bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of a two-dimensional binary gas mixture outflow into vacuum through a thin slit on the basis of direct solution of the Boltzmann kinetic equation
Authors: Sitnikov S S , Tcheremissine F G , Sazykina T A 
Published: November 2021

Abstract
Two-dimensional binary gas mixture outflow from a vessel into vacuum through a thin slit is studied on the basis of direct solution of the Boltzmann kinetic equation. For evaluation of collision integrals in the Boltzmann equation a conservative projection method is used. Numerical simulation of a two-dimensional argon-neon gas mixture outflow from a vessel into vacuum was performed. Graphs of mixture components flow rate dependence on time during the flow formation, as well as fields of molecular density and temperature for steady-state regime, were obtained.
On reconstruction of the coefficient in complex Helmholtz’s equation
Authors: Malovichko M , Orazbayev A , Kloss Yu , Khokhlov N 
Published: November 2021

Abstract
This note summarizes some preliminary results on the fast solution of the coefficient inverse problem for the Helmholtz equation, given measured pressure in a set of observation points. The Helmholtz equation is the model PDE for the harmonic problem of the linear theory of elasticity, and this work is a move in that direction. The problem has been the primary focus for several research areas, most notably seismic exploration. Still, practical problems are very challenging because they are non-linear and large. In this paper, we develop a novel numerical method for seismic full-waveform inversion based on Newton iterations. Its distinctive future is that it does not require the Jacobian of the target functional. Thus, in certain scenarios, it will perform only a fraction of computations comparing to the conventional Gauss-Newton algorithm. We present some early results on the Helmholtz equation in two dimensions.
Determination of Reynolds shear stress from the turbulent mean velocity profile and spectral characteristics of Orr-Sommerfeld -Squire equations
Authors: Selim R. S. 
Published: November 2021

Abstract
Theoretically, based on a waveguide model, the expression of the tangential stress is formulated for steady, two-dimensional incompressible fluid flow over a flat plate in turbulent boundary layer. It is dependent on some factors, one of them, the behaviour of the last damping mode eigenvalues, and eigenfunctions, that are deduced from solution Orr-Sommerfeld equation by spectral Chebyshev collocation Method. Verification of the latter method is investigated by comparison the deduced formula of turbulent tangential stress with experimental data. In addition to, weight factors in this expression are connected to define the condition of dynamical system solution for multiple 3-wave resonance. This system is solved numerically, and the dynamic invariant is normalized to obtain the time average of the square modulus harmonic, and sub harmonics amplitudes by theorem Birkhoff-Khinchin. Comparison is made between the time-averaged and the phase average for the square modulus of harmonic, and sub harmonic amplitudes that defined on the unit sphere, in the state of multiple 3-wave resonance.
About boundary conditions for kinetic equations in metal
Authors: Karimov F , Lam T N , Yushkanov A A 
Published: November 2021

Abstract
Boundary conditions for kinetic equations describing the dynamics of electrons in the metal were analyzed. The boundary condition of the Fuchs and the boundary condition of Soffer were considered. The Andreev conditions for almost tangential moving electrons were taken into account. It is shown that the Soffer boundary condition does not satisfy this condition. The boundary condition was proposed that satisfies the Andreev condition. It is shown that this boundary condition passes in the limiting case into the mirror–diffuse Fuchs boundary condition.
Longitudinal Plasmons in a Thin Flat Conductive Film
Authors: Zotov A A , Zverev N V 
Published: November 2021

Abstract
The longitudinal plasmons in the plasma of conductivity electrons between the surfaces of a thin flat conductive film are investigated. It is shown that these plasmons lead to a resonant behaviour of the optical power coefficient of E-wave interaction with this film. The conditions for appearance of these plasmon resonances are found, and peculiarities of the dependence of the resonant frequencies on the film characteristics are revealed.
Relaxation type Kinetic equation for electrons in polycrystalline metal
Authors: Lam T N , Karimov F , Yushkanov A A 
Published: November 2021

