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See detailA random walk in Machine Learning
Begon, Jean-Michel ULg

Conference given outside the academic context (2017)

Since the dawn of machine learning (ML), it hasn’t stop spreading into our everyday lives in new, creative ways. Why Google, Facebook, Amazon and the like have invested so much in ML recently? What can ... [more ▼]

Since the dawn of machine learning (ML), it hasn’t stop spreading into our everyday lives in new, creative ways. Why Google, Facebook, Amazon and the like have invested so much in ML recently? What can (and can’t) ML actually do for us? In this non-technical (and non-exhaustive) talk we will examine ML applications ranging from standard uses to some of the most exotic ones. [less ▲]

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See detailOffline Policy-search in Bayesian Reinforcement Learning
Castronovo, Michaël ULg

Doctoral thesis (2017)

This thesis presents research contributions in the study field of Bayesian Reinforcement Learning — a subfield of Reinforcement Learning where, even though the dynamics of the system are un- known, the ... [more ▼]

This thesis presents research contributions in the study field of Bayesian Reinforcement Learning — a subfield of Reinforcement Learning where, even though the dynamics of the system are un- known, the existence of some prior knowledge is assumed in the form of a distribution over Markov decision processes. In this thesis, two algorithms are presented: OPPS (Offline Prior- based Policy Search) and ANN-BRL (Artificial Neural Networks for Bayesian Reinforcement Learning), whose philosophy consists to analyse and exploit the knowledge available beforehand prior to interacting with the system(s), and which differ by the nature of the model they make use of. The former makes use of formula-based agents introduced by Maes et al. in (Maes, Wehenkel, and Ernst, 2012), while the latter relies on Artificial Neural Networks built via SAMME (Stagewise Additive Modelling using a Multi-class Exponential loss function) — an AdaBoost algorithm developed by Zhu et al. in (Zhu et al., 2009). Moreover, we also describe a comprehensive benchmark which has been created to compare Bayesian Reinforcement Learning algo- rithms. In real life applications, the choice of the best agent to fulfil a given task depends not only on their performances, but also on the computation times required to deploy them. This benchmark has been designed to identify the best algorithms by taking both criteria into account, and resulted in the development of an open-source library: BBRL (Benchmarking tools for Bayesian Reinforcement Learning) (https://github.com/mcastron/BBRL/wiki). [less ▲]

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See detailApport de l'ENMG aux syndromes douloureux diffus
WANG, François-Charles ULg

Scientific conference (2017, March 14)

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See detailQSAR models and the flexible regulation of chemicals
Thoreau, François ULg

Scientific conference (2017, March 14)

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See detailEvaluation de la fonction rénale
DELANAYE, Pierre ULg

Conference (2017, March 14)

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See detailImagerie très haute résolution en agriculture: potentialité de la technologie drone
Bauwens, Sébastien ULg

Conference given outside the academic context (2017)

Ces dix dernières années, l’émergence des drones civils ouvre de nouvelles perspectives dans divers domaines tels que la logistique, le secourisme, les médias, la foresterie et l'agriculture. Dans le ... [more ▼]

Ces dix dernières années, l’émergence des drones civils ouvre de nouvelles perspectives dans divers domaines tels que la logistique, le secourisme, les médias, la foresterie et l'agriculture. Dans le cadre de cette présentation, nous ferons le point sur le potentiel qu’offrent les images acquises par drone au niveau du secteur agricole et forestier. La réponse spectrale des plantes au rayonnement solaire sera abordée, les capteurs spectraux pour drones seront ensuite présentés ainsi que les différentes plateformes drone. Finalement, nous verrons le type d’information qui peut être extrait de ces images spectrales à partir de cas d’études agronomiques et forestiers. [less ▲]

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See detailMUNIX vs TASPM
WANG, François-Charles ULg

Conference (2017, March 10)

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See detailUne méthode simple d'évaluation de l'excitabilité nerveuse ?
WANG, François-Charles ULg

Scientific conference (2017, March 10)

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See detailPratiques de coopération entre généralistes et médecins du travail
Vanmeerbeek, Marc ULg

