This work deals with a non linear inverse problem of reconstructing an unknown boundary γ, the boundary conditions prescribed on γ being of Signorini type, by using boundary measurements. The problem is turned into an optimal shape design one, by constructing a Kohn & Vogelius-like cost function, the only minimum of which is proved to be the unknown boundary. Furthermore, we prove that the derivative of this cost function with respect to a direction θ depends only on the state u0, and not...

Si considera il problema al contorno $-\mathrm{\Delta }u=f(x,u)+ϵ\psi (x,u)$ in $\mathrm{\Omega }$, $u|\partial \mathrm{\Omega }=0$, dove $\mathrm{\Omega }\in {ℝ}^n$ è un aperto limitato e connesso ed $ϵ$ è un parametro reale. Si prova che, se $f(x,s)+ϵ\psi (x,s)$ è «superlineare» ed $ϵ$ è abbastanza piccolo, il problema precedente ha almeno tre soluzioni distinte.

An introduction to the worst scenario method is given. We start with an example and a general abstract scheme. An analysis of the method both on the continuous and approximate levels is discussed. We show a possible incorporation of the method into the fuzzy set theory. Finally, we present a survey of applications published during the last decade.

Uniqueness of the optimal control is obtained by assuming certain conditions on the crowding effect of the species. Moreover, an approximation procedure for the unique optimal control is developed.