Funding for this research was provided by:
National Natural Science Foundation of China (81801448, 81820108016)
Text and Data Mining valid from 2019-11-25
Received: 17 September 2019
Accepted: 18 November 2019
First Online: 25 November 2019
Ethics approval and consent to participate
: The study has received approval and was carried out in accordance with the approved guidelines from the Zhengzhou University Research Ethics Board.
: Not applicable.
: The authors declare that they have no competing interests.