deformation forces with different values of friction coefficient. The authors also considered the effect of distribution on force parameters of the combined extracting and final dimensions of the product.

This article justifies the necessity of developing a general mathematical model of cavitation wear of work-pieces, which takes into account design-engineering features and operating modes along with properties of external hydro-dynamic environment and the strain-stress state of a work-piece. Simulation results of the strain-stress state of a work-piece operated in a hydro-dynamic medium and influenced by cavitation were presented in this paper along with pressure values, the equivalent stress and deformation velocity in the work-piece’s materials under consideration. The developed evaluation model for the strain-stress state of a work-piece is one of the basic modules of a general mathematical model of work-piece cavitation wear.

This work justifies the necessity of developing a method of quantitative estimation of nozzle extension deterioration of water jet cutting equipment during continuous operation under given manufacturing modes. The proposed method consists of several major blocks; their function is forming various mathematical models which describe wearing processes. Simulation results of a hydro-abrasive jet in a nozzle extension were considered in this work along with interaction between abrasive particles and channel walls. Influence of the nozzle extension wear on the erosion rate of the processed material was also investigated. 

This paper describes optimization of the power subsystem of an electrohydraulic servo drive with throttling governing. The electrohydraulic servo drive was considered together with an electrohydraulic power amplifier replaced by a proportional link. Variable parameters were selected and objective functions for design alternatives were proposed in order to optimize the electrohydraulic servo drive. An example of two-criterion optimization of the power subsystem was considered in this paper. These criteria were nearness of phase-response characteristic to the axis of abscissae and the mass to power ratio. Multi-criterion modification of genetic algorithm was used to obtain the Pareto front. The described concept is based on generalization of optimization methods for the  electrohydraulic servo drive known from literature references and includes new proposals on the structure of the optimization algorithm.

It was proposed to carry out performance evaluation of active vibration damping in multi-mass dynamic systems of metal structures of excavators and jib cranes when damper’s power body is located between oscillating masses, in comparison with external resistance damping. Results of synthesis of damping effect which provides a specified degree of oscillation decline in metal structures under force excitations and self-oscillations were presented. It was shown that allocation of the active damper’s power body between the working body’s installation unit and metal structures of machines allowed one to improve dynamic properties of the specified machines significantly.

A spatial model of interaction between a wheel vehicle and a road surface was considered in this article. Expressions for kinematic and power factors that determine motion and oscillations of a wheel vehicle, transmission elements and its running gear under spatial loads were obtained. It was shown that specifying wheels displacement in the coordinate system connected with the vehicle’s body allowed to make this mathematical model of motion significantly more precise. This approach provides a possibility to obtain a reliable estimate of exploitation operating modes of aggregates and systems of a wheel vehicle under conditions of passing engineering constructions.

The purpose of this paper is to develop methods of improving design of a truck cab at a dynamic impact on A-pillars; the aim of this design is to increase characteristics of passive safety. According to the results of the calculation the authors estimate maximum movements of primary elements of the design and residual living space; the authors analyse behaviour of the door frames, window frames, pillars, frame girders, other elements of the truck cab, etc. The design is experiencing contact, buckling, crumpling, bending, appearance of plastic hinges. To improve the design, the most sensitive areas and locations of plastic hinges were found. As an indirect assessment of stiffness in the cab as a whole, the authors suggest that, besides the recommended living space, acceleration of the mass center of a dummy should be used; the maximum value of acceleration at a certain time interval should be regulated, too. Basing on a comprehensive analysis of the impact of structural factors on passive safety of a truck cab at an impact on A-pillars, modifications to vehicle interior (increased thickness of the main parts of cab doors, introduction of local pads and foam aluminium racks inside the truck cab), which improved truck passive  safety. Key words: passive safety, truck cab, pillar, pads, foam aluminium, impact load, LS-DYNA.

In this article a sufficient condition for exponential stability of a linear system with delay was proposed; a new estimating method of the degree of damping and magnitude of overregulation was developed on the basis of this condition. The exponential stability condition lies in solvability of an arbitrary non-linear matrix inequality for one matrix and two scalar unknown quantities. Explicit expressions for estimates of the lower bound of the degree of damping and the upper bound of overregulation in terms of solution to this matrix inequality were derived; a method for finding such solutions was also proposed. An example illustrating effectiveness of the proposed approach was considered.

