Wu, Yuan
Wang, Hui
Cheng, Yongqiang
Liu, Xiongjun
Hui, Xidong
Nieh, Taigang
Wang, Yandong
Lu, Zhaoping
Article History
Received: 11 March 2015
Accepted: 17 June 2015
First Online: 6 August 2015
Competing interests
: The authors declare no competing financial interests.