bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid temperature dependence of the shock formation in a cavitation bubble
Authors: Aganin A.A. , Khalitova T.F.
Published: January 2018

The dependence of the radially convergent shock wave formation in a cavitation bubble on the surrounding liquid temperature TL in the range from 273.15 to 400 K is investigated at the liquid pressure equal to 50 bar. Realistic mathematical model is applied, in which the effects of the liquid compressibility, the heat conductivity of the vapor and liquid, the evaporation and condensation on the bubble surface are taken into account, wide-range equations of state are utilized. The governing equations of the vapor and liquid dynamics are solved numerically using a modification of the Godunov method of the second order of accuracy. It has been found that a radially convergent shock wave arises in the bubble in 273.15≤T_L≤375 К. In this interval, the distance between the shock wave formation position and the bubble surface decreases with decreasing the liquid temperature. The possibility of using a known simplified criterion of the formation of a shock wave inside a bubble to estimate its formation position under the studied conditions is considered. It is shown that with applying that criterion the shock wave formation position turns out to be correctly predicted at T_L≈325 К, while at T_L>325 К and T_L<325 К it is predicted closer to and more distant from the bubble surface, respectively.
Ensuring for effective use of energy resources in mobile robots group
Authors: Bogdanov D.R. , Darintsev O.V.
Published: January 2018

For the successful functioning of the robot team, the necessary condition is the availability of sufficient energy resources and the mechanism for their effective distribution within the group. Reducing the consumption of resources is planned using the optimal distribution of tasks from the point of view of energy costs, and to increase the effectiveness of the collective — thanks to the use of energy exchange mechanisms between agents. The proposed variant of the power system’s architecture for an individual robot, the algorithm of its operation and hardware are considered as the basis for the synthesis of an intelligent monitoring and managing energy supplies system, which allows the redistribution of the collective energy resources among robot-agents in accordance with the chosen behavior strategy. The main components of the being developed system are wireless energy exchange modules, an energy management system and a hardware&software complex that implements support for both individual and group management of energy flows.
The method for determination of flexoelectric coefficients of nematic liquid crystals
Authors: Delev V.A. , Skaldin O.A. , Timirov Yu.I.
Published: January 2018

A method for determining the flexoelectric coefficients of a nematic liquid crystal (NLC) is proposed. The principle of method suggested is the measurement of characteristics of flexoelectric domains arising in the a polarization-optical microscope (electro-optical method). The digitized images of these domains is used for the optical contrast K determination. Linear fitting of the contrast K depending on the applied voltage U in vicinity of the threshold of flexoelectric domain formation allows rather precisely to determine the critical voltage U_c. The spatial period of the observed domains is found by means of a two-dimensional Fourier transformation of digitized images. Using the material parameters of the NLC in the linear analysis of the basic state stability, and the difference between the flexoelectric coefficients (e_1–e_3) as the fitting parameter, the threshold characteristics (critical voltage and characteristic spatial period) of the flexoelectric domains are calculated so that they were close to experimental ones. The flexocoefficient difference chosen in this way is accepted as the wanted result.
Some details of the cooling process of bacterial suspensions
Authors: Simonov O.A.
Published: January 2018

he results of experimental studies of the cooling process of the water bacterial suspensions in a cylindrical vessel near the maximum density of water are present. Carried out direct numerical simulation of convective flow of water. Studied the flow regimes, the calculated integral parameters of the flow. Shows the influence of surface tension on the formation of flow structure, resulting in significantly changed the rate of cooling of the vessel.
A new approach to the hydraulic fracture geometric dimensions determination
Authors: Ilyasov A.M.
Published: January 2018

Based on the generalized Perkins-Kern-Nordgren model (PKN) for the development of a hyperbolic type vertical hydraulic fracture, an exact solution is obtained for the hydraulic fracture self-oscillations after terminating the fracturing fluid injection. These oscillations are excited by a rarefaction wave that occurs after the injection is stopped. The obtained solution was used to estimate the height, width and half-length of the hydraulic fracture at the time of stopping the hydraulic fracturing fluid injection based on the bottomhole pressure gauge data.
Propagation of weak disturbances in warm water with air bubbles
Authors: Vdovenko I.I. , Vdovenko N.N.
Published: January 2018

The features of reflection and refraction of harmonic waves at the interface between a ”pure“ liquid and a liquid with bubbles with a vapor-gas mixture under direct and oblique incidence are studied. A numerical analysis is made of the effect of the initial volumetric gas content αg0 for two initial bubble sizes a0=10–6 m and 10–3 m. The influence of the disturbance frequencies on the reflection and refraction coefficients of sound in direct incidence and on the dependence of the angle of refraction on the angle of incidence is studied.
Calidad de vida en adultos del Paraguay con enfermedad celiaca
Authors: Real-Delor Raúl Emilio , Centurión-Medina Ingrid Celeste
Published: January 2018

La enfermedad celiaca altera el estado emocional, las relaciones sociales, la autonomía y la percepción de la salud, afectando la calidad de vida relacionada a la salud. Los objetivos fueron determinar la calidad de vida relacionada a la salud en adolescentes y adultos con enfermedad celiaca e investigar los factores que la afectan. Se realizó un estudio observacional, prospectivo, realizado en adolescentes y adultos del Paraguay portadores de enfermedad celiaca con al menos 6 meses en dieta sin gluten. Se aplicó el cuestionario CD-QOL. Fueron incluidos 114 sujetos, con edad media 30±10 años, siendo 58% del sexo femenino. La calidad de vida fue buena en 25%, regular en 49% y mala en 26%. Los factores asociados significativamente a mejor calidad de vida fueron el sexo femenino, el grupo etario >30 años y realizar actividades fuera del hogar. Se concluye que la calidad de vida de los celiacos adolescentes y adultos es regular en 49% de los encuestados.
Responsabilidad ética del docente de enfermería en el fomento de la calidad de vida de estudiantes universitarios
Authors: González-Noguera Tatiana , Guevara-Rumbos Berta
Published: January 2018

