3 research outputs found
Dragon-kings: mechanisms, statistical methods and empirical evidence
This introductory article presents the special Discussion and Debate volume
"From black swans to dragon-kings, is there life beyond power laws?" published
in Eur. Phys. J. Special Topics in May 2012. We summarize and put in
perspective the contributions into three main themes: (i) mechanisms for
dragon-kings, (ii) detection of dragon-kings and statistical tests and (iii)
empirical evidence in a large variety of natural and social systems. Overall,
we are pleased to witness significant advances both in the introduction and
clarification of underlying mechanisms and in the development of novel
efficient tests that demonstrate clear evidence for the presence of
dragon-kings in many systems. However, this positive view should be balanced by
the fact that this remains a very delicate and difficult field, if only due to
the scarcity of data as well as the extraordinary important implications with
respect to hazard assessment, risk control and predictability.Comment: 20 page
Urban road networks -- Spatial networks with universal geometric features? A case study on Germany's largest cities
Urban road networks have distinct geometric properties that are partially
determined by their (quasi-) two-dimensional structure. In this work, we study
these properties for 20 of the largest German cities. We find that the
small-scale geometry of all examined road networks is extremely similar. The
object-size distributions of road segments and the resulting cellular
structures are characterised by heavy tails. As a specific feature, a large
degree of rectangularity is observed in all networks, with link angle
distributions approximately described by stretched exponential functions. We
present a rigorous statistical analysis of the main geometric characteristics
and discuss their mutual interrelationships. Our results demonstrate the
fundamental importance of cost-efficiency constraints for in time evolution of
urban road networks.Comment: 16 pages; 8 figure