1. Applications Engr., MeasureTek, P.O. Box 1717, Corvallis, OR 97339. E-mail: mlouie@measuretek.com
2. Assoc. Prof., Room 240 Gilmore Hall, Dept. of Bioresource Engrg., Oregon State Univ., Corvallis, OR, 97331-3906; corresponding author. E-mail: selkerj@engr.orst.edu