[1] Xidian Univ, Sch Comp Sci & Technol, Xian 710071, Shaanxi, Peoples R China
[2] Xidian Univ, Dept Math, Xian 710071, Shaanxi, Peoples R China
[3] Shaanxi Univ Technol, Dept Management, Hanzhong 723000, Shaanxi, Peoples R China
[4] Shaanxi Univ Technol, Sch Mech Engn, Hanzhong 723000, Shaanxi, Peoples R China