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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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See detailDes processus de (dé)subjectivation dans l’activisme associatif: enquête ethnographique au sein du mouvement belge "Inclusion"
Borotto, Jessica ULg; Duysens, Fanny ULg

Conference (2015, November 24)

L’activisme associatif dans le domaine de la déficience intellectuelle a connu des évolutions significatives depuis quelques décennies. Suivant les principes fondateurs de la Convention des Nations Unies ... [more ▼]

L’activisme associatif dans le domaine de la déficience intellectuelle a connu des évolutions significatives depuis quelques décennies. Suivant les principes fondateurs de la Convention des Nations Unies relative aux droits des personnes handicapées (2006), les associations de personnes concernées revendiquent leur légitimité à s’impliquer activement dans la gouvernance des questions qui les concernent. Cette communication porte sur les manières dont de jeunes adultes dits porteurs de déficience intellectuelle sont sujets à des processus de subjectivation et de désubjectivation au travers de discours et pratiques associatives qui revendiquent leur pleine inclusion et participation à la société. Croisant nos recherches respectives en sciences sociales et en philosophie politique, nous mobilisons une approche du sujet observé en situation (Agier, 2012) en vue d'envisager des « scènes de subjectivation » formelles et informelles dans le cadre d'une association belge francophone, en ce qu’elles nous semblent effectivement donner à voir de telles dynamiques de (dé)subjectivation par lesquelles se (re)construisent constamment les sujets porteurs de déficience intellectuelle et leur capacité d’agir. [less ▲]

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See detailPanorama du Nouveau Cinéma Allemand: entre esthétique et politique.
Hamers, Jérémy ULg

Scientific conference (2015, November 23)

Detailed reference viewed: 13 (0 ULg)
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See detailThe mysterious droplet birth in a microfluidic cross junction
Van Loo, Stéphanie ULg; Gilet, Tristan ULg

Conference (2015, November 23)

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could ... [more ▼]

In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics. [less ▲]

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See detailContinuer à faire travailler la raison
Durand, Pascal ULg; Bourton, William

Article for general public (2015)

Detailed reference viewed: 58 (9 ULg)
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See detailPrimary osteosarcoma of the breast : a case report
Crevecoeur, Julie; Jossa, Véronique; GENNIGENS, Christine ULg et al

in Clinical Case Reports (2015)

Detailed reference viewed: 19 (2 ULg)
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See detailWho are my Visitors and Where do They Come From? An Analysis Based on Foursquare Check-ins and Place-based Semantics.
Hallot, Pierre ULg; Stewart, Kathleen; Billen, Roland ULg

in Eurographics Workshop on Urban Data Modelling and Visualisation 2015 (2015, November 23)

Activity recommendation systems aims at providing relevant information depending on targeted users' groups. For instance in a city, it makes sense to differentiate local residents from tourists. This ... [more ▼]

Activity recommendation systems aims at providing relevant information depending on targeted users' groups. For instance in a city, it makes sense to differentiate local residents from tourists. This research investigates to what extent the anonymized data collected from social networks can be used as a basis for making activity recommendations associated with local residents versus tourists when visiting a public place, such as a museum or gallery. Using rules based on the spatial, temporal and semantics of visited places, we are able to infer if a user is likely to be local or a tourist, based on anonymous sample Foursquare data and place-based semantics retrieved using Google Places API. Using semantics of visited places, it becomes possible to infer additional information about a user based on their movements over space and time. Depending on the kind and frequency of visited places, inferences about the aim of a visit to a location are possible. This analysis could provide information to users in the form of recommendations based on their movements while travelling around an area. This study has been performed using Foursquare check-ins for visitors to the Art Institute of Chicago between March 2010 and January 2011. [less ▲]

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See detailNeuropathies périphériques (intro)
WANG, François-Charles ULg

Learning material (2015)

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See detailPIV-based estimation of unsteady loads on a flat plate at high angle of attack using momentum equation approaches
Guissart, Amandine ULg; Bernal, Luis; Dimitriadis, Grigorios ULg et al

Conference (2015, November 23)

The direct measurement of loads with force balance can become challenging when the forces are small or when the body is moving. An alternative is the use of Particle Image Velocimetry (PIV) velocity ... [more ▼]

The direct measurement of loads with force balance can become challenging when the forces are small or when the body is moving. An alternative is the use of Particle Image Velocimetry (PIV) velocity fields to indirectly obtain the aerodynamic coefficients. This can be done by the use of control volume approaches which lead to the integration of velocities, and other fields deriving from them, on a contour surrounding the studied body and its supporting surface. This work exposes and discusses results obtained with two different methods: the direct use of the integral formulation of the Navier-Stokes equations and the so-called Noca's method. The latter is a reformulation of the integral Navier-Stokes equations in order to get rid of the pressure. Results obtained using the two methods are compared and the influence of different parameters is discussed. The methods are applied to PIV data obtained from water channel testing for the flow around a 16:1 plate. Two cases are considered: a static plate at high angle of attack and a large amplitude imposed pitching motion. Two-dimensional PIV velocity fields are used to compute the aerodynamic forces. Direct measurements of dynamic loads are also carried out in order to assess the quality of the indirectly calculated coefficients. [less ▲]

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See detailSous le regard de Zeus Horios. Borner la terre en pays grec.
Lebreton, Sylvain ULg

Conference (2015, November 23)

La diversité des sources relatives aux horoi – limites, frontières, bornes – dans le monde grec antique est sans doute révélatrice de l'importance de la délimitation et du bornage de la terre aux yeux des ... [more ▼]

La diversité des sources relatives aux horoi – limites, frontières, bornes – dans le monde grec antique est sans doute révélatrice de l'importance de la délimitation et du bornage de la terre aux yeux des anciens Grecs. C'est la retranscription de cet enjeu multiforme – tant symbolique que matériel, politique qu'économique – dans le champ du polythéisme qui fera l'objet de cette présentation. Si l'on se borne aux puissances divines explicitement invoquées comme garantes de ces horoi, on constate qu'au sein d'un ensemble où l'on rencontre Apollon, Athéna, Héra, émerge incontestablement la figure du Zeus Horios. La mise en contexte et en série des données relatives au culte de ce dernier, ainsi que l'examen des logiques théologiques qui les soutiennent et les procédés rituels qui les accompagnent, formeront par conséquent le cœur de cette étude. Au-delà des possibilités d'expérimentation sur le fonctionnement du polythéisme hellénique qu'elle offre, cette étude de cas permettra, on l'espère, d'éclairer la manière grecque d'investir symboliquement la terre, en l'occurrence de justifier sur le plan religieux les délimitations appliquées à celle-ci. [less ▲]

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See detailLa subjectivité au dehors : du Saint Genet à la Conférence de Rome
Caeymaex, Florence ULg

Conference (2015, November 23)

Detailed reference viewed: 7 (0 ULg)
See detailPegylated Polyplexes Based On HDAC5 siRNA And Aliphatic Polycarbonate Polymers For An Anticancer Therapy
Frère, Antoine ULg; Baroni, Alexandra; Peulen, Olivier ULg et al

Poster (2015, November 23)

Detailed reference viewed: 8 (4 ULg)