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Peer Reviewed
See detailOptimal extraction of multiple overlapping spectra: a new algorithm based on the maximum entropy method
Khmil, S. V.; Surdej, Jean ULg

in Kinematika i Fizika Nebesnykh Tel Supplement (2000), 3

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of the same quasar) has been developed, assuming that the point-spread function (PSF) of the ... [more ▼]

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of the same quasar) has been developed, assuming that the point-spread function (PSF) of the measuring instrument and the positions of the spectra relative to the CCD frame are unknown. The main idea of the algorithm is to successively apply the maximum entropy method to each set of parameters, such as the spectra, the PSF, and the spectra positions, in order to iteratively improve their values. The algorithm uses all the a priori knowledge about the spectra (e.g. flux positivity, relative magnitudes between the components, astrometry, etc.) to compute the initial parameter sets. After careful testing, the algorithm was applied to extract the spectra of the gravitationally lensed system Q1009-0252 A & B (I[SUB]B[/SUB]/I[SUB]A[/SUB]=0.1, θ[SUB]AB[/SUB]=1.''55, 1{pxl}=0.''44, typical seeing FWHM=0.''8). [less ▲]

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See detailOptimal Fertility along the Lifecycle
Pestieau, Pierre ULg; Ponthiere, Grégory ULg

in Economic Theory (2013)

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See detailOptimal Foraging By Hoverflies (Diptera, Syrphidae) And Ladybirds (Coleoptera, Coccinellidae) - Mechanisms
Hemptinne, Jl.; Dixon, Afg.; Doucet, Jean-Louis ULg et al

in European Journal of Entomology (1993), 90(4), 451-455

Coccinellids and syrphids that feed on aphids and coccids face the same problem: an unstable food supply. Their eggs and larvae face cannibalism and/or starvation if the aphid colony they attack declines ... [more ▼]

Coccinellids and syrphids that feed on aphids and coccids face the same problem: an unstable food supply. Their eggs and larvae face cannibalism and/or starvation if the aphid colony they attack declines in abundance before they mature. Optimal foraging theory predicts that such predators should lay a few eggs early in the development of an aphid colony. Studies on two species of coccinellid and one species of syrphid revealed that they do respond to the quality as well as the abundance of their prey. By refraining from laying eggs in aphid colonies already exploited by predators and those that are shortly to decline in abundance when the aphids disperse, these predators are able to forage in a way that is consistent with the predictions of optimal foraging theory. [less ▲]

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See detailThe Optimal Gravitational Lens Telescope
Surdej, Jean ULg; Delacroix, Christian ULg; Coleman, P. et al

in Astronomical Journal (The) (2010), 139

Given an observed gravitational lens mirage produced by a foreground deflector (cf. galaxy, quasar, cluster, . . . ), it is possible via numerical lens inversion to retrieve the real source image, taking ... [more ▼]

Given an observed gravitational lens mirage produced by a foreground deflector (cf. galaxy, quasar, cluster, . . . ), it is possible via numerical lens inversion to retrieve the real source image, taking full advantage of the magnifying power of the cosmic lens. This has been achieved in the past for several remarkable gravitational lens systems. Instead, we propose here to invert an observed multiply imaged source directly at the telescope using an ad-hoc optical instrument which is described in the present paper. Compared to the previous method, this should allow one to detect fainter source features as well as to use such an optimal gravitational lens telescope to explore even fainter objects located behind and near the lens. Laboratory and numerical experiments illustrate this new approach. [less ▲]

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See detailOptimal heating control in a passive solar commercial building
Kummert, M.; Andre, Philippe ULg; Nicolas, Jacques ULg

in Proceedings EuroSun'2000 Congress (2000, June)

A smart heating controller has a twofold objective: to save as much energy as possible while maintaining an acceptable comfort level in the building. Due to very large time constants in the building ... [more ▼]

