基金supported in part by the National Natural Science Foundation of China(60604032, 60674001)in part by the State Key Laboratory of Rail Traffic Control and Safety of Beijing Jiaotong University(RCS2008ZZ04,SKL2007K006)+1 种基金Shandong Province Domestic Visitor Foundationin part by the the National 863 High Technology Plan of China(2007AA11Z247)