In this paper the author proves that in groups with small cancellation conditions C(3)-T(6) an occurrence problem in a cyclic subgroup is solvable; in other words, for any elements (g,h) of such a group one can determine whether there exists an integer n≠ ±1:gⁿ=h. This result is the latest in a series of theorems on groups with small cancellation conditions C(p)-T(q), proved by the author: on resolvability of a root problem, on resolvability of a problem of conjugated appearance in a cyclic subgroup, on the norm forms of elements in the infinite order and on the characteristic property of elements in the finite order. The results were obtained with the use of the group diagram method. As a direction for further development, it is planned to solve a problem of power conjugation in the specified class of groups.

It is impossible to use the known in the theory of transcendental numbers Siegel's method directly for investigation of arithmetic properties of values of generalized hyper-geometric functions with irrational parameters because these functions do not belong to the class of E-functions. For that reason in such a situation one usually applies different variants of effective construction of linear approximating forms. In this paper we use one of such variants that makes it possible to consider the differentiated with respect to a parameter functions. The capabilities of this method are extended by a special choice of parameters of the functions under consideration.

This article deals with problems of global optimization, model updating and diagnostics of hydro-mechanical systems. It was assumed that criterion functions were continuous, Lipschitzian, multiextremal and not always differentiable. Two novel hybrid algorithms were proposed; these algorithms use the modern stochastic Particle Collision Algorithm based on an analogy with absorption and scattering processes for nuclear particles, for scanning a search space. Local search was implemented with the use of a linearization method with smoothing approximations of criteria for the first algorithm, and a convergent variant of the Nelder-Mead simplex method was used for the second algorithm. Some results on solving model problems on computational diagnostics of the coolant phase constitution in the reactor primary circuit were presented.

The frontier of linear spatial filtration during interference elimination of a spatially-heterogeneous background was considered in this article. It is supposed that the effect of linear filtration depends on parameters of the correlation function of the background and characteristics of an optic-mechanical block. The achievable degree of interference elimination, obtained as a result of analytical statistical estimation, was compared with the values required for a difficult background. The authors estimated the degree of signal suppression from the edges of interfering formations on a “step” model and on a video frame with a real difficult background. The obtained results demonstrated that the class of linear filters does not provide comprehensible indicators of interference elimination during observation of targets on difficult background ensembles.

A problem of fluid oscillations in tanks of space launch vehicles is quite well known and has been investigated extensively during the last decades. This is caused by the fact that the major mass of a liquid-propellant rocket is fluid and its forced motion affects vehicle controllability significantly. In their recent works the authors considered small oscillations in tanks with a propellant intake and with fuel reallocation inside a vehicle. Such problems have arisen due to the purpose of increasing efficiency and output performance of multistage cluster rockets by central stage fueling from side stages of a cluster. The problem of propellant free oscillations in cylindrical and conical tanks was considered, and solutions were presented with boundary conditions on a free surface and the surface of intake that, figuratively speaking, provides resistance to the fluid descent. Eigen-frequencies and Eigen-values of perturbed motion equations with dissipation on boundary surfaces were found. It was shown that slow fluid decent and intake surface boundary conditions may affect both oscillating and damped terms of the solution.

The authors consider influence of distribution of magnetic field induction on distribution of gas discharge parameters in crossed electric and magnetic fields in the passage of a thruster with an anode layer. The authors proposed a flow model of the electron component, where the flow is perpendicular to the magnetic field, with the use of the specific flux value. The authors also obtained a ratio between distribution of plasma potential over the passage with distribution of the specific flux, and a ratio that allows to determine the position of the low-voltage anode boundary layer. An example of calculating plasma potential distribution over the channel of a thruster with an anode layer, and of determining the position of a low-voltage anode boundary layer was given in this article.

It was proposed to carry out performance evaluation of active vibration damping in multi-mass dynamic systems of metal structures of excavators and jib cranes when damper’s power body is located between oscillating masses, in comparison with external resistance damping. Results of synthesis of damping effect which provides a specified degree of oscillation decline in metal structures under force excitations and self-oscillations were presented. It was shown that allocation of the active damper’s power body between the working body’s installation unit and metal structures of machines allowed one to improve dynamic properties of the specified machines significantly.

