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Refinement of the aging integral formula is proposed. A computer model of insulation wearing out is developed using refined formula. Computer simulation of power transformer insulation wearing out over the next ten years of life is carried out. References 4, tables 4, figures 3. [ABSTRACT FROM AUTHOR]

The paper considers a method for justifying the choice of a corrosion-resistant material for the manufacture of a blowout preventer body based on computer simulation of an elastic-plastic task in the ANSYS Mechanical APDL software. To describe the material properties, a multilinear deformation model is used, the reference points of which are calculated as a result of working out the macro developed by the authors based on two models: RambergOsgood and the “method of sequential corrections” proposed by TSAGI specialists. The paper presents the results of computer simulation on the loading of the PShKM-ASMT-114x21 preventer body by working and double starting pressure for four variants of body materials. The calculations confirmed the high safety factor of the body for the currently used 40X steel showed sufficient working capacity of corrosion-resistant steels 20X13 and 30XMA. However, a computer experiment detected very extensive zones and the level of plastic strains as a result of loading the body made of 12X18H10T steel with double starting pressure. The obtained results indicate that the investigated preventer can be manufactured in corrosionresistant versions K1 and K2, but for the execution of K3 it is necessary to develop a fundamentally different geometry of the body.

This paper is devoted to the studies of the opportunities for the intensification of the particle diffusion in the periodic structures, for example, the crystals that are exposed to the action of the time-periodic fields of a different nature. These can be acoustic or electromagnetic fields. The trivial one-dimensional model of the motion of the particles in the potential lattice field under the thermal equilibrium has been used. The paper studies the interaction of rectangular fields with the frequencies less than 0.01 ω0, where ω0 is the frequency of natural small vibrations of the particles in the systems with the low dissipation. The selected friction coefficient in dimensionless units is equal to γ'=0.03. The amplitude dependence of the intensification of the diffusion D under the action of the fields of a different frequency has been studied. It was shown that the diffusion coefficient can be increased by several orders of magnitude by applying the field of an appropriate amplitude and frequency. A maximum diffusion intensification is attained at ω→0. A maximum attained value of the diffusion coefficient at the periodic force corresponds to the case of the action of the constant force. However, at low frequencies a maximum intensification is only possible in the narrow range of field amplitudes F'oc γ'. A further increase in the field amplitude results in a decrease of the diffusion coefficient and it attains the value of the coefficient of the particle diffusion in the viscous medium Dvis=k'T'/γ', where k' is the Boltzmann coefficient and T' is the temperature. An increase in the frequency of the external force results in the extension of the range of forces at which D>Dvis, however the value of the diffusion intensification is decreased. It was shown that the exceed of a certain threshold value of the amplitude of the external field results in the gain of the diffusion coefficient at least by the value of η=(k'T'eε/k'T')/(γ"D0, where ε is the value of the energy barrier during the passage of the particle from one cell of the one-dimensional lattice to another. The obtained data open prospects for the development of new technologies to exercise control over diffusion processes. It is of great importance for the production of nanomaterials with the specified structure, creation of the surface nanostructures, etc.

General description of the research topic. A technique and an algorithm for calculating the thermal field of electromagnets operating in complex forced systems proposed by authors are considered. The widespread use of such devices in electromechanical switching devices allows not only to increase their speed but also significantly reduce the size, mass and energy losses, which indicates the relevance of this topic. The mathematical model of heating the windings of forced electromagnets proposed by the authors is a system of 1D differential equations of stationary heat transfer in a cylindrical coordinate system, supplemented by equations of electrical and magnetic circuits. This model allows to take into account the ripple of the currents in the windings and the losses in the magnetic core due to these ripples, contains certain signs of scientific novelty and represents the goal of the paper. The algorithm developed by the authors for calculating the thermal field of electromagnets operating in forced control systems is a complex iterative cycle. Its implementation is greatly simplified by using the Maple computing environment which allows to realize complicated and cumbersome mathematical transformations, automates the process of computations, and obtain results of numerical simulation in a convenient tabular and/or graphic form, which indicates the practical significance of this works. The results of comparison of computation results with experimental data presented in the paper indicate the adequacy of the model and algorithm proposed.

Ultrasound examination of material properties is a precision method for determining their elastic and strength properties in connection with the small wavelength formed in the material after impact of a laser beam. In this paper, the wave processes arising during these measurements are considered in detail. It is shown that full-wave numerical modeling allows us to study in detail the types of waves, topological characteristics of their profile, speed of arrival of waves at various points, identification the types of waves whose measurements are most optimal for examining a sample made of a specific material of a particular shape, and to develop measurement procedures. To carry out full-wave modeling, a grid-characteristic method on structured grids was used in this work and a hyperbolic system of equations that describes the propagation of elastic waves in the material of the thin plate under consideration on a specific example of a ratio of thickness to width of 1:10 was solved. To simulate an elastic front that arose in the plate due to a laser beam, a model of the corresponding initial conditions was proposed. A comparison of the wave effects that arise during its use in the case of a point source and with the data of physical experiments on the propagation of laser ultrasound in metal plates was made. A study was made on the basis of which the characteristic topological features of the wave processes under consideration were identified and revealed. The main types of elastic waves arising due to a laser beam are investigated, the possibility of their use for studying the properties of materials is analyzed. A method based on the analysis of multiple waves is proposed. The proposed method for studying the properties of a plate with the help of multiple waves on synthetic data was tested, and it showed good results. It should be noted that most of the studies of multiple waves are aimed at developing methods for their suppression. Multiple waves are not used to process the results of ultrasound studies due to the complexity of their detection in the recorded data of a physical experiment. Due to the use of full wave modeling and analysis of spatial dynamic wave processes, multiple waves are considered in detail in this work and it is proposed to divide materials into three classes, which allows using multiple waves to obtain information about the material of the plate. The main results of the work are the developed problem statements for the numerical simulation of the study of plates of a finite thickness by laser ultrasound; the revealed features of the wave phenomena arising in plates of a finite thickness; the developed method for studying the properties of the plate on the basis of multiple waves; the developed classification of materials. The results of the studies presented in this paper may be of interest not only for developments in the field of ultrasonic non-destructive testing, but also in the field of seismic exploration of the earth's interior, since the proposed approach can be extended to more complex cases of heterogeneous media and applied in geophysics.