A smart heating controller has a twofold objective: to save as much energy as possible while maintaining an acceptable comfort level in the building. Due to very large time constants in the building response, it has to anticipate internal and external disturbances. In the case of a passive solar commercial building, the need for anticipation is reinforced by important solar and internal gains. Indeed, large solar gains increase the energy savings potential but also the overheating risk. Optimal control theory presents an ideal formalism to solve this problem : its principle is to anticipate the building behaviour using a model and a forecasting of the disturbances in order to compute the control sequence that minimises a given cost function over the optimisation horizon. This cost function can combine comfort level and energy consumption. This paper presents the application of optimal control to auxiliary heating of a passive solar commercial building. Simulation-based and experimental results show that it can lead to significant energy savings while maintaining or improving the comfort level in this type of building. [less ▲]

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See detailOptimal heating control in a passive solar commercial building.
Kummert, Michaël; Andre, Philippe ULg; Nicolas, Jacques ULg

in Solar Energy (2001), 69(6), 103-116

A smart heating controller has a twofold objective: to save as much energy as possible while maintaining an acceptable comfort level in the building. Due to very large time constants in the building ... [more ▼]

A smart heating controller has a twofold objective: to save as much energy as possible while maintaining an acceptable comfort level in the building. Due to very large time constants in the building response, it has to anticipate internal and external disturbances. In the case of a passive solar commercial building, the need for anticipation is reinforced by important solar and internal gains. Indeed, large solar gains increase the energy savings potential but also the overheating risk. Optimal control theory presents an ideal formalism to solve this problem: its principle is to anticipate the building behaviour using a model and a forecasting of the disturbances in order to compute the control sequence that minimises a given cost function over the optimisation horizon. This cost function can combine comfort level and energy consumption. This paper presents the application of optimal control to auxiliary heating of a passive solar commercial building. Simulation-based and experimental results show that it can lead to significant energy savings while maintaining or improving the comfort level in this type of building [less ▲]

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See detailOptimal income taxation and the ability distribution: Implications for migration equilibria
Hamilton, J.; Pestieau, Pierre ULg

in International Tax and Public Finance (2005), 12(1), 29-45

As recently argued by Diamond (1998), one of the key factors explaining the progressivity of an optimal non-linear income tax is the distribution of productivity among workers. Migration is one source of ... [more ▼]

As recently argued by Diamond (1998), one of the key factors explaining the progressivity of an optimal non-linear income tax is the distribution of productivity among workers. Migration is one source of changes in the productivity distribution. How changes in the population's ability distribution affect optimal income tax schedules has received little attention. Changing the distribution generally affects both the objective function and the government budget constraint. We first consider the comparative statics of the fraction of highly-skilled workers with maximin and maximax welfare functions (so that only the second effect is present) and a quasi-linear utility function. We also present some results for a utilitarian social welfare function. We then study the interaction between mobility and redistributive taxation. We consider mobility by either the skilled or unskilled population under majority voting where governments take the population as fixed. If individuals choose to relocate independently, having identical ability distributions is always a stable equilibrium when the unskilled are the mobile group. However, this is not always the case when the skilled are mobile. If groups of individuals can choose where to locate, having identical ability distributions across regions is only an equilibrium when the mobile type has an overall majority. [less ▲]

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See detailOPTIMAL LEVEL OF RAPESEED MEAL IN DIETS OF LAMBS.
Mandiki, S.; Bister, J.-L.; Deryke, G. et al

Poster (1999)

Two experiments were carried out in order to improve the strategy of rapeseed meal (RPM) incorporation in the diets of lambs. In a first experiment, the effects of RPM obtained from either a high ... [more ▼]

