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See detailMulti-scale simulations of membrane active peptides: The fusion peptides
Crowet, Jean-Marc ULg

Scientific conference (2010, May 19)

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See detailMulti-scale spatial variability of amphipod assemblages from the foliar stratum of the Posidonia oceanica (L.) Delile meadow
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Michel, Loïc ULg et al

Conference (2008, October)

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation ... [more ▼]

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation. In the Mediterranean coastal zone, the Posidonia oceanica seagrass meadows constitute one of the dominant ecosystems and are an important habitat for vagile invertebrates. Among these, amphipods comprise a large number of species, with considerable abundance and biomass, as well as being an important trophic resource for fish populations. Until now, little attention has been given to the horizontal variability at different spatial scales of amphipod assemblages associated with P. oceanica meadows. A hierarchical sampling design, spanning three orders of magnitude (from 1 to 100s of metres) was elaborated. Sampling was undertaken in March 2007 in the meadows of Calvi Bay (NW Corsica), at depths ranging from 10 to 13 m, using a suction sampler. Our results indicated an important horizontal variability of the studied assemblage, and this at different spatial scales. In addition, these results tend to show that the small scale (~ 1 m and ~ 10 m) influenced abundance, while the medium-scale (~ 100 m) influenced diversity. Some potential causes of the observed patterns are discussed. These results emphasize the importance of considering different spatial scales in the study of the vagile invertebrates associated with P. oceanica meadows. [less ▲]

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See detailMulti-scale stochastic study of the grain orientation and roughness effects on polycrystalline thin structures
Lucas, Vincent ULg; Wu, Ling ULg; Golinval, Jean-Claude ULg et al

Conference (2016, June 09)

When studying micro-electro-mechanical systems (MEMS) made of poly-crystalline materials, as the size of the device is only one or two orders of magnitude higher than the size of the the grains, the ... [more ▼]

When studying micro-electro-mechanical systems (MEMS) made of poly-crystalline materials, as the size of the device is only one or two orders of magnitude higher than the size of the the grains, the structural properties exhibit a scatter at the macro-scale due to the existing randomness in the grain size, grain orientation, surface roughness... In order to predict the probabilistic behavior at the structural scale, the authors have recently developed a stochastic 3-scale approach [1]. In this method, stochastic volume elements (SVEs) [2] are defined by considering random grain orientations in a tessellation. For each SVE realization, a meso-scopic apparent material tensor can be obtained using the computational homogenization theory. The extracted meso-scopic apparent material tensors can then be used to defined a spatially correlated meso-scale random field, which is in turn used as input for stochastic finite element simulations. In this work we intend to study the effect of different material-related uncertainty sources on the structural behavior of vibrating micro-devices manufactured using low pressure chemical vapor deposition. First, the effect of preferred grain orientation on vibrating micro-structures is assessed. To this end, SVEs are generated so that their grain orientation distributions follow XRD measurements. Second, the effect of the roughness of the vibrating micro-structures is studied. Toward this end, SVEs, whose rough surface statistical properties follow AFM measurements, are generated. A second-order computational homogenization [3] applied on the different SVE realizations allows defining a meso-scale random field of the in-plane and out-of-plane meso-scale shell properties. Stochastic shell finite elements can then be applied to predict the MEMS probabilistic behavior. [1] V. Lucas, et al., Comp. Meth. in Appl. Mech. and Eng., 294, 141-167, 2015 [2] M. Ostoja-Starzewski, X.Wang, Comp. Meth. in Appl. Mech. and Eng., 168, 35–49, 1999 [3] E.W.C. Coenen, V. Kouznetsova, M.G.D. Geers. Int. J. for Numer. Meth. in Eng., 83, 1180–1205, 2010. [less ▲]

Detailed reference viewed: 35 (11 ULg)
Peer Reviewed
See detailA multi-scale strategy for the modelling of failure in masonry plates and shells
Massart, Thierry J.; Mercatoris, Benoît ULg; Diaby, Adama

Conference (2007)

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See detailMulti-scale studies of foamed materials
Nguyen, Van Dung ULg; Noels, Ludovic ULg

Conference (2013, September)

We propose a multi-scale study to predict micro-buckling that could happen in foamed materials. At the macroscopic scale, when localization occurs, the characteristic size of macroscopic deformation is ... [more ▼]

We propose a multi-scale study to predict micro-buckling that could happen in foamed materials. At the macroscopic scale, when localization occurs, the characteristic size of macroscopic deformation is the same order of the microscopic size. The assumption of material action in standard multi-scale computational homogenization approach where the stress only depends on the strain at this point is no-longer suitable, which motivates the uses of the second-order scheme. In this work, an implementation of the second-order continuum based on a discontinuous Galerkin approximation is shown to be particularly efficient to constrain weakly the continuities of the displacement field and of its gradient. At the microscopic scale, classical finite element resolutions of RVEs are considered. To enforce the periodic boundary condition of this micro problem, we propose an efficient method, which is based on the polynomial interpolation, and allows applying the periodic boundary condition without requiring conformal meshes. The micro-macro transition follows the second-order computational homogenization scheme. With the proposed framework it is shown that, during the macroscopic loading, the micro- buckling of the thin components of the foamed structure (cell walls and edges) can occur even if the tangent modulus of micro-material is still elliptic since the homogenized tangent modulus at macro-scale can lose its ellipticity. In that case, the localization occurs at macro- scale and can be captured by the model. [less ▲]

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See detailMulti-Sensor 3D Image Fusion: Technologies for an Urban Common Operating Picture
Waxman, Allen M.; Verly, Jacques ULg; Fay, David A.

Conference (2001, June)

Detailed reference viewed: 7 (0 ULg)
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See detailMulti-Sensor Image Fusion: 3-D Visualization and Search Agents
Waxman, Allen M.; Ross, William; Streilein, William et al

Conference (1999, October)

Detailed reference viewed: 7 (0 ULg)
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See detailMulti-Sensor Image Fusion: 3D Visualization and Search Agents
Waxman, Allen M.; Ross, William; Streilein, William et al

Conference (2000, June)

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See detailMulti-site quantitative ultrasound measurements of the third metacarpal bone in young thoroughbred horses
Carstanjen, B; Lepage, OM; Langlois, P et al

in Proceedings of the CESMAS congress 2002 (2002)

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See detailMulti-species measurements of nitrogen isotopic composition reveal the spatial constraints and biological drivers of ammonium attenuation across a highly contaminated groundwater system
Wells, Naomi S.; Hakoun, Vivien ULg; Brouyère, Serge ULg et al

in Water Research (2016), 98

Groundwater under industrial sites is characterised by heterogeneous chemical mixtures, making it difficult to assess the fate and transport of individual contaminants. Quantifying the in-situ biological ... [more ▼]

Groundwater under industrial sites is characterised by heterogeneous chemical mixtures, making it difficult to assess the fate and transport of individual contaminants. Quantifying the in-situ biological removal (attenuation) of nitrogen (N) is particularly difficult due to its reactivity and ubiquity. Here a multi-isotope approach is developed to distinguish N sources and sinks within groundwater affected by complex industrial pollution. Samples were collected from 70 wells across the two aquifers underlying a historic industrial area in Belgium. Below the industrial site the groundwater contained up to 1000 mg Nl-1 ammonium (NH4 +) and 300 mg N l-1 nitrate (NO3-), while downgradient concentrations decreased to ~1 mg l-1 DIN ([DIN] = [NH4+-N] + [NO3--N] + [NO2--N]). Mean δ1534 N-DIN increased from ~2‰ to +20‰ over this flow path, broadly confirming that biological N attenuation drove the measured concentration decrease. Multi-variate analysis of water chemistry identified two distinct NH4+ sources (δ15N-NH4+ from -14‰ and +5‰) within the contaminated zone of both aquifers. Nitrate dual isotopes co-varied (δ15 N: -3‰ - +60‰; δ18O: 0‰ - +50‰) within the range expected for coupled nitrification and denitrification of the identified sources. The fact that δ15N-NO2- values were 50‰ to 20‰ less than δ15N-NH4+ values in 40 the majority of wells confirmed that nitrification controlled N turnover across the site. However, the fact that δ15N-NO2- was greater than δ15N-NH4+ in wells with the highest [NH4+] shows that an autotrophic NO2- reduction pathway (anaerobic NH4+ oxidation or nitrifier-denitrification) drove N attenuation closest to the contaminant plume. This direct empirical evidence that both autotrophic and heterotrophic biogeochemical processes drive N attenuation in contaminated aquifers demonstrates the power of multiple N isotopes to untangle N cycling in highly complex systems. [less ▲]

