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See detailInversion of Venus NO nightglow limb profiles
Stiepen, Arnaud ULg; Soret, Lauriane ULg; Gérard, Jean-Claude ULg et al

Conference (2012, July)

Detailed reference viewed: 19 (9 ULg)
See detailInversions Estrangeres Directes i Innovació a Catalunya
Artige, Lionel ULg; Nicolini, Rosella

in Busom, Isabel (Ed.) La situació de la innovació a Catalunya (2006)

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See detailLes invertébrés des carrières souterraines de craie de la Montagne Saint-Pierre (Province de Liège, Belgique). Note préliminaire
Dethier, Michel; Willems, Luc ULg

in Notes Fauniques de Gembloux (2005), 57

During the 1930’s, Leruth collected 145 species in the underground chalk quarries at the Montagne Saint-Pierre. None was troglobitic. To evaluate the biological interest of the sites and the faunal drift ... [more ▼]

During the 1930’s, Leruth collected 145 species in the underground chalk quarries at the Montagne Saint-Pierre. None was troglobitic. To evaluate the biological interest of the sites and the faunal drift 70 years after, we have undertaken in 2004 a new faunistic survey. [less ▲]

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See detailInverted patterns of genetic diversity in continental and island populations of the heather Erica scoparia s.l.
Desamore, Aurélie ULg; Laenen, Benjamin ULg; González-Mancebo, JM et al

in Journal of Biogeography (2012), 39(3), 574--584

Aim  Using the heather Erica scoparia s.l. as a model, this paper aims to test theoretical predictions that island populations are genetically less diverse than continental ones and to determine the ... [more ▼]

Aim  Using the heather Erica scoparia s.l. as a model, this paper aims to test theoretical predictions that island populations are genetically less diverse than continental ones and to determine the extent to which island and continental populations are connected by pollen- and seed-mediated gene flow.Location  Macaronesia, Mediterranean, Atlantic fringe of Europe.Methods  Patterns of genetic diversity are described based on variation at two chloroplast DNA (cpDNA) loci and one nuclear DNA (nDNA) locus for 109 accessions across the entire distribution range of the species. Global patterns of genetic differentiation were investigated using principal coordinates analysis. Genetic differentiation between island and continental areas, estimations of pollen- and seed-mediated gene flow, and the presence of phylogeographical signal were assessed by means of Fst/NST (continental scale) and Fij/Nij (local scale). Extant and past distribution ranges of the species were inferred from niche modelling using layers describing present and Last Glacial Maximum (LGM) macroclimatic conditions.Results  The Azores exhibited a significantly higher genetic diversity than the continent. The lowest levels of genetic differentiation were observed between the Azores and the western Mediterranean, and the diversity observed in the Azores resulted from at least two colonization waves. Within the Azores, kinship coefficients showed a significant and much steeper decrease with geographical distance in the cpDNA than in the nDNA. The distribution predicted by LGM models was markedly different from the current potential distribution, particularly in western Europe, where no suitable areas were predicted by LGM models, and along the Atlantic coast of the African continent, where LGM models predicted highly suitable climatic conditions.Main conclusions  The higher diversity observed in Azorean than in continental populations is inconsistent with MacArthur and Wilson’s equilibrium model and derived theoretical population genetic expectations. This inverted pattern may be the result of extinction on the continent coupled with multiple island colonization events and subsequent allopatric diversification and lineage hybridization in the Azores. The results highlight the role of allopatric diversification in explaining diversification on islands and suggest that this process has played a much more significant role in shaping Azorean biodiversity than previously thought. [less ▲]

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See detailInverting Hydraulic Heads In An Alluvial Aquifer Constrained With Electrical Resistivity Tomography Data Through Multiple-Point Statistics And Probability Perturbation Method: A Case Study
Hermans, Thomas ULg; Scheidt, Celine; Caers, Jef et al

Conference (2014, July)

Solving spatial inverse problems in the Earth Sciences remains a considerable challenge given the large number of parameters to invert for, the non-linearity of forward models and as a result the ill ... [more ▼]

