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See detailBiorthogonalization Techniques for Least Squares Temporal Difference Learning
Jung, Tobias ULg; Ernst, Damien ULg

Poster (2012, December 07)

We consider Markov reward processes and study OLS-LSTD, a framework for selecting basis functions from a set of candidates to obtain a sparse representation of the value function in the context of least ... [more ▼]

We consider Markov reward processes and study OLS-LSTD, a framework for selecting basis functions from a set of candidates to obtain a sparse representation of the value function in the context of least squares temporal difference learning. To support efficient both updating and downdating operations, OLS-LSTD uses a biorthogonal representation for the selected basis vectors. Empirical comparisons with the recently proposed MP and LARS frameworks for LSTD are made. [less ▲]

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See detailEfficient ALE mesh management for 3D quasi-Eulerian problems
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Engineering (2012), 92(10), 857-890

In computational solid mechanics, the ALE formalism can be very useful to reduce the size of finite element models of continuous forming operations such as roll forming. The mesh of these ALE models is ... [more ▼]

In computational solid mechanics, the ALE formalism can be very useful to reduce the size of finite element models of continuous forming operations such as roll forming. The mesh of these ALE models is said to be quasi-Eulerian because the nodes remain almost fixed—or almost Eulerian—in the main process direction, although they are required to move in the orthogonal plane in order to follow the lateral displacements of the solid. This paper extensively presents a complete node relocation procedure dedicated to such ALE models. The discussion focusses on quadrangular and hexahedral meshes with local refinements. The main concern of this work is the preservation of the geometrical features and the shape of the free boundaries of the mesh. With this aim in view, each type of nodes (corner, edge, surface and volume) is treated sequentially with dedicated algorithms. A special care is given to highly curved 3D surfaces for which a CPU-efficient smoothing technique is proposed. This new method relies on a spline surface reconstruction, on a very fast weighted Laplacian smoother with original weights and on a robust reprojection algorithm. The overall consistency of this mesh management procedure is finally demonstrated in two numerical applications. The first one is a 2D ALE simulation of a drawbead, which provides similar results to an equivalent Lagrangian model yet is much faster. The second application is a 3D industrial ALE model of a 16-stand roll forming line. In this case, all attempts to perform the same simulation by using the Lagrangian formalism have been unsuccessful. [less ▲]

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See detailAbundance and phenological model of Harmonia axyridis (Coleoptera: Coccinellidae) in field crops
Vandereycken, Axel ULg; Brostaux, Yves ULg; Joie, Emilie ULg et al

Poster (2012, December 07)

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive ... [more ▼]

The multicolored Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was introduced into Western Europe in the late 1990s. This exotic and invasive species is known to thrive principally in shrubs and arboreal habitats. We focus on a phonological model and on annual abundance in various field crops. The abundance of H. axyridis adults and larvae were evaluated during a three-year period, from 2009 to 2011, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. H. axyridis colonizes and reproduces in all four crops studied, with larger densities observed in corn and broad bean. The reproduction of H. axyridis occurs principally in corn and occurred much less in wheat and potato. From 2009 to 2011, abundances of H. axyridis populations were constant except in corn, where the observed densities of all immature stages and adults were higher in 2011 than in 2009. The population dynamics of aphids and H. axyridis were characterized by a symmetric logistic function (S-shape) based on the cumulative population size. [less ▲]

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See detailStructure et fonction des communautés phytoplanctoniques en milieux côtiers marin et lagunaire (Méditerranée – Corse) dans une optique de gestion
Garrido, Marie ULg

Doctoral thesis (2012)

Les écosystèmes côtiers contribuent de manière importante à la production primaire des océans. De par leur position géographique, ils sont particulièrement sensibles à l’eutrophisation. Le compartiment ... [more ▼]

