Funding for this research was provided by:
Chongqing Municipal Education Commission (No.YJG183074)
Major entrustment projects of the Chongqing Bureau of quality and technology supervision (No.CQZJZD2018001)
Chongqing Social Science Planning Project (No.2018YBSH085)
Chongqing research and innovation project of graduate students (No.CYS18252)
Science and Technology Research Project of Chongqing Municipal Education Commission (KJQN201800624)
Text and Data Mining valid from 2019-06-03
Received: 2 December 2018
Revised: 23 April 2019
Accepted: 24 May 2019
First Online: 3 June 2019
Compliance with ethical standards
: The authors acknowledged that there is no conflict of interest in this work.
: This article does not contain any information with human participants or animals performed by any of the authors.