1. Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo, Japan. gaku.morio.vn@hitachi.com
2. Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo, Japan. hiroaki.ozaki.yu@hitachi.com
3. Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo, Japan. terufumi.morishita.wp@hitachi.com
4. Research and Development Group, Hitachi, Ltd., Kokubunji, Tokyo, Japan. kohsuke.yanai.cs@hitachi.com