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Peer Reviewed
See detailModeling simple lipid phase separation and effects of amphiphilic molecules on lipid domains
Lins, Laurence ULg; Deleu, Magali ULg; Mingeot-Leclercq, Marie-Paule et al

Poster (2013, April 28)

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See detailModeling soil heterotrophic respiration with an enzyme-based model: first comparison with field data and suggestions of improvements
Buysse, Pauline ULg; Longdoz, Bernard; Debacq, Alain ULg et al

in Geophysical Research Abstracts (2011, April 07), 13

Detailed reference viewed: 28 (12 ULg)
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See detailModeling soil respiration in wheat fields
Delogu, Emilie; Le Dantec, Valérie; Mordelet, Patrick et al

Poster (2013, April 09)

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See detailModeling Species Distributions from Heterogeneous Data for the Biogeographic Regionalization of the European Bryophyte Flora
Mateo, R. G. A; Vanderpoorten, Alain ULg; Muñoz, J. B D et al

in PLoS ONE (2013), 8(2),

The definition of biogeographic regions provides a fundamental framework for a range of basic and applied questions in biogeography, evolutionary biology, systematics and conservation. Previous research ... [more ▼]

The definition of biogeographic regions provides a fundamental framework for a range of basic and applied questions in biogeography, evolutionary biology, systematics and conservation. Previous research suggested that environmental forcing results in highly congruent regionalization patterns across taxa, but that the size and number of regions depends on the dispersal ability of the taxa considered. We produced a biogeographic regionalization of European bryophytes and hypothesized that (1) regions defined for bryophytes would differ from those defined for other taxa due to the highly specific eco-physiology of the group and (2) their high dispersal ability would result in the resolution of few, large regions. Species distributions were recorded using 10,000 km2 MGRS pixels. Because of the lack of data across large portions of the area, species distribution models employing macroclimatic variables as predictors were used to determine the potential composition of empty pixels. K-means clustering analyses of the pixels based on their potential species composition were employed to define biogeographic regions. The optimal number of regions was determined by v-fold cross-validation and Moran's I statistic. The spatial congruence of the regions identified from their potential bryophyte assemblages with large-scale vegetation patterns is at odds with our primary hypothesis. This reinforces the notion that post-glacial migration patterns might have been much more similar in bryophytes and vascular plants than previously thought. The substantially lower optimal number of clusters and the absence of nested patterns within the main biogeographic regions, as compared to identical analyses in vascular plants, support our second hypothesis. The modelling approach implemented here is, however, based on many assumptions that are discussed but can only be tested when additional data on species distributions become available, highlighting the substantial importance of developing integrated mapping projects for all taxa in key biogeographically areas of Europe, and the Mediterranean peninsulas in particular. © 2013 Mateo et al. [less ▲]

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See detailModeling Stationary and Evolving Discontinuities with Finite Elements
Moës, Nicolas; Béchet, Eric ULg

in Owen, D. R. J.; Onate, E. (Eds.) VII International Conference on Computational Plasticity COMPLAS 2003 (2003)

A methodology for treating non-planar three-dimensional cracks with geometries that are independent of the mesh is summarized. The method is based on the extended finite element method, in which the crack ... [more ▼]

A methodology for treating non-planar three-dimensional cracks with geometries that are independent of the mesh is summarized. The method is based on the extended finite element method, in which the crack discontinuity is introduced as a Heaviside step function via a partition of unity. In addition, branch functions are introduced for all elements containing the crack front. The crack geometry is described by two signed distance functions (level sets), which in turn can be defined by nodal values. Consequently, no explicit representation of the crack is needed. A Hamilton-Jacobi equation is used to update the level sets as the crack grows. Numerical experiments show the robustness of the method in treating cracks with significant changes in topology. The method is readily extendable to inelastic fracture problems. [less ▲]

