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See detailStabilization of Collective Motion in Three Dimensions : A Consensus Approach
Scardovi, Luca; Leonard, Naomi; Sepulchre, Rodolphe ULg

in Proceedings of 46th IEEE Conference on Decision and Control (2007, December)

This paper proposes a methodology to stabilize relative equilibria in a model of identical, steered particles moving in three- dimensional Euclidean space. Exploiting the Lie group structure of the ... [more ▼]

This paper proposes a methodology to stabilize relative equilibria in a model of identical, steered particles moving in three- dimensional Euclidean space. Exploiting the Lie group structure of the resulting dynamical system, the stabilization problem is reduced to a consensus problem on the Lie algebra. The resulting equilibria correspond to parallel, circular and helical formations. We rst derive the stabilizing control laws in the presence of all-to-all communication. Providing each agent with a consensus estimator, we then extend the results to a general setting that allows for unidirectional and time-varying communication topologies. [less ▲]

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See detailProgresse-t-on en enseignement des langues étrangères?
Defays, Jean-Marc ULg

Scientific conference (2007, December)

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See detailFe-2(II)(PO4)(OH), a synthetic analogue of wolfeite
Hatert, Frédéric ULg

in Acta Crystallographica Section C-Crystal Structure Communications (2007), 63(Part 12), 119-121

This paper reports the hydrothermal synthesis and crystal structure refinement of diiron(II) phosphate hydroxide, Fe-2(II)(PO4)(OH), obtained at 1063 K and 2.5 GPa. This phosphate is the synthetic ... [more ▼]

This paper reports the hydrothermal synthesis and crystal structure refinement of diiron(II) phosphate hydroxide, Fe-2(II)(PO4)(OH), obtained at 1063 K and 2.5 GPa. This phosphate is the synthetic analogue of the mineral wolfeite, and has a crystal structure topologically identical to those of minerals of the triplite-triploidite group. The complex framework contains edge-and corner-sharing FeO4(OH) and FeO4(OH)(2) polyhedra, linked via corner-sharing to the PO4 tetrahedra (average P-O distances are between 1.537 and 1.544 angstrom). Four five-coordinated Fe sites are at the centers of distorted trigonal bipyramids (average Fe-O distances are between 2.070 and 2.105 angstrom), whereas the coordination environments of the remaining Fe sites are distorted octahedra (average Fe-O distances are between 2.146 and 2.180 angstrom). The Fe-O distances are similar to those observed in natural Mg-rich wolfeite, except for two Fe-O bond distances, which are significantly longer in synthetic Fe-2(2+) (PO4)(OH). [less ▲]

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See detailConsensus under general convexity
tuna, S. E.; Sepulchre, Rodolphe ULg

in Proceedings of the 46th IEEE Conference on Decision and Control (2007, December)

A method is proposed to characterize contraction of a set through orthogonal projections. For discrete-time multi-agent systems, quantitative estimates of convergence (to a consensus) rate are provided by ... [more ▼]

A method is proposed to characterize contraction of a set through orthogonal projections. For discrete-time multi-agent systems, quantitative estimates of convergence (to a consensus) rate are provided by means of contracting convex sets. Required convexity for the sets that should include the values that the transition maps of agents take is considered in a more general sense than that of Euclidean geometry. [less ▲]

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See detailCessation versus continuation of 6-month migraine preventive therapy with topiramate (PROMPT): a randomised, double-blind, placebo-controlled trial
Diener, Hans-Christoph; Agosti, Reto; Allais, Gianni et al

in Lancet Neurology (2007), 6(12), 1054-1062

Background Use of preventive therapy for migraine is often recommended for only 6-9 months, but no randomised, placebo-controlled trials have investigated migraine frequency after the end of prophylaxis ... [more ▼]

Background Use of preventive therapy for migraine is often recommended for only 6-9 months, but no randomised, placebo-controlled trials have investigated migraine frequency after the end of prophylaxis. We assessed the effects of discontinuation of topiramate after a treatment period of 6 months. Methods 818 patients who have migraines were enrolled from 88 clinics in 21 countries. After a 4-8-week lead-in period, patients received topiramate in a 26-week open-label phase. Daily dose was increased from 25 mg to 100 mg in steps of 25 mg every week; the dose could be adjusted further in the range 50-200 mg/day, but was stable for the final 4 weeks. Patients were randomly assigned to continue this dose or switch to placebo for a 26-week double-blind phase. The primary endpoint was the difference in number of days with migraine during the last 4 weeks of the double-blind phase compared with the last 4 weeks of the open-label phase. Analysis was by intention to treat. This trial is registered with EudraCT, number 2005-000321-29. Findings 559 patients (68.3%) completed the open-label phase; 514 entered the double-blind phase and were assigned to topiramate (n=255) or placebo (n=259). The mean increase in number of migraine days was greater in the placebo group (1.19 days in 4 weeks, 95% CI 0.71 to 1.66; p < 0.0001) than in the topiramate group (0.10, -0.36 to 0.56; p=0.5756; mean difference between groups -1.09, -1.75 to -0.43). Patients in the placebo group had a greater number of days on acute medication than did those in the topiramate group (mean difference between groups -0.95, -1.49 to -0.41; p=0.0007). Quality of life, as assessed by the MIDAS questionnaire, fell in the placebo group but remained stable in the topiramate group. Patients were more satisfied with the efficacy of topiramate than with that of placebo, whereas satisfaction with tolerability was similar in both treatment groups. Interpretation Sustained benefit was reported after discontinuation of topiramate, although number of migraine days did increase. These findings suggest that patients should be treated for 6 months, with the option to continue to 12 months in some patients. [less ▲]

