[1] Fudan Univ, Sch Math Sci, Shanghai 200433, Peoples R China
[2] Fudan Univ, Key Lab Math Nonlinear Sci, Shanghai 200433, Peoples R China
[3] East China Univ Sci & Technol, Dept Math, Shanghai 200237, Peoples R China
[4] Georgetown Univ, Dept Math & Stat, Washington, DC 20057 USA
[5] Fu Jen Catholic Univ, Coll Management, Grad Inst Business Adm, Taipei 242, Taiwan