bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-feature automatic abstract based on LDA model and redundant control
Authors: Dan Tang , Yu Sun
Published: December 2020

With the continuous popularization of computer application technology and the rapid development of Internet technology, there has been an explosion of information in every field, and more and more information is transmitted and stored on the Internet in the form of electronic text. Automatic summarization can solve the problem that the speed of traditional hand-written summaries cannot keep up with the speed of electronic text information generation. Automatic summarization can use a computer to generate a comprehensive and accurate coherent short essay on one or more documents, so people can quickly understand the main content of the text, which greatly improves the efficiency of people’s learning and work. Nowadays, automatic summarization technology has achieved rich results, but Chinese document summarization is still in the shallow semantic analysis of text, and there are problems such as redundancy of summarization and poor quality of abstract content. In view of the above problems, this article is in the research and implementation of Chinese automatic summarization technology. On the one hand, LDA is used to mine the topic distribution of documents to obtain high-quality abstracts; on the other hand, the similarity between the sentences to be extracted is calculated to remove redundant information.
Calculation of the Shortest Path for Robot to Avoid Obstacles
Authors: Qi Li-hua , Xing Dong-qiu , Li Yan-ni , Cui Jing-na , Gao Xin-wei
Published: December 2020

Obstacle avoidance path was widely used in real life, such as rescue and search, through battle field, robot through obstacles. In this paper, the obstacle avoidance problem of robot was studied. By establishing a mathematical model and considering the speed change of robot when turning, the selection principle and calculation of the shortest path for robot to pass through the obstacle area were discussed.
Global Agricultural Robotics Research and Development: Trend Forecasts
Authors: Zhao Jingjuan , Yang Yanping , Zheng Huaiguo , Dong Yu
Published: December 2020

Agricultural robots have been recognized as one of the emerging technologies with the highest potential in agriculture. Through grasping the research and development trend of international agricultural robots and analyzing the technical hot spots, the strategy or plan of agricultural robots in China can be formulated with a decision-making support. This paper applies the methods of expert consultation, qualitative investigation and quantitative analysis to analyze and summarize the hot spots and frontier of agricultural robot research and the future development trend by tracing the development course of agricultural robots at home and abroad. Based on the analysis of China’s strategic needs and key development directions for the next few years, this paper provides references and suggestions for China’s forefront planning on basic research, technological R&D and industrial layout of agricultural robots in the future.
Spectral evolution of long gamma-ray bursts observed with Konus-Wind
Authors: Svinkin D S , Temiraev Yu R , Frederiks D D , Tsvetkova A E , Ulanov M V , Demin A G
Published: December 2020

We present a preliminary analysis of spectral evolution of 35 long bright gamma-ray bursts (GRBs) detected by Konus-Wind instrument. From the temporal and spectral analyses of the sample, we investigate the evolution of parameters of the smoothly joined broken power-law spectral model (the Band “GRB” function), in particular, we analyse hardness-intensity correlation within a burst. We show that the bulk of bursts exhibit Ep
∝ F

γ
relation with the slope γ ∼ 0.3−0.5, where Ep
is the vFv
spectrum peak energy and F is the energy flux; while a number of events have the smooth initial phase with strong spectral evolution with γ ≳ 1. Finally, we discuss derived the Band function parameters and their evolution pattern in the framework of GRB emission models.
Possible influence of solar and astronomical factors on a climate of Northern Fennoscandia
Authors: Ogurtsov M G , Veretenenko S V , Helama S , Jalkanen R , Lindholm M
Published: December 2020

Eleven proxy records of Northern Fennoscandia and North Atlantic climate variability were analyzed. Correlation of climatic records with (a) a quasi 11-year solar cycle of Schwabe, (b) a quasi 22-year solar cycle of Heil, (c) a quasi 20-year planetary-tidal cycle, related to wobbling of the Sun around the baricenter of the solar system, has been studied. A weak but stable and statistically significant correlation between the climatic proxies of Northern Fennoscandia and a double solar cycle was found to be present through the AD 1700–2000. No evidence of a connection between climatic records and both solar Schwabe cycle and quasi 20-year astronomic cycle were found. Possible physical mechanisms behind the revealed effect are discussed.
The X-ray polarimeter of solar flares for the Interhelioprobe mission: experimental determination of the response of the physical model to polarized x-ray radiation
Authors: Savchenko M I , Kruglov E M , Lazutkov V P , Skorodumov D V , Shishov I I
Published: December 2020

The work is devoted to the study of the characteristics of the PING-M hard x-ray polarimeter using its physical model (PING-P FM). The PING-M instrument is developed jointly by the Moscow Engineering Physical Iinstitute and the Ioffe Institute for the mission “Interhelioprobe”. The operation of the device is based on Compton scattering. The degree and direction of linear polarization are determined by measuring the asymmetry of the scattered radiation field. The device uses active scatterers that register the Compton recoil electron. A useful event is the case when two impulses in the detector-scatterer and in the detector-receiver of scattered radiation coincide. The physical model represents the detector part of the polarimeter. It contains three scatterers and six receivers of scattered radiation – a total of 18 pairs of detectors oriented at different azimuthal angles. As a result of the experiments, the dependences of counting rates in pairs of detectors on the positional angle of the polarization plane of the incident radiation were measured. The modulation depth of this dependence determines the sensitivity of the device to the polarization degree. The sensitivity of the device is estimated.
The nature of the storm activity in the northwest Atlantic during the Holocene and its possible connection with variations in the Earth’s magnetic field
Authors: Vasiliev S S , Dergachev V A
Published: December 2020

