We thank Alvin Leung, Kamala Anupindi, Nancy McCracken, Paul Coddington, and Tony Skjellum for their assistance in this research. This work has been supported in part by Niagara Mohawk Power Corporation, the New York State Science and Technology Foundation, the NSF under co-operative agreement No. CCR-9120008, and ARPA under contract #DABT63-91-K-0005.