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See detailLe projet de plate-forme électronique de construction et de gestion qualité de tests standardisés e-C&QCST
Gilles, Jean-Luc ULg; Piette, Sylvie-Anne ULg; Detroz, Pascal ULg et al

in Arzola, S. (Ed.) World education for educational research (WAER) : XIV congreso mundial de ciencias de la educacion : educatores para una nueva cultura : summary of papers abstracts (2004)

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See detailInfluence of morphological characteristics of heterogeneous moraine formations on their mechanical behaviour using image and statistical analysis
Lebourg, Thomas; Riss, Joelle; Pirard, Eric ULg

in Engineering Geology (2004), 73(1-2), 37-50

The study of landslide stability on mountain slopes becomes more difficult when the sliding materials. are heterogeneous. This is a current problem with the old glacial moraines now under study in the ... [more ▼]

The study of landslide stability on mountain slopes becomes more difficult when the sliding materials. are heterogeneous. This is a current problem with the old glacial moraines now under study in the Aspe Valley, Pyrenees. Analysis of slope stability numerical models necessitates accurate data about mechanical and physical properties. Because moraines are very heterogeneous, a large sample is necessary, but, unfortunately, data acquisition costs a lot of time and money. Therefore, we would like to estimate mechanical properties from correlated variables that are easier to acquire (morphological variables using image analysis). Observations in the field and previous mechanical results in the laboratory have shown that differences between the behaviour of moraines seem to be related not only to their three-dimensional structure but also to the morphological and petrographical characteristics of their components. The moraines are classified based on textural characteristics at the sample scales based on the distributions of size and shape of their constitutive elements (blocks, matrix, etc.). Then, we study the statistical distribution of the variables to highlight the most significant variables. Next, we evaluate the results of the mechanical behaviour of the moraines, with the internal angle of friction and the effective cohesion. On seven specific moraines, we established relations between the effective internal angle of friction, the elongation factor and the roughness factor. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailThe contribution of 211 particles to the mechanical reinforcement mechanism of 123 superconducting single domains
Mathieu, Jean-Philippe; Cano, I. G.; Koutzarova, T. et al

in Superconductor Science and Technology (2004), 17(1), 169-174

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values ... [more ▼]

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values when performed in (001) planes rather than in planes parallel to the c-axis. Moreover, the cracks pattern around the indentation follows preferential orientation in planes parallel to the c-axis whereas a classical 'four-cracks' pattern is observed in the (001) planes. It has been possible to show the crucial role played by the 211 particles in the deviating mechanism of cracks and the relevance of the high homogeneity of 211-particle distribution in the material. [less ▲]

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See detailTesting Interactif Multimédia via Internet (TIMI) version 2.0
Gilles, Jean-Luc ULg; Lê, Hung; Pirson, Marc ULg

Software (2004)

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See detailVertical ionization energies of alpha-L-amino acids as a function of their conformation: an ab initio study
Dehareng, Dominique ULg; Dive, Georges ULg

in International Journal of Molecular Sciences (2004), 5(11-12, NOV-DEC), 301-332

Vertical ionization energies (IE) as a function of the conformation are determined at the quantum chemistry level for eighteen alpha-L-amino acids. Geometry optimization of the neutrals are performed ... [more ▼]

Vertical ionization energies (IE) as a function of the conformation are determined at the quantum chemistry level for eighteen alpha-L-amino acids. Geometry optimization of the neutrals are performed within the Density Functional Theory (DFT) framework using the hybrid method B3LYP and the 6-31G**(5d) basis set. Few comparisons are made with wave-function-based ab initio correlated methods like MP2, QCISD or CCSD. For each amino acid, several conformations are considered that lie in the range 10-15 kJ/mol by reference to the more stable one. Their IE are calculated using the Outer-Valence-Green's-Functions (OVGF) method at the neutrals' geometry. Few comparisons are made with MP2 and QCISD IE. It turns out that the OVGF results are satisfactory but an uncertainty relative to the most stable conformer at the B3LYP level persists. Moreover, the value of the IE can largely depend on the conformation due to the fact that the ionized molecular orbitals (MO) can change a lot as a function of the nuclear structure. [less ▲]

