[Liu, Junwan;Li, Zhoujun;Chen, Yiming] Natl Univ Deference Technol, Sch Comp, Changsha, Hunan, Peoples R China.^[Liu, Junwan] Cent S Univ Forestry & Technol, Sch Comp Sci, Changsha, Hunan, Peoples R China.^[Li, Zhoujun] Beihang Univ, Sch Comp Sci & Engn, Beijing, Peoples R China.^[Hu, Xiaohua] Drexel Univ, Coll Informat Sci & Technol, Philadelphia, PA 19104 USA.^[Chen, Yiming] Hunan Agr Univ, Sch Informat Sci & Technol, Changsha, Hunan, Peoples R China.