This study is partially supported by the National Natural Science Foundation of China ( 51775396 , 61703319 ), the Major Project of Technological Innovation of Hubei Province ( 2016AAA007 , 2017CFA008 ), and the China Scholarship Council ( 201706950088 ). Grateful acknowledgment is made to Dr. Hongxu Guan, Dr. Chao Chen, Dr. Cunlong Fan, and Dr. Chao Deng who provided us with considerable help and thoughtful comments. In addition, the constructive comments of anonymous reviewers are greatly appreciated.