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See detailModelling the Cape Ghir Upwelling Filament
Troupin, Charles ULg

Scientific conference (2008, December 12)

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See detailModelling the cardiovascular system
Shaw, G. M.; Chase, J. G.; Starfinger, C. et al

in Critical Care and Resuscitation : Journal of the Australasian Academy of Critical Care Medicine (2007), 9(3), 264-269

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See detailModelling the Cenozoic evolution of atmospheric CO2
François, Louis ULg; Gaillardet, J.; Godderis, Y.

in Geochimica et Cosmochimica Acta (2002), 66(15A), 243-243

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See detailModelling the climate effect on Black Grouse Population Dynamic in Rhön Biopshere Reserve
Loneux, Michèle ULg; Kolb, Karl-Heinz; Lindsey, James ULg

in Plummer, Ron (Ed.) Black Grouse Endangered Species (2005, December)

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See detailModelling the Climatic Response to Solar Variability
Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution ... [more ▼]

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution models, the solar luminosity has increased steadily by 25-30% over the past 4 × 10[SUP]9[/SUP] years. Periodic variations are also suspected with characteristic timescales of 11 or 22 years, 80-90 years and possibly longer periods. The ultraviolet radiation below 300 nm also exhibits significant changes over the 27-day solar rotation period as well as the 11-year solar cycle. Variations in the solar constant are expected to produce both direct and indirect (feedback) perturbations in the global surface temperature. A hierarchy of zero- to three-dimensional models have been used to study the complex couplings involved by such effects. The response of a zonally averaged model to possible total irradiance changes associated with the Gleissberg cycle is investigated and compared with measurements of the sea-surface temperature made since 1860. Changes in the solar ultraviolet irradiance modulate the amount and distribution of atmospheric ozone, which is predicted to change by several percent in the stratosphere. These perturbations directly affect the middle atmospheric thermal structure, but may also generate indirect effects that could possibly account for some short-term geophysical signatures of solar activity. The cycle-modulated energetic particle interaction with the middle atmosphere is also a possible source of global climatic perturbations. [less ▲]

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See detailModelling the climatic response to solar variability.
Gérard, Jean-Claude ULg

in The Earth's Climate and Variability of the Sun over Recent Millennia: Geophysical, Astronomical and Archaeological Aspects (1990)

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of ... [more ▼]

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of the possible temperature signature of the Gleissberg solar cycle and climatic effects of ultraviolet irradiance variations and intense solar charged particle interaction with the Earth's atmosphere. [less ▲]

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See detailModelling the Climatic Response to Solar Variability: Discussion
Pecker, J*-C; Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

Not Available

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See detailModelling the Coastal Ocean’s Complex Ecohydrodynamics. A case study; the Northern Bering Sea
Nihoul, Jacques ULg; Adam, Paul; Djenidi, Salim ULg et al

in Progress in Belgian Oceanographic Research (1993)

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See detailModelling the competition between two phytoplanktonic species
Elkafazi, Abderahman; Djenidi, Salim ULg; Nihoul, Jacques ULg

in Bulletin de la Société Royale des Sciences de Liège (1996), 65

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See detailModelling the components of binaries in the Hyades: the dependence of the mixing-length parameter on stellar mass
Yıldız, M.; Yakut, K.; Bakış, H. et al

in Monthly Notices of the Royal Astronomical Society (2006), 368(4), 1941-1948

We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to ... [more ▼]

We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to observations so as to give the observed total V and B-V of that system and the observed slope of the main sequence in the corresponding parts. According to our findings, there is a very definite relationship between the mixing-length parameter and the stellar mass. The fitting formula for this relationship can be given as α= 9.19(M/M[SUB]solar[/SUB]- 0.74)[SUP]0.053[/SUP]- 6.65, which is valid for stellar masses greater than 0.77M[SUB]solar[/SUB]. While no strict information is gathered for the chemical composition of the cluster, as a result of degeneracy in the colour-magnitude diagram, by adopting Z= 0.033 and using models for the components of 70 Tau and θ[SUP]2[/SUP] Tau we find the hydrogen abundance to be X= 0.676 and the age to be 670 Myr. If we assume that Z= 0.024, then X= 0.718 and the age is 720 Myr. Our findings concerning the mixing-length parameter are valid for both sets of the solution. For both components of the active binary system V818 Tau, the differences between radii of the models with Z= 0.024 and the observed radii are only about 4 per cent. More generally, the effective temperatures of the models of low-mass stars in the binary systems studied are in good agreement with those determined by spectroscopic methods. [less ▲]

