The constructive comments of the anonymous reviewers are gratefully acknowledged. This work was supported by the National Natural Science Foundation of China (91641107, 91852116), the Science and Technology Plan Project of Hunan Province (Hunan Provincial Key Laboratory of Intelligent Information Processing and Application, 2016TP1020), the Application-oriented Characterized Disciplines, Double First-Class University Project of Hunan Province (Xiangjiaotong [2018]469).