Funding for this research was provided by:
the Sichuan Provincial Key Research and Development Projects (No. 2017GZ0293, No. 2017GZ0387)
the Cultivating Program of Young and Middle-aged Backbone Teachers of Chengdu University of Technology (No. JXGG201515)
Article History
Received: 16 January 2018
Accepted: 24 April 2018
First Online: 3 May 2018