Visual Analytics - Mapping Scientific Frontiers: The Quest for Knowledge Visualization - page 319

Fig. 9.3 Citations over time are shown as tree rings. Tree rings in red depict the years an
accelerated citation rate was detected (citation burst). Three areas emerged from the visualization
are currently concerned with, which may or may not be consistent with the direction
of the cluster. These clusters represent the intellectual base of a paradigm, whereas
the citing articles associated with a cluster represent the research fronts. It is possible
that the same intellectual base may sustain more than one research front.
CiteSpace identifies noteworthy patterns in terms of structural and temporal
properties. Structuring properties include the betweenness centrality of a cited
reference at both the individual article level and the aggregated level of clusters.
Temporal properties include citation bursts, which measure the acceleration of
citations within a short period of time. It has been shown that these indicators
capture research focuses of the underlying scientific community (Chen 2012 ;Chen
et al. 2010 ;Small 1973 ).
CiteSpace characterizes emerging trends and patterns of change in such networks
in terms of a variety of visual attributes. The size of a node indicates how many
citations the associated reference received. Each node is depicted with a series
of citation tree-rings across the series of time slices. The structural properties of
a node are displayed in terms of a purple ring. The thickness of the purple ring
indicates the degree of its betweenness centrality, which is a measure associated
with the transformative potential of a scientific contribution. Such nodes tend to
bridge different stages of the development of a scientific field. Citation rings in red
indicate the time slices in which citation bursts, or abrupt increases of citations,
are detected. Citation bursts provide a useful means to trace the development of
research focus. Figure 9.3 shows an example of the distribution of topic areas with
strong citation bursts in research of terrorism.