Yu. N. Zolotukhin, A. S. Maltsev, M. N. Filippov, K. Yu. Kotov, A. S. Dimova
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: управление группой мобильных роботов, синтез систем автоматического регулирования, адаптация параметров регулятора, моделирование, Robot Operating System, control of a group of mobile robots, synthesis of automatic control systems, adaptation of regulator parameters, modeling, robot operating system
A control method and software structure for solving the problem of control of motion of a group of robots along a prescribed trajectory with preserving the chosen configuration under the conditions of unsteady dynamic characteristics of individual robots is proposed.
E. L. Eremin, L. V. Chepak
Amur State University, Blagoveshchensk, Russia
Keywords: control delay, non-affine system, hyper-stability criterion, stationary observer, a priori uncertainty
This paper deals with the synthesis of a combined output control system for a nonlinear non-affine plant with delay in the control channel operating under conditions of a priori parametric uncertainty subject to external interference. The simulation results confirm the performance of the synthesized control system, and the resulting controller provides tracking of the plant output after the reference signal.
N. D. Goldina
Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: интерференционный фильтр, тонкие металлические плёнки, УФ-диапазон, interference filter, thin metal films, UV range
A metal-dielectric narrow-band filter for a wavelength of 270 nm is calculated within the framework of the conductive surface model for characterization of the properties of thin metal films. It is demonstrated that inclusion of four thin molybdenum films to the dielectric structure ensures effective transmission cut-off at <1.5 % in the visible range of the spectrum with the maximum transmittance more than 50 % for the identified wavelength and the spectral width of the filter <5 nm.
V. P. Bessmeltsev1, A. N. Pavlenko2, V. I. Zhukov3 1Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: капиллярно-пористое покрытие, микротекстурированная поверхность, аддитивные технологии, SLМ/SLS, интенсификация теплообмена при кипении, capillary-porous coating, microtextured surface, additive technologies, SLМ/SLS, intensification of heat transfer during boiling
Application of the method of layer-by-layer selective laser sintering of a metal powder for depositing capillary-porous coatings with a prescribed porosity onto heat-releasing surfaces is considered. Implementation of this method in experimental investigations of the boiling process on modified surfaces allows broad-range variations of the main parameters of microstructured capillary-porous coatings and other three-dimensional structures: material, porosity, amplitude (height), thickness of the residual layer and wavelength of capillary-porous coatings, and size and shape of three-dimensional ordered microtextures. It is demonstrated that the use of this technology can increase the coefficient of heat release in the case of boiling on the surface with a capillary-porous coating by several times as compared to the uncoated surface.
S. V. Savel'kaev1, V. A. Litovchenko2, N. V. Zarzhetskaya1 1Siberian State University of Geosystems and Technologies, Novosibirsk, Russia 2Novosibirsk Higher Military Command School, Novosibirsk, Russia
Keywords: S-параметры, транзистор, адекватное измерение, имитатор-анализатор, математическая модель, калибровка, сверхвысокочастотный усилитель и автогенератор, S-parameters, transistor, adequate measurement, simulator/analyzer, mathematical model, calibration, microwave amplifiers and oscillators
In this paper, we consider the two-signal method and a modified two-signal method for measuring the S-parameters of passive two-ports poles and a method for adequately measuring the S-parameters of two-ports, such as transistors, developed on their basis. The methods are implemented by a coaxial simulator/analyzer of microwave amplifiers and oscillators in its measuring channels matched or mismatched with loads. The field of application and the interrelation between these methods are investigated, and their advantages and disadvantages are discussed. Data on the maximum measurement error of the methods are presented.
A. N. Aparnikov, E. V. Buryi, N. E. Orlov
Bauman Moscow State Technical University, Moscow, Russia
Keywords: линейка лазерных диодов, температура, вольт-амперная характеристика, разность потенциалов, laser diode bar, temperature, current-voltage characteristic, electric potential difference
Based on an analysis of differences between the experimentally measured temperature dependence of the current-voltage characteristic (I-V curve) of a laser diode bar (LDB) with AlGaAs/GaAs heterostructure and the dependence obtained in accordance with the well-known model of light-emitting diodes, assumptions were made about the sources of these differences. The agreement between experimental and modeled dependencies is significantly improved by taking into consideration the change in the resistance of LDB layers caused by temperature change. It is shown that when the injection current is known, the measured voltage drop across the LDB can be used to estimate the temperature of the diode active region in order to implement thermal stabilization for solid-state laser pumping systems based on high-power laser diodes.
