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See detailClassification automatique d'images par arbres de d́ecision
Marée, Raphaël ULg

Doctoral thesis (2005)

The work presented in this thesis is motivated by the problem of automatic image classification. Image classification methods seek to automatically classify previously unseen images using databases of ... [more ▼]

The work presented in this thesis is motivated by the problem of automatic image classification. Image classification methods seek to automatically classify previously unseen images using databases of labeled images provided by human experts. The main contribution of this thesis is a novel approach for image classification that has been shown to perform well on a variety of tasks. It uses some recent machine learning algorithms based on ensembles of decision trees that we applied directly on pixel values. We combine it with techniques of random extraction and transformation of subwindows from images so as to improve robustness to certain image transformations. The method has been evaluated on 7 publicly available datasets corresponding to various image classification tasks: recognition of handwritten digits, faces, 3D objects, textures, buildings, themes, or landscapes. Some of these datasets contain images representing widely varying conditions: occlusions, cluttered background, illumination, viewpoint, orientation, and scale changes. The accuracy of our method is generally comparable with the state of the art and it is particularly attractive in terms of computational efficiency. [less ▲]

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See detailDecision Trees and Random Subwindows for Object Recognition
Marée, Raphaël ULg; Geurts, Pierre ULg; Piater, Justus ULg et al

in ICML workshop on Machine Learning Techniques for Processing Multimedia Content (MLMM2005) (2005)

In this paper, we compare five tree-based machine learning methods within a recent generic image classification framework based on random extraction and classification of subwindows. We evaluate them on ... [more ▼]

In this paper, we compare five tree-based machine learning methods within a recent generic image classification framework based on random extraction and classification of subwindows. We evaluate them on three publicly available object recognition datasets (COIL-100, ETH-80, and ZuBuD). Our comparison shows that this general and conceptually simple framework yields good results when combined with ensemble of decision trees, especially when using Tree Boosting or Extra-Trees. The latter is also particularly attractive in terms of computational efficiency. [less ▲]

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See detailAdvanced particle characterization for improved understanding of cold spray coating quality
Pirard, Eric ULg; Campana, Florent; Janssen, Jean-Pierre

in Pawlowski, Lech (Ed.) 2e Rencontres Int. Projection Thermique (2005)

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See detailRobustness of Planar Shape Descriptors of Particles
Pirard, Eric ULg; Dislaire, Godefroid

in Chung, C.-F. (Ed.) Proceedings Mathematical Geology Congress (2005)

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See detailSolution structure of human prolactin
Teilum, K.; Hoch, J. C.; Goffin, Vincent et al

in Journal of Molecular Biology (2005), 351(4), 810-23

We report the solution structure of human prolactin determined by NMR spectroscopy. Our result is a significant improvement over a previous structure in terms of number and distribution of distance ... [more ▼]

We report the solution structure of human prolactin determined by NMR spectroscopy. Our result is a significant improvement over a previous structure in terms of number and distribution of distance restraints, regularity of secondary structure, and potential energy. More significantly, the structure is sufficiently different that it leads to different conclusions regarding the mechanism of receptor activation and initiation of signal transduction. Here, we compare the structure of unbound prolactin to structures of both the homologue ovine placental lactogen and growth hormone. The structures of unbound and receptor bound prolactin/placental lactogen are similar and no noteworthy structural changes occur upon receptor binding. The observation of enhanced binding at the second receptor site when the first site is occupied has been widely interpreted to indicate conformational change induced by binding the first receptor. However, our results indicate that this enhanced binding at the second site could be due to receptor-receptor interactions or some other free energy sources rather than conformational change in the hormone. Titration of human prolactin with the extracellular domain of the human prolactin receptor was followed by NMR, gel filtration and electrophoresis. Both binary and ternary hormone-receptor complexes are clearly detectable by gel filtration and electrophoresis. The binary complex is not observable by NMR, possibly due to a dynamic equilibrium in intermediate exchange within the complex. The ternary complex of one hormone molecule bound to two receptor molecules is on the contrary readily detectable by NMR. This is in stark contrast to the widely held view that the ternary prolactin-receptor complex is only transiently formed. Thus, our results lead to improved understanding of the prolactin-prolactin receptor interaction. [less ▲]