Solving spatial inverse problems in the Earth Sciences remains a considerable challenge given the large number of parameters to invert for, the non-linearity of forward models and as a result the ill-posedness of the problem. Geostatistics is therefore needed to specify prior models, more particularly, information to control the spatial features of the inverse solutions. We used multiple-point statistics (MPS) to build models of pre-defined hydrofacies: clay, sand and gravel facies constrained to geological data (hard data) and geophysical data (soft data). The electrical resistivity tomography method was chosen to bring relevant spatially distributed information on the presence of the facies, given its sensitivity to variations in lithology and porosity. The comparison of the geophysical signature of the deposits with direct observations in boreholes enables to derive the conditional probability of observing a facies given its electrical resistivity. This is used to produce probability maps for each facies and constrain stochastic simulations of the alluvial aquifer. Then, the probability perturbation method (PPM) is used to integrate hydraulic heads data, using MPS to generate models. This process enables us to obtain calibrated models of the aquifer. The PPM algorithm will automatically seek solutions fitting both hydrogeological data and training-image based geostatistical constraints. Only geometrical features of the model are affected by the perturbation, i.e. we do not attempt to directly find the optimal value of hydrogeological parameters (chosen a priori), but the optimal spatial distribution of facies whose prior distribution is quantified in a training image. The methodology is first tested with a synthetic benchmark. The tests performed show that the choice of the training image is a major source of uncertainty. Therefore, one first needs to select those training images consistent with the geophysical data (and hence reject the inconsistent ones). Then, we proceed with them to hydrogeological inversions. Geophysical data (soft constraints) acts as an accelerator of convergence by reducing prior uncertainty. The hydraulic conductivity of each facies is a sensitive parameter, but it can be easily optimized prior to the PPM process. The stochastic method is then successfully applied within the context of an alluvial aquifer submitted to a pumping experiment. We show how the integration of various sources of data (borehole logs, geophysics, hydraulic heads) aids in calibrating hydrogeological models, locating high hydraulic conductivity zones and reducing uncertainty. The developed methodology proposes a common framework (multiple-point statistics) to integrate various information sources with variable resolutions relevant for hydrogeology: geological, geophysical and hydrogeological data. The method can be extended to integrate tracer tests to enable the calibration of transport parameters as well. The originality of the method is to use geophysical data both to refine the choice of the training image and to constrain the inversion of hydrogeological models. [less ▲]

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See detailA Investigacao Sociologica os "pragamatic" americanos
Stassart, Pierre M ULg

Scientific conference (2011)

Detailed reference viewed: 12 (0 ULg)
See detailLa investigación experimental en educación
De Landsheere, Gilbert ULg

Book published by UNESCO (1982)

Detailed reference viewed: 79 (3 ULg)
See detailLa investigación pedagógica
de Landsheere, Gilbert ULg; Mialaret, Gaston

Book published by Angel Estrada - 1ère éd. (1971)

Detailed reference viewed: 10 (0 ULg)
See detailInvestigación y Desarrollo más Innovación
Artige, Lionel ULg; Nicolini, Rosella

Book published by Consejo Económico y Social de España (2008)

Detailed reference viewed: 30 (5 ULg)
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See detailInvestigaciones sobre el aceite de Mauritia flexuosa L.
Lognay, Georges ULg; Trevejo, E.; Jordan, E. et al

in Grasas Y Aceites (1987), 38(5), 303-307

Detailed reference viewed: 14 (0 ULg)
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See detailInvestigating a bottom-up approach for extracting domain ontologies from urban databases
Chaidron, Christophe; Teller, Jacques ULg; Billen, Roland ULg

in Proceedings of the 1st Workshop of COST Action C21 Towntology (2006)

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See detailInvestigating a Bottom-up Approach for Extracting Ontologies from Urban Databases
Chaidron, Christophe; Billen, Roland ULg; Teller, Jacques ULg

in Teller, Jacques; Lee, John; Roussey, Catherine (Eds.) Ontologies for Urban Development (2007)

Detailed reference viewed: 51 (9 ULg)
See detailInvestigating a two-level dynamic estimation algorithm for large-scale electric power systems
Rousseaux, Patricia ULg; Van Cutsem, Thierry ULg; Ribbens-Pavella, Mania

in Proceedings of the 1st European Workshop on the Real Time Control of Large Scale Systems (1984)

