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See detailModelling the risk of ecosystem disruption in Europe with a dynamic vegetation model
Dury, Marie ULg

Conference (2012, June)

With unprecedented speed and extent, the projected climate change might lead to a disruption of terrestrial plants functioning in many regions. In the framework of the EcoChange project, the process-based ... [more ▼]

With unprecedented speed and extent, the projected climate change might lead to a disruption of terrestrial plants functioning in many regions. In the framework of the EcoChange project, the process-based dynamic vegetation model, CARAIB DVM (Dury et al., 2011, iForest 4, 82-99) was used to assess the transient vegetation response to climate change and identify threatened regions across Europe. The vegetation model was driven over 1951-2100 by the outputs of 4 climate models under different SRES scenarios: the ARPEGE/Climate model and 3 regional climate models from the European Union project ENSEMBLES. European vegetation was studied at the Bioclimatic Affinity groups scale as well as the species scale. The ability of the climate models to reproduce the present-day climate was evaluated comparing the interannual climate variability simulated by the models with the observed climate variability over 1961-1990 (CRU TS 3.0 dataset). Under the combined effects of projected changes particularly in temperature and precipitations, CARAIB simulates important reductions in the annual soil water content which have large impacts notably on net primary productivity and fire risk in the Mediterranean region but also in other parts of Europe. With this background, the species and biome distributions are projected to be strongly modified. Finally a quantitative index combining some CARAIB outputs evaluates the risk of ecosystem disruption in Europe. [less ▲]

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See detailModelling the risk of ecosystem disruption in Europe with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Warnant, Pierre et al

Conference (2012, April)

What will be the European ecosystem responses to future climate? With unprecedented speed and extent, the projected climate change might lead to a disruption of terrestrial plants functioning in many ... [more ▼]

What will be the European ecosystem responses to future climate? With unprecedented speed and extent, the projected climate change might lead to a disruption of terrestrial plants functioning in many regions. In the framework of the EcoChange project, transient projections over the 1901-2100 period have been performed with a process-based dynamic vegetation model, CARAIB DVM (Dury et al., 2011, iForest 4: 82, 99). The vegetation model was driven by the outputs of four climate models under the SRES A1B scenario: the ARPEGE/Climate model and three regional climate models (KNMI-RACMO2 , DMI-HIRHAM5 and HC-HadRM3Q0 RCMs) from the European Union project ENSEMBLES. DVMs are appropriate tools to apprehend potential climate change impacts on ecosystems and identify threatened regions over Europe. CARAIB outputs (soil moisture, runoff, net primary productivity, fire, etc.) were used to characterize the ecosystem evolution. To assess consequences on biodiversity, the evolution of 100 natural common European species (47 herbs, 12 shrubs and 41 trees) has been studied year-to-year over the 1901-2100 period. Under the combined effects of projected changes particularly in temperature and precipitations, CARAIB simulates important reductions in the annual soil water content. The species productivities vary strongly from year to year reaching during the driest years values much lower than present-day average productivity. According to CARAIB, a lot of species might go beyond their water tolerance very frequently, particularly after 2050, due to more intense summer droughts. In the northern part of Europe and in the Alps, with reduced temperature variability and positive soil water anomalies, NPP variability tends to decrease. Regions with more severe droughts might also be affected by an increase of the frequency and intensity of wildfires. With this background, the species distributions might be strongly modified. 15% of tree species and 30% of herb and shrub species (respectively 30% and 60% if the CO2 fertilization effect on species is not taken into account) might experience a loss of 30% or more of their current distribution. Proportions of new species appearance at the end of the century were also studied. Southern Europe might suffer important species extinction while the more suitable climate conditions in northern Europe might lead to a gain in species diversity. [less ▲]

Detailed reference viewed: 67 (17 ULg)
See detailModelling the seasonal cycle of the biological productivity in the Ligurian Sea by means of a 1D interdisciplinary model
Raick, C.; Soetaert, K.; Grégoire, Marilaure ULg

in VLIZ Young Scientists' Day, Brugge, Belgium 5 March 2004: book of abstracts. VLIZ Special Publication, 17 (2004, March 05)

A one-dimensional coupled physical-biogeochemical model has been built to study the pelagic food web of the Ligurian Sea (NW Mediterranean Sea). The physical model is the turbulent closure model (version ... [more ▼]

