Volume 88, №2
ONE-DIMENSIONAL PLANE MONOCHROMATIC FILTRATION WAVES
Equations and relations to describe one-dimensional plane monochromatic fi ltration waves in a homogeneous isotropic porous medium have been obtained. To this end, use was made of the equation of motion of a liquid phase with account of frictional forces, which in the case of steady-state fi ltration with parallel streamlines agrees with Darcy′s filtration law for an anisotropic medium. The equations of motion and continuity reduced to an equation of telegraphy enabled us to construct relations for the wave number, the absorption and attenuation coeffi cients, and the velocity of fi ltration waves. The expression for the phase velocity, the absorption coeffi cient, and the wave number of fi ltration waves has made it possible to investigate the correlation between this velocity and the velocity of elastic acoustic waves and the dependence on frequency. The extended theory of fi ltration-wave pressure fi elds refi nes the ideas of propagation of monochromatic fi ltration wave disturbances in a porous medium and confi rms the substantial decrease in the velocity in the low-frequency region compared to the velocity of propagation of elastic waves.
Author: A. I. Filippov and O. V. Akhmetova
Keywords: porous medium, filtration waves, attenuation coeffi cient, piezoconductivity coefficient
SOME CHARACTERISTIC FEATURES OF UNSATURATED SWELLING POROUS MEDIA DEFORMATION
The behavior of unsaturated swelling porous media under load is investigated. An equation for unsaturated fi ltration in swelling porous media and an equation relating the volume deformation of the medium to the magnitude of applied load have been obtained. The results of calculations by these equations are compared with corresponding experimental data
Author: N. E. Galiullina and M. G. Khramchenkov
Keywords: swelling porous medium, soil-ground, unsaturated filtration
SIMULATION OF ANOMALOUS OIL FILTRATION IN A POROUS BED
The problems of modeling the processes of filtration of anomalous structurized oils with coagulation structures present in a porous bed are considered. An equation for the fi ltration of Bingham fluids in a carrier bed that accounts for the dependence of the fi ltration rate on the pressure gradient and shear stress has been derived. Models for calculating the effective viscosity and mobility of oil depending on the change of the pressure gradient in the bed and of the concentration of particles in it have been developed. A comparison of these models with the experimental data available in the literature for various wells yielded satisfactory results.
Author: G. I. Kelbaliev, Ab. G. Rzaev, S. R. Rasulov, and L. V. Guseinova
Keywords: fi ltration, anomalous oil, Bingham fluid, coagulation structure, carried bed
ON THE DYNAMICS OF A HEAT-RELEASING GRANULAR BED
Within the framework of a two-temperature model, numerical simulation of the dynamics of cooling a heatreleasing granular bed by a gas with account for the temperature dependence of gas viscosity has been carried out. Generalized dependences are obtained for calculating the time needed to establish a stationary state and the maximum temperature of particles.
Author: Yu. S. Teplitskii and A. R. Roslik
Keywords: heat-releasing granular bed, dynamics, fi ltration cooling, two-temperature model, maximum temperature of particles, stabilization time
THEORETICAL INVESTIGATION OF THE PROCESS OF STEAM–OXYGEN GASIFICATION OF COKE–ASH PARTICLES IN A FLUIDIZED BED UNDER PRESSURE
The problem on the evolution of the state of an ensemble of reacting coke–ash particles in a fl uidized-bed gas generator is considered. A kinetic equation for the distribution function of particles within small ranges of carbon concentration variation for the stages of surface and bulk reaction has been constructed and integrated. Boundary conditions ("matching" conditions) at the boundaries between these ranges are formulated. The infl uence of the granulometric composition of the starting coal, height, porosity, and of the bed temperature on the process of steam– oxygen gasifi cation of coke–ash particles of individual sorts of fuel and of a binary coal mixture has been investigated.
Author: B. B. Rokhman
Keywords: steam–oxygen gasifi cation, coal, binary mixture, generator gas, particles, polydispersity, temperature, heterogeneous and homogeneous reactions, distribution function, bubbling bed
MATHEMATICAL SIMULATION OF THE STRESSED-STRAINED STATE OF THE FOUNDATION OF EARTH DAMS WITH AN OPEN SURFACE UNDER THE INFLUENCE OF HEAT AND MASS TRANSFER IN THE TWO-DIMENSIONAL CASE
his paper considers the problem of mathematical simulation of the stressed-strained state of the foundation of the earth dam with account for the heat and mass transfer in the presence of a free surface of ground waters. We have obtained a numerical solution of the corresponding boundary-value problem in the two-dimensional case in the inverse formulation with the use of a computational algorithm based on numerical conformal mapping of the composition domain with a curved boundary and the fi nite difference method.