El interés central del presente documento es reflexionar sobre la responsabilidad ética del docente de enfermería en el fomento de la salud y calidad de vida de los estudiantes universitarios, teniendo en cuenta que la enfermería es considerada una profesión que actúa en beneficio de las personas con las que tiene una relación estrecha. Fomentar una buena salud en los estudiantes es una tarea que implica deberes éticos para la sociedad, para las instituciones de educación superior, de salud y esencialmente para enfermería. El profesional en enfermería es indispensable para producir cambios en el estilo de vida de los estudiantes, a través de los derechos y deberes éticos que emanan de la dignidad y que es esencial en la enseñanza de los más jóvenes. Como docentes universitarios hay que aceptar la responsabilidad de promover estilos de vida saludables que protejan la salud de los estudiantes y por ende la calidad de vida de los futuros profesionales integrales.
Interpret Ogoh-ogoh towards Hindu Contemporary Society
Authors: Suda I Ketut , Indiani Ni Made
Published: January 2018

The interpreting of the making ogoh-ogoh based on the perspective of the cultural studies in related to the festival day of the tawur kesanga towards Hindu society in Bali. It recently is an interesting phenomenon to be studied in the academics. Due to the ogoh-ogoh is made as a series for the ceremony of the tawur kesanga lately. It has been a high cost, although, in the literary texts, it does not find the existence of ogoh-ogoh become the completeness of the tawur ceremony itself. Regarding its phenomenon, the author was interested in studying in term of this. The study was intended to interpret the ideology or a truth behind the making of ogoh-ogoh shown of the religious ceremonies. It was conducted applying a qualitative approach included classifying, categorize, understand, and interpret any data or the facts by paraphrase or description, therefore, the conclusion was generally obtained. The results of the analysis were conducted. It can be understood that the making of ogoh-ogoh recently in the Hindu society in Bali, not merely means to cast out of the evil spirits that have been perceived as buta kala by the Hindu society in Bali. However, it was interpreted as a game of the ideology i.e. capitalist ideology. In term of this was evident that the making of ogoh-ogoh lately, no longer using the local materials that can be freely gotten from the surrounding environment, but must be made by lux materials that must be purchased expensive. Thus, it can be concluded that behind the making of ogoh-ogoh related with the ceremony of the tawur kesanga towards Hindu society in Bali lately was initiated by the game of the ideology i.e. capitalist ideology.
Financial Disclosure based on Web-ICT Determinants
Authors: Hadi Ahwan , Handajani Lilik , Putra I Nyoman Nugraha Ardana
Published: January 2018

The purpose of this research is to analyze the influence of local government characteristic and accountability performance on the financial disclosure based on WEB-ICT and how it’s implications for local government financial performance as a response to the public information disclosure requirements. Using 307 regencies and cities local government in Indonesia as samples based on purposive sampling and analyze by SEM-PLS technique. The result shows that local government characteristic and accountability of local government performance has a positive influence on financial disclosure based on web-ICT. It indicates that local governments with better performance accountability levels and have greater or more mature characteristics will disclose wider financial information through the website. These findings are consistent with the signaling theory which states that organizations tend to provide a signal in the form of information disclosure to stakeholders to describe positive conditions. This study also found that financial disclosure based on web-ICT has a negative influence on local government financial performance, public sector characteristics that are nonprofit oriented cause disclosure of financial information does not encourage the financial performance of local government. Unlike the private sector, the disclosure of information encourages better corporate financial performance.
Reutilización del desperdicio de frutas para el aprovechamiento en nuevas fibras
Authors: Condor Lizbet , Choque Heidy , Miranda Natali
Published: January 2018

El presente trabajo de investigación busca enfrentar la problemática actual en referencia al desperdicio en crecimiento de alimentos perecibles ocasionados por deficiencias en la distribución debido a los diversos percances en las rutas de transporte desde las provincias hasta la capital, que es el principal mercado para los agricultores y comerciantes dentro del país. Con el análisis de determinadas frutas seleccionadas en un alto estado de maduración se demostrará características y utilidades de la reutilización de estas en referencia al reemplazo del cuero, generando un producto sostenible y económico.
Использование атомной структуры кристаллов кремния для получения многоострийных полевых источников электронов
Authors: Яфаров Р.К.
Published: January 2018

AbstractThe field-emission properties of field electron sources produced using the atomic structure of silicon crystals, the heterophase vacuum-plasma self-organization of island carbon coatings, and highly anisotropic plasma-chemical etching under weak-adsorption conditions are studied. A correlation between the morphological and field-emission characteristics of field cathode microstructures on silicon crystals with various conductivity types is ascertained. The results of experimental studies are interpreted using the Fowler–Nordheim theory in conjunction with changes in the compositions of the surface phases formed in fabricating emitting silicon projections.
Особенности частотной зависимости проводимости неупорядоченных полупроводников в области перехода к режиму с постоянной длиной прыжка
Authors: Ормонт М.А. , Звягин И.П.
Published: January 2018