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See detailA multi-step process for an alternative wheat bran biorefinery
Aguedo, Mario ULg; Fougnies, Christian; Richel, Aurore ULg

Poster (2014, May 21)

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See detailMulti-Step toolpath approach to overcome forming limitations in single point incremental forming
Verbert, J.; Belkassem, B.; Henrard, Christophe ULg et al

in Boisse, P. (Ed.) Proceedings of the 11th International ESAFORM Conference on Material Forming (2008)

Although Incremental Forming offers distinct advantages over traditional forming processes, such as short lead times and low setup costs, the process still has some drawbacks. Besides the obtainable ... [more ▼]

Although Incremental Forming offers distinct advantages over traditional forming processes, such as short lead times and low setup costs, the process still has some drawbacks. Besides the obtainable accuracy, one of the main challenges of the process are the process limits. Many workpiece geometries cannot be manufactured due to the fact that the maximum wall angle that can be formed is limited for a certain sheet material and thickness to a given angle. Different solutions to this approach have been proposed and this paper further investigates one of those solutions, the multi step approach for single point incremental forming. Experiments were performed and compared with simulations to better understand the phenomena underlying the improved process performance. [less ▲]

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See detailMulti-terminal HVDC systems and ancillary services
Ernst, Damien ULg

Speech/Talk (2012)

Detailed reference viewed: 14 (3 ULg)
See detailMulti-tracer constraints on ocean storage of anthropogenic CO2
Aumont, O.; Caldeira, K.; Campin, J. et al

Poster (2002, December 01)

During the second phase of the Ocean Carbon-Cycle Model Intercomparison, 13 models simulated oceanic uptake of anthropogenic CO2 for the period 1765 to 2000. For the 1980s, models agreed to within +/- 22 ... [more ▼]

During the second phase of the Ocean Carbon-Cycle Model Intercomparison, 13 models simulated oceanic uptake of anthropogenic CO2 for the period 1765 to 2000. For the 1980s, models agreed to within +/- 22% (1.99 +/- 0.43 Pg C yr-1, half the range over the mean). For the 1990s the OCMIP-2 models predict a 24% uptake increase (2.38 +/- 0.53 Pg C yr-1), in contrast with the 1980s-to-1990s decrease predicted by the most recent IPCC Third Assessment Report Chapter 3. However, the IPCC's estimates are based on atmospheric O2 measurements which are susceptible to error due to interannual variations in air-sea O2 fluxes. It appears likely that the OCMIP-2 range for the modern uptake of anthropogenic CO2 brackets real ocean uptake for four reasons: (1) the large model diversity; (2) the range of OCMIP-2 models bracket observed tracer constraints (CFC-11 along sections, global mean deep-ocean 14C); (3) the simulated global storage of anthropogenic CO2 correlates with the simulated global storage of CFC-11 and the simulated global-mean, deep-ocean natural C-14;(4) the simulated global inventories of anthropogenic CO2 bracket data-based estimates for that same tracer. In theory, the CFC-11 and C-14 data constraints should allow us to weight the models, and thus narrow uncertainties, based on how models perform in regards to matching ocean inventories of these independent tracers. Here we will discuss progress on this effort, in regards to global and regional inventories. [less ▲]