The relevance of the research is caused by discrepancies in design of cathodic protection of pipelines. Electric current, flowing from anodic protection to the ground, spreads there and then enters the protected pipeline polarizing its cathode. Certain assumptions are taken to describe the patterns of change imposed by the potential and strength of the polarizing current along the length of the pipeline at a cathodic protection. There are significant differences between design and actual parameters of protection in settlements of cathodic protection of pipelines. The main aim of the research is to propose an algorithm for solving a boundary value problem for the potential of the electric field of cathodic protection of an underground pipeline by a vertical depth anode based on the method of fictitious sources. Objects: gas and oil pipelines, for which protection against electrochemical corrosion is a necessary condition for ensuring an optimum period of their operation. Methods. Based on the method of fictitious sources the authors have proposed the algorithm for solving the boundary-value problem for capacity of the electric field of cathodic protection of underground pipeline vertical deep anode. Application of the method is justified by the principle of electrostatic analogy for spatial task of electric field distribution. Results. To apply the established relation to this problem in half, the method of mirror reflections is used additionally in the algorithm that allows transferring the task from half to space. The C++ computing code is developed for numerical calculations of electric fields in the systems of cathodic protection of pipelines via deep anodes subject to the restrictions on the electric potential of the protected structure and the density of current, flowing from the anode. The computer model allows conducting a set of numerical experiments for selection of geometric and electrochemical parameters of designed deep anode, to improve the reliability of cathodic protection for underground structures and increase the duration of their service life. The paper introduces the graphs illustrating the features of current density distributions along the depth of anode and the protective capacity of the pipeline, with changes in the external environment for a certain period of operation. It was shown that at decrease in insulation resistance the increase in cathodic station current is required for maintaining the necessary protective pipeline capacity. Current density at the «anode–ground» boundary increases that leads in its turn to more intensive anode dissolution. The paper introduces the examples of numerical results obtained based on real data conditions. The analysis of the results confirms the effectiveness, stability and versatility of the algorithm developed.

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In the last decades, the development of methods for increasing the efficiency of hydrocarbon extraction in fields with unconventional reserves containing large amounts of gas condensate is of great importance. This makes important the development of methods of mathematical modeling that realistically describe physical processes in a gas-condensate mixture in a porous medium. In the paper, a mathematical model which describes the dynamics of the pressure, velocity and concentration of the components of a two-component two-phase mixture entering a laboratory model of plast filled with a porous substance with known physicochemical properties is considered. The mathematical model is based on a system of nonlinear spatially one-dimensional partial differential equations with the corresponding initial and boundary conditions. Laboratory experiments show that during a finite time the system stabilizes, what gives a basis to proceed to the stationary formulation of the problem. The numerical solution of the formulated system of ordinary differential equations is realized in the Maple environment on the basis of the Runge-Kutta procedure. It is shown that the physical parameters of the gascondensate mixture, which characterize the modeled system in the stabilization regime, obtained on this basis, are in good agreement with the available experimental data. This confirms the correctness of the chosen approach and the validity of its further application and development for computer modeling of physical processes in gas-condensate mixtures in a porous medium. The paper presents a mathematical formulation of the system of partial differential equations and of respective system stationary equations, describes the numerical approach, and discusses the numerical results obtained in comparison with experimental data.

The paper focuses on the problem of increasing the accuracy of radar measurements of the elevation angle of the low-altitude targets over the sea. The Matrix Pencil method, as one of the means to resolve this problem, is studied in the paper. This method refers to the methods of high spectral resolution, but in a number of publications, the possibility of its use for measuring the angles of arrival of radio waves is also considered. However, the extent of its suitability for solving the problem needs to be studied taking into account the specific conditions under which the measurement of the elevation angles of low-altitude targets is performed. The research was carried out by computer simulation. It covered the sea states with the conditions of both specular and strong diffuse reflection satisfied. One of the main goals of this work was to determine ultimate measurement accuracy achieved by the method when only the diffuse reflection from the sea is considered as a disturbance (a specular signal along with a direct signal from the target are considered as a measured signal). It was established that by this indicator the Matrix Pencil method does not concede to the well-known MUSIC method, but even exceeds it, especially for strong diffuse reflection (improvement reaches 20%). Another impor-tant task was to investigate the influence of the a priori parameters of the method on the measurement errors: the number of measured signals, the values of the so-called pencil-parameter and the number of spatial samples of the signal at the given antenna aperture. As a result, recommen-dations on the selection of these parameters have been developed, which make it possible to minimize the errors in the measurement of the elevation angles. This research expands the understanding of ways to increase the accuracy of mea-suring the angles of low-altitude targets over an agitated sea.

