bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of the sensitivity of ZrO2 and ZnO layers electrochemically deposited on a quartz resonator
Authors: Lovchinov K , Alexieva G , Georgieva B , Petrov M , Gergova R , Tzoukrovsky Y , Tyutyundzhiev N
Published: February 2021

A study is presented on the sensitivity of electrochemically deposited ZrO2 and ZnO on a quartz resonator. The nanostructured ZrO2 and ZnO layers are deposited by electrochemical method on the Au electrodes of the quartz resonators. The deposition of the electrochemical layers of ZrO2 and ZnO is carried out in aqueous solution of (ZrOCl2 (5. 10-3 M) and KCl (0.1 M) for ZrO2 and (ZnCl2 (5. 10-3 M) and KCl (0.1 M) for ZnO) at 70°C and (vs SCE) using a three-electrode electrochemical cell. The structure of the ZrO2 and ZnO layers deposited on the polished surface of quartz resonator is studied by Scanning Electron Microscopy (SEM) and optical profilometry. The influence of the roughness on the ZrO2 and ZnO sorption properties is investigated. The sorption ability of the ZrO2 and ZnO layers is defined by measuring the resonant frequency shift (ΔF) of the quartz structure in the presence of different concentration of methanol, ethanol and ammonia (0 - 25000 ppm).
Effect of infrared laser irradiation on electrical conductivity and ethanol sensitivity of sol-gel ZnO thin films
Authors: Gegova-Dzhurkova R , Nesheva D , Mihailov V , Dzhurkov V , Terziyska P , Manolov E
Published: February 2021

Zinc oxide thin films are prepared by spin-coating sol-gel method. Warm air flow is used as a first step in the drying procedure during the preparation of a part of the films. Post-deposition irradiation of some films with infrared pulse laser is also applied. Spectroscopic ellipsometry, X-ray diffraction and conductivity measurements are used to get information about the influence of the laser irradiation and the usage of the warm air flow on the properties of the films. It is shown that all films are nanocrystalline and the treatment with warm air flow and laser beam irradiation improves films crystallinity and reduces their conductivity. The results are related to lower porosity and smaller amount of defects in treated films.
Effect of blocking and tunnel oxide layers on the charge trapping properties of MIS capacitors with ALD HfO2/Al2O3 nanolaminated films
Authors: Spassov D , Paskaleva A , Guziewicz E , Wozniak W , Stanchev T , Ivanov Tz , Wojewoda-Budka J , Janusz-Skuza M
Published: February 2021

Electrical and charge trapping properties of HfO2/Al2O3 nanolaminated stacks incorporated in three types of metal-insulator-silicon capacitor structures (without blocking and tunnel oxide layers; with 20 nm Al2O3 as blocking oxide and ∼3 nm Al2O3 or thermal SiO2 as tunnel layer) were investigated. HfO2/Al2O3 stacks exhibit a positive initial oxide charge, and adding of the 3 nm Al2O3 tunnel layer to the capacitor doubles the amount of the positive charge and the density. Using SiO2 as a tunnel layer resulted in a negative initial oxide charge which is interpreted by the effect of dipole formation at the Al2O3/SiO2 interface. Tunnel SiO2 provides lowest density of the interface states at silicon and leakage currents. The insertion of blocking and tunnel oxide layers to the capacitors significantly widens the memory windows; capacitors with a SiO2 tunnel oxide demonstrate largest memory windows.
Influence of ZnO nanoparticles as electron transport material on the performance and stability of organic solar cells with sputtered Ag back electrodes
Authors: Gergova R , Sendova-Vassileva M , Popkirov G , Dikov Hr , Atanasova M – D , Grancharov G
Published: February 2021

ZnO has been widely used as electron selective material in P3HT:PCBM organic solar cells with either conventional or inverted architecture in order to enhance the extraction of electrons and block the collection of holes at one electrode. In this work we investigate the influence of ZnO nanoparticles electron transport layer (ETL) on the performance and stability of P3HT:PCBM based organic solar cells with conventional architecture and magnetron sputtered back Ag contacts. Their stability in the dark and under real outdoor conditions was monitored by current-voltage measurements and impedance spectroscopy. The impedance spectra were taken as a function of applied bias under illumination in order to reveal more information about the degradation mechanisms taking place in the device.
Development of Cost-efficient Wireless Network for Solar UV Irradiation Monitoring in Bulgaria
Authors: Tyutyundzhiev N , Angelov Ch , Arsov T , Lovchinov K , Nitchev Hr , Alexieva G
Published: February 2021

