Last 7 days
Bookmark and Share    
Full Text
Peer Reviewed
See detailComparing photogrammetry and laser scanning: a 3D reconstruction of the Castle of Penne
Novel, Cyril; Keriven, Renaud; Poux, Florent ULg et al

Conference (2015, November 25)

In the last decade, the progress in computing power – both CPU and GPU – has allowed the development of photogrammetry softwares. These softwares can turned a set of photos of an object – such as a ... [more ▼]

In the last decade, the progress in computing power – both CPU and GPU – has allowed the development of photogrammetry softwares. These softwares can turned a set of photos of an object – such as a building – into a 3D model. They compete with laser scanners which are usually used for scanning objects like buildings and landmarks. In this paper, we compare outcomes of the software Smart3DCapture[4] with laser scanner point clouds of various scenes in order to evaluate the accuracy of photogrammetry reconstruction [less ▲]

Detailed reference viewed: 27 (0 ULg)
Full Text
See detail25 novembre 2015 : cent ans de Relativité
De Rop, Yves ULg

E-print/Working paper (2015)

La théorie proposée par Einstein au début du XXe siècle porte bien mal son nom; car si, historiquement, l'accent fut mis d'abord sur la relativité de certaines notions (en particulier, la mesure de l ... [more ▼]

La théorie proposée par Einstein au début du XXe siècle porte bien mal son nom; car si, historiquement, l'accent fut mis d'abord sur la relativité de certaines notions (en particulier, la mesure de l'intervalle de temps écoulé entre deux événements donnés), on a compris par la suite qu'elle reposait plus fondamentalement sur l'existence de quantités absolues, c'est-à-dire, dont la mesure est identique pour tous les observateurs, quel que soit leur état de repos ou de mouvement. Ces quantités sont inconnues de la mécanique de Newton, laquelle ne reconnaît qu'un seul invariant : le temps. Ce texte cherche à retracer, avec un minimum de formalisme, comment s'est imposé un nouveau cadre géométrique pour la physique, dominé par cette exigence d'invariance des mesures spatio-temporelles et intégrant une description révolutionnaire de la gravitation. [less ▲]

Detailed reference viewed: 56 (10 ULg)
See detailOptional Sage package slabbe-0.2.spkg
Labbé, Sébastien ULg

Software (2015)

Detailed reference viewed: 7 (0 ULg)
Full Text
See detailÉconomie sociale et fiscalité: état des lieux et perspectives
Garroy, Sabine ULg

Conference (2015, November 25)

Detailed reference viewed: 20 (1 ULg)
Full Text
See detailRamses: An annotated corpus of Late Egyptian texts. Background information, recent developments and work in progress
Polis, Stéphane ULg

Scientific conference (2015, November 25)

Background information about the Ramses project and Ramses Online (http://ramses.ulg.ac.be) with a special attention to recent developments that are relevant for digital humanities in general: event ... [more ▼]

Background information about the Ramses project and Ramses Online (http://ramses.ulg.ac.be) with a special attention to recent developments that are relevant for digital humanities in general: event sourcing, TEI interchange format, ontologies and metadata thesauri, linked data. [less ▲]

Detailed reference viewed: 27 (3 ULg)
Full Text
See detailL'empreinte carbone mine-t-elle nos héros ?
Ozer, Pierre ULg

Article for general public (2015)

Nous avons établi un classement, certifié sans aucune valeur scientifique, de dix personnages populaires. Du plus écolo au plus polluant.

