Yu. E. Voskoboinikov1,2
a:2:{s:4:"TYPE";s:4:"HTML";s:4:"TEXT";s:174:"1Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, Russia 2Novosibirsk State Technical University, Новосибирск, Россия";}
Keywords: wavelet filtering of images, threshold functions, wavelet filtering artifacts, ways to eliminate artifacts, nonlinear algorithms for spatial filtering
Wavelet filtering algorithms are widely used for image processing, and most of these algorithms are of a threshold nature: the wavelet expansion coefficient whose absolute value is smaller than a certain threshold value vanishes; otherwise the coefficient undergoes some (most often nonlinear) transformation, which is defined by the threshold function used. When high-contrast images are filtered, such processing of expansion coefficients can lead to the emergence of the so-called artifacts in the filtered image - in the vicinity of a jump-like change in the amplitude of the filtered image, there appear pulses that are absent in the original image, which significantly degrades the filtering quality. To eliminate such artifacts, several approaches are considered in the present paper, and a method is proposed, which implies post-processing of the results of wavelet filtering of images by nonlinear algorithms of spatial filtering. The computational experiment is performed, which makes it possible to conclude that the proposed method is an effective way to eliminate artifacts of wavelet filtering of high-contrast images.
A. V. Lapko1,2, V. A. Lapko1,2 1Institute of Computational Modelling SB RAS, Krasnoyarsk, Russia 2Reshetnev Siberian State University of Science and Technology, Krasnoyarsk, Russia
Keywords: kernel density estimation, fast optimization algorithm, bandwidth selection, antikurtosis coefficient, symmetric probability densities, second derivative of the probability density
A modification of the fast algorithm of bandwidth selection of kernel functions in nonparametric probability density estimation of the Rosenblatt - Parzen type is proposed. Fast algorithms for optimizing the kernel density estimates can significantly reduce the time costs when selecting their bandwidth, as compared to the traditional approach. This is especially true when processing large volumes of statistical data. The basis of the proposed method is the analysis of the formula for the optimal calculation of the bandwidths of kernel functions and the detected dependence between the nonlinear functional of the second derivative of the reconstructed probability density and the antikurtosis coefficient. The proposed algorithm for bandwidth selection provides reduction in the probability density approximation error as compared to the traditional approach. The conclusions from the study are confirmed by the results of computational experiments. Particular attention is paid to the dependence of these properties on the amount of initial information.
S. I. Vyatkin, B. S. Dolgovesov
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: reconstruction of three-dimensional objects, silhouette, stereo pair, depth map, octal tree, perturbation functions
A method for reconstructing functionally defined surfaces from stereo images of real objects is proposed. A well-known approach to calculating volume models based on images of silhouettes in the object space is used at the stage of preprocessing. A well-known area-based algorithm with correlation of image intensity levels is applied to calculate the depth map. In order to reconstruct a smooth surface with a compact description, a new method of transformation into a functionally defined model is proposed.
Y.V. Volkov
Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch, Russian Academy of Sciences, Tomsk, Russia
Keywords: signals analysis, mathematical model, surface temperature, climate classification, clustering, algorithm stability estimation
An algorithm for dynamic clustering of temperature signals, which is used to solve the problem of isolating climatic regions on the Earth surface characterized by a certain homogeneous (within the boundaries of the region) type of the climate is considered. A numerical experiment implemented to assess its stability is described. The reference signal model used in the numerical experiment is represented as a sum of harmonic components. The additive noise components are generated in the frequency domain. The parameters varied in the numerical experiment are the noise value and sample size. The estimates of the root-mean-square deviations and stability of the dynamic clustering algorithm are given.
S. S. Abdurakipov, E. B. Butakov
Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: machine learning, predictive maintenance, pre-failure and emergency conditions of engines
This study is aimed at a comparative analysis of the developed classical machine learning models based on linear models and decision trees, as well as modern algorithms of convolutional neural networks and a neural network autoencoder for solving the problem of predictive detection of pre-failure and emergency conditions of aircraft engines. The simulations are performed using a NASA dataset based on sensor data from aircraft engine life cycles. Several formulations of problems are considered: problems of binary and multi-class classification of normal, pre-failure, and emergency states of aircraft engines, a regression problem for predicting the exact number of operating cycles before the engine failure, and an unsupervised learning problem in which a neural network autoencoder is used to detect abnormal operating cycles of an aircraft engine. The resulting algorithms are combined into a programming framework, which can be useful for analyzing a wide range of predictive maintenance data.