Les écosystèmes côtiers contribuent de manière importante à la production primaire des océans. De par leur position géographique, ils sont particulièrement sensibles à l’eutrophisation. Le compartiment phytoplanctonique y joue un rôle prépondérant au regard de sa position dans la chaîne tropique, mais également en termes de diversité. Il est également capable d’intégrer et/ou de refléter les changements environnementaux qui s’opèrent à court, moyen et long terme. Cette thèse vise à renforcer les connaissances sur la dynamique et la fonction des communautés phytoplanctoniques par rapport aux conditions environnementales dans deux écosystèmes côtiers, en utilisant des techniques traditionnelles comme la microscopie, l’HPLC et d’autres plus récentes comme le Phyto-PAM et la FluoroProbe. Le littoral corse a été choisi comme site d’étude. En effet, ses 1 047 km de côtes regorgent d’écosystèmes particulièrement dynamiques, d’une richesse biologique importante et de zones d’interfaces productives (e.g. structure frontale, milieu lagunaire). Malgré cela, il existe peu de données concernant la dynamique et la fonction de ces micro-algues, aussi bien en milieu marin côtier que lagunaire. Une fréquence d’échantillonnage appropriée à l’échelle d’observation a été utilisée selon les écosystèmes étudiés et le type d’étude menée (in situ ou expérimentale), allant de prélèvements mensuels à des prélèvements journaliers. Dans un premier temps, nous avons poursuivi les efforts engagés depuis plusieurs années concernant l’amélioration des méthodes d’analyses spectrofluorimétriques nécessaires pour l’étude de la dynamique et l’analyse fonctionnelle des communautés phytoplanctoniques. Des recommandations concernant les conditions de conservation des échantillons (i.e. durée, température) ont été dégagées pour l’analyse au Phyto-PAM, afin d’affiner les limites d’utilisation de cet outil. Nous avons également testé l’utilisation de la FluoroProbe dans les écosystèmes côtiers en Méditerranée. Dans un second temps, nous avons étudié la variabilité spatio-temporelle des communautés phytoplanctoniques en milieu marin côtier (Calvi et Bastia) et en milieu lagunaire eutrophisé (Réserve Naturelle de Biguglia). Les résultats ont mis en avant une succession écologique et une structure des peuplements phytoplanctoniques différentes dans les deux écosystèmes marins côtiers étudiés, présentant des spécificités locales propres et comparés à l’échelle des zones côtières en Méditerranée. Nous avons démontré que des événements météorologiques pouvaient influencer les variations observées, agissant directement sur l’abondance des espèces ou indirectement sur les conditions du milieu (e.g. nutriments). Au niveau lagunaire, les actions de gestion mises en œuvre ont impacté la structure et l'efficacité photosynthétique des communautés phytoplanctoniques. Les modifications des flux hydrologiques ont exacerbé le caractère confiné de la lagune et des efflorescences successives d’espèces opportunistes et non profitables au réseau trophique supérieur ont été observées. Ces études ont permis de fournir une aide scientifique en ce qui concerne la prise de décision qui incombe aux acteurs de l’environnement et plus particulièrement les gestionnaires, dans une optique de gestion. [less ▲]

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See detailPistes pour une mesure de la compétence numérique
Vandeput, Etienne ULg; Henry, Julie ULg

in Questions Vives : Recherches en Education (2012), 7(17),

Nowadays, in the educational field, digital literacy is considered absolutely necessary for students and citizens. If it is occasionally easy to observe the good practice of learners, there remains to ... [more ▼]

Nowadays, in the educational field, digital literacy is considered absolutely necessary for students and citizens. If it is occasionally easy to observe the good practice of learners, there remains to determine how to train them and how to certify their abilities. The visaTICE project tries to face both issues. In this project, certification is a big challenge, but another challenge is to set up a system that takes into account the school context but that is not constrained by it. Presently the visaTICE project has developed online courses, tests, ability trees, coach training programs, which can be used in different contexts but we are not able to prove now, neither the training efficiencies, nor the suitability of the certification tests. A significant number of students will participate in the certification test for the first time in May 2012. Up to now, the collaborative design principle applied in visaTICE acts as a warranty. [less ▲]