Abstract
The kinetic equation for electrons in a polycrystalline metal is considered. A kinetic equation is written that describes in a unified manner the scattering of conduction electrons both by impurities or phonons and by grain boundaries. This kinetic equation takes into account the scattering of electrons at the boundaries of crystallites of a polycrystalline metal An expression is obtained for the bulk conductivity in the general case. Let us analyze the effect of electron scattering at grain boundaries on its electrical properties.
MATLAB Modelling electron energy spectrum in one-dimensional quantum well with infinitely high walls for GaAs solid solution
Authors: Kozhanova E R , Tkachenko I M 
Published: November 2021

Abstract
The paper presents calculations of electron states in semiconductor nanostructures AlxGa1–x As (x=0) and simulates the energy spectrum of the electron in a one-dimensional quantum well with infinitely high walls of a given width (from 10 to 30 atomic monolayers) using MATLAB application. The data is visualized using a wavelet transform with different wavelet functions.
Dependence of the integral characteristics of a nematic light modulator on the physical parameters of a liquid crystal
Authors: Simonenko G V 
Published: November 2021

Abstract
In the present work, the effect of physical constants of an LC material on the integral characteristics of a modulator operating in a waveguide mode in an LC structure with a twist angle of 270 and antisymmetric boundary conditions in the working cell was studied using the method of computer simulation. It is shown that, under antisymmetric boundary conditions, the small value of the total response time of the LC modulator is due to the absence of a “backflow” in the LC cell and the role of only half of the LC working gap thickness in the dynamics of switching between two states in such a device. In addition, it was found that in order to simultaneously achieve high contrast ratios and a short total response time of the device, it is necessary to choose an LC material with a high value of its dielectric anisotropy. In this case, there is an optimal set of elasticity constants for the LC material, which simultaneously realizes a high contrast ratio and a short total response time of the modulator.
Mathematical Modeling of Survivability Function for Thermoelectric Module
Authors: Sattar Sh , Osipkov A , Belyaev V V 
Published: November 2021

Abstract
Developing an optimized reliability model for thermoelectric module at the stress where the probability of module to functions without abruptive failure is a challenging aspect. One of the major reasons is the mismatch of thermal expansion coefficient, which has severe effects on segmented moduli compared to unsegmented moduli. The likelihood of a thermoelectric module to survive at certain level of thermo-mechanical stresses varies by varying number of component (layers) in thermoelectric leg. On another hand, selection of an adequate distribution model to predict reliability and sustainability of the thermoelectric module requires development of new optimized stress-strength-based model. In this paper the predictive reliability model for high temperature segmented module is derived from parametric Lognormal mean residual life and nonparametric Lognormal-kernel survival function to measure probability of module to survive at certain thermo-mechanical stress. A comprehensive comparative discussion has been done to illustrate the maximum likelihood based on Bayesian nonparametric lognormal-Kernel inference method regarding to Monte Carlo simulation, Weibull’s distribution, and Lognormal mean residual life for various shapes for the survival function. It has been demonstrated that nonparametric lognormal-kernel survival function has high ratio of probability to predict the survival of module at higher discrete thermo-mechanical stress data.
Optical rotation dispersion of cholesteric-nematic mixture
Authors: Vasilchikova E N , Dmitrieva A D , Kondakova A V , Kurilov A D , Usachev V V , Muravsky A A , Chausov D N 
Published: November 2021

Abstract
The dispersion of the specific rotation constant of a cholesteric-nematic mixture of 5CB and Ch17 at a low concentration was studied by optical spectroscopy. The dispersion of the anisotropy of the refractive index as a function of the wavelength is studied, and the helical pitch of the cholesteric-nematic mixture is calculated.
Special features of short-duration processes in condensed media
Authors: Khantuleva Tatyana A. , Kats Victor M. 
Published: November 2021

Abstract
The problem of the short-duration processes is considered on the base of the nonlocal theory of non-equilibrium transport, taking into account inertial effects. The system temporal evolution out of equilibrium connected to the dynamic structure transition described by the Speed-Gradient principle (SG-principle or SGP) developed in control theory and cybernetic physics. In the manuscript, we show that retardation of the system response to the short-duration loading due to inertial effects influences on the system evolution and can change its direction. The response to the shock loading of condensed matter is compared to quasi-stationary loading in a wide range of conditions. The short duration loading can lead the system into the structure unstable state and even give rise to self-organization of turbulent structures in the medium. The use of SGP for the modelling of such processes opens new possibilities to control them.
The formation of super-long nano-chains during evaporation of metals with a help of intensive impacts
Authors: Klassen N V , Provotorov P V 
Published: November 2021

