Funding for this research was provided by:
Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources (KF2018-2)
Basic science research project of Shaanxi province (2014JM2-5064)
National Natural Science Foundation of China (41402265)
Basic research project of Shaanxi Natural Science Foundation of China (2016JM4014)
China Postdoctoral Science Foundation (2016M590961)
Article History
Received: 26 June 2019
Accepted: 10 February 2020
First Online: 29 February 2020