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See detailL’ambition climatique de l’Europe est aussi socio-économique
Chapelle, Grégor; de Borchgraeve, François; de Callataÿ, Etienne et al

Article for general public (2014)

Les objectifs climatiques et énergétiques de la Commission européenne sont trop faibles. Inquiets, plusieurs chefs d’entreprises et académiques demandent à notre Premier ministre de plaider, lors du ... [more ▼]

Les objectifs climatiques et énergétiques de la Commission européenne sont trop faibles. Inquiets, plusieurs chefs d’entreprises et académiques demandent à notre Premier ministre de plaider, lors du Conseil européen, pour une politique climat-énergie bien plus ambitieuse. [less ▲]

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See detailLa résilience chez les plus vulnérables au Rwanda
Militery Ngamata, Olivier ULg

Doctoral thesis (2014)

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce ... [more ▼]

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce the poverty of the vulnerable populations and so reach the Millennium Development Goals (MDGs). The different interventions done in the context of social security of the poor people are considered as means of increasing the economy, integrating people in employment market, improving human development thanks to a better access to health and education, and reducing poverty. After the context and justification of the research as well as the methods for data collection, this study focuses primarily on the conceptualization of resilience and connected concepts. Secondly, it scrutinizes the impact of the three programmes of social protection that were developed to reduce poverty of the beneficiaries. The first programme is FARG that supports the survivors of the 1994 genocide against the Tutsi in the domain of education, access to accommodation, medical health and income generating activities. The second programme is Ubudehe-VUP-2020. This one helps very poor households via direct financial transfers, creation of jobs and access to financial services. Girinka is the third programme; it contributes to food improvement, subsistence means and land fertility by supplying a dairy cow to poor families. In third position, this research assesses the achievements of the association of the widows survivors of genocide called - Agahozo (AVEGA) as well as the successes so far reached by the widows beneficiaries. The widows consider AVEGA as an important ‘tutor for resilience’ because it not only deals with their psychological aspects related to the tragedies they experienced but also the promotion and development of economic activities that can supply them with an income for their social reintegration at both economic and social levels. Thus, AVEGA involves a diversity of actors in order to help the widows and implement various income generating activities. Research conducted on the field has targeted, in last position, the most resilient widows. These widows have got support from social protection programmes and AVEGA, in order to involve in income generating activities among which the most developed are agriculture, animal rearing and commerce. All in all, the widows of genocide who were surveyed positively commented the support they get from SPP and AVEGA regarding the reinforcement of their economic resilience. [less ▲]

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See detailContribution à l'amélioration de l'accès à une eau potable de qualité pour les populations de la région nord du Burkina Faso
Some, Issam; Guel, Boubié; Hantson, Anne-Lise et al

Poster (2014, March 19)

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See detailAudiovisual spatial congruence, and applications to 3D sound and stereoscopic video
André, Cédric ULg

Doctoral thesis (2014)

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D ... [more ▼]

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie. The perceptual relevance of such spatial audiovisual coherence is of significant interest. In this thesis, we investigate the possibility of adding spatially accurate sound rendering to regular s-3D cinema. Our goal is to provide a perceptually matched sound source at the position of every object producing sound in the visual scene. We examine and contribute to the understanding of the usefulness and the feasibility of this combination. By usefulness, we mean that the technology should positively contribute to the experience, and in particular to the storytelling. In order to carry out experiments proving the usefulness, it is necessary to have an appropriate s-3D movie and its corresponding 3D audio soundtrack. We first present the procedure followed to obtain this joint 3D video and audio content from an existing animated s-3D movie, problems encountered, and some of the solutions employed. Second, as s-3D cinema aims at providing the spectator with a strong impression of being part of the movie (sense of presence), we investigate the impact of the spatial rendering quality of the soundtrack on the reported sense of presence. The short 3D audiovisual content is presented with three different soundtracks. These soundtracks differ by their spatial rendering quality, from stereo (low spatial coherence) to Wave Field Synthesis (WFS, high spatial coherence). The original stereo version serves as a reference. Results show that the sound condition does not impact on the sense of presence of all participants. However, participants can be classified according to three different levels of presence sensitivity with the sound condition impacting only on the highest level (12 out of 33 participants). Within this group, the spatially coherent soundtrack provides a lower reported sense of presence than the other custom soundtrack. The analysis of the participants' heart rate variability (HRV) shows that the frequency-domain parameters correlate to the reported presence scores. By feasibility, we mean that a large portion of the spectators in the audience should benefit from this new technology. In this thesis, we explain why the combination of accurate sound positioning and stereoscopic-3D images can lead to an incongruence between the sound and the image for multiple spectators. Then, we adapt to s-3D viewing a method originally proposed for 2D images in the literature to reduce this error. Finally, a subjective experiment is carried out to prove the efficiency of the method. In this experiment, an angular error between an s-3D video and a spatially accurate sound reproduced through WFS is simulated. The psychometric curve is measured with the method of constant stimuli, and the threshold for bimodal integration is estimated. The impact of the presence of background noise is also investigated. A comparison is made between the case without any background noise and the case with an SNR of 4 dBA. Estimates of the thresholds and the slopes, as well as their confidence intervals, are obtained for each level of background noise. When background noise is present, the point of subjective equality (PSE) is higher (19.4° instead of 18.3°) and the slope is steeper (-0.077 instead of -0.062 per degree). Because of the overlap between the confidence intervals, however, it is not possible to statistically differentiate between the two levels of noise. The implications for the sound reproduction in a cinema theater are discussed. [less ▲]