The data on the concentration of ions in the core of the Greenland Ice Sheet Project 2 (GISP2) were analysed to find the cause of storm activity in the north-west Atlantic during the Holocene. It was shown that there is cyclical transfer of ionic components with a period of ∼ 2700 years due to changes in storm activity. As a possible cause of storm changes, secular variations in the position of the geomagnetic pole over the past several thousand years have been considered. In particular, the periodicity of fluctuations in the longitude of the north geomagnetic pole was compared with the frequency of intensification of storm activity. It has been demonstrated that the spectra of these variations are similar, from which it is concluded that secular variations in the magnetic field are the basis of the processes that determine the variability of storm activity and climate in the north-west Atlantic during the Holocene.
Quasi-periodic oscillation of the γ-ray burst GRB 190114C
Authors: Dranevich V A , Dmitriyev P B
Published: December 2020

The data obtained by the BAT γ-ray telescope on board the SWIFT satellite in the energy range of 15-350 keV with a time resolution of 64 ms were used to study the temporal structure of the γ-ray burst GRB 190114C emission by means a modified spectral analysis technique. The analysis revealed quasi-periodic fluctuations with main periods of 3.84 s and 2.24 s. Both oscillations start simultaneously, continue throughout of the burst, and are equally modulated. Based on this evidence, it can be argued that all three episodes of the burst were controlled by one “central engine”.
Beam-plasma instability, the features of HXR spectra and polarization in solar flares
Authors: Charikov Yu E , Kudryavtsev I V
Published: December 2020

A one-dimensional quasi-linear beam relaxation leads to the formation of a plateau-like electron distribution function. Of greatest practical interest is the case when the initial velocity of the beam v0 greatly exceeds the thermal velocity of the plasma electrons VT, and the initial velocity spread in the beam ∼Δv0 is small compared with v0. These conditions are usually met for solar flares. The article deals with the features of the energy spectra and polarization of hard x-ray radiation (HXR) in the energy range of 20 -150 keV generated by electrons with a plateau-like electron distribution function. Calculations in the framework of a thick target take into account not only the energy losses of electrons interacting with plasma particles, but also changes in their angular distribution. It is shown that the break down energy of the electron spectrum leads to changes in HXR spectra, as well as the degree of linear polarization. There is a characteristic softening of the spectrum near the break-down energy. HXR polarization increases with quanta energy and can reach tens of percent.
Measurements of the 277 nm photon detection efficiency of the OnSemi MicroFJ-60035 silicon photomultiplier
Authors: Bogdanov A A , Tuboltsev Yu V , Chichagov Yu V , Losev S N , Sokolovskii G S , Krassilchtchikov A M , Kholupenko E E
Published: December 2020

The article describes a method for absolute calibration of the photon detection efficiency of the OnSemi/SensL MicroFJ-60035 silicon photomultiplier by the Newport Power/Energy Meter 841-PE with the 883-UV photodiode sensor head, and the PicoQuant PLS-270 fast diode source of 277 nm ultraviolet emission. The dependences of the power of the detected emission and the number of ultraviolet photons on the distance to the source were obtained. The photon detection efficiency of the silicon photomultiplier was measured to be approximately 8% compared to the 9.6% level claimed by the manufacturer. It was also shown that, within the experimental setup, absorption of the 277 nm emission at paths in the air shorter than 1 m is not significant, and the angular distribution of the emission source is homogeneous. The obtained three-dimensional calibration surface of the dependence of the irradiance on the distance to the detector and the source intensity will be employed for development of a novel camera of the TAIGA-IACT telescope array.
Creation of a theoretical simulation model of orbital referencing of lunar objects’ optical observations taken by space lunar satellite to the selenocentric coordinate system
Authors: Andreev A O , Nefedyev Y A , Nefediev L A , Demina N Y , Bagrov A V , Petrova N K , Zagidullin A A
Published: December 2020

This paper aims at the creation of a selenocentric catalogue of lunar objects’ positions (SCLOP) and development of a theoretical simulation model of orbital referencing of lunar objects taken by space lunar satellite to the selenocentric coordinate system defined by SCLOP. The data produced by the modern space lunar missions serve as the basis for multi-parameter and highly accurate digital simulation model. The results obtained in the work are important and relevant for the development of navigation technologies on creation and orienting of coordinate systems and the study of celestial bodies’ figures. To solve the problems stated in this work, the following new results are produced: a) reliability of coordinate data in modern systems of coordinate and time support for lunar objects is investigated by the robust analysis; b) a method and a software complex for transforming selenographic coordinates (TSC) are developed; c) the software package is tested for work with navigation data and determining planetary parameters; d) a method of adaptive regression modeling (ARM) for transforming coordinate systems and assessing structures and parameters of the selenocentric system (SS) is created; e) an algorithm of multi-parameter identification of SS based on ARM-approach is developed to carry out works on expansion and estimation of the reference selenocentric system; f) a global dynamic selenocentric system is constructed on the basis of optical observations taken at “Clementine”, “LRO”, and “Apollo” missions; g) as a result, a simulation digital model of orbital referencing of lunar objects optical observations, taken by star sensors of lunar satellite and on-board laser interferometer, to the selenocentric coordinate system is developed.
The analysis of Venus’ physical surface using methods of fractal geometry
Authors: Morena Carlos De La , Andreev A O , Nefedyev Y A , Akhmedshina E N , Nefediev L A
Published: December 2020

In this paper, the work on investigating fractal structures on Venus was performed on the basis of observations taken by the “Magellan” spacecraft (NASA). The uncertainties in some data produced by “Magellan” were filled by the information that had been collected before – in “Venera 15”, “Venera 16”, and “Pioneer” missions. During the implementation of the work a digital map of Venus’ surface was built, and its spatial model was created. It is worth noting that the choice of basic level surface on Venus is defined by a certain value of potential or a point on its surface through which the geoid passes. The model of Venus’ physical surface was created use the harmonic expansion into spherical functions of altimetry data the “Magellan” mission. In the present paper, for determining and analyzing fractal dimensions the Minkowski mathematical algorithm, which is a simplified option of Hausdorff-Besicovitch dimension and provides high reliability and accuracy, was used. As a result, fractal correlations of Venus’ geoid anomalies in both longitude and latitude as well as the mean value of fractal dimensions were calculated. The following values of mean fractal dimension for Venus surface are obtained: in latitude – Dβ = 1.003; in longitude – Dλ = 0.98. Based on these values, we may conclude that the topographic model of Venus’ physical surface is close to spherical figure. The comparison between the obtained Venus fractal parameters with the ones of the Earth shows the good agreement.
The study of models of space selenophysics using multi-parameter analysis and fractal geometry
Authors: Churkin K O , Andreev A O , Nefedyev Y A , Nefediev L A , Hudec R , Bagrov A V , Demina N Y
Published: December 2020

In this work, using multi-parameter harmonic analysis and expansion of altimetry into spherical functions, models of the Moon’s physical surface (digital lunar selenocentric map - DLSM) are built, and a comparison of similarity of chosen local areas of the complex lunar structure is performed. The constructed DLSM have radius-vectors of the surface points in accordance with the space measurements taken. As result, the averaged fractal dimension of the selenocentric surfaces profiles models was found to 1.345. The similarity and difference parameters were determined by the author’s method using fractal similarity coefficients. The analysis of macrosurfaces based on multi-parameter and fractal methods for the selenocentric models built in this work has not been conducted before.
Evaluating MHD parameters of relativistic shock waves with particle-in-cell modeling
Authors: Romansky V I , Bykov A M , Osipov S M
Published: December 2020

Relativistic plasma outflows are observed in gamma-ray burst sources, jets of active galactic nuclei, pulsar wind nebulae and supernovae explosions. Magnetohydrodynamical (MHD) shock waves inevitably result from interactions of such relativistic outflows with the ambient interstellar matter. The widely used single-fluid MHD description of relativistic shock waves is the main tool to study the global structure of such objects. However, to justify the validity of the global MHD models and to interpret the observed emission spectra of space objects with relativistic shocks, a kinetic description of electrons, positrons, and ions at microscales is needed. We model a plane relativistic shock propagating transverse to a regular magnetic field in the electron-ion plasmas with imposed turbulent fluctuations in the shock upstream. Namely we study the effect of the micro-scale plasma processes on macroscopic parameters of the mildly-relativistic shocks as the adiabatic index of the relativistic fluid in the shock downstream. The adiabatic index is a macroscopic parameter of the single-fluid MHD models commonly used for shock modeling at much longer hydrodynamical scales and it is especially important for the MHD modeling of the mildly-relativistic shocks.
The study of near Earth objects and meteor showers
Authors: Sergienko M V , Sokolova M G , Andreev A O , Nefedyev Y A
Published: December 2020

In this work, the physical parameters of near-Earth objects (NEO), i.e. small celestial bodies crossing the Earth’s orbit, are investigated. First of all, the study of NEO, whose number exceeds 15 thousand, is important in terms of asteroid threats. NEO are mainly stony and iron, but also could be comet nuclei that had lost the icy component under the influence of solar radiation. As a result of analyzing 14800 near-Earth asteroids from the Apollo group, in this work near-Earth objects closely genetically related to the existing meteor showers are determined. 2002LV and 2001MG1 asteroids are the closest to the Kappa-Cygnids by orbital elements. 2014RS17, 2006BF56, 2001YB5 asteroids are the closest to the Delta-Cancrids by orbital elements. 2008VL14, 2006UF17, 2010VF, 2000DO1, 2010CF55, 2010TN55, 2007EJ88, 481482 2007CA19 asteroids are the closest to the Virginids by orbital elements. The D-criterion method was used in the analysis.
Fluid–structure interaction modelling of the venous valve with elastic leaflets
Authors: Tikhomolova L G , Gataulin Y A , Yukhnev A D , Rosukhovskiy D A
Published: December 2020