Abstract
Extended nanostructures, in particular, chains of nanoparticles, are of great interest for microelectronics, biomedicine, and energy. But until now, it was possible to obtain such structures with the lengths not more than a few millimeters. We have developed several techniques based on laser and electric evaporation of metals, which provide the formation of nanochains with the lengths up to 60 cm. A significant factor in the formation of such structures is the constructive participation of turbulent vortices, which create the necessary compression and subsequent agglomeration of the vapors of metals and oxides subjected to the intensive electrical or laser impacts. Research and production of the nano-structures with large surfaces and lengths provide promising opportunities for the direct converters of solar energy and ionizing radiation to electricity, development of new optoelectronic and microelectronic devices as well as highly sensitive biosensors.
Giant spin-valve effect in Al/Y3Fe5O12 heterostructures
Authors: Skryabina O V , Uspenskaya L S 
Published: November 2021

Abstract
Superconducting phase transition in the aluminium stripes fabricated on yttrium-iron garnet and on oxidized silicon substrates is studied. Reduction of critical temperature, widening of superconducting transition depending upon the mutual current and magnetization orientations as well as on current strength are observed in aluminium on garnet comparing with aluminium on silicon. The proximity and triplet proximity effects, Andreev reflection, exchange interaction, spin-orbit coupling and self YIG magnetic field impacts on the observed effects are discussed. We show that only accounting for the spin-orbit coupling and self-magnetic field of YIG is allowed to explain the observed phenomenon of asymmetric change in the transition under the variation of the current and magnetization alignment. Based on the obtained results, we suggest a new geometry of spin-valve with hundreds percent variation of the resistance controlled by the current.
The concept of biaxial surface potential and polymer aligning layers in electro-optical cells based on helical nanostructures of ferroelectric liquid crystal
Authors: Tkachenko T P , Zhukov A A , Pozhidaev E P 
Published: November 2021

Abstract
The paper considers the possibility of controlling the alignment quality of helical nanostructures of ferroelectric liquid crystals (FLCs) within the concept of biaxial surface potential due to variation the FLCs helical pitch p0
and polymer aligning layers structures.
Influence of the temperature field in the energy-saving carbon-graphite thermal unit on configuration of the solidification front under different conditions of growing fluoride single crystals by the HDS method
Authors: Yusim V A , Sarkisov S E , Kloss Y Y , Yusim F A , Ivanova L V 
Published: November 2021

Abstract
Mathematical modeling of the influence of the temperature field created by the ECU on the position and on configuration of the solidification front under different conditions of growing single crystals of fluorides by the HDS method has been carried out. Data were obtained for different growing conditions for single crystals of fluorides and their effect on configuration of the solidification front in various modifications of the ECU of the first and second types. From a comparison of mathematical calculations, a conclusion was made about the most suitable conditions for the synthesis of these single crystals.
Advanced processes for low-temperature formation of functional metal oxide based thin films
Authors: Abduev A , Akhmedov A , Asvarov A , Kanevsky V , Muslimov A , Belyaev V , Generalov D , Nikolaeva D , Tirado J , Frah M A A 
Published: November 2021

Abstract
The analysis the discharge processes in magnetron plasma, target sputtering processes, as well as nucleation and formation of oxide thin films during dc magnetron sputtering is carried out. Particular attention is paid to the phenomenon of instabilities of the current-voltage characteristics of magnetron plasma during the sputtering of oxide targets, the processes of structural transformations of the surface of metal oxide targets under ion bombardment impact, and the mechanisms of low-temperature magnetron deposition of metal oxide thin films. Based on the results of the analysis performed the optimal routes for improving technologies for the low-temperature formation of transparent conductive oxide thin films have been discussed.
Synthesis of ZnS:Cu,Br radioluminescent phosphors using the electron-beam treatment and studying their characteristics
Authors: Bakhmetyev V V , Zelenina E V , Shvindin M A 
Published: November 2021

