[Yang Shi-da;Shan Zhi-yong] Wuhan Univ Sci & Technol, Coll Comp Sci & Technol, Wuhan 430072, Hubei, Peoples R China.^[Yi Ya-lin] Cent China Normal Univ, Sch Math & Stat, Wuhan 430079, Hubei, Peoples R China.^[Shan Zhi-yong] Donghua Univ, Coll Informat Sci & Technol, Shanghai 200051, Peoples R China.