The research detailed in this monograph was originally motivated by our
interest in control problems involving partial and delay differential
equations. Our attempts to apply control theory techniques to such prob-
lems in several areas of science convinced us that in the need for
better and more detailed models of distributed/ continuum processes in
biology and mechanics lay a rich, interesting, and challenging class of
fundamen- tal questions. These questions, which involve science and
mathematics, are typical of those arising in inverse or parameter
estimation problems. Our efforts on inverse problems for distributed
parameter systems, which are infinite dimensional in the most common
realizations, began about seven years ago at a time when rapid advances
in computing capabilities and availability held promise for significant
progress in the development of a practically useful as well as
theoretically sound methodology for such problems. Much of the research
reported in our presentation was not begun when we outlined the plans
for this monograph some years ago. By publishing this monograph now,
when only a part of the originally intended topics are covered (see
Chapter VII in this respect), we hope to stimulate the research and
interest of others in an area of scientific en- deavor which has
exceeded even our optimistic expectations with respect to excitement,
opportunity, and stimulation. The computer revolution alluded to above
and the development of new codes allow one to solve rather routinely
certain estimation problems that would have been out of the question ten
years ago.