Funding for this research was provided by:
project of Yangtze Upriver Economic Research Center (CJSYI-201806)
the NSF of China (11871124 and 11471060)
Basic Research Program of Chongqing (cstc2018jcyjAX0241)
Received: 2 February 2018
Accepted: 26 August 2019
First Online: 11 September 2019
: The authors declare that they have no competing interests.