A. L. Reznik, A. A. Soloviev, A. V. Torgov
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: pulse-point source, optimal search, localization accuracy
High-speed algorithms for detection and localization of randomly distributed pulse-point objects capable of generating instantaneous delta pulses at random times are investigated. The search is carried out using a receiving device (detector) that can freely move within the search interval and dynamically alter the scanning window size. In this study, a priori information on the distribution of the sought signal source is limited to single-mode functions with a stepwise probability distribution density, which ensures physical feasibility of the algorithms. The parameters of the optimal search are calculated depending on the a priori distribution density of the sought signal source and the required localization accuracy.
V. I. Guzhov, E. N. Denezhkin, S. P. Ilinykh, G. A. Pozdnyakov, D. S. Khaidukov
Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: digital holography, step-by-step phase shift method, holographic interferometry, mathematical hologram, Fresnel transform, laser, wavelength
A modification of the digital holographic interferometry method for determining the deformations of an object with a diffuse surface by comparing the complex wave fronts reflected from it in two different states is discussed. The difference between the proposed method and the classical methods of digital holography lies in the fact that digital holograms used for image reconstruction have complex values determined by the method of phase shifts (“complex” hologram), while the classic digital holograms have only real values. In addition, the reconstruction of digital holograms is performed with due allowance for inhomogeneity of the reference beam intensity, which increases the quality of reconstruction. For this purpose, a tunable neutral optical filter is introduced into the reference arm of the optical scheme of the interferometer. An experimental verification of the method is performed.
V. P. Yushchenko1, V. G. Edvabnik1, O. V. Hoffman2, T. V. Duluba3, V. N. Legkii1 1Novosibirsk State Technical University, Novosibirsk, Russia 2"Confadecor" LLC, Smolensk, Russia 3Saint-Gobain LLC, Moscow, Russia
Keywords: ring antenna array, ultrasound, monochromatic probing signal, image reconstruction, tomography
A method of objects image reconstruction in sections by means of a ring antenna array with space sounding by an ultrasonic monochromatic wave is proposed. The image reconstruction is carried out by scanning the internal structure of the object placed inside the ring controlled by the focus of the ring antenna array. A control algorithm for phase shifters in channels of elementary radiators of the ring antenna array for changing the focus position is described. Model results of image reconstruction of elementary point objects are presented. The problems of ring antenna array implementation are discussed.
Yu. V. Chugui1,2,3 1Technological Design Institute of Scientific Instrument Engineering, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia 3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: Fresnel and Fraunhofer diffraction, Fourier optics, spatial filtering, images and spectra of 3D objects, volumetric edge, 3D dimensional inspection
As applied to dimensional inspection of 3D objects, specific features of the formation images of a volumetric asymmetric absolutely absorbing edge, which is the main fragment of extended (in depth) plates of constant thickness, in the diffraction-limited projection system of images are analytically investigated. The structures and intensity profiles in images of the front and rear faces of the object are studied, respectively, with small and large apertures of the optical system for various relationships of the object bevel c , Fresnel zone size dd ~ ( l is the light wavelength and d is the object thickness), and angular aperture of the optical system . For the bevel , at a large depth of focus of the system, there is a shift in the intensity profile in the 3D edge images, which is proportional to the Fresnel zone and the bevel value. It is analytically shown that a clear image of either the front face (the rear face is in the shadow) or the rear face (the front face is shaded by the rear face) is observed in the plane conjugated with the front face in the case with large bevels ( ) and small apertures of the system. Formulas for the profile of rear face images are derived and investigated in the case of significant volumetric effects, where the depth of focus of the system is much smaller than the object thickness. The results of the calculations are in good agreement with the results of computer modeling.
M. S. Khairetdinov1, B. V. Poller2,3, B. D. Borisov2,3, A. V. Britvin2 1Institute of Computational Mathematics and Mathematical Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: acousto-optic interaction, infra-low frequencies, seismic vibrator, laser measuring line, optical stand, experimental research
The processes of acousto-optical interaction at infra-low frequencies are studied using seismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measuring lines as optical receivers of vibrations. The proposed types of the source and receiver for the purpose of studying acousto-optical interaction determine the novelty and originality of the proposed approach. The results of experiments on evaluating the characteristics of acousto-optical interaction at infra-low frequencies in problems of laser environmental monitoring are presented.
