Published online by Cambridge University Press: 15 September 2002
We consider the problem of localizing aninaccessible piece I of the boundary of a conducting medium Ω, anda cavity D contained in Ω, from boundary measurements on theaccessible part A of ∂Ω. Assuming that g(t,σ) isthe given thermal flux for (t,σ) ∈ (0,T) x A, andthat the corresponding output datum is the temperature u(T 0,σ)measured at a given time T 0 for σ ∈ A out ⊂ A, weprove that I and D are uniquely localized from knowledge of all possiblepairs of input-output data $(g,u(T_0)_{\mid A_{{\rm out}}})$ . The sameresult holds when a mean value of the temperature is measured over a smallinterval of time.