AbstractA simple idea of finding a domain that encloses an unknown discontinuity embedded in a body
is introduced by considering an inverse boundary value problem for the heat equation.
The idea gives a design of a special heat flux on the surface of the body such that from
the corresponding temperature field on the surface one can extract the smallest radius of
the sphere centered at an arbitrary given point in the whole space and enclosing unknown inclusions.
Unlike before, the designed flux is free from a large parameter. An application of the idea
to a coupled system of the elastic wave and heat equations are also given.