Author: A. P. Vlasyuk and N. A. Zhukovskaya
Keywords: boundary-value problem, stressed-strained state, heat and mass transfer, earth dam, free surface, conformal mapping, finite difference method.
DEPOSITION OF HEAVY PARTICLES FROM A SPHERICAL CLOUD ON THE EARTH′S SURFACE. ANALYTICAL SOLUTION
Analytical solutions of the problems on deposition of particles from a spherical cloud on the earth′s surface have been obtained for two cases: the wind velocity in the ground layer of the atmosphere is invariable with height and the wind velocity follows a linear law. Analytical formulas have been suggested for calculating the surface concentration of deposited particles with an arbitrary function of their size distribution, as well as the geometrical parameters of the deposition region.
Author: K. O. Sabdenov and G. T. Zholdybaeva
Keywords: deposition of particles, surface density of deposited particles, turbulent diffusion, dangerous zone
FORMATION OF A COMPOSITE BASED ON POLYURETHANE WITH CARBON NANOTUBES AND SHUNGITE
hysicomechanical and electrophysical characteristics of a polyurethane composite doped with carbon-containing materials have been investigated. It has been found that the roughness of the sample’s surface and also the porosity increase with the concentration of the dopant. Volt-ampere characteristics of composite materials point to the activated type of conductivity in these materials; however, at a temperature of nearly 340 K, the type of conductivity is changed. Also, the frequency dependence of the conductivity has been established.
Author: F. F. Komarov, R. M. Krivosheev, M. A. Ksenofontov, T. Koltunovich, Kh. A. Abdullin, L. E. Ostrovskaya, and A. K. Togambaeva
Keywords: carbon nanomaterials, carbon nanotubes, polymers, electrophysical properties
INFLUENCE OF CONDITIONS EMPLOYED IN APPLICATION OF Ti–Zr–Si–N NANOSTRUCTURED COATINGS ON THEIR COMPOSITION, STRUCTURE, AND TRIBOMECHANICAL PROPERTIES
Nanostructured coatings of thickness from 1.5 to 2 μm are applied to Ar+ ions-prepurifi ed stainless steel substrates by means of reactive magnetron sputtering of composite targets with the content of Ti–Zr–Si components 56, 36, 8 at.% and 36, 56, 8 at.%, respectively. Using the methods of Rutherford back scattering and transmission electron microscopy, we studied the structure of the coatings obtained, their phase composition, and the distribution of components over the depth of coatings. The microhardness of coatings was measured and their basic tribomechanical characteristics were investigated. The dependence of the composition and properties of coatings on the conditions of their application has been examined. The optimum regimes of application of coatings with high tribomechanical properties that ensure microhardness of coating of 31 GPa and double decrease in the friction coeffi cient have been determined.
Author: F. F. Komarov, V. V. Pil′ko, and I. M. Klimovich
Keywords: friction, wear, coating, magnetron sputtering
PARAMETRIC INVESTIGATION OF THE KINETICS OF GROWTH OF CARBON-NANOTUBE ARRAYS ON IRON NANOPARTICLES IN THE PROCESS OF CHEMICAL VAPOR DEPOSITION OF HYDROCARBONS
On the basis of the kinetic model of synthesis of carbon nanotubes on iron nanoparticles in the process of chemical vapor deposition of hydrocarbons, the parametric dependences of characteristics of arrays of vertically oriented nanotubes on the temperature of their synthesis, the concentration of acetylene in a reactor, and the diameter of the catalyst nanoparticles were investigated. It is shown that the maximum on the temperature dependence of the rate of growth of carbon nanotubes, detected in experiments at a temperature of ~700oC is due to the competing processes of increasing the catalytic activity of iron nanoparticles and decreasing the acetylene concentration because of the signifi cant gas-phase decomposition of acetylene in the reactor before it enters the substrate with the catalyst. Our calculations have shown that the indicated maximum arises near the transition point separating the low-temperature region where multiwall nanotubes are predominantly synthesized from the higher-temperature region of generation of single-wall nanotubes in the process of chemical vapor deposition of hydrocarbons.
