Funding for this research was provided by:
National Natural Science Foundation of China (81271729)
Received: 11 April 2019
Accepted: 9 July 2019
First Online: 1 August 2019
Ethics approval and consent to participate
: The study was performed based on standard principles of ethical and professional conduct.
: The authors are in agreement for the publication of the study.
: The authors declare that they have no competing interests.