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See detailIterative ecological radiation and convergence in damselfishes (Pomacentridae)
Frederich, Bruno ULg

Scientific conference (2012, December 12)

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See detailAn iterative finite element perturbation method for computing electrostatic field distortions
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in IEEE Transactions on Magnetics (2008), 44(6), 746-749

A finite element perturbation method is developed for computing electrostatic field distortions and the ensuing charges and forces on moving conductive regions subjected to fixed potentials. It is based ... [more ▼]

A finite element perturbation method is developed for computing electrostatic field distortions and the ensuing charges and forces on moving conductive regions subjected to fixed potentials. It is based on the subsequent solution of an unperturbed problem in a complete domain, where conductive regions have been extracted, and of perturbation problems in subdomains restricted to the surroundings of the added conductive regions. The solution of the unperturbed problem serves as source (with a very reduced support) for the perturbation subproblems. For every new position of the conductors, the solution of the unperturbed problem does not vary and is thus reused; only the perturbation subproblems have to be solved. Further, this approach allows for the use of independent and well-adapted meshes. An iterative procedure is required if the conductive regions are close to the sources. [less ▲]

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See detailAn Iterative Finite Element Perturbation Method for Computing Electrostatic Field Distortions
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in Proceedings of 16th Conference on the Computation of Electromagnetic Fields (COMPUMAG2007) (2007, June)

A finite element (FE) perturbation method for computing electrostatic field distortions due to moving conductors is presented. First, an unperturbed problem (in the absence of conductors) is solved with ... [more ▼]

A finite element (FE) perturbation method for computing electrostatic field distortions due to moving conductors is presented. First, an unperturbed problem (in the absence of conductors) is solved with the conventional FE method in the complete domain. Then, a perturbed problem is computed in a reduced region using the solution of the unperturbed problem as a source field. When the source is close to the perturbing regions, an iterative computation may be required. The developed procedure allows for solving sub-problems in reduced domains with independent problem-adapted meshes. [less ▲]

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See detailIterative finite element solution of multiple-scattering problems at high frequencies
Geuzaine, Christophe ULg; Dular, Patrick ULg; Gaignaire, R. et al

in Proceedings of the 8th International Symposium on Electric and Magnetic Fields (EMF'2009) (2009)

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See detailIterative Fragmentation Improves the Detection of ChIP-seq Peaks for Inactive Histone Marks.
Laczik, Miklos ULg; Hendrickx, Jan; Veillard, Anne-Clemence et al

in Bioinformatics and biology insights (2016), 10

As chromatin immunoprecipitation (ChIP) sequencing is becoming the dominant technique for studying chromatin modifications, new protocols surface to improve the method. Bioinformatics is also essential to ... [more ▼]

As chromatin immunoprecipitation (ChIP) sequencing is becoming the dominant technique for studying chromatin modifications, new protocols surface to improve the method. Bioinformatics is also essential to analyze and understand the results, and precise analysis helps us to identify the effects of protocol optimizations. We applied iterative sonication - sending the fragmented DNA after ChIP through additional round(s) of shearing - to a number of samples, testing the effects on different histone marks, aiming to uncover potential benefits of inactive histone marks specifically. We developed an analysis pipeline that utilizes our unique, enrichment-type specific approach to peak calling. With the help of this pipeline, we managed to accurately describe the advantages and disadvantages of the iterative refragmentation technique, and we successfully identified possible fields for its applications, where it enhances the results greatly. In addition to the resonication protocol description, we provide guidelines for peak calling optimization and a freely implementable pipeline for data analysis. [less ▲]

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See detailAn iterative maximum a posteriori estimation of proficiency level to detect multiple local likelihood maxima
Magis, David ULg; Raîche, Gilles

in Applied Psychological Measurement (2010), 34

In this article the authors focus on the issue of the nonuniqueness of the maximum likelihood (ML) estimator of proficiency level in item response theory (with special attention to logistic models). The ... [more ▼]

In this article the authors focus on the issue of the nonuniqueness of the maximum likelihood (ML) estimator of proficiency level in item response theory (with special attention to logistic models). The usual maximum a posteriori (MAP) method offers a good alternative within that framework; however, this article highlights some drawbacks of its use. The authors then propose an iteratively based MAP estimator (IMAP), which can be useful in detecting multiple local likelihood maxima. The efficiency of the IMAP estimator is studied and is compared to the ML and MAP methods by means of a simulation study. [less ▲]

