Funding for this research was provided by:
National Natural Science Foundation of China (81573055)
the Fundamental Research Funds for the Central Universities and for Changjiang Scholars, and Innovative Research Team in University (PCSIRT:1171) and Funds of Shaanxi Province
Text and Data Mining valid from 2018-10-15
Received: 5 March 2018
Accepted: 6 August 2018
First Online: 15 October 2018
: The authors declare no competing interests.