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See detailAnomalous OI-989 Å intensity profile: solving an old mystery.
Hubert, Benoît ULg; Gérard, Jean-Claude ULg; Shematovich, Valery I. et al

Poster (2012, December 06)

Sounding rocket measurements conducted in 1988 under high solar activity conditions had revealed that the intensity of the thermospheric OI emission at 989 Å presents an anomalous vertical profile ... [more ▼]

Sounding rocket measurements conducted in 1988 under high solar activity conditions had revealed that the intensity of the thermospheric OI emission at 989 Å presents an anomalous vertical profile. Observation presents an intensity much higher than what can be expected compared with theoretical results including the photochemical sources of excited oxygen and the radiative transfer of the photons of the OI-989 sextuplet especially above the exobase. Attempts were conducted to clarify the discrepancy by including the non-thermal O(3P) population that appears around the exobase and higher, and that can scatter Doppler-shifted photons of the line profile farther from the rest wavelength. All attempts based on detail modeling of the photochemical processes and radiative transfer revealed unable to account for the discrepancy. Recently the FUV and EUV solar flux has been obtained at very high spectral resolution with the SOHO-SUMER instrument, revealing a significant solar oxygen emission at 989 Å, i.e. a source of photons that had never been accounted for before. In this study, we compute the radiative transfer of the OI-989 Å multiplet including the photochemical sources of excited oxygen, the scattering of incident solar photons and the effect of non-thermal atoms. We find a good agreement with the previous sounding rocket observation, solving the old mystery. We also compare the model simulations with the observations of the STP-78 satellite to better determine the relative importance of the various parameters at work in the radiative transfer of the OI-989 Å multiplet. [less ▲]

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See detailUnderstanding the 3D morphology of the Jovian aurora using Juno-UVS observations: simulations and tomographic reconstruction
Bonfond, Bertrand ULg; Gladstone, Randy

Conference (2012, December 06)

The aurora at Jupiter is a spectacular signature of the many processes taking place in the Jovian magnetosphere, such as magnetic reconnection, large scale electric currents, moon-magnetosphere ... [more ▼]

The aurora at Jupiter is a spectacular signature of the many processes taking place in the Jovian magnetosphere, such as magnetic reconnection, large scale electric currents, moon-magnetosphere interactions, etc. As a consequence, this aurora is extremely complex and dynamic, powered by a variety of phenomena that we have only begun to unravel. The 3D morphology of the aurora can provide a way to untangle the different processes at play. As a polar orbiter, Juno will provide unprecedented global and close-up views of Jupiter’s auroral emissions. As it flies at low altitude over auroral curtains, spots and patches, it will provide views of these features from multiple points, allowing the retrieval of their 3D structure. The ultraviolet spectrograph on board Juno (Juno-UVS) is designed to observe auroral emissions in the 68 to 210 nm range. It is equipped with a scan mirror targeting up to +/-30 degrees off axis of the spacecraft rotation plane. We have built a planning tool to determine which auroral targets of interest, such as a satellite footprint for example, is observable by the instrument at any time during the mission. We have also built a simulation tool that allows us to generate realistic views of the Jovian aurora as observed by Juno-UVS. The purpose of this tool is to 1) fine-tune the selection algorithm to identify the most valuable data in the harsh radiation environment encountered around Jupiter, and 2) serve as a test bed for adapting tomographic algorithms to the Juno-UVS dataset. Tomographic reconstruction will allow estimation of the position and horizontal extent of the auroral regions of interest, as well as their vertical emission structure, which may be used to characterize the energy distribution of the precipitating particles responsible for the features. [less ▲]

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See detailExcess Return Forecast Using a Dynamic Asset Class Factor Model
Hübner, Georges ULg; Sougné, Danielle ULg; Wijnandts, Jean-Charles ULg

E-print/Working paper (2012)

We propose a Dynamic Hierarchical Factor Model using Asset classes to predict mutual funds excess returns. We use different forecast combination schemes of bivariate model considering each asset class ... [more ▼]