AbstractThe effect of hybridization of electron states on the high-frequency conductivity of disordered semiconductors is studied. It is shown that the dependence of the pre-exponential factor of the resonance integral on the intercenter separation in a pair determines the abruptness of the change in conductivity mechanisms near the transition of the frequency dependence of the real part of the conductivity σ_1(ω) from sublinear to quadratic. The abruptness of the change of the conductivity regimes is associated with a rapid decrease in hopping distance with increasing frequency near the transition, which leads to a substantial relative decrease in the contribution from the phononless conductivity component in the variable-range hopping regime with increasing frequency and transition to the fixed-range hopping conductivity regime.
Диэлектрические свойства и электропроводность легированного серебром монокристалла TlGaS-=SUB=-2-=/SUB=-
Authors: Мустафаева С.Н. , Асадов С.М. , Керимова Э.М.
Published: January 2018

AbstractThe effect of silver ions (2 mol %) on the dielectric properties and electrical conductivity of TlGaS_2 single crystals grown by the Bridgman–Stockbarger method is investigated. The experimental results of studying the frequency dispersion of the dielectric coefficients of TlGaS_2 single crystals (2 mol % Ag) makes it possible to establish the nature of dielectric losses and the charge-transfer mechanism, to evaluate the density of states near the Fermi level, the spread of states, the average hopping time and length, and the concentration of deep traps responsible for ac conductivity. The Ag doping of the TlGaS_2 single crystals results in an increase in the density of states near the Fermi level and in a decrease in the average hopping time and length.
Электрически активные состояния захвата и переноса заряда, обусловливающие медленную рекомбинацию в кристаллах бромида таллия при низких температурах
Authors: Кажукаускас В. , Гарбачаускас Р. , Савицки С.
Published: January 2018

AbstractTlBr single crystals grown by the Bridgman–Stockbarger method are studied. It is established that frozen-conductivity effects manifest themselves under interband excitation by light at temperatures below 200 K. Herewith, clearly pronounced superlinear dependences of the induced photoconductivity on the strength of the applied electric field manifest themselves. The results of studying thermally stimulated conductivity evidence that these phenomena can be associated with the filling of trap states with thermal activation energies of 0.08–0.12 eV. This state can be removed due to thermal quenching at temperatures of ≳180 K because of the emptying of energy states with an activation energy of 0.63–0.65 eV filled after optical generation.
Влияние глубоких уровней дислокаций в гетероэпитаксиальных InGaAs/GaAs и GaAsSb/GaAs p-i-n-структурах на время релаксации неравновесных носителей
Authors: Соболев М.М. , Солдатенков Ф.Ю.
Published: January 2018

AbstractThe results of an experimental study of the capacitance–voltage ( C – V ) characteristics and deep-level transient spectroscopy (DLTS) spectra of p ^+– p ^0– i – n ^0 homostructures based on undoped dislocationfree GaAs layers and InGaAs/GaAs and GaAsSb/GaAs heterostructures with homogeneous networks of misfit dislocations, all grown by liquid-phase epitaxy (LPE), are presented. Deep-level acceptor defects identified as HL 2 and HL 5 are found in the epitaxial p ^0 and n ^0 layers of the GaAs-based structure. The electron and hole dislocation-related deep levels, designated as, respectively, ED 1 and HD 3, are detected in InGaAs/GaAs and GaAsSb/GaAs heterostructures. The following hole trap parameters: thermal activation energies ( E _ t ), capture cross sections (σ_ p ), and concentrations ( N _ t ) are calculated from the Arrhenius dependences to be E _ t = 845 meV, σ _ p = 1.33 × 10^–12 cm^2, N _ t = 3.80 × 10^14 cm^–3 for InGaAs/GaAs and E _ t = 848 meV, σ _ p = 2.73 × 10^–12 cm^2, N _ t = 2.40 × 10^14 cm^–3 for GaAsSb/GaAs heterostructures. The concentration relaxation times of nonequilibrium carriers are estimated for the case in which dislocation-related deep acceptor traps are involved in this process. These are 2 × 10^–10 s and 1.5 × 10^–10 s for, respectively, the InGaAs/GaAs and GaAsSb/GaAs heterostructures and 1.6 × 10^–6 s for the GaAs homostructures.
Исследование длинноволновых инфракрасных спектров отражения моно- и поликристаллов SmS в области гомогенности
Authors: Улашкевич Ю.В. , Каминский В.В. , Романова М.В. , Шаренкова Н.В.
Published: January 2018

AbstractThe far- and mid-IR reflection spectra of Sm_1 + x S ( x = 0–0.17) samples are recorded and analyzed, as well as their electrical and structural parameters at a temperature of T = 300 K. The bond ionicity in SmS is shown to fall with a decrease in the area of the X-ray coherent scattering region and an increase in the concentration of donor impurities and, consequently, conduction electron concentration. The electrical conductivity of stoichiometric SmS single crystals and polycrystals can be determined with an error of 10% from the IR reflection spectra. Due to the low structural quality of the samples, the electrical conductivity cannot be determined in the case of deviation from stoichiometry.
Влияние концентрации кислорода в составе газовой плазмообразующей смеси на оптические и структурные свойства пленок нитрида алюминия
Authors: Лубянский Я.В. , Бондарев А.Д. , Сошников И.П. , Берт Н.А. , Золотарев В.В. , Кириленко Д.А. , Котляр К.П. , Пихтин Н.А. , Тарасов И.С.
Published: January 2018