Scientific conference (2017, March 09)

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Peer Reviewed
See detailAnticoherence measures for spin states
Baguette, Dorian ULg; Martin, John ULg

Poster (2017, March 09)

Among all possible spin states, spin-coherent states are the most classical because the spin expectation value in these states yields a vector of maximal norm pointing in a well defined direction. In ... [more ▼]

Among all possible spin states, spin-coherent states are the most classical because the spin expectation value in these states yields a vector of maximal norm pointing in a well defined direction. In contrast, anticoherent spin state to order t are such that <(J.n)^k> is independent of the unit vector n for k = 1, ..., t [1]. By construction, coherent and anticoherent spin states are at both ends of the spectrum of classicality. The aim of this work is to position all possible spin states on such a spectrum, that is to provide measures of anticoherence. To this aim, we introduce an axiomatic definition of anticoherence measures to any order t. In particular, we show that the total variance of a pure spin state, first introduced in [2] can be used to define a measure of anticoherence to order 1. We describe a systematic way of constructing anticoherence measures to any order that relies on the mapping between spin-j states and symmetric states of N = 2j spin-1/2. In particular, we exploit the fact that anticoherent spin states to order t have maximally mixed t-spin-1/2 reduced density matrices in the symmetric subspace [3]. [1] J. Zimba, Electron. J. Theor. Phys. 3, 143 (2006). [2] A. A. Klyachko, B. Öztop, and A. S. Shumovsky, Phys. Rev. A 75, 032315 (2007). [3] D. Baguette, T. Bastin, and J. Martin, Phys. Rev A 90, 032314 (2014). [less ▲]

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See detailLong-range Rydberg-blockade entangling gate mediated by auxiliary atoms
Cesa, Alexandre ULg; Martin, John ULg

Poster (2017, March 09)

Arrays of qubits encoded in the ground state manifold of trapped neutral atoms appear as a promising platform for the realisation of a scalable quantum computer. Indeed, such physical qubits have a long ... [more ▼]

Arrays of qubits encoded in the ground state manifold of trapped neutral atoms appear as a promising platform for the realisation of a scalable quantum computer. Indeed, such physical qubits have a long coherence time and allow for high-fidelity single-qubit operations [1]. In such a platform, entangling two-qubit gates can be implemented by exploiting the Rydberg-blockade mechanism to produce a phase shift or a flip of the state of a target atom conditioned on the state of a control atom [2]. However, because dipole-dipole interactions fall off rapidly with the interatomic distance, such entangling gates based on Rydberg-blockade are impractical between distant qubits. In this work, we propose a protocol to implement long-range Rydberg-blockade gates (CZ or CNot) using auxillary non-coding atoms to transfer the Rydberg excitation from the control to the target qubit. The dependence of the fidelity on the number of auxillary atoms, the blockade strength and the decay rates of the Rydberg states are determined. When compared to a sequential application of nearest neighbours entangling gates, our protocol leads to a larger fidelity and a reduction of the overall gate duration (which scales linearly with the number of auxillary atoms). [1] M. Saffman, J. Phys. B: At. Mol. Opt. Phys. 49, 202001 (2016). [2] D. Jaksch, J. I. Cirac, P. Zoller, S. L. Rolston, R. Côté, and M. D. Lukin, Phys. Rev. Lett. 85, 2208 (2000). [less ▲]

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See detailExercices pratiques de légistique
Grandjean, Geoffrey ULg

Learning material (2017)

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See detailArduino: une carte électronique aux multiples possibilités
Sartor, Kevin ULg

Scientific conference (2017, March 08)

Formation destinée à l'utilisation des cartes électroniques "Arduino". Au programme une brève introduction, une liste de possibilités non exhaustive, le tout suivi de cas pratiques et de conseils pour la ... [more ▼]

Formation destinée à l'utilisation des cartes électroniques "Arduino". Au programme une brève introduction, une liste de possibilités non exhaustive, le tout suivi de cas pratiques et de conseils pour la réalisation de votre premier projet. [less ▲]

