Publications ORBi OA
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See detailLifting, Superadditivity, Mixed Integer Rounding and Single Node Flow Sets Revisited
Louveaux, Quentin ULg; Wolsey, Laurence A.

in 4OR : Quarterly Journal of the Belgian, French and Italian Operations Research Societies (2003), 1

In this survey we attempt to give a unified presentation of a variety of results on the lifting of valid inequalities, as well as a standard procedure combining mixed integer rounding with lifting for the ... [more ▼]

In this survey we attempt to give a unified presentation of a variety of results on the lifting of valid inequalities, as well as a standard procedure combining mixed integer rounding with lifting for the development of strong valid inequalities for knapsack and single node flow sets. Our hope is that the latter can be used in practice to generate cutting planes for mixed integer programs. The survey contains essentially two parts. In the first we present lifting in a very general way, empha- sizing superadditive lifting which allows one to lift simultaneously different sets of variables. In the second, our procedure for generating strong valid inequalities consists of reduction to a knapsack set with a single continuous variable, construc- tion of a mixed integer rounding inequality, and superadditive lifting. It is applied to several generalizations of the 0-1 single node flow set. [less ▲]

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See detailPhotoabsorption Spectroscopy at medium Resolution. The C2HXYZ (XYZ= H, F, Cl and/or Br) Molecules.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H - on CD-ROM (2003)

The V-UV photoabsorption spectra of 1,1-C2H2F2, C2HBrF2 and C2HClF2 have been recorded by using synchrotron radiation and are reported.

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See detailApplication of a damage model to an aluminium alloy
Castagne, Sylvie; Habraken, Anne ULg; Cescotto, Serge ULg

in International Journal of Damage Mechanics (2003), 12(1), 5-30

An energy-based isotropic elastoplastic model coupled to damage is implemented in the finite element code LAGAMINE developed for more than fifteen years in the MSM department. In this model, based on the ... [more ▼]

An energy-based isotropic elastoplastic model coupled to damage is implemented in the finite element code LAGAMINE developed for more than fifteen years in the MSM department. In this model, based on the local approach of ductile fracture, effective stresses associated to damage variables are introduced. The damage law allows a continuous description of crack appearance. After a brief description of the model, its identification and its validation for an aluminum alloy are presented. Finally, the research of a global rupture criterion associated to this model is introduced. [less ▲]

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See detailA new formulation of internal forces for non-linear hypoelastic constitutive models verifying conservation laws
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg et al

in Bathe, K. J. (Ed.) Second MIT Conference on Fluid and Solid Mechanics (2003)

This paper proposes a new formulation of the internal forces for hypoelastic constitutive models ensuring that the elastic work of deformation can be restored by the scheme. Moreover, we demonstrate that ... [more ▼]

This paper proposes a new formulation of the internal forces for hypoelastic constitutive models ensuring that the elastic work of deformation can be restored by the scheme. Moreover, we demonstrate that the work of the plastic deformation is positive and consistent with the material model. [less ▲]

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See detailDevelopment of a Mesoscopic Cell Modeling the Damage Process in Steel at Elevated Temperature
Castagne, Sylvie; Remy, M.; Habraken, Anne ULg

in Key Engineering Materials [=KEM] (2003), 233-236

An on going project whose goal is the development and identification of a mathematical model of steel at elevated temperature using a mesoscopic approach is presented. The research aims to study the ... [more ▼]

An on going project whose goal is the development and identification of a mathematical model of steel at elevated temperature using a mesoscopic approach is presented. The research aims to study the damage process at elevated temperature using information from the macroscopic and mesoscopic scales. As a final application our results will be used to study the industrial process of continuous casting of low carbon steel. [less ▲]

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See detailClinching joining system: validation of numerical models
Pietrapertosa, C.; Zhang, Lihong ULg; Habraken, Anne ULg et al

in Brucato, V. (Ed.) Proceedings of the 6th International ESAFORM Conference on Material Forming (2003)

The clinching process, also known as “press joining”, is a mechanical joining technique for sheet metal. Its basic principle is to clamp together several metal sheets by an impact extrusion between a ... [more ▼]

