Fund: The research was supported by the Fundamental Research Funds for the Central Universities (Grant Nos. 2020CDJSK02ZH03; 2021CDSKXYJG012), the MOE project of Humanities and Social Sciences on the west and the border area (Grant Nos. 20XJC910001; 14XJC910001), the China Scholarship Council (Grant No. 201606055028) and the National Natural Science Foundation of China (Grant No. 11671060). |