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See detailSensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR
Noel, Brice; Fettweis, Xavier ULg; van de Berg, W.J. et al

in Cryosphere (The) (2014), 8

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North ... [more ▼]

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS. [less ▲]

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See detailProbabilistic Assessment of Lifetime of Low-Earth-Orbit Spacecraft: Uncertainty Propagation and Sensitivity Analysis
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Journal of Guidance Control & Dynamics (2014)

This paper is devoted to the probabilistic uncertainty quantification of orbital lifetime estimation of low-altitude satellites. Specifically, given a detailed characterization of the dominant sources of ... [more ▼]

This paper is devoted to the probabilistic uncertainty quantification of orbital lifetime estimation of low-altitude satellites. Specifically, given a detailed characterization of the dominant sources of uncertainty, we map this input into a probabilistic characterization of the orbital lifetime through orbital propagation. Standard Monte Carlo propagation is first considered. The concept of drag correction is then introduced to facilitate the use of polynomial chaos expansions and to make uncertainty propagation computationally effective. Finally, the obtained probabilistic model is exploited to carry out stochastic sensitivity analyses, which in turn allow gaining insight into the impact uncertainties have on orbital lifetime. The proposed developments are illustrated using one CubeSat of the QB50 constellation. [less ▲]

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See detailA Riemannian approach to large-scale constrained least-squares with symmetries
Mishra, Bamdev ULg

Doctoral thesis (2014)

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost ... [more ▼]

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost functions remain a popular way to model large-scale problems, the additional symmetry constraint should be interpreted as a way to make the modeling robust. Two fundamental examples are the matrix completion problem, a least-squares problem with rank constraints and the generalized eigenvalue problem, a least-squares problem with orthogonality constraints. The possible large-scale nature of these problems demands to exploit the problem structure as much as possible in order to design numerically efficient algorithms. The constrained least-squares problems are tackled in the framework of Riemannian optimization that has gained much popularity in recent years because of the special nature of orthogonality and rank constraints that have particular symmetries. Previous work on Riemannian optimization has mostly focused on the search space, exploiting the differential geometry of the constraint but disregarding the role of the cost function. We, on the other hand, propose to take both cost and constraints into account to propose a tailored Riemannian geometry. This is achieved by proposing novel Riemannian metrics. To this end, we show a basic connection between sequential quadratic programming and Riemannian gradient optimization and address the general question of selecting a metric in Riemannian optimization. We revisit quadratic optimization problems with orthogonality and rank constraints by generalizing various existing methods, like power, inverse and Rayleigh quotient iterations, and proposing novel ones that empirically compete with state-of-the-art algorithms. Overall, this thesis deals with exploiting two fundamental structures, least-squares and symmetry, in nonlinear optimization. [less ▲]

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See detailQuelles aides proposer aux victimes d’infractions ?
Garcet, Serge ULg

Article for general public (2014)

L'article propose un panorama de l'offre en matière d'aide aux victimes.

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See detailThe Airline Container Loading Problem with Pickup and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2014, October 19)

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at ... [more ▼]

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at intermediate airports, this problem is simultaneously a weight and balance problem and a sequencing problem. Our objective is to minimize fuel and handling operations costs. This problem is shown to be NP-hard. We resort to a mixed integer linear program. On the basis of a professional partner's real-world data, TNT Airways, we perform numerical experiments using a standard B&C library. This approach yields better solutions than traditional manual planning, which results in substantial cost savings. [less ▲]

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See detailSeasonal variations of wild boar Sus scrofa distribution in agricultural landscapes: a species distribution modelling approach
Morelle, Kevin ULg; Lejeune, Philippe ULg

in European Journal of Wildlife Research (2014)

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often ... [more ▼]

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often results in damages and makes control of the population difficult. The plasticity of the species to cope with different habitats is largely proven, but the environmental and human drivers of this seasonal habitat shift at the population scale remain largely unknown. Using MaxEnt and two seasonally distinct presence datasets, we contrasted the distribution of wild boar in southern Belgium during the growing and hunting seasons to (i) analyse seasonal drivers of the distribution and (ii) forecast the potential spread of the species north to its current distribution. We demonstrated that during the growing season, wild boar range almost double, owing to the cover and food provided by agricultural areas, thereby enhancing the movement and spread of the species. We found that the seasonal distribution of wild boar in agricultural lands is mostly influenced by the search for cover and food provided alternatively by forest and field crops. Interestingly, it seems that this search for cover operates under the constraint of a threshold distance. Our results indeed reveal an increased probability of presence not only in the vicinity of forests but also above a threshold distance of 865 m from the forest edge, suggesting that wild boar can overcome the dependence to forest cover. The forecast distribution of wild boar highlighted a potential increase of the current range into suitable habitat between 63 and 168 km2. To counteract the potential spread of the species into agricultural habitats and the consecutive damages, we insist on the need for the development of integrated management strategies, combining land use spatial configuration and wild boar spatial behaviour. [less ▲]

