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See detailDes preuves : où, quand, comment ?
Rigo, Michel ULg

Speech/Talk (2017)

Expliquer une démonstration, prouver un résultat, énoncer une conjecture sont des activités qui font partie intégrante du quotidien du mathématicien. Dans ce court exposé, je passerai en revue quelques ... [more ▼]

Expliquer une démonstration, prouver un résultat, énoncer une conjecture sont des activités qui font partie intégrante du quotidien du mathématicien. Dans ce court exposé, je passerai en revue quelques exemples de preuves. Certaines sont classiques ou historiques, d'autres sont peut-être moins connues : des preuves à la Ramanujan, des preuves sans mots, le théorème des quatre couleurs, la conjecture de Klepler sur l'empilement de sphères,... Le but est de partager mes réflexions comme chercheur « professionnel » et enseignant. [less ▲]

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See detailThe Prediction-Focused Approach: An opportunity for hydrogeophysical data integration and interpretation
Hermans, Thomas ULg; Nguyen, Frédéric ULg; Klepikova, Maria et al

Conference (2017, April 28)

Hydrogeophysics is an interdisciplinary field of sciences aiming at a better understanding of subsurface hydrological processes. If geophysical surveys have been successfully used to qualitatively ... [more ▼]

Hydrogeophysics is an interdisciplinary field of sciences aiming at a better understanding of subsurface hydrological processes. If geophysical surveys have been successfully used to qualitatively characterize the subsurface, two important challenges remain for a better quantification of hydrological processes: (1) the inversion of geophysical data and (2) their integration in hydrological subsurface models. The classical inversion approach using regularization suffers from spatially and temporally varying resolution and yields geologically unrealistic solutions without uncertainty quantification, making their utilization for hydrogeological calibration less consistent. More advanced techniques such as coupled inversion allow for a direct use of geophysical data for conditioning groundwater and solute transport model calibration. However, the technique is difficult to apply in complex cases and remains computationally demanding to estimate uncertainty. In a recent study, we investigate a prediction-focused approach (PFA) to directly estimate subsurface physical properties from geophysical data, circumventing the need for classic inversions. In PFA, we seek a direct relationship between the data and the subsurface variables we want to predict (the forecast). This relationship is obtained through a prior set of subsurface models for which both data and forecast are computed. A direct relationship can often be derived through dimension reduction techniques. PFA offers a framework for both hydrogeophysical “inversion” and hydrogeophysical data integration. For hydrogeophysical “inversion”, the considered forecast variable is the subsurface variable, such as the salinity. An ensemble of possible solutions is generated, allowing uncertainty quantification. For hydrogeophysical data integration, the forecast variable becomes the prediction we want to make with our subsurface models, such as the concentration of contaminant in a drinking water production well. Geophysical and hydrological data are combined to derive a direct relationship between data and forecast. We illustrate the process for the design of an aquifer thermal energy storage (ATES) system. An ATES system can theoretically recover in winter the heat stored in the aquifer during summer. In practice, the energy efficiency is often lower than expected due to spatial heterogeneity of hydraulic properties combined to a non-favorable hydrogeological gradient. A proper design of ATES systems should consider the uncertainty of the prediction related to those parameters. With a global sensitivity analysis, we identify sensitive parameters for heat storage prediction and validate the use of a short term heat tracing experiment monitored with geophysics to generate informative data. First, we illustrate how PFA can be used to successfully derive the distribution of temperature in the aquifer from ERT during the heat tracing experiment. Then, we successfully integrate the geophysical data to predict medium-term heat storage in the aquifer using PFA. The result is a full quantification of the posterior distribution of the prediction conditioned to observed data in a relatively limited time budget. [less ▲]

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See detailL’espace public comme tribune
Brahy, Rachel ULg

Conference given outside the academic context (2017)

L’espace public a de tous temps été une tribune, un lieu où débattre, haranguer la foule, partager des opinions ou rassembler des soutiens. Le chapiteau de cirque et l’art dans la rue occupent cet espace ... [more ▼]

L’espace public a de tous temps été une tribune, un lieu où débattre, haranguer la foule, partager des opinions ou rassembler des soutiens. Le chapiteau de cirque et l’art dans la rue occupent cet espace sans pour autant l’utiliser comme tribune. La présentation d’un spectacle à un public implique pourtant des questions de mise en scène qui sont déjà une forme d’engagement, celui de l’artiste au service de sa création. Il n’y a alors plus qu’un petit pas à franchir pour se poser la question de l’engagement de l’artiste dans le monde. Avec Didier Balsaux, Directeur artistique des Royales Marionnettes ; Alain Moreau, Directeur du Tof théâtre ; Sara Amari, Thank You for Coming ; Charles Culot, auteur de “Nourrir l’humanité” ; Rachel Brahy, Coordinatrice scientifique de la Maison des Sciences de l’Homme Ulg ; … Modérateur : Antoine Laubin, Co-directeur éditorial de la revue Alternatives théâtrales Rapporteuse: Laurence Bertels [less ▲]

