References of "Wehenkel, Louis"
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See detailRandom Subwindows and Randomized Trees for Image Retrieval, Classification, and Annotation
Marée, Raphaël ULg; Dumont, Marie; Geurts, Pierre ULg et al

Poster (2007, July 22)

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See detailApplication of the Galileo system for a better synchronization of electrical power systems
Mack, Philippe; Capitanescu, Florin ULg; Glavic, Mevludin et al

(2007, July)

In this paper we present objectives and strategies of the NAVELEC research project funded by the European Union Galileo Joint Undertaking (GJU/05/2423). The project objective is to assess how the European ... [more ▼]

In this paper we present objectives and strategies of the NAVELEC research project funded by the European Union Galileo Joint Undertaking (GJU/05/2423). The project objective is to assess how the European Global Navigation Satellite System related solutions can enhance the operation and control of the European power system over wide areas. Some basic functionalities of the GALILEO system are given first, then we summarize the questionnaire, set at the initial stage of the project, and provide the analysis of received responses from transmission system operators. Two generic strategies to upgrade existing electrical power transmission networks with functionalities, as well as major steps to upgrade underlying infrastructures, are discussed in this paper. [less ▲]

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See detailPREDetector: A new tool to identify regulatory elements in bacterial genomes
Hiard, Samuel ULg; Marée, Raphaël ULg; Colson, Séverine ULg et al

in Biochemical and Biophysical Research Communications (2007), 357(4), 861-864

In the post-genomic area, the prediction of transcription factor regulons by position weight matrix-based programmes is a powerful approach to decipher biological pathways and to modelize regulatory ... [more ▼]

In the post-genomic area, the prediction of transcription factor regulons by position weight matrix-based programmes is a powerful approach to decipher biological pathways and to modelize regulatory networks in bacteria. The main difficulty once a regulon prediction is available is to estimate its reliability prior to start expensive experimental validations and therefore trying to find a way how to identify true positive hits from an endless list of potential target genes of a regulatory protein. Here we introduce PREDetector (Prokaryotic Regulatory Elements Detector), a tool developed for predicting regulons of DNA-binding proteins in bacterial genomes that, beside the automatic prediction, scoring and positioning of potential binding sites and their respective target genes in annotated bacterial genomes, it also provides an easy way to estimate the thresholds where to find reliable possible new target genes. PREDetector can be downloaded freely at http://www.montefiore.ulg.ac.be/-hiard/PreDetector (c) 2007 Published by Elsevier Inc. [less ▲]

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See detailImproving the statement of the corrective security-constrained optimal power flow problem
Capitanescu, Florin ULg; Wehenkel, Louis ULg

in IEEE Transactions on Power Systems (2007), 22(2), 887-889

This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability ... [more ▼]

This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability constraints on the short-term equilibrium reached just after contingency. The rationale for doing so is discussed and supported by two examples. [less ▲]

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See detailInterior-point based algorithms for the solution of optimal power flow problems
Capitanescu, Florin ULg; Glavic, Mevludin; Ernst, Damien ULg et al

in Electric Power Systems Research (2007), 77(5-6), 508-517

Interior-point method (IPM) is a very appealing approach to the optimal power flow (OPF) problem mainly due to its speed of convergence and ease of handling inequality constraints. This paper analyzes the ... [more ▼]

Interior-point method (IPM) is a very appealing approach to the optimal power flow (OPF) problem mainly due to its speed of convergence and ease of handling inequality constraints. This paper analyzes the ability of three interior-point (IP) based algorithms, namely the pure primal-dual (PD), the predictor-corrector (PC) and the multiple centrality corrections (MCC), to solve various classical OPF problems: minimization of overall generation cost, minimization of active power losses, maximization of power system loadability and minimization of the amount of load curtailment. These OPF variants have been formulated using a rectangular model for the (complex) voltages. Numerical results on three test systems of 60, 118 and 300 buses are reported. (C) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailProjecting Generation Decisions Induced by a Stochastic Program on a Family of Supply Curve Functions
Defourny, Boris ULg; Wehenkel, Louis ULg

Scientific conference (2007, March)

We propose to post-process the results of a scenario based stochastic program by projecting its decisions on a parameterized space of policies. By doing so the risk of overfitting to the set of scenarios ... [more ▼]

