Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailOn the use of PMUs in power system state estimation
Gomez-Exposito, Antonio; Abur, Ali; Rousseaux, Patricia ULg et al

in Proceedings of the 17th PSCC (2011, August)

Synchronized phasor measurement units (PMUs) are becoming a reality in more and more power systems, mainly at the transmission level. This paper presents, in a tutorial manner, the benefits that existing ... [more ▼]

Synchronized phasor measurement units (PMUs) are becoming a reality in more and more power systems, mainly at the transmission level. This paper presents, in a tutorial manner, the benefits that existing and future State Estimators (SE) can achieve by incorporating these devices in the monitoring process. After a review of the relevant PMU technological aspects and the associated deployment issues (observability, optimal location, etc.), the alternative SE formulations in the presence of PMUs are revisited. Then, several application environments are separately addressed, regarding the enhancements potentially brought about by the use of PMUs. [less ▲]

Detailed reference viewed: 87 (8 ULg)
Full Text
Peer Reviewed
See detailOn the use of posture verbs by French-speaking learners of Dutch : A corpus-based study
Lemmens, Maarten; Perrez, Julien ULg

in Cognitive Linguistics (2010)

Detailed reference viewed: 29 (5 ULg)
Peer Reviewed
See detailOn the use of posture verbs by French-speaking learners of Dutch : a corpus-based study.
Lemmens, Maarten; Perrez, Julien ULg

Conference (2009)

Detailed reference viewed: 8 (3 ULg)
Full Text
See detailOn the Use of Principal Component Analysis for Parameter Identification and Damage Detection in Structures
Golinval, Jean-Claude ULg

Conference (2014, November 20)

Modal analysis is used extensively for understanding the dynamic behaviour of structures as well as for structural health monitoring or damage detection based on output-only measurements. In this ... [more ▼]

Modal analysis is used extensively for understanding the dynamic behaviour of structures as well as for structural health monitoring or damage detection based on output-only measurements. In this presentation, a different approach based on principal component analysis is considered. Principal component analysis (PCA), also called proper orthogonal decomposition (POD), is a multi-variate statistical method that aims at obtaining a compact representation of the data. In the present paper, PCA (POD) is used for three purposes, namely damage detection, structural health monitoring and identification of nonlinear parameters. The key idea of PCA is to reduce a large number of measured data to a much smaller number of uncorrelated variables while retaining as much as possible of the variation in the original data. To this purpose, an orthogonal transformation to the basis of the eigenvectors of the sample covariance matrix is performed, and the data are projected onto the subspace spanned by the eigenvectors corresponding to the largest eigenvalues. This transformation has the property to decorrelate the signal components and to maximize variance. The first problem to which PCA is applied here is the damage detection problem. When applied to vibration measurements, it can be shown that the basis of eigenvectors (called the proper orthogonal modes) span the same subspace as the mode-shape vectors of the monitored structure. Thus the damage detection problem may be solved using the concept of subspace angle between a reference subspace spanned by the eigenvectors of the initial (undamaged) structure and the subspace spanned by the eigenvectors of the current (possibly damaged) structure. The second problem concerns structural health monitoring of civil engineering structures when environmental effects (e.g. the influence of the variation of the ambient temperature) have to be removed from the structural changes. In this case, PCA may be applied on identified modal features (e.g. the natural frequencies) to separate the changes due to environmental variations from the changes due to damage sources. This procedure is illustrated on the example of a real bridge located in Luxembourg. The third problem is related to the estimation of nonlinear parameters using model updating techniques. In this case, the most interesting property of PCA is that it minimizes the average squared distance between the original signal and its reduced linear representation. When applied to nonlinear problems, PCA gives the optimal approximating linear manifold in the configuration space represented by the data. The linear nature of the method is appealing because the theory of linear operators is still available. However, it should be borne in mind that it also exhibits its major limitation when the data lie on a nonlinear manifold. [less ▲]

Detailed reference viewed: 53 (2 ULg)
Peer Reviewed
See detailOn the use of the Cowan's code for atomic structure calculations in singly ionized lanthanides
Quinet, Pascal ULg; Palmeri, P.; Biémont, Emile ULg

in Journal of Quantitative Spectroscopy & Radiative Transfer (1999), 62

Detailed reference viewed: 38 (2 ULg)
Full Text
Peer Reviewed
See detailOn the use of the sigma-coordinate system in regions of large bathymetric variations
Deleersnijder, Eric; Beckers, Jean-Marie ULg

in Journal of Marine Systems (1992), 3(4-5), 381-390

The sigma-transformation is a widely used coordinate change that maps the actual depth-varying sea onto a computational domain, the depth of which is constant. The advantages of this technique are ... [more ▼]

