A mathematical model considering free nuclei was developed to reveal the migration behavior of the free nuclei. Numerical simulation results show that most of the nuclei on the top surface of the melt move downwards a...A mathematical model considering free nuclei was developed to reveal the migration behavior of the free nuclei. Numerical simulation results show that most of the nuclei on the top surface of the melt move downwards and distribute randomly inside the Al melt, which induces more nucleation sites resulting in grain refinement. At the same time, the effect of nuclei size on the nuclei distribution and refinement employing electric current pulse （ECP） was also investigated. The smaller nuclei migrate a short distance with the Al melt at lower speed. But for the larger nuclei, the migration downwards with higher speed benefits the refinement of interior grains of the melt. The research results help to better understand the refinement process and provide a more reasonable explanation of the grain refinement mechanism using ECP.展开更多
To solve the mismatch between the candidate model and the reference model caused by the time change of the tracked head, a novel mean shift algorithm based on a fusion model is provided. A fusion model is employed to ...To solve the mismatch between the candidate model and the reference model caused by the time change of the tracked head, a novel mean shift algorithm based on a fusion model is provided. A fusion model is employed to describe the tracked head by sampling the models of the fore-head and the back-head under different situations. Thus the fusion head reference model is represented by the color distribution estimated from both the fore- head and the back-head. The proposed tracking system is efficient and it is easy to realize the goal of continual tracking of the head by using the fusion model. The results show that the new tracker is robust up to a 360°rotation of the head on a cluttered background and the tracking precision is improved.展开更多
基金Project(SELF-2011-01)supported by the Open Project of Shanghai Key Laboratory of Modern Metallurgy and Materials Processing,ChinaProjects(51204109,51035004)supported by the National Natural Science Foundation of China
文摘A mathematical model considering free nuclei was developed to reveal the migration behavior of the free nuclei. Numerical simulation results show that most of the nuclei on the top surface of the melt move downwards and distribute randomly inside the Al melt, which induces more nucleation sites resulting in grain refinement. At the same time, the effect of nuclei size on the nuclei distribution and refinement employing electric current pulse （ECP） was also investigated. The smaller nuclei migrate a short distance with the Al melt at lower speed. But for the larger nuclei, the migration downwards with higher speed benefits the refinement of interior grains of the melt. The research results help to better understand the refinement process and provide a more reasonable explanation of the grain refinement mechanism using ECP.
基金The National Natural Science Foundation of China(No.60672094,60673188,U0735004)the National High Technology Research and Development Program of China(863 Program)(No.2008AA01Z303)the National Basic Research Program of China (973 Program)(No.2009CB320804)
文摘To solve the mismatch between the candidate model and the reference model caused by the time change of the tracked head, a novel mean shift algorithm based on a fusion model is provided. A fusion model is employed to describe the tracked head by sampling the models of the fore-head and the back-head under different situations. Thus the fusion head reference model is represented by the color distribution estimated from both the fore- head and the back-head. The proposed tracking system is efficient and it is easy to realize the goal of continual tracking of the head by using the fusion model. The results show that the new tracker is robust up to a 360°rotation of the head on a cluttered background and the tracking precision is improved.
