Liu, Yang http://orcid.org/0000-0001-7650-0077
Funding for this research was provided by:
the Science and Technology Plan Project of Gansu Province in China (17JR5RA279)
Article History
Received: 2 July 2018
Accepted: 17 October 2018
First Online: 24 October 2018
Competing interests
: The author declares that he has no competing interests.