where ωi is the natural frequency, K is the coupling strength, k is the average node degree, and Λi is the set of nodes directly coupled to node i. ωi is selected from a Gaussian distribution N(ω¯,σω2) with a mean ω¯ of 4.5 and a standard deviation σω of 0.15, and allocated randomly in the nodes, unless otherwise noted. The coupling strength is normalized using the average degree (Hong et al., 2002; Lee, 2005; Zhao et al., 2010), rather than the degree of individual nodes, in order to maintain the identity of high-degree nodes. Simulations are conducted for 250 and 500 s for the single network and NoN, respectively.