Author: S. I. Futko, B. G. Shulitski, V. A. Labunov, and E. M. Ermolaeva
Keywords: carbon nanotubes, chemical vapor deposition, array of carbon nanotubes, iron nanoparticles, heterogeneous catalysis, transition metals, hydrocarbons
REDUCTION OF 137Cs EMISSION INTO THE ATMOSPHERE ON COMBUSTION OF A RADIONUCLIDE-CONTAMINATED SOLID FUEL UNDER CONDITIONS INVOLVING EXCITATION OF THERMOACOUSTIC SELF-OSCILLATIONS AND GAS-DYNAMICAL PULSATIONS
The emission of radioactive 137Cs with flue gases in various regimes of combustion of radionuclide-contaminated solid fuels in a wide temperature interval has been investigated. The fl ame temperature decreased on the onset of vibrating combustion. A lowering in the 137Cs emission under conditions of vibrating and intermittent combustion in comparison with the emission under conditions of diffusion combustion has been obtained.
Author: Yu. V. Polezhaev, V. D. Geshele, O. G. Stonik, I. P. Raskatov, V. N. Solov′ev, I. G. Pleshchankov, L. A. Bida, A. S. Levchuk, and G. I. Fokina
Keywords: vibrating combustion, Rijke tube, solid fuel, emission, radionuclides, thermoacoustic self-oscillations
OPTIMUM DISTRIBUTION OF METAL PARTICLES IN THE SOLID-PROPELLANT CHARGE IN THE APPROXIMATION OF A ONE-DIMENSIONAL FLOW FIELD IN A CYLINDRICAL CHANNEL
A study has been made of ways of optimum distribution of particles of dispersed metal in the solid-propellant charge with a cylindrical central channel, which is firmly fastened to the case. The efficiency of combustion of this metal has been analyzed. Consideration has been given to the influence of the dynamic nonequilibrium of two-phase flow on the optimum distribution of metal particles in the indicated charge in the approximation of one-dimensionality of the flow field.
Author: L. L. Min′kov and É. R. Shrager
Keywords: solid-propellant charge, dispersed metal, combustion efficiency
INFLUENCE OF THE FERMENTATION OF PINEAPPLE WASTES WITH THE USE OF METHANOBACTERIUM STRAINS SEPARATED IN VIETNAM ON THE PRODUCTION OF BIOGAS FROM THEM
When pineapples are processed, the wastes obtained comprise 30–50% of the raw-material weight. These wastes contain sugar, albumins, lipids, and vitamins that decompose under the action of microorganisms existing in nature and, in so doing, pollute the environment. The use of wastes in plants operating on biogas makes it possible to obtain great economic benefi ts. It was established that the best conditions for the obtaining biogas from pineapple wastes are realized in the case where Methanobacterium strains are used for increasing the rate of fermentation of these wastes and the wastes have a temperature of 35–45o C, a pH index of 7–7.5 at the initial stage of their fermentation, and a C/N ratio of 30/1. Under these conditions, the MT3, MT5, and MT7 strains of Methanobacterium yield the maximum amounts of biogases containing, respectively, 57.4% of CH4 and 36.1% of CO2, 57.2% of CH4 and 36.3% of CO2, and 57.4% of CH4 and 36.2% of CO2
Author: Nguyen Thuy Nga and Nguyen The Trang
Keywords: biogas, pineapple waste, Bacillus, Streptomyces, Methanobacterium
DETERMINATION OF THE DYNAMIC STRESSES IN AN INFINITE PLATE ON THE BASIS OF AN EXACT ANALYTICAL SOLUTION OF THE HYPERBOLIC HEAT-CONDUCTION EQUATION FOR IT
With the use of an exact analytical solution of the classical hyperbolic heat-conduction equation, derived on the basis of the Maxwell–Cattaneo–Luikov relaxation formula, an exact analytical solution of the problem on the dynamic thermoelasticity of an infi nite plate was obtained for the case where the outer surfaces of this plate are free of mechanical loads. It is shown that the undamped thermoelastic stresses in this plate vary spasmodically in time with periodic change in their sign. The stress jumps arising near the opposite outer surfaces of the indicated plate move along the spatial variable to its center where they superimpose, with the result that the dynamic thermal stresses in the plate double.
