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See detailPrévisions de fumure pour 1989
Falisse, André; Poelaert, Jean; Bodson, Bernard ULg et al

in Fumure et protection phytosanitaire des céréales (1989, February 23)

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See detailPrévisions de fumures
Poelaert, Jean; Falisse, André; Bodson, Bernard ULg et al

in Fumure et protection phytosanitaire des céréales (1983, February 24)

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See detailPrévisions des rendements du blé d’hiver à échelle régionale par modélisation de la courbe de chute de l’indice foliaire
Kouadio, Amani Louis ULg

Doctoral thesis (2012)

Estimation of cereal-crop production is considered as a priority in most crop research programs due to the relevance of food grain to world agricultural production. A large number of agrometeorological ... [more ▼]

Estimation of cereal-crop production is considered as a priority in most crop research programs due to the relevance of food grain to world agricultural production. A large number of agrometeorological models for crop yield assessment are available with various levels of complexity and empiricism. The current development of models for wheat yield forecasts, however, does not always reflect the inclusion of the loss of valuable green area and its relation to biotic and abiotic processes in production situation. At the field level, the close correlation between green leaf area during maturation and grain yield in wheat revealed that the onset and rate of senescence appeared to be important factors for determining wheat grain yield. Earth observation data, owing to their synoptic, timely and repetitive coverage, have been recognized as a valuable tool for crop monitoring at different levels. Our study sought to explore an approach for winter wheat (Triticum aestivum L.) yield forecasts at a regional scale, based on metrics derived from the senescence phase of the green area index (GAI). The senescence phase of winter wheat was analyzed and its modelling was achieved through two curve-fitting functions (modified Gompertz and logistic function). Metrics derived from these functions and characterizing this phase (i.e. the maximum value of GAI, the senescence rate and the time taken to reach either 37% or 50% of the remaining green surface in the senescent phase) were related to grain yields. The Senescence-based Approach For Yield estimates (SenAFY) was established and first tested at plot scale based on GAI values derived from digital hemispherical photograph. Then, it was applied at a regional scale using GAI temporal profiles retrieved from MODIS data. This second part of our study took advantage of recent methodological improvements in which imagery with high revisit frequency but coarse spatial resolution can be exploited to derive crop-specific GAI time series by selecting pixels whose ground-projected instantaneous field of view is dominated by the winter wheat. The regression-based models derived from the SenAFY provide interesting yield estimates at these two spatial scales. At regional scale, especially, the use of the SenAFY in order to forecast wheat yield gave satisfactory results. Such an approach may be considered as a first yield estimate that could be performed in order to provide better integrated yield assessments in operational systems. [less ▲]

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See detailPrévoir la septoriose : un modèle belge au Luxembourg
El Jarroudi, Moussa ULg; Giraud, Frédéric; Tychon, Bernard ULg et al

in Phytoma : La Défense des Végétaux (2011), 642

Septoria leaf blight caused by Septoria tritici Roberge ex Desmaz. (anamorph of Mycosphaerella graminicola) is one of the most serious foliar diseases on winter wheat which farmers in Luxembourg. It need ... [more ▼]

Septoria leaf blight caused by Septoria tritici Roberge ex Desmaz. (anamorph of Mycosphaerella graminicola) is one of the most serious foliar diseases on winter wheat which farmers in Luxembourg. It need to take into account when deciding upon fungicide application during stem elongation. Management of S. tritici aims at keeping the top two leaf layers free from infection, as these leaves contribute most to grain yield. The model PROCULTURE has been developed to simulate the progress of the Septoria leaf blotch disease on winter wheat during the cropping season. The model has been validated in Luxembourg for 3-years (2000 to 2002) at distinct representative sites. Proculture forecasts have been shown to be correct in about 85% of all cases. This model has since 2004 been used in the Grand-Duchy of Luxemburg in order to find the optimum time of fungicide spray in fields. On average, no spray of fungicides or only one application is required to efficiently control Septoria leaf blotch. In the Oesling (north of G-D of Luxembourg), treatments based on the Septoria risk simulation model were recommended only once, in 2007. The climatic conditions of the Oesling tend to favour organic farming in a region where foliar disease pressure is very weak. [less ▲]

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See detailLa Prévoyance Sociale ou la gestion habile d'une coopérative socialiste
Geerkens Provin, Eric ULg

in Peiren, Luc; Geerkens Provin, Eric; Vincent, Anne (Eds.) et al Cent ans de P&V 1907-2007. L'histoire originale d'une société coopérative d'assurances, vol. 2 (2007)

Les quatre chapitres qui forment cette contribution traitent, suivant un plan chronologique distinguant quatre périodes, des aspects économiques de l'histoire de La Prévoyance Sociale, société coopérative ... [more ▼]

Les quatre chapitres qui forment cette contribution traitent, suivant un plan chronologique distinguant quatre périodes, des aspects économiques de l'histoire de La Prévoyance Sociale, société coopérative d'assurances, fondée en 1907. L'exposé des structures et de l'organisation de la société dans ses différentes composantes — organes dirigeants et organisation générale de l'activité, politique du personnel, de l'administration centrale autant que des inspections, et stratégie de promotion des activités — introduit l'examen du développement de son activité dans ses diverses branches et de sa politique de placement. [less ▲]

