311 research outputs found

    Radial HI Profiles at the Periphery of Galactic Disks: The Role of Ionizing Background Radiation

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    Observations of neutral hydrogen in spiral galaxies reveal a sharp cutoff in the radial density profile at some distance from the center. Using 22 galaxies with known HI distributions as an example, we discuss the question of whether this effect can be associated exclusively with external ionizing radiation, as is commonly assumed. We show that before the surface density reaches σHI0.5M/pc2\sigma_{\textrm{HI}}\le 0.5 {\cal M}_\odot/{\textrm {pc}}^2(the same for galaxies of different types), it is hard to expect the gas to be fully ionized by background radiation. For two of 13 galaxies with a sharp drop in the HI profile, the "steepening" can actually be caused by ionization. At the same time, for the remaining galaxies, the observed cutoff in the radial HI profile is closer to the center than if it was a consequence of ionization by background radiation and, therefore, it should be caused by other factors.Comment: 15 pages, 6 figure

    Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

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    Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9–1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration

    Dynamic regimes of the stochastic “prey – predatory” model with competition and saturation

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    We consider “predator – prey” model taking into account the competition of prey, predator for different from the prey resources, and their interaction described by the second type Holling trophic function. An analysis of the attractors is carried out depending on the coefficient of competition of predators. In the deterministic case, this model demonstrates the complex behavior associated with the local (Andronov – Hopf and saddle-node) and global (birth of a cycle from a separatrix loop) bifurcations. An important feature of this model is the disappearance of a stable cycle due to a saddle-node bifurcation. As a result of the presence of competition in both populations, parametric zones of mono- and bistability are observed. In parametric zones of bistability the system has either coexisting two equilibria or a cycle and equilibrium. Here, we investigate the geometrical arrangement of attractors and separatrices, which is the boundary of basins of attraction. Such a study is an important component in understanding of stochastic phenomena. In this model, the combination of the nonlinearity and random perturbations leads to the appearance of new phenomena with no analogues in the deterministic case, such as noise-induced transitions through the separatrix, stochastic excitability, and generation of mixed-mode oscillations. For the parametric study of these phenomena, we use the stochastic sensitivity function technique and the confidence domain method. In the bistability zones, we study the deformations of the equilibrium or oscillation regimes under stochastic perturbation. The geometric criterion for the occurrence of such qualitative changes is the intersection of confidence domains and the separatrix of the deterministic model. In the zone of monostability, we evolve the phenomena of explosive change in the size of population as well as extinction of one or both populations with minor changes in external conditions. With the help of the confidence domains method, we solve the problem of estimating the proximity of a stochastic population to dangerous boundaries, upon reaching which the coexistence of populations is destroyed and their extinction is observed. c 2019 Ekaterina P. Abramova, Tatyana V. Ryazanova.Russian Science Foundation, RSF: 16-11-10098This work was supported by Russian Science Foundation (No. 16-11-10098)

    Customs Control in the Eurasian Economic Union and the European Union: the Comparative Analysis

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    The study of the Institute of Customs Control is part of international integration processes. Under the rapidly changing international world facts, the international trade turnover in some directions is decreasing, and in others it is increasing at times, which affects the economy of all countries, their compliance with modern trends, part of all these processes is customs control, as one of the types of control at the state border, requiring the national security of states. The article compares the institute of customs control in the EAEU and the EU. On this basis, a comparison is made according to a number of criteria and key features. The legal regime of goods under customs control, its beginning, completion and correlation with other customs institutions are investigated. The general competence of customs authorities in the field of customs control is commented on. The circumstances of the goods being under customs control in accordance with the legislation of the EAEU and the EU on customs regulation are analyzed. As a result of comparing the institute of customs control in the EAEU and the EU, both similar and different features were identified. The comparison showed a mixed picture, since the two associations are at different stages of political and economic development, and are also characterized by different historical and geographical features.Aim. Study of the main criteria of the Customs Control Institute in the Eurasian Economic Union and the European Union.Tasks. Characteristics of the economic unions of the EAEU and the EU, as well as the study of forms of customs control in the EAEU and disclosure of customs control in the EU.Methods. Comparative legal analysis of international, supranational and customs law, as well as the study and analysis of popular science literature, description and generalization of the material in the process of research.Results. The protection of the security of the State is directly related to economic activity, namely, with the constantly flowing and increasing pace of international trade. States, uniting in unions, form a single legal field in which they create a regulatory framework. The EU introduced the institute of customs control earlier than the EAEU, since the EAEU relied on European experience when creating legislation regulating the customs area. With this in mind, this institute has similar goals and elements of the purpose of its conduct and holding.Conclusion. Actively developing integration processes lead to an increase in world trade turnover and increased control at interstate borders. Every state, and with it the unions, strive for safe and fast trade. Many elements become such tools, one of them is customs control. An institution that  controls the legality, security and mutual cooperation of customs authorities and participants in foreign economic activity