A. V. Likhachev
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: классификатор элементов изображения, апостериорные вероятности, image element classifier, posterior probabilities
A classifier for operation with 1 pixel image fragments is proposed. Separation of elements into an object and background is based on posterior probabilities, which are calculated using a histogram. A computational experiment has shown that the developed algorithm provides a more accurate classification than the separation according to the brightness threshold determined from the condition of the minimum weighted sum of errors of the first and second kind.
A. K. Shakenov
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: обнаружение и распознавание объектов, свёрточные нейронные сети, машинное обучение, малоразмерные объекты, object detection and recognition, convolutional neural networks, machine learning, small objects
Several approaches to the use of neural networks for detecting objects on spatially inhomogeneous backgrounds are considered. A method for constructing a classifier for detecting objects directly from observed fragments has been implemented. An approach consisting of a combination of the matched linear filtering method and convolutional neural networks is proposed. It is shown that this approach reduces the likelihood of false alarms while maintaining the object detection probability.
H. Tan, L. Li, G. Wu, Q. Wang
State Grid Chongqing Electric Power Research Institute, Chongqing, China
Keywords: закрытый газовый смеситель, регистрация цифровых изображений, подавление шума на рентгенограммах, повышение качества изображения, gas insulated combination, digital imaging detection, X-ray, image denoising, image enhancement
The existence of internal structural defects in Gas Insulated Combination (GIS) seriously affects the normal operation of equipment, and it needs an efficient and non-destructive detection method. This study is focused on the feasibility of X-ray digital imaging detection in GIS equipment monitoring. First, the digital imaging detection process is briefly introduced. Then, in order to obtain high-quality digital images, a correlation coefficient is introduced to improve the nonlocal mean filtering denoising algorithm. In terms of image enhancement, a histogram equalization method is introduced, and then an improved contrast-limited adaptive histogram equalization (CLAHE) method is proposed for image denoising. The detection system and image processing method of this study are used to detect two GIS equipment units of the Chongqing Electric Power Company. It is found that this method clearly and accurately detects the equipment defects and proved its reliability. This study provides some theoretical basis for the further promotion of the X-ray DR technology in GIS equipment defect detection.
A. V. Lapko1,2, V. A. Lapko1,2 1Institute of Computational Modeling, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia 2Reshetnev Siberian University of Science and Technology, Krasnoyarsk, Russia
Keywords: непараметрический алгоритм распознавания образов, максимум апостериорной вероятности, ядерная оценка плотности вероятности, быстрый выбор коэффициентов размытости, оценка плотности вероятности типа Розенблатта-Парзена, nonparametric algorithm of pattern recognition, a posteriori probability maximum, kernel estimate of the probability density, fast bandwidth selection, estimate of the probability density of the Parzen - Rosenblatt type
A method of fast bandwidth selection in a nonparametric algorithm of pattern recognition corresponding to the a posteriori probability maximum criterion is proposed. The algorithm is based on the results of studying the asymptotic properties of the nonparametric estimate of the separating surface equation and probability densities in solving a two-alternative problem of pattern recognition. The proposed method is compared with the traditional approach based on minimizing the classification error probability estimate.
A. A. Zabolotskii
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: наноматериалы, хиральные структуры, солитоны, nanomaterials, chiral structures, solitons
Effect of nonlocality on the polarization dynamics of an electric field pulse in a medium with cubic nonlinearity is under study. Nonlinear equations are solved using a variational approach. It is shown that nonlocal and chiral effects cause trajectory oscillations and nonlinear rotation of the soliton pulse polarization of the field.