The paper describes equations of circular symmetrical sandwich plates bending for plates with isotropic outer layers and nonlinear elastic filler. Two computer models of circular sandwich plates are proposed: 1) analytical model on the basis of Maple CAS, 2) threedimensional FEM-model. We compare results of analytical model with results of numerical simulation using two problems: 1) the problem of axisymmetric transverse bending of a sandwich plate, 2) the problem of axisymmetric transverse bending of a single-layer plate with linear and nonlinear formulation. The first section of the article describes basic differential equations and analytical model constructing method. FEM-model is described in the second section. Numerical results of computer simulation are showed in the last section of the article. [ABSTRACT FROM AUTHOR]

In the search for new magnetically ordered phases of materials, solid-state synthesis technologies in reaction crucibles are used. The final result of the synthesis process in reaction crucibles is conditioned, in particular, by technological factors, the mode of current flow and its density, the achieved temperature in the reaction zone, exposure time, geometrical parameters of the crucible and the reaction zone, etc. The paper presents the results of influence investigation of the reaction volume filling degree with tin melt on the processes of heat and mass transfer during its electrothermal treatment. A model describing diffusion processes in the reaction zone during the synthesis of iron and tin intermetallides under electrothermal treatment has been proposed. The diffusion process in the reaction crucibles of the iron-tin system was investigated by the finite element method in the Comsol Multiphysics software environment. It is shown that the decrease in the degree of filling of the reaction crucible with synthesis components leads to a change in the distribution of current density and a decrease in the temperature in the reaction zone, which affects the mass transfer processes. The results of the work can be used in the analysis of experimental data on the production of intermetallides by reaction synthesis and determination of the necessary technological parameters for the synthesis of new materials.

This paper aims to interpret the transformations of the "guitar hero", from the icon of popular culture to models of nostalgic selfdesign, meaning transformations from generally recognizable figure in the context of popular culture to mimetic patterns based in medium of contemporary technologies. The phrase "guitar hero", in its basic meaning represents a specific phenomenon in popular culture and popular music of the second half of the twentieth century. Guitar hero is a performer with skills and appearance that transcends and transforms common patterns of guitar performances, thus creating a new and distinctive form of musical and performative statement. Seen in this way, a guitar hero is close to heroic models of antique and romanticism. On the other hand, contemporary products of cultural industries and the entertainment industry to some extent changed this basic meaning of the phrase "guitar hero". Creation and popularization of video games like Guitar Hero or Rock Band, as well as the availability of high quality replicas of instruments of "original" guitar heroes, carried the meaning of this phrase more explicit in the field of consumerism, fetishism, and virtualization. Guitar hero in its basic meaning undoubtedly belongs to the history of the twentieth century popular culture. However, his legacy is still very much present. Specific heritage of a guitar hero in contemporary popular culture lies primarily in the dissemination of the original model through the mechanisms of consumer society, and then in the mimetic patterns based in media of contemporary technology. Thanks to these characteristics, the phenomenon of guitar hero was transformed from icon of popular culture to nostalgic self-design over the original model. Whether it is a replica of instruments of guitar hero or empathy in virtual reality of video games as Guitar Hero or Rock Band, guitar hero heritage confirms its place in modern popular culture, despite the fact that the "sundown" of rock-guitar culture occurred in the last decades of the twentieth century. However, this transformation from icon of popular culture to model of nostalgic self-design is not without significance for understanding "heroic" component in the phenomenon of guitar hero. Described transformations of guitar hero put this phenomenon even closer to the ancient heroic model - its heroic character was confirmed after its death.o [ABSTRACT FROM AUTHOR]

This paper establishes the system for termining the production of wooden chairs which is the consisting part of the system for production planning. It particularly discusses the termination of the production according to the structural components of the product in thermic units. It defines the simulation programme for the solution of the problem, which is projected in the way that it provides a continuous realization of the logistic chain from the moment of the purchase of repromaterial, through the realization of the working errand in the workshop, to the delivery of the product to the buyer. The simulation experiment starts with the assumption that the necessary repromaterial is opportunely accessible in the entrance storehouse. The programme, which is managed by the automatically calculated priorities of the working errands, completely describes what happens in the workshop. [ABSTRACT FROM AUTHOR]

Background and Objectives: Metasurfaces are coatings consisting of elementary resonators that reemit incident UHF electromagnetic waves. By varying the parameters and arrangement of these resonators, it is possible to tune the electrical properties of the metasurface as a whole. This produces a number of practically important characteristics that are difficult to achieve with conventional attenuation coatings, and therefore prospective in the tasks of shielding of electronic devices and attenuation of the reflected signal. As there are many possible configurations of resonators, numerical experiments are needed for an effective comparative analysis. We investigate metasurfaces consisting of rectangular stripline resonators arranged on a dielectric substrate in a checkerboard pattern in two configurations. The aim of the study is to obtain scattering diagrams in numerical experiments and compare them with real structures. Materials and Methods: In this paper a computer simulation of the interaction of metasurfaces with the microwave radiation in open space is carried out using the CST Studio package with a time domain solver. Calculations were performed for several frequencies in the range of 16 to 25 GHz. Experiments were then carried out with real structures at the same frequencies, using a bistatic method of measurements. The structures, with single resonators measuring 2×4.2 mm matching the frequency range, consisted of etched copper-plated FR4 sheets overlaid on a metal plate. Results: The results show that the value of the normal component of the reflected electromagnetic wave decreases as the incident frequency approaches the resonance frequency. Also, side lobes, with a frequency-dependent magnitude, are observed. The scattering diagrams obtained with real samples show the same characteristic features with differences caused by physical particularities of the receiving antenna as well as the presence of diffraction effects. Both structures examined have shown high incident wave scattering, which is clearly indicated by the redistribution of the central lobe in diagrams. Comparison has shown that the simulated metasurfaces have similar patterns to the experimental diagrams. Conclusion: The comparative analysis has demonstrated a satisfactory fit of the simulation to the experiment. Further studies with structures of this type are planned in the future. It may be noted that the CST Studio package has worked well and will be used in future studies.

The paper presents tasks and approaches to their solutions in assessing vibration strength and dynamic safety of marine reactor equipment (for example: pumps, control driven rod mechanisms). The topicality of this work is determined by the experience of operating nuclear power plants. Development of digital computation models and computational analysis allowed us to exclude experimental validation of control driven rod mechanisms seismic resistance. A digital computational model was developed for validating the dynamic safety and life time of the seal pot of the reactor facility main circulation pump. The model included the main circulation pump and the framework of the reactor facility. Computational and experimental analysis of the vibration state of the control and protection system drives was also carried out.

