Spiral waves in a system without abnormal excitation underR= 3,R= 6 ((a) and (b)) andR= 3,K= 7 ((c) and (d)). Panels (a) and (b) illustrate the distribution of the excited state, where the black represents the excited state, the white represents the rest and refractory state. Panels (c) and (d) show the tip trajectories of the corresponding spiral waves.