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See detailIterative multi-task sequence labeling for predicting structural properties of proteins
Maes, Francis ULg; Becker, Julien ULg; Wehenkel, Louis ULg

in ESANN 2011 (2011)

Developing computational tools for predicting protein structural information given their amino acid sequence is of primary importance in protein science. Problems, such as the prediction of secondary ... [more ▼]

Developing computational tools for predicting protein structural information given their amino acid sequence is of primary importance in protein science. Problems, such as the prediction of secondary structures, of solvent accessibility, or of disordered regions, can be expressed as sequence labeling problems and could be solved independently by existing machine learning based sequence labeling approaches. But, since these problems are closely related, we propose to rather approach them jointly in a multi-task approach. To this end, we introduce a new generic framework for iterative multi-task sequence labeling. We apply this - conceptually simple but quite effective - strategy to jointly solve a set of five protein annotation tasks. Our empirical results with two protein datasets show that the proposed strategy significantly outperforms the single-task approaches. [less ▲]

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See detailIterative Proportional Fitting to expand a synthetic sample into a synthetic population
Cools, Mario ULg

Scientific conference (2016)

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See detailIterative pruning method of unsupervised clustering for categorical data
Chaichoompu, Kridsadakorn ULg; Tongsima, Sissades; Shaw, Philip James et al

Poster (2016, April 03)

Single Nucleotide Polymorphisms (SNPs) are commonly used to identify population structures. Iterative pruning Principal Component Analysis (ipPCA) utilizes SNP profiles to assign individuals to ... [more ▼]

Single Nucleotide Polymorphisms (SNPs) are commonly used to identify population structures. Iterative pruning Principal Component Analysis (ipPCA) utilizes SNP profiles to assign individuals to subpopulations without making assumptions about ancestry. The strategy can be extrapolated to patient samples to identify molecular classes of patients. It is challenging to investigate the utility of substructure detection using profiles based on pre-defined genomic regions-of-interest rather than profiles based on SNPs. Using principles outlined in Fouladi, 2015, we can construct gene-based categorical variables representing different summary gene profiles in a region. These gene-based new constructs no longer have an equal number of unordered category levels. Here, we present C-PCA, an extension of ipPCA to target perform iterative pruning for categorical variables using optimal scaling. It allows performing non-linear principal component analyses to handle possibly non-linearly related variables with different measurement levels. To show the power of C-PCA compared to ipPCA, we simulated 500 individuals and assigned them to two populations of equal size. We considered genetic population distances using Fixation Index from 0.001 to 0.006. For each dataset, we simulated 10,000 independent random SNPs for 100 replicates using the Balding–Nichols model. These were used numerically in ipPCA and as categorical in C-PCA analysis. In conclusion, like ipPCA, we expect C-PCA to perform well in the presence of fine substructures. This paves the way to apply C-PCA to DNA-seq data and input categorical variable derived from genomic regions-of-interest to which common and rare variants are mapped. We foresee additional advantages of C-PCA in this context since region-based categorical variables are likely to be non-linearly associated at the background of underlying gene-gene interaction networks. C-PCA is implemented in R. [less ▲]

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See detailIterative pruning PCA improves resolution of highly structured populations.
Intarapanich, Apichart; Shaw, Philip J.; Assawamakin, Anunchai et al

in BMC bioinformatics (2009), 10

BACKGROUND: Non-random patterns of genetic variation exist among individuals in a population owing to a variety of evolutionary factors. Therefore, populations are structured into genetically distinct ... [more ▼]

