Funding for this research was provided by:
Postgraduate Research Innovation Project of Chongqing Normal University (YKC17009)
the Scientific and Technological Research Program of Chongqing Municipal Education Commission (KJ1500331)
the Chongqing Research Program of Basic Research and Frontier Technology (cstc2015jcyjA80012)
the Foundation Project of Chongqing Normal University (15XLB012)
Article History
Received: 11 January 2018
Accepted: 17 April 2018
First Online: 24 April 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.