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We study a graph-augmentation problem arising from a technique applied in recent approaches for route planning. Many such methods enhance the graph by inserting shortcuts, i.e., additional edges (u, v) such that the length of (u, v) is the distance from u to v. Given a weighted, directed graph G and a number c ∈ Z >0 , the shortcut problem asks how to(More)
Maximizing the quality index <i>modularity</i> has become one of the primary methods for identifying the clustering structure within a graph. Since many contemporary networks are not static but evolve over time, traditional static approaches can be inappropriate for specific tasks. In this work, we pioneer the NP-hard problem of online dynamic modularity(More)
Clustering a graph means identifying internally dense subgraphs that are only sparsely interconnected. Formalizations of this notion lead to measures that quantify the quality of a clustering and to algorithms that actually find clusterings. Since, most generally, corresponding optimization problems are hard, heuristic clustering algorithms are used in(More)
Collaboration networks arise when we map the connections between scientists which are formed through joint publications. These networks thus display the social structure of academia, and also allow conclusions about the structure of scientific knowledge. Using the computer science publication database DBLP, we compile relations between authors and(More)
Radiographic simulation of thick components represents a particular challenge, since the Monte-Carlo methods generally applied to obtain accurate scattering predictions are inherently slow, and as such not suited to applications for inspection procedure qualification, where a large number of parameter variations has to be studied in a reasonable time. We(More)
One of the problems in modelling radiographic inspections concerns the film characteristics as the last step in the radiographic modelling chain, throughout which the energy deposited by the incoming radiation is to be converted to a grey value. This conversion depends not only on the total dose absorbed by the film, but also on the radiation's spectrum and(More)
A new gamma or X-Ray simulation module has been integrated to the CIVA software and completes the already available UT and ECT. This module is based on a combination of NDT radiographic modules developed at the CEA LETI and at EDF R&D. Direct radiation is calculated from an analytical way (ray tracer and Beer-Lambert law for the attenuation) while the(More)
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