Funding for this research was provided by:
National Social Science Fund of China (1509093)
National Natural Science Foundation of China (71772047)
Received: 20 November 2017
Accepted: 20 January 2019
First Online: 25 January 2019
Compliance with Ethical Standards
: All the authors declare that they have no conflict of interest.
: 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.
: Informed consent was obtained from all individual participants included in the study.