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See detailLes sols wallons sous la loupe
Legrain, Xavier ULiege; Demarcin, Pierre ULiege; Bock, Laurent ULiege et al

Article for general public (2010)

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See detailSolutions TP4 Rugosité - Frettage
Trif, David Ioan ULiege

Learning material (2010)

Le présent chapitre offre les solutions pour les exercices proposés dans le chapitre Rugosité - Frettage.

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See detailL’apprentissage au secours de la réduction de dimension pour des problèmes d’optimisation
Ben Abbes, Ala; Rachelson, Emmanuel ULiege; Diemer, Sébastien

in Actes de la Conférence Francophone d'Apprentissage (2010, May 19)

Pour assurer la stabilité du réseau électrique, la production doit être ajustée en quasi temps réel à la consommation. Cet ajustement ne peut porter que sur un nombre limité de centrales et doit être ... [more ▼]

Pour assurer la stabilité du réseau électrique, la production doit être ajustée en quasi temps réel à la consommation. Cet ajustement ne peut porter que sur un nombre limité de centrales et doit être effectué dans des délais réduits. La combinatoire du problème rend la recherche d’un optimum économique par des méthodes d’optimisation classiques très difficile. Ce travail cherche à montrer l’intérêt d’utiliser des algorithmes d’apprentissage supervisé performants comme le Boosting, pour sélectionner les centrales à redéclarer. Cette sélection préalable permet ensuite de réduire considérablement le temps de l’optimisation des programmes de production tout en garantissant l’optimalité économique. [less ▲]

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See detailRiver modelling and flood mitigation in a Belgian catchment
Khuat Duy, Bruno; Archambeau, Pierre ULiege; Dewals, Benjamin ULiege et al

in Proceedings of ICE : Water Management (2010), 163(8), 417-423

This paper describes the steps followed to propose solutions to recurring flooding problems in a Belgian catchment. Firstly, the hydraulic capacity (maximum discharge before bank overflow) of the cross ... [more ▼]

This paper describes the steps followed to propose solutions to recurring flooding problems in a Belgian catchment. Firstly, the hydraulic capacity (maximum discharge before bank overflow) of the cross sections was computed all along the river by an iterative 1D steady-state approach. In order to carry out these simulations, cross sections from on-site surveys of the river were integrated into the model, as well as hydraulic structures such as culverts, footbridges, and pipes. Secondly, the flooding problem was analysed with a time-dependant approach consisting of simulating floods following extreme rainfall events. The hydrological aspect was studied in a spatially distributed way using a multi-layer hydrological model. The available data on the basin such as the digital elevation model (DEM), the landuse, and the pedology were exploited to identify the basic modelling parameters. The hydrological contribution was routed by a 1D network resulting from the merging of the DEM-based and the cross section-based river networks. According to the results of the aforementioned steps, various local and catchment-wide solutions against flooding were proposed and analyzed. The comparison of simulated situations before and after these improvements allowed checking the effectiveness of the proposed solutions. [less ▲]

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See detailProjet OPALHA : Prévision de la propagation sonore en milieu urbain à l'aide d'un modèle de diffusion
Billon, Alexis ULiege

Scientific conference (2010, May 19)

Dans cette présentation, des développements du modèle de diffusion pour l'acoustique urbaine sont présentés. Ces développements prennent en compte : la présence du sol, l'absorption aux façades et l ... [more ▼]

Dans cette présentation, des développements du modèle de diffusion pour l'acoustique urbaine sont présentés. Ces développements prennent en compte : la présence du sol, l'absorption aux façades et l'atténuation atmosphériques. Le modèle obtenu est ensuite validé numériquement et expérimentalement. [less ▲]

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See detailDe la prévention chronologique à la prévention relationnelle; la prévention quaternaire comme tâche du médecin de famille.
Jamoulle, Marc ULiege

Poster (2010, May 19)

