Funding for this research was provided by:
National Natural Science Foundation of China (61307067, 11574125)
Natural Science Foundation of Shandong Province (ZR2015JL024)
Taishan Scholar Project of Shandong Province (ts201511055)
Text and Data Mining valid from 2018-03-07
Received: 24 November 2017
Accepted: 27 February 2018
First Online: 7 March 2018
: The authors declare that they have no competing interests.
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