AbstractIn the work we investigate synthesis of aluminum nitride films using reactive ion plasma deposition in oxygen/nitrogen gas mixture for application as optical elements for power semiconductor lasers. The experimental refractive index of synthesized AlNO films is dependent on oxygen composition and is decreasing in diapason from 1.76 to 2.035 at elevation of the oxygen fraction.It is shown that the AlN films synthesized by pure nitrogen plasma are polycrystalline and textured. The oxygen presence in discharging gas results to growth of amorphous phase of the AlNO film.
Электронный транспорт в квантовых ямах AlGaAs/InGaAs/ GaAs РНЕМТ при различных температурах: влияние одностороннего дельта-легирования Si
Authors: Сафонов Д.А. , Виниченко А.Н. , Каргин Н.И. , Васильевский И.С.
Published: January 2018

AbstractThe influence of the concentration of δ doping with Si on the electron transport properties of Al_0.25Ga_0.75As/In_0.2Ga_0.8As/GaAs pseudomorphic quantum wells is studied in a broad temperature range of 4.2–300 K. A decrease in the doping efficiency at an electron concentration of >1.8 × 10^12 cm^–2 is found. This is caused by the effects of incomplete impurity ionization, which is also reflected on the temperature dependence of the electron concentration. A nonmonotonic variation in the electron mobility with increasing donor concentration, which is not associated with filling of the upper subband of size quantization, is observed. An increase in the mobility is associated with a rise in the Fermi momentum and screening, while its subsequent drop with increasing Si concentration is caused by the tunnel degradation of the spacer layer with a decrease in the conduction-band potential in the region of the δ-Si layer.
Оптические свойства халькогенидных сплавов на основе теллура в дальнем инфракрасном диапазоне (lambda>30 мкм)
Authors: Рыжов В.А. , Мелех Б.Т.
Published: January 2018

AbstractTernary telluride alloys of Ge–Se(Sb)–Te and Si–Ge(Ga)–Te systems are synthesized in glassy and crystalline states for use in the terahertz frequency range. The transmission spectra of the obtained alloys are measured and studied in a wide wavelength range from 0.75 to 300 μm. The possible mechanisms of their formation are discussed. A comparative analysis of the results shows that the Ge_14Sb_28Te_56 alloy of the GST system is most promising. Its phonon spectrum is in the range of 40–280 cm^–1, limiting the long-wavelength transmission window of this alloy by 35 μm. Optimization of the Ge_14Sb_28Te_56 composition, the removal of impurities, and heat treatment will promote a further decrease in the absorbance in the far-infrared spectrum of this alloy.
Микроструктура и комбинационное рассеяние света тонких пленок Cu-=SUB=-2-=/SUB=-ZnSnSe-=SUB=-4-=/SUB=-, осажденных на гибкие металлические подложки
Authors: Станчик А.В. , Гременок В.Ф. , Башкиров С.А. , Тиванов М.С. , Юшкенас Р.Л. , Новиков Г.Ф. , Герайтис Р. , Саад A.M.
Published: January 2018

AbstractCu_2ZnSnSe_4 thin films are produced by selenizing electrochemically layer-by-layer deposited and preliminarily annealed Cu–Zn–Sn precursors. For flexible metal substrates, Mo and Ta foils are used. The morphology, elemental and phase compositions, and crystal structure of Cu_2ZnSnSe_4 films are studied by scanning electron microscopy, X-ray spectral microanalysis, X-ray phase analysis, and Raman spectroscopy.
Изменение характера биаксиальных напряжений при возрастании x от 0 до 0.7 в слоях Al-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N:Si, полученных методом аммиачной молекулярно-лучевой эпитаксии
Authors: Ратников В.В. , Щеглов М.П. , Бер Б.Я. , Казанцев Д.Ю. , Осинных И.В. , Малин Т.В. , Журавлев К.С.
Published: January 2018

AbstractThe deformation mode and defect structure of Al_ x Ga_1 – x N:Si epitaxial layers ( x = 0–0.7) grown by molecular beam epitaxy and doped with Si under a constant silane flux are studied by X-ray diffractometry. The concentration of Si atoms in the layers measured by secondary ion mass spectrometry is (4.0–8.0) × 10^19 cm^–3. It is found that the lateral residual stresses are compressive at x < 0.4 and become tensile at x > 0.4. The stresses after the end of growth are estimated and the contribution to the deformation mode of the layers of both the coalescence of nuclei of the growing layer and misfit stresses in the layer–buffer system are discussed. It is found that the density of vertical screw and edge dislocations are maximal at x = 0.7 and equal to 1.5 × 10^10 and 8.2 × 10^10 cm^–2, respectively.
Расширенная модель Холстейна-Хаббарда для эпитаксиального графена на металле
Authors: Давыдов С.Ю.
Published: January 2018

AbstractA model that combines the extended Hubbard model involving intra-atomic and interatomic Coulomb repulsion and the Holstein model describing the interaction of a band electron with an Einstein phonon is proposed. Three regions of the phase diagram are considered. The regions correspond to the states of spin- and charge-density waves and the state uniform in spin and charge. Numerical estimations for the Rh, Ir, and Pt substrates show that Coulomb interaction plays a leading part, making possible transitions from the uniform state to the states of spin- and charge-density waves.
Оптимизация параметров поликристаллических фоторезисторов на основе PbS
Authors: Мирошников Б.Н. , Мирошникова И.Н. , Попов А.И.
Published: January 2018

