A Computational Homogenization Method for the Evaluation of Eddy Current in Nonlinear Soft Magnetic Composites

in Proceeding of the 9th International Symposium on Electric and Magnetic Fields, EMF 2013 (2013, April 23)

The use of the soft magnetic composite (SMC) in electric devices has increased in recent years. These materials made from a metallic powder compacted with a dielectric binder are a good alternative to ... [more ▼]

The use of the soft magnetic composite (SMC) in electric devices has increased in recent years. These materials made from a metallic powder compacted with a dielectric binder are a good alternative to laminated ferromagnetic structures as their granular mesoscale structure allows to significantly reduce the eddy current losses. Furthermore unlike the laminated ferromagnetic structures, SMC exhibit isotropic magnetic properties what makes them good candidates for manufacturing machines with 3D flux paths. The isotropy of the thermal conductivity also allows for a more efficient heat dissipation. The use of classical numerical methods such as the finite element method to study the behavior of SMC is computational very expensive. Indeed a very fine mesh would be required in order to capture fine scale variations i.e. variations at level of metallic grains whence the use of multiscale methods for modelling SMC. The application of multiscale method to study the behaviour of SMC is relatively recent. In (A. Bordianu et al “A Multiscale Approach to Predict Classical Losses in Soft Magnetic Composites”, IEEE Trans. Mag., vol. 48, no. 4, 2012.), the authors used a homogenization technique to compute electrical and magnetic constitutive laws on a representative volume element (RVE). These laws were then used in finite element computations. Herein, the RVE has been chosen to account for the grain- grain contact that can occur in a actual SMC structure due to the compaction process and that can lead to the appearance of macroscale eddy currents. In this paper, we will extend the computational homogenization method success- fully used for modelling the behaviour of laminated ferromagnetic cores in mag- netodynamics (I. Niyonzima et al “Computational Homogenization for Laminated Ferromagnetic Cores in Magnetodynamics”, in Proc. of the 15th Biennal Confer- ence on Electromagnetic Field Computation, 2012) to the case of SMC. The method is based on the heterogeneous multiscale method (HMM) and couples two types of problems: a macroscale problem that captures the slow variations of the overall so- lution and many microscale problems that allow to determine the constitutive laws at the macroscale. The choice of RVE will also be discussed. [less ▲]

A Methodology to Improve the Robustness of Gas Turbine Engine Performance Monitoring Against Sensor Faults

in Journal of Engineering for Gas Turbines and Power (2013), 135(5),

For turbine engine performance monitoring purposes, system identification techniques are often used to adapt a turbine engine simulation model to some measurements performed while the engine is in service ... [more ▼]

For turbine engine performance monitoring purposes, system identification techniques are often used to adapt a turbine engine simulation model to some measurements performed while the engine is in service. Doing so, the simulation model is adapted through a set of so-called health parameters whose values are intended to represent a faithful image of the actual health condition of the engine. For sake of low computational burden, the problem of random errors contaminating the measurements is often considered to be zero-mean, white and Gaussian random variables. However, when a sensor fault occurs, the measurement errors no longer satisfy the Gaussian assumption and the results given by the system identification rapidly become unreliable. The present contribution is dedicated to the development of a diagnosis tool based on a Kalman filter whose structure is slightly modified in order to accommodate sensor malfunctions. The benefit in terms of the diagnostic reliability of the resulting tool is illustrated on several sensor faults that may be encountered on a current turbofan layout. [less ▲]

Subproblem h-Conform Formulation for Accurate Thin Shell Models Between Conducting and Nonconducting Regions

in Proceeding of the 9th International Symposium on Electric and Magnetic Fields, EMF 2013 (2013, April 23)

A subproblem method (SPM) with h-formulation is developed for correcting the inaccuracies near edges and corners that arise from using thin shell (TS) models to replace thin volume regions by surfaces ... [more ▼]