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See detailStandardized Settling Cell Design
Leleu, David ULg; Pfennig, Andreas ULg

Scientific conference (2017, March 07)

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See detailCharacterizing exoplanetary atmospheres with a mid-infrared nulling spectrograph
Defrere, Denis ULg; Léger, Alain; Absil, Olivier ULg et al

Poster (2017, March 07)

The discovery of an increasing number of terrestrial planets around nearby stars marks the dawn of a new era in the exoplanet field: the characterization and understanding of their atmospheres. To make ... [more ▼]

The discovery of an increasing number of terrestrial planets around nearby stars marks the dawn of a new era in the exoplanet field: the characterization and understanding of their atmospheres. To make significant progress, it becomes clear that a large number of exoplanetary atmospheres have to be studied at various wavelengths. This is particularly relevant for identifying possible bio-signatures. In this poster, we present a concept of a space-based mid-infrared nulling spectrograph that can characterize a large number of exoplanetary atmospheres and provide key information on their size, surface temperature, and the presence of key molecules such as CO2, H2O, CH4 and O3. The proposed mission concept would be particularly suited to characterize Proxima Cen b. [less ▲]

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See detailTrees and shrubs influence the behaviour of grazing cattle and rumen fermentation
Vandermeulen, Sophie ULg

Doctoral thesis (2017)

Hedgerows and woody strips have been used to enclose fields but declined due to the loss of a direct economic value, abandonment of traditional management techniques and agricultural intensification ... [more ▼]

Hedgerows and woody strips have been used to enclose fields but declined due to the loss of a direct economic value, abandonment of traditional management techniques and agricultural intensification. Nowadays, shrubs and trees on pastures are promoted again through environment-friendly policies and the interest in using them as forage for ruminant increases in both temperate and tropical ecosystems. Woody plants on farmland could yield a wide range of ecosystem services and provide benefits for farmers and their animals such as forage supply to livestock, animal protection against severe weather and reduced parasitic infestation. Moreover, shifts in digestive physiology can be observed that will in turn affect the welfare and the performances of the animal and the production system as a whole. Therefore, in order to contribute to the development of sustainable systems using shrubs and trees as a feed component in its full right, the aim of this work was to investigate the influence of trees and shrubs on the behaviour of grazing cattle and their selectivity towards woody species, and to determine the changes induced by temperate and tropical shrub and tree species on rumen fermentation. Firstly, the behaviour of grazing dairy heifers was recorded during the whole grazing season as well as their selectivity towards temperate woody species in a hedge. It was concluded that having access to a hedge influenced the behaviour of grazing cattle, as the animals ingested woody plants in each season but mostly when the available pasture biomass was lower. The most selected species were Carpinus betulus, Corylus avellana, Cornus sanguinea and Crataegus monogyna. Secondly, the chemical composition, in vitro rumen fermentation profile and protein precipitation capacity (PPC) of the temperate shrub and tree species were measured. The analyses showed that Fraxinus excelsior presented the most interesting profile in terms of chemical composition and in vitro fermentation production. Among the preferred species, C. monogyna and C. avellana produced lower CH4 and the latest had the highest PPC. Thirdly, three newly-developed cultivars of the tropical Desmanthus genus were studied for their effects on in vitro rumen fermentation including potential to reduce CH4. Desmanthus leptophyllus and D. bicornutus had the highest anti-methanogenic potential, and D. bicornutus was more digestible. In conclusion, both temperate and tropical shrub and tree fodder are promising to supplement cattle with good quality forage. Cattle can browse woody species voluntarily, however, further investigations are needed to provide relevant practical recommendations on how to manage this resource adequately in order to balance intake by the animal and regrowth capacity of the plant. The impact of management strategies relying on cutting and preservation should also be assessed. Moreover, benefits of shrubs and trees on pastures beyond the animal feeding and nutrition are still poorly characterized while, in an agroecological perspective, they can contribute to a significant improvement of the sustainability of ruminant production systems. [less ▲]

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See detailIncreased sea ice cover disrupts food web structure in coastal Antarctica
Michel, Loïc ULg; Dubois, Philippe; Eleaume, Marc et al

