“…We would like to force the averaged temperature and phase variable to be closed to some fixed values ϑ Q and ϕ Q and their final values at time T to be closed to ϑ Ω and ϕ Ω , respectively. In order to do that we choose the following cost functional 3 2 Ω (ϑ(T ) − ϑ Ω ) 2 + κ 4 2 Ω (ϕ(T ) − ϕ Ω ) 2 (1.5) where (ϑ, ϕ) is the state corresponding to the control u, and the desired temperatures ϑ Q ∈ L 2 (Q), ϑ Ω ∈ L 2 (Ω), the target phases ϕ Q ∈ L 2 (Q), ϕ Ω ∈ L 2 (Ω), and the constants κ i ≥ 0, i = 1, . .…”