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See detailA 'price balance statistic' for optimizing pricing strategies: a better estimation of elasticities and cross-elasticities
Lurkin, Virginie ULg; Schyns, Michael ULg; Garrow, Laurie A. et al

Conference (2014, May 16)

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has ... [more ▼]

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has typically been studied separately from the others. Yet, better understanding their relationship gives an airline the opportunity to increase its profitability. In prior work, Tim Jacobs and colleagues introduced a macro-level metric known as the ‘Price Balance Statistic (PBS)’ for evaluating the quality of a given pricing strategy and guiding a search algorithm to identify an optimal alignment between pricing structure, scheduled capacity and RM controls using marginal revenue principles. The aim of our work is to incorporate additional modeling improvements to the PBS. The current model formulation uses price elasticity as input parameters and assumes perfect independency between the different fare classes. However, in reality, a passenger demand fluctuates between classes based on differences in prices. We propose to use instrumented variable linear regression methods to obtain parameter estimates for price elasticities and cross-elasticities. This modification incorporates accurate price elasticities but also the impact of a change in one fare class on another through the cross-elasticities. [less ▲]

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See detailA 'price balance statistic' for optimizing pricing strategies: a better estimation of elasticities and cross-elasticities
Lurkin, Virginie ULg; Schyns, Michael ULg; Garrow, Laurie A. et al

Conference (2014, May 15)

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has ... [more ▼]

Demand forecasting, price optimization and capacity controls form three major tools of revenue management. Over the past few decades, each discipline has generated a great deal of research but has typically been studied separately from the others. Yet, better understanding their relationship gives an airline the opportunity to increase its profitability. In prior work, Tim Jacobs and colleagues introduced a macro-level metric known as the ‘Price Balance Statistic (PBS)’ for evaluating the quality of a given pricing strategy and guiding a search algorithm to identify an optimal alignment between pricing structure, scheduled capacity and RM controls using marginal revenue principles. The aim of our work is to incorporate additional modeling improvements to the PBS. The current model formulation uses price elasticity as input parameters and assumes perfect independency between the different fare classes. However, in reality, a passenger demand fluctuates between classes based on differences in prices. We propose to use instrumented variable linear regression methods to obtain parameter estimates for price elasticities and cross-elasticities. This modification incorporates accurate price elasticities but also the impact of a change in one fare class on another through the cross-elasticities. [less ▲]

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See detailPrice competition under universal service obligations
Gautier, Axel ULg; Wauthy, Xavier

in International Journal of Economic Theory (2010), 6(3), 311-326

In industries like telecom, postal services or energy provision, universal service obligations (uniform price and universal coverage) are often imposed on one market participant. Universal service ... [more ▼]

In industries like telecom, postal services or energy provision, universal service obligations (uniform price and universal coverage) are often imposed on one market participant. Universal service obligations are likely to alter firms' strategic behavior in such competitive markets. In this paper we show that, depending on the entrant's market coverage and the degree of product differentiation, the Nash equilibrium in prices involves either pure or mixed strategies. We show that the pure strategy market sharing equilibrium, as identified by Valletti et al. (2002) defines a lower bound on the level of equilibrium prices. [less ▲]

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See detailPrice Competition under Universal Service Obligations
Gautier, Axel ULg

Conference (2010, September)

In industries like telecom, postal services or energy provision, universal service obligations (uniform price and universal coverage) are often imposed on one market participant. Universal service ... [more ▼]

In industries like telecom, postal services or energy provision, universal service obligations (uniform price and universal coverage) are often imposed on one market participant. Universal service obligations are likely to alter firms' strategic behavior in such competitive markets. In this paper we show that, depending on the entrant's market coverage and the degree of product differentiation, the Nash equilibrium in prices involves either pure or mixed strategies. We show that the pure strategy market sharing equilibrium, as identified by Valletti et al. (2002) defines a lower bound on the level of equilibrium prices. [less ▲]

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See detailPrice Discrimination Under Ec Competition Law: Another Antitrust Theory in Search of Limiting Principles
Petit, Nicolas ULg; Geradin, Damien

in GCLC (2005)

Price discrimination is one of the most complex areas of EC competition law. There are several reasons for this. First, the concept of price discrimination covers many different practices (discounts and ... [more ▼]