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See detailPetrogenesis of the Kabanga-Musongati layered mafic-ultramafic intrusions in Burundi (Kibaran Belt): geochemical, Sr-Nd isotopic constraints and Cr-Ni behaviour
Duchesne, Jean-Clair ULg; Liégeois, Jean-Paul ULg; Deblond, André et al

in Journal of African Earth Sciences (2004), 39

A succession of mafic-ultramafic layered intrusions forms an alignment in the boundary zone between the Kibaran belt and the Tanzania craton. The intrusions represent a continuous series of cumulate rocks ... [more ▼]

A succession of mafic-ultramafic layered intrusions forms an alignment in the boundary zone between the Kibaran belt and the Tanzania craton. The intrusions represent a continuous series of cumulate rocks. For instance, in the Mukanda-Buhoro and Musongati (MBM) contiguous bodies, the series starts with dunite and passes to lherzolite, pyroxenite, norite, gabbronorite and anorthosite on top. Cumulate textures are conspicuous in all rock types and cryptic layering characterises cumulus mineral compositions, thus evidencing fractional crystallization as a major differentiation mechanism. The increase of Cr in the ultramafic members of the series indicates that chromite was not a liquidus mineral in dunite and lherzolite rocks, thus unable to form chromitite layers. The high Ni-content of dunite seems to preclude the existence of conjugate Ni-rich sulphide deposits. The 87Sr/86Sr initial ratio is relatively constant and averages 0.7087, with some values up to 0.712 due to local assimilation. Fine-grained rocks from the MBM area are isotopically (Nd and Sr) similar to the MBM cumulates. Modelling their crystallization produces cumulus mineral compositions similar to those in the Musongati ultramafic rocks, which suggests a broadly picritic parental magma. On the other hand, fine-grained rocks from the Nyabikere area are not related to the Nyabikere cumulates. Nd and Sr isotope ratios show that the MBM magmatism is related to an enriched source, possibly an old subcontinental lithospheric mantle. The Nyabikere dykes, as well as the Waga dykes, come from a depleted mantle source, as do the A-type granitoids occurring in the same boundary zone. Several lines of evidence point to two types of parental magmas, a picritic magma, and a more evolved magma, broadly similar to the Bushveld Main Zone magma. [less ▲]

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See detailExtended formulations for Gomory Corner polyhedra
Köppe, Matthias ULg; Louveaux, Quentin ULg; Weismantel, Robert et al

in Discrete Optimization (2004), 1(2), 141-165

We present several types of extended formulations for integer programs, based on irreducible integer solutions to Gomory’s group relaxations. We present algorithmic schemes based on an iterative ... [more ▼]

We present several types of extended formulations for integer programs, based on irreducible integer solutions to Gomory’s group relaxations. We present algorithmic schemes based on an iterative reformulation technique using these extended formulations. We give computational results for benchmark problems, which illustrate the primal and dual effect of the reformulation. [less ▲]

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See detailThe Vacuum UV Photoabsorption Spectroscopy of the Three membered Ring Systems C3H6, C2H4O and C2H4S and their open Chain Isomers.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Elektronen Synchrotron Strahlung m.b.H - on CD-ROM (2004)

The vacuum UV photoabsorption spectrum of C3H6, C2H4O and C2H4S have been measured using synchrotron radiation and are reported.

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See detailDevelopments in finite element simulations of continuous casting
Castagne, Sylvie; Pascon, Frédéric ULg; Blès, Guilhem et al

in Journal de Physique IV (2004), 120

Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which ... [more ▼]

Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models. [less ▲]

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See detailContributions aux algorithmes d'intégration temporelle conservant l'énergie en dynamique non-linéaire des structures
Noels, Ludovic ULg

Doctoral thesis (2004)

Les points fondamentaux de mes recherches consistent en une étude mathématique des algorithmes d'intégration temporelle d'une discrétisation de type éléments-finis. Les algorithmes traditionnels d ... [more ▼]

Les points fondamentaux de mes recherches consistent en une étude mathématique des algorithmes d'intégration temporelle d'une discrétisation de type éléments-finis. Les algorithmes traditionnels d'intégration temporelle (Newmark, famille alpha-généralisée, ...) peuvent introduire numériquement de l'énergie dans les systèmes non-linéaires. De nouveaux algorithmes sont dès lors apparus pour permettre d'éviter cette perte de stabilité. Lors de mes études, ces algorithmes ont été étendus, de manière originale, au traitement de la plasticité à l'aide d'un modèle de type hypo-élastique. Ils ont également été étendus au traitement généralisé, dans le cadre tridimensionnel, de l'interaction de contact. Ensuite la mise en oeuvre d'une méthode permettant de combiner, au cours du temps un algorithme implicite stable, avec un algorithme explicite traditionnel a été envisagée. La stabilité du passage d'une méthode explicite vers une méthode implicite a été démontrée par nos soins. Une définition originale de critères automatiques de choix de basculement entre les méthodes a été proposée. Des exemples numériques complexes ont mis en évidences les bonnes performances des algorithmes développés, tant du point de vue de la précision des résultats - confrontés aux résultats expérimentaux si ces derniers existent -, que du point de vue de la réduction des coûts de calcul lorsque la méthode combinée est utilisée. [less ▲]