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailRecent advances in BLV research
Barez, Pierre-Yves ULg; De Brogniez, Alix ULg; Carpentier, Alexandre ULg et al

in Viruses (2015), 7(11), 6080-6088

Different animal models have been proposed to investigate the mechanisms of HTLV-induced pathogenesis: rats, transgenic and NOD-SCID/γcnull (NOG) mice, rabbits, squirrel monkeys, baboons and macaques ... [more ▼]

Different animal models have been proposed to investigate the mechanisms of HTLV-induced pathogenesis: rats, transgenic and NOD-SCID/γcnull (NOG) mice, rabbits, squirrel monkeys, baboons and macaques. These systems indeed provide useful information but have intrinsic limitations such as lack of disease relevance, species specificity or inadequate immune response. Another strategy based on a comparative virology approach is to characterize a related pathogen and to speculate on possible shared mechanisms. In this perspective, bovine leukemia virus (BLV), another member of the deltaretrovirus genus, is evolutionary related to HTLV-1. BLV induces lymphoproliferative disorders in ruminants providing useful information on the mechanisms of viral persistence, genetic determinants of pathogenesis and potential novel therapies. [less ▲]

Detailed reference viewed: 30 (8 ULg)
Full Text
See detailAtelier Paralysie faciale
WANG, François-Charles ULg

Scientific conference (2015, November 24)

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailA Lightweight Network Proximity Service Based On Neighborhood Models
Liao, Yongjun; Du, Wei; Leduc, Guy ULg

in 22nd IEEE Symposium on Communications and Vehicular Technology in the Benelux (SCVT) (2015, November 24)

This paper proposes a network proximity service based on the neighborhood models used in recommender systems. Unlike previous approaches, our service infers network proximity without trying to recover the ... [more ▼]

This paper proposes a network proximity service based on the neighborhood models used in recommender systems. Unlike previous approaches, our service infers network proximity without trying to recover the latency between network nodes. By asking each node to probe a number of landmark nodes which can be servers at Google, Yahoo and Facebook, etc., a simple proximity measure is computed and allows the direct ranking and rating of network nodes by their proximity to a target node. The service is thus lightweight and can be easily deployed in e.g. P2P and CDN applications. Simulations on existing datasets and experiments with a deployment over PlanetLab showed that our service achieves an accurate proximity inference that is comparable to state-of-the-art latency prediction approaches, while being much simpler. [less ▲]

Detailed reference viewed: 31 (2 ULg)
See detailLa personnalité antisociale ? Antipode d'une réflexion psychopathologique
Englebert, Jérôme ULg

Scientific conference (2015, November 24)

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailDiscrimination of deciduous tree species from time series of unmanned aerial system imagery
Lisein, Jonathan ULg; Michez, Adrien ULg; Claessens, Hugues ULg et al

in PLoS ONE (2015), 10(11),

Technology advances can revolutionize Precision Forestry by providing accurate and fine forest information at tree level. This paper addresses the question of how and particularly when Unmanned Aerial ... [more ▼]

Technology advances can revolutionize Precision Forestry by providing accurate and fine forest information at tree level. This paper addresses the question of how and particularly when Unmanned Aerial System (UAS) should be used in order to efficiently discriminate deciduous tree species. A time series of high resolution UAS imagery was collected to cover the growing season from leaf flush to leaf fall. Full benefit was taken of the temporal resolution of UAS acquisition, one of the most promising features of small drones. The disparity in forest tree phenology is at the maximum during early spring and late autumn. But the phenology state that optimized the classification result is the one that minimizes the spectral variation within tree species groups and, at the same time, maximizes the phenologic differences between species. Sunlit tree crowns (5 deciduous species groups) were classified using a Random Forest approach for monotemporal, two-date and three-date combinations. The end of leaf flushing was the most efficient single-date time window. Multitemporal datasets definitely improve the overall classification accuracy. But single-date high resolution orthophotomosaics, acquired on optimal time-windows, result in a very good classification accuracy (overall out of bag error of 16%). [less ▲]

Detailed reference viewed: 101 (45 ULg)
Full Text
See detailComment réduire l'impact environnemental pour le transport de marchandises ?
Limbourg, Sabine ULg

Conference given outside the academic context (2015)

Avec l'internationalisation des activités économiques, la demande de transport a considérablement augmenté suite à l’allongement des distances et à la multiplication des fréquences d’envois. Pour répondre ... [more ▼]

Avec l'internationalisation des activités économiques, la demande de transport a considérablement augmenté suite à l’allongement des distances et à la multiplication des fréquences d’envois. Pour répondre aux exigences du e-commerce et des livraisons à domicile, de nouveaux schémas logistiques sont indispensables. Ces défis doivent être relevés tout en minimisant les nuisances environnementales. A l'occasion de ce lunch-conférence, Sabine Limbourg exposera le résultat de ses recherches, basées sur des méthodes quantitatives, explorant trois options permettant de réduire l'impact environnemental pour le transport des marchandises. Ces options sont le transport intermodal qui combine efficacement plusieurs modes de transport, l'intégration de véhicules électriques en milieu urbain et le partage de ressources de transport réutilisables qui circulent en boucle entre les acteurs d’une chaîne logistique. [less ▲]

Detailed reference viewed: 26 (5 ULg)
Full Text
See detailTime-lapse inversion of ERT monitoring data using variogram-based regularization
Hermans, Thomas ULg; Dumont, Gaël ULg; Kemna, Andreas et al

Conference (2015, November 24)

Hydrogeophysics has become a major field of research in the past two decades and time-lapse electrical resistivity tomography (ERT) is one of the most popular techniques to monitor passive and active ... [more ▼]

Hydrogeophysics has become a major field of research in the past two decades and time-lapse electrical resistivity tomography (ERT) is one of the most popular techniques to monitor passive and active processes in subsurface reservoirs. Time-lapse inversion schemes have been developed to refine inversion results; but, in contrast with static inversion, they mostly still rely on the spatial regularization procedure based on the standard smoothness constraint. In this contribution, we propose to apply a variogram-based regularization operator in the time-lapse ERT inverse problem, using the model difference covariance matrix to replace the standard smoothing operator. The variogram of resistivity variations can be computed through independent borehole data, such as electromagnetic logs or hydrogeological monitoring, which is often available during monitoring experiments. We first illustrate the method for surface ERT with a synthetic case and compare the results with the standard smoothness constraint solution. This example shows that the variogram-based constraint images better the assumed anomaly both in terms of shape and amplitude. The improvement is largely higher than the one obtained with more classical anisotropic smoothness constraint. This synthetic example also shows that an error made in the range of the variogram has a limited impact on the resulting image, which still remains better than the smoothness constraint result. Anomalies located in various part of the tomograms were tested. Although more crucial in low-sensitivity zones, improvements are observed everywhere in the tomograms. The method is then applied to cross-borehole ERT field data from a heat tracing experiment, where the comparison with direct temperature measurements shows a strong improvement of the breakthrough curves retrieved from ERT. Using the variogram-based regularization, it is possible to reduce the smoothing of resistivity variations in low sensitivity zones and therefore to avoid overestimation of temperatures. The proposed method could be extended to the time dimension which would allow the use of variogram-based constraints in 4D inversion schemes. [less ▲]

Detailed reference viewed: 32 (1 ULg)
Full Text
Peer Reviewed
See detailPost-coronagraphic tip-tilt sensing for vortex phase masks: the QACITS technique
Huby, Elsa ULg; Baudoz, Pierre; Mawet, Dimitri et al

in Astronomy and Astrophysics (2015), 584

Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization ... [more ▼]

Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization. However, the drawback of this attractive feature is a high sensitivity to pointing errors, which degrades the performance of the coronagraph. We propose a tip-tilt retrieval technique based on the analysis of the final coronagraphic image, hereafter called Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing (QACITS). Under the assumption of small phase aberrations, we show that the behaviour of the vortex phase mask can be simply described from the entrance pupil to the Lyot stop plane by Zernike polynomials. This convenient formalism is used to establish the theoretical basis of the QACITS technique. Simulations have been performed to demonstrate the validity and limits of the technique, including the case of a centrally obstructed pupil. The QACITS technique principle is further validated by experimental results in the case of an unobstructed circular aperture. The typical configuration of the Keck telescope (24% central obstruction) has been simulated with additional high order aberrations. In these conditions, our simulations show that the QACITS technique is still adapted to centrally obstructed pupils and performs tip-tilt retrieval with a precision of $5 \times 10^{-2}$ {\lambda}/D when wavefront errors amount to {\lambda}/14 rms and $10^{-2}$ {\lambda}/D for {\lambda}/70 rms errors (with {\lambda} the wavelength and D the pupil diameter). The implementation of the QACITS technique is based on the analysis of the scientific image and does not require any modification of the original setup. Current facilities equipped with a vortex phase mask can thus directly benefit from this technique to improve the contrast performance close to the axis. [less ▲]