Author: I. V. Kudinov and V. A. Kudinov
Keywords: dynamic thermoelasticity, hyperbolic heat-conduction equation, stress jump, undamped thermoelastic stress waves, relaxation coefficient
MATHEMATICAL SIMULATION OF THE LOCALLY NONEQUILIBRIUM HEAT TRANSFER IN A BODY WITH ACCOUNT FOR ITS NONLOCALITY IN SPACE AND TIME
Differential equations for the locally nonequilibrium heat transfer in an infi nite plate, in which the nonlocality of this plate in space and time is taken into account, have been derived. Exact analytical solutions of these equations were obtained and analyzed in detail. This analysis has shown that, in the case where the nonlocality of the plate in space and time is taken into account in the indicated equations, they do not give abrupt changes in the temperature of the plate and negative temperatures for it. It was established that, in locally nonequilibrium processes, the fi rst-kind boundary conditions (a heat shock) cannot be realized instantaneously at any conditions of heat exchange between a body and the environment and that, consequently, in the process of this exchange, the coeffi cient of heat transfer cannot exceed any limiting values determined by the physical properties (including the relaxation ones) of the body
Author: I. V. Kudinov and V. A. Kudinov
Keywords: locally nonequilibrium heat exchange, space and time nonlocality, relaxation coeffi cient, heat fl ow, temperature gradient.
WEIGHTED TEMPERATURE IDENTITIES
It has been shown that the differential heat conduction equation together with the boundary conditions can be recast as a sequence consisting of integral identities for the weighted temperature. Weight functions take into account the properties of the heat conduction equation and the boundary conditions. The sequence of identities was constructed on the basis of multiple differentiation or integration operators. Using the search for eigenvalues of the boundary value problem as an example, we have demonstrated the high effi ciency of such systems.
Author: V. A. Kot
Keywords: heat conduction equation, weight function, approximate method, integral identities, eigenvalues
COMPUTATIONAL ANALYSIS OF THE THERMAL STATE OF METAL LOAD-CARRYING STRUCTURES OF A STADIUM FOR VARIOUS FIRE SCENARIOS
This paper considers a numerical model and a method of its construction and verifi cation, as well as the results of calculations of the distribution of nonstationary temperatures of structures with the example of analysis of the thermal state of complex load-carrying metal elements of awnings over the stands of the ″Olimpiiskii″stadium (Kiev) under the conditions of three scenarios of possible fi res. We have estimated the fi re-resistance of these structures using the fi eld method (CFD technology) realized with the aid of ANSYS FLUENT and FDS computer programs.
Author: I. V. Chalaya and P. G. Krukovskii
Keywords: metal structures, thermal state, fire conditions, fire-resistance, modeling
ANALYSIS OF THE POSSIBILITIES OF PROVIDING HIGH-QUALITY MECHANIZED SOLDERING
We have analyzed the possibilities of optimizing the technological processes of convection, wave, and laser soldering by comparing experimental data with the results of mathematical modeling
Author: V. N. Shtennikov
Keywords: convection, wave, and laser soldering, soldered joint, printed circuit.
VISUALIZATION OF A FLOW IN A SPHERICAL DIMPLE BUILT IN THE LOWER WALL OF THE RECTANGULAR-SECTION CHANNEL OF A WATER TUNNEL AND NUMERICAL IDENTIFICATION OF THE VORTEX-JET STRUCTURES IN IT
Numerical and physical simulations of a laminar separation flow over a single spherical dimple built in the lower wall of the rectangular-section plane-parallel channel of a water tunnel were performed on the basis of the multiblock computational technologies realized in the VP2/3 package. The vortex mechanism of intensifi cation of the heattransfer processes in this dimple was analyzed with special emphasis on the identifi cation of the vortex-jet structures self-generated in it.
