Funding for this research was provided by:
the National Social Science Foundation of China (15BJY163)
Article History
First Online: 7 November 2020
Compliance with ethical standards
:
: Authors Ren, Hu, Yu, and Cheng declare they have no conflict of interest regarding the publication of this paper.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors.
: Informed consent was obtained from all individual participants included in the study.