Funding for this research was provided by:
National Natural Science Foundation of China (11402140)
National Natural Science Foundation of China (11404197)
Natural Science Foundation of Shanxi Province (2015021016)
Natural Science Foundation of Shanxi Province (201701D221006)
Article History
Received: 2 January 2018
Accepted: 7 March 2018
First Online: 15 March 2018