AbstractPhotosensitive elements based on polycrystalline lead sulfide layers are investigated. The influence of heterogeneous reactions at the crystallite–environment interfaces on the photosensitive-element characteristics is considered. It is shown that heat treatment in vacuum can be used to significantly change the parameters of the as-fabricated structures and optimize them for specific optoelectronic systems. A model is proposed to explain the nature of the observed phenomena.
Диоды Шоттки графит/p-SiC, полученные методом переноса нарисованной пленки графита на SiC
Authors: Солован М.Н. , Андрущак Г.О. , Мостовой А.И. , Ковалюк Т.Т. , Брус В.В. , Марьянчук П.Д.
Published: January 2018

AbstractGraphite/ p -SiC Schottky diodes are fabricated using the recently suggested technique of transferring drawn graphite films onto p -SiC single-crystal substrates. The current–voltage and capacitance–voltage characteristics are measured at different temperatures and at different frequencies of a small-signal AC signal, respectively. The temperature dependences of the potential-barrier height and of the series resistance of the graphite/ p -SiC junctions are measured and analyzed. The dominant mechanisms of the charge–carrier transport through the diodes are determined. It is shown that the dominant mechanisms of the transport of charge carriers through the graphite/ p -Si Schottky diodes at a forward bias are multi-step tunneling recombination and tunneling described by the Newman formula (at high bias voltages). At reverse biases, the dominant mechanisms of charge transport are the Frenkel–Poole emission and tunneling. It is shown that the graphite/ p -SiC Schottky diodes can be used as detectors of ultraviolet radiation since they have the open-circuit voltage V _oc = 1.84 V and the short-circuit current density I _sc = 2.9 mA/cm^2 under illumination from a DRL 250-3 mercury–quartz lamp located 3 cm from the sample.
Физические основы самосогласованного моделирования процессов генерации интерфейсных состояний и транспорта горячих носителей в транзисторах на базе структур металл-диэлектрик-кремний
Authors: Тягинов С.Э. , Макаров А.А. , Jech M. , Векслер М.И. , Franco J. , Kaczer B. , Grasser T.
Published: January 2018

AbstractA detailed simulation of degradation (caused by hot charge carriers) based on self-consistent consideration of the transport of charge carriers and the generation of defects at the SiO_2/Si interface is carried out for the first time. The model is tested using degradation data obtained with decananometer n -type-channel field-effect transistors. It is shown that the mutual influence of the above aspects is significant and their independent simulation gives rise to considerable quantitative errors. In calculations of the energy distribution for charge carriers, the actual band structure of silicon and such mechanisms as impact ionization, scattering at an ionized impurity, and also electron–phonon and electron–electron interactions are taken into account. At the microscopic level, the generation of defects is considered as the superposition of single-particle and multiparticle mechanisms of breakage of the Si–H bond. A very important applied aspect of this study is the fact that our model makes it possible to reliably assess the operating lifetime of a transistor subjected to the effects of “hot” charge carriers.
Подавление волноводной рекомбинации за счет использования парных асимметричных барьеров в лазерных гетероструктурах
Authors: Зубов Ф.И. , Максимов М.В. , Гордеев Н.Ю. , Полубавкина Ю.С. , Жуков А.Е.
Published: January 2018

AbstractA semiconductor-laser design is proposed in which parasitic recombination in the waveguide region is suppressed by means of double asymmetric barriers adjacent to the active region. Double asymmetric barriers block the undesirable transport of one type of charge carrier while allowing the transport of the other type of carrier. The spacer in the double asymmetric barrier can serve to compensate the elastic strain introduced by the barrier layers as well as to control the energy spectrum of charge carriers and, thus, the transmission coefficient. By the example of a laser with Al_0.2Ga_0.8As waveguide layers, it is shown that the design with double asymmetric barriers makes it possible to suppress undesirable electron transport by a factor of 4 in comparison to the design using single asymmetric barriers.
Электрическая активность протяженных дефектов в мультикремнии
Authors: Пещерова С.М. , Якимов Е.Б. , Непомнящих А.И. , Павлова Л.А. , Феклисова О.В. , Пресняков Р.В.
Published: January 2018

AbstractThe excess carrier lifetime (τ) distribution in multicrystalline silicon grown by the Bridgman technique from high-purity metallurgical silicon (HPMG-Si) is studied. The features of the variation in τ, caused by the grain-boundary structure of ingots, are revealed. The grain boundaries, dislocations, and impurity microinclusions are studied by electron probe microanalysis (EPMA) and scanning electron microscopy (SEM) using selective acid etching. The electrical activity of extended defects is measured by the electronbeam- induced-current (EBIC) method.
Влияние добавок кремния на свойства монокристаллов германия для инфракрасной оптики
Authors: Шиманский А.Ф. , Павлюк Т.О. , Копыткова С.А. , Филатов Р.А. , Городищева А.Н.
Published: January 2018

AbstractHomogeneous Sb-doped single crystals of Ge–Si solid solutions are grown with a silicon content of 0.2 to 0.8 at %. The optical absorption of single crystals with a resistivity of (2–3) Ω cm is studied by IR Fourier spectroscopy at a wavelength of 10.6 μm in the temperature range from 25 to 60°C. It is found that the introduction of silicon into antimony-doped germanium improves the temperature stability of the optical properties of the crystals.
Ионный синтез кристаллической фазы Ge в пленках SiO-=SUB=-x-=/SUB=-N-=SUB=-y-=/SUB=- при отжиге под высоким давлением
Authors: Тысченко И.Е. , Кривякин Г.К. , Володин В.А.
Published: January 2018