This article deals with real-world problems of secondary digital processing of radar data in an autonomic survey radar subsystem. Essential aspects and complexities of trajectory processing in such kind of systems were revealed. A review of existent algorithms for locking trajectories as an important stage of secondary processing was presented. An algorithm for locking target trajectories, which takes into account low accuracy of the input data, was developed; this algorithm was considered to be optimal by the maximum likelihood criterion. Mathematical simulation which demonstrates satisfactory performance of the proposed algorithm, including the case of data with an intense noise, was carried out.

In this article the authors propose an investigation method of changing current–voltage characteristic of a resonant tunneling diode influenced by degradation processes in its structure. An investigation of degradation of an AlAs/GaAs resonant tunneling diode structure at the temperature of 300°C was conducted. The findings show that in these conditions change in current–voltage characteristic of the resonant tunneling diode is mainly due to degradation of ohmic contacts. An analytic dependence of the resonant tunneling diode AuGeNi ohmic contact resistance on time and temperature was determined.

Thermal power loading of a thermoelectric module (TM) in operation was investigated; the weakest elements were revealed. Analysis of thermal deformations arising in the branches of TM was carried out. Influence of various deformation types on the stress-strain state of the TM’s branches was studied. A mathematical model for calculating stresses in the branches of TM was developed. Calculation results obtained with the use of the proposed model were presented. Influence of geometric characteristics of the TM’s branches and manufacturing tolerance on stresses in the branches was also investigated. Recommendations were given on the design of TM on the basis of the obtained results.

The paper deals with creating a mathematical model of motion of abrasive grains in the abrasive extrusion processing (AEP). This will extend capabilities of this technology. The essence of the AEP is in puncturing (extrusion) of an abrasive paste along the processed surfaces (in most cases through holes) and material removal by abrasive particles contained in the paste which consists of abrasive grains and a binder in a viscous-elastic liquid. Use of existing models cannot explain the essence of the grain’s motion and its impact on the processed surface material. The author substantiates the need for introduction of elastic characteristics of the bonding liquid into the model’s main equation, along with the concentration index of the abrasive grains.

The authors proposed and justified a new approach for predicting conditions of an aerospace survey in order to improve its effectiveness. This approach is based on the fact that information on optical characteristics of the atmosphere, the earth's surface brightness, spectral reflectance, as well as exposure parameters of shooting performed in the form of layers of the geographic information system, could be used for solving problems associated with planning an aerospace survey. The basic idea of this work lies in forming a high dynamic layer of the continuous phenomena of geo-information system; this high dynamics is caused by high dynamics of change in meteorological conditions.

This article presents analysis of a typical process related to implementation of a release cycle of electronic periodicals in a publishing house of a higher educational establishment. A set of main components that represent various parts of the publisher’s organizing structure and affect the operating behavior was determined. A process of maintaining queries from users by editors, reviewers, and bibliographers was considered. As a result of the conducted investigations, it was shown that the law of inflow of publication queries in an electronic periodical was the simplest one. Parameters of that simplest inflow of users’ queries were also determined. A formalized scheme represented in the form of a closed-loop querying system was proposed for description of a typical process of the release cycle of electronic periodicals.

A modeling problem of information risks in computer-aided systems was considered in this paper. It was shown that a usage of fuzzy models is a promising approach to solving this problem because their development requires far less information about the system. Analysis of various types of fuzzy models was carried out; their main features were emphasized. The Mamdani model was recognized as the most suitable for estimating information risks. Combination of fuzzy and neural network modeling was proposed; that means the creation of neuro-fuzzy networks by transforming the Mamdani fuzzy model to a self-learning neural network, which operates on the basis of fuzzy logical apparatus and fuzzy sets. An example of a neuro-fuzzy network for an assessment of information risks was presented.

This work is a part of investigation devoted to the development of design methods for ontological knowledge bases, oriented at the decision support in the enterprise information systems. An approach to finding solutions in knowledge bases using document’s metadata was considered. Document’s metadata as well as search queries were represented as the frames of design and search patterns respectively. Slots of those patterns corresponded to the concepts’ roles in the utilized ontology. Specified roles divided concepts of ontology, a document and a query into clusters. Semantic networks for those clusters were defined in such a way that search queries of a document were represented as a set of semantic networks, corresponding to the slots of design and search patterns. The relevancy of a document was estimated by a set of metrics which formalized the nearness of semantic networks. A problem formulation of multi-criteria estimation of the relevancy of documents in the enterprise ontological knowledge base and an adaptive solution method were presented in this paper.