Conference (2017, March 03)

Antarctica currently undergoes strong and contrasted impacts linked with climate change. While the West Antarctic Peninsula is one of the most rapidly warming regions in the world, resulting in sea ice ... [more ▼]

Antarctica currently undergoes strong and contrasted impacts linked with climate change. While the West Antarctic Peninsula is one of the most rapidly warming regions in the world, resulting in sea ice cover decrease, the sea ice cover of East Antarctica unexpectedly tends to increase, possibly in relation with changes in atmospheric circulation. Sea ice is a major environmental driver in Antarctica, and changes in sea ice cover are likely to influence benthic food web structure through several processes (modifications of benthic-pelagic coupling, disruption of benthic production and/or modifications of benthic community structure and therefore resource availability for benthic consumers). To date, regions where sea ice cover is decreasing have received more attention than regions where it is increasing. Here, on the other hand, we studied shallow (0-20 m) benthic food web structure on the coasts of Petrels Island (Adélie Land, East Antarctica) during an event of unusually high spatial and temporal (two successive austral summers without seasonal break-up) sea ice cover. Using time-tested integrative trophic markers (stable isotope ratios of carbon, nitrogen and sulfur) and state-of-the-art data analysis tools (bayesian ecological models), we studied the structure of the food web associated to benthic macroinvertebrates communities. In total, 28 macroinvertebrate taxa spanning most present animal groups (sponges, sea anemones, nemerteans, nematods, sipunculids, sessile and mobile polychaetes, gastropods, bivalves, pycnogonids, crustaceans, sea stars, sea urchins, brittle stars and sea cucumbers) and functional guilds (grazers, deposit feeders, filter feeders, predators, scavengers) were investigated. Our results indicate that the absence of seasonal sea ice breakup deeply influences coastal benthic food webs in Antarctica. We recorded marked differences from literature data, both in terms of horizontal (i.e. primary producers and resources supporting animal populations) and vertical (i.e. trophic level of the studied consumers) structure of the food web. Overall, sympagic (sea-ice associated) algae dominated the diet of many important consumers, and the trophic levels of invertebrates were low, suggesting omnivore consumers relied less on predation and/or scavenging than in normal environmental conditions. Surprisingly, few animals seemed to feed on the extremely abundant benthic biofilm, whose exceptional development was also presumably linked with the peculiar sea ice conditions. Interpretation of data was complicated by the peculiar ecophysiological features of Antarctic invertebrates, whose very low metabolic rates could be associated to low tissue turnover. However, comparison of data obtained in the austral summers of 2013-2014 (first year without seasonal breakup) and 2014-2015 (second year without seasonal breakup) clearly showed that the observed trends were linked with actual temporal changes in invertebrate feeding habits rather than with other potential ecological drivers. Our results provide insights about how Antarctic benthic consumers, which have evolved in an extremely stable environment, might adapt their feeding habits in response to sudden man-driven changes in environmental conditions and trophic resource availability. They also show that local and/or global trends of sea ice increase in Antarctica could cause strong changes in food web structure and therefore impact zoobenthic communities. This reinforces the view that, no matter their overall direction (i.e. increase or decrease), fluctuations in sea ice cover are likely to influence Antarctic benthic ecosystems' structure and functioning. [less ▲]

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See detailBehavior of digital sequences through exotic numeration systems
Leroy, Julien ULg; Rigo, Michel ULg; Stipulanti, Manon ULg

in Electronic Journal of Combinatorics (2017), 24(1), 14436

Many digital functions studied in the literature, e.g., the summatory function of the base-k sum-of-digits function, have a behavior showing some periodic fluctuation. Such functions are usually studied ... [more ▼]

Many digital functions studied in the literature, e.g., the summatory function of the base-k sum-of-digits function, have a behavior showing some periodic fluctuation. Such functions are usually studied using techniques from analytic number theory or linear algebra. In this paper we develop a method based on exotic numeration systems and we apply it on two examples motivated by the study of generalized Pascal triangles and binomial coefficients of words. [less ▲]

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