Figure 1

Schematic diagram of the growth mechanisms of the model. (a) Event I. The black and gray nodes are a new node and a randomly selected existing node, respectively. (b) and (c) Event II. The red lines correspond to new edges. The red nodes are randomly selected existing nodes. The green nodes are existing nodes, which are selected by a random walk from each red node. The new edge becomes a short-cut path between the red node and the green node.