A significant part of the research on the effectiveness of various systems is devoted to the study of their functioning in a stationary mode. However, from the point of view of their practical application, it is of interest to study the functioning of such systems with varying workload intensity in transient, non-stationary modes of operation. And unlike the models for studying non-stationary systems, which are essentially based on the static values of distributions, this paper proposes a model using arbitrary probability distributions over time. The mathematical formalization of the model is based not on the application of the classical differential model in the time domain, but on the formal representation of the probabilities of the system states in the Laplace transform, i.e., in a complex way. Determining the values of the probabilities of the systems states is based on the principle of balance of “complex probabilities” which allows developing models of nonstationary queuing systems with arbitrary probability distributions of the arrival time of requests and their service, taking into account random or deterministic time delays. For the operational calculation of systems, it is proposed to use the developed application with a graphical user interface. The architecture of this application is presented in the form of a package diagram. The algorithm of the application is shown. Comparison of the application operation with programs MATLAB and MathCad for solving the problems of technical calculations was made when modeling the process of functioning of the standard unit of quantity and the robot control system. The advantages of using the developed application are given. The presented results can be applied by specialists involved in research on the effectiveness of various systems.

The exhausted design lifetime of main pipelines makes it necessary to extend their service life up to 100 years. This explains the urgency for development of repair designs providing postrepair lifetime level equal to the intact pipe. The paper presents the parametric study results of methods for increasing the lifetime of sleeves after repair to restore the pipeline functionality. Based on analysis of the stress state under external loads the paper offers a computer-simulated option of the sleeve design to provide a significantly increased lifetime.

THE PURPOSE. Currently, brushless motors – electric machines with permanent magnets on the rotor and a rotor position sensor controlled by a sinusoidal voltage from frequency converters, are widely used in mechatronic and robotic systems. The control algorithm is formed on the basis of information about the current values of the parameters brushless motor mechatronic system using a nominal or reference mathematical model, which is, as a rule, an idealized representation of a real device. The non-stationarity of the parameters object of study, as well as the possible uncertainty of its mathematical description due to the simplification of the mathematical model, lead to undesirable or unacceptable results when forming the control algorithm of the mechatronic system. The problem arises of analyzing the dynamic characteristics of a brushless motor under conditions of parametric uncertainty in order to determine the parameters that most affect the functioning of the mechatronic system and the phase coordinates that are sensitive to these changes.METHODS. When solving the problem, methods of the sensitivity theory are used to obtain the corresponding vector-matrix equations, the solution of which is carried out by means of the MatLab software environment.RESULTS. In this paper, sensitivity equations are obtained for the active resistance and projections of the stator winding inductance on the longitudinal and transverse coordinate axes, as well as for the moment of inertia of the brushless motor. A vector-matrix block diagram for calculating the sensitivity functions of a brushless motor is formed, the characteristic feature of which is the presence of a non-zero matrix of free terms, reduced to the input of the sensitivity model. The corresponding Simulink models were built to study the influence of the listed quasi-stationary parameters on the rotation speed and torque on the shaft of the object of study. An analysis of the statistical characteristics additional motion of the specified phase coordinates of the brushless motor has been carried out, and graphical dependencies and steady-state values of dispersions and relative estimates have been obtained.CONCLUSION. An analysis of the dynamic characteristics of a brushless motor under conditions of parametric uncertainty made it possible to determine that the rotation speed of the machine is the most sensitive to parametric disturbances. This coordinate is the most informative and is of maximum interest in the formation of an optimization algorithm for a mechatronic system. The decisive role in the formation of the additional movement of the output coordinates of the brushless motor is made by a change in the projection of the stator inductance on the transverse coordinate axis, which is an order of magnitude greater than the contribution to the additional movement of coordinates from other unstable parameters. It is expedient to use the results obtained in the course of the study when constructing an optimal control algorithm for a mechatronic system under conditions of parametric uncertainty.

The paper considers the problem of keeping cars from rolling away on station railway tracks with a permissible slope of 0–2.5 ‰. The study presents the computer simulation results for the dynamic interaction of wheels with brake shoes installed on rails in the process of stopping a freight train car using standard brake shoes in the MSC.ADAMS engineering software package. In this case, various properties of the rail surface were taken into account, simulating favorable and unfavorable conditions for contact between the wheel, brake shoe and rail at braking due to both weather conditions and the peculiarities of station tracks location and operation. The interaction of the car wheels with the maximum axle load and the station brake shoes installed on the rails was studied at different initial velocities of the vehicle movement, as well as when it is at rest on tracks with the permissible slope under the conditions of ensuring the minimum friction between the wheel and the rail, as well as the interaction of rail and shoe was analyzed, which corresponds to the presence of the train on oily rails. It is demonstrated that it is not always possible for one brake shoe put on the oily rail to hold the train moving with the initial velocity more than 0.5 m/sec. Under other conditions of the wheel-brake shoe collision, the problem of keeping the train on the rails is also possible, due to such random factors as lateral wind load, rail icing, wear and deformation of the wheel surface and brake shoe, which reduce the dynamic friction coefficient between the contacting surfaces.

The increase in the cost of fuel and energy resource and the deterioration of the environment from the combustion of traditional fossil fuel, have led to a great interest in energy-saving technology by using secondary energy resources in the thermal energy of industrial, housing and communal services using heat pump units in Russia and abroad. This paper analyzes the well-known two-stage heat pump units, and reveals their advantages in comparison with single-stage. The modeling of a highly efficient multistage vapor compression heat pump unit is proposed. Moreover, a method for calculating a multistage heat pump unit with a high coefficient of performance is presented. In addition, an example of calculating the thermodynamic cycle of a four-stage heat pump unit is presented. The influence of the number of stages on the increase in coefficient of performance in relation to a single-stage heat pump unit, the effect of the temperature difference between the temperature of the high-potential heat source and the temperature of the low-potential heat source on the coefficient of performance were analyzed. In addition, the influence of the initial value of the temperature of the high-potential heat source before heating during the course in the heat pump unit on the value of coefficient of performance for a different number of stages is analyzed under the condition of a constant difference between the heating temperature of the high-potential heat source at the outlet of the heat pump unit and the temperature of the low-potential heat source.