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See detailInternal energy and fragmentation of ions produced in electrospray sources
Gabelica, Valérie ULg; De Pauw, Edwin ULg

in Mass Spectrometry Reviews (2005), 24(4), 566-587

This review addresses the determination of the internal energy of ions produced by electrospray ionization (ESI) sources, and the influence of the internal energy on analyte fragmentation. A control of ... [more ▼]

This review addresses the determination of the internal energy of ions produced by electrospray ionization (ESI) sources, and the influence of the internal energy on analyte fragmentation. A control of the analyte internal energy is crucial for several applications of electrospray mass spectrometry, like structural studies, construction of reproducible and exportable spectral libraries, analysis of non-covalent complexes. Sections II and III summarize the Electrospray mechanisms and source design considerations which are relevant to the problem of internal energy, and Section IV gives an overview of the interrelationships between ion internal energy, reaction time scale, and analyte fragmentation. In these three sections we tried to make the most important theoretical elements understandable by all ESI users, and their understanding requires a minimal background in physical chemistry. We then present the different approaches used to experimentally determine the ion internal energy, as well as various attempts in modeling the internal energy uptake in electrospray sources. Finally, a tentative comparison between electrospray and other ionization sources is made. As the reader will see, although many reports appeared on the subject, the knowledge in the field of internal energy of ions produced by soft ionization sources is still scarce, because of the complexity of the system, and this is what makes this area of research so interesting. The last section presents some perspectives for future research. [less ▲]

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See detailAscididemin and meridine stabilise G-quadruplexes and inhibit telomerase in vitro
Guittat, Lionel; De Cian, Anne; Rosu, Frédéric ULg et al

in Biochimica et Biophysica Acta - General Subjects (2005), 1724(3), 375-384

Ascididemin and Meridine are two marine compounds with pyridoacridine skeletons known to exhibit interesting antitumour activities. These molecules have been reported to behave like DNA intercalators. In ... [more ▼]

Ascididemin and Meridine are two marine compounds with pyridoacridine skeletons known to exhibit interesting antitumour activities. These molecules have been reported to behave like DNA intercalators. In this study, dialysis competition assay and mass spectrometry experiments were used to determine the affinity of ascididemin and meridine for DNA structures among duplexes, triplexes, quadruplexes and single-strands. Our data confirm that ascididemin and meridine interact with DNA but also recognize triplex and quadruplex structures. These molecules exhibit a significant preference for quadruplexes over duplexes or single-strands. Meridine is a stronger quadruplex ligand and therefore a stronger telomerase inhibitor than ascididemin (IC50= 11 and > 80 mu M, respectively in a standard TRAP assay). (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailFast gas-phase hydrogen/deuterium exchange observed for a DNA G-quadruplex
Gabelica, Valérie ULg; Rosu, Frédéric ULg; Witt, Matthias et al

in Rapid Communications in Mass Spectrometry : RCM (2005), 19(2), 201-208

The gas-phase hydrogen/deuterium (H/D) exchange kinetics of DNA G-quadruplexes has been investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). The quadruplex [(TGGGGT)(4 ... [more ▼]

The gas-phase hydrogen/deuterium (H/D) exchange kinetics of DNA G-quadruplexes has been investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). The quadruplex [(TGGGGT)(4).3NH(4)(+)] undergoes very fast H/D exchange, in both the positive and in the negative ion modes, compared to DNA duplexes and other quadruplexes tested, and compared to the corresponding single-stranded TGGGGT. Substitution of NH4+ for K+ did not alter this fast H/D exchange, indicating that the hydrogens of the ammonium ions are not those exchanged. However, stripping of the interior cations of the quadruplex by source collision-induced dissociation (CID) in the positive ion mode showed that the presence of the inner cations is essential for the fast exchange to be possible. Molecular dynamics simulations show that the G-quadruplex is very rigid in the gas phase with NH4+ ions inside the tetrads. We suggest that the fast H/D exchange is favored by this rigid quadruplex conformation. This example illustrates that the concept that compact DNA structures exchange H for D slower than unfolded ones is a misconception. Copyright (C) 2004 John Wiley Sons, Ltd. [less ▲]

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See detailEnlèvement international d’enfants- La pratique des juridictions belges
Collienne, Fleur ULg; Wautelet, Patrick ULg

in Wautelet, Patrick (Ed.) Actualités du contentieux familial international (CUP) (2005)

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See detailApplication des méthodes d'analyse stochastique à l’étude des effets du vent sur les structures du génie civil
Denoël, Vincent ULg

Doctoral thesis (2005)