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See detailAutonomous rigid body attitude synchronization
Sarlette, Alain ULg; Sepulchre, Rodolphe ULg; Leonard, Naomi

in Proceedings of the 46th IEEE Conference on Decision and Control (2007, December)

This paper studies some extensions to the decentralized attitude synchronization of identical rigid bodies. Considering fully actuated Euler equations, the communication links between the rigid bodies are ... [more ▼]

This paper studies some extensions to the decentralized attitude synchronization of identical rigid bodies. Considering fully actuated Euler equations, the communication links between the rigid bodies are limited and the available information is restricted to relative orientations and angular velocities. In particular, no leader nor external reference dictates the swarm's behavior. The control laws are derived using two classical approaches of nonlinear control - tracking and energy shaping. This leads to a comparison of two corresponding methods which are currently considered for distributed synchronization - consensus and stabilization of mechanical systems with symmetries. [less ▲]

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See detailObservations and asteroseismic analysis of the rapidly pulsating hot B subdwarf PG 0911+456
Randall, Suzanna K.; Green, Elizabeth M.; Van Grootel, Valérie ULg et al

in Astronomy and Astrophysics (2007), 476

Aims:The principal aim of this project is to determine the structural parameters of the rapidly pulsating subdwarf B star PG 0911+456 from asteroseismology. Our work forms part of an ongoing programme to ... [more ▼]

Aims:The principal aim of this project is to determine the structural parameters of the rapidly pulsating subdwarf B star PG 0911+456 from asteroseismology. Our work forms part of an ongoing programme to constrain the internal characteristics of hot B subdwarfs with the long-term goal of differentiating between the various formation scenarios proposed for these objects. So far, a detailed asteroseismic interpretation has been carried out for 6 such pulsators, with apparent success. First comparisons with evolutionary theory look promising, however it is clear that more targets are needed for meaningful statistics to be derived. Methods: The observational pulsation periods of PG 0911+456 were extracted from rapid time-series photometry using standard Fourier analysis techniques. Supplemented by spectroscopic estimates of the star's mean atmospheric parameters, they were used as a basis for the “forward modelling” approach in asteroseismology. The latter culminates in the identification of one or more “optimal” models that can accurately reproduce the observed period spectrum. This naturally leads to an identification of the oscillations detected in terms of degree ℓ and radial order k, and infers the structural parameters of the target. Results: The high S/N low- and medium resolution spectroscopy obtained led to a refinement of the atmospheric parameters for PG 0911+456, the derived values being T_eff = 31 940 ± 220 K, log g = 5.767 ± 0.029, and log He/H = -2.548 ± 0.058. From the photometry it was possible to extract 7 independent pulsation periods in the 150-200 s range with amplitudes between 0.05 and 0.8% of the star's mean brightness. There was no indication of fine frequency splitting over the 68-day time baseline, suggesting a very slow rotation rate. An asteroseismic search of parameter space identified several models that matched the observed properties of PG 0911+456 well, one of which was isolated as the “optimal” model on the basis of spectroscopic and mode identification considerations. All the observed pulsations are identified with low-order acoustic modes with degree indices ℓ = 0,1,2 and 4, and match the computed periods with a dispersion of only 0.26%, typical of the asteroseismological studies carried out to date for this type of star. The inferred structural parameters of PG 0911+456 are T_eff = 31 940 ± 220 K (from spectroscopy), log {g} = 5.777 ± 0.002, Mast/Msun = 0.39 ± 0.01, log{M_env/Mast} = -4.69 ± 0.07, R/Rsun = 0.133 ± 0.001 and L/Lsun = 16.4 ± 0.8. We also derive the absolute magnitude MV = 4.82 ± 0.04 and a distance d = 930.3 ± 27.4 pc. [less ▲]

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See detailIon Beam Induced Luminescence & Cultural Heritage
Calvo Del Castillo, Helena ULg

Scientific conference (2007, December)