Two experiments were carried out in order to improve the strategy of rapeseed meal (RPM) incorporation in the diets of lambs. In a first experiment, the effects of RPM obtained from either a high-glucosinolate (HG) cultivar (Honk RPM) or a double-low strain (Samourai RPM) were studied. Two types of concentrates containing 25% of RPM were compared to a Control concentrate. In a second experiment, the effects of various proportions (0 – 40%) of an industrial low glucosinolate (LG)-RPM were studied in order to determine the disorder-threshold in diets for young ruminants. One hundred forty six Texel, Suffolk or crossbred lambs ranged in age from 1 to 2 months were used. Neither the Samourai nor the Honk RPM did affect negatively animal performance whatever the parameter considered (growth, food intake and conversion, slaughter performances). Low (P < 0.05) proportions of C10:0, C12:0 and C14:0 and high contents of C18:1trans, C22:2 were determined in the perirenal fat of lambs receiving the Honk RPM. The industrial LG-RPM had no negative effects on animalperformance, best results were obtained with 25 and 30% of RPM. The Samourai RPM had no effect on the thyroid weight, whereas, the Honk RPM modified (P < 0.05) the histology of this organ; the percentages of large thyroid follicles being higher (P < 0.05) in the Honk group than in the Control and Samourai groups. High levels of Canola industrial LG-RPM(from 20%) induced also an hyperthyroidism. The Samourai and Honk RPM decreased (P < 0.05) the secretions of thyroid hormones while the industrial LG-RPM did not affect these hormones in any way. RPM had no significative effects on other hormones. It was concluded that disturbance in thyroid histology and activity induced by the ingestion of RPM did not affect the physiology and performance of lambs and that the levels between 25 to 30% of a LG-RPM were optimal for growing and fattening lambs. [less ▲]

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See detailOptimal linear taxation under endogenous longevity
Pestieau, Pierre ULg; Leroux, ML; Ponthiere, Gregory

in Journal of Population Economics (2011), 24

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See detailOptimal location of inter-modal terminals
Jourquin, Bart; Limbourg, Sabine ULg

Conference (2004)

The known methods to solve the problem of the optimal location of inter-modal terminals are “node” based, in the sense that they use the locations of the demands and the supplies as main input. The basic ... [more ▼]

The known methods to solve the problem of the optimal location of inter-modal terminals are “node” based, in the sense that they use the locations of the demands and the supplies as main input. The basic idea of this new research is to use the flows between these origins and destinations as additional input. [less ▲]

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See detailOptimal location of inter-modal terminals
Jourquin, Bart; Limbourg, Sabine ULg

Conference (2005)

The optimal location of a facility is a rather complex task that was already studied many times. Several optimal location problems and solution exists, but only a few can be applied to the location of ... [more ▼]

The optimal location of a facility is a rather complex task that was already studied many times. Several optimal location problems and solution exists, but only a few can be applied to the location of multimodal freight terminals. Among the possible approaches, if theoretical solutions can be found in the literature, the computational complexity of the proposed methods make them impossible to be applied to real world large geographical networks. Indeed, many of them are based on linear programming, for which the number of constraints drastically increases with the number of terminals to take into account. This paper identifies the possible existing theoretical exact solutions and the framework of a new approach, in which the initial set of potential terminals is computed by means of the results obtained by the assignment of the flows of commodities on the trans-European network. [less ▲]

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See detailOptimal management of migraine taking into account comorbidities and “positive side effects”
Sándor, C; Dodick, DW; Schoenen, Jean ULg

in Schoenen, Jean; Dodick, DW; Sándor, C (Eds.) Comorbidity in Migraine (2011)

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See detailOptimal multi-subject fMRI experiments
Maus, Bärbel ULg; van Breukelen, Gerard J P; Goebel, R et al

Conference (2011)

Functional magnetic resonance imaging is a neuroimaging method which is used to study the human brain and its functional areas. In multi-subject fMRI experiments, data from several subjects is collected ... [more ▼]

