Computer-aided simulation of gas adsorption processes in nanopores

A computer-aided simulation of the behavior of molecular gas-phase hydrogen in spherical nanopores was accomplished. The calculations were performed within the frame of molecular dynamics. Interaction between hydrogen molecules is described on the basis of adaptive intermolecular reactive empirical bond-order (AIREBO) potential. The interaction of gas with the walls of nanopores was calculated using the Lennard-Jones potential. The paper also contains the calculated distributions of gas density and velocities of molecules for different temperatures and pressures. The paper states that the adsorption properties of gas systems in nanopores can be described by varying the parameters of the potential of interaction with pore walls

Computer-aided simulation of gas adsorption processes in nanopores

A computer-aided simulation of the behavior of molecular gas-phase hydrogen in spherical nanopores was accomplished. The calculations were performed within the frame of molecular dynamics. Interaction between hydrogen molecules is described on the basis of adaptive intermolecular reactive empirical bond-order (AIREBO) potential. The interaction of gas with the walls of nanopores was calculated using the Lennard-Jones potential. The paper also contains the calculated distributions of gas density and velocities of molecules for different temperatures and pressures. The paper states that the adsorption properties of gas systems in nanopores can be described by varying the parameters of the potential of interaction with pore walls

Photoluminescence of hexagonal boron nitride: effect of surface oxidation under UV-laser irradiation

We report on the UV laser induced fluorescence of hexagonal boron nitride (h-BN) following nanosecond laser irradiation of the surface under vacuum and in different environments of nitrogen gas and ambient air. The observed fluorescence bands are tentatively ascribed to impurity and mono (VN), or multiple (m-VN with m = 2 or 3) nitrogen vacancies. A structured fluorescence band between 300 nm and 350 nm is assigned to impurity-band transition and its complex lineshape is attributed to phonon replicas. An additional band at 340 nm, assigned to VN vacancies on surface, is observed under vacuum and quenched by adsorbed molecular oxygen. UV-irradiation of h-BN under vacuum results in a broad asymmetric fluorescence at ~400 nm assigned to m-VN vacancies; further irradiation breaks more B-N bonds enriching the surface with elemental boron. However, no boron deposit appears under irradiation of samples in ambient atmosphere. This effect is explained by oxygen healing of radiation-induced surface defects. Formation of the oxide layer prevents B-N dissociation and preserves the bulk sample stoichiometry

Kinetics of exciton photoluminescence in type-II semiconductor superlattices

The exciton decay rate at a rough interface in type-II semiconductor superlattices is investigated. It is shown that the possibility of recombination of indirect excitons at a plane interface essentially affects kinetics of the exciton photoluminescence at a rough interface. This happens because of strong correlation between the exciton recombination at the plane interface and at the roughness. Expressions that relate the parameters of the luminescence kinetics with statistical characteristics of the rough interface are obtained. The mean height and length of roughnesses in GaAs/AlAs superlattices are estimated from the experimental data.Comment: 3 PostScript figure

First-principles envelope-function theory for lattice-matched semiconductor heterostructures

In this paper a multi-band envelope-function Hamiltonian for lattice-matched semiconductor heterostructures is derived from first-principles norm-conserving pseudopotentials. The theory is applicable to isovalent or heterovalent heterostructures with macroscopically neutral interfaces and no spontaneous bulk polarization. The key assumption -- proved in earlier numerical studies -- is that the heterostructure can be treated as a weak perturbation with respect to some periodic reference crystal, with the nonlinear response small in comparison to the linear response. Quadratic response theory is then used in conjunction with k.p perturbation theory to develop a multi-band effective-mass Hamiltonian (for slowly varying envelope functions) in which all interface band-mixing effects are determined by the linear response. To within terms of the same order as the position dependence of the effective mass, the quadratic response contributes only a bulk band offset term and an interface dipole term, both of which are diagonal in the effective-mass Hamiltonian. Long-range multipole Coulomb fields arise in quantum wires or dots, but have no qualitative effect in two-dimensional systems beyond a dipole contribution to the band offsets.Comment: 25 pages, no figures, RevTeX4; v3: final published versio

Integrated Security Issues in the Basic Principles of Russian Federation State Policy in the Arctic to 2035: Experience and Prospects for Implementation

