Tight-binding study of interface states in semiconductor heterojunctions

Localized interface states in abrupt semiconductor heterojunctions are studied within a tight-binding model. The intention is to provide a microscopic foundation for the results of similar studies which were based upon the two-band model within the envelope function approximation. In a two-dimensional description, the tight-binding Hamiltonian is constructed such that the Dirac-like bulk spectrum of the two-band model is recovered in the continuum limit. Localized states in heterojunctions are shown to occur under conditions equivalent to those of the two-band model. In particular, shallow interface states are identified in non-inverted junctions with intersecting bulk dispersion curves. As a specific example, the GaSb-AlSb heterojunction is considered. The matching conditions of the envelope function approximation are analyzed within the tight-binding description.Comment: RevTeX, 11 pages, 3 figures, to appear in Phys. Rev.

Studies of edge turbulence in the Uragan-3M torsatron

Spatial and temporal behavior of the edge fluctuations and their correlation with plasma density behavior inside the confinement region of the Uragan-3M torsatron are investigated. The key role of the radial electric field in turbulent transport suppression is shown.Досліджено динаміку флуктуацій поблизу межі плазми та їх кореляції з поведінкою щільності усередині об’єму утримання а торсатроні Ураган-3М. показана основна роль радіального електричного поля в пригнічені турбулентного потокуИсследована динамика флуктуаций вблизи границы плазмы и их корреляция с поведением плотности внутри объема удержания в торсатроне Ураган-3М. Показана основная роль радикального электрического поля в подавлении турбулентности поток

Assessment of the potential of Russian IT industry clusterization, 2005-2018 [ОЦЕНКА ПОТЕНЦИАЛА КЛАСТЕРИЗАЦИИ ИТ-ОТРАСЛИ РОССИИ В 2005-2018 гг]

The article is devoted to the problem of clustering possibility in Russian information technology industry (IT). The clustering potential concept and its significance in the framework of cluster policy measures modeling are considered. The article uses the example of the Russian IT industry to test the European Cluster Observatory model for clustering potential assessing. The main trends characterizing the change of the IT industry clustering potential in Russian regions were identified. The verification of the current cluster development priorities within the framework of the current state cluster policy was carried out. The regions of Russia that have a high potential for the new IT-cluster formation were identified. The directions for improving the methodological approach to assessing the clustering potential, taking into account the main factors of the information technology industry development, were proposed. The analysis helps to identify few important problems of the Russian IT industry development within the framework of the cluster development model, including a trend towards a decrease in indicators of the IT industry clustering potential for the most socially and economically developed Russian regions, an increase in the level of IT industry monopolization, and also an increase in the negative impact of barriers which preventing new companies from entering the Russian IT market. © 2021 Lomonosov Moscow State University. All rights reserved

Transport accessibility problems of the isolated settlements in russian european arctic zone [ПРОБЛЕМЫ ТРАНСПОРТНОЙ ДОСТУПНОСТИ ИЗОЛИРОВАННЫХ НАСЕЛЁННЫХ ПУНКТОВ ЕВРОПЕЙСКОГО СЕКТОРА АРКТИЧЕСКОЙ ЗОНЫ РОССИИ]

The article identifies and analyzes the list of settlements in the Russian European Arctic regions that are not provided with year-round ground transport accessibility with another territory, that is, are not included in regional and federal land transport networks. The year-round ground transport accessibility concept is introduced as the availability of a year-round transport connection with the core federal highways network on hard-surface roads providing year-round operation along the entire length, or by rail, with possible transfers (congestion) between roads and by rail. A database and GIS of this settlements category are compiled; a quantitative assessment of the resident population living number in them is given. Quantitative estimates indicate an extreme unevenness between the settlements number in the existing Russian European Arctic settlement network and the distribution of their population. The features of the internal Arctic regions transport systems are identified and analyzed from their optimization point of view taking into account the isolated settlements presence. Based on the study, recommendations on specific problems of the island and other isolated territories development, including the use of “local” transport modes, transport and pedestrian infrastructure are formulated. © 2020 Lomonosov Moscow State University. All rights reserved

Innovation clusters in the arctic zone of Russian Federation

The article discusses the problems, directions and opportunities for the development of federal level innovation clusters in the Arctic zone of Russian Federation (AZRF), taking into account the Russian state long-term plans for Arctic territories development and implementing major investment projects. The article analyzes the current territorial structure of supported clusters in the AZRF, explores their industry and production specifics, and identifies the main distinctive features and characteristics of them. Based on the analysis of Russian Arctic regions socio-economic development indicators, the regions, municipalities and cities for the prospective cluster formations development are identified; directions, key specializations and cluster development factors are distinguished. The article justifies the relevance of innovative clusters formation in the context of task innovative, territorial, technological, information and communication, socio-economic development by AZRF. © 2020 Institute of Physics Publishing. All rights reserved

Electrodeposition of rhenium from chloride melts: Electrochemical nature, structure and applied aspects

Processes involved in the electrodeposition of rhenium from chloride melts have been studied over the temperature interval from 680 to 970 0C at a cathodic current density of 5 to 250 mA/cm2. It has been found that rhenium is deposited in the form of continuous layers. In addition to that the growth of deposits as separate single-crystal needles has also been noticed. Continuous layers had axial growth textures. The crystallographic direction of the textures is due to electrolysis conditions, such as concentration of oxygen-containing impurities, temperature, melt composition and cathodic current density. When the concentration of oxygen-containing impurities in the melt decreased, electrolysis temperature increased, the average radius of the supporting electrolyte cations became smaller, or cathodic current density diminished, the direction of the growth textures was changing as follows: (1010) →(1120) →(101L) →(0001) →(0001)needles. The microhardness of the deposits in this series is 900 to 250 kg/mm2. The growth of deposits on textured rhenium substrates and single crystals having different orientations, including bent substrates, was studied. It has been found that the epitaxial growth is virtually unlimited in depth if the orientation of the substrate coincides with the growth texture under given conditions. If the substrate orientation deviated from the growth texture, the epitaxial growth was nearly absent. Kinetic parameters were measured using the galvanostatic method. The exchange current density was determined over the interval of (0.01-0.1) A/cm2 depending on the concentration of oxygen-containing impurities, cation composition, type of the surface and its condition. The parameter α⋅Z, which was estimated by two methods, was equal to 2.1-3.1. The diffusion coefficient of rhenium ions has been found to be 2.8 ⋅10 −5 cm2/s at 790 0C and 3.5 ⋅10 −5 cm2/s at 840 0C. Galvanoplastic production of rhenium products, such as crucibles, ampoules foils, wire, and intricate articles, was performed