Funding for this research was provided by:
Natural Science Foundation of Hunan Province (2018JJ2097)
Special Innovation Projects of Universities in Guangdong Province, China (No.2018KTSCX)
Text and Data Mining valid from 2020-01-02
Received: 31 July 2019
Accepted: 18 December 2019
First Online: 2 January 2020
: The authors declare that they have no competing interests.