Funding for this research was provided by:
the National Natural Science Foundation of China (51178054)
Innovative Research Group Project of the National Natural Science Foundation of China (51108036)
Key R&D Plan of Shaanxi Province in 2018-General Project of soft Science Research Program (S2018-ZC-RKXMS-011)
Shaanxi Provincial Department of Education 2018 Special Scientific Research Plan. (18JK1109)
Received: 29 December 2019
Accepted: 23 April 2020
First Online: 14 May 2020
Ethics approval and consent to participate
: This article does not contain any studies with human participants or animals performed by any of the authors.
: All authors agree to submit this version and claim that no part of this manuscript has been published or submitted elsewhere.
: The authors declare that they have no conflict of interest.