[1] Dept. of Comp. Sci., Ocean Univ. of Qingdao, Qingdao 266071, China
[2] Dept. of Precision Instrum. and Mech, Tsinghua Univ., Beijing 100084, China
[3] Dept. of Mech. Eng., Dalian Railway Inst., Dalian 116028, China
[4] Mobile Postdoctoral Study Station, Tianjin Univ., Tianjin 300072, China