[Zhao Gang;Luo Zhuoran;Liu Shan] Cent China Normal Univ, Sch Educ Informat Technolog, Wuhan, Peoples R China.^[Li Jun;Hu Tao] Hubei Univ Nationalities, Sch Informat Engn, Enshi, Peoples R China.^[Zan Hui] Cent China Normal Univ, Natl Engn Res Ctr E Learning, Wuhan, Peoples R China.