Human over-exposure to solar UV radiation has been identified as a serious health problem which needs intensive screening and monitoring. The goal of this study is to present recent success in solar UV irradiation monitoring in Bulgaria in the frame of INTERGA_UV project (No. KΠ 06/24H - 2018 of National Research Fund of Bulgaria). The research efforts has been focused on development of an independent on-ground UV sensors network, which uses MQTT sensor protocol, local databases and remote access to monitoring center. The developed UV monitoring system is intended to withstand severe climatic conditions at a reasonable price of equipment and components. It differs from conventional scientific instruments with an open architecture and smooth upgradability due to implementation of modern digital sensors, Arduino-based controllers and Wi-Fi communication modules. The software bridging modules are based on open-source Python applications, open-source InfluxDB database and Grafana visualization tool.
Magneto-optical characterization of ZnO / Ni nano-laminate obtained via Atomic Layer Deposition
Authors: Buchkov K , Galluzzi A , Blagoev B , Paskaleva A , Terziyska P , Stanchev T , Mehandzhiev V , Tzvetkov P , Kovacheva D , Avramova I , Nazarova E , Polichetti M
Published: February 2021

The magneto-optical (MO) properties of ZnO / Ni transition metal oxide (TMO) nano-laminate structures prepared by Atomic Layer Deposition (ALD) have been investigated. The structural (XRD) and chemical composition (XPS) analysis confirm the ZnO formation and corresponding effect of Ni incorporation in the crystal lattice. The XPS identification of Ni I2+ state, reveals also some minor traces of Ni(OH)2 inclusions. By using a MO Kerr effect microscopy, we have studied the local magnetic coercivity and its distribution and mapping of the ZnO/Ni nano-laminate sample on a microscale level. The statistical dispersion of the measured Hc
values ranges between 100 and 400 Oe (peak value of ∼ 200 Oe) with minor inhomogeneity inclusions.
Calculation of the Bandgap of Dilute Nitride GaAsSbN Alloys
Authors: Georgiev S , Donchev V , Milanova M
Published: February 2021

Dilute nitrides are semiconductor alloys, obtained from the conventional III-V compounds by incorporating a small amount of nitrogen. In this work, we focus on GaAsSbN considered as a perspective material for incorporation in multijunction solar cells. Nitrogen creates a localized level inside the conduction band continuum. The interaction of this level with the conduction band is usually described by the single band anti-crossing (BAC) model. The double BAC model of GaAsSbN considers both the N and the Sb localized levels in the conduction and the valence band, respectively. We calculate the bandgap energy of GaAsSbN employing the double BAC model for different concentrations of Sb and N. Parameters of the BAC model taken from different literature sources are used in the calculations and their influence on the final result is explored. Finally, the calculated bandgap energies are compared to experimental data of GaAsSbN layers grown on n-GaAs substrates by low-temperature liquid phase epitaxy. These data include the optical absorption edge of the material determined by surface photovoltage spectroscopy and the energy position of the photoluminescence peak at room temperature.
Development of a novel model for emptying of a self-pressurising nitrous oxide tank
Authors: Kardaś D , Szymborski J
Published: February 2021

Self-pressurised, or vapour pressurised system is a system that maintains operational pressure in ambient conditions, with no need for additional pressurisation. An example of such system is a tank filled with nitrous oxide, which keeps pressure of 50.35bar at 20°C. Self-pressurised tanks are used in hybrid rocket engines, due to low weight and simple construction. At the same time, accurate prediction of the dynamics of these systems during emptying creates a significant challenge, due to occurrence of near equilibrium two phase flow and rapid changes in pressure and temperature. The authors have developed several numerical models with aim of capturing described phenomena. The development started with basic assumption of lumped parameters approach and using mass and energy balance equations. First model featured two elements, one for the investigated fluid and second for the tank walls, with assumption of fluid in equilibrium, having single pressure and enthalpy. Such approach, while capturing major trends, lacked accuracy. To order to improve it, fluid was divided into two separate elements, one with saturated vapour and the second with the two-phase mixture. This proved to be more useful for predicting mass flow, but still did not offer accurate results. Further development included treating both fluid elements as two phase mixtures, first being mostly vapour and the second being mostly liquid and required additional equation describing tank’s internal dynamics. Resultant model allows for significantly higher pressure prediction accuracy than previously and gives better prediction of parameters of fluid flowing out of the investigated tank.
Modes for measuring aerodynamic resistances in the wind tunnel in the laboratory
Authors: Nedelcu O , Salisteanu I C , Magdun O , Dogaru V , Diaconu M
Published: February 2021

The paper is focused on the architecture and design of a wind tunnel for measurement of aerodynamical resistances. The quantities which influence the flow of fluids and the applied laws in this case are described on short. Taking into account the main criteria for wind tunnels classification (architecture, test chamber type, test chamber fluid speed) type of the tunnel will be chosen fallowed by the design and construction. Test chamber measurements are carried on by an anemometer. The physical results are compared with the modelling results obtained for ideal conditions with the aid of SolidWorks software.
Occurrence consequences of mining terrain surface discontinuous linear deformations in a residential building
Authors: Orwat J , Gromysz K
Published: February 2021

