Publications ORBi OA
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See detailModelling of organic Rankine cycle power systems in off-design conditions: an experimentally-validated comparative study
Dickes, Rémi ULg; Dumont, Olivier ULg; Daccord, Rémi et al

in Energy (2017), 123

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development ... [more ▼]

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development, power generation from low-grade heat sources is gaining interest and the organic Rankine cycle (ORC) is seen as one of the most promising technologies for such applications. In this paper, it is proposed to perform an experimentally-validated comparison of different modelling methods for the off-design simulation of ORC-based power systems. To this end, three types of modelling paradigms (namely a constant-efficiency method, a polynomial-based method and a semi-empirical method) are compared both in terms of their fitting and extrapolation capabilities. Post-processed measurements gathered on two experimental ORC facilities are used as reference for the models calibration and evaluation. The study is first applied at a component level (i.e. each component is analysed individually) and then extended to the characterization of the entire organic Rankine cycle power systems. Benefits and limi- tations of each modelling method are discussed. The results show that semi-empirical models are the most reliable for simulating the off-design working conditions of ORC systems, while constant-efficiency and polynomial-based models are both demonstrating lack of accuracy and/or robustness. [less ▲]

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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 detailDeformations of soap bubbles in a uniform electric field
Mawet, Sébastien ULg

Conference (2017, March 15)

The study of the deformations undergone by a soap bubble submitted to an electrical force began with Taylor and Wilson 1 and the observation of the so-called Taylor’s cones. Beyond this particular ... [more ▼]

The study of the deformations undergone by a soap bubble submitted to an electrical force began with Taylor and Wilson 1 and the observation of the so-called Taylor’s cones. Beyond this particular structure, few studies analyzed the bubble deformations. For example, what is the link between the deformations and the electrical force ? Or, how do charges move in the thin soap film formed by the bubble ? To answer those questions, we characterize the shape variations of the surface of the bubble immersed in the uniform electric field of a plan capacitor. In particular, our study focuses on hemispherical bubbles lying on the bottom electrode of a plane capacitor. This study allows us to observe some interesting phenomena like the appearance of a hysteresis cycle in the deformation amplitude. [less ▲]

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See detailUnderground pumped storage hydropower plants using open pit mines: How do groundwater exchanges influence the efficiency?
Pujades, Estanislao ULg; Orban, Philippe ULg; Bodeux, Sarah ULg et al

in Applied Energy (2017), 190

Underground Pumped Storage Hydropower (UPSH) is a potential alternative to manage electricity production in flat regions. UPSH plants will interact with the surrounding porous medium through exchanges of ... [more ▼]

Underground Pumped Storage Hydropower (UPSH) is a potential alternative to manage electricity production in flat regions. UPSH plants will interact with the surrounding porous medium through exchanges of groundwater. These exchanges may impact the surrounding aquifers, but they may also influence the efficiency of the pumps and turbines because affecting the head difference between the reservoirs. Despite the relevance for an accurate efficiency assessment, the influence of the groundwater exchanges has not been previously addressed. A numerical study of a synthetic case is presented to highlight the importance of considering the groundwater exchanges with the surrounding porous medium. The general methodology is designed in order to be further applied in the decision making of future UPSH plants introducing each case specific complexity. The underground reservoir of a hypothetical UPSH plant, which consists in an open pit mine, is considered and modelled together with the surrounding porous medium. Several scenarios with different characteristics are simulated and their results are compared in terms of (1) head difference between the upper and lower reservoirs and (2) efficiency by considering the theoretical performance curves of a pump and a turbine. The results show that the efficiency is improved when the groundwater exchanges increase. Thus, the highest efficiencies will be reached when (1) the underground reservoir is located in a transmissive porous medium and (2) the walls of the open pit mine do not constrain the groundwater exchanges (they are not waterproofed). However, a compromise must be found because the characteristics that increase the efficiency also increase the environmental impacts. Meaningful and reliable results are computed in relation to the characteristics of the intermittent and expected stops of UPSH plants. The frequency of pumping and injection must be considered to properly configure the pumps and turbines of future UPSH plants. If not, pumps and turbines could operate far from their best efficiency conditions. [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 detailImprinting superconducting vortex footsteps in a magnetic layer
Brisbois, Jérémy ULg

Conference (2017, March 14)

We experimentally show that the principle of local polarization of a magnetic layer, a well-known method to store information, namely in hard drives and credit cards, can be applied for imprinting into a ... [more ▼]

We experimentally show that the principle of local polarization of a magnetic layer, a well-known method to store information, namely in hard drives and credit cards, can be applied for imprinting into a soft magnetic layer of permalloy (Py) the trajectory of vortices moving in a superconducting film (Nb). In full analogy with a magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py layer. We have used the magneto-optical imaging technique to investigate the mutual interaction between superconducting vortices and ferromagnetic domains. In general, we observe that the flux propagation is delayed at the border of the magnetic layer. Interestingly, in thin Py layers without stripe domains, vortices leave clear imprints of locally polarized magnetic moments along their trajectories. Furthermore, the printings were found to be stable and could still be observed at room temperature, allowing for ex situ observation of the flux penetration in superconductors. We expect our findings to pave the way for further studies for optimizing magnetic recording of superconducting vortex trajectories. [less ▲]

