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