Funding for this research was provided by:
Beijing University of Posts and Telecommunications (No.CX2019309)
National Natural Science Foundation of China (61471064)
National Science and Technology Major Project of China (No.2017ZX03001022)
Text and Data Mining valid from 2019-07-23
Received: 14 February 2018
Accepted: 30 April 2019
First Online: 23 July 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants or animals performed by any of the authors.