A subproblem method (SPM) with h-formulation is developed for correcting the inaccuracies near edges and corners that arise from using thin shell (TS) models to replace thin volume regions by surfaces. The developed surface-to-volume correction problem is defined as a step of multiple SPs, with inductors and magnetic or conducting regions, some of them being thin. The TS model assumes that the fields in the thin regions are approximated by a priori 1-D analytical distributions along the shell thickness (C. Geuzaine et al., “Dual formulations for the modeling of thin electromagnetic shells using edge elements,” IEEE Trans. Magn., vol. 36, no. 4, pp. 799–802, 2000). Their interior is not meshed and ratherextracted from the studied domain, which is reduced to a zero-thickness double layer with interface conditions (ICs) linked to 1-D analytical distributions that however neglect end and curvature effects. This leads to inaccuracies near edges and corners that increase with the thickness. To cope with these difficulties, the authors have recently proposed a SPM based on the h-formulation for a thin region located between non-conducting regions (Vuong Q. Dang et al., “Subproblem Approach for Thin Shell Dual Finite Element Formulations”, IEEE Trans. Magn., vol. 48, no. 2, pp. 407–410, 2012). The magnetic field h is herein defined in nonconducting regions by means of a magnetic scalar potential , i.e. h = -grad{\phi} , with discontinuities of through the TS. In this paper, the SPM is extended to account for thin regions located between conducting regions or between conducting and nonconducting regions, in the general case of multiply connected regions. In these regions, the potential is not defined anymore on both sides of the TS and the problem has to be expressed in terms of the discontinuities of h, possibly involving on one side only, to be strongly defined via an IC through the TS. In the proposed SP strategy, a reduced problem with only inductors is first solved on a simplified mesh without thin and volume regions. Its solution gives surface sources (SSs) as ICs for added TS regions, and volume sources (VSs) for possible added volume regions. The TS solution is further improved by a volume correction via SSs and VSs that overcome the TS assumptions, respectively suppressing the TS model and adding the volume model. Each SP has its own separate mesh, which increases the computational efficiency. Details on the proposed method will be given in the extended paper, with practical applications. [less ▲]

Coupling heat and salt tracer experiment for the estimation of heat transfer and solute transport parameters

Conference (2013, April 22)

Geothermal energy is a promising source of energy in the context of sustainable development. Therefore, very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or ... [more ▼]

Geothermal energy is a promising source of energy in the context of sustainable development. Therefore, very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy. However, prior to the development of such systems, a feasibility study and an impact study of the system on groundwater ressources are required. Thereliability of such studies is highly dependent on the quality of the estimation of heat transfer parameters. This highlights the necessity of estimating properly such parameters. The objective of this study is to combine the use of heat and salt tracers to estimate simultaneously heat transfer and solute transport parameters in an alluvial aquifer. Additionally, coupling heat and salt tracing experiments is particularly useful for comparing heat transfer and solute transport processes occurring in the subsurface. An experimental field site, located near Liege (Belgium), is equipped with 21 piezometers drilled in the alluvial deposits of the Meuse River. These alluvial deposits are composed of a loess layer (3 m) overlying a sand and gravel layer which constitutes the alluvial aquifer (7 m). The coupled tracing experiment consists in injecting simultaneously heated water and salt in a piezometer and monitoring the evolution of groundwater temperature and salt concentration in a series of control panels set perpendicularly to groundwater flow. This coupled tracing experiment is then simulated using a numerical model. The estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The present study proposes a methodology coupling heat and salt tracing experiment for estimating heat transfer parameters at the field scale. Furthermore, this coupled tracing experiment shows that the comportment of heat and solute in the subsurface presents key differences. [less ▲]

Hacia una caracterizaciòn de los òxidos de hierro empleados durante el periodo Arcaico en la Costa Arreica del Norte de Chile

Conference (2013, April 22)

Los óxidos de hierro han sido intensamente utilizados por los grupos de cazadores recolectores de la Prehistoria desde hace 300 ka. Sin embargo, poco conocidas son las modalidades de extracción. La mina ... [more ▼]

Los óxidos de hierro han sido intensamente utilizados por los grupos de cazadores recolectores de la Prehistoria desde hace 300 ka. Sin embargo, poco conocidas son las modalidades de extracción. La mina de San Ramón15 (Taltal, región de Antofagasta) situada en la costa norte de Chile,representa una evidencia excepcional de la extracción de óxidos de hierro por grupos de pescadores-cazadores-recolectores. Dos fases de extracción han sido determinadas: La primera durante latransiciónPleistoceno-Holoceno (12000-10k BP) y la segunda haciael 4300 BP. Una alta cantidad de percutores y martillos líticosfueron encontrados en el desmonte de extracción. En la mina de San Ramón 15 las rocas ricas en óxidos de hierro se presentan bajo la forma de un filón lenticular de varios metrosintrusivo en granodioritas del Jurasico. El filón, de color negro y extremamente duro, está compuesto principalmente de magnetita y goethita.Una parte del filónfue explotada. Actualmente nuestra investigación se orienta a determinar cuales fueron las características de los óxidos de hierro explotadosy las fases posteriores de su transformación y uso. Para responder a estas preguntas, se desarrolló un protocolo de muestreo y análisis específico. En primer lugar, ha sido fundamental conocer la litología de los filones y de otras formaciones geológicas circundantes ricas en óxidos de hierro. Asimismo, se muestrearon restos de óxidos de hierro tanto en la mina como en los sitios habitacionales del área (conchales) para ser comparados. Los óxidos de hierro (geológicos, arqueológicos, residuos en los objetos) fueron analizados a partir de técnicasfísico-químicas(MEB-EDS, XRD, PIXE) y de caracterización petrográfica. [less ▲]

