Fouling Detection in Heat Exchangers

This paper deals with the design of a nonlinear observer for the purpose of detecting the fouling phenomenon that commonly occurs in heat exchangers. First, the general model of the heat exchanger is presented in terms of partial differential equations. Next, a simplified lump model is derived that is suitable for the observer design. The observer gains are generated by using appropriate Lyapunov functions, equations and inequalities

Amélioration de l'agrément de conduite via le pilotage du groupe motopropulseur

La transmission à double embrayage a été introduite dans les véhicules afin d'améliorer le confort de conduit, l'économie de conduite et de diminuer le temps de changement de vitesses. La gestion du double embrayage joue un rôle important sur le confort de conduite. L'objectif principal de ce travail concerne alors la synthèse des lois de commande du double embrayage en phase de décollage et lors du changement de vitesses. Le mémoire est structuré de la façon suivante : le premier chapitre propose un état de l'art sur le groupe motopropulseur, la modélisation et la commande du groupe motopropulseur. Le second chapitre s'intéresse à la modélisation du groupe motopropulseur à double embrayage : dans une première partie, un modèle complet à simuler est développé, puis la deuxième partie propose une simplification de modèle en vue de la commande. Le troisième chapitre aborde les lois de commande du double embrayage en utilisant la technique de commande par mode glissant pour les systèmes multivariables. Le quatrième chapitre propose l'utilisation des modèles flous du type Takagi-Sugeno pour la synthèse des lois de commande. Dans une première partie, des lois de commande basées sur un modèle Takagi-Sugeno prenant en compte des incertitudes et des perturbations sont établies. Afin d'améliorer la performance de la loi de commande lors du changement de vitesses supérieures, la deuxième partie présente une loi de commande basée sur un modèle de Takagi-Sugeno incertain et perturbé à commutations. Enfin, des résultats de simulation obtenus en considérant le modèle complet développé dans le chapitre 2 sont donnés.Dual clutch transmission systems were introduced in vehicles to upgrade the driving comfort, the energy economy, and to minimize the shift time. Dual clutch management is a key point when considering driving comfort, particularly during the gearshift. Thus, the main objective of this work is the synthesis of control laws for dual clutch transmission during launch and gearshift. The first chapter presents an overview about vehicle powertrain, modeling and control. The second chapter focuses on modeling the dual clutch transmission. In a first part a complete model for simulation is developed, and in a second part, the model is simplified for the laws control design. The third chapter proposes control laws of the dual clutch using sliding mode control approach for a MIMO system. The fourth chapter deals with the application of state feedback control based on Takagi-Sugeno model. The first part proposes control laws taking into account uncertainties and disturbances. In order to improve the performance of the control law during upshifting, the second part proposes a control law based on a switched Takagi-Sugeno fuzzy model in the presence of parametric uncertainties and disturbances. Finally, control laws are tested in simulation on the complete model developed in Chapter 2.VALENCIENNES-Bib. électronique (596069901) / SudocSudocFranceF

Acidification des eaux de source et saturnisme dans le Massif vosgien.

Les recherches menées à  l'occasion du programme DEFORPA ont montré que les dépôts acides et la sylviculture avaient directement contribué à une acidification des sols et des eaux de surface du Massif vosgien. L'étude de la variation de l'acidité des eaux de source depuis 30 ans a confirmé une acidification progressive de l'eau captée sur les roches les plus pauvres, comme le grès vosgien. Nous avons expérimentalement vérifié que cette acidification a considérablement augmenté la teneur en plomb de l'eau chez les résidents dont les canalisations d'eau potable sont en plomb. Le nombre élevé de cas de saturnisme hydrique observés par les médecins au cours des années 1980 dans le Massif vosgien est attribué directement à  cette acidification des eaux, et indirectement et pour partie à la pollution acide atmosphérique

Finite-time stability and stabilization of time-delay systems

International audienceFinite-time stability and stabilization of retarded-type functional differential equations are developed. First, a theoretical result on finite-time stability inspired by the theory of differential equations, using Lyapunov functionals, is given. As it may appear not easily usable in practice, we show how to obtain finite-time stabilization of linear systems with delays in the input by using an extension of Artstein's model reduction to nonlinear feedback. With this approach, we give an explicit finite-time controller for scalar linear systems and for the chain of integrators with delays in the input

The trophic reliance of methane in the benthic food web: natural versus anthropogenic drivers

It is now widely recognized that biogenic methane can contribute up to 80% of the chironomid biomass in case of hypoxic tropholytic zone. However, several studies have revealed that hypoxic deep conditions can appear more or less abruptly through time, suggesting that the biogenic methane contribution is not the \u27reference\u27 functioning in most lakes. This study aims at identifying the causes of the trophic reliance of methane (\u27TRM\u27) activation, and to understand the environmental conditions that enable the activation of the TRM. Three different lakes (productivity, altitude, water depth, etc.) were investigated using paleolimnological approach. The methodological strategy is built in three steps: (i) the reconstruction of the temporal evolution of methanotroph availability (ancient DNA of methanotroph) and the chironomid paleo-diet (carbon stable isotopes), (ii) the comparison of these dynamics with the histories of climate variability and anthropogenic pressures (pollen analysis) (iii) and the assessment of the environmental conditions (trophic state, oxygen conditions and organic matter accumulation) that allowed this activation. Results reveal very contrasting evolutions suggesting (i) that this pathway is highly driven by human and climate pressures and (ii) that lakes seem to have a various \u27sensibility\u27 facing the activation and the modulation of the TRM

Mathématiques pour l'ingénieur

National audience1. Introduction aux distributions. 2. Optimisation et LMI. 3. Systèmes stochastiques. 4. EDO non linéaires. 5. Calcul des variations. 6. Systèmes à retards. 7. Commande algébrique des EDP. 8. Platitude et algèbre différenetielle

About stability of equilibrium shapes

We discuss the stability of "critical" or "equilibrium" shapes of a shape-dependent energy functional. We analyze a problem arising when looking at the positivity of the second derivative in order to prove that a critical shape is an optimal shape. Indeed, often when positivity -or coercivity- holds, it does for a weaker norm than the norm for which the functional is twice differentiable and local optimality cannot be a priori deduced. We solve this problem for a particular but significant example. We prove "weak-coercivity" of the second derivative uniformly in a "strong" neighborhood of the equilibrium shape

Fingolimod dans la prise en charge de la sclérose en plaques

LILLE2-BU Santé-Recherche (593502101) / SudocSudocFranceF

Stability and stability domains analysis for nonlinear differential-difference equations

International audienceIn this paper, the problem of stability analysis of nonlinear time-delay systems is considered by using comparison-like methods. The main tool is the concept of vector norms which gives a systematic way of defining comparison systems. Examples illustrate the study