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See detailStreamlining NCA independence in reforming Regulation 1/2003: time to take incongruent accountability realities (more) seriously?
Van Cleynenbreugel, Pieter ULg

Scientific conference (2017, April 28)

This presentation analyses argues that the Commission’s reform suggestions aimed at streamlining NCAs into independent administrative agencies appear to neglect this variety of accountability mechanisms ... [more ▼]

This presentation analyses argues that the Commission’s reform suggestions aimed at streamlining NCAs into independent administrative agencies appear to neglect this variety of accountability mechanisms underlying current NCA institutional organisation and functioning. Given that those mechanisms each harbour incongruent expectations regarding the organisation and functioning of independent NCAs, failure to acknowledge such incongruence may in practice lead to less effective competition law enforcement. Its purpose is therefore to uncover the different NCA independence perspectives underlying those accountability mechanisms and to look for legally sound ways to make them converge when designing or upgrading NCA independence in the context of the Regulation 1/2003 reform. [less ▲]

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See detailPathological hip fractures
KURTH, William ULg

Conference (2017, April 28)

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See detailHedge fund trading strategies and performance: theory and practice
Lambert, Marie ULg

Scientific conference (2017, April 28)

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See detailOccurrence of greenhouse gases (CO2, N2O and CH4) in groundwater of the Walloon Region (Belgium).
Jurado Elices, Anna ULg; Borges, Alberto ULg; Pujades, Estanislao ULg et al

Conference (2017, April 28)

Greenhouse gases (GHGs) are an environmental problem because their concentrations in the atmosphere have continuously risen since the industrial revolution. They can be indirectly transferred to the ... [more ▼]

Greenhouse gases (GHGs) are an environmental problem because their concentrations in the atmosphere have continuously risen since the industrial revolution. They can be indirectly transferred to the atmosphere through groundwater discharge into surface water bodies such as rivers. However, their occurrence is poorly evaluated in groundwater. The aim of this work is to identify the hydrogeological contexts (e.g., chalk and limestone aquifers) and the most conductive conditions for the generation of GHGs in groundwater at a regional scale. To this end, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) concentrations, major and minor elements and environmental isotopes were monitored in several groundwater bodies of the Walloon Region (Belgium) from September 2014 to June 2016. The concentrations of GHGs in groundwater ranged from 1769 to 100519 ppm for the partial pressure of CO2 and from 0 to 1064 nmol/L and 1 to 37062 nmol/L for CH4 and N2O respectively. Over- all, groundwater was supersaturated in GHGs with respect to atmospheric equilibrium, suggesting that groundwater contribute to the atmospheric GHGs budget. Prior inspection of the data suggested that N2O in groundwater can be produced by denitrification and nitrification. The most suitable conditions for the accumulation of N2O are promoted by intermediate dissolved oxygen concentrations (2.5-3 mg L−1) and the availability of nitrate (NO3 ). These observations will be compared with the isotopes of NO3 . CH4 was less detected and at lower concentration than N2O, suggesting that groundwater redox conditions are not reducing enough to promoted the production of CH4. The results will be presented and discussed in detail in the presentation. [less ▲]

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See detailN2O eddy covariance fluxes : from field measurements to flux analysis
Lognoul, Margaux ULg; Debacq, Alain ULg; Heinesch, Bernard ULg et al

Poster (2017, April 28)

N2O eddy covariance data were collected for a complete season of sugar beet crop (from first fertilization to harvest). Data treatment and preliminary results are presented.

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See detailThree-dimensional modelling of the hydrodynamics of the Southern Bight of the North Sea: first results
Ivanov, Evgeny ULg; Capet, Arthur ULg; Barth, Alexander ULg et al

Poster (2017, April 28)

In the frame of the Belgian research project FaCE-It (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of ... [more ▼]

