[1] North China Elect Power Univ, Dept Math & Phys, Baoding 071003, Peoples R China
[2] Tsinghua Univ, Sch Econ & Management, Key Res Inst Humanities & Social Sci Univ, Res Ctr Contemporary Management, Beijing 100084, Peoples R China
[3] Univ Macau, Fac Business Adm, Taipa, Macau, Peoples R China