Funding for this research was provided by:
National Natural Science Foundation of China (31270831, 30970630)
Outstanding Youth Science Foundation of Chongqing (cstc2011jjjq10003)
Program for New Century Excellent Talents in University (NCET-08-0912)
Fundamental Research Funds for the Central Universities (XDJK2016C158)
Doctoral Fund of Southwestern University (XJKJXM003338)
Article History
Received: 10 February 2017
Accepted: 23 March 2017
First Online: 21 April 2017
Free to read: This content has been made available to all.