作者机构:[1]Dept. of Computer Science and Technology, Tsinghua Univ., Beijing 100084, China
相关基金:National Natural Science Foundation of China (No. 90304014 ), National High Technology Research and Development Program of China (863 Program) (No. 2005AA114160) and National Basic Research Program of China ( 973 Program ) (No. 2003CB314805 )