Yu. N. Zolotukhin, K. Yu. Kotov, A. A. Nesterov, E. D. Semenyuk
Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: object tracking, video stream, convolutional neural network, Kalman filter
In this paper, an algorithm for 6-coordinate moving object tracking on a sequence of RGB images based on a convolutional neural network is proposed. Network training is performed on the synthesized data of an object with a dynamic motion model. A Kalman filter is included into the feedback from the output to the input of the network to obtain a smoothed estimate of the object coordinates. Preliminary results of object tracking on synthesized images demonstrate the effectiveness of the proposed approach.
R.Yu. Pozhitkov
Institute of the problems of Northern development, Tyumen Scientific Centre SB RAS, Tyumen, Russia
Keywords: particulate matter, dust pollution, РМ, РМ, environmental monitoring, Tyumen
The content of particulate matter PM2.5 and PM10 in the surface air layer of the city of Tyumen in June 2020 is estimated. The measurements were made using a hand-held portable particle counter AIR TESTER CW-HAT 200. The content of PM2.5 and PM10 in the city air is not highly variable; their average values are several times less than the one-time maximum permissible concentrations. This allows us to conclude that the surface air in Tyumen is moderately polluted with suspended particles. With the help of ArcGIS 10.6.1 software, schemes of the distribution of particles over the city territory are constructed; two highly polluted regions are identified caused by high traffic and wind pattern, respectively. The correlations between the content and distribution of PM2.5 and PM10 with air temperature and relative humidity are analyzed.
A.A. Filei
Far-Eastern Center of State Research Center for Space Hydrometeorology "Planeta", Khabarovsk, Russia
Keywords: cloudiness, cloud top height, satellite data, brightness temperature, MSU-MR
A technique for determining the cloud top height from the MSU-MR measurements on-board the Russian meteorological satellite Meteor-M No. 2-2 is presented. It is based on measurements of the cloud radiation in the infrared atmospheric window at wavelengths of 11 and 12 m. The comparison between the cloud top heights estimated from MSU-MR data and CALIOP satellite lidar data shows their good agreement. A high correlation coefficient (0.94) and a low root-mean-square error (1.28 km) confirm the effectiveness of the technique suggested.
B.D. Belan, G.A. Ivlev, T.K. Sklyadneva
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: atmosphere, ultraviolet radiation, total ozone content, cloudiness, variations, albedo of the underlying surface
The relationship between variations in the values of surface ultraviolet radiation in the wavelength range 280-320 nm and the state of the underlying surface is analyzed. For this purpose, a homogeneous series of UV-B radiation data obtained at the TOR-station of IAO SB RAS from 2004 to 2016, satellite data on TOC, AOT data from AERONET network, and the data on total cloud cover from the meteorological site of IMCES SB RAS were used. It is shown that the contribution of the underlying surface albedo to increase in the UV-B radiation is 4-8% on average for TOC = 300-400 DU and 9-13% for TOC = 400-500 DU subject to stable snow and the solar zenith angle from 52° to 68°.
A.A. Sin'kevich1, V.B. Popov1, A.M. Abshaev2, B.A. Boe3, S.D. Pawar4, Yu.P. Mikhailovskii1, M.L. Toropova1, V. Gopalakrishnan4, Zh.M. Gekkieva5 1The Voeikov Main Geophysical Observatory, St Petersburg, Russia 2HSRC "Antigrad", Nalchik, Russia 3Weather Modification Inc International, 58102, Fargo, ND, 20th Street North, USA 4Indian Institute of Tropical Meteorology, 411008, Pashan, Pune, Maharashtra, Dr. Homi Bhabha Road, India 5Mountain Geophysical Institute, Nalchik, Russia
Keywords: thunder, radar, cumulonimbus
Radar characteristics of convective clouds during their transition to thunderstorm stage are considered for three regions of the world (India, North Caucasus, and north-west of Russia). Cu depth increases in all regions; the reflectivity and cloud volumes with high reflectivity increase in Russia. Changes in reflectivity in clouds in India are low.
