[Chen, Yawen; Wang, Qi; Liu, Shan; Zhao, Gang] Cent China Normal Univ, Sch Educ Informat Technol, Wuhan 430079, Hubei, Peoples R China.
[Hu, Tao] Hubei Univ Nationalities, Sch Informat Engn, Enshi 445000, Peoples R China.
[Lin, Luyu] Cent China Normal Univ, Natl Engn Res Ctr E Learning, Wuhan 430079, Hubei, Peoples R China.
[Zhao, Dasheng] Wuhan Maritime Commun Res Inst, Wuhan 430079, Hubei, Peoples R China.