Faculty of Engineering, Information and Systems, University of Tsukuba, Tsukuba, Japan;
Graduate School of Information Science and Technology, Osaka University, Osaka, Japan;
Graduate School of Information Science, Nara Institute of Science and Technology, Nara, Japan;
Research Institute of Electrical Communication, Tohoku University, Sendai, Japan;
Research Institute of Electronics, Shizuoka University, Shizuoka, Japan;
School of Science and Technology, Kwansei Gakuin University, Nishinomiya, Japan;
Social; Network; Ambient; Environment; Dynamic; Social; Network; Analysis; Centrality;