In the article a case study of consequences of underground mining exploitation of hard coal deposit on terrain surface and in a residential building has been presented. It was realized an exploitation of two hard coal seams (in three layers) in Poland, in the Upper Silesian Coal Basin, in 2013 – 2019. Operation was conducted at relatively small depth and by use of five longwalls with significant height and large decline. There were observed exploitation influences of fifth longwall on terrain surface and in the building by use of geodetic surveys. Measurements were carried out on the ground and wall points located in two perpendicular directions. Heights differences and distances between next points before and after the end of exploitation of last longwall have been measured. There the inclinations changes of particular sections have been determined. Analysis of surveys results shown that processes of the terrain and buildings deformations take place differently and terrain inclinations and building deviations have other values. Moreover, next to the building four discontinuous linear deformations of terrain surface (one in front of the building, one under the building, two behind the building) have been occurred. The ground steps location was detected by use of profile leveling of road located on the east of the building. A ground step with height of 15 cm under the building caused its crack. Example of the building with a partial basement proved that a consolidation type of building in the ground has a significant influence on values of its deviations.
Determination of the discretion interval of the temporal series of the technological process parameter measurement in ACS TP in the noises conditions
Authors: Tymchuk S O , Abramenko I G , Zahumenna K V , Miroshnyk O O , Shchur T G , Tomporowski A , Kruszelnicka W
Published: February 2021

We have solved the problem of substantiating the choice of the sampling interval of the temporal series of the technological process parameter measurements for automation systems, if there are errors, which takes into account the frequency characteristics of this series. The object of the study is the measuring channel of ACS TP (automated control systems of technological processes). We have developed the mathematical simulation model of the measuring channel and the analog-to-digital converter, which provides the possibility of studying the influence of the sampling interval value of the temporal series of technological process parameter measurements on the reliability of the information. The results of the research of the model show the effectiveness of the model developed.
Scheduling of preventive maintenance of an power equipment of the agricultural enterprises
Authors: Trunova I , Miroshnik O , Savchenko O , Moroz O , Pazyi V , Shchur T , Kasner R , Bałdowska-Witos P
Published: February 2021

Presented paper deals with the topic of preventive maintenance of an power equipment of typical agricultural enterprises. A decision support method was designed, incorporating the analysis of annual schedules of load diagrams of the typical agricultural enterprises and the planning of preventive maintenance of the power equipment with month priority during which maximal consumption of electric energy take place. The correction of typical load diagrams on the basis of the fact sheet about electric loading of the consumer is possible. The designed method optimizes maintenance costs without supplementary investment and running costs. An algorithm of the designed method is offered and a case study of its implementation is described in the paper.
Asymmetry bandwidth of stock market index time series as a warning signal
Authors: Malivuk Gak D , Rajilic Z , Stupar N
Published: February 2021

The time series of the S&P 500 index from 2003 to 2018 and the stochastic time series are considered. The asymmetry is called the change in the complexity Cmp of the time series when time direction is changing, and the values of the asymmetry of the substrings are in the interval of a certain width. The asymmetry bandwidth of the S&P 500 series is minimal for 2005, and stochastic strings can have such a small width. The 2007-2008 crisis seems to have been preceded by a rush of heightened stochasticity (a fall in predictability) that has led to a decline in investor optimism. By calculating asymmetry bandwidth, a warning signal could be obtained for a possible stock market crash.
Analysis of voice control of a collaborative robot
Authors: Janíček M , Ružarovský R , Velíšek K , Holubek R
Published: February 2021

Using the voice control to interact with things around us can always be one of the most interesting things. Voice control is becoming more and more used in everyday life, whether it is a smart home, voice control of a mobile phone or voice control of comfort equipment in a car. Whether, voice control gets into the production industry line is the right question. Reliability is still insufficient. The paper is focused on analysis of voice control of a collaborative robot. Analysis is focused on various voice commands, their repeatability and reliability in robot-human cooperation. The research determines the most problematic voice commands and ideal voice commands for voice control of a collaborative robot.
Development of the fundamental diagram of the formation and transformation of the products properties during their manufacturing
Authors: Kusyi Y M , Stupnytskyy V V , Kuk A M , Topilnytskyy V G
Published: February 2021

In object-oriented technologies of mechanical engineering production the step-by-step execution of interconnected design stages of technological process of product manufacture is used. A systematic approach to research and qualitative modelling of real physical processes, taking into account the operational characteristics of products and machines at all levels of research is ignored. As a rule, the object-oriented technological processes do not track the change of the products properties during their manufacture from the position of technological inheritability for all stages and substages of the Life Cycle Support of Product. Therefore, the development of scientific and applied principles of technological inheritability of quality parameters to provide the operational characteristics of products in the design of function-oriented technologies is a priority item of modern mechanical engineering. The structure of functional-oriented technology is closely related to the stages and substages of Life Cycle Support of Product. From the standpoint of continuous damage mechanics, Life Cycle Support of Product is considered to be a single process of exhaustion of the material plasticity margin under the influence of certain load modes in accordance with the technological inheritance of the product properties. The basic chart of the formation and transformation of the products properties from the point of view of mechanics of technological inheritability is developed. This chart, in contrast to previous research in this area, takes into account the significant impact of the stage of blanks manufacture in the technological process structure on the formation of technological parameters and operational characteristics of products.
Analysis of the Industry 4.0 key elements and technologies implementation in the Festo Didactic educational systems MPS 203 I4.0
Authors: Ružarovský R , Holubek R , Janíček M , Velíšek K , Tirian G O
Published: February 2021

