Funding for this research was provided by:
National Natural Science Foundation of China (11671284)
Sichuan Provincial Natural Science Foundation of China (2015JY0002, 2017JY0197)
the Research Foundation of the Education Department of Sichuan Province (15ZA0032)
Article History
Received: 23 January 2018
Accepted: 27 April 2018
First Online: 7 May 2018