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See detailAppropriation progressive de l'arganeraie: exploration de l'histoire depuis la genèse des droits jusqu'à leur refonte
Bejbouji, Jihane ULg; Mougenot, Catherine ULg; Mormont, Marc ULg et al

in Farcy, Christine; Peyron, Jean-Luc; Poss, Yves (Eds.) Forêts et Foresterie. Mutations et décloisonnements (2013)

L’arganeraie, spécificité du Sud-Ouest marocain, est l’ensemble des écosystèmes dont l’espèce caractéristique est l’arganier ou Argania spinosa. Outre leurs multiples fonctions écologiques, ces ... [more ▼]

L’arganeraie, spécificité du Sud-Ouest marocain, est l’ensemble des écosystèmes dont l’espèce caractéristique est l’arganier ou Argania spinosa. Outre leurs multiples fonctions écologiques, ces écosystèmes procurent de nombreux biens pour une population pauvre vivant dans des conditions précaires. Toutefois, cet espace intrigue. En effet, à la différence des autres forêts marocaines dont les riverains ne disposent que de deux droits (la récolte de bois mort gisant et le parcours), la population de l’arganeraie a bénéficié d’une législation spéciale depuis 1925, jouissant ainsi d’une large gamme d’utilisation et d’exploitation des ressources forestières. L’image classique véhiculée de cet espace est celle d’une population autochtone, connue pour son élevage caprin, poursuivant des pratiques ancestrales, notamment l’agdal, et gérant des terrains d’arganiers dont elle tire depuis toujours une huile, aujourd’hui très prisée à l’échelle internationale, et devenue emblématique du Maroc. Les historiens nous livrent pourtant une image contrastée entre recherche de la sécurité et de terrains fertiles et fuite de l’insécurité. Parmi les différentes étapes qui ont jalonné son histoire, nous distinguons pour notre propos deux étapes principales : une première période se situe avant la délimitation des forêts et est marquée par des vagues d’immigration successives venant du sud ; la seconde, à la suite de la colonisation, a remodelé et déstabilisé la situation foncière traditionnelle dans la zone en délimitant un espace domanial. Dans cet article, nous dressons le portrait actuel de l’espace et l’ensemble des droits qui le régissent. Cette construction sociale résulte d’une histoire riche et tourmentée, ayant affecté les modes de gestion des territoires. Pour ce faire, nous avons mobilisé des données d’historiens et d’enquêtes qualitatives et quantitatives réalisées dans le cadre de ce travail ; ces dernières se sont déroulées auprès de 100 ménages, principalement au niveau de trois communes rurales autour du massif du Jbel Amsitten. Il constitue l’une des dix-huit zones centrales de la Réserve de Biosphère de l’arganier, dans le Sud-Ouest marocain. Etant donné que les enquêtes s’intéressent aux usages et pratiques des ménages enquêtés, mais aussi de leurs aïeuls et ascendants, ce travail de recherche pourrait contribuer à reconstruire l’histoire de la zone à partir de celle des personnes interviewées via la compréhension de leur implantation spatiale ou temporelle. Nos enquêtes nous montrent que la population est issue d’un brassage récent d’émigrants du sud. Il s’en suit une trame de droits récemment forgée ; le domanial étant bien distinct du privé avec un rétrécissement des droits concédés par les Français. Renouer avec le corpus de règles qu’entretenait la population avec cet espace-ressources, pourrait être à notre avis, une des principales portes d’entrées à leur conservation. [less ▲]

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See detailL’appropriazione dello spazio urbano : le processioni
Delfosse, Annick ULg

Scientific conference (2009, March 02)

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See detailApproprions les études universitaires à notre temps
Dubuisson, Marcel ULg

Speech/Talk (1961)

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See detailApprossimazioni all'«alieno»
Curreri, Luciano ULg

in L'alieno dentro : Percorso semiotico alle origini del romanzo femminista italiano (2011)

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See detailL'approvisionnement agricole de la ville de Niamey : potentialités et contraintes d'une agriculture de proximité
Andres, Ludovic ULg; Lebailly, Philippe ULg

Conference (2012, June 12)

