1. Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
2. Institute of Agricultural Engineering, Aarhus University Faculty of Agricultural Sciences, Research Center Bygholm, Schuttesvej 17, 8700 Horsens, Denmark. Phone: +45 89991900; Fax: +45 89993100; E-mail: ryoh.nakakubo@agrsci.dk
3. Institute of Agricultural Engineering, Aarhus University Faculty of Agricultural Sciences, Research Center Bygholm, 8700 Horsens, Denmark.
4. Hokkaido University, Sapporo 060-8589, Japan.