Pairing in exotic neutron rich nuclei around the drip line and in the crust of neutron stars

Exotic and drip-line nuclei as well as nuclei immersed in a low density gas of neutrons in the outer crust of neutron stars are systematically investigated with respect to their neutron pairing properties. This is done using Skyrme density-functional and different pairing forces such as a density-dependent contact interaction and a separable form of a finite-range Gogny interaction. Hartree-Fock-Bogoliubov and BCS theories are compared. It is found that neutron pairing is reduced towards the drip line while overcast by strong shell effects. Furthermore resonances in the continuum can have an important effect counterbalancing the tendency of reduction and leading to a persistence of pairing at the drip line. It is also shown that in these systems the difference between HFB and BCS approaches can be qualitatively large

Current Sharing Between Parallel Turns of a Planar Transformer: Prediction and Improvement Using a Circuit Simulation Software

International audienceWith the increase of power needs in low voltage applications, wiring several windings in parallel to sustain large currents becomes common. This operation often has a dangerous impact on transformer reliability because additional currents, we call "circulation currents", create extra losses, generally not taken into account by analytical approaches. Yet, hot points which result from these currents can destroy the component. In planar transformers, windings are made of PCB layers and circulation currents lead to severe unbalance of current sharing between parallel layers. This paper presents an analytical method which enables currents in all layers to be evaluated using only a circuit simulation software such as Pspice® or PSIM®. For a designer, this method is very intuitive and fast compared with the use of fem simulations

Modeling and Design of Passive Planar Components for EMI Filters

Les composants magnétiques en technologie planar répondent aux exigences actuelles de l Electronique de Puissance (EP), à savoir la montée en fréquence de commutation des structures d EP et la réduction du volume des convertisseurs. La première tendance impose des contraintes fortes en termes de compatibilité électromagnétique (CEM) des équipements. Ces dernières doivent être prises en compte par les ingénieurs dès la phase conception des convertisseurs en se basant sur des modèles fiables, peu développés pour les composants planar dans la littérature scientifique. Ce travail de thèse porte ainsi sur la modélisation des composants planar pour applications aux filtres CEM. Différentes méthodes sont développées au cours de cette thèse pour arriver à évaluer de manière fine les éléments parasites des inductances planar de mode commun : capacités parasites et inductances de fuite. Une partie du travail a porté sur la modélisation par circuits équivalents du comportement fréquentiel des inductances de MC. Une approche automatisée, basée sur un algorithme de fitting a ainsi été développée pour élaborer des circuits équivalents fiables et robustes. Des approches analytiques (Décomposition du Champ Electrique) et semi-analytiques (Fonctions de Green) ont aussi été proposées pour évaluer les valeurs des éléments parasites. La dernière partie de la thèse est plus orientée conception, avec la réalisation de deux structures de composants innovantes, la première se basant sur une technique de compensation des capacités parasites à l aide d éléments parasites structuraux et la seconde sur l association de deux noyaux magnétiques, possédant matériaux et géométries différentesThe magnetic components with planar technology join in the current trends in Power Electronics (PE), namely increasing the switching frequency of PE structures and reducing the size of the power converters. The first tendency imposes strong constraints in terms of electromagnetic compatibility of equipments. The latter has to be considered by engineers at the beginning of the design of Power converters on the basis of reliable models, which are not sufficiently developed for planar components in scientific literature. This PhD work thereby focuses on the modeling of planar components for the applications of EMI filters. Different methods are developed during this study in order to accurately evaluate the parasitic elements of planar common-mode chokes: parasitic capacitances and leakage inductances. A part of this dissertation concerns the equivalent circuit modeling of the frequency behavior of CM chokes. An automated approach, based on a fitting algorithm developed for elaborating reliable and robust equivalent circuits. Analytical approaches (Electric Field Decomposition) and semi-analytical (Green s Function) are proposed as well for calculating the values of these parasitic elements. The last part of this dissertation is oriented to conception, with the realization of two structures of innovative components, the first one based on a parasitic capacitance cancellation technique using structural parasitic elements and the second one on the association of two magnetic cores with different materials and geometriesVILLENEUVE D'ASCQ-ECLI (590092307) / SudocSudocFranceF

Automated tool for 3D planar magnetic temperature modelling: application to EE and E/PLT core-based components

International audienceThermal performance of power converters is a key issue for the power integration. Temperatures inside active and passive devices can be determined using thermal models. Modelling the temperature distribution of high frequency magnetic components is quite complex due to diversity of their geometries and used materials. This paper presents a thermal modelling method based on lumped elements thermal network model, applied to planar magnetic components made of EE and E/PLT cores. The 3D model is automatically generated from the component's geometry. The computation enables to obtain 3D temperature distribution inside windings and core of planar transformers or inductors, in steady state or in transient case. The paper details the proposed modelling method as well as the automated tool including the problem definition and the solving process. The obtained temperature distributions are compared with Finite Element simulation results and measurements on different planar transformers

