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See detailMulti-instrument overview of the 1-hour pulsations in Saturn's magnetosphere
Palmaerts, Benjamin ULg; Roussos, Elias; Radioti, Aikaterini ULg et al

Conference (2017, March 16)

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See detailPrésentation du projet de thèse : Performance des entreprises et ressources territoriales multi-échelles en Belgique et Wallonie
Wilmotte, Pierre-François ULg

Conference (2017, March 16)

Présentation du projet doctoral dans le cadre du séminaire des doctorants de l'ASRDLF. L'objectif est de présenter le projet mais aussi de mettre en avant les difficultés éventuelles pour recueillir des ... [more ▼]

Présentation du projet doctoral dans le cadre du séminaire des doctorants de l'ASRDLF. L'objectif est de présenter le projet mais aussi de mettre en avant les difficultés éventuelles pour recueillir des conseils et suggestions de doctorants ou d'enseignants-chercheurs. Le projet a été présenté avec les éléments suivants : contexte, questions de recherche, méthodologie, premiers résultats et éléments attendus. [less ▲]

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See detailEnquête sur les pratiques de pâturage en Wallonie: Résultats et conclusions
Lessire, Françoise ULg; Dufrasne, Isabelle ULg

Conference given outside the academic context (2017)

The role of grasslands as a C sink is generally accepted. It is considered that permanent grasslands allow annual C storage rates between 22 and 44 g C/m2/y (Soussana et al., 2010) thereby contributing to ... [more ▼]

The role of grasslands as a C sink is generally accepted. It is considered that permanent grasslands allow annual C storage rates between 22 and 44 g C/m2/y (Soussana et al., 2010) thereby contributing to the mitigation of greenhouse gas (GHG) emissions. Grassland preservation has several other advantages including a decrease in feeding costs (Dillon et al., 2005), a positive effect on cows’ health (e.g.a decrease in lameness) (Burow et al., 2011) and the provision of a positive image to consumers. Despite these arguments, grazing is decreasing in Europe and grasslands are disappearing. A better understanding of grazing practices and of farmers’ expectations could suggest ways of improving these practices and limiting grassland disappearance. As a result, Walloon dairy farmers were surveyed in December 2015 and the preliminary results are presented below. [less ▲]

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See detailCancer in the organ donor
DETRY, Olivier ULg

Conference (2017, March 16)

Organ Donation and Cancer Pr Olivier Detry, Dpt of Abdominal Surgery and Transplantation, University of Liege The risk of transmission of cancer with the transplanted organ has been known since the ... [more ▼]

Organ Donation and Cancer Pr Olivier Detry, Dpt of Abdominal Surgery and Transplantation, University of Liege The risk of transmission of cancer with the transplanted organ has been known since the pioneering years of solid organ transplantation, and is enhanced by immunosuppression and particularly the calcineurin inhibitors. Therefore, classically, potential organ donors with past history of cancer are excluded from donation, with the exception of low-grade malignant tumours of the central nervous system, the skin and the cervix uteri. Despite that policy, every year, some cases of cancer transmission with organ transplantation were regularly reported in transplant medical journals. At the other hand, there is a clear graft shortage, with long organ transplant waiting lists and inacceptable mortality while waiting for a life saving graft. One mean to increase the number of available grafts could be to accept donation from donors with past history of cancer. Several uncertainties remain: what is the risk of cancer transmission with organ transplantation? This risk depends of course of many donor factors, as the staging and the nature of the donor malignant tumour, the oncological management, the delay between the remission and the organ procurement. This risk may also vary according to the type of organ transplanted, as livers and lungs are more prone to bear occult metastases, compared to the hearts for example. In fact, this risk is unknown, and was clearly overestimated by the old registries as the IPTR, and by the various case reports. All modern prospective registries, as from UNOS or from UK transplant, now report a very low rate of cancer transmission when the donor cancer was known and evaluated before organ donation. Undiagnosed or occult cancer transmission with transplantation is clearly another issue that should not be mistaken with the donors with past history of cancer. In most of the recent reported cases of cancer transmission with transplantation, the donor cancer was not diagnosed before and during organ donation. And this risk increases in modern organ transplantation, as we are now accepting older and older donors, particularly in transplantation of the liver, an organ particularly at risk of metastases. Therefore surgical donor exploration is an important step of organ procurement. Body CT could be a tool to diagnose some, but not all, of these tumours. To my view, the risk of cancer transmission with transplantation has to be balanced with the risk of dying on the waiting lists. Donors with active or recent aggressive cancers have to be excluded from donation. Some types of aggressive cancers, as lymphoma or melanoma, are at high risk. In donors with past history of cancer with some years of remission, organ donation should be considered for recipients at high risk of death without a rapid transplantation. Particularly, heart transplantation, an organ with a low risk of cancer transmission but with a severe organ shortage, could benefit from such a policy. [less ▲]

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Peer Reviewed
See detailStatistics of localized phase slips in tunable width planar point contacts
Baumans, Xavier ULg

in Scientific Reports (2017), 7

The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In ... [more ▼]

The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink in-situ the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current I sw needed to trigger an avalanche of events. Furthermore, for an applied current larger than I sw , we unveil the existence of two distinct thermal regimes. One corresponding to efficient heat removal where the constriction and bath temperatures remain close to each other, and another one in which the constriction temperature can be substantially larger than the bath temperature leading to the formation of a hot spot. Considering that the switching current distribution depends on the exact thermal properties of the sample, the identification of different thermal regimes is of utmost importance for properly interpreting the dissipation mechanisms in narrow point contacts. [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 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 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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