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See detailAnisotropic elasto-plastic finite element analysis using a stress-strain interpolation method based on a polycrystalline model
Habraken, Anne ULg; Duchene, Laurent ULg

in International Journal of Plasticity (2004), 20(Issue 8-9), 1525-1560

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived ... [more ▼]

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived from crystallographic texture [Int. J. Plasticity 19 (2003) 647; J. Phys. IV France 105 (2003) 39] are an interesting alternative to finite element models, where the macroscopic stress is provided by an averaging of microscopic stresses computed on a set of representative crystallites [Acta Metal 22 (1985) 923; Int. J. Plasticity 5 (1989) 67]. The parameters of the analytical functions modeling the yield locus are identified by comparison with a high number of stress tensors computed, for instance, by the well-known Taylor model [J. Inst. Metal 62 (1938) 307]. This identification method depends on the crystallographic texture and should be applied each time that the plastic strain has induced a significant texture evolution. The stress–strain interpolation method accurately describes the anisotropic material behavior in a narrow stress direction defined by only five stress points. The cost of texture updating is then greatly reduced compared to a full analytical function of the yield locus. After the mathematical description of the stress–strain interpolation method, its validity is demonstrated on two non-radial strain paths. The simulations of a deep drawing experiment allow comparing model predictions and measurements. Accuracy and CPU time of the interpolation stress–strain method are judged against two other models, respectively based on a complete analytical yield locus and on the averaging of crystallite stresses. [less ▲]

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See detailPrediction of distortion during cooling of steel rolled rings using thermal-mechanical-metallurgical finite element model
Pascon, Frédéric ULg; Blès, Guilhem; Bouffioux, Chantal ULg et al

in Steel Grips 2 (2004), Supplement Metal Forming 1-3

This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and ... [more ▼]

This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and dimension measurement devices. The final goal of the project is to develop and set up a system, integrated in the industrial process, capable of predicting the geometrical characteristics of final pieces just after the ring rolling stage and to allow the rolling process to avoid dimensional defects through online adaption. In fact, ring rolling production does not imply only the rolling process, but also the cooling and quench stages of steel rings. During all these phases, the dimensions of the pieces change dramatically. In particular, due to the lack of symmetry in the cooling conditions, ring distortions include contraction and rotation of the ring section. The modeling of the cooling phase requires taking into account a large number of phenomena resulting from the coupling of thermal, mechanical and metallurgical effects. A numerical model has been implemented in the non-linear finite element code LAGAMINE, developed by the University of Liège. Such a model can help to better understand the evolution of the geometry during the cooling phase and also the effects of each physical and microstructural parameter implemented in the model on the ring final shape. Effectively, several parameters can affect the ring distortions and the model should take them into account; in particular, the mechanical and thermal behavior of each phase present in the material (metastable austenite, ferrite, pearlite, bainite and martensite). Phase transformation modeling implies the integration of a wide data base of material properties (thermo-physical and mechanical properties of the phases, TTT and CCT diagrams, enthalpy and strain of phase transformation, strain of transformation plasticity…) but only a few of these data are available in literature. Some of them have been found for the reference material (42CrMo4 steel), but additional laboratory experiments have been performed at the Universities of Padua and Liège in order to characterize thermal, mechanical and plastic behaviour of phases. Finally, this paper presents the model validation on an industrial case (measurements of temperature and dimensions of rings have been provided by the manufacturer). Then, some applications are presented, demonstrating the importance of some factors such as some material properties, the shape of the rings, the type of cooling (and the cooling rate) or the symmetry of the cooling scheme on final ring distortion. [less ▲]

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See detailSuspension de l’exigibilité de créances de l’Etat : l’incidence d’un fédéralisme centrifuge sur le principe d’égalité
Rosoux, Géraldine ULg

in Revue de Jurisprudence de Liège, Mons et Bruxelles (2004)

The article analyzes a mechanism of compensation of State debts, and examines the question of the protection of fundamental rights such as equality in the Belgian federal State.