Price discrimination is one of the most complex areas of EC competition law. There are several reasons for this. First, the concept of price discrimination covers many different practices (discounts and rebates, tying, selective price cuts, discriminatory input prices set by vertically-integrated operators, etc.) whose objectives and effects on competition significantly differ. From the point of view of competition law analysis, it is thus not easy to classify these practices under a coherent analytical framework. Second, there is a consensus among economists that the welfare effects of the (various categories of) price discrimination are ambiguous. It is hard to say a priori whether a given form of price discrimination increases or decreases welfare. The response to this question may indeed depend on which type of welfare standard (total or consumer) is actually pursued. Moreover, even if one agrees on a given standard, the welfare effects of discriminatory prices generally depend on factual issues, such as whether it increases or decreases total output. Third, the exact scope of Article 82(c), the only Treaty provision dealing with discrimination, is not entirely clear. While the European Commission (hereafter, the Commission) and the Community courts have applied Article 82(c) to many different practices, there are good reasons to believe that this provision should be applied to a limited set of circumstances, most forms of discrimination being adequately covered by Article 82(b) or other provisions of the Treaty. Against this background, the main objective of this paper is to throw some light on the compatibility of price discrimination with EC competition law. In order to do so, this paper does not seek to propose a grand unifying theory that would provide a single test offering a way to distinguish between practices compatible and incompatible with the EC Treaty. Instead, we offer an analytical framework which distinguishes between different categories of price discrimination depending on their effects on competition. Different tests may thus be needed to assess the compatibility of the practices belonging to these categories with EC competition law. Another objective of the paper is to show that Article 82(c) should only be applied to the limited circumstances where a non-vertically integrated dominant firm price discriminates between customers with the effect of placing one or several of them at a competitive disadvantage vis-a-vis other customers (secondary line price discrimination). In contrast, Article 82(c) should not be applied to pricing measures designed to harm the dominant firm's competitors (first line price discrimination) or to fragment the single market across national lines. As will be seen, relying on Article 82(c) to condemn such practices goes against the letter and the spirit of this provision and may also apply a wrong test to such practices. It is also not necessary since other Treaty provisions can be used to achieve this objective. [less ▲]

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See detailThe Pricing of Equity on the London Stock Exchange: Seasonality and Size premium
Corhay, Albert ULg; Hawawini, Gabriel; Michel, Pierre-Armand

in Dimson, Elroy (Ed.) Stock Market Anomalies (1988)

Detailed reference viewed: 58 (2 ULg)
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See detailPrières et variations sur les motifs du bilan et du pèlerinage
Dor, Juliette ULg

in Louviot, Elise; Stévanovitch, Colette; Mahoux, Philippe (Eds.) et al Everyman (2009)

Detailed reference viewed: 24 (10 ULg)
See detailThe priest, the universe, and the Big Bang
Nazé, Yaël ULg

Article for general public (2007)

A Belgian priest's extraordinary insights anticipated modern cosmology's most fundamental ideas: Georges Henri Joseph Edouard Lemaître.

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See detailPriests and Cult Personnel in Three Hellenistic Families
Carbon, Jan-Mathieu ULg; Pirenne-Delforge, Vinciane ULg

in Horster, Marietta; Klöckner, Anja (Eds.) Cities and Priests. Cult Personnel in Asia Minor and the Aegean Islands from the Hellenistic to the Imperial Period (2013)

This paper offers an examination of three significant familial inscriptions from the Hellenistic period. The texts are detailed cultic dossiers initiated by three individuals—Diomedon on Cos, Poseidonios ... [more ▼]

This paper offers an examination of three significant familial inscriptions from the Hellenistic period. The texts are detailed cultic dossiers initiated by three individuals—Diomedon on Cos, Poseidonios in Halicarnassus, and Epikteta on Thera. Though they are often very briefly grouped together, these inscriptions are discussed here in greater textual and contextual detail. In particular, the analysis focusses on the cult personnel, which is appointed in these families, demonstrating that it remains independent from the polis, but is organised with reference to a civic framework. By setting these inscriptions in parallel, the discussion opens up productive perspectives on the evolutions of familial cults in the Hellenistic period.—The inscription of Poseidonios is reedited in an Appendix by Jan-Mathieu Carbon. [less ▲]

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See detailPRIM related correlations
Mathéi, Axel ULg

Conference (2013, March 07)

Detailed reference viewed: 33 (8 ULg)
See detailA primal-dual approach in truss topology optimization
Beckers, Maryse; Fleury, Claude ULg

in Topping, B. H. V.; Papadrakakis, Manolis (Eds.) Advances in Structural Optimization (1994)

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See detailA primal-dual approach in truss topology optimization
Beekers, M.; Fleury, Claude ULg

in Computers & Structures (1997), 64(1-4), 77-88

The objective of truss topology optimization is to find, for a given weight, the stiffest truss, defined as a subset of an initially choosen set of bars called the ground structure. The restrictions are ... [more ▼]

The objective of truss topology optimization is to find, for a given weight, the stiffest truss, defined as a subset of an initially choosen set of bars called the ground structure. The restrictions are bounds on bar volumes and the satisfaction of equilibrium equations. For a single load case and without bounds on bar volumes, the problem can be written as a linear programming problem with nodal displacements as variables. The addition to the objective function of a quadratic term vanishing at the optimum allows us to use a dual solution scheme. A conjugate gradient method is well suited to maximize the dual function. Several ground structures are introduced. For large networks, those where each node is connected to those situated in a certain vicinity give a good compromise between generating a reasonable number of bars and obtaining a sufficient number of possible directions. Some examples taken from the literature are treated to illustrate the quality of the solution and the influence of initial topology. (C) 1997 Civil-Comp Ltd and Elsevier Science Ltd. [less ▲]

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