Funding for this research was provided by:
Beijing Social Science Fund (17SRB005)
Received: 30 August 2019
Accepted: 3 July 2020
First Online: 10 July 2020
Ethics approval and consent to participate
: The study was approved by the Ethical Review Committee of the Capital Medical University (No. 2018SY92). Participation in the survey was completely voluntary, and written consent was obtained from participants. The participants were fully informed before consenting to participate in this study.
: Not applicable.
: The authors declare that there are no competing interests.