Industry 4.0 is one of the key words and strategies in current industrial production. It is important to define the Industry 4.0 strategy, analyse its objectives, and characterize the key elements and technologies of Industry 4.0. The Industry 4.0 concept uses the Industry 4.0 reference architecture, which assists and guides automated system developers in their design and construction, and of course in the development of a new assembly product. Given that the existing assembly system for education - Festo Didactic MPS 203 I4.0 is used to explore the possibilities of using digitization in design, it will be necessary to analyse this system in terms of reference architecture and key elements of Industry 4.0 implemented. The result is in conclusion of how deeply the key elements of Industry 4.0 are implemented in this educational system. The aim of this result was to create a digital twin of the system and test it in a virtual environment after the verification and validation of the digital twin model.
Dual Stator Winding Induction Generator (DSWIG) used for hybrid micro grid power systems
Authors: Topor M , Deaconu S I , Bu F , Popa G N , Tutelea L N , Muntean N
Published: February 2021

This paper proposes a hybrid micro grid system for critical consumers like military disaster intervention, health or municipality. The solution is based on a multiple level of redundancy DC micro grid. The solution is projected to provide critical functionalities like stability, power quality, coordinated control, grid support capability. The configuration described here takes in consideration the problem integration of renewable energy sources which should have features like redundancy, flexibility and scalability from architecture point of view.
Tuning proportional-derivative controller for a three-phase electric arc furnace
Authors: Ghiormez L , Panoiu M , Panoiu C , Muscalagiu I
Published: February 2021

In this paper is presented a control system that is based on the proportionalderivative controller for modeling and simulation of the electric arc furnace focusing on the controller’s loop. The proposed controller is used to modify the position of the electrodes of the electric arc furnace in order to minimize the effect of the disturbances that can appear in the process during its functioning. With the proposed controller can be obtain the maximum power that can be used during functioning of the electric arc furnace. Also, the proposed control system can be used to obtain a specific active power for the electric arc that appears in the functioning of the electric arc furnace. In this paper are presented the steps used to tune the proportional and derivative gains of the controller. Used mathematical model of the electric arc is based on the voltage-current characteristic of the electric arc that simulates the functioning of the electric arc from the electric arc furnace. The model is integrated in the control system implementation. The simulations are implemented using Simulink toolbox from Matlab software. Taking into consideration obtained results during simulation are selected the best values for the gains of the proportional-derivative controller in order to obtain performance optimization of the electric arc furnace. For the selected gains of the proportional-derivative controller is presented the response of the system that is tested in a closed loop.
Some aspects regarding the implementation of a Web application in different SAP UI technologies
Authors: Berdie A D , Berdie A A , Lemle K L
Published: February 2021

Currently, in the development and implementation of an web application, the software developers are turning to those technologies that satisfy the client’s requirements, that can be easily extended and have optimal results in terms of execution time. This scientific paper addresses issues related to the development and implementation of the same application using three different web technologies, existing on the SAP NetWeaver platform. In this context, aspects related to the SAP NetWeaver technological platform and the SAP AS application server ABAP, the facilities offered by these for developing and implementing web applications, as well as the features specific to Web Dynpro ABAP, Floorplan Manager and WebClient UI technologies are highlighted.
Sea ice impact on naval operations
Authors: Novac V , Rusu E , Onea F , Stăvărache G
Published: February 2021

This paper highlights the icing regime and its impact on the primary naval operations conducted in the Black Sea basin. The article analyzes seawater’s phenomenon freezing through the perspective of merchant shipping operations and underlines the impact on undersea or surface warfare. The article figures out the impact on the ship hull, weapons systems, personnel, as well as the tactics aspects of operations or de-icing strategies when ice accrues on ship hull and equipment. The article points out associated meteorological phenomena and brings in attention the importance of meteorological and oceanographic observations in situ or by satellites as a condition for the success of the operation. In the end, the article concludes regarding shortfalls faced during icing periods and give some directions meant to curb the adversary effects of unfavorable icing environment.
The analysis of the deforming regime in the electric traction railway
Authors: Baciu I , Cunţan C D
Published: February 2021

The paper presents the results of measurements of electric power quality analyzer CA8334 on an electric locomotive equipped with continuous power engines. Determinations were made of the arrangements of current and voltage related to a motor of a locomotive 5 MVA. The data measured by the analyzer were transferred to a computer system using the Qualistar program and further processed in Excel that allows graphical representation of the characteristic quantities of power quality.
Management of the activity of quality assurance of cast iron castings in foundries
Authors: Josan A , Ardelean E , Ardelean M , Puţan V
Published: February 2021

