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See detailAn Ant Colony System for Responsive Dynamic Vehicle Routing
Schyns, Michael ULg

in European Journal of Operational Research (2015), 245(3), 704-718

We present an algorithm based on an Ant Colony System to deal with a broad range of Dynamic Capacitated Vehicle Routing Problems with Time Windows, (partial) Split Delivery and Heterogeneous fleets ... [more ▼]

We present an algorithm based on an Ant Colony System to deal with a broad range of Dynamic Capacitated Vehicle Routing Problems with Time Windows, (partial) Split Delivery and Heterogeneous fleets (DVRPTWSD). Besides the traditional distance criterion, we address the important case of responsiveness. Responsiveness is defined here as completing a delivery as soon as possible, within the time window, such that the client or the truck may restart its activities. This is crucial for many production or service activities in different fields: express parcel deliveries, taxi services, Just in Time production, express repair services, medical care, petrol station replenishment, etc. We develop an interactive web-based solution to allow dispatchers to take new information into account in real-time. The algorithm and its parametrization were tested on real and artificial instances. We first illustrate our approach with a problem submitted by Liege Airport, the 8th biggest cargo airport in Europe. The goal is to develop a decision system to optimize the journey of the refueling trucks. We then consider some classical VRP benchmarks with extensions for more complex problems. [less ▲]

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See detailVocabulaire liturgique et strates lexicales en indo-iranien ancien
Swennen, Philippe ULg

Conference (2015, September 16)

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See detailA General Review of Model Order Reduction Techniques for Magnetodynamic Problems
Paquay, Yannick ULg

Scientific conference (2015, September 15)

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See detailEfficient and Precise Trajectory Planning for Nonholonomic Mobile Robots
Lens, Stéphane ULg

Doctoral thesis (2015)

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis ... [more ▼]

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis presents an original and complete solution to tackle the motion planning problem for nonholonomic mobile robots in two-dimensional space. Given a set of obstacles, an initial and a goal configuration, the problem consists in computing efficiently a physically feasible trajectory that reaches the specified target as fast as possible. One of the original aspects of this work lies in the decomposition of the general problem into several simpler subproblems, for which very efficient solutions are developed. Their combination provides a complete trajectory planning approach that is one of the most computationally effective method suited for the motion of cylindrically shaped wheeled mobile robots in the presence of polygonal obstacles. This complete solution consists of three main steps. The first one is aimed at finding a short path that avoids obstacles and manages to reach the destination, without taking into account nonholonomic constraints of the robot. Our path planning method relies on an original refinement procedure of a constrained Delaunay triangulation of the obstacles, that outperforms other existing planning techniques. The second step consists in interpolating paths into smooth curves that can be followed by a real robot without slowing down excessively. By joining only two arcs of clothoids for moving from one curvature to another, our approach is simpler and also computationally cheaper than other interpolation methods. Finally, thanks to the introduction of an original discretization scheme, an efficient algorithm for computing a time-optimal speed profile for arbitrary paths is presented. The speed profile that results from this procedure not only allows the robot to follow the synthesized path as fast as possible while taking into account a broad class of velocity and accelerations constraints, but also provides the accurate advance information necessary to implementing coordinated actions during the displacement of the robot (e.g., between the locomotion system and other actuators). [less ▲]

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See detailEmpirical comparison of scoring rules at early stages of CAT
Magis, David ULg

Conference (2015, September 15)

Usual scoring rules in CATs include maximum likelihood (ML), weighted likelihood (WL) and Bayesian approaches. However, at early stages of adaptive testing, only a few item responses are available so the ... [more ▼]

Usual scoring rules in CATs include maximum likelihood (ML), weighted likelihood (WL) and Bayesian approaches. However, at early stages of adaptive testing, only a few item responses are available so the amount of information is very limited and in addition constant patterns (i.e. only correct or only incorrect responses) are often observed, yielding ML scoring intractable. Specific scoring rules (such as fixed- or variable stepsize adjustments) were developed for that purpose. However recent research highlighted that both Bayesian and WL scoring rules may provide finite values even with small sets of items. The purpose of this presentation is twofold: (a) to make a quick review of available scoring rules at early stages of CAT, and (b) to present empirical results from a simulation study that compares those scoring rules. More precisely, three scoring scenarios will be investigated: stepsize adjustment followed by ML, Bayes or WL followed by ML, and constant scoring rule throughout the CAT. These methods will be compared by means of simulated item banks and under various CAT scenarios for next item selection and stopping rules. Empirical results will be presented and practical guidelines for early stage scoring will be outlined. [less ▲]