Background. The fi nite element method is gaining acknowledgment in Russia and other developed countries in a range of areas, including medicine. In stomatology, the method is applicable in research and implication of novel treatment and relevant material design.Objective. The review highlights usage of the fi nite element method in computer simulation to improve quality of patient dental care.Methods. The review analyses the state-of-the-art in current scientific literature. Records were mined in the PubMed and e-Library databases at a depth of 10 years, with selective inclusion of earlier articles. The query keywords were: finite element method [метод конечных элементов], computer simulation [компьютерная симуляция], quality of life improvement [повышение качества жизни], oral diseases [заболевания полости рта], dental treatment [стоматологическое лечение].Results. The review systematically surveys 56 scientific papers in the focus area for current state-of-the-art in the finite element analysis-empowered simulation in dentistry. The method’s rising employment is conditioned by its flexibility, 3D-object modelling simplicity and the rapid acquisition of reliable high-quality output. Its undoubted paramount advantage in dentistry is an explicit software visualisation of reliable results through co-modelling of multiple oral parameters.Conclusion. The growing acquaintance, mastering and use of this technique among researchers around the globe will give impetus to novel diagnosis and treatment, as well as relevant management algorithms in particular patient categories to enable personalisation of even mass dental check-up. This will reduce the number of visits, peri- and posttreatment error and complication rates for the improved patient’s quality of life and social rehabilitation.

This paper is devoted to the studies of the specific features of the simulation of the particle diffusion processes in space – periodic potentials using Langevin equations. Different methods used for the presetting of initial conditions and their effect on the obtained solutions have been analyzed. It is shown that the system is nonequilibrium for all the methods of the presetting of initial conditions during a certain time interval of ttrm. This interval is increased as 1/γ with a decrease in the friction coefficient. A reasonable description of the transient processes of particle transport and diffusion requires a preliminary system thermalization procedure. A new method of the presetting of initial conditions that provides the most accurate description of equilibrium system has been suggested. It consists in the generation of the initial particle coordinates and velocities that correspond to the equilibrium distribution of harmonic oscillators with a specified temperature. The use of such initial conditions enables the computations with a good accuracy using no thermalization procedure at T < 0.1. The classic method of the determination of diffusion coefficients D as a limit limt→ꝏ (σ2/t) has been analyzed. It was shown that the use of it for computer-aided calculations is limited by the restricted computational time. It results in that the computation of D under certain conditions becomes impossible. A new method was suggested for the determination of the diffusion coefficient using the linear approximation of the dependence of dispersion on time. This approximation can only be possible after the kinetic temperature attains its stationary value. The suggested method requires several orders of magnitude less time in comparison to the classic method. As a result, it enables the computation of the diffusion coefficient even in the cases of total previous failure. The obtained data are of great importance for correct simulation computations of diffusion processes and for the appropriate physical interpretations of obtained data.

In this paper the kinetics of the growth of Ag clusters in AgBr microcrystals of the photographic emulsion SP-1 with sensitivity 6 units GOST during illuminating with laser radiation λ = 490 nm, P = 10 mW; λ = 633 nm, P = 10 mW, P = 2.5 mW, P = 0.98 mW; λ = 850 nm, P = 10 mW; λ = 325 nm, P = 3 mW was investigated using the computer model and found that the influence of the laser light power on the growth of Ag clusters more efficiently than the photon energy. [ABSTRACT FROM AUTHOR]

The paper under scrutiny demonstrates numerical simulation results of thermal modes of the nanosatellite developed at the National Technical University of Ukraine "Kyiv Polytechnic Institute". It is designed to conduct scientific and applied research into the Earth remote sensing in the low Earth orbit with a solar pointing. In addition, we compare the obtained results with numerical simulation results of the "FalconSat-2" small satellite developed by the United States Air Force Academy. [ABSTRACT FROM AUTHOR]

This paper proposes the algorithm for decreasing the blinks influence at the analysis of the iridologycal image of the eye. It allows improving the reliability and accuracy of pupil's edge detection. Its advantages and efficiency are confirmed by the results of numerical simulations. This algorithm is based on the detection of an encompassing rectangle for all pupil edge points. Each point of the rectangle is connected with the image center. Finally, we remove all edge points on this ray, except the first edge point. [ABSTRACT FROM AUTHOR]

The paper considers an extruder as an object of mathematical modeling. We address the issue of mathematical modeling of the thermal mode control of extrusion process of polymeric materials. Crucially, we develop a mathematical model, which takes into account basic factors, influencing the increase of work efficiency of the extruder. [ABSTRACT FROM AUTHOR]

This paper outlines the approach to resolve the program motion task at the airplane automatic alignment. In particular, we consider the basic requirements for the longitudinal motion program of the airplane in the landing stage. We also provide some recommendations for the law assignment of the height change and implement the calculation algorithm of the possible trajectory variant. On the experimental side, synthesis of such law is carried out for the specific airplane and computer modeling of the motion on the calculated trajectory is executed. [ABSTRACT FROM AUTHOR]

Photovoltaic power plants have non-linear voltage-current characteristic, with specific maximum power point, which depends on operating conditions, viz. irradiation and temperature. In targeting the maximum power, it is by far known that the photovoltaic arrays have to operate at the maximum power point despite unpredicted weather changes. For this reason the controllers of all photovoltaic power electronic converters employ some method for maximum power point tracking. This paper makes an emphasis on model predictive controller as a control method for controlling the maximum power point tracking through the utilization of the well-known algorithm namely the Perturb and Observe technique. Further, during the advanced stages of this research study, the model will compare the results obtained for tracking the maximum power point from model predictive controller and a PID-controller as they are integrated Perturb and Observe algorithm. The obtained results will verify that the adaptive PID-controller Perturb and Observe algorithm has limitation for tracking the precise MPP during the transient insulation conditions. As compared to the proposed adaptive/modified model predictive controller for Perturb and Observe algorithm we illustrate that by adopting this method we will get to establish more accurate and efficient results of the obtained power in any dynamic environmental conditions: advantages as on regulation time (six times under the accepted experimental conditions) and by the number of fluctuations.