BACKGROUND: Non-random patterns of genetic variation exist among individuals in a population owing to a variety of evolutionary factors. Therefore, populations are structured into genetically distinct subpopulations. As genotypic datasets become ever larger, it is increasingly difficult to correctly estimate the number of subpopulations and assign individuals to them. The computationally efficient non-parametric, chiefly Principal Components Analysis (PCA)-based methods are thus becoming increasingly relied upon for population structure analysis. Current PCA-based methods can accurately detect structure; however, the accuracy in resolving subpopulations and assigning individuals to them is wanting. When subpopulations are closely related to one another, they overlap in PCA space and appear as a conglomerate. This problem is exacerbated when some subpopulations in the dataset are genetically far removed from others. We propose a novel PCA-based framework which addresses this shortcoming. RESULTS: A novel population structure analysis algorithm called iterative pruning PCA (ipPCA) was developed which assigns individuals to subpopulations and infers the total number of subpopulations present. Genotypic data from simulated and real population datasets with different degrees of structure were analyzed. For datasets with simple structures, the subpopulation assignments of individuals made by ipPCA were largely consistent with the STRUCTURE, BAPS and AWclust algorithms. On the other hand, highly structured populations containing many closely related subpopulations could be accurately resolved only by ipPCA, and not by other methods. CONCLUSION: The algorithm is computationally efficient and not constrained by the dataset complexity. This systematic subpopulation assignment approach removes the need for prior population labels, which could be advantageous when cryptic stratification is encountered in datasets containing individuals otherwise assumed to belong to a homogenous population. [less ▲]

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See detailIterative solution of high-frequency multiple-scattering problems using finite elements
Geuzaine, Christophe ULg; Vion, Alexandre ULg; V Sabariego, Ruth ULg

in Proceedings of the IVth European Conference on Computational Mechanics (ECCM 2010) (2010)

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See detailIterative solvers and stabilisation for mixed electrostatic and magnetostatic formulations
Deliège, Geoffrey ULg; Rosseel, Eveline; Vandewalle, Stefan

in Journal of Computational & Applied Mathematics (2008), 215(2), 348-356

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See detailIterative Solvers for Large Pressure Dependent Problems
Boman, Romain ULg; Colantonio, Laurent; Ponthot, Jean-Philippe ULg

in Huétink, J.; Baaijens, F. P. T. (Eds.) Proceedings of the Sixth International Conference on Numerical Methods in Industrial Forming Processes (1998, June)

In this paper, we present a stress update scheme for non-deviatoric elastoviscoplastic models, which can be considered as an extension of the radial return method for classical plasticity. We use the ... [more ▼]

In this paper, we present a stress update scheme for non-deviatoric elastoviscoplastic models, which can be considered as an extension of the radial return method for classical plasticity. We use the unconditionally stable backward Euler scheme to obtain the viscoplastic solution at each increment. To solve the large sparse non symmetric iteration matrix, we use the GMRES method. This fast iterative solver, in conjunction with an appropriate preconditioner, can save a lot a memory and CPU time when 3D problem are considered. A comparison between direct and iterative solvers will be discussed on two applications of cold compaction of powders. [less ▲]

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See detailIteratively extending time horizon reinforcement learning
Ernst, Damien ULg; Geurts, Pierre ULg; Wehenkel, Louis ULg

in Machine Learning: ECML 2003, 14th European Conference on Machine Learning (2003)

Reinforcement learning aims to determine an (infinite time horizon) optimal control policy from interaction with a system. It can be solved by approximating the so-called Q-function from a sample of four ... [more ▼]

Reinforcement learning aims to determine an (infinite time horizon) optimal control policy from interaction with a system. It can be solved by approximating the so-called Q-function from a sample of four-tuples (x(t), u(t), r(t), x(t+1)) where x(t) denotes the system state at time t, ut the control action taken, rt the instantaneous reward obtained and x(t+1) the successor state of the system, and by determining the optimal control from the Q-function. Classical reinforcement learning algorithms use an ad hoc version of stochastic approximation which iterates over the Q-function approximations on a four-tuple by four-tuple basis. In this paper, we reformulate this problem as a sequence of batch mode supervised learning problems which in the limit converges to (an approximation of) the Q-function. Each step of this algorithm uses the full sample of four-tuples gathered from interaction with the system and extends by one step the horizon of the optimality criterion. An advantage of this approach is to allow the use of standard batch mode supervised learning algorithms, instead of the incremental versions used up to now. In addition to a theoretical justification the paper provides empirical tests in the context of the "Car on the Hill" control problem based on the use of ensembles of regression trees. The resulting algorithm is in principle able to handle efficiently large scale reinforcement learning problems. [less ▲]

