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See detailEnjeux de « Horizon 2020 » : Conséquences pour les chercheurs
Thirion, Paul ULg

Scientific conference (2014, October 24)

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See detailRetrievals of formaldehyde from ground-based FTIR and MAX-DOAS observations at the Jungfraujoch station and comparisons with GEOS-Chem and IMAGES model simulations
Franco, Bruno ULg; Hendrick, François; Van Roozendael, Michel et al

in Atmospheric Measurement Techniques. Papers in Open Discussion (2014), 7

As a ubiquitous product of the oxidation of many Volatile Organic Compounds (VOCs), formaldehyde (HCHO) plays a key role as a short-lived and reactive intermediate in the atmospheric photo-oxidation ... [more ▼]

As a ubiquitous product of the oxidation of many Volatile Organic Compounds (VOCs), formaldehyde (HCHO) plays a key role as a short-lived and reactive intermediate in the atmospheric photo-oxidation pathways leading to the formation of tropospheric ozone and secondary organic aerosols. In this study, HCHO profiles have been successfully retrieved from ground-based Fourier Transform Infrared (FTIR) solar spectra and UV-Visible Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) scans recorded during the July 2010–December 2012 time period at the Jungfraujoch station (Swiss Alps, 46.5 N, 8.0 E, 3580ma.s.l.). Analysis of the retrieved products has revealed different vertical sensitivity between both remote sensing techniques. Furthermore, HCHO amounts simulated by two state-of-the-art Chemical Transport Models (CTMs), GEOS-Chem and IMAGESv2, have been compared to FTIR total columns and MAX-DOAS 3.6–8 km partial columns, accounting for the respective vertical resolution of each ground-based instrument. Using the CTMs outputs as intermediate, FTIR and MAX-DOAS retrievals have shown consistent seasonal modulations of HCHO throughout the investigated period, characterized by summertime maximum and wintertime minimum. Such comparisons have also highlighted that FTIR and MAX-DOAS provide complementary products for the HCHO retrieval above the Jungfraujoch station. [less ▲]

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See detailReformage catalytique du toluène
Claude, Vincent ULg; Lambert, Stéphanie ULg; Courson, Claire

Poster (2014, October 23)

This poster summarizes results obtained for the catalytic reforming of tar in the oultlet gas of a biomass gasifier. All samples were synthesized with aluminum nitrate and an organosilane (EDAS) in order ... [more ▼]

This poster summarizes results obtained for the catalytic reforming of tar in the oultlet gas of a biomass gasifier. All samples were synthesized with aluminum nitrate and an organosilane (EDAS) in order to enhance the metallic dispersion and surface area. Three different compositions have been studied (Al2O3-SiO2; Al2O3-SiO2+2%wt Ni; Al2O3-SiO2+10%wt Fe). The catalytic tests highlight the fact that the sample containing 2%Ni wt is the more appropriate in our conditions. [less ▲]

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See detailMontage de projets de Recherche et d’Innovation : A la recherche de financements
Hiligsmann, Serge ULg

Scientific conference (2014, October 23)

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See detailDebatte über Kollaboration. Tristes Spektakel
Brüll, Christoph ULg

Article for general public (2014)

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See detailManaging understory light to maintain the coexistence of forest tree species with different shade tolerances
Ligot, Gauthier ULg

Doctoral thesis (2014)

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices ... [more ▼]

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices aim to favor natural processes over human interventions. Particularly, continuous-cover forestry has the goal of relying on natural regeneration, and maintaining irregular stand structure and tree species mixture. However, maintaining mixture of species with different shade tolerances appears arduous with such a silvicultural system. Successfully managing irregular and mixed forests, relying on natural processes, requires a strong knowledge of the ecology of natural regeneration. In particular, strong knowledge is required to predict the result of the interspecific competition in the understory depending upon light availability. The amount of radiation transmitted to the understory is indeed a critical factor determining regeneration dynamics. It determines, at least in part, regeneration composition because of interspecific differences of growth and survival under shade. Moreover, our quantitative understanding of understory light in uneven-aged and mixed stands remains incomplete. A better quantitative understanding of understory light is needed to provide quantitative guidelines for the management of understory light in uneven-aged and mixed stands and, hence, for the management of natural regeneration. The purpose of this thesis is to determine how close-to-nature forest management can maintain mixtures of species with contrasting shade tolerances. I consider ecological conditions with good water and nutrient supplies. In these conditions, partially closed canopy limits the amount of light that reaches the understory, and light is the major factor driving regeneration composition. Consequently, I study the dynamics of natural regeneration with regards to light availability as well as the interception of light by the canopy of heterogeneous stands. Studying the regeneration ecology of two species with contrasting shade tolerances (Fagus sylvatica L. and Quercus petraea (Matt.) Liebl.), I find that the shade-tolerant species outgrow the less shade-tolerant species in all light conditions. Even though the control of understory light with continuous-cover silviculture is required to sustain the growth of less shade-tolerant regenerations, it might not be sufficient to maintain the coexistence of species with contrasting shade tolerances. In order to examine the effects of canopy structure and composition on understory light availability, I use a model of light interception by heterogeneous canopies after synthesizing and discussing the approaches reported in the literature. The model predicts satisfactorily measures of transmitted light even though it is a relatively simple radiative transfer model. I next explore how various silvicultural treatments can be manipulated to provide favorable understory light conditions for natural regeneration. These silvicultural strategies correspond to selective thinnings of five different types, e.g., harvesting preferentially small trees, large trees, or trees of shade-tolerant species or creating circular gaps. The results underline that creating favorable understory light conditions for natural regeneration can be achieved with various regeneration treatments. However, the adequate reduction of stand density depends upon the chosen silvicultural strategies. In particular, creating gaps of about 500 m2 provides adequate light for small regeneration clumps. Harvesting preferentially small and trees of shade-tolerant species are also appropriate but required higher harvest intensity. Harvesting preferentially large trees slightly increases understory light and promotes more shade-tolerant species than less shade-tolerant species. In order to maintain the coexistence of species with contrasting shade tolerances, forest manager must control understory light and manually suppress the regeneration of the shade-tolerant species. The outcome of this study provides foresters with the necessary tools to evaluate how silvicultural treatments can be manipulated to create or maintain favorable light conditions for the regeneration of species of different shade tolerances. Guidelines are additionally proposed for forest managers wanting to maintain the coexistence of species with contrasting shade tolerances. [less ▲]

