Obituaries: Richard Ewing

0 (x,0) and to determine the spatial solution profile at a later timeu f (x,T). The inverse problem is to be givenu f (x,T) and seek the initial configurationu 0. This is an extremely ill-conditioned problem. The trick used was to replace the heat operatoret by itsYosida approx imantet(I‐ e) ‐1