Publications ORBi OA     Results 41-60 of 42938.   1 2 3 4 5 6 7 8   Contribution of distribution network control to voltage stability: A case studyAristidou, Petros ; Valverde, Gustavo; Van Cutsem, Thierry in IEEE Transactions on Smart Grid (in press)A case study dealing with long-term voltage instability in systems hosting active distribution networks is reported in this paper. It anticipates future situations with high penetration of dispersed ... [more ▼]A case study dealing with long-term voltage instability in systems hosting active distribution networks is reported in this paper. It anticipates future situations with high penetration of dispersed generation, where the latter are used to keep distribution voltages within desired limits, in complement to load tap changers. The interactions between transmission and active distribution networks are investigated on a 3108-bus test system. It involves transmission grid, large generators, and forty distribution networks, each with dispersed generation steered by a controller inspired of model predictive control. The reported simulations show the impact of distribution network voltage restoration as well as the benefit of load voltage reduction actuated by the dispersed generators. [less ▲]Detailed reference viewed: 118 (22 ULg) Compte rendu de Hagiographies. Histoire internationale de la littérature hagiographique latine et vernaculaire en Occident des origines à 1550, sous la direction de Monique Goullet, vol. 6. Turnhout, Brepols, 2014 (Corpus Christianorum. Hagiographies, 6).George, Philippe in Revue d'Histoire Ecclésiastique (in press)Detailed reference viewed: 36 (4 ULg) Drying induced shrinkage of Boom Clay: an experimental investigationPrime, Noémie; Levasseur, Séverine; Miny, Laurent et alin Canadian Geotechnical Journal (in press)Drying induced shrinkage of geomaterials may have a strong effect on geostructure stability and deformation. Settlement of foundations, fracture opening on slopes, roads, tunnel walls may be due to drying ... [more ▼]Drying induced shrinkage of geomaterials may have a strong effect on geostructure stability and deformation. Settlement of foundations, fracture opening on slopes, roads, tunnel walls may be due to drying shrinkage. However, there is still a lack of knowledge concerning shrinkage evolution in time and shrinkage propagation within the material. In this study, the shrinkage of a specific clayey rock, Boom Clay, under drying conditions is experimentally investigated. This rock is a deep geological formation which is under study for high-level and long-life radioactive waste storage in Belgium. Two experimental campaigns are here presented. The first one, based on vapour equilibrium drying technique and completed by sample size manual measurement, aims to characterize the material shrinkage in balanced states. The second one, based on convective drying technique completed by shape monitoring using X-ray tomography, aims to analyse how shrinkage develops before reaching a steady state. Both approaches put in evidence the shrinkage anisotropy of this structurally bedded rock, with a ratio around 2 between the direction of maximum strains and the direction of minimum strains. However, the two drying techniques also provide complementary results, as the relation between the amount of shrinkage and the retention curve (for the uniform drying imposed with saline solutions) and the kinetics of shrinkage propagation inside the material (for the non-uniform drying imposed with air convection). [less ▲]Detailed reference viewed: 33 (3 ULg) Étude des contraintes mécaniques locomotrices chez le chevalNoble, Prisca ; Collin, Bernard ; Denoix, Jean-Marie et alin Annales de Médecine Vétérinaire (in press)In locomotor biomechanics, three high groups of contraints are commonly encountared : pressure, traction and torsion. In supra-maximal conditions, all of these contraints would be responsible of some ... [more ▼]In locomotor biomechanics, three high groups of contraints are commonly encountared : pressure, traction and torsion. In supra-maximal conditions, all of these contraints would be responsible of some equine diseased locomotor systems. In order to understand better the contraints in the equine locomotor dynamics, some investigations have been carried out. Moreover, some measurement methods, based on the mechanics of Newton, have been performed. This review shows the different measurement techniques and introduces the mechanical basis that are compulsory for the understanding of the