Last 7 days     Results 1581-1600 of 67333.   75 76 77 78 79 80 81 82 83 84 85   An Improved On-line Contingency Screening for Power System Transient Stability AssessmentWeckesser, Johannes ; Jóhannsson, Hjörtur; Glavic, Mevludin et alin Electric Power Components & Systems (2017)This paper presents a contingency screening method and a framework for its on-line implementation. The proposed method carries out contingency screening and on-line stability assessment with respect to ... [more ▼]This paper presents a contingency screening method and a framework for its on-line implementation. The proposed method carries out contingency screening and on-line stability assessment with respect to first-swing transient stability. For that purpose, it utilizes the single machine equivalent method and aims at improving the prior developed contingency screening approaches. In order to determine vulnerability of the system with respect to a particular contingency, only one time-domain simulation needs to be performed. An early stop criteria is proposed so that in a majority of the cases the simulation can be terminated after a few hundred milliseconds of simulated system response. The method’s outcome is an assessment of the system’s stability and a classification of each considered contingency. The contingencies are categorized by exploiting parameters of an equivalent one machine infinite bus system. A novel island detection approach, appropriate for an on-line application since it utilizes efficient algorithms from graph theory and enables stability assessment of individual islands, is also introduced. The New England and New York system as well as the large-scale model of the Continental-European interconnected system are used to test the proposed method with respect to assessment accuracy and computation time. [less ▲]Detailed reference viewed: 25 (6 ULg) SAFIR: a software for modeling structures in fireFranssen, Jean-Marc ; Gernay, Thomas Poster (2017, May 02)SAFIR is a computer program developed at University of Liege to model the behavior of building structures subjected to fire.Detailed reference viewed: 32 (2 ULg) Hybrid Fire Testing: A new approach for fire labsSauca, Ana ; Gernay, Thomas ; Mergny, Elke et alPoster (2017, May 02)Detailed reference viewed: 21 (3 ULg) La représentation des mythes grecs sur la céramique apulienne (IVe s. av. J.-C.). Modes d'emploiMorard, Thomas Scientific conference (2017, May 02)Detailed reference viewed: 11 (1 ULg) Wal-e-CitiesSchelings, Clémentine ; Reiter, Sigrid ; Teller, Jacques et alPoster (2017, May 02)L’objectif du portefeuille FEDER Wal-e-Cities est le développement de villes intelligentes («Smart Cities») au sein d’un territoire wallon interconnecté. La technologie, vue ici comme un outil au service ... [more ▼]L’objectif du portefeuille FEDER Wal-e-Cities est le développement de villes intelligentes («Smart Cities») au sein d’un territoire wallon interconnecté. La technologie, vue ici comme un outil au service de la Smart Région Wallonne et de ses citoyens, permettra de répondre à cinq défis principaux identifiés: connectivité, mobilité, énergie et environnement, gouvernance et enfin bien-être en environnement urbain. Les partenaires de ce portefeuille (Universités et Centres de Recherche), et parmi eux l’UR Urban & Environmental Engineering de l'Ulg, oeuvreront au déploiement de solutions dédiées en regard des besoins spécifiques (géographiques, démographiques, socio-économiques et culturels) de chaque ville pilote partenaire. [less ▲]Detailed reference viewed: 37 (7 ULg) Surrogate Generation and Evaluation for Biodiesel and Its Mixtures with Fossil DieselReiter, Anton M.; Schubert, Nikolai; Pfennig, Andreas et alin Energy & Fuels (2017), 31In this paper a precedently developed surrogate optimization algorithm for fossil fuels, which originally allowed simultaneous fitting of the true boiling point (TBP) curve, the liquid density at 15 °C ... [more ▼]In this paper a precedently developed surrogate optimization algorithm for fossil fuels, which originally allowed simultaneous fitting of the true boiling point (TBP) curve, the liquid density at 15 °C, and the cetane number, is refined toward its application to biodiesel and its mixtures with fossil diesel. For this purpose, the algorithm is extended (1) to also include fitting of the kinematic viscosity at 40 °C and (2) to account for peculiarities of biodiesel concerning its narrow boiling range and compensation of systematic errors of measured boiling curves. To illustrate these improvements, first, the algorithm is applied to property estimation and surrogate optimization of three different biodiesel fuels, for which surrogates consisting of one to three components are proposed. Second, a surrogate for a commercial European fossil diesel is calculated and produced in lab-scale. Finally, the algorithm is used for surrogate optimization and property estimation of mixtures of biodiesel and fossil diesel, considering fractions of biodiesel of 7% and 20% per volume. It is shown that the improved algorithm is capable of reliably optimizing surrogates for fuels containing both biogenic and fossil components. [less ▲]Detailed reference viewed: 12 (2 ULg) Gestion du changement organisationnel lié à la mise en oeuvre des TIC dans les Douanes africaines: Etude du cas du PVS dans les Douanes ivoiriennes.N'Dri, Koffi Jacques Doctoral thesis (2017)Given the importance of customs revenues in the budgets of African countries, the use of Information