A.N. Gruzdev, A.A. Isakov, P.P. Anikin
A.M. Obukhov Institute of Atmospheric Physics Russian Academy of Sciences, Moscow, Russia
Keywords: аэрозоль, массовая концентрация, линейный тренд, множественная линейная регрессия, автокорреляция данных, aerosol, mass concentration, linear trend, multiple linear regression, autocorrelation of data
Estimates of seasonally dependent long-term trends in the mass concentration of near-surface aerosol based on the measurements at Zvenigorod Research Station of A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, in 1991-2018 are presented. The analysis was performed by the method of multiple linear regression taking into account data autocorrelation on long time scales. Statistically significant negative spring and summer trends were derived for 1991-2002 and 2013-2018, respectively; possible causes of the trends are discussed.
N.V. Podnebesnykh, I.I. Ippolitov
Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: приземная температура воздуха, приземное давление, облачность, антициклоническая активность, территория Сибири, surface temperature, surface pressure, cloudiness, anticyclonic activity, the territory of Siberia
According to data from 163 meteorological stations over the territory of Siberia (50º-70º N; 60º-110º E) the air temperature, surface pressure, and cloud cover during the winter period (December-February) were calculated over 1976-2011. Using surface synoptic charts, time series of winter anticyclone characteristics, such as total number and pressure centers, were derived. Two time intervals: 1976-1990 and 1991-2011 were found in variations in climate and anticyclone activity characteristics. Over the first period, temperature and cloud amount increase, and surface pressure falls, the number of anticyclones decreases, and their intensification occurs, i.e., the pressure increases in their centers. Over the second period, the tendencies are opposite. The correlation analysis between the climate variables and anticyclonic activity characteristics allowed us to consistently describe the impact of anticyclones on the surface pressure and cloudiness.
M.N. Alekseeva1, E.A. Golovatskaya2, I.G. Yashchenko1 1Institute of Petroleum Chemistry of the Siberian Branch of the RAS, Tomsk, Russia 2Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: пожары, гари, космические снимки, геоданные, леса, болота, атмосфера, загрязняющее вещество, fires, burnt areas, satellite imagery, geodata, forests, swamps, atmosphere, pollutant
In the created geoinformation system, the analysis of air pollution from fires of drained peatlands in the territories of Bakcharsky and Shegarsky forest districts of the Tomsk region has been performed. Parameters of horizontal and vertical perturbations in the air layer due to a fire in the area of Iksa were calculated, which including a maximum vertical dimension of the convective column (mixture of air with products of complete and incomplete combustion rising above the fire), heat emission, and the propagation velocity of the aerosol cloud of combustion products. The volumes of pollutant emissions from the fire have been calculated on the basis of geodata and those on the biomass of vegetation cover of the Iksa site. It is shown that significant amounts of carbon monoxide, carbon dioxide, and methane were emitted into the atmosphere due to the fire. The data on emissions of nitrogen oxide, soot, and ozone are also reported. At the present time, this site is characterized by the restoration of vegetation cover; the positive dynamics of the NDVI vegetation index has been calculated. The accumulation of biomass in the Iksa site and the presence of dead wood, as well as a road network indicate a high risk of vegetation and peat ignition and pollutant emissions to the atmosphere.
V.E. Pavlov1, I.V. Khvostov1, N.Y. Kurepina1, N.M. Kovalevskaya1, L.A. Khvorova2 1Institute for Water and Environmental Problems of the Siberian Branch of the RAS, Barnaul, Russia 2Altai State University, Barnaul, Russia
Keywords: хлорофилл, взвешенное вещество, Обская губа, Карское море, спектрофотометр MERIS, нормальные логарифмические распределения, chlorophyll, suspended matter, the Gulf of Ob, the Kara Sea, MERIS spectrophotometer, lognormal distributions
On the basis of long-term data obtained from the European ENVISAT satellite, the statistical analysis of chlorophyll and suspended matter concentrations in the Gulf of Ob and its extension to the Kara Sea from Bely Island to Novaya Zemlya was performed. It was found that empirical functions of chlorophyll and suspended matter concentration distribution in both water areas, including the coastal zone of the Gulf of Ob, tend to the lognormal law. Statistical parameters of distributions and characteristics of the latitudinal trends of logarithms of concentrations in the Kara Sea are determined. The obtained results are presented in graphical and tabular forms and can be used in modelling the distribution of dispersed components in the waters of the Arctic Ocean under study.
