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See detailModelling groundwater flow and solute transport in karstic systems: from dreams to the reality – how can models help for groundwater vulnerability assessment ?
Dassargues, Alain ULg

in Proceedings of Trans-Karst 2004, International Transdisciplinary Conference on Development and Conservation of Karst Regions (2004, September)

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See detailModelling groundwater pumping and coupled heat transport in a alluvial aquifer: tests using different codes an optimisation
Fossoul, Frédérique ULg; Orban, Philippe ULg; Dassargues, Alain ULg

in Carrera, Jesus (Ed.) XVIII International Conference on Computational Methods in Water Resources, CMWR 2010 (2010, June 24)

Various aquifers are studied in terms of low temperature geothermal potential. The feasibility and impact studies of these systems imply very often a numerical simulation of groundwater flow and heat ... [more ▼]

Various aquifers are studied in terms of low temperature geothermal potential. The feasibility and impact studies of these systems imply very often a numerical simulation of groundwater flow and heat transport. Nowadays, some finite element or finite difference codes are able to deal with such non linear simulations. On a synthetic case study and then on a real case study, a detailed comparative sensitivity analysis is performed using three different codes (MT3DMS, SHEMAT and HYDROGEOSHERE). For low temperatures and relatively small temperature changes, it appears rapidly that the uncertainty affecting values of the main hydrodynamic parameters (i.e. hydraulic conductivity) influences more the results than taking into account any coupling or non linearity. For a case study, the pumping and associated groundwater flow and heat transport are modeled in an alluvial aquifer interacting with a main river in order to assess feasibility of a low energy air cooling /heating system for a large office building. The worst case scenario corresponds to hot summer conditions simultaneously with river maximum temperature and the model leads to an optimization with intermittent pumping in minimum 6 wells. Numerical codes are ready to simulate complex groundwater flow, solute transport and heat transport situations in aquifers, however efforts must be realized to obtain reliable experimental in-situ measured values for the hydro-thermal properties. [less ▲]

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See detailmodelling heat and mass transfer during convective drying of a building material
Kahlerras, Loubna ULg

Conference (2014, August 24)

The purpose of this study is to characterize experimentally the behaviour of a cement mortar during its convective drying. The work presented here focuses on mortars with water-to cement ratios (w/C) of 0 ... [more ▼]

The purpose of this study is to characterize experimentally the behaviour of a cement mortar during its convective drying. The work presented here focuses on mortars with water-to cement ratios (w/C) of 0, 5. The drying tests are realized in a convective dryer designed for the drying of small samples (0 - 8g). Experiences are realized with different conditions of drying air temperature (60, 90 and 130 °C) and velocity (2, 3 and 5 m/s) the results show the influence of temperature and velocity on drying curve. Mathematical models have been used for the description of drying curves. The exponential mathematical model seems the most adequate to describe the drying curves of cement mortars, with correlation coefficients changing with the air temperature and velocity and close to unity. The convective mass and heat transfer coefficients are determined from the experimental data. The results showed that both mass and heat transfer coefficients were affected by the air temperature and velocity. The convective mass transfer coefficient changed from 0.0232m/s at V=2m/s to 0.045m/s at V=5m/s, and from 0.055 m/s at 60°c to 0.023 at 130°c. Heat transfer coefficient changed from 14.767 w/m2°c at V=2m/s to 28.64 w/m2°c at V=5m/s and from 7.71 at 60° c to 14.77 at 130°c The temperature dependency of the two coefficients was expressed using an Arrhenius-type equation and related parameters were deduced [less ▲]

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See detailModelling hte dynamics of oxygen in the Black Sea northwestern shelf
Capet, Arthur ULg; Beckers, Jean-Marie ULg; Joassin, Pascal et al

Conference (2011, May)

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See detailModelling hydro-mechanical coupling using a FE² doublescale approach
van den Eijnden, Abraham Pieter ULg; Collin, Frédéric ULg; Bésuelle, Pierre et al

Scientific conference (2013, September 11)

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See detailModelling Hydrodynamically Dominated Marine Ecosystems
Delhez, Eric ULg

in Journal of Marine Systems (1998), 1-2

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See detailModelling intermediate mass red giants
Moreira, O.; Noels-Grötsch, Arlette ULg; Dupret, Marc-Antoine ULg

in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01)