Detailed reference viewed: 17 (4 ULg)
Full Text
Peer Reviewed
See detailCaractérisation des propriétés hydrauliques de sols caillouteux
Pichault, Mathieu; Garré, Sarah ULg

Conference (2015, November 24)

La détermination des propriétés hydrauliques du sol est une préoccupation majeure dans différents domaines d’études. Bien que les sols caillouteux soient répandus dans le monde entier, la plupart des ... [more ▼]

La détermination des propriétés hydrauliques du sol est une préoccupation majeure dans différents domaines d’études. Bien que les sols caillouteux soient répandus dans le monde entier, la plupart des études ne caractérisent que la fraction fine des sols, si bien que la littérature décrivant l’impact des cailloux sur les propriétés hydrauliques du sol est encore rare. Certains modèles ayant pour but de caractériser ces propriétés hydrauliques reposent sur la même hypothèse simplificatrice, qui stipule que le seul effet des cailloux est de diminuer le volume disponible pour l’écoulement de l’eau. L’objectif de cette étude est de vérifier cette hypothèse et, le cas échéant, d’identifier les facteurs déterminant ou non son respect. L’effet des cailloux sur la conductivité hydraulique à saturation effective du sol a été testé au moyen d’expériences de laboratoire et d’expériences numériques, impliquant différentes quantités et types de fragments grossiers. Nos résultats montrent que plusieurs facteurs supplémentaires, non considérés par ces modèles, peuvent affecter significativement la conductivité hydraulique à saturation. D’une part, la forme et la taille des inclusions altèrent de manière substantielle la conductivité hydraulique. D’autre part, la présence de cailloux peut contrer -voire dominer- les effets liés à la réduction du volume disponible pour l’écoulement en conditions saturantes. Nous attribuons cela à la création de macropores à l’interface entre la terre fine et les cailloux. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
See detailCurrent issues in the processing of Ti alloy Ti6Al4V by laser additive manufacturing techniques
Mertens, Anne ULg

Learning material (2015)

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Advanced Manufacturing technologies” at Université catholique de Louvain. It outlines important current ... [more ▼]

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Advanced Manufacturing technologies” at Université catholique de Louvain. It outlines important current issues in the development of additive technologies for the processing of metallic materials in general, and particularly of Ti alloy Ti-6Al-4V. This includes issues related to the dimensional accuracy of the produced components, as well as the control of their microstructures and usage properties. [less ▲]

Detailed reference viewed: 48 (8 ULg)
Full Text
Peer Reviewed
See detailMultimedia-enhanced learning productions - A typology based on instructional use and needed resources
Van de Poël, Jean-François ULg; Martin, Pierre; Verpoorten, Dominique ULg

Poster (2015, November 24)

This poster introduces a typology of educational multimedia objects stemming from an analysis of 400 audiovisual items produced by IFRES-eCampus, the staff development unit of the University of Liège ... [more ▼]

This poster introduces a typology of educational multimedia objects stemming from an analysis of 400 audiovisual items produced by IFRES-eCampus, the staff development unit of the University of Liège (Belgium). The classification of the multimedia productions is based on their instructional use and is enriched by additional qualifications in terms of time investment by the faculty and the Teaching and Learning center. [less ▲]

Detailed reference viewed: 15 (4 ULg)