Figure 2
Controllability of MCN.
(a) Multi-chain structure in MCN. Different color of nodes and links highlights different chains in two layers. In each layer, the smaller the node’s number, the larger its out-degree. (b) Driver node density nD as a function of the proportion of removed nodes p. The nodes are removed according to two strategies: RA (random attacks: randomly remove p fraction of nodes) and TA (targeted attacks: remove the top p fraction of nodes according to their out-degrees). Two networks are compared: a congruence network (CN) with remainder r = 1 and a directed scale-free (SF) network with the same scaling exponent γ = 2.001 in both in- and out-degree distributions. The two networks have the same size N = 100 and average out-degree 
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