Not Available

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See detailModelling irregularly sampled profiles of nonnegative dog triglyceride responses under different distributional assumptions
Lambert, Philippe ULg

in Statistics in Medicine (1996), 15

General methodology for modelling series of non-negative data observed at unequally spaced times is developed. The parameterization enables both the importance of the serial association, as well the order ... [more ▼]

General methodology for modelling series of non-negative data observed at unequally spaced times is developed. The parameterization enables both the importance of the serial association, as well the order of this dependence to be expressed. An example is given where the effects of three fibre based diets on dog triglyceride profiles are analysed and compared. Many different types of models based on common distributions such as the normal, exponential, gamma, Weibull and log-normal observations are presented. Comparison of possibly non-nested models fitted on the same data set is made using the Akaike criterion. [less ▲]

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See detailModelling Late Miocene vegetation in Europe: Results of the CARAIB model and comparison with palaeovegetation data
François, Louis ULg; Utescher, T.; Favre, E. et al

in Palaeogeography Palaeoclimatology Palaeoecology (2011), 304(3-4), 359-378

The CARAIB (CARbon Assimilation In the Biosphere) model is used to study the vegetation distribution during the Late Miocene (Tortonian). In this version, the plant classification is specifically adapted ... [more ▼]

The CARAIB (CARbon Assimilation In the Biosphere) model is used to study the vegetation distribution during the Late Miocene (Tortonian). In this version, the plant classification is specifically adapted to best represent Miocene European vegetation. Compared to other plant classifications used in global models, this adapted classification is more refined, since it is specifically developed for European vegetation and it includes various thermophylous tree types, which were present in Europe during the Miocene. The corresponding climatic tolerance parameters are based on the study of Laurent et al. (Journal of Vegetation Science, 15, 739-746, 2004) for the tree types currently present in Europe and on the distribution of analogue species in southeastern Asia and North/Central America for the thermophylous (sub-tropical) trees. The same classification is used to characterize the palaeoflora at the available Late Miocene localities, allowing a model-data comparison at the plant functional type level, rather than at the biome level. The climatic inputs to CARAIB are obtained from the COSMOS atmosphere-ocean general circulation model. The climatic anomalies (Tortonian minus Present) derived from COSMOS are interpolated to a higher spatial resolution before being used in the vegetation model. These anomalies are combined with a modern climatology to produce climatic fields with high spatial resolution (10' x 10'). This procedure has the advantage of making apparent relief features smaller than the grid cells of the climate model and, hence, makes easier the comparison with local vegetation data, although it does not really improve the quality of the Tortonian climate reconstruction. The new version of CARAIB was run over Europe at this higher spatial resolution. It calculates the potential distribution of 13 different classes of trees (including cold/cool/warm-temperate, subtropical and tropical types), together with their cover fractions, net primary productivities and biomasses. The resulting model vegetation distribution reconstructed for the Tortonian is compared to available palaeovegetation and pollen data. Before performing this comparison, the tree taxa present at the various data sites are assigned to one or several model classes, depending on the identification level of the taxa. If several classes are possible for a taxon, only those that can co-exist with the other tree classes identified at the site are retained. This methodology is similar to the co-existence approach used in palaeoclimatic reconstructions based on vegetation data. It narrows the range of tree types present at the various sites, by suppressing in the data the extreme types, such as the cold boreal/temperate and tropical trees. The method allows a comparison with the model simulation on a presence/absence basis. This comparison provides an overall agreement of 53% between the model and the data, when all sites and tree types are considered. The agreement is high (>85%) for needle-leaved summergreen boreal/temperate cold trees (Larix sp.) and for tropical trees, intermediate (>40%) for other boreal/temperate cold trees and for needle-leaved evergreen temperate cool trees, broadleaved summergreen temperate cool trees and broadleaved evergreen warm-temperate trees, and poor (<40%) for most temperate perhumid warm trees. In many cases, the model is shown to be better at predicting the absence than the presence, as observed for tropical trees. The modelled distributions of cold boreal/temperate trees tend to extend too much towards the south compared to the data. B contrast, model sub-tropical trees (temperate perhumid warm and needle-leaf summergreen temperate warm trees) appear to be restricted to some limited areas in southern Europe, while they are present in the data from central Europe up to at least 50 degrees N. Consequently, modelled Late Miocene climate appears to remain too cold to produce assemblages of trees consistent with the data. The predicted modelled trends from the past to the present are in the right direction, but the amplitude remains too small. For the simulations to be in a better agreement with the data, higher CO2 levels may be necessary in the climate simulations, or possibly other oceanic boundary conditions may be required, such as different bathymetry in the Panama seaway. (C) 2011 Elsevier B.V. All rights reserved. [less ▲]

