The authors would like to express their sincere thanks to the editors and the anonymous reviewers for their insightful comments, suggestions and detailed feedback. In addition, this research was financially supported by the National Natural Science Foundation of China (Nos. 71501080, 71572184, 71471073, and 71471074), and the self-determined research funds of CCNU from the colleges'' basic research and operation of MOE (Nos. CCNU15A05050, CCNU14Z02016).