Ma Yingkun received B.S. degree from Xi'an Jiaotong University in 2007, and then became a Ph.D. candidate there. His main research interest is modeling of dynamic systems. E-mail addresses: mayk.123@stu.xjtu.edu.cn (Y. Ma) Xie Shilin received B.S. and Ph.D. degrees from Xi'an Jiaotong University in 1993 and 1999, respectively, and then became a teacher there. His main research interests are modeling of dynamic systems and vibration control.Corresponding author. Tel.: + 86 29 82668483. E-mail addresses: slxie@mail.xjtu.edu.cn (S. Xie).