National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [71271218, 71571193, 71401185, 61174075]; Humanities and Social Science Foundation of the Ministry of Education of ChinaMinistry of Education, China [13YJC630200]; Natural Science Foundation of Hunan Province of ChinaNatural Science Foundation of Hunan Province [2015JJ2047, 14JJ4050]; Scientific Research Key Project of the Higher Education Institutions of Hunan Province of China [15A055]