Fig. 2.

h _R mask defined for a σ _m = 0.05,σ _n = 0.05,σ _α = 0.05; b σ _m = 0.05,σ _n = 0.1,σ _α = 0.05; c σ _m = 0.01,σ _n = 0.1,σ _α = 0.05; d σ _m = 0.1,σ _n = 0.05,σ _α = 0.1; and its second derivative calculated after variable m