Funding for this research was provided by:
Natural Science Foundation of Shaanxi Provincial Department of Education (17JK0319)
Doctoral Scientific Research Foundation of Xi’an Polytechnic University (107020277)
Shaanxi Provincial Science and Technology Department (2018JQ4016)
Received: 22 March 2019
Accepted: 10 October 2019
First Online: 21 November 2019
: The authors declare that they have no competing interests.