The sigma-transformation is a widely used coordinate change that maps the actual depth-varying sea onto a computational domain, the depth of which is constant. The advantages of this technique are numerous. It permits an efficient use of computer resources, a simple treatment of the surface and bottom boundary conditions, and an accurate representation of the bathymetry. However, if the range of the depth is too large, or when the depth varies too rapidly, as in the shelf break region, it may be shown that the sigma-transformation leads to severe numerical errors. In the application of GHER's three-dimensional model to the Western Mediterranean, the occurrence of those numerical errors is avoided by the introduction of a two-fold sigma-coordinate system in the deep sea. [less ▲]

Detailed reference viewed: 36 (2 ULg)
Full Text
Peer Reviewed
See detailOn the use of the transmission disequilibrium test to detect pseudo-autosomal variants affecting traits with sex-limited expression
Elansary, Mahmoud ULg; Stinckens, Anneleen; Ahariz, Naïma ULg et al

in Animal Genetics (2015)

We herein describe the realization of a genome-wide association study for scrotal hernia and cryptorchidism in Norwegian and Belgian commercial pig populations. We have used the transmission ... [more ▼]

We herein describe the realization of a genome-wide association study for scrotal hernia and cryptorchidism in Norwegian and Belgian commercial pig populations. We have used the transmission disequilibrium test to avoid spurious associations due to population stratification. By doing so, we obtained genome-wide significant signals for both diseases with SNPs located in the pseudo-autosomal region in the vicinity of the pseudo-autosomal boundary. By further analyzing these signals, we demonstrate that the observed transmission disequilibria are artifactual. We determine that transmission bias at pseudo-autosomal markers will occur (i) when analyzing traits with sex-limited expression and (ii) when the allelic frequencies at the marker locus differ between X and Y chromosomes. We show that the bias is due to the fact that (i) sires will preferentially transmit the allele enriched on the Y (respectively X) chromosome to affected sons (respectively daughters) and (ii) dams will appear to preferentially transmit the allele enriched on the Y (respectively X) to affected sons (respectively daughters), as offspring inheriting the other allele are more likely to be non-informative. We define the conditions to mitigate these issues, namely by (i) extracting information from maternal meiosis only and (ii) ignoring trios for which sire and dam have the same heterozygous genotype. We show that by applying these rules to scrotal hernia and cryptorchidism, the pseudo-autosomal signals disappear, confirming their spurious nature. [less ▲]

Detailed reference viewed: 17 (1 ULg)
Peer Reviewed
See detailOn the use of variable complementarity for feature selection in cancer classification
Meyer, Patrick ULg; Bontempi, Gianluca

in Applications of Evolutionary Computing (2006)

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailOn the Use of Weak Automata for Deciding Linear Arithmetic with Integer and Real Variables
Boigelot, Bernard ULg; Jodogne, Sébastien ULg; Wolper, Pierre ULg

in Lecture Notes in Computer Science (2001), 2083

This paper considers finite-automata based algorithms for handling linear arithmetic with both real and integer variables. Previous work has shown that this theory can be dealt with by using finite ... [more ▼]

This paper considers finite-automata based algorithms for handling linear arithmetic with both real and integer variables. Previous work has shown that this theory can be dealt with by using finite automata on in finite words, but this involves some difficult and delicate to implement algorithms. The contribution of this paper is to show, using topological arguments, that only a restricted class of automata on in finite words are necessary for handling real and integer linear arithmetic. This allows the use of substantially simpler algorithms and opens the path to the implementation of a usable system for handling this combined theory. [less ▲]

Detailed reference viewed: 32 (6 ULg)
Peer Reviewed
See detailOn the Uses and Abuses of Degenerate Art
Delville, Michel ULg

Conference (2002, May 11)

Detailed reference viewed: 4 (1 ULg)
Full Text
Peer Reviewed
See detailOn the value of conditioning data to reduce conceptual model uncertainty in groundwater modeling
Rojas, Rodrigo; Feyen, Luc; Batelaan, Okke et al

in Water Resources Research (2010), 46(8), 08520

Recent applications of multi-model methods have demonstrated their potential in quantifying conceptual model uncertainty in groundwater modeling applications. To date, however, little is known about the ... [more ▼]

