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See detailModel complexity and performance: How far can we simplify?
Raick, Caroline ULg; Soetaert, Karline; Grégoire, Marilaure ULg

in Progress in Oceanography (2006), 70(1), 27-57

Handling model complexity and reliability is a key area of research today. While complex models containing sufficient detail have become possible due to increased computing power, they often lead to too ... [more ▼]

Handling model complexity and reliability is a key area of research today. While complex models containing sufficient detail have become possible due to increased computing power, they often lead to too much uncertainty. On the other hand, very simple models often crudely oversimplify the real ecosystem and can not be used for management purposes. Starting from a complex and validated 1D pelagic ecosystem model of the Ligurian Sea (NW Mediterranean Sea), we derived simplified aggregated models in which either the unbalanced algal growth, the functional group diversity or the explicit description of the microbial loop was sacrificed. To overcome the problem of data availability with adequate spatial and temporal resolution, the outputs of the complex model are used as the baseline of perfect knowledge to calibrate the simplified models. Objective criteria of model performance were used to compare the simplified models' results to the complex model output and to the available data at the DYFAMED station in the central Ligurian Sea. We show that even the simplest (NPZD) model is able to represent the global ecosystem features described by the complex model (e.g. primary and secondary productions, particulate organic matter export flux, etc.). However, a certain degree of sophistication in the formulation of some biogeochemical processes is required to produce realistic behaviors (e.g. the phytoplankton competition, the potential carbon or nitrogen limitation of the zooplankton ingestion, the model trophic closure, etc.). In general, a 9 state-variable model that has the functional group diversity removed, but which retains the bacterial loop and the unbalanced algal growth, performs best. (C) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailModel Discrimination Tools in Apoptosis
Cimatoribus, C.; Eißing, T.; N., Elvassore et al

in Foundations of Systems Biology in Engineering, FOSBE 2005 (2005, August)

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See detailModel emulsion systems
Blecker, Christophe ULg; Paquot, Michel ULg

Conference (1995, April)

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See detailModel error space and data assimilation in the Mediterranean Sea and nested models
Vandenbulcke, Luc ULg

Doctoral thesis (2007)

In this work, we implemented the GHER hydrodynamic model in the Gulf of Lions (resolution 1/100 °). This model is nested interactively in another model covering the North-Western basin of the ... [more ▼]

In this work, we implemented the GHER hydrodynamic model in the Gulf of Lions (resolution 1/100 °). This model is nested interactively in another model covering the North-Western basin of the Mediterranean Sea (resolution 1/20°), itself nested in a model covering the whole basin (1/4 °). A data assimilation filter, called the SEEK filter, is used to test in which of those grids observations taken in the Gulf of Lions are best assimilated. Therefore, twin experiments are used: a reference run is considered as the truth, and another run, starting from different initial conditions, assimilates pseudo-observations coming from the reference run. It appeared that, in order to best constrain the coastal model, available data should be assimilated in that model. The most efficient setup, however, is to group all the state vectors from the 3 grids into a single vector, and hence coherently modify the 3 domains at once during assimilation cycles. Operational forecasting with nested models often only uses so-called passive nesting: no data feedback happens from the regional models to the global model. We propose a new idea: to use data assimilation as a substitute for the feedback. Using again twin experiments, we show that when assimilating outputs from the regional model in the global model, this has bene cial impacts for the subsequent forecasts in the regional model. The data assimilation method used in those experiments corrects errors in the models using only some privileged directions in the state space. Furthermore, these directions are selected from a previous model run. This is a weakness of the method when real observations are available. We tried to build new directions of the state space using an ensemble run, this time covering only the Mediterranean basin (without grid nesting). This led to a quantitative characterization of the forecast errors we might expect when various parameters and external forcings are affected by uncertainties. Finally, using these new directions, we tried to build a statistical model supposed to simulate the hydrodynamical model using only a fraction of the computer resources needed by the latter. To achieve this goal, we tried out artifficial neural networks, nearest-neighbor and regression trees. This study constitutes only the first step toward an innovative statistical model, as in its present form, only a few degrees of freedom are considered and the primitive equation model is still required to build the AL method. We tried forecasting at 2 different time horizons: one day and one week. [less ▲]

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See detailModel Extension Facilitates Parameter Estimation for Kinetic Reaction Networks
Fey, Dirk; Bullinger, Eric ULg

Poster (2007, September)

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See detailModel Extension Facilitates Parameter Estimation for Kinetic Reaction Networks
Fey, Dirk; Bullinger, Eric ULg

Poster (2007)

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See detailModel Extension Facilitates Parameter Estimation for Kinetic Reaction Networks
Fey, Dirk; Bullinger, Eric ULg

Poster (2007, September)

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See detailA model for assessing water chemistry by using aquatic bryophyte assemblages in north-eastern France
Vanderpoorten, Alain ULg; Thiébaut, G.; Trémolières, M. et al

in Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie = Proceedings of the International Association of Theoretical and Applied Limnology (2001), 27

