Funding for this research was provided by:
the National Natural Science Foundation of China (81800999)
the Scientific and Technological Research Program of Chongqing Municipal Education Commission (KJQN201800414)
the Program for Innovation Team Building at Institutions of Higher Education in Chongqing in 2016 (CXTDG201602006)
Article History
Received: 15 May 2019
Revised: 7 July 2019
Accepted: 14 July 2019
First Online: 29 July 2019
Ethics approval and consent to participate
: Applicable.
: Not applicable.
: The authors declare that they have no competing interests.