Funding for this research was provided by:
National Natural Science Foundation of China (U1866212)
Foundation for Fundamental Research of China (JSZL2016110B003)
Major Fundamental Research Program of Shaanxi (2017ZDJC-26)
Postdoctoral Research Foundation of China (2018M633460)
Innovation Fund of Xidian University.11 project (B12026)
Article History
Received: 31 December 2018
Accepted: 15 May 2019
First Online: 28 May 2019
Competing Interests
: The authors declare that they have no competing interests.