bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersion properties of uniform trapezoidal optical waveguides
Authors: Cheplagin N.A. , Zaretskaya G.A. 
Published: December 2019

Abstract
A method for calculation of the propagation constant of guided modes in the optical waveguides with trapezoidal cross-sections is proposed. The method enables to calculate a propagation constant correction factor that arises due to perturbations of the cross-section of a reference rectangular waveguide. The correction factor is analytically calculated within the framework of the coupled-mode theory. A refined form of the coupling coefficient is obtained owing to the application of a concept of effective excitation sources and accurate account of boundary conditions. An impact of the waveguide cross-section shape on its dispersion properties is analysed. The necessity to take into account the proposed form of the coupling coefficient is demonstrated by comparison of the simulation results with other methods of dispersion calculation.
Digital holographic testing of the optical fiber at welding area
Authors: Prisiazhniuk A V , Sokolenko B V , Poletaev D A , Shostka N V 
Published: December 2019

AbstractA method to analyse of optical fibers inhomogeneity in welding junction using digital holography is proposed. The method utilizes lens-less Gabor scheme for recording of a digital hologram with numerical reconstruction by angular spectrum approach. Qualitative image analysis applied on the intensity distribution of specimen after hologram reconstruction enables to evaluate the structural defects inside the fiber core and cladding after welding procedure, which are not observable with conventional microscopy. The opportunities of presented method were approved with a wavelength-division multiplexing fibers of known defects introduced by axial misalignment of welded parts. A compact in-line digital holographic recording set-up for express and robust optical fiber analysis was developed through its application to a welding quality testing. It is shown how the value of axial misalignment of welding fibers lead to a variation of artificial intensity distribution around the joint in reconstructed image.
Three-wavelength optoelectronic system for hemodialysis monitoring
Authors: Konoplev G A , Stepanova O S , Frorip A , Gerasimchuk R P 
Published: December 2019

Abstract
Novel spectrophotometric method and optoelectronic spectral equipment for automatic on-line monitoring of hemodialysis treatment are introduced. The method allows determination of the concentrations of uric acid and creatinine in effluent dialysate by measuring ultraviolet (UV) absorption at three wavelengths. An optoelectronic spectral sensor with three deep ultraviolet light emitting diodes (LED), a flow-through quartz cuvette connected to the outlet of a dialysis machine, and a solar-blind UV photodetector was designed. Dedicated software for sensor control, spectral data acquisition, and spectral analysis was developed. The results of preliminary clinical trials of the developed system are presented.
Optical materials for lens concentrators of solar radiation
Authors: Shvarts M Z , Emelyanov V M , Nakhimovich M V , Soluyanov A A 
Published: December 2019

Abstract
“Solar” Abbe number is proposed to operate in assessing the suitability of optical materials at sunlight concentrators manufacture. Comparative results are presented for materials practically used in concentrator photovoltaics from the point of view of designing Fresnel lenses from them with a high average concentration in the focal spot of the minimum size and at the same time with minimum focal length.
Current Distribution in GaAs Solar Cell with Carbon Nanotube Transport Layer
Authors: Mitin D M , Raudik S A , Mozharov A M , Bolshakov A D , Fedorov V V , Nepokh V V , Mikhailovskii V Y , Rajanna P M , Nasibulin A G , Mukhin I S 
Published: December 2019

Abstract
Numerical simulation and EBIC measurements of GaAs-based solar cells with metal grid and CNT transport layer were performed. Influence of CNT transport layer properties on lateral current distribution was analyzed. In accordance with electron beam induced current measurements it was shown that CNT demonstrates perfect transport properties leading to good charge carrier’s collection.
Triboelectric current generation in InP
Authors: Sharov V A , Alekseev P A , Dunaevskiy M S , Reznik R R , Cirlin G E 
Published: December 2019