In the civil engineering field, the analysis of structures subjected to wind loading is generally based on several hypotheses. Their justification is often fuzzy and they are usually postulated in order ... [more ▼]

In the civil engineering field, the analysis of structures subjected to wind loading is generally based on several hypotheses. Their justification is often fuzzy and they are usually postulated in order to apply simplified mathematics. These hypotheses allow the resolution to be run in a gaussian context. This work aims at presenting and applying an analysis which allows accounting for the usually neglected terms of the loading. When studying multi degree of freedom structures, other simplifications concerning the coupling effects between modes are generally formulated. These conditions are also approached and several solutions to take them (eventually partially) into account are proposed. From the simplest analysis of a single degree of freedom system subjected to a simple aerodynamic loading, this work presents more and more complex structures. The last step is to present to developments necessary to analyse a real structure. The developments will allow to analyse a linear 3-D structure subjected to a 3-D aerodynamic field whose non linear characteristics are taken into account. These non linear effects can come from the quadratic terms in the expression of the turbulence and from the non linearity of the aerodynamic coefficients in terms of the wind angle of attack. [less ▲]

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See detailFuzzy k-NN applied to moulds detection
Kuske, Martyna; Rubio, R.; Romain, Anne-Claude ULg et al

in Sensors and actuators. B, Chemical (2005), 106(1), 52-60

The possibility to detect Aspergillus versicolor growing on different building materials by a metal oxide sensor array is studied. Results show that an accurate classification rate of 89 +/- 3% can be ... [more ▼]

The possibility to detect Aspergillus versicolor growing on different building materials by a metal oxide sensor array is studied. Results show that an accurate classification rate of 89 +/- 3% can be obtained combining an extended linear discriminant analysis plus a fuzzy k-NN classifier. The classification ability of the classifier is assessed within the dataset by crossvalidation and also in a second dataset collected 5 months later. There is a slight decrease in the classification performance for all the algorithms, being the most sensitive the most accurate one. [less ▲]

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See detailMicrobial volatile organic compounds as indicators of fungi. Can an electronic nose detect fungi in indoor environments?
Kuske, Martyna; Romain, Anne-Claude ULg; Nicolas, Jacques ULg

in Building and Environment (2005), 40(6), 824-831

The paper presents a review of several studies on the detection of microbial volatile organic compounds (MVOCs) considered as indicators of fungal contamination. As fungi produce specific profiles, or ... [more ▼]

The paper presents a review of several studies on the detection of microbial volatile organic compounds (MVOCs) considered as indicators of fungal contamination. As fungi produce specific profiles, or fingerprints of volatile compounds, the electronic nose technology is a very promising opportunity for rapid and non costly detection of fungi in buildings. E-noses are able to distinguish between mouldy and non-mouldy samples, and also to recognise certain species of fungi. However, two limiting factors may appear decisive for employment of electronic noses in indoor fungi detection: low concentrations of MVOCs and presence of interfering substances in indoor environments. [less ▲]

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See detailApprentissage lexical et généralisation chez les enfants retardés mentaux
Elbouz, Mouna; Comblain, Annick ULg

in Groosmann, F.; Paveau, M. A.; Petit, G. (Eds.) Didactique du lexique : langue, cognition, discours (2005)

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See detailOn multi-area control in electric power systems
Zima, Marek; Ernst, Damien ULg

in Proceedings of the 15th Power System Computation Conference (PSCC 2005) (2005)

In this paper we study the concept of electric power system control, when the responsibility for controlling the entire system is shared by agents controlling their assigned areas. Within this framework ... [more ▼]

In this paper we study the concept of electric power system control, when the responsibility for controlling the entire system is shared by agents controlling their assigned areas. Within this framework, we suggest to study the dynamics created by the interactions of agents. In particular, we discuss the relation that exists between the information available to the different agents and their optimisation objective, and the performance of the overall power system. Simulations results, carried out on a 39-node power system voltage control problem, are provided and analyzed. They highlight, among others, the sub-optimal performance level attained by the system when the different agents exchange information about their area dynamics without sharing a common control objective. [less ▲]

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See detailApplication of an advanced transient stability assessment and control method to a realistic power system
Cirio, D.; Lucarella, D.; Vimercati, G. et al

in Proceedings of the 15th Power System Computation Conference (PSCC 2005) (2005)

The paper presents a technical overview of a large research project on Dynamic Security Assessment (DSA) supported by EU. Transient Stability Assessment and Control, which was one of the main goals of the ... [more ▼]