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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Conference (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Poster (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

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See detailModelling the Danube-influenced North-western continental shelf of the Black Sea. I: Hydrodynamical processes simulated by 3-D and box models
Beckers, Jean-Marie ULg; Grégoire, Marilaure ULg; Nihoul, Jacques ULg et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 453-472

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of ... [more ▼]

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of general circulation in the Black Sea are highlighted. Compared with a coarse resolution model, forced with the same climatic monthly averaged atmospheric data, the high resolution model exhibits stronger variability, including frontal structures and coastal upwellings induced by baroclinic instabilities, in particular along the Turkish coast. A comparison of the shelf-open sea exchanges, with particular focus on the cold intermediate waters, shows that both models lead to a replenishment of the CIL in the basin interior by cold waters formed on the shelf. Due to the better representation of frontal structures, the high resolution model is an appropriate candidate for coupling with a biological model. Problems of calibration, interpretation and data availability typically arise from this kind of coupled 3-D model. In order to overcome such difficulties, the results of the 3-D hydrodynamical model are used to guide the development of an integrated 0-D box model capable of achieving the objectives of projects like EROS21, where the effect of changes in the Danube inflows on the shelf ecosystem is investigated. The 0-D model is thus designed to cover this region and is obtained through integration over an appropriate variable volume. The integration procedure shows where the weaknesses of an 0-D approach might lie. Diagnoses in the 3-D model of the integral quantities show the range of uncertainty one can expect in the exchange laws of the 0-D model. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling the Danube-influenced north-western continental shelf of the Black Sea. II: Ecosystem response to changes in nutrient delivery by the Danube River after its damming in 1972
Lancelot, Christiane; Staneva, J.; Van Eeckhout, D. et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 473-499

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has ... [more ▼]

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has been implemented in the north-western Black Sea to assess the response of this coastal ecosystem to eutrophication by the Danube River. The trophic resolution of BIOGEN was chosen to simulate the major ecological changes reported in this coastal area since the 1960s. Particular attention was paid to establishing the link between quantitative and qualitative changes in nutrients, phytoplankton composition and food-web structures. The BIOGEN numerical code structure includes 34 state variables assembled in five interactive modules describing the dynamics of (1) phytoplankton composed of three distinct groups, each with a different trophic fate (diatoms, nanophytoflagellates, non-silicified opportunistic species); (2) meso- and microzooplankton; (3) trophic dead-end gelatinous organisms composed of three distinct groups (the omnivorous Noctiluca and the carnivores Aurelia and the alien Mnemiopsis), and organic matter degradation and associated nutrient regeneration processes by (4) planktonic and (5) benthic bacteria. The capability of the BIOGEN model to simulate the recent ecosystem changes reported for the Black Sea was demonstrated by running the model for the period 1985-1995. The BIOGEN code was implemented in an aggregated and simplified representation of the north-western Black Sea hydrodynamics. The numerical frame consisted of coupling a 0-D BIOGEN box model subjected to the Danube with a 1-D BIOGEN representing the open-sea boundary conditions. Model results clearly showed that the eutrophication-related problems of the north-western Black Sea were not only driven by the quantity of nutrients discharged by the Danube, but that the balance between them was also important. BIOGEN simulations clearly demonstrated that phosphate, rather than silicate, was the limiting nutrient driving the structure of the phytoplankton community and the planktonic food-web. In particular, it showed that a well-balanced N:P:Si nutrient enrichment, such as that observed in 1991, had a positive effect on the linear, diatom-copepod food-chain, while the regenerated-based microbial food-chain remained at its background level. When present, the gelatinous carnivores also benefited from this enrichment throughout their feeding on copepods. A synergetic effect of fishing pressure and cultural eutrophication was further indirectly suggested by modifying the mortality coefficient of copepods. However, BIOGEN scenarios with unbalanced nutrient inputs, such as nitrogen or phosphate deficiency recorded in 1985 and 1995, predicted the dominance of an active microbial food-web in which bacteria and microzooplankton played a key role; the former as nutrient regenerator, the latter as a trophic path to the copepods and hence to the carnivorous. In such conditions, however, a significant biomass reduction of all gelatinous organisms was simulated, in perfect agreement with recent observations. From these model scenarios it is suggested that the observed positive signs of Black Sea ecosystem recovery might well be related to the reduction of nutrient loads in particular phosphate, by the Danube. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling the distribution of key tree species used by lion tamarins in the Brazilian Atlantic forest under a scenario of future climate change
Raghunathan, N.; François, Louis ULg; Huynen, Marie-Claude ULg et al

in Regional Environmental Change (in press)

