The local magnetic moments and hyperfine magnetic fields in disordered metal-metalloid alloys

The local magnetic moments and hyperfine magnetic fields (HFF) in the ordered alloys Fe_{15}Sn and Fe_{15}Si are calculated with the first-principles full-potential linear augmented plane wave (FP LAPW) method. The results are compared with the experimental data on Fe-M (M=Si, Sn) disordered alloys at small metalloid concentration. The relaxation of the lattice around the impurity and its influence on the quantities under consideration are studied. The mechanism of the local magnetic moment formation is described. It is proved that the main distinction between these alloys is connected with the different lattice parameters. Three contributions to the HFF are discussed: the contributions of the core and valence electron polarization to the Fermi-contact part, and the contibution from the orbital magnetic moment.Comment: 3 pages, 3 figures, submitted to Phys. Rev.

Structure peculiarities of cementite and their influence on the magnetic characteristics

The iron carbide $Fe_3C$ is studied by the first-principle density functional theory. It is shown that the crystal structure with the carbon disposition in a prismatic environment has the lowest total energy and the highest energy of magnetic anisotropy as compared to the structure with carbon in an octahedron environment. This fact explains the behavior of the coercive force upon annealing of the plastically deformed samples. The appearance of carbon atoms in the octahedron environment can be revealed by Mossbauer experiment.Comment: 10 pages, 3 figures, 3 tables. submitted to Phys.Rev.

The role of International trade in improving the competitiveness of Saint Petersburg

This article aims to explore the prospects for the development of international trade and the impact of trade on increasing competitiveness of Saint Petersburg. To this end, the authors study the theoretical aspects of regional competitiveness as such, analyse the ten years’ data on the city’s international trade, and explore the significance of image, reputation, and information support for the region’s international trade provided by business information centres abroad. The authors employ the methods of expert opinion and statistical analysis as well as the authors’ own data to consider the problems of international trade development in Saint Petersburg and the ways to improve the city’s competitiveness. The authors estimate the international trade performance of Saint Petersburg and outline the key areas for increasing the city’s competitive ability. This article has theoretical and practical significance for experts studying regional competitiveness, for regional authorities, and the business community

Investment Climate and Investment Attractiveness of Macroregions of Russia

In accordance with the requirements of the law on strategic planning, macro-regions of the Russian Federation have been identified. The next solution is to develop strategies for the socio-economic development of macro-regions. Social and economic development requires financial resources. In a market economy, providing resources involves attracting investment. The distribution of investment between regions is uneven. Indicators of investments in fixed assets, financial investments of organizations and foreign direct investment indicate the attractiveness for investors of a limited number of regions. Assessments of investment attractiveness and investment climate are of interest to authorities, investors and local business communities. Guided by various interests and using original techniques, ratings of investment attractiveness and the investment climate of the regions are formed in scientific research and consulting developments. The results of these works are very contradictory. The article is devoted to the definition of regions — centers of investment activity in the macroregions of the Russian Federation, comparison of ratings agencies on the state of the investment climate and investment attractiveness of the regions

Scientifically-Methodical Bases of Tax Planning in Industrial Complex of Large City

Considered questions of tax revenue planning from large city industrial plants for the example of Saint Petersburg. Investigated the primary factors that influence to the formation the tax base of industrial complexes. Disclosed the peculiarities of planning revenues from sources such as the income tax, property organizations. Characterized the problems which are connected with the tax effect on the development and competitiveness of enterprises. Proposed algorithms for calculating tax revenue

Active and passive sensors for diagnostics quasi-zenith ionospheric HF communication channels