The paper presents a technical overview of a large research project on Dynamic Security Assessment (DSA) supported by EU. Transient Stability Assessment and Control, which was one of the main goals of the project, is taken into consideration by presenting the fundamental theoretical methodology and possible applications. A specific prototype installation for a realistic power system is then reported by presenting and commenting some of the obtained results. [less ▲]

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See detailA comparison of Nash equilibria analysis and agent-based modelling for power markets
Krause, Thilo; Andersson, Goran; Ernst, Damien ULg et al

in Proceedings of the 15th Power System Computation Conference (PSCC 2005) (2005)

In this paper we compare Nash equilibria analysis and agent-based modelling for assessing the market dynamics of network-constrained pool markets. Power suppliers submit their bids to the market place in ... [more ▼]

In this paper we compare Nash equilibria analysis and agent-based modelling for assessing the market dynamics of network-constrained pool markets. Power suppliers submit their bids to the market place in order to maximize their payoffs, where we apply reinforcement learning as a behavioral agent model. The market clearing mechanism is based on the locational marginal pricing scheme. Simulations are carried out on a benchmark power system.We show how the evolution of the agent-based approach relates to the existence of a unique Nash equilibrium or multiple equilibria in the system. Additionally, the parameter sensitivity of the results is discussed. [less ▲]

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See detailNew developments in the application of automatic learning to power system control
Wehenkel, Louis ULg; Glavic, Mevludin; Ernst, Damien ULg

in Proceedings of the 15th Power System Computation Conference (PSCC 2005) (2005)

In this paper we present the basic principles of supervised learning and reinforcement learning as two complementary frameworks to design control laws or decision policies within the context of power ... [more ▼]

In this paper we present the basic principles of supervised learning and reinforcement learning as two complementary frameworks to design control laws or decision policies within the context of power system control. We also review recent developments in the realm of automatic learning methods and discuss their applicability to power system decision and control problems. Simulation results illustrating the potentials of the recently introduced fitted Q iteration learning algorithm in controlling a TCSC device aimed to damp electro-mechanical oscillations in a synthetic 4-machine system, are included in the paper. [less ▲]

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See detailApproximate value iteration in the reinforcement learning context. Application to electrical power system control
Ernst, Damien ULg; Glavic, Mevludin; Geurts, Pierre ULg et al

in International Journal of Emerging Electrical Power Systems (2005), 3(1),

In this paper we explain how to design intelligent agents able to process the information acquired from interaction with a system to learn a good control policy and show how the methodology can be applied ... [more ▼]

In this paper we explain how to design intelligent agents able to process the information acquired from interaction with a system to learn a good control policy and show how the methodology can be applied to control some devices aimed to damp electrical power oscillations. The control problem is formalized as a discrete-time optimal control problem and the information acquired from interaction with the system is a set of samples, where each sample is composed of four elements: a state, the action taken while being in this state, the instantaneous reward observed and the successor state of the system. To process this information we consider reinforcement learning algorithms that determine an approximation of the so-called Q-function by mimicking the behavior of the value iteration algorithm. Simulations are first carried on a benchmark power system modeled with two state variables. Then we present a more complex case study on a four-machine power system where the reinforcement learning algorithm controls a Thyristor Controlled Series Capacitor (TCSC) aimed to damp power system oscillations. [less ▲]

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See detailPreventive and emergency control of power systems
Wehenkel, Louis ULg; Ruiz-Vega, Daniel; Ernst, Damien ULg et al

in Real Time Stability in Power Systems - Techniques for Early Detection of the Risk of Blackout (2005)

A general approach to real-time transient stability control is described, yielding various complementary techniques: pure preventive, open loop emergency, and closed loop emergency controls. The ... [more ▼]

A general approach to real-time transient stability control is described, yielding various complementary techniques: pure preventive, open loop emergency, and closed loop emergency controls. The organization of the resulting control schemes is then revisited in order to make it able to cover static and voltage security, in addition to transient stability. Distinct approaches for preventive and emergency operating conditions are advocated. [less ▲]

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See detailCorpus mechanicum versus corpus mysticum : des conflits entre l'auteur d'une oeuvre et le propriétaire du support
Vanbrabant, Bernard ULg

in Revue de la Faculté de Droit de l'Université de Liège (2005), (4), 490-562

About the conflicts arising between the author and owner of a work of art: multiplicity thereof and how to resolve them

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