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Search Results: 1 - 7 of 7 matches for " AS Kuchma "
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M ssbauer Study of Mechanical Alloying Fe-Ti and Fe-Ti-N Alloys

TA Popovich,OV Arestov,AAPopovich,AS Kuchma,

材料科学技术学报 , 2001,
Abstract: Mossbauer spectrometry was used to study the peculiarity of formation of nonequilibrium phase in Fe-Ti and Fe-Ti-N systems by mechanical alloying. Mossbauer spectra of powders show the formation of nonequilibrium crystalline phase and intermetallic compounds during a mechanical alloying process depending on the alloy composition and the milling time.
Steady-state composition of a two-component gas bubble growing in a liquid solution: self-similar approach
G. Yu. Gor,A. E. Kuchma
Physics , 2009, DOI: 10.1063/1.3276708
Abstract: The paper presents an analytical description of the growth of a two-component bubble in a binary liquid-gas solution. We obtain asymptotic self-similar time dependence of the bubble radius and analytical expressions for the non-steady profiles of dissolved gases around the bubble. We show that the necessary condition for the self-similar regime of bubble growth is the constant, steady-state composition of the bubble. The equation for the steady-state composition is obtained. We reveal the dependence of the steady-state composition on the solubility laws of the bubble components. Besides, the universal, independent from the solubility laws, expressions for the steady-state composition are obtained for the case of strong supersaturations, which are typical for the homogeneous nucleation of a bubble.
Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law
G. Yu. Gor,A. E. Kuchma
Physics , 2009, DOI: 10.1063/1.3176896
Abstract: This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.
Nucleation stage in supersaturated vapor with inhomogeneities due to nonstationary diffusion onto growing droplets
Anatoly Kuchma,Maxim Markov,Alexander Shchekin
Physics , 2013, DOI: 10.1016/j.physa.2014.02.005
Abstract: An analytical description of nucleation stage in a supersaturated vapor with instantly created supersaturation is given with taking into account the vapor concentration inhomogeneities arising as a result of depletion due to non-stationary diffusion onto growing droplets. This description suggests that the intensity of the nucleation of new droplets is suppressed in spherical diffusion regions of a certain size surrounding previously nucleated droplets, and remains at the initial level in the remaining volume of the vapor-gas medium. The value of volume excluded from nucleation depends on the explicit form of the vapor concentration profile in the space around the growing droplet, and we use for that the unsteady self-similar solution of time-dependent diffusion equation with a convective term describing the flow of the gas-vapor mixture caused by moving surface of single growing droplet. The main characteristics of the phase transition at the end of the nucleation stage are found and compared with those in the theory of nucleation with homogeneous vapor consumption (the theory of mean-field vapor supersaturation).
Stages of steady diffusion growth of a gas bubble in strongly supersaturated gas-liquid solution
Anatoly E. Kuchma,Gennady Yu. Gor,Fedor M. Kuni
Physics , 2009, DOI: 10.1134/S1061933X09040140
Abstract: Gas bubble growth as a result of diffusion flux of dissolved gas molecules from the surrounding supersaturated solution to the bubble surface is studied. The condition of the flux steadiness is revealed. A limitation from below on the bubble radius is considered. Its fulfillment guarantees the smallness of fluctuation influence on bubble growth and irreversibility of this process. Under the conditions of steadiness of diffusion flux three stages of bubble growth are marked out. With account for Laplace forces in the bubble intervals of bubble size change and time intervals of these stages are found. The trend of the third stage towards the self-similar regime of the bubble growth, when Laplace forces in the bubble are completely neglected, is described analytically.
Gas Bubble Growth Dynamics in a Supersaturated Solution: Henry's and Sievert's Solubility Laws
Gennady Yu. Gor,Anatoly E. Kuchma,Fedor M. Kuni
Physics , 2012,
Abstract: Theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution is presented. We study the influence of Laplace pressure on the bubble growth. We consider two different solubility laws: Henry's law, which is fulfilled for the systems where no gas molecules dissociation takes place and Sievert's law, which is fulfilled for the systems where gas molecules completely dissociate in the solvent into two parts. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux of dissolved gas molecules to the bubble is steady we obtain differential equations on bubble radius for both solubility laws. For the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop bubble dynamics equations for Henry's and Sievert's laws are solved analytically. For both solubility laws three characteristic stages of bubble growth are marked out. Intervals of bubble size change and time intervals of these stages are found. We also obtain conditions of diffusion flux steadiness corresponding to consecutive stages. The fulfillment of these conditions is discussed for the case of nucleation of water vapor bubbles in magmatic melts. For Sievert's law the analytical treatment of the problem of bubble dissolution in a pure solvent is also presented.
Effect of Modern Students’ Lifestyle on their Physical Development
Vladislav R. Kuchma PhD, ScD 1,Olga Yu. Milushkina, PhD 1,2,Natalya A. Bokareva, PhD 1,Natalya A. Skoblina, PhD, ScD 1
International Journal of BioMedicine , 2012,
Abstract: The study of the physical development of pupils over the last 50 years has established some features regarding the formation of morphological and functional parameters of schoolchildren. The studies were conducted using longitudinal and cross-sectional methods, which contribute to a more detailed analysis of the results. The lifestyle of students in Moscow and the factors influencing the physical capacity of the adolescents were studied, employing the questionnaire method.
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