Abstract
Energy harvesting is an area that presents the greatest potential for powering wireless low-energy electronics. Development of semiconductor-based energy harvesting is of interest. Herein we focus on studying two different energy harvesting mechanisms in indium phosphide. Piezoelectric harvesting was checked by bending vertical InP nanowires with conductive atomic force microscope (AFM) probe and simultaneously detecting current passing through the probe. No current pulses were observed that we associate with surface trapping of piezoinduced carriers. Triboelectric generation was studied by creating frictional contact between AFM tip and metal-dielectric-semiconductor (MIS) interface formed by InP layer covered with native oxide. Current peaks of 320 pA amplitude corresponding to the current density around 2.3 kA/m2 were observed under sliding reciprocating motion of the tip during AFM scanning. Achieved current density was higher than in polymer- and silicon-based triboelectric structures. The open-circuit voltage value exceeded 15 mV and the output electric power was 35 W/m2.
Studies of the thermovoltaic effect in semiconductors in the medium temperature range
Authors: Kaminskii V V , Soloviev S M , Sudak N M , Zaldastanishvili M I , Sharenkova N V , Kazanin M M 
Published: December 2019

Abstract
The possibilities of increasing the voltage generated due to the thermovoltaic effect in semiconductors by increasing the generation temperature are considered. It is shown on the example of SmS that an increase in voltage can be achieved by increasing the depth of impurity donor levels in semiconductors. The magnitude of the generated voltage is 0.15V in SmS/Sm0.7Eu0.3S as against 0.05 V in undoped SmS. The possibility of obtaining generation due to the thermovoltaic effect is also considered on a classical PbTe semiconductor operating in a higher-temperature region compared to SmS. Generation value of 0.11V was obtained.
On modelling optical parameters of InAs quantum dots for cascade GaInP / GaAs / Ge solar cells
Authors: Panchak A N , Mintairov S A , Mintairov M A , Salii R A , Shvarts M Z , Kalyuzhnyy N A 
Published: December 2019

Abstract
Triple-junction solar cells InGaP/GaAs/Ge usually are manufactured using MOCVD technology. However, the potential of such structures is investigated in the laboratory on samples made using MBE. One of the ways to increase efficiency is the implanting of InAs quantum dots in GaAs cascade. In this paper the approaches to the mathematical modeling of Ga (In) As structures grown by MOCVD and MBE are studied.
Laser-induced magnetization precession in the magnetite Fe3O4 in the vicinity of a spin-reorientation transition
Authors: Karpovsky I O , Kazenwadel D L , Shelukhin L A , Balbashov A M , Pisarev R V , Kalashnikova A M 
Published: December 2019

Abstract
Using time-resolved magneto-optical pump-probe technique we demonstrate excitation of magnetization precession in a single crystalline bulk magnetite Fe3O4 below and in the vicinity of the Verwey and spin-reorientation (SR) phase transitions. Pronounced temperature dependence of the precession amplitude is observed suggesting that the excitation occurs via laser-driven spin-reorientation transition. Similarity observed between the characteristic features of the laser-induced ultrafast SR and Verwey transitions suggests that they both rely on the same microscopic processes.
Conductive AFM study of the local current in thin ferroelectric sol-gel PZT films
Authors: Gushchina E V , Zaitseva N V , Delimova L A , Seregin D S , Vorotilov K A 
Published: December 2019

Abstract
The local current distribution across the grains and their boundaries in ferroelectric PZT films are studied using conductive AFM. The films were formed with various grain structures and different lead excess content by chemical solution deposition. C-AFM measurements have shown the influence of the lead excess and seed sublayer crystallization conditions on the grain-boundary conductivity. PZT films with fixed 0-15 wt% Pb excess demonstrate non-conductive grain boundaries, whereas in films with fixed 30 wt% Pb excess the grain-boundary conductivity is found to be much higher than that of the grains themselves. Conductive grain-boundaries was also found in PZT films without lead excess in crystallized sublayer. A study of the transient current at varied preliminary polarization revealed the current peaks in the current-voltage curves. The appearance conditions and magnitude of these peaks depend on the grain-boundary conductivity. The correlation between the grain-boundary conduction and the current polarization dependences is confirmed.
Electrocaloric effect and dielectric properties in ferroelectric ceramics based on solid solution of barium-calcium titanate
Authors: Anokhin A S , Es’kov A V , Pakhomov O V , Semenov A A , Lähderanta E 
Published: December 2019

