Copyright 1999 by Loyola College in Maryland except where otherwise noted. This work relates to NSF Cooperative Agreement ENG-9707092. The U.S. government retains a nonexclusive and nontransferable license to exercise all exclusive rights provided by copyright. The ISBN number for this report is 1-883712-53-x. This report is distributed by the National Technical Information Service (NTIS) of the U.S. Department of Commerce as NTIS report PB99-144214 .