T.B. Zhuravleva
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: radiation transfer, Monte Carlo method, optical anisotropy, horizontally oriented plates
An original algorithm for statistical of the solar radiation transfer in the presence of crystal clouds, optically anisotropic with respect to the zenith angle of the incident radiation, is presented. Examples of preliminary calculated local optical characteristics of clouds consisting of horizontally oriented plates (without taking into account internal absorption) are given. The software developed was tested in two numerical experiments. In the first of them, the results of calculations of reflected radiation for an isotropic medium with the use the previously developed algorithm for clouds consisting of chaotically oriented particles and the algorithm presented in this work were compared. In the second experiment the angular dependence of the upward radiation intensity and the phase scattering function in crystal clouds consisting of horizontally oriented plates is compared. The results of numerical experiments indicate that when simulating radiation transfer using this algorithm, the properties of the optical anisotropy of the medium are adequately taken into account.
O.N. Gaponenko
Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia
Keywords: applied optics, light absorption, light scattering, scattering phase function
The spatiotemporal light field of a point like isotropic source is calculated with the help of integral characteristics of scattering. This approach has an ample advantage since it does not require the scattering function to be known for all possible angles, especially for small angles, where the measurement for media with the strong forward scattering is very difficult.
I.M. Gubenko1, K.G. Rubinstein1,2 1Nuclear Safety Institute, Russian Academy of Sciences, Moscow, Russia 2Hydrometeorological Centre of Russia, Moscow, Russia
Keywords: thunderstorms, Moscow region, WRF-ARW, convection, electrification models, instability indices
Results of lightning activity forecast over the territory of the Moscow region for the period June 1 - August 31, 2017, are presented. The validation is made for forecasts based on the atmospheric instability indices, Cb electrification model, and WRF-ELEC module. The predictions of WRF-ARW model are used as input data. The indices Total Totals, SWEAT, CAPE, Iww, K (Whiting), and Peskov are studied. Estimation is performed using the Worldwide Lightning Location Network (WWLLN). The WWLLN data are preliminary compared with meteorological data.
E.A. Sosnin1,2, V.S. Kuznetsov1, V.A. Panarin1, V.S. Skakun1, V.F. Tarasenko1,2, G.A. Ivlev3, A.V. Kozlov3 1High Current Electronics Institute of the Siberian Branch of the RAS, Tomsk, Russia 2National Research Tomsk State University, Tomsk, Russia 3V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: apokamp discharge, blue jet, nitrogen oxides, transient light phenomena
Using of apokamp discharge carried out on a laboratory simulation of the process of formation of blue jets in the Middle atmosphere of the Earth. The developed setup allowed to compare the NOx concentration in the apokamp discharge mode and without it. In both cases, at an air pressure of 120 torr, close values of NO and NO2 were obtained, amounting to 7320 and 1220 ppb, respectively. The data obtained in a laboratory experiment indicate that blue jets do not significantly affect the concentration of nitrogen oxides.
M.V. Trigub1, N.A. Vasnev1, V.D. Kitler2, G.S. Evtushenko1,3 1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia 2Tomskiy Nauchnyy Tsentr SO Ran, Tomsk, Russia 3Scientific Research Institute - Federal Research Centre for Projects Evaluation and Consulting Services, Moscow, Russia
Keywords: high-speed imaging, active filtration, laser monitor, Ni-Al, synthesis of materials, DC arc, burning
The paper presents the results of using a laser monitor with an independent illumination source (bistatic laser monitor) to image the processes blocked from an observer by the background light. The maximum shooting speed was 15-103 fps. The possibility to observe the structural transformations in a combustion wave of self-propagating high-temperature synthesis is shown. It is shown that a bistatic laser monitor allows one to significantly improve the image quality (contrast, brightness) of low-contrast objects.
E.S. Savelieva, V.V. Zuev
Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: polar vortex, Arctic sea ice, Beaufort Sea, Canadian Arctic Archipelago, planetary waves
The Arctic stratospheric polar vortex usually forms in autumn, reaches its peak intensity in mid-winter, and decays in spring. The polar vortex strength and persistence in the winter-spring period play an important role in stratospheric ozone depletion with the return of solar radiation in late winter. In this study, we investigated the causes of the unusual weakening of the Arctic stratospheric polar vortex in winters 1984/1985, 1998/1999, and 2012/2013. The unusually early (from late December to early January) splitting of the Arctic polar vortex in those years was observed in mid-winter, after which the polar vortex did not recover for at least a month or until next autumn. We showed that such vortex dynamics was caused by an unusually prolonged increase in the activity of vertically propagating planetary waves for more than two weeks in the first half of winter in the lower stratosphere as a result of a record decrease in sea ice area and a corresponding increase in surface temperature in those years in the Beaufort Sea, the Canadian Arctic Archipelago, and the Central Arctic in November.