In Romania, at present, the process of casting the parts is used under different methods. Thus, castings have different configurations and are used in various fields of technology, such as for the automotive industry, motorcycles and engines, electrical and electronics, space, computing and office equipment, agricultural machinery, aeronautics, woodworking or household industry. There is also a wide variety of materials used in casting these types of castings. The quality of the castings is found in the final product and, therefore, a special importance is attributed to the management activity to ensure the proper management of all processes in the foundry. For this, methods, techniques and management tools are used and applied so as to continuously optimize processes and activities and to be in accordance with the objectives of the system, respectively the continuous quality assurance and customer satisfaction. The paper presents the possibility of obtaining the quality of vermicular graphite cast iron castings, of the gate valve type.
Impact of contaminants on engine oil: a review
Authors: Raţiu S , Josan A , Alexa V , Cioată V G , Kiss I
Published: February 2021

Contaminants in engine oil alter its structure in different ways, depending on their nature, leading to the degradation of the lubricant and, if it is not replaced in time, even to loss of engine performance and its failure. Consequently, both for environmental reasons and from an economic point of view, it is important to be aware of the danger that these substances may present. This paper offers an investigation of the engine oil contaminants in general, emphasizing the most dangerous ones. It also includes the causes that contribute to their appearance, the types of contaminants, the way they act, the processes that result from contamination and the impact they have on engine components.
The 3D reconstruction of a road accident used the specialized program PC Crash 12.1
Authors: Dascăl A , Popa M
Published: February 2021

A modern tool used in conducting forensic and extrajudicial technical expertise is the program specialized in simulating PC-Crash road traffic accidents, which covers a multitude of different situations, as it benefits from the advantages of the latest achievements in the fields of hardware and software. The paper presents one of the possibilities of the PC Crash program for computerized reconstruction of the dynamics of a road accident, by correlating the physical possibilities of the accident, based on the laws of mechanical engineering.
Processing of ferrous iron and steel waste in the context of the circular economy
Authors: Lupu O , Socalici A , Popa E , Gaianu O
Published: February 2021

The paper presents the possibilities of exploiting the small and powdered ferrous waste with the production of lighters that can be used as a raw material in the loading of the steel processing units. The capitalization of small ferrous and powdered iron and steel wastes is an important problem, because their transformation into by-products, so in economic goods can lead to a rational exploitation of the resources of raw materials and energy, thus ensuring both the needs of the human society and the protection of the environment surrounding.
Turning a waste producer into an energy producer
Authors: Halmaciu A I , Wächter M R , Ionel I
Published: February 2021

The paper focuses on the possibility to turn waste generated by farms into biogas, which can be used for electricity and heat generation, covering own use or even more. Three case studies, all based on experiments, are presented, the first two revealing data concerning the potential energy development from the waste, as energy carrier, the third, run on a very modern lab facility, demonstrating the high potential of the manure as renewable bio-energy source. All are based on anaerobic biogas production.
The importance of indoor air quality (IAC) monitoring
Authors: Corlan R V , Balogh R M , Ionel I , Kilyeny St
Published: February 2021

Air pollution is already a global public health crisis, as it kills seven million people each year, according to the World Health Organization. Presently, a correlation between health and air pollution levels recorded in the past exists. The paper presents series of instruments concerning IAC (Indoor Air Quality) measurements and focuses on indoor air quality measurements taken in different closed spaces, as example. Based on the concentration values detected, the conclusion of the paper indicates that, depending on the technological process or activity in enclosed spaces, it is mandatory to check the IAQ. This action must be taken as prevention, in order to reduce potential health risks upon humans, acting in their homes, or schools and offices or industrial halls, in general in closed spaces, even when artificially ventilated.
Air fleet endowment using methods of decision under certainty
Authors: Balasa R , Costea M L , Andrei A G , Apostol E I , Semenescu A
Published: February 2021

This study presents how to develop the information used during the decision-making process regarding the endowment of the Romanian air fleet with fighter aircraft, where after the analysis, we have as a result the appropriate model for the requirements and criteria for modernization and reorganization of the fleet. This analysis is performed by mathematical methods under certainty by the moments method or the Deutch Martin method. The first step of the method is to normalize the consequence matrix by linear transformations. It is taken into account that the four chosen criteria are of maximum. The moments method optimally generates clear results regarding the purchase of fighter aircraft that contribute to the development of the fleet.
Impact of healthcare innovation on the population’s well-being in Russia
Authors: Arkhipova M , Rogovchenko V
Published: February 2021

The article is devoted to the study of innovative activity in healthcare and its impact on the welfare of Russia’s population, depending on the respondents’ region of residence. Inclusion of various components of the population’s well-being is based on the author’s algorithm for calculating the composite index which includes 21 indicators within 5 sub-indices. To test the hypothesis about the presence of a statistically significant relationship between the level of development of innovations in healthcare and the well-being of the population, as well as in order to highlight innovative factors that affect the well-being of the population, the classical econometric tools and machine learning methods are considered. It allows choosing the most accurate model to describe the studied process and identifying the hidden links between the well-being of the regional population in Russia and their innovative activity. The results of evaluating different models made it possible to choose the Random Forest Regression algorithm in favor of compared Linear Regression Model and the Gradient Boosting Regression technique using control on deferred data. The obtained results of the work can be used in monitoring the state and level of innovative development of the healthcare sector at various levels, in the development of regional and municipal projects and programs to improve the healthcare system.
Study of russian households income differentiation with various inequality measures
Authors: Sirotin V P , Alexeeva K V
Published: February 2021