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See detailRegularity of functions: Genericity and multifractal analysis
Esser, Céline ULg

Doctoral thesis (2014)

As surprising as it may seem, there exist functions of C∞(R) which are nowhere analytic. When such an unexpected object is found, a natural question is to ask whether many similar ones may exist. A ... [more ▼]

As surprising as it may seem, there exist functions of C∞(R) which are nowhere analytic. When such an unexpected object is found, a natural question is to ask whether many similar ones may exist. A classical technique is to use the Baire category theorem and the notion of residuality. This notion is purely topological and does not give any information about the measure of the set of objects satisfying such a property. In this purpose, the notion of prevalence has been introduced. Moreover, one could also wonder whether large algebraic structures of such objects can be constructed. This question is formalized by the notion of lineability. The first objective of the thesis is to go further into the study of nowhere analytic functions. It is known that the set of nowhere analytic functions is residual and lineable in C∞([0, 1]). We prove that the set of nowhere analytic functions is also prevalent in C∞([0, 1]). Those results of genericity are then generalized using Gevrey classes, which can be seen as intermediate between the space of analytic functions and the space of infinitely differentiable functions. We also study how far such results of genericity could be extended to spaces of ultradifferentiable functions, defined using weight sequences or using weight functions. The second main objective is to study the pointwise regularity of functions via their multifractal spectrum. Computing the multifractal spectrum of a function using directly its definition is an unattainable goal in most of the practical cases, but there exist heuristic methods, called multifractal formalisms, which allow to estimate this spectrum and which give satisfactory results in many situations. The Frisch-Parisi conjecture, classically used and based on Besov spaces, presents two disadvantages: it can only hold for spectra that are concave and it can only yield the increasing part of spectra. Concerning the first problem, the use of Snu spaces allows to deal with non-concave increasing spectra. Concerning the second problem, a generalization of the Frisch-Parisi conjecture obtained by replacing the role played by wavelet coefficients by wavelet leaders allows to recover the decreasing part of concave spectra. Our purpose in this thesis is to combine both approaches and define a new formalism derived from large deviations based on statistics of wavelet leaders. As expected, we show that this method yields non-concave spectra and is not limited to their increasing part. From the theoretical point of view, we prove that this formalism is more efficient than the previous wavelet-based multifractal formalisms. We present the underlying function space and endow it with a topology. [less ▲]

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See detailUn savoir enfermé est un savoir stérile : Subir ou agir ?
Rentier, Bernard ULg; Thirion, Paul ULg

Scientific conference (2014, October 22)

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See detailCombined holography and thermography in a single sensor through image-plane holography at thermal infrared wavelengths
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Optics Express (2014), 22(21), 25517-25529

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and ... [more ▼]

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and surface shape information about objects. This is due to the fact that the holograms are affected by the thermal background emitted by objects at room temperature. We explain the setup and the processing of data which allows decoupling the two types of information. This natural data fusion can be advantageously used in a variety of nondestructive testing applications. [less ▲]

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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 detailHow to survey your hippos night and day? Follow them in bed with drones!
Linchant, Julie ULg; Lejeune, Philippe ULg; Vermeulen, Cédric ULg

Scientific conference (2014, October 20)

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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 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 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 detailEU Patent Package - The University Perspective
Antheunis, Nicole ULg

Conference given outside the academic context (2014)

What are the key issues of concern for European Universities with regards to the Unitary Patent and the Unified Patent Court

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