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See detailDeux chansons wallonnes sur la translation des reliques de sainte Alénie à Liège en 1843
Droixhe, Daniel ULg

in Bulletin de la Société Royale Le Vieux-Liège (2004), XIV(304), 502-508

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See detailBeaux vieux mots de Braine-le-Comte (Belgique)
Droixhe, Daniel ULg

in Linguistique picarde (2004), 44(170), 1-13

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See detailDesign of a versatile device for measuring whole plant gas exchanges in Arabidopsis thaliana
Tocquin, Pierre ULg; Périlleux, Claire ULg

in New Phytologist (2004), 162(1), 223-229

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the ... [more ▼]

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the whole rosette level, as small as possible for fast and accurate measurements, but adaptable to plant size, and suitable for in situ measurements whatever the growing substrate of the plant. This cuvette is in two parts: the basic unit, which contains the sensors and is connected to the infra-red gas analyzer, and the clear chamber, where the rosette is enclosed. We made a set of three interchangeable chambers of different sizes to measure the rate of CO2 assimilation [A] of 26-, 33- and 40-d-old plants. The dependence of A to light irradiance and to intercellular CO2 concentration was recorded as typical response curves, which validate our device. Measurements were not only consistent in saturating conditions, but accurate CO2 exchange measurements in limiting conditions also reflected important physiological features related to plant ageing. [less ▲]

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See detailImpact of low frequency transcranial magnetic stimulation on event-related brain potentials.
Hansenne, Michel ULg; Laloyaux, Olivier ULg; Mardaga, Solange et al

in Biological Psychology (2004), 67(3), 331-41

Contradictory findings exist concerning the inhibitory function of low frequency repetitive transcranial magnetic stimulation (rTMS). Therefore, the study examines the impact of different duration of low ... [more ▼]

Contradictory findings exist concerning the inhibitory function of low frequency repetitive transcranial magnetic stimulation (rTMS). Therefore, the study examines the impact of different duration of low frequency rTMS on ERPs. In 17 subjects, auditory ERPs were measured before and after 1 Hz rTMS delivered over the left prefrontal cortex during 10 min (600 pulses) and 15 min (900 pulses). Results showed that 15 min of 1 Hz rTMS induced a significant increase of P300 latency. There was no effect for early ERP components (N100, P200 and N200). This study confirms and extends that 1 Hz rTMS produces a real inhibitory effect only when the duration of the stimulation is about 15 min. The data suggest that rTMS modifies the speed of cognitive processing rather than the energetical aspect of information processing, and that cortical inhibition induced by the magnetic stimulation affects principally the controlled cognitive processes and not the automatic ones. [less ▲]

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See detailPersonality profile and drug of choice; a multivariate analysis using Cloninger's TCI on heroin addicts, alcoholics, and a random population group.
Le Bon, O.; Basiaux, P.; Streel, E. et al

in Drug and Alcohol Dependence (2004), 73(2), 175-82

As personality may predispose, precipitate or perpetuate substance abuse and/or dependence, and as it is considered to remain stable across the years in a given subject, potential links with the drug of ... [more ▼]

As personality may predispose, precipitate or perpetuate substance abuse and/or dependence, and as it is considered to remain stable across the years in a given subject, potential links with the drug of choice may help screen future patients before drug consumption. The present study compared three groups: 42 patients with heroin dependence (mean age: 31.2; standard deviation (SD): 5.5; 10 females), 37 patients with alcohol dependence (mean age 44.2; SD: 9.1; 9 females) and 83 subjects from a random population sample (mean age: 38.8; SD: 6.9; 20 females). Personality was measured by Cloninger's Temperament and Character Inventory (TCI). Pillai's MANCOVA with age as a covariate and gender as a cofactor was highly significant. Univariate ANOVA analyses using TCI dimensions as dependent variable showed most variables to vary in parallel for the two patient groups in comparison with controls. Post-hoc tests showed heroin patients to score higher in Novelty-Seeking and Self-Directedness than alcohol patients. Sub-dimensions Exploratory Excitability, Fear of the Uncertain, Responsibility, Congruent Second Nature and Transpersonal Identification were also significantly different in the two patient samples. Logistic regression showed Exploratory Excitability to segregate up to 76% of heroin patients from alcohol patients. In conclusion, personality profiles were linked to some preferential choice of drug and personality screening might be tested in preventive strategies. [less ▲]

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