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See detailArtificial Abelian gauge potentials induced by dipole-dipole interactions between Rydberg atoms
Cesa, Alexandre ULg; Martin, John ULg

Poster (2014, March 19)

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field ... [more ▼]

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atom-atom and atom-field interactions give rise to nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole and van der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion. [less ▲]

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See detailEtude des possibilités de culture de Jatropha curcas L. dans la région de Kinshasa en République Démocratique du Congo (RDC)
Minengu Mayulu, Jean de Dieu ULg

Doctoral thesis (2014)

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances ... [more ▼]

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances préalables des conditions de rentabilité et des techniques de production les mieux adaptées aux contextes locaux. L’objectif du présent travail est de lever cette lacune pour la région de Kinshasa en apportant des réponses aux principales questions qui conditionnent la mise au point d’un agrosystème durable basé sur la culture de J. curcas. Pour atteindre cet objectif, les performances d’une plantation pilote installée à proximité de la cité de Mbankana en décembre 2007 ont été évaluées et quatre essais ont été réalisés à partir de juillet 2009 à janvier 2013 dans deux sites représentatifs des conditions du Plateau des Batéké (Mbankana et Mongata) et à proximité de la rivière N’sele dans la banlieue de Kinshasa. Les résultats obtenus montrent que les facteurs de l’environnement et les pratiques culturales ont une influence sur le rendement en graines et en huile de J. curcas. Les faibles rendements obtenus, le coût très élevé des intrants (engrais et insecticides) et les faibles quantités de graines récoltées par journée de travail sont les principales causes de l’absence de rentabilité de la culture pure de J. curcas dans les premières plantations mises en place avec du matériel végétal local subspontané. Les principaux insectes ravageurs de J. curcas dans la zone d’étude sont les grillons Brachytrupes membranaceus Drury (Orthoptera, Grillidae) qui s’attaquent aux jeunes plantes lors de leur mise en place en saison pluvieuse (octobre à décembre), les chenilles mineuses de feuilles Stomphastis thraustica Meyrick (Lepidoptera, Gracillariidae), les chrysomèles Aphthona sp. (Coleoptera, Chrysomelidae) qui consomment le limbe des feuilles et les bourgeons, ainsi que les punaises à bouclier Calidea sp. (Heteroptera, Scutelleridae) qui causent des dégâts aux fleurs et aux capsules. Parmi ceux-ci, la chrysomèle est pour l’instant le ravageur le plus dommageable. En l’absence de traitements insecticides, le niveau des pertes de rendement occasionnées par ces insectes ravageurs atteignent 90% en culture pure sur le Plateau des Batéké. La gravité des dégâts des insectes ravageurs sur J. curcas est plus élevée en culture pure (>60%) que quand il est associé à d’autres cultures annuelles (<45%). La mise au point de méthodes durables de contrôle des ravageurs est une des conditions indispensables à l’installation de plantations de J. curcas dans la région de Kinshasa. L’application de la taille, de la fertilisation minérale et de la couverture du sol avec Stylosanthes guianensis (Aublet) Swartz, permet d’améliorer significativement le rendement en graines de J. curcas Onze écotypes de J. curcas, collectés dans les différentes régions de la RDC et mis en culture au Plateau des Batéké, ont montré des différences significatives en termes du développement végétatif et des rendements en graines et en huile. Le rendement moyen obtenu en 3eme année de production par l’écotype le plus productif (Panu : 473,1±3,6 kg de graines sèches ha-1) était près de 7 fois plus élevé que le rendement de l’écotype qui a produit le moins (Ilebo : 68,6±3,6 kg ha-1). Contrairement à ce qui était annoncé dans la littérature, le temps nécessaire pour l’entrée en pleine production de J. curcas en conditions tropicales humides est supérieur à 5 ans. Il n'est pas possible de déterminer sur base de nos résultats, le niveau exact de rendement qui sera obtenu quand les plantes entreront en pleine production. Quel que soit celui-ci, le coût très élevé de la main d’œuvre nécessaire à la collecte des graines de J. curcas et au désherbage limite fortement les perspectives de rentabilité de la culture pure dans la région de Kinshasa. Dans les zones enclavées du pays, où le coût de la main d’œuvre est moindre et où le prix du diesel est plus élevé, la production de J. curcas peut constituer l’une des solutions pour résoudre les problèmes d’accès à l’énergie. [less ▲]

