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Experiments on nonequilibrium rapid eutectic growth are surveyed. The applicability limits of the modern theoretical models describing rapid solidification of binary systems are assessed. A problem of rapid eutectic growth when the local equilibrium is violated in the solute diffusion field (in the bulk liquid and at the solid-liquid interface) is formulated. An analytical solution to the problem of rapid lamellar eutectic growth under local nonequilibrium conditions in the solute diffusion field is found. It is shown that the diffusion-limited growth of a eutectic pattern ceases as soon as a chemically homogeneous crystalline phase begins to grow when the critical point V=V D is achieved (V is the solid-liquid interface velocity and V D is the solute diffusion speed in the bulk liquid). At V ≥ V D, eutectic decomposition is suppressed and the nascent homogeneous crystalline phase has the initial (nominal) chemical composition of the binary system. 相似文献
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A. S. Bushmin A. A. Galenko L. M. Dmitriev 《Journal of Applied Mechanics and Technical Physics》1991,32(5):740-744
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 93–97, September–October, 1991. 相似文献
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Journal of Experimental and Theoretical Physics - A nonisothertmal model of spinodal decomposition is proposed for a binary system described by the Ginzburg–Landau energy. The initial stages... 相似文献
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JETP Letters - The crystallization of a supercooled metastable homogeneous phase into a hexagonal periodic lattice has been studied within the phase-field crystal model. The numerically determined... 相似文献
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Ekaterina E. Galenko Viktor K. Ivanov Mikhail S. Novikov Andrey A. Zolotarev Alexander F. Khlebnikov 《Tetrahedron》2018,74(43):6288-6298
A novel effective method is reported for the preparation of 1-amino-1H-pyrazole-4-carboxylic acid derivatives by Fe(II)-catalyzed rearrangement of isoxazoles having (2,4-dinitrophenylhydrazono)methyl substituent at C4. The reaction proceeds smoothly for both E and Z isomers of 4-(hydrazonomethyl)isoxazoles, and this means it is not necessary to separate mixtures of E/Z-isomers of the hydrazones prepared by reaction of 5-methoxy/pirrolidino-4-carbonylisoxazoles and 2,4-dinitrophenylhydrazine. The rearrangement proceeds via the formation of an aziridine intermediate which can be isolated in certain cases. The 2-nitro group in the synthesized 1-[(2,4-dinitrophenyl)amino]-1H-pyrazole-4-carboxylic esters can be selectively reduced in two steps via acylation of the amino group followed by hydrogenation-deacylation using H2-Pd/C. 相似文献
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Using a local nonequilibrium model of solidification, experiments on rapid eutectic growth are analyzed. An analytical solution of a problem of rapid lamellar eutectic growth under local nonequilibrium conditions in the solute diffusion field is found. It is shown that solute diffusion-limited growth of a eutectic pattern is completely finished, and diffusionless growth of the chemically homogeneous crystalline phase begins to proceed at a critical point V = V(D), where V is the solid-liquid interface velocity and V(D) is the solute diffusion speed in bulk liquid. A suppression of eutectic decomposition occurs in the range V > or = V(D) that results in a growth of homogeneous crystal phase with the initial (nominal) chemical composition of the binary system. 相似文献
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Paul Damien Alexander Galenko Elmira Popova Timothy Hanson 《European Journal of Operational Research》2007
We address the problem of a finite horizon single item maintenance optimization structured as a combination of preventive and corrective maintenance in a nuclear power plant environment. We present Bayesian semiparametric models to estimate the failure time distribution and costs involved. The objective function for the optimization is the expected total cost of maintenance over the pre-defined finite time horizon. Typically, the mathematical modeling of failure times are based on parametric models. These models fail to capture the true underlying relationships in the data; indeed, under a parametric assumption, the hazard rates are treated as unimodal, which, as shown in this paper, is incorrect. Importantly, assuming an increasing failure rate, as is typically done, we show, is way off the mark in the present context. Since hazard and cost estimates feed into the optimization phase, from a risk management perspective, potentially gross errors, resulting from purely parametric models, can be obviated. We show the effectiveness of our approach using real data from the South Texas Project Nuclear Operating Company (STPNOC) located in Bay City, Texas. 相似文献
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P. K. Galenko V. G. Lebedev A. A. Sysoeva 《Computational Mathematics and Mathematical Physics》2011,51(6):1074-1090
The critical dynamics of a spatially inhomogeneous system are analyzed with allowance for local nonequilibrium, which leads
to a singular perturbation in the equations due to the appearance of a second time derivative. An extension is derived for
the Eyre theorem, which holds for classical critical dynamics described by first-order equations in time and based on the
local equilibrium hypothesis. It is shown that gradient-stable numerical algorithms can also be constructed for second-order
equations in time by applying the decomposition of the free energy into expansive and contractive parts, which was suggested
by Eyre for classical equations. These gradient-stable algorithms yield a monotonically nondecreasing free energy in simulations
with an arbitrary time step. It is shown that the gradient stability conditions for the modified and classical equations of
critical dynamics coincide in the case of a certain time approximation of the inertial dynamics relations introduced for describing
local nonequilibrium. Model problems illustrating the extended Eyre theorem for critical dynamics problems are considered. 相似文献