Redistribution of iron during directional solidification of metallurgical-grade silicon (MG-Si) was conducted at low growth rate. Concentrations of iron were examined by ICP-MS and figured in solid and liquid phases, ...Redistribution of iron during directional solidification of metallurgical-grade silicon (MG-Si) was conducted at low growth rate. Concentrations of iron were examined by ICP-MS and figured in solid and liquid phases, at grain boundary and in growth direction. Concentrations are significantly different between solid and liquid phases. The thickness of the solute boundary layer is about 4 mm verified by mass balance law, and the effective distribution coefficient is 2.98×10?4. Iron element easily segregates at grain boundary at low growth rate. In growth direction, concentrations are almost constant until 86% ingot height, and they do not meet the Scheil equation completely, which is caused by the low growth rate. The effect of convection on the redistribution of iron was discussed in detail. Especially, the “dead zone” of convection plays an important role in the iron redistribution.展开更多
An Al-5.3%Zn-5.3%Mg alloy was unidirectionally solidified to determine morphological transition and solute distribution by a modification of the Bridgman technique for crystal growth with growth rates ranging from 4-5...An Al-5.3%Zn-5.3%Mg alloy was unidirectionally solidified to determine morphological transition and solute distribution by a modification of the Bridgman technique for crystal growth with growth rates ranging from 4-500 μm/s and a temperature gradient of 25 K/cm. It was determined that growth rates from 6.5-9.5 μm/s generated a cell morphology, where the lower limit corresponds to the plane front to cellular transition and the upper limit indicates the cellular to columnar dendrite transition. The microstructures of the alloys solidified from 30 μm/s to growth rates less than 500 μm/s were mainly composed of columnar dendrites, while the microstructures solidified at growth rates greater than 500 μm/s were equiaxed. Regarding experimental results on solute distribution, a prediction of the model developed by Rappaz and Boettinger for dendrite solidification of multicomponent alloys was applied with excellent agreement. Results of solute distribution were employed to derive the precipitation fraction of τ-phase needed to increase the electrochemical properties of the alloy to be used as an Al-sacrificial anode.展开更多
The content of this subject research is to conduct optimization for engine mounting system, and through optimization, it can make the vibration between engine and vehicle body achieve a minimum, using Adams software f...The content of this subject research is to conduct optimization for engine mounting system, and through optimization, it can make the vibration between engine and vehicle body achieve a minimum, using Adams software for simulation. It studies the isolation vibration of the engine mounting system and conducts goal optimization for fixed frequency. This paper uses two methods for optimization. One is to use the rational allocation of fixed frequency to optimize the fixed frequency, and the other is to use energy decoupling method to optimize the fixed frequency. It uses Adams software for simulation of the optimized fixed frequency and conducts comparison of simulated results. The simulated results show that the optimized energy distribution situation almost achieves 90%. Compared with original data, decoupling degree also has a very great improvement, illustrating that the optimized data has greater effect for the isolated vibration of engine, in order to further verify the feasibility of optimization design method.展开更多
Petroleum coke was thermally treated on a fixed bed reactor in a temperature range of 1173-1673 K. The changes of the elemental composition and crystalline structure of petroleum coke, with heat treatments as well as ...Petroleum coke was thermally treated on a fixed bed reactor in a temperature range of 1173-1673 K. The changes of the elemental composition and crystalline structure of petroleum coke, with heat treatments as well as the gasification reactivity of the heat-treated petroleum cokes were investigated. The results showed that the petroleum coke was carbonized and grapbitized to a higher degree with increasing heating temperature, while the gasification reactivity decreased. The treatment at temperatures of 1173 and 1473 K significantly enlarged the specific surface area and the pore volume of petroleum coke. Both the specific surface area and the pore volume decreased at 1673 K. An empirical normal distribution function model （NDFM） was found to fit the gasification rates of petroleum coke well. The correlation coefficient of petroleum coke by normal distribution function model at different heat treatment temperatures is between 0.93 and 0.95.展开更多
In this paper, the fixed-payment distribution mode of Agile Virtual Enterprises （AVEs） is studied based on game theory, and the result is compared with that of the share income mode. Finally, the paper proposes that...In this paper, the fixed-payment distribution mode of Agile Virtual Enterprises （AVEs） is studied based on game theory, and the result is compared with that of the share income mode. Finally, the paper proposes that in the circumstance of manufacturing resource information web, the goal function of the game is changed thus promotes the Nash equilibrium effort level approaches or equals to the Pareto equilibrium effort level.展开更多
In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropr...In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropriate approximations according to the relation of the variance and mean of the count, generalizing earlier results in previous literatures. The proof is based on Stein's method and coupling.展开更多
基金Projects(51334004,51204143)supported by the National Natural Science Foundation of ChinaProject(2006L2003)supported by the Scientific Technological Innovation Platform of Fujian Province,China
文摘Redistribution of iron during directional solidification of metallurgical-grade silicon (MG-Si) was conducted at low growth rate. Concentrations of iron were examined by ICP-MS and figured in solid and liquid phases, at grain boundary and in growth direction. Concentrations are significantly different between solid and liquid phases. The thickness of the solute boundary layer is about 4 mm verified by mass balance law, and the effective distribution coefficient is 2.98×10?4. Iron element easily segregates at grain boundary at low growth rate. In growth direction, concentrations are almost constant until 86% ingot height, and they do not meet the Scheil equation completely, which is caused by the low growth rate. The effect of convection on the redistribution of iron was discussed in detail. Especially, the “dead zone” of convection plays an important role in the iron redistribution.
