X.L. designed and conducted the study, collected and analyzed the data, wrote the paper, and edited the final manuscript. This work was supported by the Hunan Philosophy and Social Science Fund Project grant (grant number 16YBA039), the Hunan Provincial Social Science Achievement Appraisal Committee Project (grant number XSP17YBZC006) and the Hunan Provincial Department of Education College Research Project (grant number 15C0198).
This work was supported by the Hunan Philosophy and Social Science Fund Project grant (grant number 16YBA039), the Hunan Provincial Social Science Achievement Appraisal Committee Project (grant number XSP17YBZC006) and the Hunan Provincial Department of Education College Research Project (grant number 15C0198).