O. G. Sin'kova, V. P. Statsenko, Yu. V. Yanilkin
All-Russian Scientific Research Institute of Experimental Physics (VNIIEF), Sarov, Russia
Keywords: shock wave, Rayleigh - Taylor instability, contact boundary, three-dimensional modeling, turbulent mixing, (k-e) model
This paper describes the formulation and calculation results pertaining to the Euler gas aerodynamic complex (EGAC) method of interaction between a shock wave and a turbulent mixing zone, which develops on a flat contact boundary separating air and argon. The study is carried out using both direct numerical three-dimensional modeling and a two-dimensional ( k -e) turbulence model. A comparison is made with the results of experiments in which the expansion and stratification of a shock wave is observed during its propagation after passing through a turbulent mixing zone. Calculations are carried out using the ( k -e) model and with account for the presence of a boundary layer, which make it possible to explain this effect.
A. V. Proskurin
Altai State Technical University, Barnaul, Russia
Keywords: magnetohydrodynamics, flow stability, electrically conductive viscous fluid, differential sweep method
A system of equations of magnetohydrodynamics for an incompressible fluid is used to study flow stability between coaxial cylinders, which arises under the action of a longitudinal pressure gradient, in the case where a uniform magnetic field is directed along the cylinder axis. The differential sweep method is applied to investigate the dependences of the critical Reynolds numbers on the value of electrical conductivity and the strength of the external magnetic field. The existence of two ranges of electrical conductivity values is established, in which the stabilizing effect of the magnetic field is most significant. An abrupt increase in the critical Reynolds numbers and the detachment of closed instability regions from neutral curves are revealed.
A. Sh. Ramazanov, N. V. Bezrukov
Bashkir State University, Ufa, Russia
Keywords: temperature, pressure, filtration, constant depression, barothermal effect
A mathematical model of the unsteady temperature field of an oil reservoir after well start-up at a constant bottom-hole pressure is described taking into account the throttling and adiabatic effects. Two approximate solutions are considered and compared with the results of calculations of the thermal field using Ansys numerical simulator.
M. Kh. Khairullin1, E. R. Badertdinova2, R. M. Khairullin2 1Institute of Mechanics and Mechanical Engineering, Kazan Scientific Center, Russian Academy of Sciences, Kazan, Russia 2Kazan National Research Technological University, Kazan, Russia
Keywords: horizontal well, regularization, thermohydrodynamic studies, changes in pressure and temperature
A mathematical model describing thermohydrodynamic processes in an oil reservoir penetrated by a horizontal well has been developed. An inverse problem for estimating the filtration parameters of an oil reservoir is formulated. Temperature and pressure dependences obtained simultaneously using several autonomous downhole instruments placed in different sections of a horizontal wellbore are used as initial information. It is shown that the solution of the inverse problem based on numerical simulation and regularization methods can be used to construct inflow profiles along horizontal wellbores and estimate the reservoir properties of bottomhole and remote zones of the reservoir and the radii of bottomhole zones near downhole instruments.
A. I. Fedyushkin
Ishlinsky Institute for Problems in Mechanics, Moscow, Russia
Keywords: natural ventilation, numerical simulation, aeration lamps, Throughput
The aerodynamic characteristics of various models of aeration ridge ventilation windows are analyzed by numerical simulation. The most effective designs of ridge ventilation windows from the point of view of the lowest aerodynamic resistance of a lantern are found.
A forced convective heat transfer problem inside a micropipe as well as inside a microchannel with parallel walls in the laminar gaseous slip flow regime, a with finite heating region and a prescribed wall heat flux, including the axial heat conduction effect, is analytically investigated. The temperature field and Nusselt number are derived under the assumption that the flow is hydrodynamically fully developed in the finite-length heating region. The solution is found by applying the functional analysis method, by decomposing the energy equation into a pair of first-order partial differential equations. The first-order slip boundary conditions are imposed at the gas-wall interface. The analytical solution is compared with available calculations. The results show that the thermal characteristics in the heating region are significantly affected by the axial heat conduction, rarefaction effects, and finite length of the heating region.