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See detailA novel mutation of the luteinizing hormone/choionic gonadotrophin receptor gene leading to Leydig cell hypoplasia type I
Potorac, Iulia ULg; Rivero-Müller, Adolfo; Pintiaux, Axelle ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailFamilial hypocalciuric hypercalcemia : a rare cause of recurrent pancreatitis
Daniel, Sara ULg; Potorac, Iulia ULg; MALAISE, Olivier ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailCharacterization of paragangliomas : a single center cohort study
VROONEN, Laurent ULg; Maiga, Ibrahima ULg; PETROSSIANS, Patrick ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailEffet de l'expertise musicale sur la perception de la justesse vocale
Gosselin, Laura; Morsomme, Dominique ULg; Larrouy, Pauline ULg

Poster (2014, October 17)

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See detailLocal goat in Kabylie (Chemini and Bouzeguene)
Moula, Nassim ULg; Michaux, Charles ULg; Philippe, François-Xavier ULg et al

Poster (2014, October 17)

The livestock sector plays a dynamic role in the economic development of rural areas in Algeria. Due to its adaptation to harsh environments, goat breeding is practiced in many areas of the country. To ... [more ▼]

The livestock sector plays a dynamic role in the economic development of rural areas in Algeria. Due to its adaptation to harsh environments, goat breeding is practiced in many areas of the country. To the north, it is confined to mountainous areas, but the bulk of the workforce is left in the steppe and semi-desert areas. The goat population in Algeria reached 3.8 million heads, ranking second after sheep. The present work contributes to a better characterisation of local goat in Kabylie for production and reproduction traits. The study was conducted in the regions of Chemini (Bejaia province) and Bouzeguene (Tizi-Ouzou province). A survey was conducted in 29 herds. The results revealed that the overall mean of goats per households was 6.69 ± 2.97. The purposes of keeping goat in Chemini and Bouzguene was private consumption of milk (82.76%) and meat (68.97%) as well as for commercial exchange (62.07%). The Kabyle goat is small (male: 62.23 cm and female: 58.41 cm) with long hair. Its ears are drooping, its convex profile has a slightly pronounced nasal split and its coat colour ranges from dark brown to black. However, the crossbreeding with exotic breeds (mainly with Saanen goat), controlled or uncontrolled, increased the frequency of white coat. The average age at puberty in males was 6.93 ± 1.04 and 7.38 ± 0.94 months in females. The reported age at first kidding and kidding interval were 13.03 ± 0.87 months and 7.83 ± 1.29 months, respectively. [less ▲]

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See detailThe effect of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler
Moula, Nassim ULg; Philippe, François-Xavier ULg; Michaux, Charles ULg et al

Poster (2014, October 17)

The objective of this study was to evaluate the effects of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler chicken. The study was ... [more ▼]

The objective of this study was to evaluate the effects of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler chicken. The study was conducted from May to June 2014 in the area of Chemini (Algeria). In a completely randomized design, a total of 100 one-day-old broilers (industrial strain) were divided into 2 groups and 2 repetitions with 25 chickens each. Group 1 was the control group fed a standard commercial diet based on corn and soybean purchased on the local market, whereas the birds in group 2 were fed the nettle diet (control diet with addition of 2% of nettle). The animals were housed inside in experimental pens and fed ad libitum. The results showed that nettle inclusion significantly promotes growth performance of broilers at 42 days of age (1644.8 ± 45.5 vs. 1565.1 ± 45.5g; P<0.05). The broilers fed the nettle diet had higher thigh yield (26.0 ± 0.3 vs. 25.2 ± 0.3%; P<0.05) but lower abdominal fat yield (4.39 ± 0.16 vs. 3.90 ± 0.16%; P<0.05). No significant effect of the diet was observed for carcass yield (around 71.1%) and breast percentage (around 32.40%). The overall mortality was not significantly different (P>0.05) for any of the dietary regimens (around 20%). Feed conversion ratio of the two groups were very close (around 2.17). This experiment showed that dietary inclusion of Urtica dioica has positive effects on growth performance and carcass quality of broilers. [less ▲]