A one-dimensional coupled physical-biogeochemical model has been built to study the pelagic food web of the Ligurian Sea (NW Mediterranean Sea). The physical model is the turbulent closure model (version 1D) developed at the GeoHydrodynamics and Environmental Laboratory (GHER) of the University of Liège. The ecosystem model contains nineteen state variables describing the carbon and nitrogen cycles of the pelagic food web. Phytoplankton and zooplankton are both divided in three size-based compartments and the model includes an explicit representation of the microbial loop including bacteria, dissolved organic matter, nano-, and micro- zooplankton. The internal carbon/nitrogen ratio is assumed variable for phytoplankton and detritus, and constant for zooplankton and bacteria. Silicate is considered as a potential limiting nutrient of phytoplankton growth. The aggregation model described in Kriest and Evans (2000) is used to evaluate the sinking rate of particulate detritus. The model is forced at the air-sea interface by meteorological data coming from METEO France. The DYFAMED time series data obtained during the year 2000 are used to calibrate and validate the biological model. The comparison of model results within in-situ DYFAMED data shows that although some processes are not represented by the model, such as horizontal and vertical advections, model results are in good agreement with observations and differences observed can be explained with environmental conditions. [less ▲]

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See detailModelling the sediment transport in a Belgian coastal area
Djenidi, Salim ULg

in Vreughdenil, C. B. (Ed.) Mathematical modelling of sediment transport and morphology (Euromech 177 Colloquium) (1984)

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See detailModelling the short-term and long-term aggregate response of multiple loads fed through a sub-transmission network
Van Cutsem, Thierry ULg; Renoy, Quentin; Lefebvre, Daniel

(2006, November)

This paper addresses the problem of representing the aggregate response to voltage changes of a set of loads fed through distribution transformers connected by a subtransmission network. A simple, while ... [more ▼]

This paper addresses the problem of representing the aggregate response to voltage changes of a set of loads fed through distribution transformers connected by a subtransmission network. A simple, while accurate equivalent is proposed. The latter involves standard network components and includes a single internal bus. This equivalent matches both the short-term and the long-term response of the original system, the long-term dynamics coming from the load tap changers that control the distribution voltages. A procedure to identify its parameters from step responses of the unreduced system is detailed. The method is illustrated and validated on a large subtransmission-distribution system of Hydro-Québec. [less ▲]

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See detailModelling the sound transmission through separation walls using a diffusion model
Billon, Alexis ULg; Foy, Cédric; Valeau, Vincent et al

Conference (2007, September)

The diffusion model has been used successfully to evaluate the acoustic behaviour of a system of coupled rooms connected through a coupling aperture. In this paper, an extension of this model is proposed ... [more ▼]

The diffusion model has been used successfully to evaluate the acoustic behaviour of a system of coupled rooms connected through a coupling aperture. In this paper, an extension of this model is proposed to deal with the propagation of sound energy through a partition wall. The diffusion model can be considered as an extension of the statistical theory to none diffuse sound fields. Numerical comparisons with the statistical theory are then carried out. The following parameters are varied: its transmission loss of the separation wall, its surface, the coupled room’s absorption coefficient and the coupled room’s volume. The agreement between the statistical theory and the diffusion model is very good. [less ▲]

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See detailModelling the spatial distribution of endemic Caesalpinioideae in Central Africa, a contribution to the evaluation of actual protected areas in the region
Ndayishimiye, J.; Greve, M.; Stoffelen, P. et al

in International Journal of Biodiversity and Conservation (2012), 4

Detailed reference viewed: 58 (17 ULg)
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See detailModelling the spray drift by a modified Gaussian tilting plume model.
Stainier, Charles; Robaye, Vincent ULg; Schiffers, Bruno ULg et al

in Aspects of Applied Biology (2006), 77(2), 281-287

The increased concern about environmental effect of pesticides use has resulted in abundant research on spray drift. Spray drift modelling has been developed to get a better understanding of the ... [more ▼]

The increased concern about environmental effect of pesticides use has resulted in abundant research on spray drift. Spray drift modelling has been developed to get a better understanding of the parameters involved and better estimation of the off-target spray deposit. Two groups of models have received extensive a.ttention: Random-walk and computational fluid dynamics (CFD) models have been used to predict the effect of: nozzle height, spray pressure, wind speed,... and were v.alidated with wind tunnels trials. Statistical models based on field trials results have been developed to estimate off-target spray deposit for different sprayers in various environmental conditions. A third group, Gaussian dispersion models, have received early attention in spray drift modelling but are not so popular, despite their international success in environmental pollution modelling. The adaptation of such a model to ground spraying is proposed. The nozzle droplet size distribution measured with a Malvern laser particle analyser is used to divide the nozzle output into several size classes. The spray deposit (or footprint) of each diameter class is computed. The summation of these footprints results in the global drift of the nozzle. The methodology is applied to derive the drift of a.flat fan nozzle located in a wind tunnel and the potential of this approach is discussed. [less ▲]

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See detailModelling the thermal efficiency of condensing boilers working in steady-state conditions
Makaire, Danielle ULg; Ngendakumana, Philippe ULg

Scientific conference (2010, May)

