1. a Praxair Inc. , Department of Business Information Systems , 175 East Park Drive, Tonwanda, NY 14151, USA
2. b Rensselaer Polytechnic Institute , DSES Department , CII 5015, RPI, 110 Eighth St., Troy, NY 12180-3590, USA
3. c Faculty of Electrical Engineering , Mathematics and computer Science, University of Twente , PO Box 217, 7500 AE Enschede, The Netherlands