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See detailInvestigating apical adverse effects of four endocrine active substances in the freshwater gastropod Lymnaea stagnalis
Giusti, Arnaud ULg; Lagadic, Laurent; Barsi, Alpar et al

in Science of the Total Environment (2014), 493

The hermaphroditic gastropod Lymnaea stagnalis is proposed as a candidate species for the development of OECD guidelines for testing of the reprotoxicity of chemicals, including endocrine active ... [more ▼]

The hermaphroditic gastropod Lymnaea stagnalis is proposed as a candidate species for the development of OECD guidelines for testing of the reprotoxicity of chemicals, including endocrine active substances (EASs). Up to now, only a few putative EASs have been tested for their reproductive toxicity in this species. In this study, we investigate the effects of four EASs with different affinities to the vertebrate estrogen and androgen receptors (chlordecone as an estrogen; cyproterone acetate, fenitrothion and vinclozolin as anti-androgens) on the reproduction of L. stagnalis in a 21-day semi-static test. Testosterone and 17α-ethinylestradiol (EE2) were used as the reference compounds. The tested EASs had no significant effect on growth and survival at the tested concentration ranges (ng to μg/L). Classical reproduction endpoints (i.e., oviposition and fecundity) were not responsive to the tested chemicals, except for chlordecone and 17α-ethinylestradiol, which hampered reproduction from 19.6 μg/L and 17.6 μg/L, respectively. The frequency of polyembryonic eggs, used as an additional endpoint, demonstrated the effects of all compounds except EE2. The molecular pathways, which are involved in such reproduction impairments, remain unknown. Our results suggest that egg quality is a more sensitive endpoint as compared to other reproductive endpoints commonly assessed in mollusk toxicity tests. [less ▲]

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See detailInvestigating Circumferential Non-Uniformities in Throughflow Calculations using an Harmonic Reconstruction
Thomas, Jean-Philippe ULg; Léonard, Olivier ULg

in Proceedings of the ASME Turbo Expo 2008 (2008, June)

The flow field in a multistage turbomachine is very complex. It is 3D, unsteady and turbulent. Even if modern simulation tools can describe most of the flow features, the computation time needed and the ... [more ▼]

The flow field in a multistage turbomachine is very complex. It is 3D, unsteady and turbulent. Even if modern simulation tools can describe most of the flow features, the computation time needed and the extraction of useful information remain severe drawbacks to systematic use of URANS codes in a design procedure. In this context the throughflow simulation proved to be more convenient. Nevertheless the need for empiricism limits the potential of throughflow solvers. As an alternative, Admaczyck (1984) proposed three averaging operators (ensemble, time and passage) that lead to the average-passage model, linking the unsteady turbulent flow field to a steady flow field in a typical blade passage. This model involves additional terms that respectively bring back the mean effect of turbulence, deterministic unsteadiness and aperiodicity on the mean periodic flow. These terms need to be modelled; it is the closure problem. Harmonic closure, which consists in solving a linearized perturbation system in the frequency domain, revealed to be an efficient method to approximate deterministic stresses (He and Ning, 1998, Stridh, 2005, Vilmin, 2006). A fourth averaging can be performed, a circumferential averaging, giving rise to the throughflow model. Additional terms appear: the so-called circumferential stresses. It has been proven that these terms play an important role in the description of the flow (Jennions, 1986, Perrin, 1995), being at least as considerable as deterministic stresses. Introducing these terms in a throughflow simulation allows to reproduce the averaged 3D steady flow field (Simon, 2007). The aim of the present contribution is to prove that harmonic method can potentially be used to reconstruct circumferential stresses. The importance of circumferential stresses in a throughflow simulation is first highlighted on a single stage low speed compressor testcase, for viscous and non-viscous flow fields. The second step is the characterization of the frequency spectrum of the circumferential perturbation field. Next are compared the stresses associated to a Fourier reconstruction of the perturbation field with the real ones. Finally the approximated circumferential stresses are injected into a throughflow simulation tool to analyse and demonstrate their capability to reproduce a 3D averaged flow field. [less ▲]