The paper presents the results of a numerical study of the flow in a symmetric model of a healthy popliteal venous valve with different leaflet elasticity. The focus is on the analysis of the stagnant area under the valve leaflet. The stagnant area under the valve leaflet, as well as behind the valve, is of great practical interest to phlebologists in terms of the possibility of blood clots. The flow in the constructed simplified model of the venous valve gave good qualitative agreement with the clinical ultrasound data for a leaflet with Young modulus of 1.2 MPa.
Elastomer planar device for nucleic acids extraction
Authors: Germash N N , Esikova N A , Afonicheva P K , Antifeev I E , Petrov D G , Evstrapov A A
Published: December 2020

In this paper a device that provides the nucleic acids extraction and loading into a microfluidic chip for subsequent analysis by amplification methods was performed. The device is made by soft lithography from Silastic T4. The mechanical properties of the material (Young’s modulus) and the contact angle after Ar plasma treatment were studied. The strength of the connection of the device elements was evaluated. The device usability was checked by nucleic acids extraction from E.coli samples and using model solutions of the GAPDH gene cDNA.
Dispersion-compensated waveguide for difference-frequency generation in quantum-cascade laser
Authors: Savchenko G M , Sokolovskii G S
Published: December 2020

The waveguide structure of a semiconductor quantum-cascade laser is presented, which provides compensation of material dispersion of the refractive index. This structure can be used to generate radiation with a frequency of 1.4 THz due to nonlinear light conversion.
Proton irradiation effects on GaN-based epitaxial structures
Authors: Lebedev A A , Davydov V Yu , Smirnov A N , Eliseyev I A , Davydovskaya K S , Zavarin E E , Zakheim D A , Lundin W V , Nikolaev A E , Sakharov A V , Tsatsulnikov A F , Zubov A V , Kozlovski V V
Published: December 2020

Radiation hardness of different types of GaN based epitaxial structures which can be used as elements of electronic devices is studied by Hall effect,CV and IV measurements, as well as photoluminescence and Raman scattering. It is shown that proton irradiation leads to formation of deep acceptor states reducing conductivity of high electron mobility transistors (HEMTs) and Si-doped layers and is accompanied by a redistribution of the defect-related lines in the photoluminescence spectra. Our results demonstrate that proton irradiation increases conductivity for GaN:C, while decreases it for GaN:Fe and GaN:(Fe+C) layers.
Explicit isometric embeddings of pseudo-Riemannian manifolds: ideas and applications
Authors: Sheykin A A , Markov M V , Fedulov Ya A , Paston S A
Published: December 2020

We study the problem of construction of explicit isometric embeddings of (pseudo)-Riemannian manifolds. We discuss the method, which is based on the idea that the exterior symmetry of the embedded surface and the interior symmetry of its metric must be the same. In case of high enough symmetry of the metric such method allows transforming the expression for induced metric, which is the one to be solved in order to construct an embedding, into a system of ODEs. It turns out that this method can be generalized to allow the surface to have lower symmetry as long as the above simplification occurs. This generalization can be used in the construction of embeddings for metrics, whose symmetry group is hard to analyze, and the construction of the isometrically deformed (bent) surface. We give some examples of the application of this method. In particular, we construct the embedding of spatially-flat Friedmann model and isometric bendings of a sphere, 3-sphere, and squashed AdS universe, which is related to the Godel universe.
Explicit isometric embeddings of black holes geometry with non-singular matter distribution
Authors: Kapustin A D , Paston S A
Published: December 2020

The work is devoted to the construction of explicit embeddings for the metrics of the black holes, formed by nonsingular matter distribution. One of the possible examples of such type of solutions is regular black holes. Using the existing classification of minimal symmetric embeddings of the Schwarzschild metric as a base, we construct embeddings for regular black holes with de Sitter interior. Another simple example is black hole, formed by collapsing homogeneous spherically symmetric cloud of dustlike matter. We discuss embeddings for two variants of such black holes -the one with the eternally existing horizon, when dust ball never leaves the interior of the horizon, and another variant with the dynamically forming horizon.
Study of instability of sapphire tubes growth by Stepanov method
Authors: Vasil’ev M G , Bakholdin S I , Krymov V M
Published: December 2020

The paper considers the experimentally observed instability of capillary shaping during the growth of thick-walled sapphire tubes by the Stepanov method. The explanation of this phenomenon is based on the theoretical model of radiative-conductive heat transfer in a crystal. An algorithm is developed for the asymptotic expansion of the problem based on the presence of two small parameters. It is shown that the spatial density of the radiation is inhomogeneous along the cross section of the tube and is maximum near its inner walls. This leads to their overheating and the meniscus separation from the inner edges of the shaper.
The limit shape of the height function in the six-vertex model with domain-wall boundary conditions
Authors: Belov P A
Published: December 2020

The height function of the six-vertex model with the domain-wall boundary conditons in the free fermion point is computed by the Monte Carlo algorithm. The numerical results are in good agreement with the analytical expression for the limit shape height function. This paper is a “warm up” for the forthcoming one, where the two-point correlation function for the height function is calculated.
The effect of the n-alkane evenness on structural phase transitions
Authors: Gureva S A , Marikhin V A , Myasnikova L P , Volchek B Z , Medvedeva D A
Published: December 2020