The article reviews modern income inequality measure such that Gini index and its modification, Zenga index and Davydov, their advantages and disadvantages. The reviewed indices are applied to the household’s income data for different regions in the Russian Federation from 2014 to 2018. The indices studied showed different level of income inequality in regions compared, thus the tendency is the same – income inequality decreases for all type of inequality studied. Russian regions become more similar in terms of income inequality, while income inequality itself tends to decrease in most regions.
The use of return on equity as a criterion for stock selection in the Indian equity markets
Authors: Saha A
Published: February 2021

As per Dorsey, companies with a sustainable competitive advantage tend to outperform the market benchmarks over time. Companies which have a durable competitive advantage compared with their competitors manage to compound capital at attractive rates of return and such companies tend to grow sales and profits predictably and generate substantial free cash flows. This reflects in their share prices over time. In this paper we have used a measure of Return on Equity as an indicator that a company has a sustainable competitive advantage, and have studied the equity performance of such companies as compared with market performance. We find that companies which have attained Return on Equity greater than 15% each year for the past ten years tend to outperform the market benchmarks over the next five years.
Ab initio study of MgO under pressure using quasi-harmonic approximation
Authors: Burov A S , Minakov D V , Levashov P R
Published: February 2021

We examine the dependence of the Gibbs free energy and entropy on pressure and density along MgO isotherm 300 K. Some theoretical works have previously predicted a drastic drop of entropy along MgO isotherms by analyzing existing experimental data and extrapolating them to high pressures. We present first-principle calculations of thermodynamic properties of MgO under pressure using density functional theory and quasi-harmonic approximation. The robustness of our calculations is verified by comparing the calculated and experimental phonon dispersion curves. The comparison with available diamond anvil cell experimental data is also provided. Our estimate for the B1–B2 phase transition is in good agreement with other experimental and theoretical studies. However, our results for entropy along isotherm 300 K do not agree with previous theoretical estimates based upon the integration of thermal expansion coefficient and isothermal bulk modulus by volume.
Equations of state for CaSiO3 phases based on the Helmholtz free energy
Authors: Sokolova T S , Dorogokupets P I
Published: February 2021

Equations of state for the CaSiO3 phases are constructed using a thermodynamic model based on the Helmholtz free energy. The proposed thermodynamic formalism is allowed us to calculate the full set of thermodynamic properties of minerals in a wide range of temperatures and pressures. The proposed equations of state are constructed with a small number of fitting parameters and reliably represent the properties of studied minerals under T–P or T–V parameters.
Experimental study of thermal expansion of chromium near its melting point
Authors: Senchenko V N , Belikov R S
Published: February 2021

Experimental study of thermal expansion of chromium by millisecond pulse heating technique was performed. The results obtained allow calculating the density of Cr in the wide range of high temperatures up to the melting point.
Computation of molecular spectra and thermodynamic functions for diatomic ideal gases using interatomic potentials
Authors: Maltsev M A , Morozov I V , Osina E L
Published: February 2021

A method for calculation of the thermodynamic properties of diatomic ideal gases using interatomic interaction potentials is discussed. For instance the computation of thermodynamic functions such as heat capacity, entropy and reduced Gibbs energy in the temperature range 298.15–10 000 K is shown for diatomic argon compounds.
The effect of atomic polarization on the diffusion coefficient of oxygen ions in cubic zirconia
Authors: Savilov T M , Lankin A V , Norman G E
Published: February 2021

We study single crystal zirconia using molecular dynamics method. We calculate the diffusion coefficient of oxygen ions in the temperature range from the occurrence of diffusion at our calculation parameters to the loss of stability of the crystal. In the potential of interatomic interactions, in addition to conventional terms, we introduce into our model the interaction due to the polarization of atoms. These interactions turned out to be crucial for the correspondence between the calculations and available experimental data.
Metastable shock waves in the region of their ambiguous representation
Authors: Konyukhov A V , Levashov P R , Likhachev A P
Published: February 2021

The behavior of perturbed shocks belonging to Hugoniot segments with ambiguous representation of the shock-wave discontinuity is considered. The segments are adjacent to the region of the shock wave instability L > 1 + 2M from the side of greater and lower pressure. Here, L is the D’yakov parameter and M is the post-shock Mach number. The model equation of state is used. For the constructed Hugoniot curve, the ambiguity sections are overlapped by the shock wave neutral stability regions. The three-dimensional simulations with varying post-shock parameters and perturbation intensity are performed. It is shown that shock waves considered are metastable: for any intensity of the shock wave, there are intervals of the perturbation threshold values inside of which the shock is neutrally stable or unstable. Neutral stability is characterized by the weak damping of secondary waves occurring as result of the perturbation.
Calculation of the optimal corrugation of the plate surface for explosive welding
Authors: Shutov A V , Sultanov V G
Published: February 2021