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See detailAnnotations as reflection amplifiers in online learning - An exploratory study
Verpoorten, Dominique ULg; Specht, Marcus; Westera, Wim

in Ullmann, T; Kravcik, M; Mikroyannidis, A (Eds.) et al Proceedings of the 5th Workshop on Awareness and Reflection in Technology-Enhanced Learning (ARTEL). In conjunction with the 10th european conference on technology enhanced learning: Design for teaching and learning in a networked world. (2015, September 15)

In a controlled experiment on the effects of frequent and local digital annotations, 137 volunteers covered an online course at 3 conditions: no/free/question-based electronic annotations. Results show no ... [more ▼]

In a controlled experiment on the effects of frequent and local digital annotations, 137 volunteers covered an online course at 3 conditions: no/free/question-based electronic annotations. Results show no difference in performance between groups. However, analyses conducted within treatments suggest positive impacts on performance when annotation rates are taken into consideration, and coupled with other reflective enactments. [less ▲]

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See detailOrigin of high-frequency TEC disturbances observed by GPS over the European mid-latitude region
Wautelet, Gilles ULg; Warnant, René ULg

in Journal of Atmospheric and Solar-Terrestrial Physics (2015)

High-frequency variability of the ionospheric Total Electron Content (TEC) can strongly affect precise positioning with GNSS. The occurrence rate as well as the amplitude of such disturbances has been ... [more ▼]

High-frequency variability of the ionospheric Total Electron Content (TEC) can strongly affect precise positioning with GNSS. The occurrence rate as well as the amplitude of such disturbances has been extensively studied over the last decade. Mainly, one can distinguish disturbances due to space-weather events and the others, qualified as “quiet-time” as they are observed during quiet geomagnetic conditions. The latter, which represent more than 75% of the total number of disturbances over mid-latitudes, are then divided into two categories: the Winter Daytime (WD) and the Summer Nighttime (SN). The first category, representing the bulk of quiet-time disturbances, corresponds to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), that are the result of the interaction of gravity waves and the ionospheric plasma. On the other hand, SN disturbances are generally understood as non-classical MSTIDs of electrical origin. The paper investigates the origin of these two types of disturbance based on GPS measurements, ionospheric soundings and wind speed data at a tropospheric level. If one cannot exclude the solar terminator as a potential source of gravity waves responsible for WD events, it is thought that the major contribution comes from the lower atmosphere. More precisely, tropospheric jetstream is considered as the favorite candidate for daytime MSTIDs. Turning to SN disturbances, our analysis reveals that they are related to spread-F phenomenon, linked to the appearance of sporadic E-layers. The related instabilities are responsible for field-aligned irregularities in the F-region, which are thought to be responsible for noise-like fluctuations of the GPS TEC observed during SN events. [less ▲]

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See detailTowards processes-based groundwater vulnerability assessments
Dassargues, Alain ULg; Popescu, Cristina; Brouyère, Serge ULg

Conference (2015, September 15)

Various groundwater vulnerability methods have recently been developed. Considering groundwater quality issues, the most common techniques are based on calculation of an index expressing the protective ... [more ▼]

Various groundwater vulnerability methods have recently been developed. Considering groundwater quality issues, the most common techniques are based on calculation of an index expressing the protective effect (i.e. in terms of solute contaminant transport) of underground formations overlying the groundwater resource (Gogu & Dassargues, 2000, Gogu et al., 2003)). However, there is a strong need for new methods giving more emphasis on the processes-based calculation of vulnerability indicators. As a first alternative, a method is proposed based on three factors describing a pollution event (Brouyère et al., 2001): (1) the transit time from the source to the target, (2) the duration of the contamination breakthrough at the target, (3) the ratio between the maximum concentration at the target to the released concentration at the contamination source. The method can feature the impact of surface runoff to preferential infiltration points. Practically, the assessment can then be based on the simulated breakthrough curves at the ‘target’ corresponding to Dirac-type solicitations (Popescu et al., 2008). Different vulnerability maps can be built according to the relative importance conventionally given to each of the three factors. This concept allows a clear distinction between conventional aspects and processes-based results in the building of a final vulnerability indicator. A second proposal consists in reframing the groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers (Beaujean et al., 2013). The method is here based on the calculation of sensitivity coefficients for a user-defined groundwater state for which several physically-based indicators are proposed. The sensitivity coefficients reflect the easiness with which the groundwater state transmits pressures into impacts. They are converted to vulnerability, using the concept of ‘transgressing a given threshold’ (Luers et al., 2003). While the methodology is general and can be applied in quantity as quality issues, the choice of causal chains has to be made prior to the calculation. The vulnerability is also related to a damaged state and is related to the ‘distance’ between the current state and a given threshold. Here also, the method allows a clear distinction between conventional choices (threshold) and scientific work (Dassargues et al., 2009). [less ▲]