equine locomotor apparatus functioning. [less ▲]Detailed reference viewed: 186 (38 ULg) Reforming the Postal Universal ServiceGautier, Axel ; Poudou, Jean-Christophein Review of Network Economics (in press)The postal sector has undergone dramatic changes over the recent years under the double effect of ongoing liberalization and increased competition with alternative communication channels (e-substitution ... [more ▼]The postal sector has undergone dramatic changes over the recent years under the double effect of ongoing liberalization and increased competition with alternative communication channels (e-substitution). As a result, the mail volume handled by the historical operator has declined sharply while the latter's ability to match the same standard of universal service may be under threat. Thus, a reform of the postal universal service is on the agenda. This paper examines possible reforming options ranging from keeping universal service within the postal sector to redefining universal service as spanning postal and electronic technologies. [less ▲]Detailed reference viewed: 93 (6 ULg) A Quantitative Doignon-Bell-Scarf theoremAliev, Iskander; Bassett, Robert; De Loera, Jesus et alin Combinatorica (in press)The famous Doignon-Bell-Scarf theorem is a Helly-type result about the existence of integer solutions to systems of linear inequalities. The purpose of this paper is to present the following quantitative ... [more ▼]The famous Doignon-Bell-Scarf theorem is a Helly-type result about the existence of integer solutions to systems of linear inequalities. The purpose of this paper is to present the following quantitative generalization: Given an integer k, we prove that there exists a constant c(n,k), depending only on the dimension n and on the number k, such that if a bounded polyhedron {x in R^n : Ax <= b} contains exactly k integer points, then there exists a subset of the rows, of cardinality no more than c(n,k), defining a polyhedron that contains exactly the same k integer points. In this case c(n,0)=2^n as in the original case of Doignon-Bell-Scarf for infeasible systems of inequalities. We work on both upper and lower bounds for the constant c(n,k) and discuss some consequences, including a Clarkson-style algorithm to find the l-th best solution of an integer program with respect to the ordering induced by the objective function. [less ▲]Detailed reference viewed: 27 (6 ULg) Parametric Polyhedra with at least k Lattice Points: Their Semigroup Structure and the k-Frobenius ProblemAliev, Iskander; De Loera, Jesus; Louveaux, Quentin in Beveridge, Andrew; Griggs, Jerold; Hogben, Leslie (Eds.) et al Recent trends in Combinatorics (in press)The well-studied semigroup Sg(A) = {b : b = Ax; x in Z^n; x >= 0} can be stratified by the sizes of the polyhedral fibers IPA(b) = {x : Ax = b; x >= 0; x in Z^n}. The key theme of this paper is a ... [more ▼]The well-studied semigroup Sg(A) = {b : b = Ax; x in Z^n; x >= 0} can be stratified by the sizes of the polyhedral fibers IPA(b) = {x : Ax = b; x >= 0; x in Z^n}. The key theme of this paper is a structure theory that characterizes precisely the set Sg_k(A) of all vectors b in Sg(A) such that their fiber IPA(b) has at least k-solutions. We demonstrate that this set is finitely generated, a union of translated copies of a semigroup which can be computed explicitly via Hilbert bases computations. Related results can be derived for those right-hand-side vectors b for which IPA(b) has exactly k solutions or fewer than k solutions. We also show that, when n, k are fixed natural numbers, one can compute in polynomial time an encoding of Sg_k(A) as a generating function, using a short sum of rational functions. As a consequence, one can identify all right-hand-side vectors that have at least k solutions. Using this tool we prove that for fixed n; k the k-Frobenius number can be computed in polynomial time, generalizing a well-known result of R. Kannan. [less ▲]Detailed reference viewed: 22 (3 ULg) Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraphRuane, Garreth J.; Huby, Elsa ; Absil, Olivier et alin Astronomy and Astrophysics (in press)The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial ... [more ▼]The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression. We introduce a phase-only Lyot-plane optic to the vortex coronagraph that offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described and compared. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm. Numerically, we achieve a contrast on the order of $10^{-6}$ for a companion with angular displacement as small as $4~\lambda/D$ with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or optimized pupil plane phase element alone. [less ▲]Detailed reference viewed: 16 (0 ULg) Post-coronagraphic tip-tilt sensing for vortex phase masks: the QACITS techniqueHuby, Elsa ; Baudoz, Pierre; Mawet, Dimitri et alin Astronomy and Astrophysics (in press)Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization ... [more ▼]Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization. However, the drawback of this attractive feature is a high sensitivity to pointing errors, which degrades the performance of the coronagraph. We propose a tip-tilt retrieval technique based on the analysis of the final coronagraphic image, hereafter called Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing (QACITS). Under the assumption of small phase aberrations, we show that the behaviour of the vortex phase mask can be simply described from the entrance pupil to the Lyot stop plane by Zernike polynomials. This convenient formalism is used to establish the theoretical basis of the QACITS technique. Simulations have been performed to demonstrate the validity and limits of the technique, including the case of a centrally obstructed pupil. The QACITS technique principle is further validated by experimental results in the case of an unobstructed circular aperture. The typical configuration of the Keck telescope (24% central obstruction) has been simulated with additional high order aberrations. In these conditions, our simulations show that the QACITS technique is still adapted to centrally obstructed pupils and performs tip-tilt retrieval with a precision of $5 \times 10^{-2}$ {\lambda}/D when wavefront errors amount to {\lambda}/14 rms and $10^{-2}$ {\lambda}/D for {\lambda}/70 rms errors (with {\lambda} the wavelength and D the pupil diameter). The implementation of the QACITS technique is based on the analysis of the scientific image and does not require any modification of the original setup. Current facilities equipped with a vortex phase mask can thus directly benefit from this technique to improve the contrast performance close to the axis. [less ▲]Detailed reference viewed: 12 (0 ULg) FLOR-ID: an interactive database of flowering-time gene networks in Arabidopsis thalianaBouché, Frédéric ; Lobet, Guillaume ; Tocquin, Pierre et alin Nucleic Acids Research (in press)Flowering is a hot topic in Plant Biology and important progress has been made in Arabidopsis thaliana toward unravelling the genetic networks involved. The increasing complexity and the explosion of ... [more ▼]Flowering is a hot topic in Plant Biology and important progress has been made in Arabidopsis thaliana toward unravelling the genetic networks involved. The increasing complexity and the explosion of literature however require development of new tools for information management and update. We therefore created an evolutive and interactive database of flowering time genes, named FLOR-ID (Flowering-Interactive Database), that is available freely at http://www.flor-id.org. The hand-curated database contains information on 306 genes and links to 1595 publications gathering the work of more than 4500 authors. Gene function and interactions within the flowering pathways were inferred from the analysis of related publications, included in the database and translated into interactive manually drawn snapshots. [less ▲]Detailed reference viewed: 128 (33 ULg) Carte géologique Huy-Nandrin (48/3-4): notice explicativeMottequin, Bernard ; Marion, Jean-Marc Book published by Université de Liège (in press)Detailed reference viewed: 128 (23 ULg) Carte géologique de Wallonie (Belgique) 1/10.000. 59/3 RochefortBarchy, Laurent; Dejonghe, Léon; Marion, Jean-Marc Cartographic material (in press)New geological map of Wallonia published at the scale of 1/25.000, based on a new field work and using previous scientific data, produced since the previous edition published in 1900 (Stainier)Detailed reference viewed: 213 (21 ULg) Minimalisme / musiques populaires : un cas pour la théorie de l’acteur-réseauLevaux, Christophe in Musimédiane (in press)Detailed reference viewed: 14 (0 ULg) Parametric Stein operators and variance boundsSwan, Yvik ; Ley, Christophein Brazilian Journal of Probability and Statistics (in press)Detailed reference viewed: 14 (2 ULg) GROMPALA: a membrane-implicit modelling method to screen lipid-interacting moleculesSteinhauer, Sven; Crowet, Jean-Marc ; Brasseur, Robert et alin