13 research outputs found
A model for cascading failures in complex networks
Large but rare cascades triggered by small initial shocks are present in most
of the infrastructure networks. Here we present a simple model for cascading
failures based on the dynamical redistribution of the flow on the network. We
show that the breakdown of a single node is sufficient to collapse the
efficiency of the entire system if the node is among the ones with largest
load. This is particularly important for real-world networks with an highly
hetereogeneous distribution of loads as the Internet and electrical power
grids.Comment: 4 pages, 4 figure
Sandpiles on multiplex networks
We introduce the sandpile model on multiplex networks with more than one type
of edge and investigate its scaling and dynamical behaviors. We find that the
introduction of multiplexity does not alter the scaling behavior of avalanche
dynamics; the system is critical with an asymptotic power-law avalanche size
distribution with an exponent on duplex random networks. The
detailed cascade dynamics, however, is affected by the multiplex coupling. For
example, higher-degree nodes such as hubs in scale-free networks fail more
often in the multiplex dynamics than in the simplex network counterpart in
which different types of edges are simply aggregated. Our results suggest that
multiplex modeling would be necessary in order to gain a better understanding
of cascading failure phenomena of real-world multiplex complex systems, such as
the global economic crisis.Comment: 7 pages, 7 figure
Cascade-based attacks on complex networks
We live in a modern world supported by large, complex networks. Examples
range from financial markets to communication and transportation systems. In
many realistic situations the flow of physical quantities in the network, as
characterized by the loads on nodes, is important. We show that for such
networks where loads can redistribute among the nodes, intentional attacks can
lead to a cascade of overload failures, which can in turn cause the entire or a
substantial part of the network to collapse. This is relevant for real-world
networks that possess a highly heterogeneous distribution of loads, such as the
Internet and power grids. We demonstrate that the heterogeneity of these
networks makes them particularly vulnerable to attacks in that a large-scale
cascade may be triggered by disabling a single key node. This brings obvious
concerns on the security of such systems.Comment: 4 pages, 4 figures, Revte
Integrating fluctuations into distribution of resources in transportation networks
We propose a resource distribution strategy to reduce the average travel time
in a transportation network given a fixed generation rate. Suppose that there
are essential resources to avoid congestion in the network as well as some
extra resources. The strategy distributes the essential resources by the
average loads on the vertices and integrates the fluctuations of the
instantaneous loads into the distribution of the extra resources. The
fluctuations are calculated with the assumption of unlimited resources, where
the calculation is incorporated into the calculation of the average loads
without adding to the time complexity. Simulation results show that the
fluctuation-integrated strategy provides shorter average travel time than a
previous distribution strategy while keeping similar robustness. The strategy
is especially beneficial when the extra resources are scarce and the network is
heterogeneous and lowly loaded.Comment: 14 pages, 4 figure
Crackling Noise
Crackling noise arises when a system responds to changing external conditions
through discrete, impulsive events spanning a broad range of sizes. A wide
variety of physical systems exhibiting crackling noise have been studied, from
earthquakes on faults to paper crumpling. Because these systems exhibit regular
behavior over many decades of sizes, their behavior is likely independent of
microscopic and macroscopic details, and progress can be made by the use of
very simple models. The fact that simple models and real systems can share the
same behavior on a wide range of scales is called universality. We illustrate
these ideas using results for our model of crackling noise in magnets,
explaining the use of the renormalization group and scaling collapses. This
field is still developing: we describe a number of continuing challenges
Load shedding strategies for preventing cascading failures in power grid
Load shedding has always been a commonly adopted method in emergency situations to maintain power system reliability. Several load reduction strategies have been suggested in the past but most are complex and not scalable. In this paper, we have proposed and thoroughly investigated three load shedding strategies to prevent cascading failures in power grid. The first strategy is a base line case called the homogeneous load shedding strategy. It reduces load homogeneously in all the buses of the system. This strategy is extremely simple and fast, and these properties motivate its use in some specific scenarios in spite of its inefficiencies. Next, to accurately find the location and amount of load shedding, we propose a linear optimization formulation which is much more efficient in overall load shedding in the system. A novel tree heuristic is proposed to overcome the drawbacks of the optimization, namely fairness and scalability. The tree heuristic is linear and very simple to implement. In general, it gives close to optimal results. The results of the tree strategy are compared with that of another existing heuristic and it is found that the tree performs equal to or better than the existing heuristic for all cases