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See detailModelling Lymphatic and blood capillary patterning
Bruyere, Françoise; Maillard, Catherine ULg; Erpicum, Charlotte ULg et al

in Davies, Jamie (Ed.) Replacing Animal Models, a practical guide to creating and using culture-based biomimetic alternatives (2012)

Angiogenesis and lymphangiogenesis, the formation of new blood or lymphatic vessels from preexisting ones, are important biological processes associated with diverse physiological processes, tissue repair ... [more ▼]

Angiogenesis and lymphangiogenesis, the formation of new blood or lymphatic vessels from preexisting ones, are important biological processes associated with diverse physiological processes, tissue repair and pathologies, such as cancer. Much progress has been made in recent years in identifying molecules specifically expressed on blood and lymphatic vessels and in the setting up of models of angiogenesis and lymphangiogenesis. In this review, we describe the most common in vitro models of (lymph)angiogenesis that have proven suitable for investigating angiogenic and lymphatic biology, and offer alternatives to animal experimentation. Their rationales, limitations and applications in biomedical research are discussed. A special emphasis will be given on ring assays that provide excellent recapitulation of various steps of (lymph)angiogenesis. The aortic ring assay has become the most widely used methods to study in vitro angiogenesis, and the recently set up lymphatic ring assay provides the opportunity to extend the in vitro studies to lymphangiogenesis. [less ▲]

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See detailModelling macroalgae productivity in an estuary. a biorremediation to nutrient discharges in the ecosystems
Alvera Azcarate, Aïda ULg; Ferreira, J. G.; Nunes, J. P.

Conference (2002, April)

Enhanced nutrient load to estuaries and coastal waters due to anthropogenic activities is damaging aquatic ecosystems, resulting in water pollution and eutrophication prob- lems. It is important to ... [more ▼]

Enhanced nutrient load to estuaries and coastal waters due to anthropogenic activities is damaging aquatic ecosystems, resulting in water pollution and eutrophication prob- lems. It is important to quantify the production of photosynthetic organisms, as they play an important role in controlling nitrogen removal and nitrogen fluxes between the sediments and the water column. In turbid estuaries, such as those on the NE Atlantic coast of Europe, benthic primary producers such as macroalgae may play an important part in carbon fixation and nutrient removal, since pelagic production is often strongly light-limited. Estuarine seaweeds are primarily located in intertidal areas, which are characterised by shallow waters and strong tidal currents. Due to high concentrations of suspended particulate matter in the water column, light is rapidly attenuated, limiting macroal- gae production during part of the tidal cycle. An accurate representation of sediment dynamics is essential for the determination of the light energy available for the algae, which is a key factor in reliable primary production estimates. In tidal flats, the sedi- ment dynamics is made more complex by the formation of tidal pools during low tide, where water quickly becomes clear, allowing more light to penetrate through the water column. In the present work a model is developed to calculate macroalgae production in the intertidal areas of estuaries, considering the factors mentioned above. The model is tested for the Tagus estuary (Portugal), and a Gross Primary Production of 3300 g m-2 y-1 was obtained. That results in a total nitrogen removal of 440 gN m-2 y-1. The results show that the macroalgae community plays an impor- tant role in the nitrogen cycle in estuaries and nutrient export to the open sea, acting as a biorremediation for the increased nutrient loading problem. [less ▲]

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See detailModelling micropore formation during directional solidification
Daoxin, Ji; Lecomte-Beckers, Jacqueline ULg; Habraken, Louis

in metallurgical report CRM (1982), 59

In this work we have developed two criteria which can characterize the susceptibility to microporosities formation of alloys. These defects are influential in determining mechanical properties of ... [more ▼]

