Funding for this research was provided by:
National Natural Science Foundation of China (11764039, 11475027, 11305132, 11274255, 11865014, 11847304)
Natural Science Foundation of Gansu Province (17JR5RA076)
Scientific research project of Gansu higher education (2016A-005)
Creation of Science and Technology of Northwest Normal University (NWNU-LKQN-18-33)
Article History
Received: 31 August 2018
Accepted: 16 March 2019
First Online: 1 April 2019