We used three IPCC climate change scenarios (A1B, A2 and B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of 75 tree species used by two endemic primate species ... [more ▼]

We used three IPCC climate change scenarios (A1B, A2 and B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of 75 tree species used by two endemic primate species from the Brazilian Atlantic Forest (BAF). Habitat conservation is a vital part of strategies to protect endangered species, and this is a new approach to understanding how key plant species needed for survival of golden lion tamarins (Leontopithecus rosalia) and golden-headed lion tamarins (L. chrysomelas) might be affected by climate change and what changes to their distribution are likely. The model accurately predicted the current distribution of BAF vegetation types, for 66 % of the individual tree species with 70 % agreement obtained for presence. In the simulation experiments for the future, 72 out of 75 tree species maintained more than 95 % of their original distribution and all species showed a range expansion. At the biome level, we note a substantial decrease in the sub-tropical forest area. There is some fragmentation of the savannah, which is encroached mostly by tropical seasonal forest. Where the current distribution shows a large sub-tropical forest biome, it has been replaced or encroached by tropical rainforest. The results suggested that the trees may benefit from an increase in temperature, if and only if soil water availability is not altered significantly, as was the case with climate simulations that were used. However, these results must be coupled with other information to maximise usefulness to conservation since BAF is already highly fragmented and subject to high anthropic pressure. © 2014 Springer-Verlag Berlin Heidelberg. [less ▲]

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See detailModelling the disturbed argillite - Strain localization
Pardoen, Benoît ULg; Collin, Frédéric ULg; Charlier, Robert ULg

Scientific conference (2012, February 09)

The excavation process creates a damaged zone around the galleries composing underground structures. The prediction of the extension but especially of the fracturing structure in this zone remains an ... [more ▼]

The excavation process creates a damaged zone around the galleries composing underground structures. The prediction of the extension but especially of the fracturing structure in this zone remains an unresolved issue in the context of underground storage. Disturbed argillite and damage (fracturing) can be numerically modeled by the development of strain localization bands. Within the framework of classical finite elements, the strain localization depends on the mesh while the second gradient method overcomes this difficulty. This method is implemented in the finite element code Lagamine and is used to model biaxial compression tests performed in laboratory. [less ▲]

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See detailModelling The Dynamic Distribution Of Spray Deposits
Lebeau, Frédéric ULg

in Biosystems Engineering (2004), 89(3),

A mathematical model to estimate the spray distribution of phytopharmaceutical deposits under a spray boom is proposed. It focuses on the need to take account of the dynamic effects of the forward ... [more ▼]

A mathematical model to estimate the spray distribution of phytopharmaceutical deposits under a spray boom is proposed. It focuses on the need to take account of the dynamic effects of the forward movement of the boom. These are related both to the horizontal and vertical boom movement and to the influence of aerodynamic factors on the nozzle spray distribution. The distribution of the spray deposits is computed by multiplying the nozzle spray pattern by the time needed to move from one position to the next. Mathematically, this is expressed by a convolution of the trajectory function with the nozzle spray pattern function. The model is validated through a dynamic test bench to reproduce the boom movements observed in the field. The chosen method to measure the distribution of the spray deposits is a chemical dosage of the sprayed potassium chloride (KCl) solution collected in Petri dishes. A pulse-width modulation (PWM) nozzle body fitted on the test bench is used to generate a dynamic distribution of spray deposits from which the dynamic two-dimensional nozzle spray pattern is reconstructed. This dynamic nozzle spray pattern introduced in the model allows a far better estimation of the spray deposit distribution to be made than the one obtained using the static nozzle spray pattern which was computed using filtered back-projection. [less ▲]

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