The clinching process, also known as “press joining”, is a mechanical joining technique for sheet metal. Its basic principle is to clamp together several metal sheets by an impact extrusion between a punch and a die. The joint is formed by a localized cold plastic deformation. Forming is used as a joining method. Within the context of this research, University of Liège is developing numerical models, with the FEM code LAGAMINE, that simulate the clinching process. On the other hand, shear tests on simple joints with one or two clinches were realized and their behaviour is reproduced numerically with LAGAMINE. This work opens the way to the analytical formulation of the behaviour of clinched joints. The article will focus on comparisons between experiments and numerical simulations. First, the identification of model parameters will be explained. Then, the predicted failure modes will be analysed by comparison with the xperiments. [less ▲]

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See detailManaging Pests : consumers and commitments: The case of apple and pear growers in Belgium's Lower Meuse Region
Collet, Eric; Mormont, Marc ULg

in Environment & Planning A (2003), 35(3), 413-427

The authors analyse the construction of a seed fruit market. The conventional market had led to the 'anonymousness' of the fruit and to disconnected temporalities. The process needs new types of ... [more ▼]

The authors analyse the construction of a seed fruit market. The conventional market had led to the 'anonymousness' of the fruit and to disconnected temporalities. The process needs new types of coordination and components within the common information channels and actors' network. It also needs the construction of a new contract between producers and consumers, that the conventional market is unable to allow. Producers are experimenting with direct contact with the final consumer to find ways of allowing it. The fruit is replaced in the subject's experience of the final consumer and in the grower's story. The grower's story deals with managing pests, consumers, and commitments through a harmless action: eating a pear or an apple. [less ▲]

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See detailLa sous-traitance internationale : questions choisies
Wautelet, Patrick ULg

in Commisison droit et vie des affaires (Ed.) La sous-traitance (2003)

In this paper, a general overview is given of the legal problems arising in the context of cross-border subcontracting operations. Particular attention is paid to the difficulties arising out of the fact ... [more ▼]

In this paper, a general overview is given of the legal problems arising in the context of cross-border subcontracting operations. Particular attention is paid to the difficulties arising out of the fact that the sub-contracting agreement is intertwined with the main contracting agreement [less ▲]

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See detailNumerical shear tests for different elasto-plastic laws
de Montleau, P.; Duchene, Laurent ULg; Flores, Paulo et al

in Onate, E.; Owen, D. R. J. (Eds.) Proceedings of the VII International Conference on Computational Plasticity (COMPLAS 2003) (2003)

This paper presents the numerical simulation of a cyclic simple shear test. The blank tested is a high strength steel sheet for which we use three different constitutive plastic laws derived from Teodosiu ... [more ▼]

This paper presents the numerical simulation of a cyclic simple shear test. The blank tested is a high strength steel sheet for which we use three different constitutive plastic laws derived from Teodosiu's model. These laws take into account respectively isotropic, kinematic and mixed isotropic-kinematic hardening. The goal of the paper is to provide a first numerical idea of the stress-strain path in the center of an experimental test sample. [less ▲]

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See detailUne méthode générique pour la classification automatique d'images à partir des pixels
Marée, Raphaël ULg; Geurts, Pierre ULg; Wehenkel, Louis ULg

in Revue des Nouvelles Technologies de l'Information (2003), 1

Dans cet article, nous évaluons une approche générique de classification automatique d'images. Elle repose sur une méthode d'apprentissage récente qui construit des ensembles d'arbres de décision par ... [more ▼]

Dans cet article, nous évaluons une approche générique de classification automatique d'images. Elle repose sur une méthode d'apprentissage récente qui construit des ensembles d'arbres de décision par sélection aléatoire des tests directement sur les valeurs basiques des pixels. Nous proposons une variante, également générique, qui réalise une augmentation fictive de la taille des échantillons par extraction et classification de sous-fenêtres des images. Ces deux approches sont évaluées et comparées sur quatre bases de données publiques de problèmes courants: la reconnaissance de chiffres manuscrits, de visages, d'objets 3D et de textures. [less ▲]

