David W. Yarbrough is the V.P. of R&D Services, Inc., a testing and consulting firm located in Watertown, TN, USA. He holds a PhD from Georgia Institute of Technology and is an Emeritus Professor of Chemical Engineering at Tennessee Technological University. Dr. Yarbrough is a licensed professional engineer in Tennessee and Florida and a Fellow of ASTM-International. E-mail: dave@rdservices.com.