This paper deals with the problem of multi-criterion optimization. It was assumed that the Pareto set is a solution to this problem. A promising approach to solving this problem is the adaptive weighted sum (AWS) method. Just like the classic weighted sum method based on the additive convolution of partial optimality criteria, the adaptive method also is based on the  convolution. But the AWS method also proposes adaptation of weighting coefficients during iterations on the basis of the current location of the search subarea. This method works with meta-models of criterion functions in order to reduce computational costs. Results of our investigations showed that the AWS method provides a high quality Pareto-approximation in case of a convex, although, maybe, unconnected Pareto frontier. For problems with a concave Pareto frontier this method doesn’t always provide sufficient quality of solution or it does but this takes too much time. In some cases the AWS method could provide an unacceptable solution caused by a special method of constraint satisfaction. The purpose of this work is to overcome specified disadvantages of the AWS method. A problem formulation for multi-criterion optimization was presented along with basic approaches to its solving. Several modifications of the ASW method proposed by the authors were considered. A brief description of the developed software implementing the method and its modifications were presented. Performance study of this software was carried out.

This paper presents an analysis of existent nearest neighbor algorithms, and a description of a new nearest neighbor algorithm. A parallel version of the proposed algorithm was developed; its implementation using parallel computations was also described. Experimental results on estimating efficiency of the developed program implementation were provided. The proposed implementation is a C++ library. Possible application domains are geo-systems, liquid motion simulation and other areas where it is required to determine the nearest neighbors in a large bulk of data.

A new method was proposed to solve terminal control problems for multidimensional affine systems. The system under consideration is supposed to be equivalent to a regular system of a quasi-canonical form. A necessary and sufficient condition for existence of a solution of terminal control problems for transformed systems was formulated. A sufficient condition for solvability of terminal control problems was proved for quasi-canonical systems with nonlinear subsystem dimension not exceeding control dimension. An algorithm was designed to construct a solution of terminal control problems for this class of systems. A numerical example was presented to illustrate the proposed algorithm.

This paper deals with solving a tracking problem for a scheduled change in the angle of attack initiated by a target direction system with regard to longitudinal dynamics of an air-to-air missile. Control system design was performed with the use of an integrator back-stepping method. The author considers a model of longitudinal dynamics which takes into account dynamics of rocket control organs along with dependence of aero-dynamical coefficients on the modulus of the angle of attack. According to the results of the numerical simulation it is possible to draw a conclusion about working capacity of the control algorithm based on the investigated simplified model of longitudinal dynamics. Control of technical systems is a possible application domain.

In this paper the authors formulated a problem of optimising the composite micro-structure, which is a problem of minimisation of the composite density under given restrictions on the components of effective elasticity and heat-conduction tensors, and effective limits of the composite strength. The authors proposed a method for solving an optimal design problem of a composite material reinforced with micro-spheres and designed for thermal shielding. The method of asymptotical averaging (homogenisation method) was used for calculating effective composite characteristics such as elastic and heat-conduction modulus tensors and strength limits; the finite element method was used for solving local 3D heat conduction and elasticity theory problems on the composite’s periodicity cells. The finite element method was implemented with the use of GCD software developed at “FN-11” department of Bauman MSTU. The Hooke Jeeves algorithm was used for solving optimisation problems. Numerical implementation of the proposed method of micro-structure optimisation was developed by the example of a composite based on glass micro-spheres.

This paper deals with a co-evolutionary algorithm of global optimisation, Co-PSO, based on particle swarm optimisation. Implementation of this algorithm developed in MATLAB was described in this work. This software is oriented to a parallel operation of the given number of PSO algorithms at the logical level. These algorithms use various neighbourhood topologies of particles and/or various values of their free parameters. Results of a comprehensive numerical experiment on performance study of Co-PSO and its implementation were also presented. The experiment was based on Rosenbrock, Himmelblau and Rastrigin benchmark functions. Experimental results show superiority of the Co-PSO algorithm over the canonical PSO. A three-criterion problem of optimal control for a spacecraft during its reentry was solved with the use of Co-PSO. Methods of additive scalar convolution and reduction of the optimal control problem to a nonlinear programming problem were used in this work.