The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of odd tricosane C23H48 and even tetracosane C24H50 was studied by FTIR spectroscopy. The initial nuclei location of the new phase was revealed. The process of crystal structure rearrangement is initiated in the interlayers between neighboring lamellar for odd tricosane, while the nanonuclei in even tetracosane arise in the crystalline lamellas cores. Thus, the influence of the number evenness of carbon atoms in the n-alkanes chains on the first-order structural phase transition has been proved.
Incoherent grain boundaries in CuO nanowhiskers
Authors: Berminova M S , Kalmykov A E , Myasoedov A V , Sorokin L M , Dorogov M V
Published: December 2020

An array of CuO nanowhiskers have been fabricated by heating of copper coatings formed on stainless steel mesh substrate in air. Cross-sections of the nanowhiskers were studied by transmission electron microscopy. It was established that whiskers consist of two or more grains with incoherent boundaries. The mechanism of the formation of incoherent boundary is revealed. An important role of the incoherent boundaries in the formation of the nanowhiskers is discussed.
Computer simulation of three-layer ferromagnetic nanosystems in magnetic field
Authors: Belim S V , Belim S S
Published: December 2020

A computer modelling of magnetization behavior in ultrathin ferromagnetic films, divided by antiferromagnetic film is carried out. The exchange integral value is different for each ferromagnetic films. One of the films is magnetohard, the second one is magnetosoft. The situation where magnetosoft film has the exchange integral value twice smaller than the value of magnetohard film is investigated. Heisenberg model is used. Calculations are made using Metropolis algorithm. The phase transition temperature is obtained for all three films. The magnetic field was applied along the film plane. The simulation showed that magnetizations of ferromagnetic films first become perpendicular to the direction the staggered magnetization vector in the antiferromagnetic film. With a higher magnetic field value, the magnetization vectors of the ferromagnetic films become mutually perpendicular. Thus, in these multi-layer systems, it is possible to control the orientation of the substances spins, which is an important property for implementing spintronics devices.
Investigation of the influence of the nano-nuclei habit on the specifics of phase transitions in long-chain molecular crystals and polymers
Authors: Borisov A K , Egorov V M , Marikhin V A
Published: December 2020

The thermodynamic parameters of a long chain molecular crystals (LCMCs) set are analyzed. We revealed the dependence of LCMC’s melting points with a different chain length on the habitus of the first-order phase transition’s elementary volume. It was shown that LCMCs with the same chemical structure of the “core” (normal alkanes {CH3(CH2)nCH3}, normal alkanols {CH3(CH2)nCOH}, diols {COH(CH2)nCOH}, carboxylic {CH3(CH2)nCOOH} and dicarboxylic {COOH(CH2)nCOOH} acids) lose their individual thermodynamic properties and approach the properties of polymethylene with an increase in the number of –CH2– groups.
Investigation of optical and structural properties of three-dimensional InGaPAs islands formed by substitution of elements of the fifth group
Authors: Andryushkin V V , Gladyshev A G , Babichev A V , Kolodeznyi E S , Novikov I I , Karachinsky L Ya , Nevedomskii V N , Egorov A Yu
Published: December 2020

We propose a new method to obtain the three-dimensional quantum-sized object arrays with reduced surface density. These arrays are formed by elastic transformation of the InGaPAs layer grown on the GaAs surface. We present the results on influence of the InGaP layer thickness, the substrate temperature, and exposure time in the arsenic flow on the optical and structural properties of the formed three-dimensional islands.
Effect of the composition and temperature of the subphase on the surface potential of the Langmuir monolayer of 8CB liquid crystal
Authors: Begletsova N N , Mironyuk V N , Santer S , Smirnova A I , Usol’tseva N V , Glukhovskoy E G
Published: December 2020

The effect of the composition and temperature of the subphase on the effective dipole moment of the Langmuir monolayers of a liquid crystal 4-n-octyl-4’-cyanobiphenyl on the surface of pure water and an aqueous solution containing copper nanoparticles was studied. It is shown that the presence of nanoparticles in the subphase leads to increase of the area occupied by the monolayer in the condensed state, increase of the collapse pressure, and reduce of the surface potential at the end of monolayer compression. The effective dipole moments of liquid crystal molecules were calculated for monolayers formed under various conditions.
Features of hydrogen diffusion through an amorphous Fe92Si6B2 alloy membrane
Authors: Pluzhnikova T N , Fedorov V A , Balybin D V , Berezner A D , Fedotov Yu D , Pluzhnikov S N
Published: December 2020

In this work, the hydrogen diffusion through an amorphous Fe92Si6B2 alloy membrane has been investigated. It has been established that the hydrogen diffusion decreases with the growth of the acidity of the environment at the constant ionic force of solution. The probable mechanisms of the blocking of hydrogen flow through the membrane have been discussed. An insignificant variation of the mechanical characteristics (ultimate tensile strength, microhardness, Young’s modulus) of Fe92Si6B2 amorphous alloy has been detected.
Improvement of single walled carbon nanotubes layer conductivity by texturing
Authors: Mitin D M , Vorobyev A A , Raudik S A , Mozharov A M , Nasibulin A G , Mukhin I S
Published: December 2020

