P The a u t h o r i s w i t h t h e Lewis Research Center o f t h e N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n i n Cleveland, Qhio and was f o r m e r l y w i t h t h e E l e c t r o n i c s Research Center, NASA, Cambridge, Massachusetts. The work was funded by t h e O f f i c e o f Advanced Research and Technology o f NASA and performed w i t h i n an i n t e r n a l research program a t