Zhang, Xueqing
Yu, Yi
Sun, Ping
Fan, Zhen
Zhang, Wensheng
Feng, Chengqiang
Funding for this research was provided by:
Beijing Municipal Commission of Education (SYS100270430)
Article History
Received: 7 December 2017
Accepted: 9 November 2018
First Online: 17 January 2019
Competing Interests
: The authors declare no competing interests.