National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [41104094, 11174119]; Research Fund for the Doctoral Program of Higher Education of ChinaResearch Fund for the Doctoral Program of Higher Education of China (RFDP)Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) [20114324120002]; Research Foundation of Education Bureau of Hunan Province, China [12C0370]; Scientific Research Foundation for the Returned Overseas Chinese ScholarsScientific Research Foundation for the Returned Overseas Chinese Scholars