Background. There is a growing need for active sensory diagnostics of partial HF channels to provide frequency support to quasi-zenith HF radio links in varying signal propagation conditions. Enhancing the efficiency of active sensor algorithms, particularly by reducing emission time, is topical. To address this, a transition from sequential to parallel (simultaneous) diagnostics is proposed. Another significant challenge in HF communication is narrowband interference, and overcoming this issue involves the method of passive sensory diagnostics. This method assesses the availability of partial channels by analyzing the spectral density of interference power within them. Aim. The goal of this study is to develop algorithms and software tools that implement spectral monitoring and parallel sensing of partial channels for sensory diagnostics of ionospheric channels in quasi-zenith HF communication. Methods. The proposed approach involves integrating dynamic diagnostic methods into the development of intelligent sensors for ionospheric HF radio links, along with the creation of data analysis methods. Specialized computer software is employed to address the defined tasks. Experimental studies are conducted using the developed devices, which include intelligent active and passive radio sensors for HF radio links, to assess the load on HF communication channels. Results. A sensor for orthogonal quasi-zenith ionospheric radio channels has been created, incorporating algorithms for synthesizing a group pulse with orthogonal subcarriers while minimizing the peak factor. Additionally, algorithms for separating subcarriers and calculating the correlation function at the reception have been developed. The sensor employs the OFDM-BPSK signal modulation method, enabling operation in simultaneous-sequential sounding mode across the potential frequency range for communication. This led to an 8-fold reduction in the total signal emission time. Conclusion. The scientific results obtained have broad practical applications, particularly in enhancing the efficiency of wideband HF communication systems using spread spectrum signals

Specifics of Phase Equilibria Studies in the Multinary Aqueous Systems

Фазовые диаграммы и данные по фазовым равновесиям в многокомпонентных системах лежат в основе технологических схем переработки рассолов природного и техногенного происхождения, проектирования процессов получения, разделения и очистки неорганических веществ. Поэтому разработку новых технологий, усовершенствование технологических процессов необходимо начинать с изученя соответствующих систем и построения фазовых диаграмм. Эффективность изучения фазовых равновесий в многокомпонентных водно-солевых системах оптимизированным методом сечений показана на примере пятикомпонентной системы CO(NH2)2 – NH4Cl – (NH4)2SO4 – NH4H2PO4 – H2O при 25 °C. Оптимизированный метод сечений позволяет определять составы равновесных фаз без выделения их из раствора и последующего физико-химического анализа. В результате образования между карбамидом и хлоридом аммония химического соединения NH4Cl·CO(NH2)2 в системе появляются две нонвариантные области – эвтоническая и перитоническая. В работе описаны особенности прогнозирования составов двух нонвариантных точек, экспериментального определения составов на гиперплоскостях нонвариантных областей для расчета по ним составов равновесных жидких и твердых фаз. Показана эффективность алгоритма прогнозирования нонвариантных составов в системе. Описана методология планирования исследования линий моновариантного равновесия и поверхности кристаллизации индивидуальных солей. По экспериментальным данным построена проекция фазовой диаграммы на солевое основание системыThe data of phase equilibria and phase diagrams have an important significance to guide the development and utilization of brine-mineral resources, design process of obtain, separation and purification of inorganic salts, and provide a theoretical basis for understanding the recovery of rare earth elements, whether from the environment or the economy. Therefore, the phase diagram determination of the corresponding systems is essential for establishment of the optimal temperature-concentration conditions of the process of crystallization. The efficiency of the investigation of the solid-liquid equilibria in quinary system CO(NH2)2 – NH4Cl – (NH4)2SO4 – NH4H2PO4 – H2O at 25 °C by the optimized sections method was shown. The method is allowed to determine the compositions of equilibrium solid phases without isolating them from liquid in the systems differently complexity. As a result of the formation of one complex salt NH4Cl·CO(NH2)2 between urea and ammonium chloride the quinary system has two invariant regions – eutonic and peritonic. In this study, the specifics of predicting the compositions of two invariant points, experimental determination of the compositions on the hyperplanes of invariant regions for computation of the compositions of equilibrium liquid and solid phases were considered. The efficiency of the algorithm for predicting the compositions of invariant points in the system was proved. The methodology of experimental design in studies of univariant curves and salt crystallization surfaces was described. According to the experimental data the phase diagram projection on the salt base of the system was constructe