J. Dutta1,2, B. Kundu1 1Department of Mechanical Engineering, Jadavpur University, Kolkata, India 2Department of Mechanical Engineering, MCKV Institute of Engineering, Howrah, India
Keywords: three-dimensional problem, analytical solution, bioheat, regional hyperthermia, dual-phase-lag
This article addresses the formulation of an exact analytical solution of a three-dimensional dual-phase-lag bioheat model in relation to living tissues of human organs subjected to regional hyperthermia treatment. The solution methodology is employed as a finite integral transform in combination with a filtered approach. A renovated initial condition with appropriate boundary conditions is imposed in the present modelling. Isotherms in different cross sections of the physical domain are generated and discussed with different thermal and geometric variables for establishing the exact temperature field. The present research output is compared with the published experimental work. The results show the necessity of a 3D analysis for an accurate prediction of the temperature response in tumour cells.
M. A. Ilgamov, M. M. Shakiryanov
Mavlyutov Institute of Mechanics, Ufa Federal Research Center RAS, Ufa, Russia
Keywords: pipeline, variable pressure, forced and parametric vibrations, interaction
The bending vibrations of a pipeline under the influence of the variable pressure of the transported fluid and the vertical vibrational motion of the supports are studied. The first mode of vibration is considered. Nonlinear forced parametric vibrations and their interaction are studied. The results of approximate analytical and numerical solutions are compared.
V. Yu. Kirpichnikov1, A. P. Koshcheev1, A. I. Syatkovskii2 1Krylov State Scientific Center, St. Petersburg, Russia 2Plastpolymer company, St. Petersburg, Russia
Keywords: vibration damping, vibration excitation, constraining coatings, resonant frequencies, viscoelastic laye
This paper presents the results of an experimental study of the efficiency of constrained vibrodamping coatings comprising a thin polymer layer with a very high damping capacity and thin constraining layers of various thickness. Vibration analysis of steel plates with and without a coating on the plate surface was performed. It has been shown that the application of the studied coating significantly reduces the vibration and sound generation in plate elements of structures.
S. Yan, Sh. Yan, J. Tang, X. Wang
School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, China
Keywords: graphene, cement, well cementation, elasticity modulus, compressive strength
Graphene has a high tensile strength and ductility; it is an ideal choice of cementing reinforcement materials. The effect of graphene on the well cementation properties of the cement slurry and on the mechanical properties of the set cement is investigated by adding 0.02 wt.% of graphene to the cement slurry system. Addition of graphene reduces the slurry viscosity and exerts a minor effect on the filtration and thickening time of the cement slurry. A triaxial mechanical test shows that the elasticity modulus of cement with graphene addition increases from 5087.6 to 6983.2 MPa, the compressive strength increases by 60.98%, and the strain recovery ability of the cured cement is improved. The structural analysis of the set cement by means of scanning electron microscopy shows that the silicate crystals of the set cement with graphene are more regular, and there are only few inner pores in the set cement. Therefore, graphene offers broad application prospects of improving cementing quality.
A. A. Adamov
Institute of Continuum Mechanics, Branch of the Perm Federal Research Center, Ural Branch, Russian Academy of Sciences, Perm, Russia
Keywords: theory of elasticity for an isotropic body with different moduli in tension and compression, test technique, tension-compression, coal plastic, graphite, ultra-high molecular weight polyethylene
We examine a range of issues related to the methodological and experimental support of a linear elastic model for an isotropic body with different moduli in tension and compression in mechanical tests of solid samples of different origin and structure. The reasons for the difference between tensile and compressive Young's moduli measured in the tests are analyzed. It is shown that using appropriate test techniques and equipment for measuring and recording deformations sustained by a homogeneous uniaxial state makes it possible to obtain statistically insignificant differences in Young's modulus for a number of materials subjected to tensile and compressive forces.
A. M. Gaifullin, K. G. Khairullin
Central Aerohydrodynamic Institute, Zhukovskiy, Russia
Keywords: transonic buffeting, numerical simulation, aerodynamics, flow control
This paper presents numerical simulation results for controlling a transonic boundary layer on a supercritical wing profile of a civil aircraft using a moving section of the profile surface. The efficiency of control in the case of transonic buffeting is shown.
D. Mukherjee, B. Sahoo
National Institute of Technology Rourkela, Rourkela, India
Keywords: Kármán swirling flow, Coriolis force, Chebyshev spectral method, radial stretching, convective instability
This paper deals with a laminar swirling flow of a viscous fluid over a stretchable rotating disk. The classical flow over a solid disk is known as the Kármán flow problem. For the first time in the literature, the combined effects of both the Coriolis force and radial stretching on the stability of the Kármán swirling flow has been carried out. The numerical investigation has been performed by using the Chebyshev spectral method. It is discovered that surface stretching produces a destabilising effect on the Kármán flow.
