Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailInventories and Maps: Cognitive Ways of Framing the Nature Policies in Europe
Mougenot, Catherine ULg; Remy, Elisabeth

in Journal of Environmental Policy & Planning (2002), 4(4), 313-322

Since the Earth Summit in Rio, declining biodiversity has become a subject of general concern for many countries. To counter these negative trends, government nature policies in Europe at least are now ... [more ▼]

Since the Earth Summit in Rio, declining biodiversity has become a subject of general concern for many countries. To counter these negative trends, government nature policies in Europe at least are now thought out primarily in terms of networks. They concern new areas outside nature reserves, new players and new management strategies. Consequently, these policies should themselves become the subject of new public debate. Our study concerns the analysis of the forms used to collect the data required to set up the European Union's Natura 2000 network and maps drawn as part of the Council of Europe's Pan-European Ecological Network strategy. The aim of this article, which takes the perspective developed by the sociology of science, will be to show how the forms and maps used in these new nature policies produce knowledge that precedes policy discussions to search for the best possible socio-political compromises. In other words, the knowledge that is collected in and by means of these documents, forms and maps offers a cognitive way of framing the subsequent public debates. [less ▲]

Detailed reference viewed: 31 (10 ULg)
Full Text
Peer Reviewed
See detailInventory control in a decentralised two-stage make-to-stock queueing system
Arda, Yasemin ULg; Hennet, Jean-Claude

in International Journal of Systems Science (2008), 39(7),

In an Enterprise network, several companies interact to produce families of goods. Each member company seeks to optimise his own production and inventory policy to maximise his profit. These objectives ... [more ▼]

In an Enterprise network, several companies interact to produce families of goods. Each member company seeks to optimise his own production and inventory policy to maximise his profit. These objectives are generally antagonistic and can lead to contradictory choices in the context of a network with a high degree of local decisional autonomy. To avoid a global loss of economic efficiency, the network should be equipped with a coordination mechanism. The present article describes a coordination contract negotiated between a manufacturer and a supplier. The purpose of the negotiation is to determine the price of the supplied intermediate goods and the delay penalty in case of a late delivery. For a manufacturer with a dominant contracting position, the outcome of the negotiation can be computed as a Stackelberg equilibrium point. Under the resulting contract, the two-stage supply chain reaches globally optimal running conditions with the maximal possible profit obtained by the manufacturer and the smallest acceptable profit obtained by the supplier. [less ▲]

Detailed reference viewed: 82 (21 ULg)
Peer Reviewed
See detailInventory control in a decentralized two-stage make-to-stock queuing system
Arda, Yasemin ULg; HENNET, Jean-Claude

in INCOM 06, 12th IFAC Symposium on Information Control Problems in Manufacturing, Saint-Etienne, France, 17-19 May 2006 (2006, May 17)

In an Enterprise network, several companies interact to produce families of goods. Each member company seeks to optimize his own production and inventory policy to maximize his profit. These objectives ... [more ▼]

In an Enterprise network, several companies interact to produce families of goods. Each member company seeks to optimize his own production and inventory policy to maximize his profit. These objectives are generally antagonistic and can lead to contradictory choices in the context of a network with a high degree of local decisional autonomy. To avoid a global loss of economic efficiency, the network should be equipped with a coordination mechanism. The present paper describes a coordination contract negotiated between a manufacturer and a supplier. The purpose of the negotiation is to determine the price of the supplied intermediate goods and the delay penalty in case of a late delivery. For a manufacturer with a dominant contracting position, the outcome of the negotiation can be computed as a Stackelberg equilibrium point. Under the resulting contract, the two-stage supply chain reaches globally optimal running conditions with the maximal possible profit obtained by the manufacturer and the smallest acceptable profit obtained by the supplier. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailInventory control in a multi-supplier system
Arda, Yasemin ULg; Hennet, Jean-Claude

in International Journal of Production Economics (2006), 104

An enterprise network is analyzed from the viewpoint of an end-product manufacturer who receives customer orders and organises his production and supply policy so as to minimize the sum of his average ... [more ▼]