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See detailLearning to look - Purpose and design of an awareness-raising online course in veterinary sciences
Tasnier, Sophie ULg; Busoni, Valeria ULg; Hanzen, Christian ULg et al

in Prilla, M; Ullmann, T; Kravcik, M (Eds.) et al Proceedings of the 5th Workshop on Awareness and Reflection in Technology-Enhanced Learning (2015, September 15)

This paper reports on a work in progress: an online self-instruction course created to stimulate students’ awareness processes when dealing with pictures. Using non-clinical material, the “Learning to ... [more ▼]

This paper reports on a work in progress: an online self-instruction course created to stimulate students’ awareness processes when dealing with pictures. Using non-clinical material, the “Learning to Look” course was de-signed as a preliminary training to the observation of histological sections, radi-ological graphs, and other specialized visual material. Following a presentation of the project, salient results of a feedback questionnaire completed by 382 stu-dents about their experience of the course are provided. [less ▲]

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See detailLe passé à travers le prise du présent
Grandjean, Geoffrey ULg

Article for general public (2015)

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See detailAnalyse du déterminisme génétique de l’inhibition de la synthèse du gossypol dans la graine chez la descendance de l’hybride [(Gossypium hirsutum L. x G. raimondii Ulb.)² x G. sturtianum Willis]
Diouf, Fatimata Bintou Hassédine ULg

Doctoral thesis (2015)

Several analyses were performed in advanced generations of HRS [(Gossypium hirsutum x G. raimondii) ² x G. sturtianum] hybrid. These were obtained by backcrossing and selfing HRS plants expressing the ... [more ▼]

Several analyses were performed in advanced generations of HRS [(Gossypium hirsutum x G. raimondii) ² x G. sturtianum] hybrid. These were obtained by backcrossing and selfing HRS plants expressing the glanded-plant and glandless-seed trait of G. sturtianum. The purpose is to understand why it is not possible to fix this target character in the HRS progeny. Thus, HRS BC2S5, BC2S6, BC2S7, BC3S4, ♂BC4S3, ♂BC4S4, ♀BC4S3 and ♀BC4S4 plant populations were studied. Agro-morphological observations carried out on the studied plant material showed in all analyzed progenies significant fertility problems as manifested by high rates of embryo abortion, poor germination of seeds and premature mortality of many seedlings. Moreover, major phenotypic differences were observed between the HRS plants and upland cotton. Genomic in situ hybridization analysis (GISH) demonstrated that the magnitude of these problems is related to the importance of the presence of genetic material of the Australian species in HRS hybrids. The analysis of the plant material with the 10 SSRs markers, mapped on c2-c14, c3-c17, and c6-c25 linkage groups of G. hirsutum, points out very important segregation distortions (SD). Genotypic profiles were almost always heterozygous. These SD are caused by gametic and/or zygotic selections that occur respectively before and/or after fertilization. GISH showed the presence of one (1) to four (4) whole G. sturtianum chromosomes and one to two large fragments of G. sturtianum chromosomes. This structural heterozygosity is implicated in the SD observed. However, the massive presence of alien genetic material hardly affected the chromosome pairing and pollen fertility of the analyzed hybrid plants. This is contradictory to the observed SD and suggests a certain genetic balance in the analysed hybrids. It thus indicates no, or very weak interaction between the chromosomes of G. sturtianum and those of G. hirsutum into the genome of HRS derivatives. The expression of the desired character is very complex, but it is certain that: (i) the factors responsible for the desired trait are better transmitted through the ovule than the pollen, (ii) the alleles involved in the expression of the target trait operate both according to the additive and epistatic models, (iii) the increase of the G. hirsutum genetics background in the most advanced generations of the HRS hybrid is accompanied by a decrease of the expression of the desired trait, (iv) seeds viability problems affect both seeds with or without gossypol glands, whether they are well formed or malformed, showing the independence between at least a part of the imbalance factors and those related to the expression of researched character. Several G. sturtianum genes appear to be involved in the control of the target trait. However, the strong SD that characterizes the analyzed plants questions the reliability of this result obtained through single-marker analysis. A resumption of the breeding program using agro-morphological characterization tools, SSR and GISH, in the early generations of backcrossing, should help to better guide the selection program towards obtaining stable plants that express the character. [less ▲]

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See detailCorporate Board Attributes and CAC: A Comparative Study of France, Germany and UK
Boussaid, Nabila ULg; Hamza, Taher; Sougné, Danielle ULg

Conference (2015, September 14)

This paper investigates the impact of corporate board of directors’ attributes on conditional accounting conservatim in the French, German and British contexts. Using pooled regression model over the ... [more ▼]