基金the financial support from Consejo Nacional de Ciencia y Tecnología (CONACYT) Project N° 129780PAPIIT-UNAM project N° IN213912-3
文摘An Al-5.3%Zn-5.3%Mg alloy was unidirectionally solidified to determine morphological transition and solute distribution by a modification of the Bridgman technique for crystal growth with growth rates ranging from 4-500 μm/s and a temperature gradient of 25 K/cm. It was determined that growth rates from 6.5-9.5 μm/s generated a cell morphology, where the lower limit corresponds to the plane front to cellular transition and the upper limit indicates the cellular to columnar dendrite transition. The microstructures of the alloys solidified from 30 μm/s to growth rates less than 500 μm/s were mainly composed of columnar dendrites, while the microstructures solidified at growth rates greater than 500 μm/s were equiaxed. Regarding experimental results on solute distribution, a prediction of the model developed by Rappaz and Boettinger for dendrite solidification of multicomponent alloys was applied with excellent agreement. Results of solute distribution were employed to derive the precipitation fraction of τ-phase needed to increase the electrochemical properties of the alloy to be used as an Al-sacrificial anode.
文摘The content of this subject research is to conduct optimization for engine mounting system, and through optimization, it can make the vibration between engine and vehicle body achieve a minimum, using Adams software for simulation. It studies the isolation vibration of the engine mounting system and conducts goal optimization for fixed frequency. This paper uses two methods for optimization. One is to use the rational allocation of fixed frequency to optimize the fixed frequency, and the other is to use energy decoupling method to optimize the fixed frequency. It uses Adams software for simulation of the optimized fixed frequency and conducts comparison of simulated results. The simulated results show that the optimized energy distribution situation almost achieves 90%. Compared with original data, decoupling degree also has a very great improvement, illustrating that the optimized data has greater effect for the isolated vibration of engine, in order to further verify the feasibility of optimization design method.
文摘Petroleum coke was thermally treated on a fixed bed reactor in a temperature range of 1173-1673 K. The changes of the elemental composition and crystalline structure of petroleum coke, with heat treatments as well as the gasification reactivity of the heat-treated petroleum cokes were investigated. The results showed that the petroleum coke was carbonized and grapbitized to a higher degree with increasing heating temperature, while the gasification reactivity decreased. The treatment at temperatures of 1173 and 1473 K significantly enlarged the specific surface area and the pore volume of petroleum coke. Both the specific surface area and the pore volume decreased at 1673 K. An empirical normal distribution function model （NDFM） was found to fit the gasification rates of petroleum coke well. The correlation coefficient of petroleum coke by normal distribution function model at different heat treatment temperatures is between 0.93 and 0.95.
文摘In this paper, the fixed-payment distribution mode of Agile Virtual Enterprises （AVEs） is studied based on game theory, and the result is compared with that of the share income mode. Finally, the paper proposes that in the circumstance of manufacturing resource information web, the goal function of the game is changed thus promotes the Nash equilibrium effort level approaches or equals to the Pareto equilibrium effort level.
基金supported by National Natural Science Foundation of China (Grant No. 11071021)
文摘In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropriate approximations according to the relation of the variance and mean of the count, generalizing earlier results in previous literatures. The proof is based on Stein's method and coupling.