This work is aimed at finding and developing new ways to improve and optimize the characteristics of transparent conductive electrodes based on SWCNT by forming a texture in a continuous layer by combination of lithography and oxygen plasma treatment. A theoretical and an experimental justification for choosing thickness of a textured pattern, together with the experimental results of optical and electrophysical measurements were presented. The resistance of the textured electrode was 187.5 Ohm/sq, which is 17.5% lower than resistance of the electrode made from a continuous SWCNT layer with a same transparency of 95%. An analytical calculation showed that the use of extremely absorbing SWCNT films for texturing allows to obtain ∼ 54% gain in the resistance of a textured electrode compared to a continuous SWCNT’s layer.
Light-activation of gas sensitive layers based on zinc oxide nanowires
Authors: Nalimova S S , Ryabko A A , Maximov A I , Moshnikov V A
Published: December 2020

In this work, a sensor layer based on zinc oxide nanowires was synthesized by low-temperature hydrothermal method. The gas sensitivity of sample to isopropyl alcohol vapor was studied both during heating and under ultraviolet radiation. It was shown that depending on the presence of moisture on the surface of zinc oxide nanowires, isopropyl alcohol vapor can act as a reducing or oxidizing gas upon activation of gas sensitivity by ultraviolet irradiation. It was shown that there is an optimal intensity of irradiation, which determines the maximum response of sample. The gas sensitivity under moist air conditions demonstrates the possibility of practical application of adsorption resistive gas sensors with light-activation at room temperature.
Raman scattering and low-frequency noise in epitaxial graphene chips
Authors: Eliseyev I A , Usikov A S , Lebedev S P , Roenkov A D , Puzyk M V , Zubov A V , Makarov Yu N , Lebedev A A , Shabunina E I , Dementev P A , Smirnov A N , Shmidt N M
Published: December 2020

Graphene is considered as a promising candidate for manufacturing of sensors due to its extreme sensitivity to molecule absorption. In this work, we show the connection between the electrical and optical properties of epitaxial graphene chips grown on 4H-SiC and intended for the production of protein-based sensors. Using of a complex of techniques, including Raman spectroscopy, atomic force microscopy, Kelvin probe microscopy, study of I-V characteristics and low-frequency noise, it is shown that the character of frequency dependence of the spectral density of voltage fluctuations and its value at a frequency of 1 Hz can be used for classification and selection of graphene chips for their application as sensors. Classification of the graphene chips will allow more efficient development of graphene-based biosensors.
Comparative analysis of proton production as a function of quark content and collision geometry
Authors: Larionova D M , Berdnikov A Ya , Berdnikov Ya A , Kotov D O , Mitrankov Yu M
Published: December 2020

Quark gluon plasma (QGP) is one of the most discussable objects in modern particle physics. One of the ways to study QGP is to measure production of different particles in various relativistic ion collisions. Nuclear modification factors (Rab) for protons were previously measured in symmetric Au+Au collisions at

s

N
N

= 200 GeV and U+U collisions at

s

N
N

= 200 GeV. Asymmetric Cu+Au system in comparison with Au+Au results allows to study the influence of collision geometry on proton production. This report presents invariant transverse momentum (p
T) spectra, Rab values of protons obtained in Cu+Au collisions at the energy of

s

N
N

= 200 GeV and U+U collisions at

s

N
N

= 200 GeV and the results of comparative analysis of proton (three valence quarks) and φ, π0-mesons (quark antiquark pairs) production as a function of quark content and collision geometry (Cu+Au and Au+Au).
X-ray spectral studies of calcium copper titanates
Authors: Nekipelov S V , Zhuk N A , Mingaleva A E , Petrova O V , Sivkov D V , Sivkov V N
Published: December 2020

XPS and NEXAFS spectroscopy were used to study calcium copper titanates (CCTO) solid solutions doped with iron and nickel atoms. The CCTO compound spectra analysis shows that titanium atoms have +4 charge state, and copper and calcium atoms – +2, and their valency does not change when doped with iron and nickel atoms at the concentration of the latter up to 6 atomic percent. In this case, doping atoms are mainly embedded into the positions of titanium atoms and have Fe 3+ and Ni 2,5+ charge states.
Control of topological structure of solitons in a laser with saturable absorption
Authors: Rosanov N N , Fedorov S V , Veretenov N A
Published: December 2020

We present a theoretical and numerical investigation of effect of a weak coherent holding radiation on transverse field structures in a wide-aperture laser with fast saturable absorption. In the absence of the coherent driving, the laser is able to support various types of “free” bright solitons. We show that even weak driving can control their topology making the scheme promising for topologically protected information processing.
OV-bearing modes with ℓ = 2 of twisted anisotropic optical fibres
Authors: Alexeyev C N , Barshak E V , Vikulin D V , Lapin B P , Yavorsky M A
Published: December 2020

We investigated the high-order mode structure of a weakly guiding twisted anisotropic optical fibre. An analytical solution of the vector wave equation for this case is presented. We obtained analytical expressions for the higher-order modes with an azimuthal number ℓ = 2 and their propagation constants of such a fibre, considering the mutual effect of linear anisotropy of fibre’s material, twisting, including torsional mechanical stress, and spin-orbital interaction. We showed that optical vortex beams with topological charge ±2 are the modes of the fibres considered.
Change of the defects density distribution profile over the area of the InGaN/GaN light-emitting heterostructures during current tests
Authors: Frolov I V , Radaev O A , Sergeev V A
Published: December 2020