Cet article tente de répondre à la question suivante : « Est-ce que l’agriculture urbaine et périurbaine de Niamey peut satisfaire et approvisionner une demande urbaine toujours plus croissante ? ». Cette ... [more ▼]

Cet article tente de répondre à la question suivante : « Est-ce que l’agriculture urbaine et périurbaine de Niamey peut satisfaire et approvisionner une demande urbaine toujours plus croissante ? ». Cette question de recherche est accompagnée d’un objectif secondaire essayant de démontrer l’importance de la diversité des systèmes de production permettant le développement de nombreuses cultures. Cette étude a été réalisée à partir de données secondaires provenant du Recensement Général de l’Agriculture et du Cheptel (RGAC), de l’Institut National de la Statistique (INS) et de la Direction Générale de la Statistique Agricole (DGSA). Après une présentation de la zone d’étude, les différents systèmes de production présents au sein de Niamey seront décrits et caractérisés. Les systèmes de production se regroupent au sein de deux catégories : agriculture pluviale et agriculture irriguée (riziculture irriguée ; maraîchage, arboriculture fruitière et riziculture pluviale et/ou irriguée ; maraîchage et arboriculture fruitière) (Seybou Y et Wada H, 2004). De plus, la production et les superficies agricoles de chaque spéculation seront introduites. L’importance de la consommation alimentaire telle que celle des légumes (31,5 kg/personne/an) et des céréales (179,6 kg/personne/an) sera présentée afin d’établir une balance entre la production locale et les besoins alimentaires des ménages de la Communauté Urbaine de Niamey (CUN) (République du Niger, 1994). Les potentialités de cette agriculture sont accentuées par la faible capacité de stockage et la détérioration lors du transport des produits agricoles provenant des zones rurales. Il en ressort que malgré les fortes potentialités de cette agriculture de proximité (urbaine, périurbaine et rurbaine), certaines contraintes telles que la problématique foncière, l’accès aux intrants et aux matériels agricoles (motopompes) empêchent l’expansion de ces systèmes de production. De plus, les balances alimentaires présentées indiquent un déficit pour la quasi-totalité des rubriques alimentaires entraînant de ce fait un accroissement du coût des produits importés. Toutefois, les systèmes de production pourraient partiellement combler une demande alimentaire de la population en constante augmentation. [less ▲]

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See detailApprovisionnement alimentaire de la ville de Bukavu : flux en provenance de l'intérieur du Sud-Kivu, du Rwanda et du Nord-Kivu
Vwima Ngezirabona, Stany ULg; Lebailly, Philippe ULg

Poster (2013)

Ce travail caractérise les flux principaux d’approvisionnements alimentaires de la ville de Bukavu en provenance de l’intérieur de la province du Sud-Kivu, du Nord-Kivu et du Rwanda issus du pointage des ... [more ▼]

Ce travail caractérise les flux principaux d’approvisionnements alimentaires de la ville de Bukavu en provenance de l’intérieur de la province du Sud-Kivu, du Nord-Kivu et du Rwanda issus du pointage des flux des produits alimentaires. [less ▲]

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See detailL'approvisionnement en circuit court: gage de qualité et durabilité?
Sindic, Marianne ULg

Conference given outside the academic context (2013)

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See detailL'approvisionnement en eau des porcs: un élément à ne pas négliger
Vandenheede, Marc ULg; Nicks, Baudouin ULg

in Annales de Médecine Vétérinaire (1991), 135(2), 123-128

Water requirements are determined according to the amounts of water stored in the tissues and lost by the animal. This review summarises estimates of water losses by faeces, urine, milk and by evaporation ... [more ▼]

Water requirements are determined according to the amounts of water stored in the tissues and lost by the animal. This review summarises estimates of water losses by faeces, urine, milk and by evaporation from the skin and respiratory tract. A description of the main pig drinkers is given with recommendations about the number, siting, fixing height and flow rate. Drinking water quality guidelines are also given. [less ▲]

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See detailApproximate and Efficient Methods to Assess Error Fields in Spatial Gridding with Data Interpolating Variational Analysis (DIVA)
Beckers, Jean-Marie ULg; Barth, Alexander ULg; Troupin, Charles ULg et al

in Journal of Atmospheric & Oceanic Technology (2014), 31(2), 515-530

We present new approximate methods to provide error fields for the spatial analysis tool Diva. It is first shown how to replace the costly analysis of a large number of covariance functions by a single ... [more ▼]