Natural Single-Nucleosome Epi-Polymorphisms in Yeast

Epigenomes commonly refer to the sequence of presence/absence of specific epigenetic marks along eukaryotic chromatin. Complete histone-borne epigenomes have now been described at single-nucleosome resolution from various organisms, tissues, developmental stages, or diseases, yet their intra-species natural variation has never been investigated. We describe here that the epigenomic sequence of histone H3 acetylation at Lysine 14 (H3K14ac) differs greatly between two unrelated strains of the yeast Saccharomyces cerevisiae. Using single-nucleosome chromatin immunoprecipitation and mapping, we interrogated 58,694 nucleosomes and found that 5,442 of them differed in their level of H3K14 acetylation, at a false discovery rate (FDR) of 0.0001. These Single Nucleosome Epi-Polymorphisms (SNEPs) were enriched at regulatory sites and conserved non-coding DNA sequences. Surprisingly, higher acetylation in one strain did not imply higher expression of the relevant gene. However, SNEPs were enriched in genes of high transcriptional variability and one SNEP was associated with the strength of gene activation upon stimulation. Our observations suggest a high level of inter-individual epigenomic variation in natural populations, with essential questions on the origin of this diversity and its relevance to gene x environment interactions

Elaboration sans prototypage du circuit équivalent de transformateurs de type planar

Planar technology is very interesting for transformer used in aeronautical equipment because components are very thin so they can be used into small space. Unfortunately, dimensioning such transformers, when they work at frequencies upper than 100 KHz, is a difficult work because rules and tools conception are not the same as in standard winding transformers. In this thesis, transformers are represented by equivalent circuits and they are identified by impedance measurements. Due to the high number of circuit parameters, optimization of such component will be compromised if parameters computations were based on fem simulations. That is why we have focused this work on analytical computation. The goal is to deduce equivalent circuit parameters with analytical calculation based on physic and geometric caracterisitics. For example, each element of the static leakeage transformer can be deduced using PEEC formulas.Then, problems due to parallel windings, which always appear when transformer current are close to hundred Amperes, are studied. A simple analytical calculation based on one dimensional propagation enable to realize equivalent circuit and Pspice simulations in order to find quickly the best arrangement of windings conductors.In the last part, copper losses in transformers and also in rectangular conductors are studied. Solutions are tested by fem simulations in order to reduce eddy current losses. Multipolar development is finally used for optimizing these losses.La technologie planar est très intéressante pour les transformateurs utilisés dans les équipements aéronautiques car elle mène à des composants minces et utilisables dans des espaces confinés. Malheureusement, le dimensionnement des transformateurs de ce type, lorsqu'ils fonctionnent au-delà de 100 kHz, est un travail aléatoire car les règles et les outils de conception ne sont pas les mêmes que pour un transformateur bobiné classique.Au long de ce mémoire, on apprend à représenter ces composants par un circuit équivalent et à identifier ce circuit équivalent par des mesures d'impédances. Compte tenu du grand nombre de paramètres ajustables, l'optimisation d'un tel transformateur serait compromise s'il fallait compter sur des simulations à éléments finis pour déduire les éléments du circuit équivalent. C'est pourquoi nous essayons de déduire, par des moyens analytiques, les éléments de ce circuit en partant des caractéristiques physiques et géométriques du composant. Le but est atteint pour tous les éléments du transformateur de fuites obtenus à l'aide d'un calcul original exploitant les formules de la méthode PEEC. Nous étudions ensuite les problèmes posés par la mise en parallèle de spires, inévitable lorsqu'on veut faire circuler des centaines d'Ampères. Une approche analytique simple s'avère alors très efficace et, grâce à elle, la meilleure disposition des spires peut être recherchée à l'aide d'un logiciel de simulation de circuits de type PSpice.Enfin, diverses solutions sont envisagées et testées par simulation fem pour réduire les pertes par courants induits dans les transformateurs et dans les conducteurs méplats. Le développement multipolaire du champ magnétique est largement mis à contribution pour mener ces études

Identifying the Magnetic Part of the Equivalent Circuit of n-Winding Transformers

International audienceRepresentation of multi-winding transformers by equivalent circuits has been recently improved and so it is for the identification of its components. In this paper, focus is on magnetic coupling with its related losses. A general method, based on impedance measurements, is used to determinate inductances, coupling ratio and resistances included in these equivalent circuits. Justification for impedance measurements, choice of measured impedances and precautions regarding short-circuit compensation are discussed. For illustration, two components are tested and their equivalent circuits are established

Improved frequency Resolution DFT Eases Teaching FFT Analysis and Provides better Amplitude Accuracy

International audienceFor a signal extension T, DFT and FFT calculate the transform at frequencyies 1/T apart. Duo to this, amplitud of the transform can show more than 36% of discrepancy relatively to exact analytical Fourier Transform and this disagreement looks random

Identifying the Magnetic Part of the Equivalent Circuit of �-Winding Transformers

Abstract—Representation of multiwinding transformers by equivalent circuits has been recently improved, and it is for the identification of components of these circuits. In this paper, the focus is on magnetic coupling with its related losses. A general method, based on external impedance measurements, is followed to determine inductances, coupling ratios, and resistances included in these equivalent circuits. Justification for impedance measurements, choice of measured impedances, and precautions regarding short-circuit compensation are discussed. For illustration, two components are tested, and their equivalent circuits are established. Index Terms—Equivalent circuit, identification, impedance measurement, multiwinding transformer, short-circuit compensation. I

Design of equivalent circuits and characterization strategy for n-input coupled inductors

International audienceAbstract—This paper begins with the definition of ideal coupler, the justification of negative inductance concept and the establishment of various equivalences between circuits. Then, an energy-based recursive method for designing for the equivalent circuit of an n-input magnetic system is presented and the leakage transformer concept is introduced. The obtained circuits allow easy checking of inequalities that inductance matrix elements must satisfy. Advantage is then taken from winding identity and dominant coupling to simplify circuit design. This new knowledge is applied to design equivalent circuits for a three-phase inductor and a three-column six-winding transformer. Finally, key points of a strategy intended to experimental identification of all circuit elements are given