and Communication Technologies (ICT) in order to adapt techniques and methods of control to the needs ... [more ▼]Given the importance of customs revenues in the budgets of African countries, the use of Information and Communication Technologies (ICT) in order to adapt techniques and methods of control to the needs of facilitation of international trade is a major challenge. In this context, this work investigates what become of the technical potentialities of ICTs when confronted to the contextual characteristics of the environment in which they are to be implemented. This is the main purpose of this research that is based on the study of the case of the PVS system in the Customs administration of Côte d’Ivoire. The work is a unique "embedded" case study, in an interpretativist epistemological positioning and an abductive approach. It feeds on data from various sources; but, it is based mainly on semi-structured interviews. The research uses the Actor Network Theory (ANT) as a framework for observation and thematic analysis. The general result is that, the system is implemented but it lacks to convey organizational transformations and coexists with former manual practices. By discussion of these results, two original contributions are made concerning the factors that influence the effective realization of the objectives of organizational change related to ICT implementation in the African Customs. On the one hand, contrary to the national cultural differentiation perspective that is often used in similar work in the African context, the research points out the important role of organizational variables; namely, organizational cultural values. And, on the other hand, in line with its interpretativist positioning, the research underlines the way the process is managed as a determining factor for the results that come out. So, at the managerial level, research highlights the shortcomings of the “top-down” style of management. But above all, from this perspective, it proposes concrete ways of correcting these deficiencies through three recommendations: the application of a polyphonic management model (based on the principles of ANT); the reduction of cultural conflicts; and the rooting of managerial instrumentation in the cultural characteristics of the social environment. [less ▲]Detailed reference viewed: 19 (1 ULg) Trace elements and organochlorines in sperm whales stranded on the coast of Schleswig Holstein in 2016Pinzone, Marianna ; Schnitzler, Joseph ; Thomé, Jean-Pierre et alPoster (2017, May 02)Several strandings of sperm whales occurred in the North Sea during January and February 2016. Twelve animals were necropsied and sampled after their discovery on German coasts of Schleswig Holstein ... [more ▼]Several strandings of sperm whales occurred in the North Sea during January and February 2016. Twelve animals were necropsied and sampled after their discovery on German coasts of Schleswig Holstein. Muscle, liver, kidney and blubber samples were taken from all specimens for toxicological analyses. The concentrations of lipophilic organic pollutants such as polychlorinated biphenyl (PCB) and pesticides such as DDT were determined in adipose tissue. Metals and trace elements such as cadmium, selenium and mercury were measured in the liver, kidney and muscle. Polychlorinated biphenyls (PCBs) and pesticides such as DDTs were determined in adipose tissue at levels of 0.9 and 1.3 mg.kg-1 lipid weight respectively. Cadmium, selenium and mercury were measured in the liver at respective concentrations of 57, 52 and 81 mg.kg-1 dry weight. The investigated 12 sperm whales stranded on the coasts of Schleswig Holstein in spring 2016 showed a lower contamination of organic pollutants than the 7 sperm whales stranded along the Belgian and Dutch coast in the winter of 1994/95. These animals were clearly larger and older than the ones that stranded in Schleswig-Holstein. So, lower contaminant burden may be due to shorter life span. It seems unlikely that contamination is the direct cause of the death of sperm whales. However, debilitating role of pollutants cannot be excluded, as strandings are often a multi factorial event. Further investigations on the contaminant patterns among the 30 sperm whales at different stranding sites may also give indications on the feeding strategy and linkage among the individuals. [less ▲]Detailed reference viewed: 24 (4 ULg) π Aquarii is another γ Cassiopeiae objectNazé, Yaël ; Rauw, Grégor ; Cazorla, Constantin in Astronomy and Astrophysics (2017), 602The γ Cas category is a subgroup of Be stars displaying a strong, hard, and variable thermal X-ray emission. An XMM-Newton observation of π Aqr reveals spectral and temporal characteristics that clearly ... [more ▼]The γ Cas category is a subgroup of Be stars displaying a strong, hard, and variable thermal X-ray emission. An XMM-Newton observation of π Aqr reveals spectral and temporal characteristics that clearly make this Be star another member of the γ Cas category. Furthermore, π Aqr is a binary but, contrary to γ Cas, the nature of the companion to the Be star is known; it is a non-degenerate (stellar) object and its small separation from the Be star does not leave much room for a putative compact object close to the Be disk. This renders the accretion scenario difficult to apply in this system, and, hence, this discovery favors a disk-related origin for the γ Cas phenomenon. Based on observations collected with the ESA science mission XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]Detailed reference viewed: 18 (3 ULg) Identification of non-stationary dynamical systems using multivariate ARMA modelsBertha, Mathieu ; Golinval, Jean-Claude in Mechanical Systems and Signal Processing (2017), 88This paper is concerned by the modal identification of time-varying mechanical systems. Based on previous works about autoregressive moving average models in vector form (ARMAV) for the modal ... [more ▼]This paper is concerned by the modal identification of time-varying mechanical systems. Based on previous works about autoregressive moving average models in vector form (ARMAV) for the modal identification of linear time invariant systems, and time-varying autoregressive moving average models (TV-ARMA) for the identification of nonstationary systems, a time-varying ARMAV (TV-ARMAV) model is presented for the multivariate identification of time-varying systems. It results in the identification of not only the time-varying poles of the system but also of its respective time-varying mode shapes. The method is applied on a time-varying structure composed of a beam on which a mass is moving. [less ▲]Detailed reference viewed: 35 (8 ULg) In vitro biphasic dissolution tests and their suitability for establishing in vitro-in vivo correlations: A historical reviewPestieau, Aude ; Evrard, Brigitte in European Journal of Pharmaceutical Sciences (2017), 102For many decades, one of the most critical issues in the pharmaceutical industry has been the poor solubility of some drugs. Indeed, a prerequisite for drug absorption is the presence of dissolved drug at ... [more ▼]For many decades, one of the most critical issues in the pharmaceutical industry has been the poor solubility of some drugs. Indeed, a prerequisite for drug absorption is the presence of dissolved drug at the absorption site and this can be challenging for compounds with low aqueous solubility such as BCS class II (low solubility, high permeability) and IV (low solubility, low permeability) compounds. If the development of oral delivery formulations of these compounds is frequently challenging to formulation scientists in the pharmaceutical industry, the in vitro evaluation of these new formulations is also a great challenge. One alternative approach to overcome the problems encountered with conventional dissolution methods is the use of biphasic dissolution systems. This review provides an overview of the origin and the evolution over time of the biphasic systems and the growing interest among scientists regarding their suitability for establishing in vitro-in vivo correlations. The evolution of these systems and their applications from the 1960s to the present day, such as in system variants and improvements, analysis of complex formulations, discriminatory power, bio-relevance, precipitation and supersaturation visualization, etc. will be discussed. [less ▲]Detailed reference viewed: 24 (5 ULg) Anesthesia Case of the MonthTutunaru, Alexandru-Cosmin ; Sandersen, Charlotte in Journal of the American Veterinary Medical Association [=JAVMA] (2017), 250(9), 984-987Detailed reference viewed: 45 (2 ULg) Ambiguities in gravitational lens models: the density field from the source position transformationUnruh, Sandra; Schneider, Peter; Sluse, Dominique in Astronomy and Astrophysics (2017), 601Strong gravitational lensing is regarded as the most precise technique to measure the mass in the inner region of galaxies or galaxy clusters. In particular, the mass within one Einstein radius can be ... [more ▼]Strong gravitational lensing is regarded as the most precise technique to measure the mass in the inner region of galaxies or galaxy clusters. In particular, the mass within one Einstein radius can be determined with an accuracy of the order of a few percent or better, depending on the image configuration. For other radii, however, degeneracies exist between galaxy density profiles, precluding an accurate determination of the enclosed mass. The source position transformation (SPT), which includes the well-known mass-sheet transformation (MST) as a special case, describes this degeneracy of the lensing observables in a more general way. In this paper we explore properties of an SPT, removing the MST to leading order, that is we consider degeneracies which have not been described before. The deflection field \ahat(čθ) resulting from an SPT is not curl-free in general, and thus not a deflection that can be obtained from a lensing mass distribution. Starting from a variational principle, we construct lensing potentials that give rise to a deflection field \atilde, which differs from \ahat by less than an observationally motivated upper limit. The corresponding mass distributions from these "valid" SPTs are studied: their radial profiles are modified relative to the original mass distribution in a significant and non-trivial way, and originally axi-symmetric mass distributions can obtain a finite ellipticity. These results indicate a significant effect of the SPT on quantitative analyses of lens systems. We show that the mass inside the Einstein radius of the original mass distribution is conserved by the SPT; hence, as is the case for the MST, the SPT does not affect the mass determination at the Einstein radius. Furthermore, we analyse a degeneracy between two lens models, empirically found previously, and show that this degeneracy can be interpreted as being due to an SPT. Thus, degeneracies between lensing mass distributions