An enterprise network is analyzed from the viewpoint of an end-product manufacturer who receives customer orders and organises his production and supply policy so as to minimize the sum of his average holding cost and average stockout cost. For each main component to be ordered, the producer has several possible suppliers. The arrivals of customers’ orders are random and delivery times from suppliers are also supposed random. This supply system is represented as a queuing network where the producer uses a base-stock inventory control policy that keeps constant the inventory position level (current inventory level+pending replenishment orders). The decision variables are the reference inventory position level and the percentages of orders sent to the different suppliers. In the queuing network model, the percentages of orders are implemented as Bernoulli branching parameters. A close-form expression of the expected cost criterion is obtained as a complex non-linear function of decision variables. A decomposed approach is proposed for solving the optimization problem in an approximate manner. The quality of the approximate solution is evaluated by comparison to the exact solution, which can be computed numerically in some simple cases, in particular in the two-supplier case. Numerical applications show the important economic advantage for the producer of sending orders to several suppliers rather than to a single one. [less ▲]

Detailed reference viewed: 53 (10 ULg)
Peer Reviewed
See detailInventory control in a multi-supplier system
Arda, Yasemin ULg; Hennet, Jean-Claude

in IGLS 04, 13th International Working Seminar on Production Economics, Igls/Innsbruck, Austria, 16-20 February 2004 (2004, February 16)

An enterprise network is analyzed from the viewpoint of an end-product manufacturer who receives customer orders and organises his production and supply policy so as to minimize the sum of his average ... [more ▼]

An enterprise network is analyzed from the viewpoint of an end-product manufacturer who receives customer orders and organises his production and supply policy so as to minimize the sum of his average holding cost and average stock-out cost. For each main component to be ordered, the producer has several possible suppliers. The arrivals of customers’ orders are random and delivery times from suppliers are also supposed random. This supply system is represented as a queuing network and the producer uses a base-stock inventory control policy that keeps constant the position inventory level (current inventory level + pending replenishment orders). The decision variables are the reference position inventory level and the percentages of orders sent to the different suppliers. In the queuing network model, the percentages of orders are implemented as Bernoulli branching parameters. A close-form expression of the expected cost criterion is obtained as a complex non-linear function of decision variables. A decomposed approach is proposed for solving the optimization problem in an approximate manner. The quality of the approximate solution is evaluated by comparison to the exact solution, which can be computed numerically in some simple cases, in particular in the two-supplier case. Numerical applications show the important economic advantage for the producer of sending orders to several suppliers rather than to a single one. [less ▲]

Detailed reference viewed: 6 (0 ULg)
Full Text
Peer Reviewed
See detailAn inventory of emerging innovation project in belgium, Typical and traditional products: rural effect and agro-industrial problems, Parma – Italy ,
Van Huylenbroeck, I.; Verhaegen, Ingrid; Collet, Eric et al

in Proceeding of the 52nnd Seminar of the EAAE (1998)

Detailed reference viewed: 16 (8 ULg)
Full Text
Peer Reviewed
See detailInventory-routing problem with pickups and deliveries of RTI in closed-loop supply chain
Iassinovskaia, Galina; Limbourg, Sabine ULg; Riane, Fouad

Conference (2014, July 17)

Reducing environmental impact, related regulations and potential for operational benefits are the main reasons why companies share their Returnable Transport Items (RTIs) among different partners of a ... [more ▼]

Reducing environmental impact, related regulations and potential for operational benefits are the main reasons why companies share their Returnable Transport Items (RTIs) among different partners of a closed-loop supply chain. This research deals with an inventory-routing problem with pickups and deliveries of RTIs. A mixed-integer linear program is developed and tested on small instances. To handle realistic large size problems, a clustering algorithm is coupled with a simulation model. This hybrid heuristic allows assessing the benefits of information and RTIs sharing among partners. [less ▲]

Detailed reference viewed: 37 (8 ULg)
Full Text
See detailInventorying urban areas with Very High Resolution Satellite Images
Van de Voorde, Tim; Binard, Marc ULg; Op ’t Eyndt, Tom

in Ramon, J.; Ruiz, M.; Gold, M. (Eds.) Procredings of the 5th AGILE Conference on Geographical Information Science (2002)

Prior to the commercial availability of Very High Resolution (VHR) satellite imagery, the applicability of Earth Observation data in the urban planning sector was very limited. The spatial resolution of ... [more ▼]

