Dong, Yan http://orcid.org/0000-0002-2365-6366
Funding for this research was provided by:
National Nature Science Foundation of China (71171164)
Scientific research Foundation of Shaanxi Railway Institute (KY2016-04)
Article History
Received: 29 January 2019
Accepted: 17 July 2019
First Online: 1 August 2019
Competing interests
: The author declares that he has no competing interests.