Use of Life Cycle Assessment to determine the environmental impact of thermochemical conversion routes of lignocellulosic biomass: The gasification step

Poster (2013, April 22)

One-pot controlled synthesis of double thermoresponsive N-vinylcaprolactam-based copolymers with tunable LCSTs

in Polymer Chemistry (2013), 4(8), 2575-2583

N-Vinylcaprolactam (NVCL) was copolymerized statistically for the first time in a controlled manner with hydrophilic N-vinylamide or hydrophobic vinylester monomers in order to precisely tune up and down ... [more ▼]

N-Vinylcaprolactam (NVCL) was copolymerized statistically for the first time in a controlled manner with hydrophilic N-vinylamide or hydrophobic vinylester monomers in order to precisely tune up and down the lower critical solution temperature (LCST) of the resulting copolymers. The incorporation of these segments in complex architectures was also considered. Several narrowly distributed NVCL-based copolymers were prepared by cobalt-mediated radical polymerization (CMRP) using the bis-(acetylacetonato)cobalt(II) complex as a controlling agent and N-methyl-N-vinylacetamide (NMVA), N-vinylacetamide (NVA), vinyl acetate (VAc) or vinyl pivalate (VPi) as comonomers. PNVCL-containing block copolymers having two discrete LCSTs were also synthesized following a one-pot strategy based on the sequential CMRP of NVCL followed by the copolymerization of NMVA with the residual NVCL. Upon gradual heating of aqueous solutions of such double thermoresponsive copolymers, we noticed a transition from free chains to micelles before full dehydration and collapse of the block copolymers. These advances represent a significant step towards the development of a platform based on thermoresponsive PNVCL copolymers with a single phase separation or multistep assembly behaviors. [less ▲]

Observation des acteurs et de la dialectique comme marqueurs du genre dans la pratique scientifique

Conference (2013, April 20)

Avec ce travail, nous proposons de porter une réflexion sémiotique sur le genre dans le domaine de la médecine clinique.

Quelle formation pour un moniteur sportif? Un éclairage scientifique

Conference given outside the academic context (2013)

La Science du coaching s’intéresse notamment à la formation des entraîneurs. Dans le cadre de la journée organisée par l’ADEPS à l’attention des fédérations sportives francophones, cette présentation ... [more ▼]

La Science du coaching s’intéresse notamment à la formation des entraîneurs. Dans le cadre de la journée organisée par l’ADEPS à l’attention des fédérations sportives francophones, cette présentation poursuit trois objectifs : situer la place de la recherche sur la formation des entraîneurs ; décrire les modèles utilisés pour étudier la formation des entraîneurs ; partager quelques résultats marquants. Un constat interpellant souligne l’impérieuse nécessité de promouvoir davantage de coopération entre le domaine de la recherche et les acteurs de terrain. Parmi les principales recommandations, il convient de souligner plusieurs priorités : mettre l’entraîneur au centre de ses apprentissages (responsabilité) ; proposer une combinaison de procédés de formation ; limiter les cours aux notions indispensables et appliquées ; stimuler les occasions de réflexion et d’échange ; tenir compte de ce que l’entraîneur maîtrise déjà ; mettre des ressources à disposition. [less ▲]

Hiérarchisation énonciative, prismes génériques et effet de politisation

Conference (2013, April 19)

Cette présentation aborde la question des genres et de leurs effets interprétatifs par le biais de l’énonciation et, plus particulièrement, par le biais des jeux de hiérarchisation énonciative dont ... [more ▼]

Cette présentation aborde la question des genres et de leurs effets interprétatifs par le biais de l’énonciation et, plus particulièrement, par le biais des jeux de hiérarchisation énonciative dont peuvent faire l’objet divers genres de discours. Nous avons choisi de contraster deux genres de discours a priori très différents (discours politique et littéraire) de manière à dépasser la conception du genre comme un ensemble de données situationnelles ou textuelles, pour y voir un double principe de transfert entre ces deux ensembles. Entre la situation et le texte, le genre (roman, témoignage, harangue, etc.) impose certaines routines communicationnelles ; entre le texte et la situation, c’est d’une autre définition du genre dont on a besoin, celle du genre comme activation d’un parcours au sein d’un espace de possibles interprétatifs, donnant ainsi au texte une orientation argumentative, une consistance évènementielle et une valeur d’acte performatif. Nous pensons que dans cette seconde acception, le genre – ici, l’effet politisant – est susceptible de généralisation, tout comme le sont les genres envisagés plus traditionnellement à partir du pôle de la production. [less ▲]