Funding for this research was provided by:
China National Natural Science Funds for Distinguished Young Scholar (71225005)
Key Projects in the National Science and Technology Pillar Program (2013BAC03B03)
Text and Data Mining valid from 2017-01-06
Accepted: 21 December 2016
First Online: 6 January 2017
Compliance with Ethical Standards
: The authors declare that there is no conflict of interest regarding the publication of this paper.