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Detecting a Suddenly Arriving Dynamic Profile of Finite Duration
No full textInternational audienceThis paper addresses the detection of a suddenly arriving dynamic profile of a finite duration often called a transient change. In contrast to the traditional abrupt change detection, where the post-change period is assumed to be infinitely long, the detection of a suddenly arriving transient change should be done before it disappears. The detection of transient changes after their disappearance is considered as missed. Hence, the traditional quickest change detection criterion, minimizing the average detection delays provided a prescribed false alarm rate, is compromised. The proposed optimality criterion minimizes the worst case probability of missed detection provided that the worst case probability of false alarm during a certain period is upper bounded. A suboptimal CUSUM-type transient change detection algorithm, based on a subclass of truncated Sequential Probability Ratio Tests, is proposed. The optimization of the proposed algorithm in this subclass leads to a specially designed Finite Moving Average Test. The proposed method is analyzed theoretically and by simulation. A special attention is paid to the case of Gaussian observations with a dynamic profile
A Low-cost, High-coverage Legal Named Entity Recognizer, Classifier and Linker
No full textInternational audienceIn this paper, we try to improve Information Extraction in legal texts by creating a legal Named Entity Recognizer, Classifier and Linker. With this tool, we can identify relevant parts of texts and connect them to a structured knowledge representation, the LKIF ontology.More interestingly, this tool has been developed with relatively little effort, by mapping the LKIF ontology to the YAGO ontology and through it, taking advantage of the mentions of entities in the Wikipedia. These mentions are used as manually annotated examples to train the Named Entity Recognizer, Classifier and Linker.We have evaluated the approach on holdout texts from the Wikipedia and also on a small sample of judgments of the European Court of Human Rights, resulting in a very good performance, i.e., around 80% F-measure for different levels of granularity. We present an extensive error analysis to direct further developments, and we expect that this approach can be successfully ported to other legal subdomains, represented by different ontologies
Verba sonandi des cris des animaux: métaphorisation et traitement automatique des données
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Recovery of disrupted airline operations using k-Maximum Matching in graphs
No full textInternational audienceBy Berge's theorem, finding a maximum matching in a graph relies on the use of augmenting paths. When no further constraint is added, Edmonds' algorithm allows to compute a maximum matching in polynomial time by sequentially augmenting such paths. Motivated by applications in the scheduling of airline operations, we consider a similar problem where only paths of bounded length can be augmented. Precisely, let k ≥ 1 be an odd integer, a graph G and a matching M of G. What is the maximum size of a matching that can be obtained from M by using only augmenting paths of length at most k? We first prove that this problem can be solved in polynomial time for k ≤ 3 in any graph and that it is NP-complete for any fixed k ≥ 5 in the class of planar bipartite graphs of degree at most 3 and arbitrarily large girth. We then prove that this problem is in P, for any k, in several subclasses of trees such as caterpillars or trees with all vertices of degree at least 3 " far appart ". Moreover, this problem can be solved in time O(n) in the class of n-node trees when k and the maximum degree are fixed parameters. Finally, we consider a more constrained problem where only paths of length exactly k can be augmented. We prove that this latter problem becomes NP-complete for any fixed k ≥ 3 and in trees when k is part of the input
Design and Analysis of two Stream Ciphers Based on Chaotic Coupling and Multiplexing techniques
No full textInternational audienceIn this paper, we design and implement two new stream ciphersbased on Pseudo Chaotic Number Generators (PCNGs) which integrate dis-crete chaotic maps, namely, Piecewise Linear Chaotic Map (PWLCM), Skew-tent and Logistic map. They are weakly coupled by a predened matrix A forthe rst PCNG and they are coupled by a binary diusion matrix D for thesecond one. Each PCNG includes a chaotic multiplexing technique that allowsthe enhancement of the robustness of the system. The structure is implementedwith nite precision N = 32 bits in C language. Security performance of theproposed stream ciphers is analysed and several cryptanalytic and statisticaltests are applied. Experimental results highlight robustness as well as eciencyin terms of computation time of these two stream ciphers
Decoding the origins of vertical land motions observed today at coasts
No full textInternational audienceIn recent decades, geodetic techniques have allowed detecting vertical land motions and sea-level changes of a few millimetres per year, based on measurements taken at the coast (tide gauges), on board of satellite platforms (satellite altimetry) or both (Global Navigation Satellite System). Here, contemporary vertical land motions are analysed from January 1993 to July 2013 at 849 globally distributed coastal sites. The vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic Green’s functions. Special attention is paid to the effects of glacial isostatic adjustment induced by past and present-day ice melting. Various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally. In well-instrumented regions, predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres. Residual vertical land motions show a strong local variability, especially in the vicinity of plate boundaries due to the earthquake cycle. Significant residual signals are also observed at scales of a few hundred kilometres over nine well-instrumented regions forming observation windows on unmodelled geophysical processes. This study highlights the potential of our multitechnique database to detect geodynamical processes, driven by anthropogenic influence, surface mass changes (surface loading and glacial isostatic adjustment) and tectonic activity (including the earthquake cycle, sediment and volcanic loading, as well as regional tectonic constraints). Future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models
Formation and coarsening of roll-waves in shear shallow water flows down an inclined rectangular channel
No full textInternational audienceThe formation of a periodic roll-wave train in a long channel is studied for two sets of experimental parameters (noted as Case 1 and Case 2) corresponding to Brock's experiments [3], [4]. In both cases, a formed free surface profile was found in a very good agreement with the experimental results. Mathematical properties of the model were also tested in the case where the perturbation frequency was lower than the experimental one, so longer waves were generated at the channel inlet. It was observed that the amplitude and the enstrophy of the corresponding roll-waves train are strongly modulated. In the case where the waves of two different lengths were generated at the channel inlet, the coarsening was observed. The coarsening phenomenon is always accompanied by a strong modulation. A comparison with the Saint-Vennat equations is also done. The formation of a single wave composing a roll-wave train was also studied in a domain with periodic boundary conditions (called " periodic box ") for the same sets of experimental parameters. The free surface profile was found also in a very good agreement with the experimental results. This allows us to justify the use of the " periodic box " as a simple mathematical tool for a qualitative study of roll-waves stability. In particular, we studied the stability of a single steady wave by increasing its length. It was shown that the wave becomes morphologically unstable after some critical wave length : it transforms into a system containing several waves. It is also proved that a single steady wave corresponding to Case 1 is stable under multi-dimensional perturbations in the framework of a model which is a simplification of a general multi-D model of shear shallow water flows
From the seismic cycle to long-term deformation: linking seismic coupling and Quaternary coastal geomorphology along the Andean megathrust
No full textInternational audienceMeasurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the subduction interface and may also show up in the fore-arc morphology. To investigate this hypothesis, we compiled information on the extent of earthquake ruptures for the last 500 years and uplift rates derived from dated marine terraces along the South American coastline from central Peru to southern Chile. We additionally calculated a new interseismic coupling model for that same area based on a compilation of GPS data. We show that the coastline geometry, characterized by the distance between the coast and the trench; the latitudinal variations of long-term uplift rates; and the spatial pattern of interseismic coupling are correlated. Zones of faster and long-term permanent coastal uplift, evidenced by uplifted marine terraces, coincide with peninsulas and also with areas of creep on the megathrust where slip is mostly aseismic and tend to arrest seismic ruptures. We conclude that spatial variations of frictional properties along the megathrust dictate the tectono-geomorphological evolution of the coastal zone and the extent of seismic ruptures along strike