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See detailUnimolecular Dissociation of Halogenobenzene Cations by Phase space Theory.
Gridelet, E.; Lorquet, Jean-Claude ULg; Locht, Robert ULg et al

in Anton, J.; Cedrequist, H.; Larsson, M. (Eds.) et al 23rd International Conference on Photonic, Electronic and Atomic Collisions: Book of Abstracts. (2003)

The Orbiting Transition State version of the Phase Space Theory (PST) is used to calculate the KER distributions in the dissociation channel of X (X=I,Cl,Br)-loss from C6H5X+. The results are compared to ... [more ▼]

The Orbiting Transition State version of the Phase Space Theory (PST) is used to calculate the KER distributions in the dissociation channel of X (X=I,Cl,Br)-loss from C6H5X+. The results are compared to the experimental distribution and to that obtained by PST. [less ▲]

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See detailHow ergodic is the Fragmentation of the Pyridine Cation ? A Maximum Entropy Ananlysis
Gridelet, E.; Locht, Robert ULg; Lorquet, Andrée ULg et al

in Anton, J.; Cederquist, H.; Larsson, M. (Eds.) et al 23rd International Conference on the Photonic, Electronic and Atomic Collisions: Book of Abstracts. (2003)

The experimental KER and the statistical distributions are compared by the Maximum Entropy Method. An Ergodicity Index F(E) is defined to measure the phase space sampling efficiency. This is applied to ... [more ▼]

The experimental KER and the statistical distributions are compared by the Maximum Entropy Method. An Ergodicity Index F(E) is defined to measure the phase space sampling efficiency. This is applied to the KERD of C4H4+ cation produced by the C5H5N+ -> HCN+C4H4+ fragmentation path. In this particular case the F(E) is found to decrease steadily with increasing internal energy. [less ▲]

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See detailAlgorithmes de contournement de barrières
Briquet, Cyril ULg

Master of advanced studies dissertation (2003)

GIS (Geographical Information Systems) bring an ever increasing range of solutions to decision makers seeking ever more accurate situational awareness in the issues they are facing. In particular, a GIS ... [more ▼]

GIS (Geographical Information Systems) bring an ever increasing range of solutions to decision makers seeking ever more accurate situational awareness in the issues they are facing. In particular, a GIS can provide a broad range of visual information resulting from computations that may be complex. These require to develop and implement efficient algorithms because of the massive amount of computations or data that are induced by the geographical nature of the processed data. The Urban and Rural Planning and Study Lab of University of Liege seeks to compute accessibility profiles for so-called "slow transport modes" in the Walloon Region. In this context, a relevant issue of computation of a socio-economical index based on spatial and population data is considered. The objective of this work is to modelize a problem of computation accessibility index, then solve it. The central part consists of the developement of a consistent and efficient algorithm chain to compute optimal shortest paths in geographical zones by avoiding barriers. The integration of the involved algorithms as well as the exploitation of intermediary results are fundemental aspects of the proposed solution. Two variants of the problem are modelized: DLOSP (Discrete Line-Of-Sight Paths, that does not take barriers into account) and DGSP (Discrete Geodesic Shortest Paths, that takes barriers into account). The detection and indexation of the barrieres, the refitting of the considered search space, the optimization of visibility requests and the computation of shortest paths constitute the main steps of the proposed algorithm chain. A distributed computing setup, naturally stemming from the structure of the problem itself, is briefly presented. [less ▲]

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See detailLa possible modification de la procédure de révision de la Constitution belge
Behrendt, Christian ULg

in Revue Française de Droit Constitutionnel (2003)

The article examines the question whether it is appropriate to alter the current amendment procedure of the Belgian constitution. Furthermore, the articles enquires into the possible design of a new ... [more ▼]

The article examines the question whether it is appropriate to alter the current amendment procedure of the Belgian constitution. Furthermore, the articles enquires into the possible design of a new amendment procedure. [less ▲]

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See detailLiège-Paris 1848 : Littérature, féminisme et Révolution
Droixhe, Daniel ULg

in Bulletin de l'Académie Royale de Langue et de Littérature Françaises (2003), LXXXI(1-2), 41-49