Abstract
ZnS:Cu radioluminescent phosphors find their applications in medicine nondestructive testing, safety control and can be used as a part of the solid-state radioluminescent light sources (SRLS). This devices are very promising technology due to their independence longevity and safety compared to the gas-filled RLS. Because of the fact that tritium (the most popular radioisotope for RLS) has a very short range in substances, the improving the operating performances of radiophosphors is a crucial task for SRLS. In our study we used the electron-beam treatment to increase the brightness of radioluminescence of ZnS:Cu phosphors. It was found that bombardment of the phosphors initial charge with electrons of 900 kEv energy improves the brightness of radioluminescence by 15 – 20%. Double modifying of the initial charge and ready phosphor cause the 80% increase of brightness. The effect of electron-beam treatment on the phase content and the surface properties was studied at varying the content of activator (Cu) in the range of 0 – 0.6 % mass. As a result the model describing structure of the acid-base sites on the ZnS:Cu phosphor surface was suggested.
Formulation of the modern indicator devices modelling problem
Authors: Buzaeva E A , Evsevichev D A , Maksimova O V 
Published: November 2021

Abstract
This work is dedicated to study of the structural characteristics and parameters in advanced electroluminescent structures. The important problems in this area are the high complexity and the slowness of the design calculation processes. The problem can be solved by developing a mathematical model of the system based on equivalent circuits. First step in developing a mathematical model is formulation.
Improving the performance of the air-cooling unit in the cooling system of a radar
Authors: Borisov Yu A , Volkov-Muzilev V V , Kalashnikov D A , Khalife H S 
Published: November 2021

Abstract
The article discusses the issues of reducing the size of the cooling unit of the antenna of a radar station by improving the gas-dynamic processes occurring in the air-cooling unit. The results of the experimental studies of the gas flow in a plate-fin heat exchanger, being blown by one axial fan are presented. The feasibility of changing the number of axial fans for organizing a more uniform flow around the heat-exchange surfaces has been determined by calculation and theoretical methods. The calculation results are confirmed by experimental studies of the air flow in the segment of the heat exchanger, which is provided by a smaller fan.
Modeling the working media flow in shut-off valves with displacement of the regulating body perpendicular to the flow axis
Authors: Soloveva V V , Pugachuk A S , Chernyschev A V 
Published: November 2021

Abstract
The mathematical model of the working fluid movement in the flow section of the wedge type two-disc parallel gate valve is developed. The simulation of the fluid flow through the valve cavity is carried out, as a result the flow parameters are obtained in a wide range of Reynolds numbers at the entrance to the calculated area. The dependence of the hydraulic resistance as a function of the Reynolds number for liquid and gas flow is calculated. The various positions of the shut-off body in the flow part of the valve are considered and the area of reduced pressures in which the effect of cavitation may occur during fluid flow is estimated.
Application of the video correlation method to measure the velocity on the surface of a liquid metal
Authors: Teplyakov I O , Vinogradov D A , Klementyeva I B , Ivochkin Yu P 
Published: November 2021

Abstract
In this work, the applicability of the video correlation method proposed by the authors for measuring the velocity on the surface of a liquid metal in an electrovortex flow in a hemisphere is investigated. The method is based on calculating the cross-correlation of the brightness signals of two closely spaced points in the video. It is shown that the method allows quite simply determining the velocity of the liquid metal.
Eddy generation and variability of the marginal ice zone in the Fram Strait according to satellite radar measurements
Authors: Petrenko L A , Kozlov I E 
Published: November 2021