AbstractThe nucleation of the crystalline Ge phase in SiO_ x N_ y films implanted with Ge^+ ions with the energy 55 keV to doses of 2.1 × 10^15–1.7 × 10^16 cm^–2 and then annealed at a temperature of T _a = 800–1300°C under pressures of 1 bar and 1–12 kbar is studied. From analysis of the Raman spectra, it is concluded that amorphous Ge precipitates increase in size upon hydrostatic compression at a temperature of 1000°C. Raman scattering at optical phonons localized in Ge nanocrystals is observed only after annealing of the samples with the highest content of implanted atoms at a temperature of 1300°C. In the photoluminescence spectra, a peak is observed at the wavelength ∼730 nm. The peak is considered to be the manifestation of the quantum-confinement effect in nanocrystals ∼3 nm in size.
Электронная структура, механическая и динамическая стабильность гексагональных субкарбидов M-=SUB=-2-=/SUB=-C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, Pt): ab initio расчеты
Authors: Суетин Д.В. , Шеин И.Р.
Published: January 2018

AbstractAb initio calculations were used to study the properties of a series of hexagonal (Fe_2N-like) subcarbides M_2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young’s modulus, compressibility, Pugh’s indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies E _form are positive with respect to a mixture of d -metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.
Электронные и спектральные свойства интерметаллических соединений RRhSn (R=Gd, Tb)
Authors: Князев Ю.В. , Лукоянов А.В. , Кузьмин Ю.И. , Gupta S. , Suresh K.G.
Published: January 2018

AbstractThe investigations of electronic structure and optical properties of GdRhSn and TbRhSn were carried out. The calculations of band spectrum, taking into account the spin polarization, were performed in a local electron density approximation with a correction for strong correlation effects in 4f shell of rare earth metal (LSDA + U method). The optical studies were done by ellipsometry in a wide range of wavelengths, and the set of spectral and electronic characteristics was determined. It was shown that optical absorption in a region of interband transitions has a satisfactory explanation within a scope of calculations of density of electronic states carried out.
Прогнозирование динамического предела текучести металлов с помощью двух структурно-временных параметров
Authors: Селютина Н.С. , Петров Ю.В.
Published: January 2018

AbstractThe behavior of the yield strength of steel and a number of aluminum alloys is investigated in a wide range of strain rates, based on the incubation time criterion of yield and the empirical models of Johnson-Cook and Cowper-Symonds. In this paper, expressions for the parameters of the empirical models are derived through the characteristics of the incubation time criterion; a satisfactory agreement of these data and experimental results is obtained. The parameters of the empirical models can depend on some strain rate. The independence of the characteristics of the incubation time criterion of yield from the loading history and their connection with the structural and temporal features of the plastic deformation process give advantage of the approach based on the concept of incubation time with respect to empirical models and an effective and convenient equation for determining the yield strength in a wider range of strain rates.
Электрические и магнитные свойства дисульфида гафния, интеркалированного атомами железа
Authors: Плещев В.Г. , Селезнева Н.В.
Published: January 2018

AbstractSimultaneous study of the dependences of the structural parameters, electrical, and magnetic properties of hafnium disulfide intercalated iron atoms in the dependence on the intercalate concentration and temperature has been performed for the first time. The temperature dependences of the electrical resistance are shown to exhibit the activation character with the activation energies characteristic of impurity conduction. The effective magnetic moments of iron ions in Fe_ x HfS_2 is found to be significantly lesser than the values of free iron ions and to decrease as the iron content increases. The character of the temperature dependences of the effective magnetic moments and negative values of the paramagnetic Curie temperatures indicate possible interactions of the antiferromagnetic type between intercalated atoms. However, the dependences of the magnetization on field for Fe_0.33HfS_2 and Fe_0.5HfS_2 obtained at T = 2 K demonstrate the hysteresis phenomenon characteristic of the ferromagnetic state. The results are discussed assuming the existence of hybridization 3 d electron states of intercalated iron atoms with the electronic states of HfS_2 matrices and the competition of various exchange interaction.
Фотодиэлектрические процессы в поликристаллических слоях ZnS:Cu
Authors: Аванесян В.Т. , Ракина А.В. , Пак В.Г. , Сычев М.М.
Published: January 2018

AbstractThe frequency dependences of dielectric parameters of zinc sulfide electroluminescent polycrystalline structures doped with copper are studied in the dark and under light excitation in the visible wavelength range. A positive photodielectric effect most pronounced in the low-frequency range was revealed. The experimental results are explained within framework of formation of a space charge in the bulk of a semiconductor. The analysis of data indicates they can be correlated with luminance characteristics of an electroluminescent layer.
Исследование спинового перехода в монокристалле LaCoO-=SUB=-3-=/SUB=- методом рентгеновского магнитного кругового дихроизма на K- и L-=SUB=-2,3-=/SUB=--краях кобальта
Authors: Сиколенко В.В. , Троянчук И.О. , Карпинский Д.В. , Rogalev A. , Wilhelm F. , Rosenberg R. , Prabhakaran D. , Ефимова E.А. , Ефимов В.В. , Тютюнников С.И. , Бобриков И.А.
Published: January 2018