This article suggests profiling the surface of one of the welded plates in a special way during explosion welding. The principle and method of calculating the profile of the plate based on the materials and welding speeds of the plates are given. It is assumed that such profiling of the surface of the plate will allow to obtain more durable welded joints and even perform welding at a speed below the minimum collision speed for welding plates with smooth surfaces. As an example, a full calculation of plate profiling for specific collision parameters of welded plates is given.
Laser ablation of a multilayer target with layers of nanometer thickness
Authors: Khokhlov V A , Ashitkov S I , Inogamov N A , Komarov P S , Parshikov A N , Petrov Yu V , Romashevsky S A , Struleva E V , Tsygankov P A , Zhakhovsky V V
Published: February 2021

Multilayer products made of ultra-thin layers are widely used in modern science and technology. Laser exposure is used as one of the promising methods of processing such products. In this regard, we study the ablation of a layered target. A physical model is constructed, numerical simulation is performed, and experiments are carried out. The experiments were conducted with two different lasers and various diameters of the focal spot. To estimate the absorbed energy the reflection coefficient was measured. The results of calculations and experiments are consistent with an accuracy of about 10%. This allowed us to refine the model of two-temperature states and determine the strength of nickel. It is explained why, with an increase in the absorbed fluence, first the upper layer breaks in the multilayer.
The role of geometry in the generation of a shock wave by a femtosecond laser pulse
Authors: Shepelev V V , Inogamov N A , Fortova S V
Published: February 2021

Laser exposure at a sufficient intensity creates a shock wave (SW), propagating in the irradiated target. The process is used in many technological applications. As a result of femtosecond exposure, a warmed up layer with a thickness of d
T ∼ 0.1 μm occurs. The radius of the heating spot R
L varies from values of the order of a micron (focusing on the diffraction limit) up to tens or hundreds of microns depending on the experiment. As you can see, R
L ≫ d
T, therefore one-dimensional motion with a plane surface is generated. The quasi-plane SW stage ends when the SW moves away from the target surface to a depth of about RL. Then the stage of quasi-hemispherical propagation begins. The paper analyzes the transition from plane to hemispherical SW. The motion of the “wings” of a hemispherical wave on the target surface bordering on a gas or vacuum is investigated. Theoretical estimates and numerical simulation results are presented. Analysis of the movement of the “wings” on the surface is important for experimental diagnostics of phenomena inside the target.
Electron thermal conductivity of nickel and aluminum in solid and liquid phases in two-temperature states
Authors: Petrov Yu V , Inogamov N A , Khokhlov V A , Migdal K P
Published: February 2021

Analytical expressions for the electron thermal conductivity of nickel and aluminum are presented. The thermal conductivity depends on the electronic and ionic temperatures, density and phase of the substance (solid or liquid). The expressions obtained can be used in hydrodynamic calculations of the ablation of these metals or multilayer targets made from them. We consider the case when ablation is caused by the action of ultrashort laser pulses.
Modeling of electronic and phonon thermal conductivity of silicon in a wide temperature range
Authors: Koroleva O N , Demin M M , Mazhukin A V , Mazhukin V I
Published: February 2021

In the present article, using the methods of mathematical modeling, the thermal conductivity of silicon was obtained in a wide temperature range (0.3 ≼ T ≼ 3 kK), including the region of semiconductor-metal phase transformations. As it is known, there are two mechanisms of heat transfer in a solid: elastic lattice vibrations and free electrons, therefore, in the study of the thermal conductivity of silicon, the lattice and electronic components were taken into account. The lattice (phonon) thermal conductivity in this work was determined within the framework of the atomistic approach. The Stillinger–Weber and Kumagai–Izumi–Hara–Sakai interaction potentials were used for modeling. The results of the comparison of the phonon thermal conductivity obtained from the simulation results with the used interaction potentials are presented. The modeling of the thermal conductivity of the electronic subsystem of silicon with intrinsic conductivity in this work is based on the use of the quantum statistics of the electron gas using the Fermi–Dirac integrals. The total thermal conductivity of silicon, obtained as the sum of the electronic and phonon components, is compared with the experimental data.
X-ray radiography based on the phase-contrast imaging with using LiF detector
Authors: Makarov S S , Pikuz T A , Buzmakov A V , Chernyaev A P , Mabey P , Vinci T , Rigon G , Albertazzi B , Casner A , Bouffetier V , Kodama R , Katagiri K , Kamimura N , Umeda Y , Ozaki N , Falize E , Poujade O , Togashi T , Yabashi M , Yabuuchi T , Inubushi Y , Miyanishi K , Sueda K , Manuel M , Gregori G , Koenig M , Pikuz S A
Published: February 2021