The focus of this paper is on the study of loading parameters of the mining dump truck drive wheels with twin wheels based on the computer simulation. A comparative assessment of the loading of the wheels’ electric drive is given for the design with and without cross-axle differential on the twin wheels. The expediency of using the cross-axle differential on the twin wheels, which reduces the required power and loadings, as well as slip, is shown. Computer simulation is performed using the ADAMS program.

The paper presents the results of a computer simulation by using a molecular dynamics method of synthesizing binary Cu – Au nanoclusters by condensation from a gaseous phase. To calculate the interatomic interaction forces, a modified tight-binding potentials with a fixed cutoff radius was used. The initial point of the process of condensation of nanoparticles from the gas phase was a configuration containing Cu and Au atoms (total number of 91124) distributed in a simple cubic lattice with the lattice parameter of 30aB, where aB is the Bohr radius (the periodic boundary conditions were used). For the analysis, we selected the initial configurations of different chemical compositions: Cu3Au, CuAu, Cu90Au10, Cu60Au40 which were cooled with the liquid nitrogen during the condensation process.

In this paper, the process of maturation of an aqueous solution of L-cysteine and silver nitrate using the method of atomistic molecular dynamics is investigated. To study the maturation process, an atomistic model of the solution was developed. The study allowed to obtain new data on the structure of silver mercaptide clusters and the role of their structural features in the process of further self-organization.

One of the technological challenges for hydrogen materials science (including the ITER project) is the currently active search for structural materials with various potential applications that will have predetermined limits of hydrogen permeability. One of the experimental methods is thermal desorption spectrometry (TDS). A hydrogen-saturated sample is degassed under vacuum and monotone heating. The desorption flux is measured by mass spectrometer to determine the character of interactions of hydrogen isotopes with the solid. The paper presents a distributed boundary-value problem of thermal desorption with dynamical boundary conditions and a numerical method for TDS spectrum simulation, where only integration of a nonlinear system of low order (compared with, e.g., the method of lines) ordinary differential equations (ODE) is required. It has been suggested dissolution and desorption coefficients estimation method in a real dynamic interaction of surface and diffusion processes without the artificial division of studies into diffusion limited regime (DLR) and surface limited regime (SLR). This work is supported by the Russian Foundation for Basic Research (project № 15-01-00744).

The paper is devoted to the definition of the parameters of the multilinear model of elasto-plastic deformation of metals used in calculating the stress-strain state and predicting the destruction of mechanical-engineering structures. The proposed method for identifying the parameters of a multilinear metal model involves a transition from the conditional (engineering) values of stresses and deformations to the true values. A distinctive feature of the technique is the consideration of the stress-strain state in the neck of the sample and the recommendations for determining the intermediate parameters of the material model. For the purpose of approbation of the developed technique in the software complex ANSYS LS-DYNA, a computer simulation of flat tensile tests was carried out. In the calculation, the identified parameters of the model for steel 20 were used. The simulation error, calculated from the value of the relative elongation of the sample at the time of failure, was 1,8 %. The obtained parameters of the model were also used in modeling the three-point bending of beams of rectangular section 60×40×3 mm from steel 20. Comparison of the calculation results with experimental data showed a difference in the control values of bending forces up to 17 %. This difference is caused by hardening of the material at the corners of the cross-section of the beams. A method is proposed for taking this effect into account on the basis of recalculation of the inertial characteristics of the cross section. This made it possible to reduce the difference in the calculated results from the experimental up to 1,1 %.

The paper describes diffusion of particles in a tilted spatially periodic potential under the action of external forces in the case of a low friction. It is shown that in underdamped systems, a region of temperature-abnormal diffusivity (TAD) exists, in which the diffusion coefficient increases with decreasing temperature. The TAD width and its position depend on the friction coefficient and the system parameters. The analytical expression for diffusion coefficients in TAD area is derived. These results are important for experimental investigations of TAD and its application.

The paper presents research results on the characteristics of Hall sensor based on the AlGaN/GaN heterostructure with various geometric parameters of the active region operating in the temperature range from -25 to 400ºC. The research was performed using device-technological simulation. The active layer of the proposed structure is a two-dimensional electron gas region, which is formed between the barrier layer Al0,3Ga0,7N and the undoped GaN channel layer. The results (room temperature current-related magnetic sensitivity 66.4 V/(A·T) and very low temperature cross sensitivity of 0,0273%/ºC) indicate the prospects of the proposed solutions for the practical use.

The results of verification carried out for investigations of hydrodynamic effect on reentry conicalsegmental space vehicle are presented in the paper. The program complex Flow Vision is used for this analysis. The purpose of the study is verification of using Flow Vision program complex for problem solving mentioned above on the base of comparison between calculated and experimental data, obtained on the Apollo landing models and new development reentry spacecraft of manned transporting spaceship designed by RSC Energia. The comparison was carried out through the data of pressure values on spacecraft model surfaces during its water landing and inertia center motion parameters. The results of study show good agreement between experimental and calculated data of force effects on vehicle construction during water landing and its motion parameters in the water medium. Computer simulation sufficiently well reproduces influence of initial velocities water entry angles variations on water landing process. Using of computer simulation provides simultaneous acquisition of all data information needed for investigation of water landing peculiarities during construction design, notably, hydrodynamic effects for structural strength calculations, parameters and dynamics of center mass motion and vehicle revolution around center mass for estimation water landing conditions, as well as vehicle stability after landing. Obtained results confirm suitability of using Flow Vision program complex for water landing vehicle investigations and investigations of influence of different landing regimes through wide initial condition change range, that permits considerably decrease extent of expensive experimental tests and realize landing conditions which are sufficiently complicated for realizing in model physical experiments.