AbstractBased on analysis of spaceborne synthetic aperture data (SAR), acquired in summer of 2007 over Fram Strait and around Svalbard, we investigate spatial and temporal variability of the ice edge and generation of eddies in the marginal ice zone. During the season, the ice-water boundary nonuniformly moves along its entire length with the overall width of the ice edge displacement ranging from 30 to 220 km. The ice edge movement is often accompanied by generation of eddies and filaments peaking in August. Analysis of the data serves to find out over 2000 distinct MIZ eddies with a clear dominance of cyclones (78%). In July the detected eddies are predominantly formed along the ice edge, in August most of them are generated inside the MIZ, while in September their numbers along the ice edge and within the MIZ are similar. Larger eddies (10-20 km in diameter) are found over deep Fram Strait and the Greenland Sea shelf, while smaller eddies (~5 km) are observed in coastal regions around Svalbard.
Application of the time-frequency technique for analysis of velocity fluctuations in the wake of a teardrop profile in the presence of a localized flow inhomogeneity
Authors: Mironov D S , Lebiga V A , Zinoviev V N , Pak A Yu 
Published: November 2021

Abstract
Experimental simulation of the inhomogeneity of the incident flow localized in time and space on a bluff tear-drop airfoil is carried out. It is shown that in the region outside the aerodynamic wake of the tear-drop airfoil, the presence of inhomogeneity leads to an increase in the amplitudes of velocity fluctuations in a wide frequency range. In the region inside the wake, the presence of inhomogeneity leads to the suppression of velocity fluctuations at the frequency of vortex shedding by a factor of 2–3 in amplitude. The intensification of fluctuations at frequencies above the main one was also noted, and there was no effect on fluctuations at lower frequencies.
Reflection of sound pulses from an inhomogeneous bubble medium
Authors: Ogorodnikov I A 
Published: November 2021

Abstract
The effect of changes in the volume concentration of bubbles in the boundary zone of the bubble medium on the nature of reflection and radiation of the excited bubble medium is studied. The spectral characteristics of the radiation of a bubble medium are obtained at the initial stage of transition radiation and at large times when the radiation is stationary. It is shown that in the initial phase the emission spectrum is broadband and is located in the absorption band of the bubble medium, and at large times the emission spectrum is located outside this band.
Unsteady cavities near the hydrofoil with a small aspect ratio
Authors: Skripkin S G , Tsoy M A , Kravtsova A Y 
Published: November 2021

Abstract
Using digital processing of high-speed visualization data on a cavitation flow near NACA hydrofoil with critically low aspect ratio, the frequencies of the formation and separation of cavities in the flow are identified. It is shown that in the case of development of cloud cavitation the main dimensionless frequency varies within 0.4, which corresponds to the type of internal instability. The Strouhal number corresponds to the frequency of attached cavity occurrence and varies in range from 0.6 to 0.8. The Strouhal numbers calculated in third mode exceed 1. This mode corresponds to the forming of very small cavities near the leading edge of hydrofoil.
Collision of water drops with a thin cylinder
Authors: Fedyushkin A I , Rozhkov A N , Rudenko A O 
Published: November 2021

Abstract
The collision of water drops with a thin cylinder is studied. The droplet flight trajectory and the cylinder axis are mutually perpendicular. In the experiments, the drop diameter is 3 mm, and the diameter of horizontal stainless-steel cylinders is 0.4 and 0.8 mm. The drops are formed by a liquid slowly pumped through a vertical stainless-steel capillary with an outer diameter of 0.8 mm, from which droplets are periodically separated under the action of gravity. The droplet velocity before collision is defined by the distance between the capillary cut and the target (cylinder); in experiments, this distance is approximately 5, 10, and 20 mm. The drop velocities before the impact are estimated in the range of 0.2–0.5 m/s. The collision process is monitored by high-speed video recording methods with a frame rate of 240 and 960 Hz. The test liquids are water. Experiments and numerical simulation show that, depending on the drop impact height (droplets velocity) different scenarios of a drop collision with a thin cylinder are possible: a short-term recoil of a drop from an obstacle, a drop flowing around a cylindrical obstacle while maintaining the continuity of the drop, the breakup of a drop into two secondary drops, one of which can continue flight and the other one is captured by the cylinder, or both secondary droplets continue to fly, and the drop can be also captured by the cylinder, until the impact of the next drop(s) forces the accumulated drop to detach from the cylinder. Numerical modeling satisfactorily reproduces the phenomena observed in the experiment.