Funding for this research was provided by:
National Natural Science Foundation of China (71573202)
Text and Data Mining valid from 2019-08-19
First Online: 19 August 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: The study was approved by the Research Ethics Committee, Xi’an Jiaotong University (No: 2016-415). The workers who participated in this study gave written informed consent.