[1] Beijing Jiaotong Univ, Sch Comp & Informat Technol, Beijing 100044, Peoples R China
[2] Beijing Informat Sci & Technol Univ, Sch Informat Management, Beijing 100092, Peoples R China
[3] Beijing Univ Technol, Coll Comp Sci, Beijing 100124, Peoples R China