Funding for this research was provided by:
the Achievements Transformation Project of the Gansu Provincial Education Department (2017d-03)
the Scientific and Technological Project of the Gansu Provincial Construction Department (jk2017-21)
the National Natural Science Foundation of China (51968043)
Article History
Received: 1 July 2019
Accepted: 22 October 2019
First Online: 29 October 2019
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.