Figure 1
From: Spectral effectiveness of engineered thermal cloaks in the frequency regime
Normalized conductivity 
and product ρc parameters used for Pendry (green), Kohn (black) and Milton (magenta) cloaks as a function of r′ inside the cloak.
The inner boundary of the cloak is R1 = 0.15 mm and the outer boundary is R2 = 2R1 = 0.3 mm. We used here ε = 0.1 for Kohn's cloaks.
