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See detailModélisation de la répartition dynamique des produits phytopharmaceutiques sous une rampe de pulvérisation
Lebeau, Frédéric ULg

Doctoral thesis (2003)

A mathematical model aimed at estimating the distribution of spray deposits of phytopharmaceutical <br />products under a spray boom is proposed. It focuses on the need to take account of the dynamic ... [more ▼]

A mathematical model aimed at estimating the distribution of spray deposits of phytopharmaceutical <br />products under a spray boom is proposed. It focuses on the need to take account of the dynamic effects of <br />the forward movement of the boom. These are related both to the horizontal and vertical boom <br />movement and to the influence of aerodynamical factors on the nozzle spray distribution. <br />The model allows one to compute the spray deposits distribution by multiplying the nozzle spray <br />distribution by the time needed to move from one position to the next. Mathematically, this is expressed <br />by a convolution of the trajectory with the nozzle spray distribution. <br />The model is validated through a dynamic test bench aimed at reproducing the boom movements <br />observed in the field. The chosen method to measure spray deposits distribution is a chemical dosage of <br />the sprayed KCL solution collected in Petri dishes. This method is accurate if the spacing between <br />collectors is small enough. With constant speed and height, the longitudinal variability approaches 5 % <br />and the transversal spray deposits distribution is a function of the nozzle characteristics (as measured on <br />the static spray patternator) and of the nozzle speed. <br />A Pulse Width Modulation (PWM) nozzle boss fitted on the test bench is used to generate a dynamic <br />spray deposits distribution from which the dynamic bidimensional nozzle spray pattern is reconstructed. <br />This dynamic nozzle spray pattern introduced in the model allows a far better estimation of the spray <br />deposits distribution to be made than the one obtained using the static nozzle spray pattern computed <br />using filtered back-projection. <br />The use of the model for estimating the spray deposits distribution under a crop sprayer allows one <br />to identify the influential parameters and to calculate the dosages according to specific local <br />circumstances. Statistical parameters aimed at characterising the treatment quality are proposed. [less ▲]

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See detailModelisation de la repartition transversale du volume disperse par une rampe de pulverisateur.
Leunda, P.; Debouche, Charles ULg; Caussin, R.

in Dodd, V. A.; Grace, P. M. (Eds.) Agricultural Engineering: Agricultural mechanisation. Congress on Agricultural Engineering 11th (1989)

The reduction of volumes spread over an hectare, which is the most significant trend in field spraying practice, requires a more accurate control of the homogeneity of volume distribution under the ... [more ▼]

The reduction of volumes spread over an hectare, which is the most significant trend in field spraying practice, requires a more accurate control of the homogeneity of volume distribution under the spraying boom. This homogeneity admits two components, a longitudinal and a transversal one, the former being ensured by the recent developments of electronical equipment controlling the flow according to the speed of advancement. The transversal component is linked to the distribution of each isolated nozzle on the boom and depends on parameters such as nozzle spacing and spraying height and pressure, whose values are fixed by the users. A possible approach for optimizing the values given to those parameters consists in establishing a model of the distribution of an isolated nozzle, taking into account nozzle calibre, spraying pressure and boom height. This individual model can then be used to predict the transversal repartition under a boom and improve it by varying the spraying parameters and nozzle spacing on the boom. [less ▲]

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See detailModelisation de la reponse des flux de respiration d'un sol forestier selon les principales variables climatiques.
Perrin, Dominique ULg; Laitat, E.; Aubinet, Marc ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2004), 8(1),

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See detailModélisation de la transition solide-fluide dans les géomatériaux. Application aux glissements de terrain.
Prime, Noémie ULg

Doctoral thesis (2012)

Geomaterials are present in nature in many forms : solid soil or rock, soft clay, almost liquid mud, etc. Geomechanics deals with the understanding the solid behavior of geomaterials. However, solid ... [more ▼]

Geomaterials are present in nature in many forms : solid soil or rock, soft clay, almost liquid mud, etc. Geomechanics deals with the understanding the solid behavior of geomaterials. However, solid ground can happen, under specific external conditions, to turn into fluid : as for example during mudflows or debris flows. In such a context, our work concerns, in a general way, solid-fluid transition in geomaterials behavior and the development of a constitutive model describing both the solid phase, fluid phase, and the transition between the two. In this framework, we chose to carry out calculations with the FEMLIP numerical method (Finite Element Method with Lagrangians Integration Points) which has shown a strong potential to describe a wide variety of behaviors (including history dependent behavior), in a unique model. Having implemented and validated the first elasto-plastic law in Ellipsis (FEMLIP based code), we have introduced in this code the solid-fluid transition model. This last is based on the evolution, at the failure state detected by the second order work criterion, of the solid elasto-plastic behavior towards a viscous fluid behavior, exhibiting a yield stress. After validation of the solid-fluid transition model in homogeneous cases (considering Plasol elasto-plastic law and Bingham viscous one), we applied this model to the modeling of Sarno and Quindici mudflows (Italy, 1998). [less ▲]

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See detailModélisation de phénomènes périodiques
Henry, Valérie ULg

in Tangente (2005), 28

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See detailModélisation de problèmes hydroélastiques par éléments finis. Application aux lanceurs aérospatiaux
Debongnie, Jean-François ULg

Doctoral thesis (1978)

This thesis is devoted to the finite element analysis of hydro-elastic vibrations arising in launchers. It sets a general formulation generalizing Tong's one by a logical step in a lagrangian point of ... [more ▼]

