1. Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands
2. Faculty EEMCS, University of Twente, P.O. Box 217, NL-7500 AE Enschede, The Netherlands
3. Department of Technical Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands