Funding for this research was provided by:
Natural Science Foundation of Heilongjiang Province (QC2009C99)
Science and Technology Planning Project of Daqing City (zd-2017-49)
Text and Data Mining valid from 2018-04-03
Received: 2 November 2017
Accepted: 21 March 2018
First Online: 3 April 2018
: The author declares that they have no competing interests.