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See detailModeling stochastic excitation of acoustic modes in stars: present status and perspectives
Samadi, R.; Belkacem, Kevin ULg; Goupil, M*-J et al

in Communications in Asteroseismology (2008), 157

Solar-like oscillations have now been detected for more than ten years and their frequencies measured for a still growing number of stars with various characteristics (e.g. mass, chemical composition ... [more ▼]

Solar-like oscillations have now been detected for more than ten years and their frequencies measured for a still growing number of stars with various characteristics (e.g. mass, chemical composition, evolutionary stage ...). Excitation of such oscillations is attributed to turbu- lent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich & Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modeled and by the assumed sources of excitation. We briefly review here the different underlying approximations and assumptions of those models. A second part shows that computed mode excitation rates crucially depend on the way time-correlations between eddies are described but also on the surface metal abundance of the star. [less ▲]

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See detailA modeling system handling the wide range of time scales involved in sediment transport processes
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Proc. 6th International SedNet conference (2009)

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Peer Reviewed
See detailModeling the black grouse population : a tool for management.
Loneux, Michèle ULg; Lindsey, J.; Poncin, Pascal ULg

Conference (2007)

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See detailModeling the Black Sea and the Mediterranean Sea hydrodynamics: a comparative study
Beckers, Jean-Marie ULg; Elmoussaoui, A.; Rixen, M. et al

in Balopoulos, E.; Chronis, G.; Lipiatou, E. (Eds.) et al International conference. Oceanography of the eastern Mediterranean and Black Sea. Similarities and differences of two interconnected basins, Zappeion international conference Centre (2000)

The application of the GHER 3D primitive equation model to the simulation of the seasonal cycle of the Mediterranean and Black Sea circulation will be shown. The two basins are very illustrative for ... [more ▼]

The application of the GHER 3D primitive equation model to the simulation of the seasonal cycle of the Mediterranean and Black Sea circulation will be shown. The two basins are very illustrative for either concentration or dilution basins, and modelling such different systems needs some special attention with respect to the representation of the water masses and mixing between the different layers. The strength of the variability of both basins will be compared, including comparison with climatological data. Turbulent characteristics in both cases alalysed, showing that at the scales under investigations, both turbulent regimes are close to a balance between production, destruction and vertical diffusion of turbulence. ft is also shown how the river dominaled Black Sea exhibits specific free surface behaviors while the Mediterranean Sea exhibits specific deep water formations leading both to a different kind of vertical mixing. [less ▲]

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See detailModeling the bone mineralization density distribution and its time evolution
Ruffoni, Davide ULg; Fratzl, P.; Roschger, P. et al

in BONE (2006)

Detailed reference viewed: 10 (1 ULg)
Peer Reviewed
See detailModeling the dependence between extreme operational losses and economic factors: a conditional semi-parametric Generalized Pareto approach
Hambuckers, julien ULg; Heuchenne, Cédric ULg; Lopez, Olivier

Conference (2015, December)

In this paper, we model the severity distribution of operational losses data, condi- tional on some covariates. Indeed, previous studies [Chernobai et al., 2011, Cope et al., 2012, Chavez-Demoulin et al ... [more ▼]

In this paper, we model the severity distribution of operational losses data, condi- tional on some covariates. Indeed, previous studies [Chernobai et al., 2011, Cope et al., 2012, Chavez-Demoulin et al., 2014a] suggest that this distribution might be in uenced by macroeconomic and rm-speci c factors. We introduce a conditional Generalized Pareto model, where the shape parameter is an unknown function of a linear combina- tion of the covariates. More precisely, we rely on a single-index assumption to perform a dimension reduction that enables to use univariate nonparametric techniques. Hence, we su er neither from too strong parametric assumption nor from the curse of dimen- sionality. Then, we develop an iterative approach to estimate this model, based on the maximisation of a semiparametric likelihood function. Finally, we apply this method- ology on a novel database provided by the bank UniCredit. We use rm-speci c factors to estimate the conditional shape parameter of the severity distribution. Our analysis suggests that the leverage ratio of the company, the proportion of the revenue coming from fees as well as the risk category have an important impact on the tail thickness of this distribution and thus on the probability of su ering from large operational losses. [less ▲]