V.V. Belov, V.N. Abramochkin, A.N. Kudryavtsev, M.V. Tarasenkov, A.V. Fedosov, E.S. Poznakharev
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: измерение, коэффициент ослабления оптического излучения, водная среда, полевые и лабораторные эксперименты, measurement, optical radiation extinction coefficient, water medium, field and laboratory experiments
The composition and operation principle of an instrument for measuring the water extinction coefficient in real time are described, including measurements in water under the ice surface. Examples of instrument testing under field and laboratory conditions are given. The measuring instrument is recommended for estimation of maximal receiver-source distances when line-of-sight optoelectronic communication or communication on scattered laser radiation is possible.
A.S. Syrneva, V.S. Ayrapetyan
Siberian State University of Geosystems and Technologies, Novosibirsk, Russia
Keywords: частотный фильтр, явление полного внутреннего отражения, ширина полосы пропускания, интерференционная картина, спектр излучения, frequency filter, total internal reflection phenomenon, bandwidth, interference pattern, radiation spectrum
The results of experimental study of characteristics of a frequency filter designed on the basis of total internal reflection phenomenon are presented. The spectral width of semiconductor laser radiation in the visible region measured with this frequency filter two-fold narrows (from 18 to 10 cm-1 after passing through the frequency filter).
V.M. Orlovskii, V.A. Panarin, V.S. Ripenko
High Current Electronics Institute of the Siberian Branch of the RAS, Tomsk, Russia
Keywords: наносекундный поток электронов, спектр поглощения воды в ИК-диапазоне, проводимость воды, nanosecond electron flux, water absorption spectrum in infrared region, water conductivity
The absorption spectra of distilled and heavy water after treatment by a nanosecond electron flux are examined. A change in the absorption spectrum of the substance was recorded after multiple treatment of water. The analysis of the IR absorption spectra of water showed the difference between the absorption spectra of non-irradiated and irradiated water and а change in the latter over time.
A.Yu. Shikhovtsev1, A.V. Kiselev1, P.G. Kovadlo1, D.Yu. Kolobov1, V.P. Lukin2, V.E. Tomin1 1Institute of Solar-Terrestrial Physics of the Siberian Branch of the RAS, Irkutsk, Russia 2V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: атмосферная турбулентность, волновой фронт, телескоп, солнечные изображения, вертикальные профили турбулентности, atmospheric turbulence, wavefront, telescope, solar images, profiles of the turbulence
The modern tasks concerning the methods for recovering the altitude profiles of the atmospheric turbulence are discussed. An alternative method to the Slodar-technique is suggested for determining the altitudes of atmospheric layers characterized by strong turbulence. The method is based on estimation of the space-time crosscovariances between local wavefront slopes on subapertures spaced in the telescope field of view with a known angular displacement of an object observed due to the Sun motion. The turbulence characteristics are estimated for the Large Solar Vacuum Telescope site.
V.V. Kolosov, V.O. Troitskii
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: генерация второй гармоники, система нелинейных уравнений, численные схемы, second harmonic generation, system of nonlinear equations, numerical scheme
A technique is proposed for approximate solution of the system of equations responsible for second harmonic generation in nonlinear uniaxial crystals. The algorithm of this techniqueis is reduced to numerical calculation of a threefold integrated integral. The study consists of two parts. In the first part, two approximations are considered. These approximations allow the time for computation of twofold integrated integrals with respect to transverse coordinates to be shortened nearly two times in the situations most complicated for computations. The second part discusses an approximate technique for estimation of the power of interacting waves, which also allows the computation time to be decreased by an order of magnitude by means of a decrease in the minimal needed number of steps of the recurrent process. The results of the tests demonstrate that although the use of the approximations proposed decreases the accuracy of solution of the nonlinear problem, but nevertheless keeps the errors at an acceptably low level.
V.V. Kolosov, V.O. Troitskii
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: генерация второй гармоники, система нелинейных уравнений, численные схемы, second harmonic generation, system of nonlinear equations, numerical scheme
This paper is the second and the last part of the study. It presents the results of tests of the numerical scheme proposed in the first part. The approximate procedure for estimation of the power of interacting waves at the exit from the crystal is discussed. This procedure allows the computation time to be shortened by more than an order of magnitude by means of a decrease in the minimal needed number of steps of the recurrent process.
