Funding for this research was provided by:
National Natural Science Foundation of China (61603345)
Outstanding Young Teacher Development Fund of Zhengzhou University (F0001175)
Text and Data Mining valid from 2019-01-18
Received: 3 December 2018
Accepted: 2 January 2019
First Online: 18 January 2019
: The authors declare that there is no conflict of interest regarding the publication of this paper. The authors declare that they have no competing interests.