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See detailLa réalisation et les complications de la césarienne dans la race Blanc-bleu Belge
Djebala, Salem ULg; Casalta, Hélène ULg; Rao, Anne-Sophie ULg et al

Conference given outside the academic context (2017)

La césarienne est la chirurgie la plus couramment réalisée en Belgique. Bien que celle-ci soit une intervention de routine le taux de complications post-opératoires est non négligeable. Deux enquêtes ont ... [more ▼]

La césarienne est la chirurgie la plus couramment réalisée en Belgique. Bien que celle-ci soit une intervention de routine le taux de complications post-opératoires est non négligeable. Deux enquêtes ont été réalisées au près des éleveurs et des vétérinaires sur la préparation, le déroulement de la césarienne et les soins post-opératoires. Ces deux enquêtes nous ont permis de tirer des conclusions et formuler des recommandations afin de réduire le taux de complication. [less ▲]

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See detailEvaluation de la fonction rénale
DELANAYE, Pierre ULg

Conference (2017, March 14)

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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 detailRealization of the Najafi-Golestanian microswimmer
Hubert, Maxime ULg; Grosjean, Galien ULg; Lagubeau, Guillaume et al

Conference (2017, March 14)

The development of artificial microswimmers, microscopic robots that swim in a fluid like sperm cells and motile bacteria, could cause a leap forward in various fields such as microfluidics, microsystems ... [more ▼]

The development of artificial microswimmers, microscopic robots that swim in a fluid like sperm cells and motile bacteria, could cause a leap forward in various fields such as microfluidics, microsystems, or minimally invasive medicine. Nature provides plenty of examples of efficient microswimmers. However, a bottom-up approach, looking at the simplest ingredients needed to generate a microswimmer, can lead to a deeper under- standing of the swimming problem. First described by Najafi and Golestanian 1 , a paradigmatic microswimmer is the three-linked-spheres model, which follows a minimalist approach for propulsion by shape shifting. In this presentation, we describe the experimental realisation of this microswimmer using self-assembled ferromagnetic particle at an air-water interface, powered by an uniform oscillating magnetic field 2 . A model, using two har- monic oscillators, reproduces the experimental findings. Because the model remains general, the same approach could be used to design a variety of efficient microswimmers. [less ▲]

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See detailMechanisms of Igf2 inhibition in thymic epithelial cells infected with CVB4 E2
Michaux, Hélène ULg; Charlet-Renard, Chantal; Martens, Henri ULg et al

Poster (2017, March 12)

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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 detailDéveloppements scientifiques et nouvelles technologies pour l'application de produits phytosanitaires de précision
Lebeau, Frédéric ULg

Conference (2017, March 10)

Depuis leur introduction, les produits phytosanitaires ont largement démontré leur efficacité pour assurer des rendements agricoles élevés. Toutefois, les nuisances sanitaires et environnementales sont ... [more ▼]

Depuis leur introduction, les produits phytosanitaires ont largement démontré leur efficacité pour assurer des rendements agricoles élevés. Toutefois, les nuisances sanitaires et environnementales sont rapidement apparues ainsi que le développement de diverses résistances. Les développements scientifiques récents, qui permettent une meilleure compréhension du processus d’application tant pour les chercheurs que les agriculteurs, ouvrent la porte à de nombreux développements technologiques. Une présentation des principales bases physiques du processus permet d’éclaircir les diverses options technologiques à la disposition des agriculteurs pour améliorer leurs pratiques en traitement des cultures. En particulier, l’attention est portée sur la trajectoire des gouttes entre la buse et sa cible ainsi que la rétention du produit par les plantes. Ces considérations se traduisent par diverses options technologiques au niveau des agro-équipements et produits de traitement qui doivent être prises en considération pour effectuer les investissements les plus pertinents et choisir les meilleures options lors du traitement. [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 detailPolitiques Architecturales en Belgique
De Visscher, Lisa ULg

Poster (2017, March 10)

The procedures for tenders proposed by the different government architects or the Cellule Architecture in Flanders, Brussels and Wallonia have an important influence on the quality of the process of the ... [more ▼]

The procedures for tenders proposed by the different government architects or the Cellule Architecture in Flanders, Brussels and Wallonia have an important influence on the quality of the process of the project and therefore on its physical result. Comparison and analysis of the different existing procedures. [less ▲]

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See detailUne illustration de multidisciplinarité:"La concertation multidisciplinaire"
Buret, Laetitia ULg

Conference (2017, March 09)

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See detailExercices pratiques de légistique
Grandjean, Geoffrey ULg

Learning material (2017)

Detailed reference viewed: 31 (2 ULg)
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See detailPratiques de coopération entre généralistes et médecins du travail
Vanmeerbeek, Marc ULg

Scientific conference (2017, March 09)

Detailed reference viewed: 22 (0 ULg)