We present new approximate methods to provide error fields for the spatial analysis tool Diva. It is first shown how to replace the costly analysis of a large number of covariance functions by a single analysis for quick error computations. Then another method is presented where the error is only calculated in a small number of locations and from there the spatial error field itself interpolated by the analysis tool. The efficiency of the methods is illustrated on simple schematic test cases and a real application in the Mediterranean Sea. These examples show that with these methods one has the possibility for quick masking of regions void of sufficient data and the production of "exact" error fields at reasonable cost. The error-calculation methods can also be generalized for use with other analysis methods such as 3D-Var and are therefore potentially interesting for other implementations. [less ▲]

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See detailApproximate compositional values and tissue fatty acid profiles of Nile Tilapia (Oreachromis niloticus L.) fed azolla-diets in earthen ponds
Abou, Youssouf; Fiogbé, Emile Didier; Beckers, Yves ULg et al

in Food and Nutrition Sciences (2011), 2

The approximate general composition and the fatty acid profile of Nile tilapia fed Azolla-diets in ponds were studied for 90 days. Six isonitrogenous (29.2% CP) and isoenergetic (16.9 kJ·g−1) diets were ... [more ▼]

The approximate general composition and the fatty acid profile of Nile tilapia fed Azolla-diets in ponds were studied for 90 days. Six isonitrogenous (29.2% CP) and isoenergetic (16.9 kJ·g−1) diets were formulated to contain 0% (A0), 10% (A10), 20% (A20), 30% (A30), 40% (A40) and 50% (A50) of Azolla meal (AM), as partial fish meal (FM) substitutes. Diet A0 without AM served as a control. Fish growth decreased as AM level exceeded 20% in diets (P < 0.05). Dry matter and crude protein showed no significant differences (P > 0.05). Crude lipid was significantly lower in fish fed A50 and significant differences were also found in crude ash (P < 0.05). Linolenic acid (LLA) decreased significantly when AM level in diets increased (P < 0.05). In contrast, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahex- aenoic acid (DHA) showed significantly higher values in fish fed high AM (P < 0.05). The n − 3/n − 6 ratio ranged from 0.35 to 0.49, with values being significantly higher in fish fed A20, A30 and A50. High level of the fern reduces growth without negatively affecting fatty acid in fish. Fish PUFA, especially the (n − 3) fatty acids, are affected posi- tively, even when fed 50% AM, which is good for the quality of the fish produced in regard to the benefits for the health of consumers. [less ▲]

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See detailApproximate Conditions Replacing Thin Layers
Poignard, Clair; Dular, Patrick ULg; Perrussel, Roman et al

in IEEE Transactions on Magnetics (2008), 44(6), 1154-1157

We provide a rigorous asymptotic method to build approximate conditions equivalent to a thin layer. With these conditions the electromagnetic field may be computed in domains such as a biological cell ... [more ▼]

We provide a rigorous asymptotic method to build approximate conditions equivalent to a thin layer. With these conditions the electromagnetic field may be computed in domains such as a biological cell, without meshing the membrane. The influence of the membrane is replaced by an appropriate condition on the inner domain, while in the thin layer, the approximate field is explicitly known. We give error estimates, which validate our asymptotic method, and we present a few numerical results performed with the finite-element method. [less ▲]

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See detailApproximate dynamic programming with a fuzzy parameterization
Busoniu, Lucian; Ernst, Damien ULg; De Schutter, Bart et al

in Automatica (2010), 46(5), 804-814

Dynamic programming (DP) is a powerful paradigm for general, nonlinear optimal control. Computing exact DP solutions is in general only possible when the process states and the control actions take values ... [more ▼]

