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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: 31 (13 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: 106 (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)

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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.

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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

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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 ▲]

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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)

Detailed reference viewed: 51 (14 ULg)
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See detailModelling weathering processes at the catchment scale: The WITCH numerical model
Godderis, Y.; François, Louis ULg; Probst, A. et al

in Geochimica et Cosmochimica Acta (2006), 70(5), 1128-1147

A numerical model of chemical weathering in soil horizons and underlying bedrock (WITCH) has been coupled to a numerical model of water and carbon cycles in forest ecosystems (ASPECTS) to simulate the ... [more ▼]

A numerical model of chemical weathering in soil horizons and underlying bedrock (WITCH) has been coupled to a numerical model of water and carbon cycles in forest ecosystems (ASPECTS) to simulate the concentration of major species within the soil horizons and the stream of the Strengbach granitic watershed, located in the Vosges Mountains (France). For the first time, simulations of solute concentrations in soil layers and in the catchment river have been performed on a seasonal basis. The model is able to reproduce the concentrations of most major species within the soil horizons, as well as catching the first-order seasonal fluctuations of aqueous calcium, magnesium and silica concentrations. However, the WITCH model underestimates concentrations of Mg2+ and silica at the spring of the catchment stream, and significantly underestimates Ca2+ concentration. The deficit in calculated calcium can be compensated for by dissolution of trace apatite disseminated in the bedrock. However, the resulting increased Ca2+ release yields important smectite precipitation in the deepest model layer (in contact with the bedrock) and subsequent removal of large amount of silica and magnesium from solution. In contrast, the model accurately accounts for the concentrations of major species (Ca, Mg and silica) measured in the catchment stream when precipitation of clay minerals is not allowed. The model underestimation of Mg2+ and H4SiO4 concentrations when precipitation of well crystallized smectites is allowed strongly suggests that precipitation of well crystallized clay minerals is overestimated and that more soluble poorly crystallized and amorphous materials may be forming. In agreement with observations on other watersheds draining granitic rocks, this study indicates that highly soluble trace calcic phases control the aqueous calcium budget in the Strengbach watershed. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailModelling Young’s modulus on small clear specimens in relation to silvicultural treatment.
Jourez, Benoît ULg; Leclercq, André

Report (1994)

The aim of this research work performed in Task 11 "Modelling Young's modulus on small clear specimens in relation to silvicultural treatments" was the modelling of Young's modulus (MOE) on small clear ... [more ▼]

The aim of this research work performed in Task 11 "Modelling Young's modulus on small clear specimens in relation to silvicultural treatments" was the modelling of Young's modulus (MOE) on small clear specimens of 24 Belgian Norway spruces in relation with the silvicultural treatment. The aim of the research was also to compare Young's modulus on small clear specimens with Young's modulus on commercial size specimens with a view to defining the rate of prediction of wood quality of specimens including the natural timber defects. This work is corresponding to one task among the twelve of a large ECC Project entitled "SilvicuItural control and non destructive assessment of timber quality in plantation grown Spruces and Douglas fir" for which 210 trees have been sampled through 6 different European countries. The experimental raw material comes from the southern and eastern part<; of Belgium and concerns four different kinds of stands characterized by the site productivity class and the thinning intensity. Within each stand, the trees have been sampled in three different social positions classes. The small clear specimens have been marked off with reference to the radial and axial positions inside the 24 trees. On the whole 350 clear wood specimens have been selected and tested by two different laboratories in order to get young's modulus by a non destructive four points flexural method described by the French Standard NF B 51-016. Young's modulus appears to be positively related with specific gravity and negatively related with growth ring width. Stands growing on high productive sites or those submitted to low thinnings and also suppressed trees give rise to a stiffer wood. Among all these factors, only the social position of the tree within the stand influences significantly the Young's modulus values. Nevertheless, a slow growth producing a heavier timber is not always linked with a stiffer wood. Young's modulus differences between juvenile and adult wood vary in connection with the specific gravity class considered. In other words, juvenile wood is stiffer than adult wood when referring to low density classes, but adult wood becomes stiffer than juvenile wood when referring to high density classes. That means that the stiffness of adult wood is more sensitive to changes in specific gravity than the stiffness of juvenile wood. The distribution of Young's modulus in relation with specific gravity shows a higher variability when specific gravity increases. In searching the reasons for a higher Young's modulus variability when specific gravity increases by looking back to the population of clear specimens, we point out a very low slope of grain on some specimens and above all the presence of compression wood on other specimens. When rejecting these defects, then it appears that Young's modulus is more strongly related to specific gravity, thus giving rise to more accurate models. Among all these models, the best one is corresponding to a combination of variables such as specific gravity and growth ring width per sampling level within the tree. The variance analysis of residues of each model has revealed a tree effect always very highly significant. On the opposite, the other factors, as site productivity, thinning intensity and social position of the tree within the stand, have no significant effect on Young's modulus values. That means that inter trees variability is far higher than the other sources of variation (intra tree variability, site productivity variability, thinning intensity variability and social position variability). This also means that the general model established is valid whatever the silvicultural treatment could be. [less ▲]

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See detailModelling zooplankton impacts on sedimentation
Darchambeau, François ULg

Conference (2000, May 28)

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See detailModelling zooplankton impacts on sedimentation
Darchambeau, François ULg; Thys, Isabelle; Leporcq, Bruno et al

Poster (2000, June 05)

Detailed reference viewed: 1 (0 ULg)