Funding for this research was provided by:
"Innovation team training plan" of Colleges and Universities during 13th Five-Year Plan in Tianjin. (TD13-5019)
Text and Data Mining valid from 2018-06-14
Received: 8 March 2018
Accepted: 30 May 2018
First Online: 14 June 2018
: The authors declare that they have no competing interests.
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