We propose a Dynamic Hierarchical Factor Model using Asset classes to predict mutual funds excess returns. We use different forecast combination schemes of bivariate model considering each asset class factor in isolation. Primary analysis highlights the importance to account for asset class specific variations together with between classes or common variations. Further refinements of the a priori repartition are however in order. Forecasting performance of the model outperforms the historical mean benchmark both in terms of MSPE and utility based criteria. A forecasting exercise matching more closely real-time conditions must be undertaken to validate these initial results. [less ▲]

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See detailHow the debate on the protection of IDPs could inform the debate on the protection of environmental migrations
Gemenne, François ULg; Brücker, Pauline

Conference (2012, December 06)

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See detailLikely Detection of UV Auroral Emission from the Magnetic Footprint of Callisto
Clarke, John; Bhattacharyya, Dolon; Montgomery, Jordan et al

Poster (2012, December 06)

A large number of UV images of Jupiter's aurora were obtained in 2007/2008 with the Hubble Space Telescope (HST) ACS/SBC camera. The initial results on variations with the solar wind conditions have been ... [more ▼]

A large number of UV images of Jupiter's aurora were obtained in 2007/2008 with the Hubble Space Telescope (HST) ACS/SBC camera. The initial results on variations with the solar wind conditions have been published elsewhere, but the large database permits other studies to be performed. In particular, while auroral emissions have been detected from the magnetic footprints of Io, Europa, and Ganymede in Jupiter's atmosphere, the footprint of Callisto has been located too close to the main auroral oval to be detected. We have thus analyzed images of the ultraviolet auroral emissions of Jupiter taken using the F115LP filter on the HST/ACS instrument. Using a unique co-addition method, we have identified a strong candidate for the footprint of Callisto on May 24, 2007. We tested this finding by applying the same co-addition method to a nearly identical auroral configuration on May 30, 2007 when Callisto was well removed in its orbit. Comparing the two co-added images, we can clearly see the presence of Callisto’s footprint on the 24th and its absence on the 30th. The method relies as well on the motion of Callisto's footprint remaining under the satellite, while most of the auroral emissions rotate with the planet. The images and analysis method will be presented in this presentation. [less ▲]

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See detailINFLUENCE OF MYELOPEROXIDASE ACTIVITY ON EQUINE POST-THAW SEMEN QUALITY
Ponthier, Jérôme ULg; Franck, Thierry ULg; Parrilla Hernandez, Sonia ULg et al

in Edeas, Marvin (Ed.) Proceedings of the 2nd ISANH World congress on Fertility and Antioxidants (2012, December 06)

This study confirms that active MPO is associated with cellular fraction of the ejaculate, as previously suggested for total MPO concentration in thawed semen (2). However, active MPO concentrations were ... [more ▼]

This study confirms that active MPO is associated with cellular fraction of the ejaculate, as previously suggested for total MPO concentration in thawed semen (2). However, active MPO concentrations were dramatically lower than total MPO concentrations observed in equine semen (3), which could be explained by presence of inactive MPO subunits in semen. MPO activity in sperm-rich pellet can be used as a predictive marker of post-thaw semen quality. Moreover, methods to inhibit MPO should be investigated in semen. [less ▲]

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See detailQuelques constats sur le devenir des métiers industriels
Remy, Céline ULg

Conference given outside the academic context (2012)

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See detailUsing a 2D Model of the Io Plasma Torus to Investigate the Effects of Density Variations on the Morphology and Intensity of the Io Footprint
Payan, Alexia; Rajendar, Ashok; Paty, Carol et al

Poster (2012, December 06)

Io is the primary source of plasma in the Jovian magnetosphere, continuously releasing approximately 1 ton/s of SO2 from volcanic eruptions. The interaction of Io with Jupiter’s magnetosphere is strongly ... [more ▼]