An x-ray radiography technique based upon phase contrast imaging using a lithium fluoride detector has been demonstrated for goals of high energy density physics experiments. Based on the simulation of propagation an x-ray free-electron laser beam through a test-object, the visibility of phase-contrast image depending on an object-detector distance was investigated. Additionally, the metrological capabilities of a lithium fluoride crystal as a detector were demonstrated.
Restoring size of detonation nanodiamonds from small-angle x-ray scattering of polychromatic synchrotron radiation beam
Authors: Rubtsov I A , Ten K A , Pruuel E R , Kashkarov A O , Zubavichus Ya V , Peters G S , Veligzhanin A A
Published: February 2021

Over the past two decades, LIH SB RAS and BINP SB RAS have jointly conducted experiments on time-resolved (TR) small-angle x-ray scattering (SAXS) with detonating high explosives. The purpose of these experiments is to restore the dynamics of carbon species condensation to diamond nanoparticles by analyzing series of SAXS patterns behind the detonation front measured in real time with fast detectors. This knowledge is crucial for the development of reliable detonation models. In this paper, we compare SAXS patterns of identical nanodiamond samples measured at the TR-SAXS extreme state of matter end-station (BINP SB RAS) in the static mode under realistic conditions simulating fast real-time measurements with polychromatic SR beam and traditional SAXS BioMUR beamline at the Kurchatov Synchrotron Radiation Source (NRC “Kurchatov Institute”) with monochromatic synchrotron radiation (SR) beam. These experiments confirm that the size of scattering inhomogeneities determined in dynamic experiments with single bunch exposure with polychromatic SR beam is correct.
Cell proliferation under intense pulses of terahertz radiation
Authors: Sitnikov D S , Ilina I V , Revkova V A , Konoplyannikov M A , Kalsin V A , Baklaushev V P
Published: February 2021

Terahertz (THz) waves can influence a diverse spectrum of cellular processes. In the present study, we focus on the effect of high-power broadband THz pulses on cell culture. An experimental setup for long-term irradiation of cells with THz pulses with intensities of about 32 GW/cm2 has been developed. Human skin fibroblasts were exposed to THz pulses with a field strength of about 3.5 MV/cm for 90 min. Preliminary results on the THz-induced apoptosis process in cells are presented.
Search for hadronic solar axions
Authors: Akhmatov Z A , Berezin S S , Gavrilyuk Yu M , Gangapshev A M , Derbin A V , Drachnev I S , Kazalov V V , Khokonov A Kh , Kobychev V V , Kuzminov V V , Muratova V N , Panasenko S I , Ratkevich S S , Tekueva D A , Unzhakov E V , Zavrazhnov A Yu
Published: February 2021

Resonance excitation of the 83Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism and via an M1-transition in the 83Kr nucleus in the Sun is searched. The γ-and x-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a proportional counter in the underground low-background facility of Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion-photon coupling constant and the axion mass: |g

Aγ
m

A
| ≼ 6.16 × 10−17. In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of mA
≼ 12.6 eV at 95% coincidence level (C.L.). In case of pure hadronic interaction the upper limit for axion-nucleon coupling is

|

g

AN

3

−

g

AN

0

|

≼ 8.3 × 10−7 at 95% C.L., which corresponds to upper limit for hadrionic axion mass: mA ≼ 64 eV at 95% C.L. with the generally accepted values S = 0.5 and z = 0.56.
Singularity-free stable black holes, holding the baryon conservation law in the periodic waveguided multiverse
Authors: Gribov I A
Published: February 2021

Black holes (BHs) are three-dimensional (3D) singularity-free macroscopic defects in the superfluid-crystal-like four-dimensional (4D) periodic waveguided multiverse (PWM) concept by the author, like edge-dislocations in 3D smectic-A liquid crystals. The PWM-co-emergent intrinsically identical ordinary matter (OM), antimatter (AM), dark matter (DM), dark antimatter (DAM) arise in the nearest 3D-waveguids–3D-universes with the co-emergent special relativity, weak Newtonian gravity, the expanded equivalence principle–the expanded general relativity (PWM-GR) foundation, predicting gravity mass symmetry–matter-antimatter antigravity. The PWM-BHs have identical Schwarzschild radii, outer gravity potentials as the GR-BHs, but flat-singularity-free gravity potentials inside. Microscopic PWM-fermions—singularity-free defects-holes in the weightless superfluid PWM-vacuum-medium–form singularity-free, intrinsically physically identical macroscopic defects: OM-BHs, DM-BHs, AM-BHs, DAM-BHs in the nearest 3D-waveguides. The smallest free PWM-BHs have 4.3 solar masses (excluding microscopic Hawking’s GR-BHs never experimentally detected), they are stable—too heavy for gravitational Schwinger-like virtual electron-positron pairs decoupling—unable emit gravitationally repulsive virtual positrons; they also unable emit repulsive PWM-antiphotons, electrostatically confined in the gravitationally polarized PWM-vacuum, preserving its decay, holding the fundamental baryon number conservation law, prohibiting Hawking’s-GR-BHs evaporation. Only plasma-eating, growing PWM-BHs emit thermal positrons, simultaneously absorbing attractive virtual particles. The dominating PWM-DM-pulsars explain relativistic galactic positrons flows excess over electrons.