Using a multi-scale homogenization method, a three-level model was developed for ceramic composite materials based on the reaction-bonded SiC. Numerical simulation was performed with the use of the finite-element method for solving a set of local problems over the periodicity cells of three structural levels. Tensor fields of stress concentration were computed in matrices and fillers. A new strength criterion of a matrix and fillers at multi-axis stress state was applied; this criterion takes into account a significant difference (more than ten times) between strength features of ceramics under tension and compression. A model that takes into account a scale effect of the strength of ceramic composites was proposed. Numerical investigation of sequential microstructural destruction of ceramic composites up to the final fracture was conducted. Computations demonstrated that at the presence of a polydisperse structure of ceramics, a change in concentrations of large-scale fractions plays less considerable role than in the case of small particles fraction.

A mathematical multi-level model for calculating thermo-elastic properties of textile composites with alumino-chromic phosphate matrices under high temperatures was developed. This model takes into account physical-chemical transformations occurring in an alumino-chromic phosphate binder and glass fibers under a high temperature. Comparison of calculation results with experimental data was carried out; it was shown that the developed model allowed to predict a complicated nonlinear character of changes in elastic properties of composites under heating up to 1600 К. The developed model could be used for prediction of elastic properties of composites with alumino-chromic phosphate matrices under complicated heating modes.

The self-consistency method was used to estimate the components of a thermal conductivity tensor of unidirectional fiber composite, which is transversally isotropic with respect to an axis arranged parallel to the fibers. In this method it is possible to estimate effective values of parameters for the composite as a whole by averaging the perturbed distributions of the parameters over the elements of the composite structure and equating averaged results to zero. A perturbed temperature field and heat flux density distribution over the fibers and composite matrix were calculated on the basis of the developed mathematical models of heat interaction between these elements of the structure and a transversely isotropic homogeneous material which has required coefficients of thermal conductivity. For validation of the final calculated dependences, bilateral estimates based on dual variation formulation of the stationary problem of heat conduction in an inhomogeneous solid body were used. The calculated dependencies can be used for forecasting effective thermal conductivity of unidirectional fiber composites.

The Runge–Kutta discontinuous Galerkin method for an ideal MHD system of equations on the unstructured mesh for axisymmetric cases was considered. An algorithm of divergence-free magnetic field reconstruction in cylindrical coordinates was given. This algorithm allows one to obtain physically appropriate computation results with a high order of accuracy. A mathematical simulation of magneto-rotational instability in the shell of an accreting protostar was carried out. The obtained results were illustrated and discussed. These results showed that the magneto-rotational instability leads to formation of large-scale structures and causes transfer of angular momentum to the circumference of a plasma cloud.

Dynamics of an ideal incompressible fluid filling a cylindrical vessel divided by an elastic membrane with an allowance for surface tension forces was investigated in this work. Boundary conditions for surface tension at the wetting angle of 90 degrees were formulated; normal oscillations were determined. The Bubnov-Galerkin method was used to obtain an approximate frequency equation in an axially symmetric case (plane problem). Dependence of the natural frequency of oscillations on the Bond number which characterises the strength of gravity was analysed. A critical value of the natural oscillation frequency was also determined.

In this paper the authors consider how the impact of work chamber atmosphere at a nuclear industry enterprise where uranium hexafluoride is used affects the human body. History of studies in this field was briefly described, and the place of current investigations in these studies was indicated. This work deals with a model for calculating deposition of fluorine in the human body. In this paper quantitative relationship between concentration of uranium hexafluoride molecules in the air of a factory shop and the mass of fluorine deposited in the human body was obtained on the basis of mathematical simulation methods. A technique for determining the specified relationship was presented. Calculations were performed within the framework of a model which describes pollution of a work chamber atmosphere and penetration of toxic substances into the human body. This paper presents results for two injection methods — percutaneous (through the skin) and inhalation (through the respiratory system), and for two modes of air pollution — emergency release and technological outputs under conditions of daily industrial activity. The calculated injections were compared with experimental data; such injections lead to irreversible changes in the human body. Conclusions on possible medical care for victims were drawn.