Funding for this research was provided by:
National Natural Science Foundation of China (31900791)
MOE (Ministry of Education in China) Project of Humanities and Social Sciences (19YJC190020)
Received: 30 January 2019
Accepted: 11 October 2019
First Online: 12 November 2019
Ethics approval and consent to participate
: All participants were informed of the purpose and voluntary nature of the survey and were assured anonymity on all responses. Written informed consent was obtained from all the participants. This study was approved by the Committee on Human Experimentation of the Air Force Military Medical University.
: Not applicable.
: The authors declare that they have no competing interests.