Conceptualization, Z.C., Y.Z. (Yucheng Zou), X.Z., K.H. and Y.Z. (Yanwei Zhang); methodology, Z.C. and X.Z.; validation, Z.C., Y.Z. (Yucheng Zou) and X.Z.; formal analysis, Z.C. and X.Z.; data curation, Z.C.; writing—original draft preparation, Z.C.; writing—review and editing, Y.Z. (Yucheng Zou) and Y.Z. (Yanwei Zhang); project administration, Z.C.; funding acquisition, K.H. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (No. 71671187), the Social Science Foundation of Hunan Province (No. 16YBA063) and the Key Program of Hunan Education Department (No. 15A037).