Dynamic programming (DP) is a powerful paradigm for general, nonlinear optimal control. Computing exact DP solutions is in general only possible when the process states and the control actions take values in a small discrete set. In practice, it is necessary to approximate the solutions. Therefore, we propose an algorithm for approximate DP that relies on a fuzzy partition of the state space, and on a discretization of the action space. This fuzzy Q-iteration algorithm works for deterministic processes, under the discounted return criterion. We prove that fuzzy Q-iteration asymptotically converges to a solution that lies within a bound of the optimal solution. A bound on the suboptimality of the solution obtained in a finite number of iterations is also derived. Under continuity assumptions on the dynamics and on the reward function, we show that fuzzy Q-iteration is consistent, i.e., that it asymptotically obtains the optimal solution as the approximation accuracy increases. These properties hold both when the parameters of the approximator are updated in a synchronous fashion, and when they are updated asynchronously. The asynchronous algorithm is proven to converge at least as fast as the synchronous one. The performance of fuzzy Q-iteration is illustrated in a two-link manipulator control problem. [less ▲]

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See detailApproximate Numerical Continuation for Aeroelastic Systems Undergoing Aperiodic Limit Cycle Oscillations
Dimitriadis, Grigorios ULg

in Proceedings of the 2007 International Forum on Aeroelasticity and Structural Dynamics (2007, June)

This paper presents a modified numerical continuation approach for predicting the bifurcation behaviour of aeroelastic systems undergoing aperiodic limit cycles oscillations. Such oscillations can occur ... [more ▼]

This paper presents a modified numerical continuation approach for predicting the bifurcation behaviour of aeroelastic systems undergoing aperiodic limit cycles oscillations. Such oscillations can occur due to a number of nonlinear functions. Here, backlash nonlinearity in the aileron stiffness for a Generic Transport Aircraft is considered. It is shown that classical numerical continuation will fail due to the aperiodic nature of the limit cycles and the inability to perform period scaling and phase fixing. An alternative, approximate numerical continuation method is proposed, based on longer numerical integration sequences and a heuristic method for determining the period of the limit cycle oscillations. The approach is applied successfully to a simulated aeroelastic model of the Generic Transport Aircraft with backlash. [less ▲]

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See detailApproximate Policy Iteration for Closed-Loop Learning of Visual Tasks
Jodogne, Sébastien ULg; Briquet, Cyril ULg; Piater, Justus ULg

in Lecture Notes in Computer Science (2006, September), 4212

Approximate Policy Iteration (API) is a reinforcement learning paradigm that is able to solve high- dimensional, continuous control problems. We propose to exploit API for the closed-loop learning of ... [more ▼]

Approximate Policy Iteration (API) is a reinforcement learning paradigm that is able to solve high- dimensional, continuous control problems. We propose to exploit API for the closed-loop learning of mappings from images to actions. This approach requires a family of function approximators that maps visual percepts to a real-valued function. For this purpose, we use Regression Extra-Trees, a fast, yet accurate and versatile machine learning algorithm. The inputs of the Extra-Trees consist of a set of visual features that digest the informative patterns in the visual signal. We also show how to parallelize the Extra-Tree learning process to further reduce the computational expense, which is often essential in visual tasks. Experimental results on real-world images are given that indicate that the combination of API with Extra-Trees is a promising framework for the interactive learning of visual tasks. [less ▲]

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See detailApproximate reinforcement learning: an overview
Busoniu, Lucian; Babuska, Robert; De Schutter, Bart et al

in Proceedings of the 2011 IEEE International Symposium on Adaptive Dynamic Programming and Reinforcement Learning (ADPRL-11) (2011, April)

Reinforcement learning (RL) allows agents to learn how to optimally interact with complex environments. Fueled by recent advances in approximation-based algorithms, RL has obtained impressive successes in ... [more ▼]

Reinforcement learning (RL) allows agents to learn how to optimally interact with complex environments. Fueled by recent advances in approximation-based algorithms, RL has obtained impressive successes in robotics, artificial intelligence, control, operations research, etc. However, the scarcity of survey papers about approximate RL makes it difficult for newcomers to grasp this intricate field. With the present overview, we take a step toward alleviating this situation. We review methods for approximate RL, starting from their dynamic programming roots and organizing them into three major classes: approximate value iteration, policy iteration, and policy search. Each class is subdivided into representative categories, highlighting among others offline and online algorithms, policy gradient methods, and simulation-based techniques. We also compare the different categories of methods, and outline possible ways to enhance the reviewed algorithms. [less ▲]