The paper deals with the possibility of complex formation of therapeutic Semax peptides with lysine dendrimer by molecular modeling methods. Dendrimers are often used for delivery of drugs and biological molecules (e.g., DNA, peptides and polysaccharides). Since lysine dendrimers are less toxic than conventional synthetic dendrimers (e.g., polyamidoamine (PAMAM) dendrimer), we chose them and studied two systems containing dendrimer and the different number of Semax peptides. The study was carried out by molecular dynamics method. It was obtained that the stable complexes were formed in both cases. The equilibrium structures of these complexes were investigated. These complexes can be used in the future in therapy of various diseases as Semax peptides have significant antioxidant, antihypoxic and neuroprotecting action.

The following paper considers the process of classification of polydisperse free-flowing material according to granulometric composition using a gravitational air classificator. There were considered the problems of the purity of separation of polydisperse bulk materials and methods for increasing the degree of separation of particles. There were presented and analyzed obtained the results of the comparison, the data of experimental research and computer simulation of two-phase hydrodynamics flow by CFD methods. The versatility of this complex allowed carrying out simulation of the process using various parameters. As a result, were obtained optimal operating parameters, which were experimentally verified. Based on the obtained data as a result of numerical modelling, the possibility of increasing gas flow influence to the polydispersed material were found, as well as organization along the walls of coarse fraction downward flow by dint of the optimizing the devise design (specifically through the organization of additional inlets for airflow) were obtained.

The following paper considers the process of classification of polydisperse free-flowing material according to granulometric composition using a gravitational air classificator. There were considered the problems of the purity of separation of polydisperse bulk materials and methods for increasing the degree of separation of particles. There were presented and analyzed obtained the results of the comparison, the data of experimental research and computer simulation of two-phase hydrodynamics flow by CFD methods. The versatility of this complex allowed carrying out simulation of the process using various parameters. As a result, were obtained optimal operating parameters, which were experimentally verified. Based on the obtained data as a result of numerical modelling, the possibility of increasing gas flow influence to the polydispersed material were found, as well as organization along the walls of coarse fraction downward flow by dint of the optimizing the devise design (specifically through the organization of additional inlets for airflow) were obtained.

This paper describes the influence of modern crustal movements and the recently activated Precambrian structural plan on the relief of theLakeLadogaregion. It presents the results of comprehensive studies, including processing of the regional geological and geomorphological data by the modern methods, as the major novelty of our work. The solutions of earthquake focal mechanisms suggest the current subhorizontal NW compression in the study area. Based on the computer simulation by the Roxar software, we have identified areas wherein new fractures are most likely to occur, determined the dominant directions of such fractures, and revealed the areas of intense vertical movements in the given stress state. The input database included a digital model of the relief and the spatial patterns of ancient faults represented by large-size inhomogeneities influencing the stress field. Strain values were estimated from the horizontal displacements recorded by the International GPS Service for Geodynamics (IGS) and the GPS networks in theRepublicofKareliaand the southeastern regions ofFinland. Using the LESSA software, we have estima­ted the relief orientation characteristics: the density of lineaments, and elongation lines, which are indicative of the changes in the dominant directions of the strike of the lineaments (‘hatches’) in the study area. By interpreting the satellite images and the topographic maps (scale 1:20000), we reveal a number of geological structures, such as gra­nite-gneiss domes and large-size faults, which are directly reflected in the relief. The study results give grounds to establish an indirect relationship between the relief and the modern field of deformation: the areas with high strain values correspond to the areas with steep slopes. The computer simulation data show a NE-trending linear zone with the increased amplitudes of vertical movements. This zone occupies the region along the NW shoreLakeLadoga. In the block divisibility scheme based on the relief analysis, this region is comprised of blocks that are small in area: the Pearson correlation coefficient between the density of the block boundaries and the vertical displacements amounts to 65 %. In addition, this zone is distinguished by an increased permeability of the crust, which was estimated from the helium survey data. Most of the seismic events occurred in the areas characterized by either high or medium probability of new fracturing in case of NW compression. This gives an argument in support of the conclusion that compression takes place in theLadoga Lakeregion at the present stage. According to estimations by the LESSA software, the maximum densities of the linear relief elements correlate with the spatial patterns of the Precambrian faults. A number of faults and granite-gneiss domes are directly manifested in the relief, reflecting the inherited nature of the development of the latter.

The work objective is to evaluate the effective heat conductivity coefficient of a material with parallel cylindrical inclusions with equal diameters.Since an analytical solution of the heat conductivity equation is quite difficult, we apply a mathematical model, in which a random motion of the imaginary "heat particles" represents the process of heat conduction. These particles represent a sample of distribution, which has density being, at every moment, proportional to that of the heat energy. Thus, using the Wiener processes enables obtaining the solution of the heat conductivity equation. The velocity of "heat particles" depends on the temperature conductivity coefficient of the material in which the particles are moving at the moment.The paper considers a layer fragment of the composite material whose effective temperature conductivity coefficient is to be evaluated. As a criterion of heat conduction, we consider the probability P, assuming that a heat particle, having started from one surface of the layer, reaches its opposite surface for a time less than T. For a homogeneous isotropic material, this probability is analytically found.We perform a series of computer experiments to simulate heat conduction through a layer of the composite material, the source of heat being applied to one surface of the layer, and heat being absorbed at the opposite surface. By statistical elaboration of their results we find confidence intervals for P. Therefrom we find confidence intervals for the effective temperature conductivity coefficients (by comparing with homogeneous materials yielding the same value of P). Next, the effective heat conductivity coefficients are obtained through multiplying the effective temperature conductivity by the average volume heat capacity.We took various proportions between cylinder diameters and distances between them. The results obtained are consistent with analytical ones. The method elaborated allows finding effective heat conductivity coefficients for composite materials with arbitrary-shaped inclusions.

