Affiliation: | 1. Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology, 2‐17‐2‐1 Tsukisamu‐Higashi, Toyohiraku, Sapporo 062‐8517 (Japan), Fax: (+81)?(0)11‐857‐8985;2. Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo 060‐0819 (Japan) |