Funding for this research was provided by:
National Natural Science Foundation of China (21878200, 21676174)
Joint Fund of Coal (U1610115)
Shanxi Scholarship Council of China (2017-036)
Natural Science Foundation of Shanxi Province (2015012019, 201703D421038)
Article History
Received: 16 June 2019
Revised: 15 April 2020
Accepted: 22 April 2020
First Online: 28 April 2020
Compliance with ethical standards
:
: The authors declare no competing financial interest.