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See detailControlled flow of smart powders
Lumay, Geoffroy ULg; Vandewalle, Nicolas ULg

in Physical Review E (2008), 78(6),

The flow properties of powders are mainly due to the interplay of cohesive forces and intergrain frictional forces. We have experimentally investigated a "smart granular system" for which the ... [more ▼]

The flow properties of powders are mainly due to the interplay of cohesive forces and intergrain frictional forces. We have experimentally investigated a "smart granular system" for which the interparticle cohesion can be tuned by a magnetic field B. We show that the rheological features of such a system can be controlled. Indeed, the granular flow can be controlled or even stopped by the magnetic field. Depending on the orientation of B, different dynamical regimes can be obtained like a "dry liquid state" forming conical droplets as well as a "layered soft state". Scaling lows are given for the flow rate outside a funnel as a function of B and for the stopping threshold of the flow as a function of the funnel output diameter D. From this analysis, it appears that the flowing properties are related to the dimensionality of the magnetic aggregates. [less ▲]

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See detailEnseigner la chimie en 1ère année de bachelier : Témoignages et réflexions
Colaux, Catherine ULg

Scientific conference (2008, December)

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See detailApproche qualité pour améliorer l’accrochage scolaire
Plunus, Ghislain ULg; Gilles, Jean-Luc ULg; Polson, Delphine ULg et al

in Education Canada (2008), 48(5), 27-29

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See detailLBG-SQUARE - Fault Tolerant, Locality-Aware Co-allocation in P2P Grids
Dethier, Gérard ULg; Briquet, Cyril ULg; Marchot, Pierre ULg et al

in Huang, Zhiyi; Xu, Zhiwei; Rountree, Nathan (Eds.) et al Ninth International Conference On Parallel And Distributed Computing, Applications And Technologies : PDCAT 2008 (2008, December)

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily ... [more ▼]

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily-communicating, long-running Tasks. They thus require co-allocation of multiple reliable resources for extended periods of time. P2P Grids are totally decentralized and provide on-demand, transparent access to edge resources, e.g. Internet-connected, non-dedicated desktop computers. A P2P Grid has the potential to provide access to a large number of resources at the fraction of the cost of a dedicated cluster. However, edge resources are heterogeneous in performance and intrinsically unreliable: Task execution failures are common due to resource preemption or resource failure. Furthermore, P2P Grid schedulers usually target sets of independent computational Tasks, i.e. so-called Bags of Tasks applications. It is therefore not trivial to deploy and run an Iterative Stencil application on a P2P Grid. Checkpointing is a common fault-tolerance mechanism in High Performance Distributed Computing, often based on a centralized architecture. Locality-aware co-allocation in P2P Grids has been recently investigated. Checkpointing and locality-aware co-allocation yet have to be integrated in P2P Grids. We propose to provide co-allocation through an existing middleware-level Bag of Tasks scheduling mechanism. We also introduce a layer of fault-tolerance for the Iterative Stencils that relies on a scalable, application-level, P2P checkpointing mechanism. Finally, LBG-SQUARE is described. This software results from the combination of a specific Iterative Stencil application (a Computational Fluid Dynamics simulation software called LaBoGrid) with a P2P Grid middleware (Lightweight Bartering Grid). [less ▲]

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See detailPanorama des imaginaires des jeunes au sujet de la société idéale
Brahy, Rachel ULg

Article for general public (2008)

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See detailest-il possible d’intégrer la fragilité gériatrique dans le risque chirurgical ?
Petermans, Jean ULg

in Revue Médicale de Liège (2008), 63(12), 722-728

Frailty in the elderly is an important factor of morbidity, particularly in the setting of surgery. The various pathologies that can lead to a functional decline are well known. The risk of mortality and ... [more ▼]

Frailty in the elderly is an important factor of morbidity, particularly in the setting of surgery. The various pathologies that can lead to a functional decline are well known. The risk of mortality and morbidity should be assessed as a function of the nature of the surgical procedure and of the disease for which it is required; the factors of severity, the predictable duration of the procedure, and the expected blood losses must also be taken into account. The thrombo-embolic risk should finally be considered. In the elderly, one may say that the functional risk matters more than the vital risk. Frailty must be integrated into the risk assessment; however, further studies are needed to better determine the impact of that new concept. Undoubtedly, the cognitive and nutritional status are of main importance. A better knowledge of the risks should lead to validate specific interventions that could help to prevent surgical complications, shorten the length of hospital stay, and protect the self-sufficiency of the aged. [less ▲]

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See detailResearch and Education Activities in Electric Power Systems at the University of Liège
Wehenkel, Louis ULg; Ernst, Damien ULg; Rousseaux, Patricia ULg et al

in Revue E Tijdschrift (2008), (4), 54-59

This paper presents research and education activities of the power systems group of the Department of Electrical Engineering and Computer Science of the University of Liège. These activities cover power ... [more ▼]