We propose to post-process the results of a scenario based stochastic program by projecting its decisions on a parameterized space of policies. By doing so the risk of overfitting to the set of scenarios used in the stochastic program is reduced. A proper choice of the structure of the space of policies allows one to exploit them in the context of novel scenarios, be it for Monte-Carlo based value estimation or for use in real-life conditions. These ideas are presented in the context of planning the exploitation of electric energy resources or for evaluating the economic value of a portfolio of assets. [less ▲]

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See detailPREDetector : Prokaryotic Regulatory Element Detector
Hiard, Samuel ULg; Rigali, Sébastien ULg; Colson, Séverine ULg et al

Poster (2007, February 15)

Background: In the post-genomic area, in silico predictions of regulatory networks are considered as a powerful approach to decipher and understand biological pathways within prokaryotic cells. The ... [more ▼]

Background: In the post-genomic area, in silico predictions of regulatory networks are considered as a powerful approach to decipher and understand biological pathways within prokaryotic cells. The emergence of position weight matrices based programs has facilitated the access to this approach. However, a tool that automatically estimates the reliability of the predictions and would allow users to extend predictions in genomic regions generally regarded with no regulatory functions was still highly demanded. Result: Here, we introduce PREDetector, a tool developed for predicting regulons of DNA-binding proteins in prokaryotic genomes that (i) automatically predicts, scores and positions potential binding sites and their respective target genes, (ii) includes the downstream co-regulated genes, (iii) extends the predictions to coding sequences and terminator regions, (iv) saves private matrices and allows predictions in other genomes, and (v) provides an easy way to estimate the reliability of the predictions. Conclusion: We present, with PREDetector, an accurate prokaryotic regulon prediction tool that maximally answers biologists’ requests. PREDetector can be downloaded freely at http://www.montefiore.ulg.ac.be/~hiard/predetectorfr.html [less ▲]

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See detailBiomarker discovery for inflammatory bowel disease, using proteomic serum profiling
Meuwis, Marie-Alice ULg; Fillet, Marianne ULg; Geurts, Pierre ULg et al

in Biochemical Pharmacology (2007), 73(9), 1422-1433

Crohn's disease and ulcerative colitis known as inflammatory bowel diseases (IBD) are chronic immuno-inflammatory pathologies of the gastrointestinal tract. These diseases are multifactorial, polygenic ... [more ▼]

Crohn's disease and ulcerative colitis known as inflammatory bowel diseases (IBD) are chronic immuno-inflammatory pathologies of the gastrointestinal tract. These diseases are multifactorial, polygenic and of unknown etiology. Clinical presentation is non-specific and diagnosis is based on clinical, endoscopic, radiological and histological criteria. Novel markers are needed to improve early diagnosis and classification of these pathologies. We performed a study with 120 serum samples collected from patients classified in 4 groups (30 Crohn, 30 ulcerative colitis, 30 inflammatory controls and 30 healthy controls) according to accredited criteria. We compared protein sera profiles obtained with a Surface Enhanced Laser Desorption Ionization-Time of Flight-Mass Spectrometer (SELDI-TOF-MS). Data analysis with univariate process and a multivariate statistical method based on multiple decision trees algorithms allowed us to select some potential biomarkers. Four of them were identified by mass spectrometry and antibody based methods. Multivariate analysis generated models that could classify samples with good sensitivity and specificity (minimum 80%) discriminating groups of patients. This analysis was used as a tool to classify peaks according to differences in level on spectra through the four categories of patients. Four biomarkers showing important diagnostic value were purified, identified (PF4, MRP8, FIBA and Hpalpha2) and two of these: PF4 and Hpalpha2 were detected in sera by classical methods. SELDI-TOF-MS technology and use of the multiple decision trees method led to protein biomarker patterns analysis and allowed the selection of potential individual biomarkers. Their downstream identification may reveal to be helpful for IBD classification and etiology understanding. [less ▲]

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See detailRandom Subwindows and Multiple Output Decision Trees for Generic Image Annotation
Dumont, Marie; Marée, Raphaël ULg; Geurts, Pierre ULg et al

Poster (2007)

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See detailRandom subwindows and extremely randomized trees for image classification in cell biology
Marée, Raphaël ULg; Geurts, Pierre ULg; Wehenkel, Louis ULg

in BMC Cell Biology (2007), 8(Suppl. 1),

Background: With the improvements in biosensors and high-throughput image acquisition technologies, life science laboratories are able to perform an increasing number of experiments that involve the ... [more ▼]

