Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study


We thank two referees for their helpful comments. Kentaro Doi, Naoki Asanuma and students of the School of earth sciences, Faculty of  Integrated Human Studies, Kyoto University assisted us in our experiments. Aya Saito and  Hiroshi Gunji  helped us with our experiments many times under severe weather conditions. We also thank them.