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See detailModeling the dependence of respiration and photosynthesis upon light, acetate, carbon dioxide, nitrate and ammonium in Chlamydomonas reinhardtii using design of experiments and multiple regression
Gerin, Stéphanie ULg; Mathy, Gregory; Franck, Fabrice ULg

in BMC Systems Biology (2014), 8(96),

Background: In photosynthetic organisms, the influence of light, carbon and inorganic nitrogen sources on the cellular bioenergetics has extensively been studied independently, but little information is ... [more ▼]

Background: In photosynthetic organisms, the influence of light, carbon and inorganic nitrogen sources on the cellular bioenergetics has extensively been studied independently, but little information is available on the cumulative effects of these factors. Here, sequential statistical analyses based on design of experiments (DOE) coupled to standard least squares multiple regression have been undertaken to model the dependence of respiratory and photosynthetic responses (assessed by oxymetric and chlorophyll fluorescence measurements) upon the concomitant modulation of light intensity as well as acetate, CO2, nitrate and ammonium concentrations in the culture medium of Chlamydomonas reinhardtii. The main goals of these analyses were to explain response variability (i.e. bioenergetic plasticity) and to characterize quantitatively the influence of the major explanatory factor(s). Results: For each response, 2 successive rounds of multiple regression coupled to one-way ANOVA F-tests have been undertaken to select the major explanatory factor(s) (1st-round) and mathematically simulate their influence (2nd-round). These analyses reveal that a maximal number of 3 environmental factors over 5 is sufficient to explain most of the response variability, and interestingly highlight quadratic effects and second-order interactions in some cases. In parallel, the predictive ability of the 2nd-round models has also been investigated by k-fold cross-validation and experimental validation tests on new random combinations of factors. These validation procedures tend to indicate that the 2nd-round models can also be used to predict the responses with an inherent deviation quantified by the analytical error of the models. Conclusions: Altogether, the results of the 2 rounds of modeling provide an overview of the bioenergetic adaptations of C. reinhardtii to changing environmental conditions and point out promising tracks for future in-depth investigations of the molecular mechanisms underlying the present observations. [less ▲]

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See detailModeling the dissociation and ionization of a sputtered organic molecule
Solomko, V.; Verstraete, Matthieu ULg; Delcorte, A. et al

in Applied Surface Science (2006), 252

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See detailModeling the Distribution of Marketable Timber Products of Private Teak (Tectona grandis L.f.) Plantations
Fonton, Noël Houédougbé; Atindogbé, Gilbert; Akossou, Arcadius Y. et al

in Open Journal of Forestry (2013), 3(4), 115-121

Management of marketable products of private plantations will not be sustainable without class girth be-ing identifiable readily. Modeling marketable products is a key to obtain good fitness between ... [more ▼]

Management of marketable products of private plantations will not be sustainable without class girth be-ing identifiable readily. Modeling marketable products is a key to obtain good fitness between observed and theoretical girth distribution. We determine the best parameter recovery method with the Weibull function for two sylvicultural regimes (coppice and high forest). Data on stand variables were collected from 1101 sample plots. The three Weibull function parameters were estimated with three parameters re-covery methods: the maximum likelihood method, the method of moments and the method of percentiles. Stepwise regression and the simultaneously re-estimated parameter using the Seemingly Unrelated Re-gression Estimation were applied to model each parameter. The results indicated that the three methods successfully predicted girth size distributions within the sample stands. The method of moments was the best one with lowest values of Reynolds error index and Kolmogorov-Smirnov statistic however the syl-vicultural regimes. The Weibull parameter distribution model developed for each of the two sylvicultural regimes was quite reliable. [less ▲]

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See detailModeling the ductile fracture and the plastic anisotropy of DC01 steel at room temperature and low strain rates
Tuninetti, Victor; Yuan, Sibo ULg; Gilles, Gaëtan et al