Background: With the improvements in biosensors and high-throughput image acquisition technologies, life science laboratories are able to perform an increasing number of experiments that involve the generation of a large amount of images at different imaging modalities/scales. It stresses the need for computer vision methods that automate image classification tasks. Results: We illustrate the potential of our image classification method in cell biology by evaluating it on four datasets of images related to protein distributions or subcellular localizations, and red-blood cell shapes. Accuracy results are quite good without any specific pre-processing neither domain knowledge incorporation. The method is implemented in Java and available upon request for evaluation and research purpose. Conclusion: Our method is directly applicable to any image classification problems. We foresee the use of this automatic approach as a baseline method and first try on various biological image classification problems. [less ▲]

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See detailA collaborative framework for multi-area dynamic security assessment of large scale systems
Wehenkel, Louis ULg; Glavic, Mevludin; Ernst, Damien ULg

in Proceedings of the 2007 Power Tech (2007)

In this paper we propose a collaborative framework to carry out multi-area dynamic security assessment over an interconnection operated by a team of TSOs responsible of different areas. In this framework ... [more ▼]

In this paper we propose a collaborative framework to carry out multi-area dynamic security assessment over an interconnection operated by a team of TSOs responsible of different areas. In this framework each TSO does his part of the work and, thanks to information exchange and coordination rules, potential security problems can be detected by all the involved TSOs. We find that distributed multi-area security assessment is achievable and useful if, on the one hand, each TSO can provide an appropriate dynamic equivalent model of his area and if, on the other hand, he is able to publish stability bounds on his inflows under which the dynamic performance of his system would remain acceptable. We then discuss the notions of dynamic equivalent model and external stability domain characterization of an area and identify techniques for deriving such equivalents and stability bounds within the proposed framework. [less ▲]

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See detailThe cross-entropy method for power system combinatorial optimization problems
Ernst, Damien ULg; Glavic, Mevludin; Stan, Guy-Bart et al

in Proceedings of the 2007 Power Tech (2007)

We present an application of a cross-entropy based combinatorial optimization method for solving some unit commitment problems. We report simulation results and analyze, under several perspectives ... [more ▼]

We present an application of a cross-entropy based combinatorial optimization method for solving some unit commitment problems. We report simulation results and analyze, under several perspectives (accuracy, computing times, ability to solve efficiently large-scale problems), the performances of the approach. [less ▲]

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See detailModel predictive control and reinforcement learning as two complementary frameworks
Ernst, Damien ULg; Glavic, Mevludin; Capitanescu, Florin ULg et al

in International Journal of Tomography & Statistics (2007), 6

Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a ... [more ▼]

Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a discrete-time optimal control problem and compute a suboptimal control policy. We present in this paper in a unified framework these two families of methods. We run for MPC and RL algorithms simulations on a benchmark control problem taken from the power system literature and discuss the results obtained. [less ▲]

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See detailContent-based Image Retrieval by Indexing Random Subwindows with Randomized Trees
Marée, Raphaël ULg; Geurts, Pierre ULg; Wehenkel, Louis ULg

in Proc. 8th Asian Conference on Computer Vision (ACCV), LNCS (2007)

We propose a new method for content-based image retrieval which exploits the similarity measure and indexing structure of totally randomized tree ensembles induced from a set of subwindows randomly ... [more ▼]

We propose a new method for content-based image retrieval which exploits the similarity measure and indexing structure of totally randomized tree ensembles induced from a set of subwindows randomly extracted from a sample of images. We also present the possibility of updating the model as new images come in, and the capability of comparing new images using a model previously constructed from a different set of images. The approach is quantitatively evaluated on various types of images with state-of-the-art results despite its conceptual simplicity and computational efficiency [less ▲]

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See detailE-SIME- A method for transient stability closed-loop emergency control: achievements and prospects
Glavic, Mevludin; Ernst, Damien ULg; Ruiz-Vega, Daniel et al

in Proceedings of 2007 IREP Symposium - Bulk Power Systems Dynamics and Control - VII (2007)

A general response-based technique is presented for closed-loop transient stability emergency control. It relies on E-SIME, derived from the hybrid transient stability method, SIME. E-SIME uses real-time ... [more ▼]