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See detailInvestigating Depth-Fanout Trade-Off in WiMAX Mesh Networks
Nahle, Salim; Iannone, Luigi; Donnet, Benoît ULg et al

in 1st WEIRD Workshop on WiMAX, Wireless and Mobility (2007, May)

In the last years, Wireless Mesh Networks (WMNs) have been an emerging technology for providing cost/effective broadband Internet access. The research done insofar usually assumes that the wireless ... [more ▼]

In the last years, Wireless Mesh Networks (WMNs) have been an emerging technology for providing cost/effective broadband Internet access. The research done insofar usually assumes that the wireless backbone of a WMN is built using IEEE 802.11 technologies. Such an approach has the drawback of leading to dense and sub-optimal deployments, due to the short transmission range of this standard. Recently standardized, the WiMAX technology is supposed to transcend this limitation by a transmission range of several miles. In particular, the mesh mode of the WiMAX standard enables direct communications between subscriber stations and, hence, reduces dead zones while increasing the global throughput. In this paper, we investigate the throughput capacity of a WiMAX mesh tree. More specifically, we are interested in balancing the impact of the depth of the tree with its fanout. We provide a traffic model and evaluate the WiMAX mesh tree by simulations. [less ▲]

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See detailInvestigating Effect of Holidays on Daily Traffic Counts: Time Series Approach
Cools, Mario ULg; Moons, Elke; Wets, Geert

in Transportation Research Record: Journal of the Transportation Research Board (2007), 2019

In this paper, different modeling philosophies are explored in order to explain and forecast daily traffic counts. The main objectives of this study are the analysis of the impact of holidays on daily ... [more ▼]

In this paper, different modeling philosophies are explored in order to explain and forecast daily traffic counts. The main objectives of this study are the analysis of the impact of holidays on daily traffic, and the forecasting of future traffic counts. Data coming from single inductive loop detectors, collected in 2003, 2004 and 2005, were used for the analysis. The different models that were investigated showed that the variation in daily traffic counts could be explained by weekly cycles. The Box-Tiao modeling approach was applied to quantify the effect of holidays on daily traffic. The results showed that traffic counts were significantly lower for holiday periods. When the different modeling techniques were compared with respect to forecasting with a large forecast horizon, Box-Tiao modeling clearly outperformed the other modeling strategies. Simultaneous modeling of both the underlying reasons of travel, and revealed traffic patterns, certainly is a challenge for further research. [less ▲]

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See detailInvestigating Effect of Holidays on Daily Traffic Counts: Time Series Approach
Cools, Mario ULg; Moons, Elke; Wets, Geert

in Proceedings of the 86th Annual Meeting of the Transportation Research Board (CD-ROM) (2007)

In this paper, different modeling philosophies are explored in order to explain and forecast daily traffic counts. The main objectives of this study are the analysis of the impact of holidays on daily ... [more ▼]

In this paper, different modeling philosophies are explored in order to explain and forecast daily traffic counts. The main objectives of this study are the analysis of the impact of holidays on daily traffic, and the forecasting of future traffic counts. Data coming from single inductive loop detectors, collected in 2003, 2004 and 2005, were used for the analysis. The different models that were investigated showed that the variation in daily traffic counts could be explained by weekly cycles. The Box-Tiao modeling approach was applied to quantify the effect of holidays on daily traffic. The results showed that traffic counts were significantly lower for holiday periods. When the different modeling techniques were compared with respect to forecasting with a large forecast horizon, Box-Tiao modeling clearly outperformed the other modeling strategies. Simultaneous modeling of both the underlying reasons of travel, and revealed traffic patterns, certainly is a challenge for further research. [less ▲]

Detailed reference viewed: 23 (2 ULg)
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See detailInvestigating Expertise, Flexibility and Resilience in Socio-technical Environments : A Case Study in Robotic Surgery.
Nyssen, Anne-Sophie ULg; Blavier, Adelaïde ULg

in Hollnagel, Erik; Braithwaite, Jeffrey; Wears, Robert (Eds.) Resilient Health Care (2013)

Detailed reference viewed: 26 (6 ULg)