Funding for this research was provided by:
the National Natural Science Foundation of China (71273229)
the program of Natural Science Foundation of Zhejiang Province (LQ12G03015)
the National Natural Science Foundation of China (71503235)
Received: 18 October 2018
Accepted: 10 February 2020
First Online: 24 February 2020
Ethics approval and consent to participate
: The oral informed consent was obtained from each participant and Zhejiang University Ethical Committee confirmed this form of consent and approved this survey (NO.ZGL2016081). All participants joined voluntarily and were informed their rights of withdrawing from the survey anytime. The participants answered the questionnaires anonymously.
: Not applicable.
: The authors declare that they have no competing interests.