Io is the primary source of plasma in the Jovian magnetosphere, continuously releasing approximately 1 ton/s of SO2 from volcanic eruptions. The interaction of Io with Jupiter’s magnetosphere is strongly influenced by the density structure of the resulting plasma torus and the position of Io relative to the center of the torus [Bonfond et al. 2008]. This unusual interaction produces a complex auroral feature on Jupiter’s ionosphere known as the Io footprint. Hubble Space Telescope (HST) observations of Jupiter’s far-UV aurora during spring 2007 showed an increased number of isolated auroral blobs along with a continuous expansion of Jupiter’s main auroral oval over a few months. These blobs were associated with several large injections of hot plasma between 9 and 27 Jovian radii. These events coincided with a large volcanic eruption of the Tvashtar Paterae on Io, as observed by the New Horizons spacecraft [Spencer et al., 2007]. This, in turn, may have resulted in a significant increase in the plasma torus density. Besides, on June 7th, 2007, the Io footprint momentarily became so faint that it disappeared under a diffuse patch of emission remaining from an injection blob [Bonfond et al., 2012]. The goal of the present study is to examine the relationship between the increased density of the plasma torus and the dimming of the Io footprint. We implement a 2D model of the Io plasma torus that treats the variable-density torus as being composed of discrete layers of uniform density. As the co-rotating plasma in the plasma torus impinges on Io, Alfvén waves are launched at a pushback angle obtained from Gurnett and Goertz [1981]. The waves propagate inside the plasma torus through reflection and refraction at density discontinuities where they lose some of their initial energy. Using the above model, we can track the Alfvén wave fronts in the plasma torus and determine the longitude at which they exit the torus along with the corresponding remaining energy. Since Alfvén waves are capable of accelerating charged particles along magnetic field lines, we assume that the discrete Io footprint features are created at these longitudes, and that the intensity of each of these features is positively correlated to the energy transported by the wave front as it exits the plasma torus. Therefore, the model allows us to investigate both the effects of density changes and of Io’s position in the plasma torus on the intensity and the morphology of the Io footprint. In this context, the model enables us to determine the density increase in the plasma torus required to explain the apparent disappearance of Io footprint given its position at that time. [less ▲]

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See detailLa maison zéro énergie, et après ?
Monfils, Stéphane ULg

Conference given outside the academic context (2012)

Introduction à la future réglementation, à la problématique des bâtiments existants et à la performance environnementale

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See detailCatalytic purification of biogas
Claude, Vincent ULg; Lambert, Stéphanie ULg

Poster (2012, December 05)

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See detailHydrodynamique et Architecture Navale
Hage, André; Rigo, Philippe ULg; Lapy, Matthieu ULg

in Journées scientifiques et techniques du CETMEF 2012 (2012, December 05)

State of art en matière d'hydrodynamique navale et architecture navale pour la navaigatio nfluviale

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See detailDes controverses souterraines et silencieuses ? Les vers de terre (lombricidés), l’agronomie et l’agriculture : d’une « non-histoire » à leur délicate mobilisation dans la conception et l’évaluation de formes contemporaines d’agricultures « durables »
Dannevoye, Bastien ULg

Conference (2012, December 05)

This communication investigates the recent and marginal scientific and agronomic interest in earthworms (or "lumbricids"), which paradoxically accounts for the first animal biomass of the globe. After ... [more ▼]

This communication investigates the recent and marginal scientific and agronomic interest in earthworms (or "lumbricids"), which paradoxically accounts for the first animal biomass of the globe. After giving some historical points of reference about earthworms' quite recent scientific knowledge-building - thanks to soil scientists and biologists' works -, we present the manner in which the earthworms and their agricultural and ecological functions are valued today amongst groups of farmers linked to "conservation agriculture practices". This second part is built on sociological observation and interviews amongst those "conservation farmers", at work as well as communicating on their soil conservation practices (no-till, direct drilling, etc.). By doing that, we aim at describing how the earthworms, conceived as "intermediary objects" and "spokesperson" of the much larger soil biology, allows for those practicians to make strongly hold together production and environmental challenges in the agriculture they're developing... instead of opposing those stakes as it's usually the case. [less ▲]

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