Received: 27 December 2017
Accepted: 19 March 2018
First Online: 3 April 2018
: Ying Zhao is currently pursuing the Ph.D. degree in Graduate School of System Informatics at Kobe University, Kobe, Japan. She also works for Ricoh Software Research Center (Beijing) Co., Ltd., Beijing, China. Zhiwei Luo is a professor and Changqin Quan is an associate professor in Graduate School of System Informatics at Kobe University, Kobe, Japan.
: The authors declare that they have no competing interests.
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