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See detailCacophonie jurisprudentielle autour de la notion d’impôt
Rosoux, Géraldine ULg

in Revue de Jurisprudence de Liège, Mons et Bruxelles (2003)

The article analyzes a decision of the Belgian judicial Supreme Court concerning the concept of "tax", and emphasizes the conflict between this decision and the case-law of the Belgian constitutional Court

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See detailLeçons de l’éphémère. La Cour d’arbitrage et le "Renouveau’ électoral" – La Cour d’arbitrage et la suspension
Rosoux, Géraldine ULg

in Revue Belge de Droit Constitutionnel (2003)

The articles analyzes the electoral reform of 2003 and points out the competence of the Belgian constitutional Court to suspend legislative norms.

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See detailDe "l'incapacité littéraire des Belges". Complexe national et contrefaçon
Droixhe, Daniel ULg; Ledain, O.

in Bertrand, Jean-Pierre; Biron, M.; Denis, Benoît (Eds.) et al Histoire de la littérature belge (1830-2000) (2003)

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See detailEvent-related potentials to emotional and neutral stimuli in alcoholism.
Hansenne, Michel ULg; Olin, Cecile; Pinto, Emmanuel ULg et al

in Neuropsychobiology (2003), 48(2), 77-81

Several studies have demonstrated that the emotional value of stimuli affects P300 amplitude. In the present study, the influence of alcohol-related stimuli in alcoholic patients was investigated ... [more ▼]

Several studies have demonstrated that the emotional value of stimuli affects P300 amplitude. In the present study, the influence of alcohol-related stimuli in alcoholic patients was investigated. Subjects were 10 alcoholic inpatients (3 female) and 10 age- and sex-matched controls. Eight alcohol-related and 8 neutral words served as stimuli in a visual oddball paradigm. Acohol-related words were targets (48 stimuli, 33%) and neutral words were standard stimuli (96 stimuli, 66%). Results showed that P300 amplitude for targets did not differ significantly between the two groups. However, P300 latency for targets as well as reaction time were significantly shorter in male alcoholic patients. In contrast, P300 latency was increased in female alcoholic patients but reaction time did not differ. These results suggest that male alcoholics process information linked to alcohol cues more rapidly than neutral cues, probably because a specific semantic network is activated in these patients. The decreased reaction time confirms the impulsive behavior frequently found in male alcoholism, as it has been described in type II alcoholism. Besides, the results imply that information processing was delayed in female alcoholic patients. Therefore this study demonstrates a gender-dependent impact of alcohol-related stimuli on information processing. [less ▲]

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See detailHarm avoidance is related to mismatch negativity (MMN) amplitude in healthy subjects
Hansenne, Michel ULg; Pinto, Emmanuel ULg; Scantamburlo, Gabrielle ULg et al

in Personality & Individual Differences (2003), 34(6), 1039-1048

Event-related potential (ERP) studies evidenced that some personality dimensions induced different controlled cognitive attitudes towards the processing of information. However, few data are available on ... [more ▼]

Event-related potential (ERP) studies evidenced that some personality dimensions induced different controlled cognitive attitudes towards the processing of information. However, few data are available on the possible relationships between personality and automatic attention or early sensory processing. In the present study the relationships between the mismatch negativity (MMN) and personality described by the Cloninger model of personality were investigated. Subjects were 32 healthy volunteers. The MMN was recorded with frequent stimuli tones of 1470 Hz, 70 dB and 40 ms duration, and target (20%) tones of 1470 Hz, 70 dB, 80 ms duration. The subjects completed a French version of the 226-item self-questionnaire TCI within the day following psychophysiological recording. The results showed that the HA dimension was negatively correlated with the MMN amplitude. The association was more present among women than men. No significant relationship existed between the other dimensions of personality and either the MMN amplitude or latency. These findings suggest that the MMN is related to the behavioral inhibition system (BIS), a fact which is consistent with clinical studies conducted on schizophrenia and anxiety disorders. In conclusion, this study suggests that personality dimensions induce different automatic attitudes towards the processing of information. (C) 2002 Published by Elsevier Science Ltd. [less ▲]

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