supported by the Humanities and Social Sciences Foundation for the Youth Scholars of Ministry of Education of China(No.15YJCZH066);the Science and Technology Plan Project of Hunan Province(No.2016TP1020);the Science and Technology Plan Project of Hengyang City(No.2017KJ183);the Construct Program of the Key Discipline in Hunan Province and University Students Research and Innovation Experiment Project of Hunan Province(No.C1718);the Scientific Research Fund of Hunan Provincial Education Department(No.17A030);Hunan Provincial Natural Science Foundation of China(No.2018JJ4024);the 2018 National Statistical Science Research Project of China(No.2018LY05)