Author: S. A. Isaev, A. S. Guzeev, S. Z. Sapozhnikov, V. Yu. Mityakov, and A. V. Mityakov
Keywords: separation fl ow, spherical dimple, plane-parallel channel, hydraulic losses, heat exchange, water tunnel, procedure of pressure correction, Rhie–Chow approach, multiblock computational technologies, VP2/3 package, visualization
INVESTIGATION OF THE AERODYNAMIC DRAG OF AN EIGHT-CHANNEL CENTRIFUGAL FILTER
The aerodynamic characteristics and the structure of vortices of the central region of the channel system of an eightchannel centrifugal fi lter have been investigated. An overview of the foreign and home literature on the fi ltration of solid particles in the gas fl ow in centrifugal apparatuses is given [1, 2]. We present the design and the principle of operation of the eight-channel centrifugal fi lter based on a system of curvilinear channels with equal turn angles and equal cross-sectional areas connected in series. We have performed numerical calculations of the dependence of the aerodynamic drag of the centrifugal fi lter on the rate of fl ow obtained by three different methods: analytical calculation, experiments on the laboratory facility, and with the help of modern means of computer modeling. Computational modeling of the fl ow was carried out by solving Reynolds (RANS, Reynolds-averaged Navier–Stokes) equations by the SFD method with the use of a k–ε model of turbulence for three modes of operation of the apparatus. The results of computer modeling permitted visualizing the vortex structure of the central region of the separation chamber in the form of 3D graphs. The obtained results have been confi rmed experimentally on a laboratory model of the centrifugal filter of capacity up to 200 m3/h of purifi ed air.
Author: D. A. Serebryanskii, N. S. Semenyuk, and S. V. Plashikhin
Keywords: centrifugal fi lter, aerodynamic drag, pressure drop, modeling, channel system
MODELING NONSTATIONARY NONLINEAR-VISCOUS LIQUID FLOWS THROUGH A PIPELINE
The process of nonstationary incompressible nonlinear-viscous liquid flow through a pipeline is considered. It is described by a parabolic-type one-dimensional nonlinear equation. The problem of determining the dependence of the pressure difference on time from the assigned volumetric flow rate in the given pipeline is formulated. Such a problem pertains to the class of inverse problems connected with the restoration of the dependence of the right-hand sides of parabolic equations on time. A computational algorithm for solving the problem has been suggested.
Author: Kh. M. Gamzaev
Keywords: pipeline transportation, nonlinear-viscous fl uid, pressure difference, inverse problem
NUMERICAL METHOD OF SOLUTION OF THE COEFFICIENT-INVERSE PROBLEM FOR UNSTEADY MOTION IN AN OIL PIPELINE
Consideration is given to the approach to identifi cation of the coeffi cient of hydraulic resistance of a linear portion of a main pipeline in transporting raw hydrocarbons. The problem of identifi cation is reduced to a class of fi nitedimensional-optimization problems. To solve them, the author proposes effi cient numerical methods of fi nitedimensional optimization of fi rst order. For this purpose, in the work, the author derives formulas for the components of the gradient of the target functional in the space of identifi ed parameters. The obtained values of the optimized vector can be used for construction of the identifi ed function from any class of functions with interpolation and approximation methods. Results of the conducted numerical experiments are given.
Author: S. Z. Kuliev
Keywords: distributed system, coefficient of hydraulic resistance, inverse problem, identifi cation problem, conjugate problem, functional gradient
FLOW PAST THE SAIL BLADE OF A WIND TURBINE
An experiment to determine the aerodynamic characteristics of a wind turbine with sail blades was conducted on a model. The dependence of the drag and lift coefficients on the dimensionless angle of attack and the number of windturbine blades has been determined experimentally
Author: K. Kusaiynov, Zh. T. Kambarova, N. K. Tanasheva, K. M. Shaimerdenova, and A. R. Alibekova
Keywords: wind turbine, sail, lift coeffi cient, drag coeffi cient, air fl ow, angle of attack, Reynolds number
OPTIMUM GASDYNAMIC CONDITIONS OF USE OF A RAILGUN ACCELERATOR FOR SPRAYING OF VARIOUS MATERIALS ON TARGET SURFACES
A model of plasma outfl ow from the channel of a railgun accelerator to an inert-gas atmosphere has been developed with the aim of optimizing the process of deposition of the substance from the plasma phase on the target. It has been established that the interaction between the plasma jet formed from the plug material at exit from the railotron and the gas fl ow preceding the plug must be minimized. It has been shown that the conditions necessary are suffi ciently universal and are reduced to correct choice of the distance at which the target must be installed in relation to the exit section of the railotron channel.