G. E. Ozoigbo1, A. M. Ette2 1Alex Ekwueme Federal University NDUFU Alike, IKWO, Nigeria 2Federal University of Technology, Owerri, Nigeria
Keywords: perturbation, static pre-loading, viscous damping, cubic model, step load
In this paper, we embark on analytical determination of the dynamic buckling of a statically pre-loaded elastic structure subjected to step loading. We first employ a two-timing regular perturbation procedure for asymptotic determination of a uniformly valid expansion of the displacement. The dynamic buckling load is determined nontrivially and is related to the corresponding static load. The dynamic buckling load is studied as a function of various problem parameters: degree of damping, initial imperfection, and static pre-loading.
The behavior of the 6008 aluminum alloy under impact loading with different strain rates is experimentally studied. Quasi-static compressive stress-strain curves of these materials areobtained in this study by using an RPL100 materials-testing machine and a split Hopkinson pressure bar. As the strain rate increases, the yield stress and the peak stress of the materials are found to increase significantly. The adiabatic temperature rise generated during the impact process makes the materials soften, so that the rate of the increase in the flow stress gradually decreases with an increase in the strain rate. Based on the dislocation dynamics theory, a viscoplastic dynamic constitutive model for the 6008 aluminum alloy is constructed. The model accurately describes and predicts the mechanical behavior of this material under impact compression at room temperature.
W. Fan1,2, N. Zhou3, Q. Jiao1, J. Shi4, K. Tang5 1State Key Laboratory of Explosion Science and Technology, School of Mechatronical Engineering, Beijing Institute of Technology, Beijing, China 2Institute of Forensic Science Ministry of Public Security of PRC, Beijing, China 3Department of Criminal Science and Technology, Nanjing Forest Police College, Nanjing, China 4Lanpec Technologies Co. LTD, Lanzhou, China 5National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing, China
Keywords: improvised explosive device, natural fragment, explosive characteristic, damage mode, scene reconstruction
To study the explosive characteristics of improvised explosive devices (IEDs), the damage mode of cylindrical IEDs and the formation mechanism of natural fragments under blast loading are investigated by using the ANSYS/AUTODYN 3D finite element code with Mott's stochastic failure model, as well as experiments of the hydraulic burst test and explosion test. The influence of the explosive charge amount and its position is also discussed. The main damage mode of the pressure container is the shearing damage, which is obviously affected by the explosive charge amount, charge position, and its power. The ability of the instantaneous function (pressurization rate) of the self-made explosive is far smaller than that of the standard explosive. Under the action of the self-made explosive, the closer to the detonation point, the smaller the size of the fragments formed.
J. Zheng1, Ya. Hu2 1Center for Hypergravity Experimental and Interdisciplinary Research, Zhejiang University, Hangzhou, China 2College of Computer Science and Technology, Zhejiang University of Technology, Hangzhou, China
Keywords: thick-walled spherical vessel, burst pressure, plastic orthotropy, plastic collapse
Based on Hill's anisotropic theory, theoretical solutions for the burst pressure and the corresponding equivalent stresses and strains for a thick-walled spherical pressure vessel made of a ductile material with plastic orthotropy are obtained. The effects of the plastic orthotropy, strain hardening, ratio of the external to internal radius of the vessel, and external pressure on the burst pressure is considered. It is found that the external pressure affects the burst pressure, while the corresponding equivalent stresses and strains have nothing to do with the external pressure.
A. E. Chesnokov1, A. V. Smirnov1, I. S. Batraev2, T. M. Vidyuk1 1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia 2Lavrentyev Institute of Hydrodynamics, Novosibirsk, Russia
Keywords: detonation spraying, copper coatings, high-energy planetary mill, microhardness, coherent scattering region, X-ray phase analysis
Copper powder spraying is under study: the PMS-1 original copper, the copper that is mechanically treated in a high-energy planetary mill, and the copper that is also spheroidized in a plasma jet. High-density copper coatings are obtained using a CCDS2000 detonation complex. The microhardness of coatings HV0.1, obtained from original and mechanically treated copper powders, increases from 110 to 160 and from 150 to 185, respectively, and the microhardness of coatings from the spheroidized powder is HV0.1=165. An X-ray phase analysis is carried out, and the resulting data indicate that, during the spraying, the copper oxide is partially reduced.