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See detailImpact des matériaux biosourcés sur le climat intérieur : Un outil de calcul flexible à l'échelle de la pièce
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Conference (2014, March 19)

L'impact de l'utilisation de matériaux d'origine végétale sur le climat intérieur, et donc sur le confort des occupants ainsi que la performance énergétique du bâtiment, n'est établi que partiellement ... [more ▼]

L'impact de l'utilisation de matériaux d'origine végétale sur le climat intérieur, et donc sur le confort des occupants ainsi que la performance énergétique du bâtiment, n'est établi que partiellement. Ces produits présentent des propriétés hygroscopiques et capillaires causant des phénomènes spécifiques liés aux changements de phase dynamiques au sein de la matrice poreuse. Les modèles mathématiques utilisés pour étudier leur comportement hygrothermique de manière détaillée sont souvent des modèles de paroi (dits modèles HAM - Heat Air Moisture). Cela sous-tend qu'ils nécessitent d'imposer des conditions aux limites à toutes les frontières de l'élément étudié, et ne permettent donc pas de connaître les flux de chaleur et de masse réels qu'offrent l'assemblage de matériaux vers le volume d'air intérieur. Pour y accéder, il convient d'intégrer ces modèles à la description de bilans thermique et hydrique de zones. Dans cette communication, nous présentons un modèle hygrothermique capable de simuler l'évolution temporelle du climat intérieur d'une ou de plusieurs pièces ("zones thermiques"). Il est composé d'un module HAM basé sur des équations aux dérivées partielles et caractérisant les transferts dans les matériaux de construction et développé au sein de l'environnement numérique COMSOL Multiphysics. Les équations qui le composent sont flexibles et facilement adaptables au cas expérimental modélisé ainsi qu'aux propriétés des matériaux composant les parois. En outre, on y trouve un traitement complet des phénomènes de changement de phase qui prend en compte l'impact de la température sur la capacité de stockage d'humidité du matériau. Ce premier module, est couplé à un outil caractérisant les bilans chaleur/masse au niveau de la zone à l'aide d'équations aux dérivées ordinaires. Le couplage des modèles est effectué au sein de SIMULINK, un outil de MATLAB destiné à l'étude des systèmes dynamiques. Nous appliquons ensuite ce modèle à l'étude d'un mur en ballots de paille séparant une enceinte climatique de grande taille en deux volumes d'air. Les données d'une expérience simple, un choc thermique imposé à un des volumes d'air, sont comparées aux sorties du modèle numérique. [less ▲]

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See detailL'impiété dans les rapports sociaux en Grèce antique : le cas des étrangers
Delli Pizzi, Aurian ULg

Scientific conference (2014, March 18)

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See detailDeuxième mission de terrain dans la reserve de Yangambi
de Haulleville, Thalès ULg; Bogaert, Jan ULg; Beeckman, Hans

Scientific conference (2014, March 18)

Presentation of Thales de Haulleville's planned fieldwork during his second field mission.