Prior to the commercial availability of Very High Resolution (VHR) satellite imagery, the applicability of Earth Observation data in the urban planning sector was very limited. The spatial resolution of the imagery, supplied by platforms like Landsat TM and SPOT HRV, was too coarse to be of real practical use to urban planners and their applications. Satellite images of urban or sub-urban areas are characterized by large radiometric variations due to the small size and the diversity of the objects. This in turn causes a radiometric contamination between neighbouring pixels which renders object recognition nearly impossible. Satellite images with a higher resolution might alleviate this problem. The dawn of the VHR era was thus anticipated with great aspiration by urban remote sensing researchers. In the framework of a DWTC/OSTC Telsat 4 pilot project we proposed a methodology to employ IKONOS-21 imagery to develop an inventory of built-up, and un-built areas in Belgium’s Flemish region. Such an inventory can be of use to regional planning agencies that are responsible for the implementation of the government’s planning policies. In Flanders, AROHM (Administration of Spatial Planning, Housing, Monuments and landscapes) records, monitors, and evaluates the built-up areas. To do this, they need an extensive data input from the communities, which requires a lot of time and effort. A reliable and swift technique, based on earth observation data, and applicable for each residential area in Flanders, would be of great value to them. Not only would it allow them to make swift assessments more frequently, they could also double-check incoming data from the communities. The aforementioned project consisted of three parts: the visual interpretation of two study areas (Hasselt and Ghent), the automatic classification of these areas using both Maximum Likelihood and Neural Network classifiers, and the development of GIS procedures to transform the classified images into thematic maps like, for instance, a map of building densities. [less ▲]

Detailed reference viewed: 51 (5 ULg)
Full Text
Peer Reviewed
See detailInverse analysis in geotechnics: soil parameter identification by genetic algorithm
Levasseur, Séverine ULg; Malécot, Yann; Boulon, Marc et al

in 8th. World Congress on Computational Mechanics (WCCM8) & 5th. European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) (2008)

Detailed reference viewed: 20 (1 ULg)
Full Text
Peer Reviewed
See detailInverse analysis on in situ geotechnical measurement using a genetic algorithm
Malécot, Yann; Levasseur, Séverine ULg; Boulon, Marc et al

in Pande, G. N.; Pietruszczak, S. (Eds.) Numerical Models in Geomechanics (2004)

This paper is dedicated to the identification of constitutive parameters of the Mohr-Coulomb constitutive model from in situ measurements. A general definition of an objective function is proposed. A ... [more ▼]

This paper is dedicated to the identification of constitutive parameters of the Mohr-Coulomb constitutive model from in situ measurements. A general definition of an objective function is proposed. A direct approach of inverse analysis is used to identify the shear modulus and the friction angle in four different situations. The first two examples deal with a “numerical” and with a real pressuremeter curve. A difficult convergence and a strong non unicity of solution is observed, which is classical in inverse analysis (ill posed problems). In a second stage, the horizontal displacements related to two excavation problems are used for identifying the two mechanical parameters. A clear minimum of the objective function is detected, giving a unique solution. The reasons of these differences are discussed and some ways of improving the interpretation of the pressuremeter test results are proposed. [less ▲]

Detailed reference viewed: 35 (2 ULg)
Full Text
Peer Reviewed
See detailInverse analysis techniques for parameter identification in simulation of excavation support systems
Rechea, Cecilia; Levasseur, Séverine ULg; Finno, Richard J

in Computers & Geotechnics (2008), 35(3), 331-345

Two numerical procedures are described that quantitatively identify a set of constitutive parameters that best represents observed ground movement data associated with deep excavations in urban ... [more ▼]

Two numerical procedures are described that quantitatively identify a set of constitutive parameters that best represents observed ground movement data associated with deep excavations in urban environments. This inverse problem is solved by minimizing an objective (or error) function of the weighted least-squares type that contains the difference between observed and calculated ground displacements. The problem is solved with two different minimization algorithms, one based on a gradient method and the other on a genetic algorithm. The objective function is shown to be smooth with a unique solution. Both methods are applied to lateral movements from synthetic and real excavations to illustrate various aspects of the implementation of the methods. The advantages and disadvantages of each method applied to excavation problems are discussed. [less ▲]

Detailed reference viewed: 42 (1 ULg)
Peer Reviewed
See detailInverse control of prolactin and growth hormone gene expression: effect of thyroliberin on transcription and RNA stabilization
Laverriere, J. N.; Morin, A.; Tixier-Vidal, A. et al

in EMBO Journal (1983), 2(9), 1493-9

The hypothalamic tripeptide thyroliberin (TRH) regulates prolactin (PRL) and growth hormone (GH) synthesis inversely by modulating the levels of their specific mRNA. Changes in mRNA levels could involve ... [more ▼]