Software and techniques for Bio-molecular modeling (in press)Detailed reference viewed: 9 (0 ULg) Constraints on the structure of 16 Cygni A and 16 Cygni B using inversion techniquesBuldgen, Gaël ; Reese, Daniel; Dupret, Marc-Antoine in Astronomy and Astrophysics (in press)Abstract Constraining mixing processes and chemical composition is a central problem in stellar physics as their impact on stellar age determinations leads to biases in our studies of stellar evolution ... [more ▼]Abstract Constraining mixing processes and chemical composition is a central problem in stellar physics as their impact on stellar age determinations leads to biases in our studies of stellar evolution, galactic history and exoplanetary systems. In two previous papers, we showed how seismic inversion techniques could offer strong constraints on such processes by pointing out weaknesses in theoretical models. We now apply our technique to the solar analogues 16CygA and 16CygB, being amongst the best targets in the Kepler field to test the diagnostic potential of seismic inversions. The combination of various seismic indicators helps to provide more constrained and accurate fundamendal parameters for these stars. We use the latest seismic, spectroscopic and interferometric observational constraints in the litterature for this system to determine reference models independently for both stars. We carry out seismic inversions of the acoustic radius, the mean density and a core conditions indicator. We note that a degeneracy exists for the reference models. Namely, changing the diffusion coefficient or the chemical composition within the observational values leads to 5% changes in mass, 3% changes in radius and up to 8% changes in age. We use acoustic radius and mean density inversions to improve our reference models then carry out inversions for a core conditions indicator. Thanks to its sensitivity to microscopic diffusion and chemical composition mismatches, we are able to reduce the mass dispersion to 2%, namely [0.96, 1.0] M_sun, the radius dispersion to 1%, namely [1.188, 1.200] R_sun and the age dispersion to 3%, namely [7.0, 7.4] Gy, for 16CygA. For 16CygB, we can check the consistency of the models but not reduce independently the age dispersion. Nonetheless, assuming consistency with the age of 16CygA helps to further constrain its mass and radius. [less ▲]Detailed reference viewed: 15 (1 ULg) CT SCAN FEATURES OF PRESUMPTIVE HAEMORRHAGIC STROKE IN A DOG WITH CUSHING’S DISEASELiotta, Annalisa Pia ; Cavrenne, Romain; Peeters, Dominique et alin Case reports in Veterinary Medicine (in press)Detailed reference viewed: 31 (3 ULg) Fernand De Visscher et la Société Internationale d'Histoire des Droits de l'AntiquitéGerkens, Jean-François in Revue Historique de Droit Français et Etranger (in press)Detailed reference viewed: 76 (10 ULg) A PHEROMONE TRAP MONITORING SYSTEM FOR THE SADDLE GALL MIDGE, Haplodiplosis marginata (von Roser) (DIPTERA: CECIDOMYIIDAE)Censier, Florence ; Heuskin, Stéphanie ; SAN MARTIN Y GOMEZ, Gilles et alin Crop Protection (in press)Outbreaks of saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae) have been reported in Belgium and other European countries since 2010. Because of the sporadic nature of this ... [more ▼]Outbreaks of saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae) have been reported in Belgium and other European countries since 2010. Because of the sporadic nature of this pest, which can sometimes be very harmful to cereal crops, an effective monitoring tool is required, both to determine the optimal timing for insecticide applications, and to understand the enigmatic population dynamics of this insect. Following the recent identification of the major sex pheromone component of the saddle gall midge, non-2-yl butanoate, a slow-release dispenser was developed using rubber septa. The release rates of 5 mg and 10 mg-loaded dispensers were initially measured under laboratory conditions, and their effectiveness in terms of pheromone loading and use duration was assessed in the field. The experiments showed that sticky traps baited with 5 mg pheromone-loaded rubber dispensers, renewed every 6 weeks, are suitable for accurately monitoring male H. marginata flights. [less ▲]Detailed reference viewed: 30 (8 ULg) Virtual reality as a complementary therapy to sexual addiction treatmentCismaru Inescu, Adina; Andrianne, Robert ; Triffaux, Jean-Marc in International Journal of Advanced Computer Science (in press), 3(7), 1-5Detailed reference viewed: 122 (32 ULg)