Funding for this research was provided by:
National Research Foundation of Korea (2017R1A2B4009177)
Korea Institute of Energy Technology Evaluation and Planning (20164030201380)
Text and Data Mining valid from 2018-10-19
Received: 14 March 2018
Accepted: 26 September 2018
First Online: 19 October 2018
: The authors declare no competing interests.