The structure of the model is similar to the model of a conventional boiler model with a main counterflow gas-water heat exchanger (HX1), at which a condensing heat exchanger is added (HX2). The case ... [more ▼]

The structure of the model is similar to the model of a conventional boiler model with a main counterflow gas-water heat exchanger (HX1), at which a condensing heat exchanger is added (HX2). The case losses to the ambient is neglected. Prior to the second heat exchanger (HX2), the exhaust gas are converted to equivalent wet air as the wet heat exchanger is simulated by a cooling coil used in air treatment. The model has been validated experimentally on gas- and oil-fired boilers. Calculated thermal efficiencies agree very well with experimental results. [less ▲]

Detailed reference viewed: 150 (10 ULg)
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See detailModelling the time-dependent 3-D circulation around a submarine canyon during stormy weather conditions
Skliris, Nikolaos; Djenidi, Salim ULg; Lacroix, Geneviève

Conference (2002)

Detailed reference viewed: 9 (4 ULg)
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See detailModelling the top-height growth and site index of Norway spruce in Southern Belgium
Perin, Jérôme ULg; Hebert, Jacques ULg; Brostaux, Yves ULg et al

in Forest Ecology & Management (2013), 298

Top-height growth in even-aged stands of Norway spruce (Piceaabies (L.) Karst.) from Southern Belgium was modelled using functions which provide an algebraic solution for site index (SI) calculation. 16 ... [more ▼]

Top-height growth in even-aged stands of Norway spruce (Piceaabies (L.) Karst.) from Southern Belgium was modelled using functions which provide an algebraic solution for site index (SI) calculation. 16 well known growth model formulations were parameterized using a method which accounts for heterogeneous variance and autocorrelation on a dataset composed of stem analysis data completed by measuring the heights of all the branch whorls to allow for accurate height–age estimates. Comparison of the parameterized models showed that the oblique asymptotic function known as the Duplat and Tran-Ha III model was the most efficient on our dataset. Validation of the selected model on permanent sample plot data showed no evidence of bias over the full range of possible age, height, site index and densities encountered in Norway spruce stands of Southern Belgium. The new height growth model described represents a significant improvement over the previous model of Dagnelie et al. (1988), which was found to be unreliable and required the use of an iterative process to estimate SI. [less ▲]

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See detailModelling the vertical centrifugal casting of large bimetallic rolling mills
Studer, Léo ULg; Habraken, Anne ULg; Pirotton, Michel ULg et al

in Onate, E.; Papadrakis, M.; Schrefler, B. (Eds.) Proceedings of the Conference of Computational Methods for Coupled Problems in Science and Engineering 2 (2007)

In order to take into account the dynamical effects of molten metal during solidification, we want to interface a metal solidification solver with a flow dynamics solver.

Detailed reference viewed: 107 (9 ULg)
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See detailModelling the vertical spincasting of large bimettalic rolling mill rolls
Studer, Léo ULg; Detrembleur, Sylvain ULg; Habraken, Anne ULg et al

in Proceedings of the Second International Conference on Advances in Solidification Processes (ICASP-2) (2008)

In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics ... [more ▼]

In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics solver. [less ▲]

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See detailModelling the Western Mediterranean : from hydrology to hydrodynamics
Beckers, Jean-Marie ULg; Djenidi, Salim ULg; Nihoul, Jacques ULg

in Water Pollution Research (1991), 28

Detailed reference viewed: 26 (9 ULg)
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See detailModelling the β-amylase activity during red sorghum malting when Bacillus subtilis is used to control mould growth
Bwanganga Tawaba, Jean-Claude ULg; Bera, François ULg; Thonart, Philippe ULg

in Journal of Cereal Science (2013), 57

Steeping in dilute alkaline (0.2% NaOH) followed by resteeping in biocontrol (starters of Bacillus subtilis S499) has been used during red sorghum malting. The effect of steeping and germination ... [more ▼]

Steeping in dilute alkaline (0.2% NaOH) followed by resteeping in biocontrol (starters of Bacillus subtilis S499) has been used during red sorghum malting. The effect of steeping and germination conditions has been described using 2 functions: a Weibull 4-parameter model combined with a General Linear Model with Logarithm Link with significant goodness. Steeping conditions (combined use of NaOH and Bacillus subtilis S499) affects the synthesis capacity of grain: when Bacillus subtilis culture used in the steeping step is diluted, lnα increases, suggesting a loss of treatment efficacy. The germination temperature affects the β-amylase synthesis rate during the induction phase: the germination temperature increase is accompanied by a decrease of the β-amylase synthesis rate. During the repression phase of β-amylase synthesis, the effect of malting conditions was found to taper. [less ▲]

Detailed reference viewed: 65 (9 ULg)
See detailModelling time perception in rats : evidence for catastrophic interference in animal learning
French, R.; Ferrara, André ULg

