Funding for this research was provided by:
Heilongjiang Provincial Postdoctoral Science Foundation (No.2018M631967)
the National Science Foundation of China (No.71573066/G0308)
Received: 6 August 2019
Accepted: 25 August 2020
First Online: 11 September 2020
Ethics approval and consent to participate
: Ethics approval for this study was granted by the Institutional Research Board of Harbin Medical University when we applied for National Natural Science Foundation, the board explicitly approved the written consent implied upon return of a completed questionnaire. The questionnaire included a cover page explaining the purposes and procedures of the study. On this cover page, respondents were told that participation in the survey was voluntary and returning the questionnaires represented informed consent. The data were collected anonymously and the respondents completed the survey questionnaires privately to ensure confidentiality.
: Not applicable.
: The authors declare that they have no competing interests.