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See detailInfluence of dipole-dipole interactions decoherence-free states
Damanet, François ULg; Martin, John ULg

Poster (2014, March 18)

Decoherence, known as the consequence of the coupling of any quan- tum system to its environment, causes information loss in the system and represents a major problem in the physical realization of quan ... [more ▼]

Decoherence, known as the consequence of the coupling of any quan- tum system to its environment, causes information loss in the system and represents a major problem in the physical realization of quan- tum computers [1]. Decoherence-Free States (DFS) are considered as a possible solution to this problem. A set of trapped cold atoms placed in a DFS state will be immune against decoherence due to sponta- neous emission. However, because of dipole-dipole interactions between atoms, induced dephasing effects are likely to destroy the coherence and drive the system out of its DFS [1-2]. In this work, we study nu- merically the dynamics of a set of two-level atoms initially in a DFS with respect to dissipative processes by solving the master equation in- cluding both dissipative dynamics and dipole dipole interactions. We focus our attention on the influence of dipolar coupling on the radiated energy rate and coherence of the system as in [3]. In particular, by av- eraging over many realizations of close randomly distributed atomic positions, we show the formation of a superradiant-like pulse and we study its properties as a function of the dipolar coupling strength. [1] D. A. Lidar & K. B. Whaley, Lectures Notes in Phys., Vol. 622, p83-120, Springer (2003). [2] M. Gross & S. Haroche, Physics reports 93, 301-396 (1982). [3] W. Feng, Y. Li & S. -Y. Zhu, arXiv :1302.0957. (2013). [less ▲]

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See detailConclusion et mise en perspective des présentations et débats de la matinée
Halleux, Jean-Marie ULg

Conference given outside the academic context (2014)

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See detailPsychopathologie et philosophie du visage en prison
Englebert, Jérôme ULg

Scientific conference (2014, March 18)

Detailed reference viewed: 16 (2 ULg)
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See detailDistributed control of electromechanical oscillations in very large-scale electric power systems
Wang, Da ULg

Doctoral thesis (2014)

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different ... [more ▼]

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different damping devices, like Power System Stabilizers (PSSs), Thyristor Controlled Series Compensators (TCSCs), and so on, are installed to damp these oscillations. This thesis proposes a trajectory-based supplementary control to improve damping effects of existing controllers, which treats damping control as a multi-step optimization control problem with discrete dynamics and costs. At each control time, it collects current system states, solves the optimal control problem and superimposes the calculated supplementary inputs on the outputs of existing damping controllers, in order to enhance the damping. These supplementary signals are continuously updated, which allows to adaptively adjust and coordinate a subset of existing damping controllers, and eventually all of them. Two kinds of methods, Model Predictive Control (MPC) and Reinforcement Learning (RL), are used to embody the proposed supplementary damping control. Firstly, a fully centralized MPC scheme is designed based on a linearized, discrete, complete state space model. Its performances are evaluated both in ideal conditions and considering realistic state estimation errors, and computation and communication delays. The effects of the number and type of available damping controllers are also studied. This scheme is further extended into a distributed scheme with the aim of making it more viable for very large-scale or multi-area systems. Different ways of decoupling and coordinating between subsystems are analyzed. Finally, a robust hierarchical multi-area MPC scheme is proposed, introducing a second layer of MPC based controllers at the level of individual power plants and transmission lines. Secondly, a tree-based batch mode RL algorithm is applied to carry on the proposed supplementary damping control. Using a set of dynamic and reward four-tuples, it constructs an approximation of the optimal $Q$-function over a given temporal horizon. The actions greediest with respect to the $Q$-function are applied as supplementary signals to existing damping controllers. The scheme is firstly tested on a single generator, and then on multiple generators. Different reward signals and damping levels are also considered. Finally, the combined control effects of MPC and RL are investigated. [less ▲]

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See detailCFD-based Compartment model for description of mixing in bioreactors
Delafosse, Angélique ULg; Calvo, Sébastien ULg; Collignon, Marie-Laure ULg et al

in Chemical Engineering Science (2014), 106

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can ... [more ▼]

In most bioprocesses, it is fundamental to accurately predict the hydrodynamics behavior of bioreactors of different size and its interaction with the biological reaction. Computational Fluid Dynamics can provide detailed modeling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of “Compartment” or “Network-of-zones” model which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow complexity. To overcome the limitations of these two methods, a solution is to combine compartment modeling and CFD simulations. The aim of this study is to propose a compartment model where the flow rates between two adjacent compartments are easily computed from the velocity fields obtained by CFD. The mixing evolution predicted by the CFD-based compartment model have been then compared with mixing experiment results. Unlike a CFD mixing simulation and a classical compartment model, the CFD-based compartment model proposed in this work reproduces with a good accuracy the spatial distribution of concentrations during the mixing process and this, without any adjustable parameters. [less ▲]

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