Funding for this research was provided by:
National Natural Science Foundation of China (31260098, 31560127)
Program for Yong Talent of State Ethnic Affairs Commission of China (No.[2014]121)
Fundamental Research Funds for the Central Universities (31920180116, 31920180044, 31920170072)
Article History
Received: 16 December 2018
Accepted: 22 August 2019
First Online: 2 September 2019
Competing interests
: The authors declare that they have no competing interests.