Scientific conference (2016, September)

This paper presents different extensions of the classical GTN damage model implemented in a finite element code. The goal of this study is to assess these extensions for the numerical prediction of ... [more ▼]

This paper presents different extensions of the classical GTN damage model implemented in a finite element code. The goal of this study is to assess these extensions for the numerical prediction of failure of a DC01 steel sheet during a single point incremental forming process, after a proper identification of the material parameters. It is shown that the prediction of failure appears too early compared to experimental results. Though, the use of the Thomason criterion permitted to delay the onset of coalescence and consequently the final failure. [less ▲]

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See detailModeling the effect of abrupt acid and osmotic shifts within the growth region and across growth boundaries on adaptation and growth of Listeria monocytogenes.
Le Marc, Y.; Skandamis, P. N.; Belessi, C. I. A. et al

in Applied and environmental microbiology (2010), 76(19), 6555-63

This study aims to model the effects of acid and osmotic shifts on the intermediate lag time of Listeria monocytogenes at 10 degrees C in a growth medium. The model was developed from data from a previous ... [more ▼]

This study aims to model the effects of acid and osmotic shifts on the intermediate lag time of Listeria monocytogenes at 10 degrees C in a growth medium. The model was developed from data from a previous study (C. I. A. Belessi, Y. Le Marc, S. I. Merkouri, A. S. Gounadaki, S. Schvartzman, K. Jordan, E. H. Drosinos, and P. N. Skandamis, submitted for publication) on the effects of osmotic and pH shifts on the kinetics of L. monocytogenes. The predictive ability of the model was assessed on new data in milk. The effects of shifts were modeled through the dependence of the parameter h(0) ("work to be done" prior to growth) induced on the magnitude of the shift and/or the stringency of the new environmental conditions. For shifts across the boundary, the lag time was found to be affected by the length of time for which the microorganisms were kept at growth-inhibiting conditions. The predicted concentrations of L. monocytogenes in milk were overestimated when the effects of this shift were not taken into account. The model proved to be suitable to describe the effects of osmotic and acid shifts observed both within the growth domain and across the growth boundaries of L. monocytogenes. [less ▲]

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See detailModeling the effect of clay drapes on pumping test response in a cross-bedded aquifer using multiple-point geostatistics
Huysmans, Marijke; Dassargues, Alain ULg

in Journal of Hydrology (2012), 450-451

This study investigates whether fine-scale clay drapes can cause an anisotropic pumping test response at a much larger scale. A pumping test was performed in a sandbar deposit consisting of cross-bedded ... [more ▼]

This study investigates whether fine-scale clay drapes can cause an anisotropic pumping test response at a much larger scale. A pumping test was performed in a sandbar deposit consisting of cross-bedded units composed of materials with different grain sizes and hydraulic conductivities. The measured drawdown values in the different observation wells reveal an anisotropic or elliptically-shaped pumping cone. The major axis of the pumping ellipse is parallel with the strike of cm to m-scale clay drapes that are observed in several outcrops. To determine (1) whether this large-scale anisotropy can be the result of fine-scale clay drapes and (2) whether application of multiple-point geostatistics can improve interpretation of pumping tests, this pumping test is analyzed with a local 3D groundwater model in which fine-scale sedimentary heterogeneity is modelled using multiple-point geostatistics. To reduce CPU and RAM demand of the multiple-point geostatistical simulation step, edge properties indicating the presence of irregularly-shaped surfaces are directly simulated. Results show that the anisotropic pumping cone can be attributed to the presence of the clay drapes. Incorporating fine-scale clay drapes results in a better fit between observed and calculated drawdowns. These results thus show that fine-scale clay drapes can cause an anisotropic pumping test response at a much larger scale and that the combined approach of multiple-point geostatistics and cell edge properties is an efficient method for integrating fine-scale features in larger scale models. [less ▲]

Detailed reference viewed: 60 (7 ULg)