Abstract
Barium titanate based ceramics is the most common class of lead-free ceramics due to its high values of dielectric constant, polarization, piezo- and electrocaloric effects. In this paper dielectric properties and electrocaloric effect in ceramics based on solid solution of barium-calcium titanate had been studied. It was shown, that increasing of calcium titanate in solid solution leads to increasing of dielectric constant and electrocaloric effect, simultaneouslyit leads to decreasing of leakage currents. While increasing fraction of calcium titanate from 0% to 10%, dielectric constant at frequency of 1 kHz rises from 10500 to 13600, maximum adiabatic electrocaloric response at ΔE = 1.3 V/μm rises from 0.5 K to 0.7 K.
Carrier mobility in the channel of AlGaN/(AlN)/GaN and InAlN/(AlN)/GaN heterostructures, limited by different scattering mechanisms: experiment and calculation
Authors: Arteev D S , Sakharov A V , Lundin W V , Zakheim D A , Zavarin E E , Tsatsulnikov A F 
Published: December 2019

Abstract
Calculational analysis of different scattering mechanisms of two-dimensional electron gas in AlGaN/(AlN)/GaN and InAlN/(AlN)/GaN high-electron mobility transistors was carried out. It was found that the mobility of AlGaN-based structures at room temperature is mainly limited by inherent scattering mechanisms (namely, optical and acoustic phonon scattering), while the mobility in our InAlN-based structures is limited by the interface roughness scattering. The low-temperature mobility is found to be limited by the interface roughness scattering for both AlGaN- and InAlN-based structures.
The effect of transverse rectification of electromagnetic waves in a two-dimensional superlattice
Authors: Konchenkov V I , Myachkova A A , Zav’yalov D V 
Published: December 2019

Abstract
Using the constant-collision frequency approximation, an analytical expression was obtained for the direct current density occurring in a two-dimensional superlattice when two waves with mutually perpendicular polarization planes are exposed to the sample, the frequency ratio of which is 2.
Effect of coherent population trapping in a compact microfabricated Cs gas cell pumped by intra-cavity contacted VCSELs with rhomboidal oxide current aperture
Authors: Bobrov M A , Blokhin S A , Maleev N A , Blokhin A A , Vasyl’Ev A P , Kuzmenkov A G , Gladyshev A G , Novikov I I , Petrenko M V , Ospennikov A M , Ermak S V , Ustinov V M 
Published: December 2019

Abstract
Miniature laser source based on intracavity-contacted vertical-cavity surface-emitting laser with rhomboidal oxide current aperture was investigated for coherent population trapping (CPT) resonance excitation in microfabricated 133Cs gas cell filled with Ne buffer gas under the pressure of 300 torr. The cell operation temperature was 90°C. The laser output power was 550 μW at bias current of 3.2 mA and 65°C. The short-term stability of ∼2.5·10-11 at the measurement time of 1 sec was estimated from CPT resonance signal measurements.
New 50-keV neutral beam injector for the Globus-M2 spherical tokamak
Authors: Telnova A Yu , Minaev V B , Shchegolev P B , Bakharev N N , Shikhovtsev I V , Varfolomeev V I 
Published: December 2019

Abstract
A design of the new neutral beam injector and the process of generation of a high-energy atomic beam are described in detail. The injector is fully prepared for experiments on auxiliary heating of the Globus-M2 tokamak plasma. The docking of injector with tokamak vacuum vessel is completed. The predictions for non-inductive current drive by 50 keV 1 MW neutral beam in the Globus-M2 are presented.
Implementation of cross-phase analysis for study of MHD instabilities arising on TUMAN-3M and Globus-M tokamaks
Authors: Balachenkov I M , Patrov M I , Petrov Yu V , Tukachinsky A S 
Published: December 2019

Abstract
Following paper represents a method to resolve spatial mode structure of plasma MHD instabilities employing cross-phase correlation analysis applied to signals of magnetic probes, mounted on Globus-M and Tuman-3M tokamaks. The data on observations of toroidal Alfven eigenmodes (TAEs), which were formerly identified in Globus-M tokamak discharges, has been analyzed. Possible interpretation of the phase plot, acquired from analysis of NBI-stimulated ion-cyclotron emission (ICE) on Tuman-3M is given as well. The method described below turns out to be useful instrument for resolution of spatial structure of plasma instabilities, especially in D-shaped tokamaks with low aspect ratio.
Low-Voltage Arc in Alkaline-Earth Metal Vapors
Authors: Bogdanov A A , Martsinovsky A M 
Published: December 2019