In the frame of the Belgian research project FaCE-It (Functional biodiversity in a Changing sedimentary Environment: Implications for biogeochemistry and food webs in a managerial setting), the impact of dredging activities andoffshorewindfarminstallationonthespatialdistributionofsedimentgrainsize,biodiversityandbiogeochemistry will be estimated in the Southern Bight of the North Sea (SBNS) with a focus on the Belgian Coastal Zone (BCZ). To reach this goal, the three-dimensional hydrodynamical model ROMS-COAWST is implemented in the SBNS in order to simulate the complex hydrodynamics and sediment transport. Two levels of nesting are used to reach a resolutionof250mintheBCZ.Themodelisforcedattheair-seainterfacebythe6-hourlyECMWFERA-interim atmospheric dataset and at the open boundaries by the coarse resolution model results available from CMEMS (Copernicus Marine Environment Monitoring Service), and also considers tides and 4 main rivers (Scheldt, Rhine with Maas, Thames and Seine). Two types of simulations have been performed: a 10-years climatological simulation and a simulation over 20032013toinvestigatetheinterannualdynamics.Themodelskillsareevaluatedbycomparingitsoutputstohistorical data (e.g. salinity, temperature and currents) from remote sensing and in-situ. The sediment transport module will then be implemented and its outputs compared to historical and newly collected (in the frame of FaCE-iT) observations on grain size distribution as well as with satellite Suspended Particulate Matter (SPM) images. This will allow assessing the impact of substrate modification due to offshore human activities at local and regional scales. [less ▲]

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See detailPosterior approach in total hip arthroplasty
KURTH, William ULg

Conference (2017, April 28)

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See detailGlobally significant greenhouse-gas emissions from African inland waters
Borges, Alberto ULg; Bouilon, S

Conference (2017, April 28)

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See detailMotion analysis: a prevention tool
Schwartz, Cédric ULg; CROISIER, Jean-Louis ULg; Forthomme, Bénédicte ULg et al

Conference (2017, April 28)

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See detailA landslide susceptibility map of Africa
Broeckx, Jente; Vanmaercke, Matthias ULg; Duchateau, Rica et al

Conference (2017, April 28)

Studies on landslide risks and fatalities indicate that landslides are a global threat to humans, infrastructure and the environment, certainly in Africa. Nonetheless our understanding of the spatial ... [more ▼]

Studies on landslide risks and fatalities indicate that landslides are a global threat to humans, infrastructure and the environment, certainly in Africa. Nonetheless our understanding of the spatial patterns of landslides and rockfalls on this continent is very limited. Also in global landslide susceptibility maps, Africa is mostly underrepresented in the inventories used to construct these maps. As a result, predicted landslide susceptibilities remain subject to very large uncertainties. This research aims to produce a first continent-wide landslide susceptibility map for Africa, calibrated with a well-distributed landslide dataset. As a first step, we compiled all available landslide inventories for Africa. This data was supplemented by additional landslide mapping with Google Earth in underrepresented regions. This way, we compiled 60 landslide inventories from the literature (ca. 11000 landslides) and an additional 6500 landslides through mapping in Google Earth (including 1500 rockfalls). Various environmental variables such as slope, lithology, soil characteristics, land use, precipitation and seismic activity, were investigated for their significance in explaining the observed spatial patterns of landslides. To account for potential mapping biases in our dataset, we used Monte Carlo simulations that selected different subsets of mapped landslides, tested the significance of the considered environmental variables and evaluated the performance of the fitted multiple logistic regression model against another subset of mapped landslides. Based on these analyses, we constructed two landslide susceptibility maps for Africa: one for all landslide types and one excluding rockfalls. In both maps, topography, lithology and seismic activity were the most significant variables. The latter factor may be surprising, given the overall limited degree of seismicity in Africa. However, its significance indicates that frequent seismic events may serve as in important preparatory factor for landslides. This finding concurs with several other recent studies. Rainfall explains a significant, but limited part of the observed landslide pattern and becomes insignificant when also rockfalls are considered. This may be explained by the fact that a significant fraction of the mapped rockfalls occurred in the Sahara desert. Overall, both maps perform well in predicting intra-continental patterns of mass movements in Africa and explain about 80% of the observed variance in landslide occurrence. As a result, these maps may be a valuable tool for planning and risk reduction strategies. [less ▲]

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See detailLe marché du livre à Bruxelles au XVIe siècle
Adam, Renaud ULg

Conference (2017, April 28)

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See detailImplémentation du programme Lidcombe dans la prise en charge du bégaiement en clinique francophone
Leclercq, Anne-Lise ULg

Conference (2017, April 28)

This talk presents preliminary results of the Lidcombe program on French stuttering preschool children. The purpose is to discuss its effectiveness in regular clinical context, and with various profiles ... [more ▼]

This talk presents preliminary results of the Lidcombe program on French stuttering preschool children. The purpose is to discuss its effectiveness in regular clinical context, and with various profiles of children. [less ▲]

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See detailAgroforestry in temperate regions: where does the water go?   A case study with ERT in a corn field bordered by poplar trees.
MALOTEAU, Sophie ULg; Coussement, Tom; Pardon, Paul et al

Conference (2017, April 28)

Detailed reference viewed: 20 (1 ULg)