Conference (1999)

For all intents and purposes, catastrophic interference, the sudden and complete forgetting of previously stored information upon learning new information, does not exist in healthy adult humans. But does ... [more ▼]

For all intents and purposes, catastrophic interference, the sudden and complete forgetting of previously stored information upon learning new information, does not exist in healthy adult humans. But does it exist other animals? In light of recent research done by McClelland, McNaughton, [less ▲]

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See detailModelling Time Reversal Applications in a Reverberation Chamber using the Current Image Method
Spirlet, Maxime; Broun, Valery; Camus, Philippe et al

Conference (2013, September)

In this paper, we present a numerical model to analyze Time Reversal applications in a reverberation chamber using the current image method. The principles behind this numerical model are presented in the ... [more ▼]

In this paper, we present a numerical model to analyze Time Reversal applications in a reverberation chamber using the current image method. The principles behind this numerical model are presented in the first part of the paper. The major advantage of this reverberation chamber model is that it requires a lot less computing time than usual solvers with qualitatively satisfying results. Next, an extension of our method to model Time Reversal Mirrors in reverberating cavities is described. Finally, two examples of Time Reversal refocusing using Time Reversal Mirrors of one or several elements are presented for illustration. [less ▲]

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See detailModelling total soil respiration in agricultural soils.
Buysse, Pauline ULg; Goffin, Stéphanie; Carnol, Monique ULg et al

Poster (2010, January 12)

Soil respiration is a process which results in CO2 release from the soil to the atmosphere. It comprises two main components. The first one is heterotrophic respiration: CO2 is produced by soil ... [more ▼]

Soil respiration is a process which results in CO2 release from the soil to the atmosphere. It comprises two main components. The first one is heterotrophic respiration: CO2 is produced by soil microorganisms while decomposing the substrate. The second one is autotrophic respiration in which CO2 originates from roots and rhizospheric organisms. All the CO2 is then transported to the surface by diffusion (see Goffin et al., this session). Many biotic and abiotic factors play a role in soil respiration, making this process complex to analyze and understand. Temperature often appears as the most important driving variable. Besides that, interest in the future CO2 emissions from agricultural soils has been growing. Indeed, these ecosystems are a major concern from environmental, economic and social points of view. In particular, the choice of cultural practices and residue management techniques has a strong influence on CO2 emissions from agricultural systems. This work aims at getting to a better understanding of soil respiration in agricultural soils. To reach this goal, many semi-mechanistic models have been previously developed at very different spatio-temporal scales. We intend to adapt such an existing model to crop soils, within a spatial scale of a cultivated field and an annual temporal scale. The model will be validated by using flux measurements carried out at three different crop sites situated in the Hesbaye region in Belgium (Lonzée) and in the South West of France (Lamasquère, Auradé). The study was focused first on soil heterotrophic respiration. Within this part, short term sensitivity of this component to temperature was studied by means of a laboratory incubation experiment. This one was performed with soil samples taken at the Lonzée site. Among the many interesting results we got, it showed a clear sensitivity of soil heterotrophic respiration to short term temperature changes. In parallel, the soil heterotrophic model was calibrated on soil chamber measurements taken at the Lonzée site (Belgium). Next steps in this part of the work will be to calibrate the model using the data from the French sites, and finally to validate the model on the three sites. Afterwards, an autotrophic respiration submodel will be implemented and the results compared to field measurements carried out at the three sites. A further development could consist in simulating agricultural practices to take their impacts on CO2 emissions from crops into account. [less ▲]

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See detailModelling Transient Air-water Flows in Civil and Environmental Engineering
Kerger, François ULg

Doctoral thesis (2010)

The present text, submitted to the University of Liège in fulfillment of the requirements for the degree of “Docteur en Sciences de l’Ingénieur”, aims at improving the understanding and description of ... [more ▼]

The present text, submitted to the University of Liège in fulfillment of the requirements for the degree of “Docteur en Sciences de l’Ingénieur”, aims at improving the understanding and description of air‐water interactions in transient flows. A particular emphasis is set on phenomena relevant in civil and environmental engineering, like rivers, pipes, and hydraulic structures. Theoretical results of this doctoral research may be summarized in two main propositions. First, I show that any mathematical model for free surface flows can be extended to pressurized flows. Second, the multiphase drift‐flux model is proven an adequate alternative to Navier‐ Stokes equations in civil and environmental engineering. These propositions underpin the development of original mathematical models and new computational codes (WOLF1D and WOLF IMPack). Validation and application on actual cases prove the efficiency of the new approach. Original concepts introduced in this thesis pave the way for further research on environmental flows, especially on the mathematical description of transport phenomena (pollutants, sediments) and heterogeneous interactions (vegetation, rough bed). [less ▲]

Detailed reference viewed: 97 (20 ULg)