This paper focuses on the inverse problem of identifying an internal void in a bounded two- or three-dimensional region. Information, in form of a heat flux and temperature, is assumed to be obtainable only on the external boundary of the region. The reciprocity gap approach with a suitable test functions is used in both the two- and three-dimensional cases.
Baker, Breanne, "Thermal Imaging to Recover a Defect in Three Dimensional Objects" (2006). Mathematical Sciences Technical Reports (MSTR). 37.