S. Ahmad1, M. Ashraf1, K. Ali2 1Centre for Advanced Studies in Pure and AppliedMathematics, Bahauddin Zakariya University, Multan, 60800, Pakistan 2Department of Basic Sciences and Humanities, Muhammad Nawaz Sharif University of Engineering and Technology, Multan, 60000, Pakistan
Keywords: вязкая диссипация, микрополярная жидкость, пористая среда, квазилинеаризация, viscous dissipation, micropolar fluid, porous medium, quasi-linearization
Taking into account the effect of viscous dissipation in the energy equation, we numerically explore the flow of an incompressible micropolar fluid with heat and mass transfer through a resistive porous medium between plane channel walls. By exploiting a similarity transformation, the governing partial differential equations are transformed into a system of nonlinear coupled ordinary differential equations, which are solved numerically for various problem parameters by means of quasi-linearization. It is found that the effect of viscous dissipation is to increase the heat and mass transfer rate at both the lower and upper walls of the channel.
I. N. Cherepanov, P. V. Krauzin
Perm State University, Perm, 614990, Russia
Keywords: модель твердых сфер, седиментация, вириальное разложение, уравнение Карнагана-Старлинга, solid sphere model, sedimentation, virial decomposition, Carnahan - Starling equation
Gas particle distribution simulated by solid spheres and located in a gravity field at a constant temperature is under study. A solid sphere model is poorly applicable to real gases, but it can be used to describe the distribution of nanoparticles in a colloidal solution. Various models of weakly nonideal gas are compared: virial expansion up to a second coefficient, a Wertheim - Thiel equation in a Percus - Yevick approximation, and a Carnahan - Starling approximation. In the case of virial expansion, an exact analytical solution for an equation of particle distribution by height is obtained. For more complex models, solutions are found using numerical methods. It is shown that accounting for a finite particle size leads to significant changes in the particle distribution as compared to the ideal gas distribution even at small volume fractions. The results obtained using virial decomposition are in good agreement with the results obtained using more complex models provided that the volume fraction of the impurity does not exceed 0.1.
V. V. Bulatov, Yu. V. Vladimirov
Ishlinsky Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow, 119526, Russia
Keywords: стратифицированная среда, внутренние гравитационные волны, частота плавучести, сдвиговые течения, stratified medium, internal gravitational waves, buoyancy frequency, shear flow
A problem of the far field of internal gravitational waves excited by an oscillating point source of perturbations in a stratified medium with a shear flow is solved. A model distribution of the shear flow velocity by depth is considered and an analytical solution to this problem is obtained in the form of a characteristic Green's function, expressed in terms of the modified Bessel functions of the imaginary index. Expressions for dispersion relations are obtained and integral representations of solutions are constructed. The dependences of the wave characteristics of the excited fields on the main parameters of the used stratification models, flows, and generation regimes are investigated.
V. V. Pak
V.I. Il'ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041, Russia
Keywords: стоксово течение, многослойное течение, неустойчивость при нулевых числах Рейнольдса, тектонофизика, складкообразование, Stokes flow, multilayer flow, instability at zero Reynolds numbers, tectonophysics, folding
Instability at zero Reynolds numbers in a three-layer Stokes flow of a viscous fluid with an inhomogeneous layer thickness in a two-dimensional region with a free boundary is investigated. The method of multiple scales to applied for constructing an asymptotic expansion of the solution of the boundary-value problem for the Stokes equations. The stability of the system of first-approximation equations is analyzed using the Fourier method, and it is concluded that the most significant increase in instability at zero Reynolds numbers occurs in the region of waves whose lengths are comparable with the thickness of the middle layer. In contrast to the case of a constant layer thickness, the instability parameters are variable. The mechanism of formation of geological folds is investigated.
