Funding for this research was provided by:
National Natural Science Foundation of China (11761011, 11461003, 11401116)
Natural Science Foundation of Guangxi (2014GXNSFBA118003)
Article History
Received: 20 September 2018
Accepted: 8 February 2019
First Online: 19 February 2019
Competing interests
: The authors declare that they have no competing interests.