AbstractSpin transitions of cobalt ions in LaCoO_3 single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K - and L _2,3-edges of Co^3+ ions. The orbital momentum of cobalt ions obtained for the K -edge at the 3 d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor of approximately 1.6, whereas the slope of the magnetization curve value in the same temperature range and magnetic field increases by a factor of more than 10. XMCD experiments at the cobalt L _2,3-edges demonstrate gradual growth of the ratio of the orbital momentum to the spin one L / S from 0.48 to 0.53 in the temperature range from 60 K to 120 K.
Спин-волновой резонанс в химически осажденных Fe-Ni пленках: измерения спин-волновой жесткости и константы поверхностной анизотропии
Authors: Важенина И.Г. , Исхаков Р.С. , Чеканова Л.А.
Published: January 2018

AbstractSingle-layer Fe_ x Ni_1 - x thin magnetic films have been investigated by the spin-wave resonance technique in the entire concentration range. The surface anisotropy and exchange stiffness constants for the films with a Ni content from 30 to 80 at % have been measured from the experimental standing spin wave spectra. The surface exchange spin wave penetration depth δ_ C = 20–30 nm has been determined from the dependences of the surface anisotropy and exchange coupling constants on the Fe_20Ni_80 film thickness in the range of 250–400 nm.
Деформационное поведение и структура квазикристаллического сплава i-Al-Cu-Fe в окрестности отпечатка наноиндентора
Authors: Шалаева Е.В. , Cелянин И.О. , Смирнова Е.О. , Смирнов С.В. , Новачек Д.Д.
Published: January 2018

AbstractThe nanoindentation tests have been carried out for the quasicrystalline polygrain Al_62.4Cu_25.3Fe_12.3 alloy with the icosahedral structure i ; the load P -displacement h diagrams have been used to estimate the contributions of plastic deformation (monotonic and intermittent), and the structures of the transverse microscopic sections have been studied in the vicinity of indentations by electron microscopy. It is shown that several systems of deformation bands are formed in the elasto-plastic zone in the vicinity of the indentations along the close-packed planes of the i lattice with the five-fold and two-fold symmetry axes; the bands often begin from cracks and manifest the signs of the dislocation structure. The traces of the phase transformation with the formation of the β-phase areas are observed only in a thin layer under an indenter. The effects of intermittent deformation are up to 50% of the total inelastic deformation and are related to the plastic behavior of the quasicrystal-activation and passage of deformation bands and also the formation of undersurface micro- and nanosized cracks.
Влияние механических напряжений и отжига на магнитную структуру и магнитоимпеданс аморфных CoFeSiBCr микропроводов
Authors: Неъматов М.Г. , Салем М.М. , Азим У. , Ахмат М. , Морченко А.Т. , Юданов Н.А. , Панина Л.В.
Published: January 2018

AbstractThe structural and magnetic properties of amorphous ferromagnetic microwires can undergo significant measurements under the action of external mechanical stresses and heat treatment. The study of transformations occurring in this case is important for designing various sensors of mechanical stresses, loading, and temperature and also for inducing in the wires a certain type of magnetic anisotropy that plays a significant role in the realization of various effects in them. In this work, the influence of external stresses and annealing on the processes of the magnetization and the magnetic impedance of Co_71Fe_5B_11Si_10Cr_3 microwires having a low positive magnetostriction (~10^-8) in amorphous state has been studied. The influence of external stresses leads to a sharp change in the character of the magnetization reversal curve, which was due to the change in the sign of the magnetostriction and the type of magnetic anisotropy. The amplitude of higher harmonics and the value of the magnetic impedance, respectively, are sensitive to mechanical stresses. Elastic stresses in the wires with a partial crystallization do not lead to a marked change in the magnetic properties; however, annealing can lead to a substantial increase in the axial magnetic anisotropy of the wires existing in the stressed state. The experimental results are analyzed in the framework of a magnetostriction model of induced magnetic anisotropy.
Влияние решеточного и спин-фононного вкладов на температурное поведение расщепления основного состояния Gd-=SUP=-3+-=/SUP=- в SrMoO-=SUB=-4-=/SUB=-
Authors: Горлов А.Д.
Published: January 2018

AbstractThe temperature behavior of the EPR spectra of the Gd^3+ impurity center in single crystals of SrMoO_4 in the temperature range T = 99–375 K is studied. The analysis of the temperature dependences of the spin Hamiltonian b _2 ^0 ( T ) = b _2( F ) + b _2( L ) and P _2 ^0 ( T ) = P _2( F ) + P _2( L ) (for Gd^157) describing the EPR spectrum and contributing to the Gd^3+ ground state splitting Δ E is carried out. In terms of the Newman model, the values of b _2( L ) and P _2( L ) depending on the thermal expansion of the static lattice are estimated; the b _2( F ) and P _2( F ) spin-phonon contributions determined by the lattice ion oscillations are separated. The analysis of b _2 ^0 ( T ) and P _2 ^0 ( T ) is evidence of the positive contribution of the spin-phonon interaction; the model of the local oscillations of the impurity cluster with close frequencies ω describes well the temperature behavior of b _2( F ) and P _2( F ).
Тонкая структура уровней и пьезоспектроскопия A-=SUP=-+-=/SUP=--центров в квантовых ямах GaAs/AlGaAs
Authors: Петров П.В. , Кокурин И.А. , Иванов Ю.Л. , Цырлин Г.Э. , Седов В.Е. , Аверкиев Н.С.
Published: January 2018