N. M. Zubarev1,2, E. Yu. Prosviryakov3 1Institute of Electrophysics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620016, Russia 2Lebedev Physical Institute, Russian Academy of Science, Moscow, 119991, Russia 3Institute of Engineering Science, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620016, Russia
Keywords: слоистые течения, изобарические течения, точные решения, переопределенная система уравнений, условия совместности, layered flows, isobaric flows, exact solutions, overdetermined system of equations, compatibility conditions
This paper describes an overdetermined system of equations that describes three-dimensional layered unsteady flows of a viscous incompressible fluid at a constant pressure. Studying the compatibility of this system makes it possible to reduce it to coupled quasilinear parabolic equations for velocity components. The reduced equations allow constructing several classes of exact solutions. In particular, polynomial and spatially localized self-similar solutions of the motion equations are obtained. The passage to the limit of the case of an ideal fluid is investigated.
Yu. O. Kuyanova1,2, S. C. Presnyakov2, A. V. Dubovoi3, A. P. Chupakhin1,2, D. V. Parshin1,2 1Lavrent'ev Institute for Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia 2Novosibirsk National Research State University, Novosibirsk, 630090, Russia 3Federal Neurosurgical Center, Novosibirsk, 630048, Russia
Keywords: гидродинамика тройника, гемодинамика, сосудистый анастомоз, угол установки анастомоза, численная задача оптимизации, T-graft hydrodynamics, hemodynamics, vascular anastomosis, anastomosis angle, numerical optimization problem
The hydrodynamics of a T-graft is investigated as part of the problem of determining the optimal angle of vascular anastomosis during neurosurgery. Four possible angles corresponding to the most commonly used real configurations are considered: π/6, π/4, π/3, and π/2. The problem is solved numerically using the ANSYS code. The condition of minimum integral of the viscous dissipation energy is used as an optimality criterion. It is shown that the anastomosis angle π/3 is optimal and the angle π/4 is the least favorable.
G. Yu. Evtushok, A. V. Boiko, S. N. Yakovenko
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: устойчивая стратификация, вертикальный барьер, внутренние волны, зоны рециркуляции, численное моделирование, stable stratification, vertical barrier, internal waves, recirculation zones, numerical simulation
A numerical algorithm for solving CFD equations for the case of a stable stratified flow with a bluff body in the form of a thin vertical barrier generating internal waves is developed and verified with the use of the OpenFOAM software system. Numerical simulations of this flow are performed for different Froude numbers for steady and unsteady regimes of wave overturning; it is demonstrated that the results predicted by the proposed algorithm are qualitatively consistent with other available data. The reasons for the differences in the computed drag coefficient from the data obtained previously are discussed.
V. A. Babeshko1, O. V. Evdokimova1, O. M. Babeshko2 1Southern Scientific Center, Russian Academy of Science, Rostov-on-Don, 344006, Russia 2Kuban State University, Krasnodar, 350040, Russia
Keywords: метод блочного элемента, граничная задача, автоморфизм, псевдодифференциальные уравнения, клиновидная область, block element method, boundary-value problem, automorphism, pseudo-differential equations, wedge-shaped region
A boundary-value problem for a three-dimensional Helmholtz equation in a region shaped as a rectangular wedge of infinite extent is under consideration. An exact solution to this boundary-value problem is constructed in the form of a packed block element necessary for investigating more complex and even mixed problems for block structures. The conjugation of packed blocks into a block structure is carried out by constructing quotient topologies of the topological spaces of blocks, and the equivalence relations are interblock boundary conditions.
Z. Wang1,2, C. Zhang3, S.-J. Li2, J.-J. Liu1, H.-W. Zhang1 1Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, 100190, China 2School of Energy and Power Engineering, Shandong University, Jinan, 250061, China 3Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin, 300384, China
Keywords: пленочное охлаждение парами разнонаправленных струй, геометрические параметры, почковидные "антивихри", связанные мультиполя, температурные напряжения, double-reverse-jet film cooling (DRJFC), geometric parameters, anti-kidney vortices, multi-field coupling, thermal stress
In order to investigate the double-reverse-jet film cooling (DRJFC), the multi-field coupling calculating method is used to study the effect of geometric parameters on the resultant vortex structure and conjugate thermal-elastic property. The traditional streamwise film cooling is also investigated for comparison. The results indicate that the formation of effective anti-kidney vortices is the key to enhance the dimensionless temperature of DRJFC holes. At low blowing ratios, the streamwise or lateral distance between two DRJFC holes should be increased to widen the transverse shift of the jets, thus, to increase the cooling performance. At high blowing ratios, the lateral distance should be decreased to prevent two jets from separating apart so that the malfunction of the anti-kidney vortices could be avoided. The stress concentration resulting from the nonuniform temperature distribution is considered.