March 5, 2020, President of Russia V.V. Putin approved the Basic Principles of Russian Federation State Policy in the Arctic to 2035. It is a strategic planning document aimed at ensuring the national security of the Russian Federation and designed to protect Russia’s interests in the Arctic. It defines goals, directions, tasks, as well as mechanisms for implementing Russian policy in the Arctic for the next 15 years. The authors analyzed the implementation results of the Basic Principles of Russia’s State Policy in the Arctic until 2020 and further perspectives. The article provides a general outline of the Basic Principles of Russian Federation State Policy in the Arctic to 2035. The authors focus on the analysis of the leading national security challenges in the Arctic and enhancing integrated security of the fuel and energy complex, as well as the main directions of the implementation of the state policy of the Russian Federation in the Arctic. They are the protection of the population and territories of the Arctic zone from natural and human-made emergencies, enhancing national security in the Arctic zone, ensuring the military security of the Russian Federation, and protection of the state border of the Russian Federation. It is emphasized that the comprehensive implementation of the Basic Principles will contribute to improving the quality of life of people in the Arctic zone, socio-economic development of the country, and increasing its defense capability in the Arctic

Trans-Arctic Transport Corridor: Political, Economic and Strategic Potential for Russia

The study is devoted to the large-scale Trans-Arctic Transport Corridor (TATC) project aimed at integrating major Russian port centers — St. Petersburg, Murmansk, Arkhangelsk and Vladivostok — in order to create a unified transport system combining sea, rail, road and inland waterways. This project aims to connect the key economic centers of Eurasia and form a seamless logistics corridor that can significantly increase the efficiency of international trade and enhance national transport sovereignty. The purpose of the work is to comprehensively assess the historical background of the project, its economic feasibility, as well as its political, diplomatic, and military-strategic significance for Russia and its partners along the Arctic route. The research uses methods of system analysis, in-depth historical review and expert assessment. The results highlight the uniqueness of TATC as a strategic instrument aimed at strengthening Russia’s position in global trade and security. At the same time, significant climatic, infrastructural, hydrographic and international legal challenges have been identified, which should be taken into account when developing the transport route. In particular, navigation in the Arctic is complicated by the presence of ice cover along a significant part of the sea route for most of the year, which requires the development of an icebreaking fleet and innovative navigation technologies. The paper offers recommendations for improving interdepartmental coordination, developing the icebreaking fleet and port infrastructure, overcoming hydrographic difficulties, as well as actively involving the indigenous peoples of the North in the economic development of the region, taking into account environmental and social aspects. The authors emphasize that the successful implementation of the Trans-Arctic Transport Corridor will become the foundation for the sustainable development of the Arctic region and will strengthen Russia’s geopolitical influence on the global stage, contributing to the formation of a new transport framework that provides unhindered access to the oceans and improves international trade relations with partners from Asia, Europe and America

The role of artificial intelligence technologies in long-term socio-economic development and integrated security

The symbol of the second decade of the 21st century is the renaissance of artificial intelligence technologies. Today, the consequences of introducing such systems are still not fully understood (especially when the results prepared by the neural network are completely incomprehensible to humans, unlike the results of the logical conclusion of an expert system) in the informational and technological processes of modern society, but the question already concerns such issues as the "ethics of machine intelligence", about a person’s readiness to transfer the right to make decisions to artificial intelligence instead of himself. The object of the paper is to study strategic documents that determine the prospects for the development of artificial intelligence technologies, primarily in the largest economies of the world to determine the contours of global socio-economic and technological development. In the framework of the system-structural and institutional approaches, a comparative and conceptual analysis of the strategies of the leading countries in process of development of artificial intelligence was carried out. The mechanisms for implementing the strategic priorities of the most advanced countries are identified and described. Authors noted the intensification of international competition in the field of development and implementation of artificial intelligence technology and, accordingly, the transformation of complex security threats

Evolution of microstructure and microhardness of dispersion-hardened V-Cr-Zr-W alloy during deformation by torsion under pressure

Results of the study of the microstructural evolution and microhardness changes of dispersion-hardened V–Cr–Zr–W alloy under severe deformation during torsion on Bridgman anvils are presented. Typical structural states and mechanisms of their formation are revealed for basic evolution stages as well as appropriate microhardness values are determined. It was shown that at true logarithmic strain values (e) in the range 0.7 ≤ e 2, the anisotropic submicrocrystalline structure is observed and the formation of two-level nanostructural states was found within grains. In the strain range (e) from 3 to 6.6, submicrocrystal sizes hardly change, but changes of two-level nanostructural state parameters are observed: the nanofragment size decreases and values of elastic curvature of the crystal lattice increases