AbstractExperimental and theoretical piezospectroscopic investigation of A^+ centers in GaAs/AlGaAs quantum wells doped with beryllium is presented. Spectra of linearly polarized photoluminescence are studied experimentally depending on applied uniaxial pressure. A model of the A^+ center in the quantum well in the presence of uniaxial deformation in the plane of the quantum well has been constructed. Analytical expressions for the level energy, optical transition intensities, and polarization ratio have been obtained. In the framework of the proposed theory, the experimentally observed change in the polarization ratio depending on pressure and the shift of the line maximum towards short waves are explained.
Релаксация колебательно-возбужденных состояний в твердых бинарных системах карбонат--сульфат
Authors: Алиев А.Р. , Ахмедов И.Р. , Какагасанов М.Г. , Алиев З.А. , Гафуров М.М. , Рабаданов К.Ш. , Амиров А.М.
Published: January 2018

AbstractThe processes of molecular relaxation in solid binary carbonate-sulfate systems, such as Li_2CO_3-Li_2SO_4, Na_2CO_3-Na_2SO_4, K_2CO_3-K_2SO_4, have been studied by Raman spectroscopy. It has been revealed that the relaxation time of CO _3 ^2- anion vibration ν_1(A) in a binary system is higher than in an individual carbonate. It is shown that an increase in the relaxation rate may be explained by the existence of an additional mechanism of the relaxation of vibrationally excited states of a carbonate anion. This mechanism is associated with the excitation of the vibration of another anion (SO _4 ^2- ) and the “birth” of a lattice phonon. It has been established that the condition for the implementation of such a relaxation mechanism is that the difference between the frequencies of these vibrations must correspond to the region of a rather high density of phonon spectrum states.
Новый люминофор ИК-диапазона на основе германата Sr-=SUB=-3-=/SUB=-La-=SUB=-2-=/SUB=-(Ge-=SUB=-3-=/SUB=-O-=SUB=-9-=/SUB=-)-=SUB=-2-=/SUB=- : Nd-=SUP=-3+-=/SUP=-, Ho-=SUP=-3+-=/SUP=-
Authors: Мелкозерова М.А. , Бакланова Я.В. , Липина О.А. , Чуфаров А.Ю. , Тютюнник А.П. , Зубков В.Г.
Published: January 2018

AbstractCyclogermanate Sr_3La_2(Ge_3O_9)_2, isostructural to silicate Sr_3Er_2(Si_3O_9)_2, activated by neodymium and holmium is obtained for the first time by the precursor method. Ion Nd^3+ in the structure of Sr_3La_2(Ge_3O_9)_2 is a sensitizer of the infrared luminescence of Ho^3+. Excitation by radiation with a wavelength of 808 nm leads to a series of emission lines in the luminescence spectra of Sr_3La_2- x Nd_ x (Ge_3O_9)_2 : Ho^3+ in the short-wave and middle-IR ranges (1.0–3.4 μm). The highest intensity of lines at 2.1 and 2.7 μm, associated with the ^5 I _7 → ^5 I _8 and ^5 I _6 → ^5 I _7 transitions in the Ho^3+ ion, is found for compositions containing traces of holmium. Based on the analysis of the concentration dependences of the luminescence intensity, an optimal composition of the phosphor is determined, which ensures the maximum efficiency of conversion of laser radiation energy. The data obtained are interpreted in the assumption of cross-relaxation energy transfer from Nd^3+ to Ho^3+.
Фононы, диффузоны и бозонный пик в двумерных решетках со случайными связями
Authors: Конюх Д.А. , Бельтюков Я.М. , Паршин Д.А.
Published: January 2018

AbstractWithin the model of stable random matrices possessing translational invariance, a two-dimensional (on a square lattice) disordered oscillatory system with random strongly fluctuating bonds is considered. By a numerical analysis of the dynamic structure factor S ( q , ω), it is shown that vibrations with frequencies below the Ioffe-Regel frequency ω_IR are ordinary phonons with a linear dispersion law ω( q ) ∝ q and a reciprocal lifetime б ~ q ^3. Vibrations with frequencies above ω_IR, although being delocalized, cannot be described by plane waves with a definite dispersion law ω( q ). They are characterized by a diffusion structure factor with a reciprocal lifetime б ~ q ^2, which is typical of a diffusion process. In the literature, they are often referred to as diffusons. It is shown that, as in the three-dimensional model, the boson peak at the frequency ωb in the reduced density of vibrational states g (ω)/ω is on the order of the frequency ω_IR. It is located in the transition region between phonons and diffusons and is proportional to the Young’s modulus of the lattice, ω_ b ≃ E .
Мессбауэровские исследования наночастиц FeO/Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=- типа ядро/оболочка
Authors: Камзин А.С. , Валиуллин А.А. , Khurshid H. , Nemati Z. , Srikanth H. , Phan M.H.
Published: January 2018

AbstractFeO/Fe_3O_4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical shape with an average size of ~20 nm. It was found that the obtained FeO/Fe_3O_4 nanoparticles had exchange coupling. The effect of anisotropy on the efficiency of heating (hyperthermic effect) of FeO/Fe_3O_4 nanoparticles by an external alternating magnetic field was examined. The specific absorption rate (SAR) of the studied nanoparticles was 135 W/g in the experiment with an external alternating magnetic field with a strength of 600 Oe and a frequency of 310 kHz. These data led to an important insight: the saturation magnetization is not the only factor governing the SAR, and the efficiency of heating of magnetic FeO/Fe_3O_4 nanoparticles may be increased by enhancing the effective anisotropy. Mössbauer spectroscopy of the phase composition of the synthesized nanoparticles clearly revealed the simultaneous presence of three phases: magnetite Fe_3O_4, maghemite γ-Fe_2O_3, and wustite FeO.