Abstract
The work continues the earlier study of the Knudsen short (3 mm interelectrode distance) low-voltage arc in barium and strontium vapor. Probe measurements of plasma parameters for strontium were carried out in a wide range of discharge parameters (pressure 10–2 – 10–1 Torr, currents 0.5 to 30 A/cm2, anode voltage up to 10 V) in a stationary mode. The main regularities of changes in plasma concentration and electron temperature by the current-voltage characteristic are established. The kinetics of non-stationary processes — ignition of the discharge and plasma decay after the end of a pulse, was also investigated. A number of differences in plasma behavior compared to cesium arc were found, however, in general, the behavior of strontium discharge plasma turned out to be quite close to that of cesium - unlike low-voltage arcs in inert gases. This is explained by the similar nature of the energy level scheme in atoms of alkali and alkaline-earth metals.
Method for determining plasma density in a magnetic field
Authors: Vodopyanov A , Mansfeld D , Sintsov S , Viktorov M 
Published: December 2019

Abstract
A new method is proposed for measuring plasma density based on the direct determination of the phase shift of an electromagnetic wave during the passage of probe radiation through plasma using a broadband oscilloscope. The paper describes a scheme for measuring plasma density up to 4*1013 cm−3. Examples of using this method to determine the parameters of the inductively coupled plasma and plasma flows in a magnetic field are given.
Theoretical and experimental study of the “hydrodynamic” effect in laboratory ballistic launchers
Authors: Bykov N V , Tovarnov M S 
Published: December 2019

Abstract
This paper performs a theoretical and experimental study of the effect of increasing the velocity of projectiles during the high-speed extrusion of the polyethylene piston through a tapered section (also called a “hydrodynamic” effect). Mathematical modeling is performed using two methods. The first method is a quasi-one-dimensional description of the polyethylene piston deformation on a moving computational grid. The second method is axisymmetric modeling using the ANSYS AUTODYN package. In the experimental studies, the polyethylene piston was preaccelerated using a propellant charge, after which the escape velocity of the projectile was measured. The escape velocity of the projectile after the tapered section increased up to 50% compared to the input velocity. The experimental results are consistent with the theoretical calculations.
Dynamics of a spherical explosion in aqueous foam taking into account heat-exchange and dissipative processes
Authors: Bolotnova R Kh , Gainullina E F 
Published: December 2019

Abstract
Numerical study of the features of spherical explosion propagation process in a cylindrical pipe surrounded by an inner layer of aqueous foam with liquid volume fraction α10 = 0.2 has been carried out. The solution method is based on a two-phase model of gas-liquid mixture under conditions of single-pressure, two-temperature, two-velocity approximations and is implemented using the twoPhaseEulerFoam solver of the OpenFOAM software. In order to test the proposed model, a comparison was made of the calculations and experimental data on a spherical explosion in aqueous foam with liquid volume fraction α10 = 0.0083. When solving the main task, the efficiency of the considered foam barrier is shown in a comparative analysis with the solution obtained in the absence of a foam layer.
Disturbing effects of a cylinder-form macro-roughness on the turbulent free-convection boundary layer: Large Eddy Simulation
Authors: Levchenya A M , Kolesnik E V , Smirnov E M 
Published: December 2019

Abstract
The paper presents results of eddy-resolving numerical simulation of non-isothermal turbulent flow in the vicinity of an adiabatic circular cylinder that disturbs the turbulent free-convection boundary layer developing along a vertical heated plate. The computational domain used includes (i) a relatively long section, where the upstream free-convection boundary layer goes over to its natural state from the model state prescribed at the inlet boundary with a synthetic turbulence generator, (ii) a mid-section covering the disturbing cylinder, mounted normally on the plate, (iii) an outlet section that is much longer than the cylinder diameter. The mathematical model is based on the Navier-Stokes equation written with the Boussinesq approximation. In the case simulated, the height of the cylinder (equal to its diameter) is about two times less than the approaching boundary layer half-width, if estimated from the velocity profile. Characteristic features of unsteady phenomena in the flow disturbed by the macro-roughness are analyzed with a focus on behavior of arising horseshoe-like vortex structures. Quantitative data on heat transfer augmentation near the cylinder is presented.
Applications of the gas discharge sustained by the powerful radiation of THz gyrotrons
Authors: Sidorov A V , Glyavin M Yu , Golubev S V , Razin S V , Sintsov S V , Veselov A P , Vodopyanov A V 
Published: December 2019

