DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Governmenc. Nether the United States Government nor any agencs thereof, nor anv of their emplovees, nor any of their contractors, subcontractors, or their emplovees, makes anv warranty, express or implied. or assumes ans legal habthtyv or responsebdits for che accuracy. completeness, or usefulness of any Information, apperatus, praduct. ar process disclosed, of represents chuc ids use would not infringe privately owned rretts. Relerence herein to ans specific com- mercial product, process, or service bs trade name. trademark, manulacturer, oF otherwise, does not necessarily Consatute or imply 16 cadarsement, recommenda: tion, or favoring by the United States Government or any agency Contractor or subcontractor thereof Phe views and opinions of authors expressed Heremnt do nat necessarily state or reflect those of the United States Government or any agency, contractor or subcontractor thereof Printed in the United States of America Available from National Technical Information Service U.S. Department of Commerce 5285 Port Roval Road Springfield, VA 22161 NTIS price codes: Printed Copy: AO8: Microfiche Copy: A01