Author: N. I. Alekseev, K. V. Tverdokhlebov, B. G. Zhukov,a R. O. Kurakin, and S. V. Bobashev
Keywords: railotron, plasma spraying, plasma plug, shock waves in the plasma
CONCERNING SOUND EMISSION DURING JET IMPINGEMENT ON A BARRIER
Using the shadow method of sound fi eld structure visualization, the sound emission during supersonic jet impingement on the edge of a fl at plate and on an annular barrier has been investigated.
Author: V. G. Pimshtein
Keywords: supersonic jet, barrier, sound emission.
MAGNETOGASDYNAMIC CYLINDRICAL SHOCK WAVES IN A ROTATING NONIDEAL GAS WITH RADIATION HEAT FLUX
A similarity solution is presented for a cylindrical magnetogasdynamic shock wave in a rotating nonideal gas in the presence of a variable axial magnetic fi eld in the case where the radiation heat flux is of importance. The initial angular velocity of the medium is assumed to vary as some power of the distance from the symmetry axis. The radiation heat flux is evaluated from the equation of motion without explicit use of the radiation transfer equations. It is shown that the gas nonidealness increases the shock strength but decreases the shock velocity. On the other hand, the presence of a magnetic fi eld decreases the shock strength but increases the shock velocity. Moreover, the shock velocity increases with the ratio of specifi c heats. The total energy of the shock wave increases with time.
Author: J. P. Vishwakarma and Nanhey Patel
Keywords: cylindrical shock waves, self-similar fl ow, rotating nonideal gas, radiation heat flux, axial magnetic field
HEAT CONDUCTIVITY OF ADHESIVE INTERLAYERS OF COMPOSITES WITH ADHESIVES MODIFIED BY THE ACTION OF COMBINED PHYSICAL FIELDS
This paper considers the action of a vibrowave fi eld combined with a magnetic or electric fi eld on the heat conductivity of dispersion-fi lled adhesive interlayers. It has been established that under the action of combined physical fi elds the heat conductivity of the adhesive composite markedly increases. It has been shown that the effective heat conductivity of the adhesive interlayer can be regulated by varying the magnetic or electric fi eld intensity and the frequency of mechanical vibrations of the vibrowave fi eld, as well as the temperature, concentration, and dispersion of the fi ller.
Author: V. M. Popov and O. R. Dornyak
Keywords: heat conductivity coeffi cient, magnetic or electric fi elds, vibrowave action
SELECTION AND VERIFICATION OF PHENOMENOLOGICAL SUSPENSION-VISCOSITY MODELS
An analysis of the accuracy of the existing phenomenological suspension-viscosity models has been made. A procedure for approximating the viscosity curve by three one-parametric models but identifying only two empirical parameters has been proposed. Phenomenological models most accurately describing experimental data for suspensions of different compositions in the entire range of concentrations of a dispersed phase have been established.
Author: A. F. Fedotov
Keywords: suspension, viscosity, approximation, phenomenological model
EFFECT OF TWO TEMPERATURES AND STIFFNESS ON WAVES PROPAGATING AT THE INTERFACE OF TWO MICROPOLAR THERMOELASTIC MEDIA
This paper is concerned with the effect of two temperatures and stiffness on wave propagation at the interface of two micropolar thermoelastic media on the basis of the thermoelasticity theory of type III (Green–Naghdi, or GN, model). The amplitude ratios of various refl ected and transmitted waves are obtained for an imperfect boundary. The effect of the normal force stiffness, transverse force stiffness, transverse couple stiffness, thermal conductivity, and two temperatures on these amplitude ratios is considered for the incidence of various plane waves. The variations of the amplitude ratios with the angle of incidence are shown graphically.
Author: Rajneesh Kumar and Mandeep Kaur
Keywords: thermoelasticity with energy dissipation, two temperatures, refl ection and transmission, amplitude ratios, imperfect boundary
IMPROVING THE QUALITY OF MANUFACTURE OF POLYMER-COMPOSITE PRODUCTS USING COMPUTED TOMOGRAPHY AS A NONDESTRUCTIVE-TESTING METHOD
The main advantages of the use of computed x-ray tomography for nondestructive testing of the state of the internal structure of laminated polymer composite materials with the aim of improving the quality of manufacture of products from composites have been demonstrated.
Author: V. N. Bakulin, A. A. Larin, and V. I. Reznichenko
Keywords: nondestructive testing, composite materials, computed tomography, internal defects