A method for measuring of the defects density distribution profile over the area of the LED chip is presented. Using the blue commercial LEDs as an example, it is shown that the emission power decreases when LEDs testing under the increased density pulsed current for 190 h. The decrease of the LEDs emission power is accompanied by a change in the defects density distribution profile. It was determined that during the degradation process a non-uniform increase in the defects density occurs in various regions of the heterostructure: in regions with a higher defect density, the increment in the density of defects is larger.
Thermal quantum efficiency droop in blue InGaN/GaN LEDs
Authors: Shabunina E I , Chernyakov A E , Ivanov A E , Kartashova A P , Talnishnikh N A , Shmidt N M , Zakgeim A L
Published: December 2020

The contribution of several mechanisms to the external quantum efficiency (EQE) droop in blue InGaN/GaN LEDs occur at different current densities j and voltages in MQWs situated inside and outside of a depletion region around p-n junction. It is clarified that an increase in EQE droop at 300-400 K (j < 10 A/cm2) is due to non-radiative losses related to an enhancement in trap-assisted tunneling. It is also associated with a growth in the concentration of delocalized carriers. The main source of the EQE droop under direct current and at pulse mode when j > 30 A/cm2 is non-equilibrium filling of lateral regions of different size within MQWs placed outside of depletion region by delocalized carriers activated by injection when voltage exceed a threshold value (U > Uth). This leads to a decrease in localized potential and to the blue shift of EQE maximum over wavelengths followed by the EQE droop.
Numerical simulations of power characteristics and emission spectra of InAs(Sb)-based mid-infrared LED structures
Authors: Lipnitskaya S N , Semakova A A , Bazhenov N L , Mynbaev K D
Published: December 2020

Numerical simulations of power characteristics and emission spectra of LED structures with the active layer made of InAsSb with InSb molar fraction 0, 0.06 and 0.15 were performed. A satisfactory agreement between the modelled and experimentally recorded electroluminescence spectra was achieved for all the structures studied. The results of the modelling of the power characteristics showed very good design of the heterostructures in respect to carrier concentrations in their layers. Still, the results of the simulations predict that in theory the power of the studied LEDs can be enhanced by almost an order of magnitude.
Room temperature mid-IR two-color photodiodes with InAs and InAs0.9Sb0.1 absorbing layers
Authors: Klimov A A , Kunkov R E , Lukhmyrina T S , Matveev B A , Lebedeva N M , Remennyi M A
Published: December 2020

Narrow gap heterostructures consisting of two double heterostructures (N-InAsSbP/n-InAs/P-InAsSbP and P-InAsSbP/n-InAs0.9Sb0.1/N-InAsSbP) grown sequentially onto a n+-InAs substrate and further processed into a two-color photodiode with individual sensing operation at 3.3 and 4 have been studied. Presented and discussed are the photodiode construction details, I-V characteristics as well as sensitivity and detectivity spectra measured at room temperature.
Kinetic laws of the thermovoltaic effect in semiconductor structures based on samarium sulfide
Authors: Grevtsev M A , Kazakov S A , Havrov G D , Kazanin M M , Sharenkova N V , Solov’ev S M , Shulman S G
Published: December 2020

The experimental data on the thermovoltaic effect in bulk samples of samarium sulfide (SmS) are considered in this work in accordance with the represented kinetic model. The kinetic laws of the elementary process of samarium ions ionization have been studied, expressions are obtained for both the dynamics of the ionization process and the process statics in the context of the law of mass action in bulk samples of samarium sulfide. Such a description of the thermovoltaic effect made it possible to obtain the current-voltage characteristics of the samples at a constant temperature. All basic parameters were obtained for the thermovoltaic generator being developed: short circuit current and open circuit voltage; the internal resistance of the generator as well as the maximum power dissipation at the found load resistance was determined by calculation.
Thermal processes in SmS/Sm1-xGdxS heterostructures at the thermovoltaic effect
Authors: Solov’ev S M , Sharenkova N V , Kazanin M M , Kamenskaya G A
Published: December 2020

Thermal processes in SmS/Sm1-xGdxS heterostructures are investigated. It is noted that cooling is observed on the Sm1-xGdxS side when these heterostructures are heated. Cooling value is less than that of previously observed in SmS, but the stability is higher. It is shown that the main factor influencing the cooling effect is the collective casting of electrons into the conduction band from impurity levels. There are two multidirectional electron flows as a result of this fact - due to the thermovoltaic effect and due to the Seebeck effect.
Formation of SiO2 hard mask using dry etching and nanosphere lithography
Authors: Vyacheslavova E A , Morozov I A , Kudryashov D A , Gudovskikh A S
Published: December 2020

The features of the formation of a SiO2 hard mask using dry etching and nanosphere lithography are considered in the paper. A series of experiments was carried out using a variation of plasma etching parameters such as ICP and RF power, pressure as well as a substrate temperature. As a result, optimal parameters were found to obtain both good selectivity and high etching rate.
Photovoltaic converters with quantum objects under laser flux of subband photons
Authors: Panchak A N , Mintairov S A , Mintairov M A , Salii R A , Kalyuzhnyy N A , Nakhimovich M V , Shvarts M Z
Published: December 2020

