The Capture and Diffusion of Knowledge Spillovers: The Influence of the Position of Cities in a Network - Methods for Multilevel Analysis and Visualisation of Geographical Networks - page 174

and development cooperation between the public and private sectors, technology
diffusion and personnel movements. We assume that personal contacts exist between
people involved in the same European RTD projects because it seems likely that
scientists choose collaborators with whom they are acquainted.

11.3 The Distribution of Knowledge Flows Within the

European System of Cities

The resulting graph of European scientific-research collaboration networks
(Fig. 11.1 ) has a large number (28,558) of links. How are these links distributed
between cities?
First, we can study the whole properties of this network. The connectivity of the
graph can be measured using three indices: (i) the density of links in the graph, or
the number of links expressed as a proportion of the maximum possible number of
links; (ii) the diameter of the graph, or the longest of the shortest paths between
all pairs of vertices, which measures the maximal extent of the network; and (iii)

Fig. 11.1 Graph of Research Collaborations in NBIC among European cities, 1986-2006 (Made
with Pajek software, Kamada-Kawai layout. Source: NBIC-Euro, Comin , 2009 )