La prévention clinique est traditionnellement exprimée comme une vue du médecin sur une tâche à réaliser avant la survenue d’un évènement. Initiée par Leavell et Clark en 1958 elle est complétée en 1988 ... [more ▼]

La prévention clinique est traditionnellement exprimée comme une vue du médecin sur une tâche à réaliser avant la survenue d’un évènement. Initiée par Leavell et Clark en 1958 elle est complétée en 1988 par J-A Bury qui dénomme prévention quaternaire les soins palliatifs.Le paradigme change, le patient devient central aux soins, la prévention clinique est perçue au travers de la relation entre le médecin et le patient. Le croisement de la science du médecin et de la conscience du patient permet de répartir la prévention en quatre champs. Elle est traversée en oblique par la ligne du temps. Cette proposition (Jamoulle, 1986) a été avalisée par la Wonca et l’UEMO et permet de cadrer quatre concepts de prévention clinique. [less ▲]

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See detailPrésentation de Pierre Gagnaire, grand chef cuisinier
Blecker, Christophe ULiege

Scientific conference (2010, May 18)

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See detailThe partial proportional odds model in the analysis of
Donneau, Anne-Françoise ULiege

Conference (2010, May 18)

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See detailSolutions TP11 - Roulements
Trif, David Ioan ULiege

Learning material (2010)

Dans le présent chapitre, on propose les solutions pour les exercices sur les roulements.

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See detailTP11 - Roulements
Trif, David Ioan ULiege

Learning material (2010)

On propose quelques exercices sur les roulements.

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See detailThe occurrence of multicolored ladybird, Harmonia axyridis Pallas, a biological control agent in agroecosystems in Wallonia
Vandereycken, Axel ULiege; Durieux, Delphine ULiege; Haubruge, Eric ULiege et al

Conference (2010, May 18)

The Asian ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was imported in 1997 in Belgium to control aphid populations in greenhouses. It took only few years to the insect to get adapted ... [more ▼]

The Asian ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was imported in 1997 in Belgium to control aphid populations in greenhouses. It took only few years to the insect to get adapted to temperate climate conditions and to spread out all over Europe. Now, H. axyridis is one of the coccinellid with the biggest size in Belgium, causing damages to the ecosystems through e.g. intraguild predation (IGP). We are still lacking information about the consequences of the introduction of this superpredator in our agro-ecosystems. This work focuses on the potential impacts of H. axyridis on the entomofauna associated with several crops (potatos, corn, wheat, broad bean). We evaluated in 2009 the occurrence as well as the interactions between aphids and their natural enemies (hoverflies, coccinellids and lacewings) in several agro-ecosystem sites in northern Wallonia. After one year of field observations, were found thirteen coccinellid species, most of the catched individuals being H. axyridis with 64% of the coccinellids, Propylea 14-punctata, 15%, or Coccinella 7-punctata, 14%. This invasive ladybird dominates the group of coccinellids generally in all crops in north Wallonia. The results with the sticky traps show that the maximum occurrence of H. axyridis in crops is observed in chicory, sugar beet and potatoes. The relationship aphid-ladybird in wheat for example, brings out that increase of density of Asian ladybird in mid-July follow the increase of aphids (Sitobion avenae, Sitobion fragariae, Metopolophium dirhodum, Aphis fabae) in the end of June. We also observe that, in most agro-ecosystems, hoverflies and lacewings are the dominant aphid natural enemies. In all crops investigate, the multicolored ladybird occurs with 5% of the aphidophagous after the Chrysopidae, 12% and the Syrphidae, 76%. In 2009, the agro-ecosystems with the most aphidophagous species are carrot and broad bean and these habitats are dominated by hoverflies. [less ▲]

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See detailMéfions-nous du "Tueur silencieux"
Krzesinski, Jean-Marie ULiege

Speech/Talk (2010)