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See detailPredatory boreholes in Tournaisian (Lower Carboniferous) spiriferid brachiopods
Mottequin, Bernard ULg; Sevastopulo, George

in Budd, G. E.; Streng, M.; Daley, A. C. (Eds.) et al Programme with abstracts of the 51st Palaeontological Association Annual Meeting (2007, December)

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See detailInternet Topology Discovery: a Survey
Donnet, Benoît ULg; Friedman, Timur

in IEEE Communications Surveys and Tutorials (2007), 9(4), 2-15

Since the beginning of the nineties, the internet has undergone impres- sive growth. This growth can be appreciated in terms of the equipment, such as routers and links, that has been added, as well as in ... [more ▼]

Since the beginning of the nineties, the internet has undergone impres- sive growth. This growth can be appreciated in terms of the equipment, such as routers and links, that has been added, as well as in the numbers of users and the value of commerce that it supports. In parallel to this expansion, over the past decade the networking research community has shown a growing interest in discovering and analyzing the internet topology. Some researchers have developed tools for gathering network topology data while others have tried to understand and model the internet’s properties. These efforts have brought us to a crucial juncture for toplogy measurement infrastructures: while, previously, these were both small (in terms of number of measurement points) and monolithic, we are starting to see the deployment of large-scale distributed systems composed of hundreds or thousands of monitors. As we look forward to this next generation of systems, we take stock of what has been achieved so far. In this survey, we discuss past and current mechanisms for discovering the internet topology at various levels: the IP interface, the router, the AS, and the PoP level. In addition to discovery techniques, we provide insights into some of the well- known properties of the internet topology. [less ▲]

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See detailLa circonscription fédérale : un placebo administré à un malade incurable?
Bouhon, Frédéric ULg

E-print/Working paper (2007)

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See detailLa personnalité borderline: clinique d'une psychopathologie "sans limites"
Debabeche, Cécile ULg; Lebas, Maud ULg; Triffaux, Jean-Marc ULg

in Revue Médicale de Liège (2007), 62(12), 730-5

The borderline personality disorder is a common psychiatric entity, which is characterized by a varied symptomatology and a significant comorbidity. It seems that its etiologic is heterogeneous ... [more ▼]

The borderline personality disorder is a common psychiatric entity, which is characterized by a varied symptomatology and a significant comorbidity. It seems that its etiologic is heterogeneous, comprising psychosocial factors as much as biological and genetic. So the best approach of the borderline personality disorder would be a multidisciplinary bio-psycho-social one. Through a clinical case, we illustrate this disorder and its treatment in outpatient clinic. [less ▲]

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See detailLe financement public des cultes et de la laïcité
Husson, Jean-François ULg

in Politique : Revue de Débats (2007), (52), 14-17

This article summarizes the public financing of religious and philosophical communities in Belgium. It discusses the way theses means are shared and the future of this model.

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See detailIntussen aan de kersttafel...
Ozer, Pierre ULg; Perrin, Dominique ULg

Article for general public (2007)

De afgelopen weken heb ik de reclamefolders van mijn dichtstbijzijnde hypermarkt uitgeplozen om een fijn dineetje samen te stellen. Hierna volgt het resultaat voor acht personen, met tussen haakjes het ... [more ▼]

De afgelopen weken heb ik de reclamefolders van mijn dichtstbijzijnde hypermarkt uitgeplozen om een fijn dineetje samen te stellen. Hierna volgt het resultaat voor acht personen, met tussen haakjes het aantal kilometers dat elk ingrediënt heeft afgelegd om naar België te komen en de hoeveelheid CO2 in kilogram die het transport geproduceerd heeft. Ik heb vooral ingrediënten gekozen die met het vliegtuig worden aangevoerd, want luchttransport produceert gemiddeld zestig keer meer CO2 dan vervoer over zee. [less ▲]

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See detailImplementation and Preliminary Evaluation of an ISP-Driven Informed Path Selection
Saucez, Damien; Donnet, Benoît ULg; Bonaventure, Olivier

in ACM CoNEXT conference (2007, December)

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See detailNoël en famille ou 15 litres de pétrole
Ozer, Pierre ULg; Perrin, Dominique ULg

Article for general public (2007)

La semaine précédant Noël, j’ai décortiqué les publicités de mon hypermarché le plus proche pour préparer le repas familial tant attendu. Et voici ce que j’ai pu concocter pour huit personnes avec, entre ... [more ▼]

La semaine précédant Noël, j’ai décortiqué les publicités de mon hypermarché le plus proche pour préparer le repas familial tant attendu. Et voici ce que j’ai pu concocter pour huit personnes avec, entre parenthèses, les kilomètres parcourus entre le pays de production et la Belgique ainsi que les kilogrammes de CO2 émis uniquement pour le transport aérien intercontinental de ces produits achetés. L’analyse se focalise sur le transport par voie aérienne puisque celui-ci émet, en moyenne, 60 fois plus de CO2 que le transport par voie maritime. [less ▲]

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