This thesis is devoted to the finite element analysis of hydro-elastic vibrations arising in launchers. It sets a general formulation generalizing Tong's one by a logical step in a lagrangian point of view. A specialized solution algorithm is presented. As launchers are axisymmetric structures, a general theory of axisymmetric structures with cosinusoidal modes is presented, including shells, volumes, and incompressible structures. The problem of setting the ccorrest limiting conditions on the axis is treated. Special pressure terms are also treated. [less ▲]

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Peer Reviewed
See detailModélisation de spectres de contraintes et application à la résistance en fatigue
Franssen, Jean-Marc ULg

in Revue de la soudure (1985), 2

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See detailModélisation de structures voiles en béton armé soumises à du cisaillement
Soufflet, Marc; Kotronis, Panagiotis; Collin, Frédéric ULg

Conference (2013)

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See detailModélisation des champs sonores en acoustique architecturale par un processus de diffusion
Picaut, Judicaël; Billon, Alexis ULg; Valeau, Vincent et al

Conference (2010, April)

La modélisation des champs sonores en acoustique architecturale est d'autant plus complexe que la géométrie d'étude est elle-même complexe. En particulier, le domaine de propagation peut présenter de ... [more ▼]

La modélisation des champs sonores en acoustique architecturale est d'autant plus complexe que la géométrie d'étude est elle-même complexe. En particulier, le domaine de propagation peut présenter de nombreux volumes couplés de tailles très différentes, connectés par de faibles surfaces de couplage. Dans ces conditions, les formulations analytiques classiques, basées par exemple sur la théorie de la réverbération, ou les méthodes numériques, basées par exemple sur des méthodes de tracé de rayons ou de faisceaux sonores, sont difficilement applicables, voire impossibles. Ces dernières années, une solution alternative, fondée sur l'utilisation d'une équation de diffusion pour la densité d'énergie sonore, a été développée et validée. Dans ce présent travail, nous présentons les développements permettant ainsi de modéliser les champs sonores en acoustique des salles, en prenant en compte les difféerents phénomènes propagatifs mis en jeu, tel que l'atténuation atmosphérique, l'absorption par les parois, la transmission acoustique à travers les cloisons et la réflexion mixte au niveau des surfaces. Dans un second temps, nous présentons la méthode retenue pour la résolution numérique des équations de diffusion mises en jeu. A cet effet, une interface logicielle a été spécialement développée, permettant de manipuler de manière fonctionnelle les données géométriques et acoustiques du problème, avant l'exécution d'un logiciel de calcul multi-physique, en s'affranchissant ainsi du formalisme spécifique associé au modèle de diffusion. Cette interface permet ensuite le post-traitement de l'ensemble des résultats, notamment afin de déterminer et de représenter différents paramètres classiques d'acoustique des salles (niveaux sonores, temps de réverbération. . . ). [less ▲]

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See detailModélisation des conditions d’apparition du micro-hydrodynamisme via la méthode des éléments finis dans la perspective d’intégrer ce phénomène dans un modèle numérique de laminage à froid.
Carretta, Yves ULg

Doctoral thesis (2014)

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto ... [more ▼]

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto, appears in the mixed lubrication regime. It consists in lubricant flows at the microscopic scale leading to a lubrication of the tool-piece solid contacts and therefore to a local friction drop. For instance, Laugier et al. have observed a friction decrease while rolling High Strength Steels for different strip thickness reductions. The only physical explanation to this trend is the MPH lubrication. Despite the huge influence of MPH lubrication on friction in metal forming processes, only a few numerical models can be found in the literature. Moreover, these models rely on several restrictive assumptions which prevent them from delivering predictive results. This work consists in the development of the first finite element model capable of predicting the appearance of the MPH lubrication. This model is used to numerically reproduce the experiments of Bech who studied this phenomenon, in plane strip drawing, by observing the behaviour of macroscopic pyramidal lubricant cavities through a transparent die. In the proposed approach, plane strip drawing is modelled in 2D with Metafor, an in-house nonlinear FE code. This model allows us to compare the lubricant pressure to the solid-solid contact pressure profile between the upper die and the strip material. Once the lubricant pressure exceeds the solid-to-solid contact pressure, the condition allowing a lubricant flow from the pocket to the neighbouring plateaus is fulfilled. The presented FE model is able to predict backward and forward escapes of the lubricant from the pocket. As in the experiments of Bech, several parametric studies have been carried out. The numerical results show that the model reproduces the trends observed experimentally. [less ▲]

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See detailModélisation des couplages entre eau souterraine, rivières et mer
Dassargues, Alain ULg

Scientific conference (1999, March 25)

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See detailModélisation des échanges thermiques et de la circulation d'air dans un lit bactérien
Nicolas, Jacques ULg; Vasel, Jean-Luc ULg

in Revue des Sciences de l'Eau = Journal of Water Science (1990), 3(3), 303-324

The temperature is one of the main parameters governing the biological reactions in a trickling filter. The present model proposes a set of equations applicable for the determination of a temperature ... [more ▼]

The temperature is one of the main parameters governing the biological reactions in a trickling filter. The present model proposes a set of equations applicable for the determination of a temperature profile, and therefore of an average temperature, inside the trickling filter, when the flowrate and the temperature at entry of the liquid, the ambient air conditions (temperature and humidity) and the thermal exchange coefficients of the tower are known. Moreover, the airflow induced by natural draft is also computed when the head loss coefficients in the media and at entry are known. Beside this formulation, the first results of modal fitting on pilot plants are discussed. With few further developments, the method could be useful for the optimization of the operating temperature in a trickling filter which guarantees a sufficient airflow rate in the tower. [less ▲]

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See detailModélisation des Écoulements Hydrologiques Quasi-Tridimensionnels : Problèmes Théoriques et Numériques
Pirotton, Michel ULg

in Tribune de l'Eau (La) (1995), 48(573), 19-26

Detailed reference viewed: 4 (0 ULg)