In this work we have developed two criteria which can characterize the susceptibility to microporosities formation of alloys. These defects are influential in determining mechanical properties of materials. The first criterion is used when the fraction eutectic is important : then the porosity formation is essentially caused by dissolved gases of formed during chemical reactions. The second is employed when the alloy possesses low fraction eutectic. In that case, because of the pressure drop, the liquid is unable to feed through interdendritic spaces to accomodate solidification shrinkage. The pressure drop is composed of two terms which influence in contrary direction : the first is due to solidification shrinkage and the second to gravity. This term is the most important except for low fraction eutectic. The fraction liquid (or the fraction eutectic) is an important factor. It depends on the alloy composition and on solidification conditions. In fact, we have showed that, depending on initial alloy concentration, the solidification conditions have opposite effects on the fraction liquid : if Co>KCe, the fraction liquid decreases if the ratio G/R decreases and if Co<KCe it increases if the ratio G/R decreases. [less ▲]

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See detailModelling migration from high-density polyethylene containers into concentrated solutions used as food flavourings
Fauconnier, Marie-Laure ULg; Panhaleux, V.; Vanzeveren, E. et al

in Food Additives & Contaminants (2001), 18(11), 1040-1045

Migration from high-density polyethylene into different liquids (hexane, ethanol, lemon terpenes and their emulsions) was modelled using the response surfaces method. Polynomial equations (z = A + Bx + Cy ... [more ▼]

Migration from high-density polyethylene into different liquids (hexane, ethanol, lemon terpenes and their emulsions) was modelled using the response surfaces method. Polynomial equations (z = A + Bx + Cy + Dx(2) + Ey(2) + Fxy) were established and parameters determined for each compound. Correlation coefficients were generally > 90%. Analysis indicated that 2,4-bis(1,1-dimethylethyl) phenol, probably due to the degradation of the antioxidant additive tris(2,4- bis(1,1-dimethylethyl) phenyl) phosphite, migrated into each liquid tested, whatever the temperature. Oligomers (10-30 carbons) terminated by a vinyl group were also detected. [less ▲]

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See detailModelling Mixed Flows in Civil and Environmental Engineering: a 1D Three-phase Approach
Kerger, François ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Proc of 7th International Conference on Mutiphase Flow (2010)

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See detailModelling nitrogen fluxes in a semi-enclosed environment (the Black Sea): transport versus biogeochemical processes and quantification of the exchanges at the shelf break
Grégoire, Marilaure ULg; Beckers, Jean-Marie ULg; Kostianoy, A. et al

in Commission internationale pour l'exportation Scientifique de la Mer Méditerranée Vol. 36 (2001)

A three-dimensional coupled biogeochemical-hydrodynamical model has been developed to get a better understanding of the biogeochemical functioning of the Black Sea. The in?uence on the ecodynamics of ... [more ▼]

A three-dimensional coupled biogeochemical-hydrodynamical model has been developed to get a better understanding of the biogeochemical functioning of the Black Sea. The in?uence on the ecodynamics of hydrodynamical and biogeochemical processes is quantified. Nitrogen inputs from the rivers, from the sediments and from the deep sea are estimated and compared in terms of potential fertilization. The exchanges between the north-western shelf and the deep sea are quantified. The results illustrate a highly complex spatial variability of the phytoplankton annual cycle and thus, stress the importance of using a 3D model to capture the essential physical-biological interactions that explain the data. [less ▲]

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See detailModelling numerical thinnings in forest management
Rondeux, Jacques ULg

in Rondeux, Jacques (Ed.) Modelling numerical thinnings in forest managment (1985, September)

This paper describes the construction of a simulation model for intensive management of even-aged stands of spruce (Picea abies Karst.) in Belgium. A computer program produces a thinning schedule or a ... [more ▼]

This paper describes the construction of a simulation model for intensive management of even-aged stands of spruce (Picea abies Karst.) in Belgium. A computer program produces a thinning schedule or a guide to reduction in number of trees. Knowing the total production of which a site is capable, the forester may calcultate how many trees growing at a chosen rate are required to use the capacity of this site. The model starts from stand constraints issued from inventories (age, number of stems, top height, mean diameter) and silvicultural constraints (annual diameter increment, rotation age, thinning cycle and thinning type). [less ▲]

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See detailModelling ocean acidification in marginal seas: the North Western European shelf case study
Artioli, Y; Blackford, JC; Butenschön, M et al

Conference (2013)

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See detailModelling of hollow cylinder tests on Boom Clay: softening, anisotropy and strain localization
François, Bertrand; Labiouse, Vincent; You, S. et al

Conference (2012)

Detailed reference viewed: 14 (2 ULg)