    Analysis of the influence of parametric noise on the dynamics of two interacting populations

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    This paper considers the predator-prey population model, which combines both the stabilizing factors of the intraspecific competition of prey and predator (for resources other than the prey), and the predator saturation. The purpose of this study is a comparative parametric analysis of stochastic phenomena which occur under parametric noise of two different types. The stochastic sensitivity of the attractors is studied. Based on the stochastic sensitivity function technique, noise-induced phenomena are described. In the parametric bistable zone, transitions of two types are carried out: equilibrium → equilibrium and cycle → equilibrium. The values of critical intensities for the occurrence of transition phenomena between attractors are obtained. In the parametric monostable zone, such phenomena as cycle deformation and equilibrium shift are demonstrated. © 2019 Udmurt State University. All right reserved.Russian Science Foundation, RSF: 16–11–10098Funding. The research was supported by the Russian Science Foundation (project no. 16–11–10098)

    Calculation fusion penetration at welding in CO₂

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    The analysis of data on the change in the penetration welding in CO₂ when the polarity of the arc and the number of heat sources. Obtained longitudinal sections settlement welding baths and cross-sections of the weld on the three options. It was found that the two coaxial heat source normally circular distribution of the heat flow is theoretically provide greater penetration in welding than twice the power of a single source. Predominant role in boil arc reverse polarity plays a power transmitted from the cathode region of the arc.Приводится анализ данных по изменению провара при сварке в СО₂ при изменении полярности дуги и количества источников тепла. Получены продольные профили расчетных сварочных ванн и поперечные сечения сварочного шва по трем вариантам. Установлено, что два соосно расположенных источника тепла с нормально-круговым распределением теплового потока теоретически обеспечивают больший провар при сварке, чем один источник удвоенной мощности. Преобладающую роль в проваре дугой обратной полярности играет мощность, передаваемая от катодной области дуги

    Влияние случайного воздействия на равновесные режимы модели популяционной динамики

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    In the paper, we study a dynamic model of interacting populations of the type “predator–two prey”. A detailed parametric analysis of the equilibrium modes arising in the system is carried out. In zones of the bifurcation parameter, where the coexistence of several equilibrium regimes is found, separable surfaces are constructed. Those surfaces are the boundaries of the attraction basins of different equilibria. It is shown that the effect of an external random disturbance can destroy the equilibrium mode of coexistence of three populations and lead to a qualitatively different mode of coexistence. Such qualitative changes lead to the extinction of one or two of the three populations. Using the technique of stochastic sensitivity function and the method of confidence domains, the probabilistic mechanisms of destruction of equilibrium modes are demonstrated. A parametric analysis of the probabilities of extinction of populations for two types is carried out. The range of the bifurcation parameter and the level of noise intensity, that are the most favorable for the coexistence of three populations, are discussed. © 2020 Izvestiya Instituta Matematiki i Informatiki Udmurtskogo Gosudarstvennogo Universiteta. All rights reserved.This study was supported by the Russian Science Foundation, grant no. 16–11–10098

    The chiral Anomalous Hall effect in re-entrant AuFe alloys

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    The Hall effect has been studied in a series of AuFe samples in the re-entrant concentration range, as well as in part of the spin glass range. An anomalous Hall contribution linked to the tilting of the local spins can be identified, confirming theoretical predictions of a novel topological Hall term induced when chirality is present. This effect can be understood in terms of Aharonov-Bohm-like intrinsic current loops arising from successive scatterings by canted local spins. The experimental measurements indicate that the chiral signal persists, meaning scattering within the nanoscopic loops remains coherent, up to temperatures of the order of 150 K.Comment: 7 pages, 11 eps figures Published version. Minor change

    Static Pressure of Hot Gas: Its Effect on the Gas Disks of Galaxies

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    The static pressure of the hot gas that fills clusters and groups of galaxies can affect significantly the volume density and thickness of the gas disks in galaxies. In combination with the dynamic pressure, the static pressure allows several observed peculiarities of spiral galaxies surrounded by a hot medium to be explained.Comment: 9 pages, 2 figures. This is a slightly modified version of the paper published in Astronomy Letters 2008, Vol. 34, No 11, p. 73
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