1,078 research outputs found
Vulnerability and Protection of Critical Infrastructures
Critical infrastructure networks are a key ingredient of modern society. We
discuss a general method to spot the critical components of a critical
infrastructure network, i.e. the nodes and the links fundamental to the perfect
functioning of the network. Such nodes, and not the most connected ones, are
the targets to protect from terrorist attacks. The method, used as an
improvement analysis, can also help to better shape a planned expansion of the
network.Comment: 4 pages, 1 figure, 3 table
Exploiting Resolution-based Representations for MaxSAT Solving
Most recent MaxSAT algorithms rely on a succession of calls to a SAT solver
in order to find an optimal solution. In particular, several algorithms take
advantage of the ability of SAT solvers to identify unsatisfiable subformulas.
Usually, these MaxSAT algorithms perform better when small unsatisfiable
subformulas are found early. However, this is not the case in many problem
instances, since the whole formula is given to the SAT solver in each call. In
this paper, we propose to partition the MaxSAT formula using a resolution-based
graph representation. Partitions are then iteratively joined by using a
proximity measure extracted from the graph representation of the formula. The
algorithm ends when only one partition remains and the optimal solution is
found. Experimental results show that this new approach further enhances a
state of the art MaxSAT solver to optimally solve a larger set of industrial
problem instances
From sand to networks: a study of multi-disciplinarity
In this paper, we study empirically co-authorship networks of neighbouring
scientific disciplines, and describe the system by two coupled networks. By
considering a large time window, we focus on the properties of the interface
between the disciplines. We also focus on the time evolution of the
co-authorship network, and highlight a rich phenomenology including first order
transition and cluster bouncing and merging. Finally, we present a ferro-
electric-like model (CDIM), involving bond redistribution between the nodes,
that reproduces qualitatively the structuring of the system in homogeneous
phasesComment: submitted to europhys. let
External Periodic Driving of Large Systems of Globally Coupled Phase Oscillators
Large systems of coupled oscillators subjected to a periodic external drive
occur in many situations in physics and biology. Here the simple, paradigmatic
case of equal-strength, all-to-all sine-coupling of phase oscillators subject
to a sinusoidal external drive is considered. The stationary states and their
stability are determined. Using the stability information and numerical
experiments, parameter space phase diagrams showing when different types of
system behavior apply are constructed, and the bifurcations marking transitions
between different types of behavior are delineated. The analysis is supported
by results of direct numerical simulation of an ensemble of oscillators
Edge based stochastic block model statistical inference
Community detection in graphs often relies on ad hoc algorithms with no clear
specification about the node partition they define as the best, which leads to
uninterpretable communities. Stochastic block models (SBM) offer a framework to
rigorously define communities, and to detect them using statistical inference
method to distinguish structure from random fluctuations. In this paper, we
introduce an alternative definition of SBM based on edge sampling. We derive
from this definition a quality function to statistically infer the node
partition used to generate a given graph. We then test it on synthetic graphs,
and on the zachary karate club network
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