1. School of Business, East China University of Science and Technology, Shanghai 200237, P. R. China
2. Research Center for Econophysics, East China University of Science and Technology, Shanghai 200237, P. R. China
3. International Elite Engineering School, East China University of Science and Technology, Shanghai 200237, P. R. China
4. School of Mathematics, East China University of Science and Technology, Shanghai 200237, P. R. China