Funding for this research was provided by:
Humanity and Social Science Youth Foundation of Ministry of Education of China (17YJC880072)
Beijing Social Science Fund Research Base Project (18JDJYB007, 16JDJYA001)
Program for Rixin Talents of Beijing University of Technology (103000514118003)
Article History
First Online: 6 November 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.