This paper investigates the impact of corporate board of directors’ attributes on conditional accounting conservatim in the French, German and British contexts. Using pooled regression model over the period 2009-2012, our findings report that the relationship between corporate board attributes and accounting conservatism is country dependent. First, regarding the board composition, we find that the effect of board size is positive for German firms, negative for French firms and insignificant for British firms. We also document a positive association between board independence and accounting conservatism for British firms. However, we find no evidence of a positive association between codetermination and earnings conservatism in German context. Second, female seats on board seem to increase conservative reporting in financial statement only for French firms. Lastly, board meeting frequency in French and British firms appears to increase accounting conservatism. As a robustness test, we use an alternative measure of accounting conservatism namely, time–series of earnings changes measure and confirm the previous results. Overall, our results reveal that corporate board affects the financial reporting quality. [less ▲]

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See detailSharing in neuroimaging: collecting with Brainmap, quantitatively analysing and sharing with ANIMA
Genon, Sarah ULg; Reid, Andrew; Eickhoff, Simon

Conference (2015, September 14)

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See detailThe Red Marble of Baelen, an exceptional mid-Famennian mud mound complex in a carbonate ramp setting from Eastern Belgium
Dreesen, Roland; Vachard, Daniel; Marion, Jean-Marc ULg et al

Poster (2015, September 14)

The Red Marble of Baelen from the Limbourg area (Vesdre Basin, Eastern Belgium) represents a member of the middle Famennian (late Upper Devonian) Souverain-Pré Formation (Late marginifera conodont Zone ... [more ▼]

The Red Marble of Baelen from the Limbourg area (Vesdre Basin, Eastern Belgium) represents a member of the middle Famennian (late Upper Devonian) Souverain-Pré Formation (Late marginifera conodont Zone). It corresponds to a short-term transgressive event and eustatic rise during the Famennian, interrupting the regressive megasequence on the Condroz shelf in Belgium. It is the only known or at least the only well-documented mid-Famennian carbonate mud mound complex worldwide, after the end-Frasnian mass extinction that wiped out numerous invertebrate taxa. [less ▲]

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See detailPt-Ni Hollow Nanoparticles for Oxygen Reduction Reaction : Controlling the Nanoparticle Morphology
Asset, Tristan ULg; Zubiaur, Anthony ULg; Chattot, Raphael et al

Poster (2015, September 13)

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See detailBande dessinée et "sonorités graphiques"
Dejasse, Erwin ULg

Conference given outside the academic context (2015)

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See detailL'abstraction dans les bandes dessinées d'Ephameron et d'Olivier Schrauwen
Crucifix, Benoît ULg; Meesters, Gert

Conference given outside the academic context (2015)

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See detail18FDG-PET/CT IMAGING IN SUSPECTED ACUTE RENAL ALLOGRAFT REJECTION
LOVINFOSSE, Pierre ULg; WEEKERS, Laurent ULg; BOVY, Christophe ULg et al

Conference (2015, September 13)

The diagnosis procedure for kidney transplant recipients (KTR) with suspected acute rejection (AR) relies on needle biopsy. Noninvasive tests to predict nonrejection would be preferable. AR is associated ... [more ▼]

The diagnosis procedure for kidney transplant recipients (KTR) with suspected acute rejection (AR) relies on needle biopsy. Noninvasive tests to predict nonrejection would be preferable. AR is associated with a recruitment of activated leukocytes into the transplant, which are characterized by a high metabolic activity and an increased uptake of glucose analog, Fluoro-deoxyglucose ( FDG). Thus, FDG-Positron emission tomography coupled with computed tomography (PET/CT) may help noninvasively distinguish nonrejection from AR. From January 2013 to February 2015, we prospectively performed 32 FDGPET/ CT in 31 adult KTR with suspected renal AR who underwent a biopsy. Biopsies were categorized as “normal”, “borderline”, “AR” or “others” according to Banff classification. PET/CT imaging was performed within 201 ± 18 minutes after i.v. administration of 3.2 ± 0.2 MBq/kg of FDG, before any modification of immunosuppression. The mean standard uptake values (SUV) of both upper and lower renal poles were measured, with no threshold activity. Biopsies were diagnosed as “normal”, “borderline”, “AR” or “others” in 8, 10, 8 and 6 (including 3 polyoma-BK nephropathies) cases. Mean SUV respectively reached 1.5 ± 0.2, 1.6 ± 0.3, 2.9 ± 0.8, 2.2 ± 1.2 in each category. Mean SUV of biopsy-proven AR was significantly higher than “normal” cases (p<0.01). No difference was found between “normal” vs. “borderline”, or between “AR” vs. “others” histopathology. Still, a positive correlation between mean SUV and acute composite (g+i+t+v+ptc) Banff score was found, with a coefficient of 0.70 (p<0.001). Sensitivity and specificity of FDG-PET/CT in detecting pathological biospies were respectively 92.3% and 36.8%, with a mean SUV threshold at 1.4. FDG-PET/CT imaging may help discriminate nonrejection, thereby avoiding unnecessary transplant biopsy in KTR with suspected AR. [less ▲]

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