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See detailA MODEL FOR CELL/MATRIX GROWTH ON 3D SURFACES: A COUPLING OF LEVEL SET METHOD AND BRINKMAN EQUATION
Guyot, Yann ULg; Papantoniou, Ioannis; Chai, Yoke Chin et al

Conference (2013, September 11)

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See detailA model for concrete in the fire situation and its application in structural fire engineering
Gernay, Thomas ULg

Scientific conference (2014, October 21)

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See detailA model for optimal sea-river shipping management
Marchal, Jean ULg; Zhang, Z. M.

in Proceedings of the Third Research Roundtable Conference on Shortsea Shipping (1996, June)

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See detailA model for promoting poultry industry development in Togo: feeding improvement, capacity building and extension
Tona, K.; Kamers, K.; Teteh, A. et al

in World's Poultry Science Journal (2014), 70

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See detailA model for promoting poultry industry development in Togo: Part 1. Management practices and incubation conditions
Tona, K.; Agbonon, A.; Eklu-Gadegbeku, K. et al

in International Journal of Poultry Science (2014), 13(3), 176-184

In commercial poultry husbandry practice, the hatchery takes over the incubation of bird eggs in order to provide as many day-old chicks as needed at any time to farmers. The main bottleneck for poultry ... [more ▼]

In commercial poultry husbandry practice, the hatchery takes over the incubation of bird eggs in order to provide as many day-old chicks as needed at any time to farmers. The main bottleneck for poultry industry development in Togo is the lack of day-old chick supply. Indeed, there is no proficient hatchery which can cover the needs of the farmers because of lack of information about hatchery management or people trained as hatchery managers. Also, there is lack of information about management practice aspects, etc. With the aim to promote poultry industry in Togo, an interuniversity project [Catholic University of Leuven (KUL) and University of Lome (UL)] as a model of poultry industry development was implemented. Specific objectives of the current project are to implement research and development activities on better conditions of incubation and adapted management practices focusing mainly on (1) Effect of early transferring of layer breeders hatching eggs on embryo parameters and hatchability, (2) Comparison of different chicken genotypes in Embryo Physiology, (3) Effects of heat conditioning at d 16 to 18 of incubation or during early broiler rearing on embryo physiology, post-hatch growth performance and heat tolerance, (4) Effect of low albumen quantity on chick embryo and post-hatch parameters, (5) Effects of In ovo-administration of L-carnitine on hatching events and juvenile performance of layer-type chick, (6) Interaction effects of mixing hatching eggs of differential embryo growth trajectory and incubator CO2 concentration on embryo physiological parameters, (7) Effect of delayed feed access on production and blood parameters of layer-type chicks and (8) Induced moulting of layer chickens. © Asian Network for Scientific Information, 2014. [less ▲]

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See detailA model for ternary projective relations between regions
Billen, Roland ULg; Clementini, Eliseo

in Lecture Notes in Computer Science (2004)

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See detailA model for the bright rim in RCW 62.
Manfroid, Jean ULg

in Astronomy and Astrophysics (1976), 51

Abstract image available at: http://cdsads.u-strasbg.fr/abs/1976A&A....51..235M

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See detailA model for the generalized parton distribution of the pion
Stassart, Pierre ULg; Bissey, F.; Cudell, Jean-René ULg et al

in AIP Conference Proceedings (2005), 756

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See detailA model for the off-forward structure functions of the pion
Bissey, F.; Cudell, Jean-René ULg; Cugnon, Joseph ULg et al

in Physics Letters B (2004), 587(3-4), 189-200

We extend our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward y*pi -->. gamma*pi scattering ... [more ▼]

We extend our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward y*pi -->. gamma*pi scattering amplitude is evaluated in the chiral limit (m(pi) = 0) and related to the twist-two and twist-three generalised parton distributions H, H-3, (H) over tilde (3). Non-perturbative effects, linked to the size of the pion and still preserving gauge invariance, are included. Remarkable new relations between H, H3 and (H) over tilde (3) are obtained and discussed. (C) 2004 Published by Elsevier B.V. [less ▲]

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See detailA model for the origin and petrogenesis of the red stromatactis limestone of Paleozoic carbonate mounds
Bourque, P. A.; Boulvain, Frédéric ULg

in Journal of Sedimentary Petrology (1993), 63(4), 607-619

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See detailA model for the pion structure function
Bissey, F.; Cudell, Jean-René ULg; Cugnon, Joseph ULg et al

in Physics Letters B (2002), 547(3-4), 210-218

The pion structure function is investigated in a simple model, where pion and constituent quark fields are coupled through the simplest pseudoscalar coupling. The imaginary part of the forward gamma*pi ... [more ▼]

The pion structure function is investigated in a simple model, where pion and constituent quark fields are coupled through the simplest pseudoscalar coupling. The imaginary part of the forward gamma*pi --> gamma*pi evaluated and related to the structure functions. It is shown that the introduction of non-perturbative effects linked to the size of the pion and preserving gauge invariance, allows a connection with the quark distribution. It is predicted that higher-twist terms become negligible for Q(2) larger than similar to 2 GeV2 and that quarks in the pion have a momentum fraction smaller than in the proton case. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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