Funding for this research was provided by:
National Natural Science Foundation of China (41804154)
Fundamental Research Funds for the Central Universities, China University of Geosciences (2018022)
Text and Data Mining valid from 2019-11-14
Received: 31 August 2019
Accepted: 4 November 2019
First Online: 14 November 2019
: The author declares no competing interests.