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See detailApproximate value iteration in the reinforcement learning context. Application to electrical power system control
Ernst, Damien ULg; Glavic, Mevludin; Geurts, Pierre ULg et al

in International Journal of Emerging Electrical Power Systems (2005), 3(1),

In this paper we explain how to design intelligent agents able to process the information acquired from interaction with a system to learn a good control policy and show how the methodology can be applied ... [more ▼]

In this paper we explain how to design intelligent agents able to process the information acquired from interaction with a system to learn a good control policy and show how the methodology can be applied to control some devices aimed to damp electrical power oscillations. The control problem is formalized as a discrete-time optimal control problem and the information acquired from interaction with the system is a set of samples, where each sample is composed of four elements: a state, the action taken while being in this state, the instantaneous reward observed and the successor state of the system. To process this information we consider reinforcement learning algorithms that determine an approximation of the so-called Q-function by mimicking the behavior of the value iteration algorithm. Simulations are first carried on a benchmark power system modeled with two state variables. Then we present a more complex case study on a four-machine power system where the reinforcement learning algorithm controls a Thyristor Controlled Series Capacitor (TCSC) aimed to damp power system oscillations. [less ▲]

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See detailApproximating Functions on a Mesh with Restricted Voronoï Diagrams
Nivoliers, Vincent ULg; Lévy, Bruno

in Computer Graphics Forum (2013), 32(5), 83-92

We propose a method that computes a piecewise constant approximation of a function defined on a mesh. The approximation is associated with the cells of a restricted Voronoï diagram. Our method optimizes ... [more ▼]

We propose a method that computes a piecewise constant approximation of a function defined on a mesh. The approximation is associated with the cells of a restricted Voronoï diagram. Our method optimizes an objective function measuring the quality of the approximation. This objective function depends on the placement of the samples that define the restricted Voronoï diagram and their associated function values. We study the continuity of the objective function, derive the closed-form expression of its derivatives and use them to design a numerical solution mechanism. The method can be applied to a function that has discontinuities, and the result aligns the boundaries of the Voronoï cells with the discontinuities. Some examples are shown, suggesting potential applications in image vectorization and compact representation of lighting. [less ▲]

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See detailApproximation Algorithms for Multi-Dimensional Vector Assignment Problems
Dokka, Trivikram; Crama, Yves ULg; Spieksma, Frits C.R.

E-print/Working paper (2013)

We consider a special class of axial multi-dimensional assignment problems called multi-dimensional vector assignment (MVA) problems. An instance of the MVA problem is defined by $m$ disjoint sets, each ... [more ▼]

We consider a special class of axial multi-dimensional assignment problems called multi-dimensional vector assignment (MVA) problems. An instance of the MVA problem is defined by $m$ disjoint sets, each of which contains the same number $n$ of $p$-dimensional vectors with nonnegative integral components, and a cost function defined on vectors. The cost of an $m$-tuple of vectors is defined as the cost of their component-wise maximum. The problem is now to partition the $m$ sets of vectors into $n$ $m$-tuples so that no two vectors from the same set are in the same $m$-tuple and so that the total cost of the $m$-tuples is minimized. The main motivation comes from a yield optimization problem in semi-conductor manufacturing. We consider two classes of polynomial-time heuristics for MVA, namely, hub heuristics and sequential heuristics, and we study their approximation ratio. In particular, we show that when the cost function is monotone and subadditive, hub heuristics, as well as sequential heuristics, have finite approximation ratio for every fixed $m$. Moreover, we establish better approximation ratios for certain variants of hub heuristics and sequential heuristics when the cost function is monotone and submodular, or when it is additive. We provide examples to illustrate the tightness of our analysis. Furthermore, we show that the MVA problem is APX-hard even for the case $m=3$ and for binary input vectors. Finally, we show that the problem can be solved in polynomial time in the special case of binary vectors with fixed dimension $p$. [less ▲]

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See detailApproximation algorithms for multi-dimensional vector assignment problems
Crama, Yves ULg

Conference (2014, July 09)

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See detailApproximation Algorithms for Multi-Dimensional Vector Assignment Problems
Crama, Yves ULg

Conference (2013, July 04)

Detailed reference viewed: 12 (0 ULg)