[Corresponding author] Tel: 86-21-51980157, Fax: 86-21-51980017, E-mail: chengzhh@fudan.edu.cn (CHENG Zhi-Hong); [Corresponding author] Tel: 86-21- 51980135, Fax: 86-21-51980017, E-mail: dfchen@shmu.edu.cn (CHEN Dao-Feng).