This paper presents research and education activities of the power systems group of the Department of Electrical Engineering and Computer Science of the University of Liège. These activities cover power systems stability, security, reliability, and markets, within the contexts of expansion planning, operation planning and real-time operation and automatic control. The paper also reviews the international collaborations of the team. [less ▲]

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See detailLe projet PEGASE
Stubbe, Marc; Karoui, Karim; Van Cutsem, Thierry ULg et al

in Revue E Tijdschrift (2008), (4), 37-41

A group of Transmission System Operators (TSO’s), expert companies and leading research centers in power system analysis and applied mathematics, under the coordination of Tractebel Engineering, has ... [more ▼]

A group of Transmission System Operators (TSO’s), expert companies and leading research centers in power system analysis and applied mathematics, under the coordination of Tractebel Engineering, has joined to develop methodologies and software tools able to monitor, simulate and analyze the European Transmission Network (ETN). This project called PEGASE is part of the 7th Framework Programme of the European Commission. Its budget is about 13 MEUR. It started in September 2008 and will last for 4 years. It will define the architecture, data flows and algorithms of an ETN state estimator making use of emerging technologies like the GPS-synchronized Phasor Measurement Units (PMUs). Giving access to the state of the ETN to each TSO would improve dramatically their coordination provided that new ideas to display huge amounts of ETN data are proposed. This is also part of the research. The static simulation of the ETN requires to take into account the various operating rules and control practices of each national grid. New algorithms will be developed, based on optimization techniques and sound engineering judgment. The dynamic simulation of the ETN is of paramount importance for better control and security assessment of this large-scale system. PEGASE will build a prototype of a simulation engine capable of reproducing all kinds of behavior of the ETN. Such an engine will be designed to play extreme scenarios up to the complete black-out of Europe and its subsequent restoration. It will require algorithmic breakthroughs and advanced computer architecture. It will be embedded in a mock-up of a real time dispatcher training simulator. Simplified dynamic simulation tools, able to run much faster than real time, will be developed for on-line security assessment. If the main challenge of the project remains the size and the heterogeneity of the ETN, special attention will be paid to modeling methodology. Component models have to face the complexity introduced by IT and power electronic technologies presently used in power systems. Standard model libraries reach some limits and a greater modeling flexibility is needed to introduce new devices in software tools or exchange models between operators. [less ▲]

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See detailCoordination on Lie groups
Sarlette, Alain ULg; Bonnabel, Silvère; Sepulchre, Rodolphe ULg

in Proceedings of the 47th IEEE Conference on Decision and Control (2008, December)

This paper studies the coordinated motion of a group of agents evolving on a Lie group. Left- or right-invariance with respect to the absolute position on the group lead to two different characterizations ... [more ▼]

This paper studies the coordinated motion of a group of agents evolving on a Lie group. Left- or right-invariance with respect to the absolute position on the group lead to two different characterizations of relative positions and two associated definitions of coordination (fixed relative positions). Conditions for each type of coordination are derived in the associated Lie algebra. This allows to formulate the coordination problem on Lie groups as consensus in a vector space. Total coordination occurs when both types of coordination hold simultaneously. The discussion in this paper provides a common geometric framework for previously published coordination control laws on SO(3), SE(2) and SE(3). The theory is illustrated on the group of planar rigid motion SE(2). [less ▲]

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See detailLes fondements d'une intervention précoce
Bednarek, Stéphanie ULg; Absil, Gaëtan ULg; Vandoorne, Chantal ULg et al

Report (2008)

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See detailBrigitte Bardot, Shakespeare und der Alte Antonio
Vanden Berghe, Kristine ULg

Article for general public (2008)

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See detailTopology and generalized shape optimisation: why stress constraints are so important?
Duysinx, Pierre ULg; Van Miegroet, Laurent ULg; Lemaire, Etienne ULg et al

in International Journal of Simulation & Multidisciplinary Design Optimization (2008), 2(4), 253-258

The paper continues along the work initiated by the authors in taking into account stress constraints in topology optimization of continuum structures. Revisiting some of their last developments in this ... [more ▼]

The paper continues along the work initiated by the authors in taking into account stress constraints in topology optimization of continuum structures. Revisiting some of their last developments in this field, the authors point out the importance of considering stress constraints as soon as the preliminary design phase, that is, to include stress constraints in the topology optimization problem in order to get the most appropriate structural lay-out. Numerical applications that can be solved using these new developments make possible to exhibit interesting results related to the specific nature of strength based structural lay out for maximum strength compared to maximum stiffness. This particular character of stress design is clearly demonstrated in two kinds of situations: once several load cases are considered and when unequal stress limits in tension and compression are involved. [less ▲]

