  Cascading breakdowns of real networks are severe accidents in recent years,
such as the blackouts of the power transportation networks in North America. In
this paper, we study the effects of geographical structure on the cascading
phenomena of load-carried scale-free networks, find that more geographically
constrained networks tend to have larger cascading breakdowns. Explanations by
the effects of circles and large betweenness of small degree nodes are
provided.