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See detailIti dans le Jaiminîya-brâhmana et dans le Shâbara-bhâshya
Verpoorten, Jean-Marie ULg

in Brereton, Joel; Jamison, Stephanie (Eds.) Sense and syntax in Vedic (1991)

Enquête sur la fonction et la position de iti dans Jaiminīya-br. 366 –376 dans l’Auswahl de W.Caland et de Śābara-bh. ad Mīmāṃsā 3 3 sūtra 14. Des deux côtés, iti sert principalement à clore un segment ... [more ▼]

Enquête sur la fonction et la position de iti dans Jaiminīya-br. 366 –376 dans l’Auswahl de W.Caland et de Śābara-bh. ad Mīmāṃsā 3 3 sūtra 14. Des deux côtés, iti sert principalement à clore un segment déclaratif qui peut précéder ou suivre des verbes comme BRŪ, AH, VAC et VAD. Les formes āha et āhuḥ , qui recherchent l’enclise de phrase, s’intercalent aussi au milieu du segment en question. Dans le Jaiminīya.br., d’autres verbes, soit synonymes de « dire », soit verbes d’action, sont suivis, à quelques exceptions près, de la phrase en iti. On rencontre aussi iti à la fin d’une énumération. Inversement, alorsqu’on l’attend, il est oublié, mais ceci est plus rare en prose qu’en poésie. Chez Śabara VAD et AH se font rares tandis que VAC est usité de préférence au passif (uktam, ucyate), prècède plutôt le segment en iti qui énonce la ou les thèses en discussion. Dans le débat, iti ferme questions, réponses et citations. Il n’est pas toujours accompagné d’un verbe de soutien, notamment quand la phrase est une objection introduite par nanu (« Pardon mais ») ou une conclusion introduite par tasmāt (« voilà pourquoi ») . La phrase à iti peut être causale ou expliciter un mot, en le précédant, le suivant ou l’entourant. Il arrive aussi que cette phrase s’appuie sur un pronom résomptif qui la reprend après iti ou sur le groupe evamādi. [less ▲]

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See detailItinéraire d’une fable : le Loup et le Chien
Pietquin, Paul ULg; Dachy, Françoise; Debrux, Thomas et al

in Etudes Classiques (Namur, Belgium) (1994), 62

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See detailL'itinéraire de Candide Wizo : un élément de datation des oeuvres anti-adoptianistes d'Alcuin? Note sur les lettres 41 et 204 de la correspondance d'Alcuin
Close, Florence ULg

in Revue d'Histoire Ecclésiastique (2008), 103(1), 5-26

In E. Dummler’s edition of Alcuin’s correspondence, L. 41 bears the date 794-795. This chronological indication has never been refuted. However, the topics dealt with in this document obviously refer to ... [more ▼]

In E. Dummler’s edition of Alcuin’s correspondence, L. 41 bears the date 794-795. This chronological indication has never been refuted. However, the topics dealt with in this document obviously refer to the second adoptianist problem (797-799), during which Candidus Wido acted as an intermediary between the Frankish court and the abbey of St. Martin de Tours. A critical reading, carefully taking into account the itinerary of Alcuin’s disciple, leads one to assign the writing of L.41 to the autumn of 798. It is, moreover, advisable to amend the critical commentary consecrated to L. 204 in the Clavis des auteurs latins du moyen age. Clavis Wizo did not present the Contra Felicem libri V11 to the court. [less ▲]

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See detailUn itinéraire du Sart Tilman
Frankignoulle, Pierre ULg; Merch, Marie-Christine ULg

E-print/Working paper (2010)

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See detailItinéraire géologique et paleontologique dans la carrière d'Ampsin (Amay, Belgique)
Barchy, Laurent; Marion, Jean-Marc ULg; Poty, Edouard ULg

Diverse speeche and writing (2008)

Close to the museum "Master of the Fire" at Ampsin (Amay, Belgium), an abandoned quarry is used to present both the local and regional geologic history, and the fauna and flora related to the site. For ... [more ▼]

Close to the museum "Master of the Fire" at Ampsin (Amay, Belgium), an abandoned quarry is used to present both the local and regional geologic history, and the fauna and flora related to the site. For all. [less ▲]

Detailed reference viewed: 284 (44 ULg)