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See detailTable ronde : Les valeurs sous-jacentes au Décret-missions et au contrat pour l'école
Beckers, Jacqueline ULg; Florkin, Étienne; Leroy, Jacky

in Puzzle (2008), 25

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See detailProduction of alarm pheromone in aphids and perception by ants and natural enemies
Verheggen, François ULg

Doctoral thesis (2008)

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm ... [more ▼]

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm behaviours. This PhD thesis aims to better understand how aphids manage their production and emission of alarm pheromone (Chapter IV). We also wanted, in a second step, to improve our knowledge on the roles that Eßf could play in the relationships that aphids have with their predators (Chapter V) and tending ants (Chapter VI), in order to better pinpoint the problem in this very tough context. The aphid predators have indeed a real advantage to be able to use the odorant cues emitted by their prey, to locate them and to select an adequate oviposition site. Ants establish with certain aphid species mutualistic relationships, which occurrence could be facilitated by the use of aphids’ odours. In Chapter IV, we have highlighted that aphid colonies non subjected to attack by predators release constantly small quantities of Eßf in their headspace, which means that this molecule could have additional roles than just acting as an alarm pheromone. In a second study, we demonstrated that the release of Eßf was not contagious, and therefore that a non stressed aphid receiving the alarm signal does not release additional Eßf. Since the production of alarm pheromone is likely to entail physiological cost, we tested and validated the hypothesis that aphids regulate their Eßf production according to their social environment. In Chapter V, we studied the ability of the hoverfly predator Episyrphus balteatus (Diptera, Syrphidae) to be used as biological control agent against aphids infesting tomato plants (Lycopersicon esculentum). After identifying the odours emitted by aphid infested plants, we have demonstrated that although this Diptera is able to perceive all the odours released by the system, it mainly uses Eßf to select its oviposition site. However, the E. balteatus larvae are not adapted to the architecture of tomato plants. We also showed that the Asian ladybeetle Harmonia axyridis (Coleoptera, Coccinellidae) olfaction was adapted to the perception of Eßf and that this beetle is also attracted by this sesquiterpene. Finally, in Chapter VI, we characterized the benefits accruing to aphid populations that have established mutualistic relationships with Lasius niger (Hymenoptera, Formicidae), and have demonstrated the role of Eßf and honeydew, respectively in locating aphid colonies and in the persistence of the mutualism. [less ▲]

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See detailElements of neonatal neurology
Battisti, Oreste ULg

Learning material (2008)

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See detailcarnet de pédiatrie en Afrique: Eléments de pathologie circulatoire néonatale
Battisti, Oreste ULg

Learning material (2008)

Cours de pathologie circulatoire néonatale pour le master complémentaire en pédiatrie

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See detailA Self-Organized clustering scheme for overlay networks
Cantin, François ULg; Gueye, Cheikh Ahmadou Bamba ULg; Kaafar, Mohamed Ali ULg et al

in Lecture Notes in Computer Science (2008, December), 5343

Hierarchical approaches, where nodes are clustered based on their network distances, have been shown to allow for robust and scalable topology-aware overlays. Moreover, recent research works have shown ... [more ▼]

Hierarchical approaches, where nodes are clustered based on their network distances, have been shown to allow for robust and scalable topology-aware overlays. Moreover, recent research works have shown that cluster-based deployments of Internet Coordinates Systems (ICS), where nodes estimate both intra-cluster and inter-cluster distances, do mitigate the impact of Triangle Inequality Violations (TIVs) on the distance predictions, and hence offer more accurate internet latency estimations. To allow the construction of such useful clusters we propose a self-organized distributed clustering scheme. For better scalability and efficiency, our algorithm uses the coordinates of a subset of nodes, known by running an ICS system, as first approximations of node positions. We designed and evaluated two variants of this algorithm. The first one, based on some cooperation among nodes, aims at reducing the expected time to construct clusters. The second variant, where nodes are selfish, aims at reducing the induced communication overhead. [less ▲]

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See detailL'astronomie dans le monde
Manfroid, Jean ULg

Article for general public (2008)

Chang'e 1; Météorites; Aurore mystérieuse sur Saturne; CoRoT; XO-3b; Disque de gaz autour d'étoiles jeunes; Hauméa; L'origine de Titan et de son atmosphère; Jupiter; Météorites; Le Crabe vu par Chandra; L ... [more ▼]

Chang'e 1; Météorites; Aurore mystérieuse sur Saturne; CoRoT; XO-3b; Disque de gaz autour d'étoiles jeunes; Hauméa; L'origine de Titan et de son atmosphère; Jupiter; Météorites; Le Crabe vu par Chandra; L'univers en UV; Images d'exoplanètes ?; Epsilon Eridani; [less ▲]

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