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Andreev Y.Y.,National research technological University
Protection of Metals and Physical Chemistry of Surfaces

It has been established that there is a quantitative relationship between the experimental value of hydrogen overvoltage, a =ηH 2 , in the Tafel equation and the surface energy, δU S, of metal with fcc and hcp structure, which is calculated theoretically in metal surface physics. An equation of slow discharge of hydrogen ions on metal is deduced, in which the a value is a linear function of the value δU S/αF where δU S is the minimal surface energy of the specified metal, α = 0.5 is the transition coefficient, and F is the Faraday num-ber. A prevailing tendency toward a decrease in hydrogen overvoltage on polycrystalline surfaces of metals with fcc, hcp, and bcc lattices with an increase in the minimal surface energy related to the appropriate (111), (0001), and (110) facets of these lattices has been observed. Results of analysis of the relationships between ηH 2 and the surface energy of metal are interpreted within the theory of active centers for heterogeneous catalysis with involvement of a thermodynamic model of the metal surface enriched with atom vacancies. © Pleiades Publishing, Ltd., 2012. Source

Baskov S.N.,National research technological University | Litsin K.V.,Magnitogorsk State Technical University
2015 International Siberian Conference on Control and Communications, SIBCON 2015 - Proceedings

The article deals with sensorless method for determining the angular position of the rotor of a synchronous motor by means of superimposing a high-frequency signal. The scheme of the laboratory stand for the experiment to determine the angular position without the use of the position sensor was made. A technique for determining the angular position of the rotor with an accuracy of 30°was described. The logic diagram for its implementation was presented. The derivation of the formula for the calculation of the angular position of the synchronous motor rotor was presented. Findings during the experiment for determining the angular position sensorless were analyzed. Conclusions to reduce the cost and size of the drive system and increase its reliability were presented. © 2015 IEEE. Source

Filippov E.S.,National research technological University
Russian Physics Journal

On the basis of the assumption of the electron density fluctuation at the band degradation, a calculation parameter (the radius R) of the half-width of the probability distribution over the coordinate R is identified at the level of the maximum electron density fluctuation (at a maximum of the Gaussian function). Based on an analysis of the crystallization process and high polymorphic transformations bcc → fcc, the reasons for the formation of bcc, fcc, hexagonal, and tetragonal structures from the liquid phase, as well as for the high temperature bcc → hcp transition in the solid phase are established using the calculated parameter (the radius R) in the solid and liquid phases. © 2016, Springer Science+Business Media New York. Source

Bokshtein B.S.,National research technological University | Khodan A.N.,RAS Research Center Kurchatov Institute | Zabusov O.O.,RAS Research Center Kurchatov Institute | Mal'Tsev D.A.,RAS Research Center Kurchatov Institute | Gurovich B.A.,RAS Research Center Kurchatov Institute
Physics of Metals and Metallography

In a temperature range of 280-320°C, the mechanism and kinetics of segregation of impurities in steels have yet remained insufficiently studied. Under these conditions diffusion of impurities in the bulk of steel grains practically ceases, and for describing the kinetics of the process it is incorrect to use the Langmuir-McLean equation. In this work we put forward two new approaches to describe the mechanism and kinetics of phosphorus segregation in steels: a model of sequential changes in the state of phosphorus based on first-order reactions and a model of diffusion redistribution of phosphorus between boundaries of carbide precipitates, structure defects, and boundaries of steel grains. A comparative analysis of the suggested models has been conducted, and estimates of the kinetics of segregation based on them have been made; these estimates have been compared with the experimental results obtained in the temperature range of 280-320°C for test times to 20 years. It has been shown that these models fairly well describe the experimental kinetics of phosphorus segregation in boundaries of steel grains. © 2014 Pleiades Publishing, Ltd. Source

Nath R.,se National Center For Basic Science | Raychaudhuri A.K.,se National Center For Basic Science | Mukovskii Ya.M.,National research technological University | Mondal P.,Indian Central Glass and Ceramic Research Institute | And 2 more authors.
Journal of Physics Condensed Matter

We report an electric field driven destabilization of the insulating state in nominally pure LaMnO3 single crystal with a moderate field which leads to a resistive state transition below 300 K. The transition is between the insulating state in LaMnO3 and a high resistance bad metallic state that has a temperature independent resistivity. The transition occurs at a threshold field (Eth) that shows a steep enhancement on cooling. While at lower temperatures the transition is sharp and involves a large change in resistance, it softens on heating and is eventually absent above 280 K. When the Mn4+ content is increased by Sr substitution up to x = 0.1, the observed transition, although observable in a certain temperature range, softens considerably. This observation has been explained as a bias driven percolation type transition between two co-existing phases, where the majority phase is a charge and orbitally ordered polaronic insulating phase and the minority phase is a bad metallic phase. The mobile fraction f of the bad metallic phase deduced from the experimental data follows an activated kinetics as f = fo (E)exp(-Δ/kBT) with the activation energy Δ ≈ 200 meV, and the pre-factor fo (E) is a strong function of the field that leads to a rapid enhancement of f on application of field, leading to the resistive state transition. We suggest likely scenarios for such co-existing phases in nominally pure LaMnO3 that can lead to the bias driven percolation type transition. © 2013 IOP Publishing Ltd. Source

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