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See detailAccompagner une réforme vers des programmes visant le développement de compétences – difficultés et leviers –
Poumay, Marianne ULiege; Tardif, Jacques

Conference (2010, May 17)

En 2007, au sein de l’Université de Liège, l’IFRES a lancé un programme interne de financement et d’accompagnement de projets facultaires. Dans les projets sélectionnés, les enseignants s’engageaient à ... [more ▼]

En 2007, au sein de l’Université de Liège, l’IFRES a lancé un programme interne de financement et d’accompagnement de projets facultaires. Dans les projets sélectionnés, les enseignants s’engageaient à progresser concrètement dans l’opérationnalisation de formations orientées vers le développement de compétences chez leurs étudiants. A travers ce programme « compétences », l’objectif de l’IFRES était d’amorcer des réformes qui visent l’amélioration de l’apprentissage des étudiants. Suite à la nécessaire description de l’initiative et de quelques résultats concrets, le présent article mentionne brièvement les difficultés d’ordre institutionnel ou organisationnel et s’attarde surtout à déterminer et illustrer des problèmes conceptuels qui se posent dans ce type de réforme. Il mentionne certains freins et facteurs facilitateurs, soulignant entre autres l’intérêt d’un accompagnement semi-collectif par un consultant externe (en l’occurrence Jacques Tardif) et d’une large communication sur les avancées des projets en cours. [less ▲]

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See detailDirect CO2 advection measurements and the night flux problem
Aubinet, Marc ULiege; Feigenwinter, Christian

in Agricultural and Forest Meteorology (2010), 150(5), 651-654

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See detailDirect advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests
Aubinet, Marc ULiege; Feigenwinter, Christian; Heinesch, Bernard ULiege et al

in Agricultural and Forest Meteorology (2010), 150(5), 655-664

The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time ... [more ▼]

The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time conditions, in an attempt to improve NEE estimates. Four towers were arranged in a square around a main tower, with the sides of the square about 100 m long. Equipped with 16 sonic anemometers and [CO2] sampling points, the towers were installed to measure vertical and horizontal advection of [CO2]. Vertical turbulent fluxes were measured by an eddy covariance system at the top of the main tower. The results showed that horizontal advection varied greatly from site to site and from one wind sector to another, the highest values being reached when there were large friction velocities and fairly unstable conditions. There was less variation in vertical advection, the highest values being reached when there were low friction velocities and stable conditions. The night-time NEE estimates deduced from the mass balance were found to be incompatible with biologically driven fluxes because (i) they varied strongly from one wind sector to another and this variation could not be explained in terms of a response of the biologic flux to climate, (ii) their order of magnitude was not realistic and (iii) they still showed a trend vs. friction velocity. From a critical analysis of the measurement and data treatment we concluded that the causes of the problem are related to the representativeness of the measurement (control volume size, sampling resolution) or the hypotheses underlying the derivation of the [CO2] mass balance (ignoring the horizontal turbulent flux divergence). This suggests that the improvement of eddy flux measurements by developing an advection completed [CO2] mass balance at night would be practically difficult. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailPlot-scale vertical and horizontal transport of CO2 modified by a persistent slope wind system in and above an alpine forest
Feigenwinter, Christian; Montagnani, Leonardo; Aubinet, Marc ULiege

in Agricultural and Forest Meteorology (2010), 150(5), 665-673

Data from the flux tower site Renon/Ritten, Italy, located at 1735 m. a.s.l. on a south exposed steep (11 degrees) forested alpine slope, is analyzed. In spite of the complex terrain, a persistent slope ... [more ▼]