J.L. Fu1, L.C. Bai2,3, C. Zhang2,3, P.F. Ju2,3 1Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, 100190, China 2Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin, 300384, China 3National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology), Tianjin. 300384, China
Keywords: пленочное охлаждение, профилированные кратеры, глубина кратера, параметр вдува, пара "антивихрей" почковидной формы, эффективность охлаждения адиабатической стенки, film cooling, contoured crater, crater depth, blowing ratio, anti-kidney-shaped vortex pair, adiabatic cooling effectiveness
The present study deals with the flow field and cooling performance for flat-plate cylindrical film cooling holes embedded in contoured craters, especially considering the effect of the crater depth. A test matrix of the crater depth ranging from 0.25 to 1.25 times of the cylindrical hole diameter and the blowing ratio ranging from 0.5 to 2.0 is used in CFD computations. The numerical results show that the flow fields downstream from the hole exit can be altered significantly due to interaction between the ejected coolant and contoured crater. The cooling performance depends on both the specific crater depth and blowing ratio; however, the cratered hole is always superior to the cylindrical hole in terms of the area-averaged cooling effectiveness regardless of the crater depth and blowing ratio. The cratered hole with a crater depth equal to the hole diameter is recommended.
A. K. Rebrov1, I. S. Batraev2, T. T. B'yadovskii1, E. V. Gladkikh3, A. S. Useinov3, M. N. Khomyakov4 1Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia 2Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia 3Technological Institute for Superhard and Novel Carbon Materials, Troitsk, 142190, Russia 4Institute of Laser Physics SB RAS, Novosibirsk, 630090, Russia
Keywords: химическое газофазное осаждение, алмазное покрытие, детонационное напыление, промежуточные слои, механические измерения, chemical vapor deposition, diamond coating, detonation sputtering, intermediate layers, mechanical measurements
Results of studying the growth of diamond structures on steel samples with the use of intermediate layers of molybdenum or tungsten carbide cemented by cobalt are reported. The intermediate layers are deposited by means of detonation sputtering. Subsequent deposition of diamond films onto the clad steel samples is formed by the gas jet method and a special thermocatalytic reactor with extended activating surfaces. The nucleation process on the intermediate layer surfaces is intensified by preliminary seeding of the samples in a colloid solution containing nanodiamonds. Information about the phase and structural composition of the resultant samples and about the film surface morphology is obtained by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analysis. The tribology of the samples is studied with the use of hardness nano-sensor and by Rockwell hardness identation.
D. A. Pozharskii1, N. B. Zolotov2 1Don State Technical University, Rostov-on-Don, 344000, Russia 2Southern Federal University, Rostov-on-Don, 344090, Russia
Keywords: цилиндр из упругого неоднородного материала, контакт, асимптотика, cylinder made of an elastic nonhomogeneous material, contact, asymptotic
Contact problems for elastic hollow cylinders made of a nonhomogeneous materia are considered. The cylinders are subjected to uniformly distributed internal or external pressure and interact with a stiff shroud or finite-length insert. Poisson's ratio (Young's modulus) of the elastic material varies along the radial coordinate. The problem equations are reduced to integral equations with respect to contact pressures. A singular asymptotic method, which is fairly effective for contact regions of sufficiently large length, is applied to solve the problem.
I. A. Banshchikova
Lavrent'ev Institute for Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: конструкционные сплавы, разупрочнение, упрочнение, повреждаемость, рациональные режимы ползучести, растяжение, structural alloys, softening, hardening, damage, rational creep, tension
The kinetic equations of creep are used to compare damage accumulation in rods under tension in two forming modes: at constant stresses and at constant strain rates corresponding to strain rates in steady-state creep for the same stresses. It is found that from the point of view of increasing the residual service life at the production stage, forming to the required strain value with given kinematics is preferable to forming under the action of constant stresses for materials on whose strain-time charts for = const, the fracture strain decreases monotonically with increasing stress. Forming at constant stress is preferred for materials on whose strain-time charts for = const, the fracture strain increases monotonically with increasing stress. Calculation results for several alloys are presented.