A general response-based technique is presented for closed-loop transient stability emergency control. It relies on E-SIME, derived from the hybrid transient stability method, SIME. E-SIME uses real-time information supposed to be furnished by phasor measurement units to predict the stability status of the power system, and, in view of an imminent instability, to design and trigger appropriate countermeasures, while continuing monitoring in order to check their effectiveness or to apply additional ones. Performance of the method in terms of accuracy and rapidity is scrutinized and illustrated on several real-world power system examples. New technical solutions and algorithms for the accurate estimation and prediction of power system quantities most relevant to the method are discussed. The observations from a recent investigation and conclusions that could prove useful for improving further the method are summarized together with some realistic timing considerations. A natural coupling of the two SIME based emergency control techniques: open-loop emergency control and E-SIME, so as to combine their complementary features is also discussed. [less ▲]

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See detailAutomatic learning for the classification of primary frequency control behaviour
Cornélusse, Bertrand ULg; Wehenkel, Louis ULg; Wera, Claude

in Power Tech, 2007 IEEE Lausanne (2007)

In this paper we propose a methodology based on supervised automatic learning in order to classify the behaviour of generators in terms of their performance in providing primary frequency control ... [more ▼]

In this paper we propose a methodology based on supervised automatic learning in order to classify the behaviour of generators in terms of their performance in providing primary frequency control ancillary services. The problem is posed as a time-series classification problem, and handled by using state-of- the-art supervised learning methods such as ensembles of decision trees and support-vector machines combined with several preprocessing techniques. The method was designed in the context of the Belgian system and is validated on real-life data composed of more than 600 time-series recorded on this system. [less ▲]

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See detailGradient boosting for kernelized output spaces
Geurts, Pierre ULg; Wehenkel, Louis ULg; d'Alché-Buc, Florence

in Proceedings of the 24th International Conference on Machine Learning (2007)

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See detailNouvelles approches dans la prise en charge de l'infection a VIH.
Chandrika, K.; Dellot, Patricia ULg; Frippiat, Frédéric ULg et al

in Revue Médicale de Liège (2007), 62 Spec No

HIV infection remains a major problem of public health in Belgium as well as globally. The number of new diagnosies of HIV infection in Belgium remains between two and three daily. Given the dramatic ... [more ▼]

HIV infection remains a major problem of public health in Belgium as well as globally. The number of new diagnosies of HIV infection in Belgium remains between two and three daily. Given the dramatic effect of antiretroviral therapy on the mortality due to HIV infection, the number of patients is constantly increasing. The different problems related to HIV care are also changing. Aging of the patients and chronic exposure to antiretroviral medications have induced new complications. We will present in this brief article several new experimental and clinical approaches in which our centre has participated during the last two years. [less ▲]

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See detailPreDetector : Prokaryotic Regulatory Element Detector
Hiard, Samuel ULg; Rigali, Sébastien ULg; Colson, Séverine ULg et al

Poster (2006, May 17)

PreDetector is a stand-alone software, written in java. Its final aim is to predict regulatory sites for prokaryotic species. It comprises two functionalities. The first one is very similar to Target ... [more ▼]

PreDetector is a stand-alone software, written in java. Its final aim is to predict regulatory sites for prokaryotic species. It comprises two functionalities. The first one is very similar to Target Explorer1. From a set of sequences identified as potential target sites, PreDetector creates a consensus sequence and computes its scoring matrix. This sequence and matrix can be saved on a file and, then, be used to find along a selected genome the sequences that are close enough to the consensus sequence. To this end, a score is attributed to each locus in the genome according to the similarity measure defined by the matrix. The output of this functionality is filtered with a cut-off score and then directly used as input by the second one. The second functionality starts by fetching the gene positions of the selected species from the NCBI server. The loci having above cut-off score are then classified into four classes, allowing multiple classes for one element. This gives the biologists a better view of his discovered sequences. [less ▲]

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See detailExtremely randomized trees
Geurts, Pierre ULg; Ernst, Damien ULg; Wehenkel, Louis ULg

in Machine Learning (2006), 63(1), 3-42

This paper proposes anew tree-based ensemble method for supervised classification and regression problems. It essentially consists of randomizing strongly both attribute and cut-point choice while ... [more ▼]

This paper proposes anew tree-based ensemble method for supervised classification and regression problems. It essentially consists of randomizing strongly both attribute and cut-point choice while splitting a tree node. In the extreme case, it builds totally randomized trees whose structures are independent of the output values of the learning sample. The strength of the randomization can be tuned to problem specifics by the appropriate choice of a parameter. We evaluate the robustness of the default choice of this parameter, and we also provide insight on how to adjust it in particular situations. Besides accuracy, the main strength of the resulting algorithm is computational efficiency. A bias/variance analysis of the Extra-Trees algorithm is also provided as well as a geometrical and a kernel characterization of the models induced. [less ▲]

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