Recent applications of multi-model methods have demonstrated their potential in quantifying conceptual model uncertainty in groundwater modeling applications. To date, however, little is known about the value of conditioning to constrain the ensemble of conceptualizations, to differentiate among retained alternative conceptualizations, and to reduce conceptual model uncertainty. We address these questions by conditioning multi-model simulations on measurements of hydraulic conductivity and observations of system-state variables and evaluating the e ffects on (i) the posterior multi-model statistics and (ii) the contribution of conceptual model uncertainty to the predictive uncertainty. Multi-model aggregation and conditioning is performed by combining the generalized likelihood uncertainty estimation (GLUE) method and Bayesian model averaging (BMA). As an illustrative example we employ a 3-dimensional hypothetical system under steady-state conditions, for which uncertainty about the conceptualization is expressed by an ensemble (M) of 7 models with varying complexity. Results show that conditioning on heads allowed for the exclusion of the two simplest models, but that their information content is limited to further diff erentiate among the retained conceptualizations. Conditioning on increasing numbers of conductivity measurements allowed for a further reffinement of the ensemble M and resulted in an increased precision and accuracy of the multi-model predictions. For some groundwater flow components not included as conditioning data, however, the gain in accuracy and precision was partially o ffset by strongly deviating predictions of a single conceptualization. Identifying the conceptualization producing the most deviating predictions may guide data collection campaigns aimed at acquiring data to further eliminate such conceptualizations. Including groundwater flow and river discharge observations further allowed for a better diff erentiation among alternative conceptualizations and drastic reductions of the predictive variances. Results strongly advocate the use of observations less commonly available than groundwater heads to reduce conceptual model uncertainty in groundwater modeling. [less ▲]

Detailed reference viewed: 138 (14 ULg)
Peer Reviewed
See detailOn the value of incorporating dominance effects in genetic evaluation of dairy cattle.
Druet, Tom ULg; Solkner, J.; Misztal, I. et al

in Proceedings of the 7th World Congress on Genetics Applied to LivestockProduction, Montpellier, France, August, 2002. Session 1 (2002)

Detailed reference viewed: 16 (2 ULg)
Full Text
Peer Reviewed
See detailOn the Vedic Yajamâna-
Swennen, Philippe ULg

in Acts of the 6th Vedic Workshop (in press)

Detailed reference viewed: 20 (0 ULg)
Peer Reviewed
See detailOn the Vedic Yajamâna-
Swennen, Philippe ULg

Conference (2014, January 07)

When he is consecrated, the Vedic Yajamâna symbolically becomes an embryo because he originally had the become a new Mârtânda in order to conquer the same divine status obtained by Vivasvant thanks to the ... [more ▼]

When he is consecrated, the Vedic Yajamâna symbolically becomes an embryo because he originally had the become a new Mârtânda in order to conquer the same divine status obtained by Vivasvant thanks to the realization of the first sacrifice. [less ▲]

Detailed reference viewed: 17 (3 ULg)
Full Text
See detailOn the Verification of Programs on Relaxed Memory Models
Linden, Alexander ULg

Doctoral thesis (2013)

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and ... [more ▼]

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and where model-checking consists in verifying a given property when exploring the state space of a program. However, modern multi-core processor architectures implement relaxed memory models, such as "Total Store Order" (TSO), "Partial Store Order" (PSO), or an extension with locks such as "x86-TSO", which allow stores to be delayed in various ways and thus introduce many more possible executions, and hence errors, than those present in SC. Of course, one can force a program executed in the context of a relaxed memory system to behave exactly as in SC by adding synchronization operations after every memory access. But this totally defeats the performance advantage that is precisely the motivation for implementing relaxed memory models instead of SC. Thus, when moving a program to an architecture implementing a relaxed memory model (which includes most current multi-core processors), it is essential to have tools to help the programmer check if correctness (e.g. a safety property) is preserved and, if not, to minimally introduce the necessary synchronization operations. The proposed verification approach uses an operational store-buffer-based semantics of the chosen relaxed memory models and proceeds by using finite automata for symbolically representing the possible contents of the buffers. Store, load, commit and other synchronization operations then correspond to operations on these finite automata. The advantage of this approach is that it operates on (potentially infinite) sets of buffer contents, rather than on individual buffer configurations, and that it is compatible with partial-order reduction techniques. This provides a way to tame the explosion of the number of possible buffer configurations, while preserving the full generality of the analysis. It is thus possible to even check designs that may contain cycles. This verification approach then serves as a basis to a memory fence insertion algorithm that finds how to preserve the correctness of a program when it is moved from SC to TSO or PSO. Its starting point is a program that is correct for the sequential consistency memory model (with respect to a given safety property), but that might be incorrect under TSO or PSO. This program is then analyzed for the chosen relaxed memory model and when errors are found (a violated safety property), memory fences are inserted in order to avoid these errors. The approach proceeds iteratively and heuristically, inserting memory fences until correctness is obtained, which is guaranteed to happen. [less ▲]

Detailed reference viewed: 104 (19 ULg)
See detailOn the way of understanding the adaptation to extreme pH of family 11 xylanases: Structural comparison and mutational analysis
De Lemos Esteves, Frédéric ULg; Ruelle, Virginie; Gouders, Thierry et al

Poster (2004, December)

Detailed reference viewed: 11 (2 ULg)