are not just a theoretical possibility, but do arise in actual lens modeling. [less ▲]Detailed reference viewed: 18 (3 ULg) A threshold-based weather model for predicting stripe rust infection in winter wheatEl Jarroudi, Moussa ; Kouadio, Louis; Bock, Clive et alin Plant Disease (2017), 101(693-703), Wheat stripe rust (caused by Puccinia striiformis f. sp. tritici) is a major threat in most wheat growing regions worldwide, which potentially causes substantial yield losses when environmental conditions ... [more ▼]Wheat stripe rust (caused by Puccinia striiformis f. sp. tritici) is a major threat in most wheat growing regions worldwide, which potentially causes substantial yield losses when environmental conditions are favorable. Data from 1999-2015 for three representative wheat-growing sites in Luxembourg were used to develop a threshold-based weather model for predicting wheat stripe rust. First, the range of favorable weather conditions using a Monte Carlo simulation method based on the Dennis model were characterized. Then, the optimum combined favorable weather variables (air temperature, relative humidity, and rainfall) during the most critical infection period (May-June) was identified and was used to develop the model. Uninterrupted hours with such favorable weather conditions over each dekad (i.e., 10-day period) during May-June were also considered when building the model. Results showed that a combination of relative humidity > 92% and 4°C < temperature < 16°C for a minimum of 4 continuous hours, associated with rainfall ≤ 0.1 mm (with the dekad having these conditions for 5-20% of the time), were optimum to the development of a wheat stripe rust epidemic. The model accurately predicted infection events: probabilities of detection were ≥ 0.90 and false alarm ratios were ≤ 0.38 on average, and critical success indexes ranged from 0.63 to 1. The method is potentially applicable to studies of other economically important fungal diseases of other crops or in different geographical locations. If weather forecasts are available, the threshold-based weather model can be integrated into an operational warning system to guide fungicide applications. [less ▲]Detailed reference viewed: 38 (8 ULg) Study of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic featuresDias-Oliveira, A.; Sicardy, B.; Ortiz, J. L. et alin The Astronomical Journal (2017), 154(1), 13We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 ... [more ▼]We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ$_{84}$'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semi axes $(470 \pm 20) \times (383 \pm 10) \times (245 \pm 8)$~km % axis ratios $b/a= 0.82 \pm 0.05$ and $c/a= 0.52 \pm 0.02$, can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75~h) and the amplitude of its rotation light curve, we derive a density $\rho=0.87 \pm 0.01$~g~cm$^{-3}$ a geometric albedo $p_V= 0.097 \pm 0.009$. A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003~AZ$_{84}$'s limb, that can be interpreted as an abrupt chasm of width $\sim 23$~km and depth $> 8$~km or a smooth depression of width $\sim 80$~km and depth $\sim 13$~km (or an intermediate feature between those two extremes). [less ▲]Detailed reference viewed: 4 (1 ULg) 3D shape of asteroid (6)~Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondritesMarsset, M.; Carry, B.; Dumas, C. et alE-print/Working paper (2017)Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium ... [more ▼]Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D~100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history. Aims. We investigate here the collisional history of asteroid (6) Hebe and challenge the idea that Hebe may be the parent body of ordinary H chondrites, the most common type of meteorites found on Earth (~34% of the falls). Methods. We observed Hebe with SPHERE as part of the science verification of the instrument. Combined with earlier adaptive-optics images and optical light curves, we model the spin and three-dimensional (3D) shape of Hebe and check the consistency of the derived model against available stellar occultations and thermal measurements. Results. Our 3D shape model fits the images with sub-pixel residuals and the light curves to 0.02 mag. The rotation period (7.274 47 h), spin (343 deg,+47 deg), and volume-equivalent diameter (193 +/- 6km) are consistent with previous determinations and thermophysical modeling. Hebe's inferred density is 3.48 +/- 0.64 g.cm-3 , in agreement with an intact interior based on its H-chondrite composition. Using the 3D shape model to derive the volume of the largest depression (likely impact crater), it appears that the latter is significantly smaller than the total volume of close-by S-type H-chondrite-like asteroid families. Conclusions. Our results imply that (6) Hebe is not the most likely source of H chondrites. Over the coming years, our team will collect similar high-precision shape measurements with VLT/SPHERE for ~40 asteroids covering the main compositional classes, thus providing an unprecedented dataset to investigate the origin and collisional evolution of the asteroid belt. [less ▲]Detailed reference viewed: 2 (1 ULg) Gaia Data Release 1. Open cluster astrometry: performance, limitations, and future prospectsGaia Collaboration, ; van Leeuwen, F.; Vallenari, A. et alin Astronomy and Astrophysics (2017), 601Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and ... [more ▼]Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information.