Funding for this research was provided by:
Institute for Information and Communications Technology Promotion (2015-0-00062)
National Research Foundation of Korea (2017R1C1B5017730, 2015R1D1A1A01059095)
Text and Data Mining valid from 2019-11-28
Received: 14 May 2019
Accepted: 28 October 2019
First Online: 28 November 2019
Ethics approval and consent to participate
: This study was approved by the ethics committee of the Institutional Review Board of the Chungnam National University (No. 201309-SB-004-01). All participants provided written consent for their participation after they were fully informed about the study and received US$20 per session as a reward for their participation
: Not applicable.
: The authors declare that they have no competing interests.