The analysis of the autocorrelation function for (a) different system average degree 〈 k 〉 with N=128² and β=0.60, (b) different system size N with 〈 k 〉 = 228 and β=0.60. The fast Fourier transform (FFT) for (c) different system average degree 〈 k 〉 with N=128² and β=0.60, (d) different system size N with 〈 k 〉 = 228 and β=0.60. Except for large errors when N is large, the quasi-periodic behavior is also robust for different system size N or system average degree 〈 k 〉 .