G. M. Sevast'yanov, A. A. Burenin
Institute of Engineering and Metallurgy, Far East Branch, Russian Academy of Sciences, Komsomolsk-on-Amur, 681005, Russia
Keywords: кручение цилиндрических стержней, конечные деформации, упругопластическая задача, связанная термопластичность, температурное разупрочнение, адиабатические условия, несжимаемый материал Муни - Ривлина, условие Треска, эффект Пойнтинга, torsion of cylindrical rods, finite deformations, elastoplastic problem, related thermoplasticity, temperature softening, adiabatic conditions, Mooney-Rivlin incompressible material, Tresca condition, Poynting effect
In this paper, we study the torsion of an incompressible circular cylinder with fixed ends made of polymer material relative to the axis of symmetry taking into account adiabatic heating. The conservative deformation mechanism is determined by the elastic Mooney-Rivlin potential, and the dissipative deformation mechanism by the Tresca-Saint-Venant plastic potential. The problem is solved using multiplicative division of the total Almansi strain measure into elastic and plastic components. It is assumed that the local change in material temperature is due only to plastic dissipation. The thermal deformation of the material and hardening are neglected. The exact solution of the problem is obtained for an arbitrary dependence of the mechanical characteristics of the material on temperature. In particular, the axial force, the torque, and the temperature distribution in the sample as a function of increasing loading parameter are determined. The obtained solution is compared with the available experimental data.
The influence of hole diameter on the fracture of quasi-brittle geomaterial in the stress concentration zone under non-uniformly distributed compression has been studied theoretically and experimentally taking into account the size effect. The failure load is determined using modified nonlocal criteria which are the development of the average stress criterion, the point stress criterion, and the fictitious crack criterion, and which contain a complex parameter that characterizes the size of the fracture process zone and takes into account not only the material structure, but also the plastic properties of the material, the geometry of the sample, and its loading conditions. The calculation results are compared with experimental data.
A. S. Semenov
St. Petersburg Polytechnic University of Peter the Great, St. Petersburg, 195251, Russia
Keywords: поликристаллическая пьезокерамика, точечные дефекты, диссипация, гистерезис, поверхность переключения, непропорциональное нагружение, гомогенизация, моделирование, polycrystalline piezoceramics, point defects, dissipation, hysteresis, switching surface, nonproportional loading, homogenization, modeling
Constitutive equations are proposed that describe the nonlinear behavior of a polycrystalline ferroelectroelastic material and taking into account the dissipative nature of the movement of domain walls, the presence of point defects, and their effect on switching processes in the temperature range not accompanied by phase transitions. The method of two-level homogenization is used to describe the behavior of a polycrystalline ferroelectroelastic material at the macro level. Accounting for defects in the micromechanical model of ferroelectroelastic materials has significantly improved the predictive ability of the model under multiaxial loading. Comparison of the results of computations with experimental data on dielectric hysteresis curves and switching surfaces under nonproportional loading of polycrystalline piezoelectric ceramics PZT-4D, PZT-5H and BaTiO3 shows that the proposed model has good prediction accuracy.
V. V. Glagolev, L. V. Glagolev, A. A. Markin
Tula State University, Tula, 300600, Russia
Keywords: конечные деформации, сверхпластичность, идеальная пластичность, режим устойчивого деформирования, логарифмический модуль скоростного упрочнения, finite deformations, superplasticity, ideal plasticity, stable deformation, logarithmic module of fast hardening
Finite deformation of the panel under the influence of pressure is considered. The statement of the problem in displacements with equilibrium conditions represented via true stresses in Lagrangian coordinates is proposed. It is proven that the initial equations are satisfied when the panel is uniformly curved during deformation. The use of the previously proposed defining relation make it possible to determine a differential relationship between the laws of pressure and curvature with time at an arbitrary strain rate. Ideally plastic and superplastic deformations are considered. The dependences of pressure on the curvature and strain time are obtained at which superplasticity occurs. It is revealed that in this case that the range of stable changes in the curvature does not depend on the strain rate, and the threshold stress does not affect the time it takes to reach a given curvature of the panel.