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See detailThe Effect of Urtica dioica Supplements on Egg Quality
Touazi, Leghel; Moula, Nassim ULg

Poster (2014, October 17)

Eggs are a rich source of lipids and proteins. Because of their low production cost, they represent a cheap source of animal proteins and lipids. recently, in Algeria, consumers’ interest are oriented of ... [more ▼]

Eggs are a rich source of lipids and proteins. Because of their low production cost, they represent a cheap source of animal proteins and lipids. recently, in Algeria, consumers’ interest are oriented of healthiness and dietetic values food. The purpose of this study was to investigate the effects a dietary supplement of Urtica dioica on laying hen's performance and egg quality. The study was conducted from may to june 2014 in the area of Chemini (Algeria). Sixty, 25-wk-old Lohmann Brown layers were randomly divided into 3 groups with 20 hens in each group. Group 1 was the control group fed a standard commercial diet based on corn and soybean, whereas the groups 2 and 3 were fed the control diet supplemented with 1% and 1.5% of nettle respectively. The hens were housed in cages in the same local and fed ad libitum. Fifty five eggs were sampled 4 times in each group from 25 to 27 weeks. A total of 220 eggs were examined. A series of measurements were carried out on each egg, namely egg weight, form index (egg shape), yolk to albumen ratio (Y:A), Yolk color, egg shell thickness, Haugh’s units. Egg weight, yolk color and Haugh Units (HU) were affected by age. Significant differences (P<0.05) were recorded between feeding type in total egg weight, yolk color and Haugh Units. The egg from group 2 proved to have a higher egg weight (57.67g; group 1: 55.41g; group 3: 56.70g; P<0.05), (33.4%), intermediate Yolk color (8.53; group 1: 9.03 ; group 3: 9.38; P<0.05) and HU (79.81; group 1: 80.85; group 3: 76.92). The results showed that the use of 1% and 1.5% of Urtica dioica, had positive effects on the color of yolk of laying hens. Using different levels of Urtica dioica could change the characteristics of egg and could meet the preferences of consumers for the intense color of the yolk. [less ▲]

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See detailDépression, niveau d'engagement dans des activités et processus psychologiques : Nouvel axe de lecture et nouveaux outils d'évaluation
Wagener, Aurélie ULg

Conference (2014, October 17)

Cet atelier aura pour objectif de présenter un modèle théorique, testé auprès de 500 personnes, des liens entre la dépression, le niveau d’engagement dans des activités et différentes familles de ... [more ▼]

Cet atelier aura pour objectif de présenter un modèle théorique, testé auprès de 500 personnes, des liens entre la dépression, le niveau d’engagement dans des activités et différentes familles de processus psychologiques (image de soi, pensées négatives répétitives, évitement expérientiel, satisfaction environnementale, régulation émotionnelle et tendance à l’approche). Plus précisément, nous menons actuellement une étude dont les résultats nous permettront d’identifier les processus psychologiques médiateurs de la relation entre la dépression et le niveau d’engagement dans des activités. Ces processus psychologiques médiateurs pourront donc devenir des cibles précises et identifiées du traitement psychothérapeutique. Pour mener à bien cette étude, nous avons réalisé une revue de la littérature des outils évaluant spécifiquement ces processus psychologiques. Certains questionnaires ont été traduits de l’Anglais au Français et sont en cours de validation. L’ensemble des échelles utilisées, leur utilité et leur cotation, seront présentées lors de l’atelier. Elles seront également mises à disposition des cliniciens intéressés. Une discussion concernant les patients avec lesquels les utiliser sera également proposée. [less ▲]

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See detailCroire ou douter : comment en sortir ? Regards et pratiques croisés pour penser la maltraitance
Glowacz, Fabienne ULg

Conference given outside the academic context (2014)

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See detailRéflexions sur les outils d'évaluation de la phonologie et de la morphosyntaxe dans le diagnostic de dysphasie
Devault, Cecilia; Labbé, Amandine; Leclercq, Anne-Lise ULg

Scientific conference (2014, October 17)

Detailed reference viewed: 13 (2 ULg)