Abstract
The terahertz frequency range currently remains the least studied from the point of view of gas-discharge physics. Recent progress in its mastering is associated, first of all, with the creation of powerful sources of terahertz radiation - gyrotrons. Nevertheless, the discharge sustained by the powerful radiation of the terahertz frequency range is of interest not only from the fundamental point of view (because of its lack of knowledge), but also from the applied one. This paper presents results of investigations aimed at studying the point-like THz discharge as a source of vacuum ultraviolet radiation and at research of CW THz plasma torch existing at atmospheric pressure and therefore having promising applications in various fields: plasma medicine, plasma chemistry, material processing etc. It is shown that it is possible to create a point-like plasma in an inhomogeneous gas flow with the density above the cut-off one (4·1015 cm−3 for 0.67 THz). It has been demonstrated that such plasma is an effective source of VUV and EUV radiation. Investigations of the atmospheric plasma torch, sustained by CW sub-terahertz radiation (1 kW @ 0.26 THz), demonstrated the possibility of the creation dense non-equilibrium plasma (2·1015 cm−3) with electron temperature in the range from 1 to 2 eV.
Numerical simulations for hydrodynamic technique protecting optical components in ITER divertor
Authors: Bukreev I M , Mukhin E E , Bulovich S V , Matyushenko A A , Babinov N A , Dmitriev A M , Litvinov A E , Razdobarin A G , Samsonov D S , Varshavchick L A , Zatilkin P A 
Published: December 2019

Abstract
There are several protecting techniques managing with contamination on optical surfaces of in-vessel diagnostic components in ITER. Analysis of impurity transport in narrow and curved gaps gave us the idea that it can’t be explained by convection flows. The proposed protecting construction, situated between plasma and irradiating laser mirror launcher, was analysed for effectiveness. The protecting ability of this construction is based on the principles of hydrodynamic, in particular on bevelled entrance, which provides redirection of polluting gas flow away from the optical components due to angling optical and geometrical channel axes. Several different numerical simulations were studied. The design, setting objectives as well as equations and parameters are under discussion. Results of 2D and 3D numerical simulations are provided.
Hydraulic resistance due to unsteady ow in river channels: numerical simulation results
Authors: Dyakonova Tatyana , Klikunova Anna , Khoperskov Alexander 
Published: December 2019

AbstractThe hydraulic resistance to ow in a river-type channel is due to the action of a large number of factors. We created numerical models of unsteady water dynamics in an inhomogeneous channel by varying its geometric and hydraulic characteristics. We focused on the study of ows at small values of the Manning roughness coefficient, when the water movement is unsteady. The transitional regime from a pulsating ow to a laminar ow is characterized by a complex system of large vortices covering the entire channel. The nonstationarity factor enhances the hydrological resistance to ow, and thus provides an additional contribution to the effective Manning coefficient.
Numerical study of blood flow in the spatial model of the abdominal aorta bifurcation: effect of an inlet conditions
Authors: Sinitsina D E , Gataulin Y A , Yukhnev A D , Smirnov E M , Zaitsev D K 
Published: December 2019

Abstract
The structure of the flow in a model configuration including a healthy bifurcation of the abdominal aorta, common, external and internal iliac arteries is investigated by a numerical method. It has established that the structure of the flow in the common, external and internal iliac arteries is characterized by a two-vortex secondary flow structure, and only in the phase of return flow, a single-vortex secondary flow develops at the exit of the internal iliac arteries. The influence of the inlet velocity profile skewness is significant only in the region upstream of the actual abdominal aorta bifurcation. In the iliac arteries, the influence of the inlet velocity profile shape is felt only through relatively weak changes in the cross-flow velocity field. Introducing a significant non-uniformity in the inlet velocity distribution does not change significantly general estimates of the minimum values of the cycle-averaged wall shear stress, TAWSS, and maximum values of the oscillation wall-shear index, OSI. This information is important for identification of the places mostly exposed to atherosclerotic vascular lesions for atherosclerotic lesions.