tResearch supported in part by the DOE under grant ET-76-C-01-2295 and in part by AFOSR under grant AFOSR 82-0258. The first author also acknowledges thankfully the support of the Fundacion ITP. Madrid;
Spain. Dr. D. A. Castanon is presently at Alphatech;
Inc.. 3 New England Executive Park. Burlington. MA 01803;