Quantum objects in the host material of photovoltaic converters can expand the spectral sensitivity to the long-wavelength spectral region. Samples with InAs quantum dots and thin layers in the host GaAs material were studied theoretically with the assumption of high-power laser subband irradiation input. Threshold factors have been established that affect the possibility of radiation heating. For noticeable increase in the temperature of the base material the necessary illumination values were estimated.
Efficiency enhancement in planar perovskite solar cells under low-light illumination and ambient lighting
Authors: Kozlov S S , Alexeeva O V , Nikolskaia A B , Vildanova M F , Shevaleevskiy O I
Published: December 2020

Hybrid organic-inorganic perovskite solar cells (PSCs) have attracted significant interest owing to their high power conversion efficiency (PCE) and low cost. Moreover, PSCs demonstrate high performance under low light illumination without significant reduction in PCE. However, photovoltaic properties of PSCs under low light conditions are rarely reported. Here, the potential of planar PSCs for efficient performance under low illuminance conditions was investigated. Planar perovskite solar cells with FTO/c-TiO2/c-SnO2/CH3NH3PbI3/Spiro-MeOTAD/Au architecture were studied under variable illumination intensities in the range of 10 – 1000 W/m2. Significant enhancement in PCE up to 18.4% was observed for planar PSCs under low light conditions (<100 W/m2), as compared to the 16% PCE value obtained under AM1.5 illumination. This was attributed to the decreased charge accumulation at the ETL/perovskite interface and increased charge collection efficiency under low light illumination. PSCs performance was additionally studied under artificial LED lighting (5500K, 1000 lux) and the PCE values exceeding 24% were obtained. The results of this work verify excellent low-light performance of planar PSCs and provide the possibility for their application as power sources for various low-power wireless devices (sensors, detectors, Internet of Things devices, etc.).
Connecting the numerical and analytical ionization times for quantum dots in semiconductor wires driven by alternating field
Authors: Khomitsky D V
Published: December 2020

Recent numerical results for ionization of quantum dots by periodic electric field during the electric dipole spin resonance are compared with known analytical approaches. It is found that in finite-length quantum wires the numerical ionization rate is slower than the analytical one, especially for low driving field when the confinement potential strongly affects the dynamics. Still, the analytically predicted ionization times are in satisfactory correspondence with mean energy threshold times when the energy crosses the border between localized and continuum states.
Transonic flow bifurcations over a double wedge
Authors: Kuzmin A.
Published: December 2020

Inviscid and turbulent airflows over a symmetric flat-sided double wedge are studied numerically. Solutions of the Euler and Navier-Stokes equations are obtained with a finite-volume solver on fine meshes. The solutions demonstrate both symmetric and asymmetric flow regimes in significant bands of the free-stream Mach number at zero angle of attack. The realization of a certain regime depends on the time history of boundary conditions. A physical interpretation of transitions between the symmetric and asymmetric flows is suggested.
On plasma neutralization of the ion beam
Authors: Shalenov E O , Dzhumagulova K N , Ramazanov T S , Tikhonov A , Kaikanov M
Published: December 2020

Simulation of the thermal motion of ions in a spherical bunch was performed on the basis of the molecular dynamics. The Yukawa potential was used to describe the ion interactions. Obtained data showed good agreement with results of theoretical investigation. The conclusion was done that INURA accelerator needs good plasma neutralization in order to keep transverse size of the ion beam.
Influence of increased magnetic field on Alfvén eigenmodes on upgraded spherical tokamak Globus-M2
Authors: Balachenkov I M , Petrov Yu V , Gusev V K , Bakharev N N , Bulanin V V , Varfolomeev V I , Dyachenko V V , Zhiltsov N S , Kiselev E O , Konovalov A N , Krikunov S V , Kurskiev G S , Minaev V B , Patrov M I , Petrov A V , Ponomarenko A M , Sakharov N V , Telnova A Yu , Shchegolev P B , Yashin A Yu
Published: December 2020

During modernization of the Globus-M tokamak, toroidal magnetic field and plasma current were increased, and a number of diagnostics were upgraded, which made it possible to study phenomena associated with the excitation of Alfvén waves in a spherical tokamak in a wider range of plasma parameters. In the experiments with neutral beam injection, the dependences of fast particle losses initiated by the toroidal Alfvén eigenmodes (TAE) on their magnitude in the magnetic field range of 0.4 – 0.7 T and currents of 180 – 330 kA were acquired. Resulting dependences confirm previously obtained results and indicate a decrease in losses with increasing magnetic field and plasma current. At the same time, a number of new phenomena, that have never been observed on Globus-M were detected. In experiments with neutral beam injection at the current ramp up stage, Alfvén cascades (AC) in the frequency range of 100 – 300 kHz were observed for the first time. By means of the Doppler backscattering diagnostics (DBS), it was shown that ACs are localized closer to magnetic axis unlike TAE. Also, during low hybrid wave current drive (LHCD) experiments, global Alfvén eigenmodes (GAE) were detected at a frequency close to 1 MHz, apparently driven in the resonance with runaway electron beam. Detected global eigenmodes are also able to arise in ohmic discharges, however, their magnitude is lower.