The hypothalamic tripeptide thyroliberin (TRH) regulates prolactin (PRL) and growth hormone (GH) synthesis inversely by modulating the levels of their specific mRNA. Changes in mRNA levels could involve both transcriptional and posttranscriptional events. To examine further these possibilities, we have investigated the effect of TRH on the biosynthesis and degradation of PRL and GH RNA in a rat pituitary tumor cell line. Newly synthesized PRL and GH RNA sequences were quantified in nuclear and cytoplasmic fractions by hybridization of 3H-labelled RNA to immobilized plasmid DNA containing either PRL or GH cDNA sequences. Steady-state levels of specific RNA were estimated by RNA blot hybridization. The results indicate that TRH increases in a rapid but transient manner the transcription of the PRL gene, and suggest that it does not alter the processing and the transport to the cytoplasm. In contrast, after a lag-time, TRH seems to induce a long-lasting inhibition on GH, as well as on overall gene transcription. Furthermore, we observed an effect of TRH on mRNA stability. TRH significantly increases the half-life of PRL mRNA. Our results also support the hypothesis that TRH decreases the half-life of GH mRNA. Such post-transcriptional action of TRH amplifies and prolongs the regulations exerted at the transcriptional level. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Peer Reviewed
See detailInverse Design of Compressor and Turbine Blades at Transonic Flow Conditions
Léonard, Olivier ULg; Van den Braembussche, René

in Proceedings of the ASME Turbo Expo 1992 (1992, June)

Detailed reference viewed: 33 (1 ULg)
Full Text
See detailInverse dynamics of parallel kinematic manipulators with flexible links
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

Conference (2012, May)

Detailed reference viewed: 27 (11 ULg)
Full Text
Peer Reviewed
See detailInverse dynamics of serial and parallel underactuated multibody systems using a DAE optimal control approach
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

in Multibody System Dynamics (2013)

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper studies the inverse dynamics of non-minimum ... [more ▼]

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper studies the inverse dynamics of non-minimum phase underactuated multibody systems with serial and parallel planar topology, e.g. for end-effector control of flexible manipulators or manipulators with passive joints. Unlike for minimum phase systems, the inverse dynamics of non-minimum phase systems cannot be solved by adding trajectory constraints (servoconstraints) to the equations of motion and applying a forward time integration. Indeed, the inverse dynamics of a non-minimum phase system is known to be non-causal, which means that the control forces and torques should start before the beginning of the trajectory (preactuation phase) and continue after the end-point is reached (post-actuation phase). The existing stable inversion method roposed for general nonlinear non-minimum phase systems requires to derive explicitly the equations of the internal dynamics and to solve a boundary value problem. This paper proposes an alternative solution strategy which is based on an optimal control approach using a direct transcription method. The method is illustrated for the inverse dynamics of an underactuated serial manipulator with rigid links and four degrees-of-freedom and an underactuated parallel machine. An important advantage of the proposed approach is that it can be applied directly to the standard equations of motion of multibody systems either in ODE or in DAE form. Therefore, it is easier to implement this method in a general purpose simulation software. [less ▲]

Detailed reference viewed: 72 (18 ULg)
Full Text
See detailINVERSE DYNAMICS OF UNDERACTUATED MULTIBODY SYSTEMS USING A DAE OPTIMAL CONTROL APPROACH
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

in Proceedings of the ECCOMAS Thematic Conference (MULTIBODY DYNAMICS) 2011 (2011, July)

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper studies the inverse dynamics of non-minimum ... [more ▼]

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper studies the inverse dynamics of non-minimum phase underactuated multibody systems, e.g. for end-effector control of flexible manipulators or manipulators with passive joints. Unlike for minimum phase systems, the inverse dynamics of non-minimum phase systems cannot be solved by adding trajectory constraints to the equations of motion and by applying a forward time integration. Indeed, the inverse dynamics of a non-minimum phase system is known to be non-causal, which means that the control forces and torques should start before the beginning of the trajectory (pre-actuation phase) and continue after the end-point is reached (post-actuation phase). The existing stable inversion method proposed for general nonlinear non-minimum phase systems requires to derive explicitly the equations of the internal dynamics and to solve a boundary value problem. This paper proposes an alternative solution strategy which is based on an optimal control approach. The method is illustrated for the inverse dynamics of a planar underactuated manipulator with rigid links and four degrees-of-freedom. An important advantage of the proposed approach is that it can be applied directly to the standard equations of motion of multibody systems either in ODE or in DAE form. Therefore, it is easier to implement this method in a general purpose simulation software. [less ▲]

Detailed reference viewed: 115 (24 ULg)