Functional magnetic resonance imaging is a neuroimaging method which is used to study the human brain and its functional areas. In multi-subject fMRI experiments, data from several subjects is collected while these subjects perform each the same task of interest, e.g., passive viewing of houses presented on a screen, in the scanner. In my talk optimal designs for multi-subject fMRI experiments with fixed experimental budget are considered. The optimal combination of number of subjects and fMRI scanner time/imaging time per subject will be studied. Analytical and numerical results based on a linear mixed effects model with uncorrelated and correlated errors will be presented for common parameters of fMRI experiments. It will be shown how the optimal number of subjects and optimal scanner [less ▲]

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See detailOptimal parametrizations for surface remeshing
Marchandise, Emilie; Remacle, Jean-François; Geuzaine, Christophe ULg

in Engineering with Computers (2012)

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See detailOptimal power flow computations with a limited number of controls allowed to move
Capitanescu, Florin ULg; Wehenkel, Louis ULg

in IEEE Transactions on Power Systems (2010), 25(1), 586-587

This letter focuses on optimal power flow (OPF) computations in which no more than a pre-specified number of controls are allowed to move. To determine an efficient subset of controls satisfying this ... [more ▼]

This letter focuses on optimal power flow (OPF) computations in which no more than a pre-specified number of controls are allowed to move. To determine an efficient subset of controls satisfying this constraint we rely on the solution of a mixed integer linear programming (MILP) problem fed with sensitivity information of controls' impact on the objective and constraints. We illustrate this approach on a 60-bus system and for the OPF problem of minimum load curtailment cost to remove thermal congestion. [less ▲]

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See detailOptimal power flow computations with constraints limiting the number of control actions
Capitanescu, Florin ULg; Rosehart, William; Wehenkel, Louis ULg

in IEEE Power Tech conference (2009, July)

This paper focuses on optimal power flow (OPF) computations in which no more than a pre-specified number of controls are allowed to move. The benchmark formulation of this OPF problem constitutes a mixed ... [more ▼]

This paper focuses on optimal power flow (OPF) computations in which no more than a pre-specified number of controls are allowed to move. The benchmark formulation of this OPF problem constitutes a mixed integer nonlinear programming (MINLP) problem. To avoid the prohibitive computational time required by classical MINLP approaches to provide a (potentially sub-optimal) solution, we propose instead two alternative approaches. The first one consists in reformulating the MINLP problem as a mathematical program with equilibrium constraints (MPEC). The second approach includes in the classical OPF problem a nonlinear constraint which approximates the integral constraint limiting the number of control variables movement. Both approaches are solved by an interior point algorithm (IPA), slightly adapted to the particular characteristics of each approach. We provide numerical results with the proposed approaches on two test systems and for two practical problems: minimum cost to remove thermal congestion, and minimum cost of load curtailment to restore a feasible equilibrium point. [less ▲]

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See detailOptimal processing of wind tunnel measurements in view of stochastic structural design of large flexible structures
Blaise, Nicolas ULg; Denoël, Vincent ULg

in Lerner, J. C.; Boldes, U. (Eds.) Wind Tunnels and Experimental Fluid Dynamics Research (2011)

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See detailOptimal procurement decisions in the presence of total quantity discounts and alternative product recipes
Crama, Yves ULg; Pascual, R.; Torres, A.

in European Journal of Operational Research (2004), 159(2), 364-378

We describe the purchasing decisions faced by a multi-plant company. The suppliers of this company offer complex discount schedules based on the total quantity (rather than cost) of ingredients purchased ... [more ▼]

We describe the purchasing decisions faced by a multi-plant company. The suppliers of this company offer complex discount schedules based on the total quantity (rather than cost) of ingredients purchased. The schedules simultaneously account both for corporate purchases and for purchases at the individual plant level. The complexity of the purchasing decisions is further increased due to the existence of alternative production recipes for each final product. We formulate the corresponding cost-minimization problem as a nonlinear mixed 0-1 programming problem. We propose various ways to linearize this formulation, and we evaluate the quality of the resulting models on real-world data. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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