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See detailMulti-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France)
Goderniaux, Pascal ULg; Brouyère, Serge ULg; Gutierrez, Alexis et al

in Hydrogeology Journal (2010)

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize ... [more ▼]

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize a sandy aquifer that is affected by diffuse pollution (Brévilles spring catchment, Val d'Oise, France), and to quantify the transfer time in the saturated zone, a multi-tracer test involving a new technique, the ‘Finite Volume Point Dilution Method’, has been performed in natural flow conditions. In November 2005, injections of four different tracers took place in four piezometers involving different locations and depths in the aquifer. Recovery of the tracers was observed at two different places near the aquifer outlet. A particularly long and unusual monitoring exercise (27 months) demonstrated the existence of several different velocities within the sandy layer, which seems to be linked to the decrease of hydraulic conductivity with depth. The new insight and parameter quantification brought by interpretation of these tests contribute to a better characterization of the saturated zone. The particularly long-term monitoring exercise also gives new information to understand and forecast the trend and persistence of groundwater contamination by pesticides in the catchment. [less ▲]

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See detailMulti-trait animal model estimation of genetic parameters for linear type and gait traits in the Belgian warmblood horse
Rustin, M.; Janssens, S.; Buys, N. et al

in Journal of Animal Breeding & Genetics (2009), 126(5), 378--386

Summary Genetic parameters for the height at withers, 27 linear type and six linear gait traits were estimated for the Belgian warmblood horse. Observations on 987 mares, mostly 3 years old, were analysed ... [more ▼]

Summary Genetic parameters for the height at withers, 27 linear type and six linear gait traits were estimated for the Belgian warmblood horse. Observations on 987 mares, mostly 3 years old, were analysed using a multi-trait animal model. The statistical model included appraiser, age and location (date × place of appraisal) as fixed effects. Genetic parameters were estimated using a canonical transformation and an expectation-maximization restricted maximum likelihood algorithm with an additional deceleration step. Estimates of heritability for the 33 linear traits were between 0.15 and 0.55. Heritability of the height at withers was 0.34 ± 0.06. Estimated genetic correlations ranged from −0.60 to 0.98 with an average SE of 0.10. The highest positive correlations were found among traits of walk and among traits of trot. Volume and the quality of legs were the most negatively correlated. Estimated genetic parameters indicated that the linear scoring system is a valuable tool to assess conformation. The full (co)variance matrix is now available for breeding value estimation to support selection for conformation and gaits. [less ▲]

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See detailMulti-view object tracking using sequential belief propagation
Du, Wei ULg; Piater, Justus ULg

in Computer Vision – ACCV 2006 (2006)

Multiple cameras and collaboration between them make possible the integration of information available from multiple views and reduce the uncertainty due to occlusions. This paper presents a novel method ... [more ▼]

Multiple cameras and collaboration between them make possible the integration of information available from multiple views and reduce the uncertainty due to occlusions. This paper presents a novel method for integrating and tracking multi-view observations using bidirectional belief propagation. The method is based on a fully connected graphical model where target states at different views are represented as different but correlated random variables, and image observations at a given view are only associated with the target states at the same view. The tracking processes at different views collaborate with each other by exchanging information using a message passing scheme, which largely avoids propagating wrong information. An efficient sequential belief propagation algorithm is adopted to perform the collaboration and to infer the multi-view target states. We demonstrate the effectiveness of our method on video-surveillance sequences. [less ▲]

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See detailMulti-walled nanotubes diameter distribution by image analysis
Gommes, Cédric ULg; BLACHER, Silvia ULg; Bossuot, Christophe ULg et al

Scientific conference (2002, February)

Detailed reference viewed: 16 (2 ULg)