(Color online) Patterns of PWTs interacting with a rectangle defect with height ( H = 30 △ x ) and width ( L = 30 △ x ) at t = 300. The pacing frequencies are ω=0.81ω₀ in (a), ω=0.83ω₀ in (b), and ω=0.88ω₀ in (c), respectively. (d) The dependence of the central angle θ of the fan region on the ω/ω₀. The definition of the θ is shown in (b).