Data from the flux tower site Renon/Ritten, Italy, located at 1735 m. a.s.l. on a south exposed steep (11 degrees) forested alpine slope, is analyzed. In spite of the complex terrain, a persistent slope wind system prevailed at the site during most of the ADVEX campaign from April to September 2005. We describe in detail how CO2 is transported parallel to the slope and how this transport affects net ecosystem exchange (NEE) in the diurnal course. The local slope wind system may be strongly modified by two different large scale synoptic situations. The "Tramontana", a persistent strong wind from the north, amplified the drainage flow during nighttime and suppressed the upslope flow above the forest canopy during daytime. Vice versa, we observed periods with continuing flow from the south, which supported the local daytime upslope flow and partly suppressed the nighttime downslope flow. This led to periods of several hours with opposite flow directions in and above the canopy. Depending on the prevailing situation, the trunk space is coupled and/or decoupled with/from the roughness sublayer above the forest canopy. In particular, vertical and horizontal mixing of CO2 was strongly dependent on the dominating wind field with essential impact on the horizontal advective flux of CO2. The most common "Local" situation, dominated by the slope wind system, showed positive horizontal and vertical advection (with typical values around 7 and 3 mu mol m(-2) s(-1), respectively) together with downslope winds at night and slightly negative horizontal advection (typical values around 2 mu mol m(-2) s(-1)) together with upslope winds during the day. This pattern was amplified at night when the wind was consistently (day and night) blowing downslope (the "Tramontana" situation) and, vice versa, attenuated during the night, when the wind was blowing permanently upslope (the "Southerlies" situation). Taking into account these advective fluxes would significantly reduce the reported annual CO2 uptake of this forest. Related effects are expected to occur at flux tower sites with similar topography and vegetation. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailSpatiotemporal evolution of CO2 concentration, temperature, and wind field during stable nights at the Norunda forest site
Feigenwinter, Christian; Molder, Meelis; Lindroth, Anders et al

in Agricultural and Forest Meteorology (2010), 150(5), 692-701

Unusually high CO2 concentrations were frequently observed during stable nights in late summer 2006 at the CarboEurope-Integrated Project (CEIP) forest site in Norunda, Sweden. Mean CO2 concentrations in ... [more ▼]

Unusually high CO2 concentrations were frequently observed during stable nights in late summer 2006 at the CarboEurope-Integrated Project (CEIP) forest site in Norunda, Sweden. Mean CO2 concentrations in the layer below the height of the eddy-covariance measurement system at 30 m reached up to 500 mu mol mol(-1) and large vertical and horizontal gradients occurred, leading to very large advective fluxes with a high variability in size and direction. CO2 accumulation was found to build up in the second part of the night, when the stratification in the canopy sub-layer turned from stable to neutral. Largest vertical gradients of temperature and CO2 were shifted from close to the ground early in the night to the crown space of the forest late at night, decoupling the canopy sub-layer from the surface roughness layer. At the top of the canopy at 25 m CO2 concentrations up to 480 mu mol mol(-1) were observed at all four tower locations of the 3D cube setup and concentrations were still high (>400 mu mol mol(-1)) at the 100 m level of the Central tower. The vertical profiles of horizontal advective fluxes during the nights under investigation were similar and showed largest negative horizontal advection (equivalent to an additional CO2-sink) to occur in the crown space of the forest, and not, as usually expected, close to the ground. The magnitude of these fluxes was sometimes larger than 50 mu mol m(-2) s(-1)and they were caused by the large horizontal CO2 concentration gradients with maximum values of up to 1 mu mol mol(-1) m(-1). As a result of these high within canopy CO2 concentrations, the vertical advection also became large with frequent changes of direction according to the sign of the mean vertical wind component, which showed very small values scattering around zero. Inaccuracy of the sonic anemometer at such low wind velocities is the reason for uncertainty in vertical advection, whereas for horizontal advection, instrument errors were small compared to the fluxes. The advective fluxes during these nights were unusually high and it is not clear what they represent in relation to the biotic fluxes. Advection is most likely a scale overlapping process. With a control volume of about 100 m x 100 m x 30 m and the applied spatial resolution of the sensors, we obviously miss relevant information from processes in the mesoscale as well as in the turbulent scale. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

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