Funding for this research was provided by:
Natural Science Foundation of Shanxi Province (201701D21059)
Art Disciplinary Project of Shanxi Province (2017F06)
13th Five-Year Education Science Project of Shanxi Province (GH-17059)
Xinzhou Platform and Talent Project (20180601)
Article History
Received: 22 March 2019
Accepted: 8 June 2019
First Online: 18 June 2019
Competing interests
: The authors declare that they have no competing interests.