The process of heat conduction can be modeled via random motion of particles of heat energy, although these particles do not physically exist: they are considered as special formal objects. The speed of diffusion of heat particles in each material is proportional to its temperature conductivity coefficient. This mathematical model underlying the method of obtaining the effective heat conductivity coefficient of a composite material described in the previous paper \Heat conductivity of composite materials with included balls of zero heat conductivity" now is being modified in order to deal with materials with various nonzero heat conductivity and capacity coefficients. Namely, when a particle passes from one material to another one, having smaller heat conductivity, it is reflected from the frontier with a certain probability.As a criterion of heat conductivity, we consider the probability that a heat particle starting on one surface of a composite layer, goes to its other surface in a time shorter than T. For a homogeneous material, this probability is calculated theoretically.For a layer of a composite, we perform a multiple computational experiment modeling heat conduction, and for the desired probability we find the confidence interval, wherefrom we obtain the confidence interval for the effective temperature conductivity coefficient, and, finally, calculate the effective heat conductivity coefficient.We have considered inclusions of materials with heat conductivity and volume heat capacity coefficients differing from those of the matrix in 3 times up or down. Ball inclusions of equal size were situated in a cubic order or chaotically. The ratio of the ball radius to the size of cubes was 0.2, 0.3, or 0.4.In series of 4300 randomly moving particles, in all cases considered, the difference between the effective heat conductivity coefficients and those calculated by other methods does not exceed a statistical error.The developed method makes it possible to obtain effective heat conductivity coefficients for composites with inclusions of any size and shape; it can be applied also in a case of inclusions from several materials. The results obtained are reliable and only the computer capability restricts their exactness.

Problem statement. Improvement of thermoelectric figure of merit is connected with the usage of nanostructured thermoelectric materials fabricated from powders by the spark plasma sintering (SPS) method. Preservation of powder nanostructure during sintering is possible at optimum temperature modes of thermoelectrics fabrication. The choice of these modes becomes complicated because of anisotropic properties of semiconductor thermoelectric materials. The decision of the given problem by sintering process simulation demands the competent approach to the problem formulation, a correct specification of thermoelectric properties, the properties of materials forming working installation, and also corrects boundary conditions. The paper deals with the efficient model for sintering of thermoelectrics. Methods. Sintering process of the bismuth telluride thermoelectric material by means of SPS-511S installation is considered. Temperature dependences of electric and thermal conductivities of bismuth telluride, and also temperature dependences of installation elements materials are taken into account. It is shown that temperature distribution in the sample can be defined within the limits of a stationary problem. The simulation is carried out in the software product Comsol Multiphysics. Boundary conditions include convective heat exchange and also radiation under Stefan-Boltzmann law. Results. Computer simulation of electric and thermal processes at spark plasma sintering is carried out. Temperature and electric potential distributions in a sample are obtained at the sintering conditions. Determinative role of graphite compression mould in formation of the temperature field in samples is shown. The influence of geometrical sizes of a graphite compression mould on sintering conditions of nanostructured thermoelectrics is analyzed. Practical importance. The optimum sizes of a cylindrical compression mould for fabrication of volume homogeneous samples based on bismuth telluride are determined. Ways of updating for the sintering process are shown giving the possibility to fabricating thermoelectric samples with predicted properties.

The paper deals with investigation of the conformational properties of some charged homopolypeptides in dilute aqueous solutions by computer simulation. A method of molecular dynamics for the full-atomic models of polyaspartic acid and polylysine with explicit account of water and counter-ions is used for this purpose. For systems containing these polypeptides we calculated time trajectories and the size, shape, distribution functions and time correlation functions of inertia radius and the distances between the ends of peptide chains. We have also calculated the solvatation characteristics of considered polyelectrolytes. We have found out that polyaspartic acid in dilute aqueous solution has more compact structure and more spherical shape than polylysine. We have shown that these differences are due to different interaction between the polypeptides and water molecules (in particular, the quality and quantity of hydrogen bonds formed by these peptides with water), and the difference in an amount of ion pairs formed by the charged groups of the peptides and counter-ions. The obtained results should be taken into account for elaboration of new products based on the investigated peptides and their usage in various industrial and biomedical applications.

The paper presents a developed multi-scale model of sandwich honeycomb structures. The model allows us both to calculate effective elastic-strength characteristics of honeycomb and forced covering of sandwich, and to find a 3D stress-strain state of structures using the threedimensional elastic theory for non- homogeneous media. On the basis of finite element analysis it is shown, that under four-point bending the maximal value of bending and shear stresses in the sandwich honeycomb structures are realized in the zone of applied force and plate support. Here the local stress maxima approximately 2-3 times exceed the “engineering” theoretical plate values of bending and shear stresses in the middle of panel. It is established that at tests for fourpoint bending there is a failure of the honeycomb sandwich panels because of the local adhesion failure rather than because of the covering exfoliation off the honeycomb core in the middle of panel.

In this paper, an analysis of state-of-the-art and an attempt to generalize the basic principles of multiphysical (coupled) computer simulation of various electromagnetic devices (electrical machines, induction heaters, actuators, electrophysical devices, etc.) are presented. The analysis is based on the author’s wide experience in solving various practical problems regarding design and operation of a variety of innovative machines and devices as well as on studies carried out by other researchers