Affiliation: | 1. Regional Circular Economy Key Laboratory of Gansu Higher Institutions, Lanzhou, People's Republic of China;2. Department of Economics and Trade, Longqiao College of Lanzhou University of Finance and Economics, Lanzhou, People's Republic of Chinazhangfanghong2010@126.com;4. Department of Basic Courses, Gansu Institute of Architectural Technology, Lanzhou, People's Republic of China |