Zhao, Xiaoguang
Fan, Kebin
Zhang, Jingdi
Keiser, George R
Duan, Guangwu
Averitt, Richard D
Zhang, Xin
Article History
Received: 1 December 2015
Revised: 11 April 2016
Accepted: 12 April 2016
First Online: 4 July 2016
Competing interests
: The authors declare no conflict of interest.