80 research outputs found
Impact des procédés industriels de traitement sur les propriétés diélectriques des substrats d'alumine utilisés dans les modules de commutation haute tension
Le domaine de l'électronique de puissance est un domaine en pleine expansion dans les applications ferroviaires, avioniques et automobiles. Ce développement est rendu possible grâce à l'arrivée sur le marché de composants de puissance qui n'ont cessé d'évoluer afin d'augmenter leurs performances tout en réduisant leurs tailles. Ces modules de puissance, tels que les modules à IGBT qui peuvent commuter jusqu'à 600 A sous 6500 V, sont constitués d'interrupteurs élémentaires (transistors et diodes) disposés sur un substrat céramique. Les liaisons entre composants sont assurées par des fils de connections et des pistes conductrices disposées sur le substrat. L'ensemble est inséré dans un boitier et encapsulé par un gel de type silicone pour assurer la protection de l'ensemble contre les agressions extérieures. Avant d'être intégrés dans les modules, ces substrats céramiques doivent subir différentes étapes de préparation. Ces étapes sont la découpe, le perçage, le marquage, le traitement de surface (surfaçage ou préparation à la métallisation) et le nettoyage. Ces traitements sont réalisés avec différents moyens technologiques : découpe, marquage ou nettoyage laser, traitements thermiques, nettoyages chimiques... et peuvent apporter des modifications bénéfiques, néfastes ou neutres sur les propriétés diélectriques des substrats. Jusqu'à ce jour, très peu d'études ont été menées pour déterminer les impacts de ces traitements sur le comportement diélectrique des alumines ainsi traitées. Il est donc primordial de connaître ces effets afin d'une part d'identifier les étapes industrielles qui peuvent nuire aux propriétés diélectriques des substrats et d'autre part de tirer à profit les résultats obtenus dans le cadre d'une démarche d'intégration de puissance. Les caractéristiques diélectriques qui ont été évaluées sont la rigidité diélectrique, la conduction électrique volumique et surfacique, les pertes diélectriques et la permittivité. Ainsi une gradation des effets induits par ces traitements, et ceci pour chaque type de traitement, a pu être estimée. Les conclusions de nos expériences ont montré que les propriétés diélectriques dépendant du volume de l'alumine n'étaient affectées que par les traitements thermiques. Sur un plan scientifique, nous nous sommes focalisés sur l'origine de la modification des propriétés électriques à partir des changements microstructuraux engendrés par ces différents traitements. Les résultats expérimentaux obtenus ont permis d'étayer des hypothèses émises lors d'études antérieures menées au laboratoire Laplace. Le mécanisme régissant la conduction à haut champ électrique a pu être ainsi identifié et associé à la taille des grains d'alumine. En ce qui concerne la rupture diélectrique, des informations cruciales concernant son origine ont pu permettre de lever des incertitudes quant au rôle de l'état de surface. Enfin, ce travail a permis d'émettre des propositions de traitements spécifiques qui devraient permettre de réduire la dimension des substrats par le biais d'une réduction des contraintes électriques surfaciques.The power electronics domain, is a domain which is in expansion in the railways, aeronautic and car applications. This development was possible with the apparition on the market of the power component which have evolve for increase theirs performances and decrease theirs sizes. These power modules, like the IGBT (Insulated Gate Base Transistor) could commutate until 600A under 6500V, are constituted of elementary interrupter (transistors and diodes) laid out under a ceramic substrate. The connections between the different components are realized by some wire bonding and metallization laid out on the substrate. The unit is integrated in a case and encapsulated by a silicon gel for realized the protection against the external attack. These treatments are realized with different technology technics: cutting, marking or laser cleaning, thermal treatments, chemical cleaning... and could bring some modifications benefit, harmful or neutral on the dielectrics properties of the substrates. Under this day, few studies were realized for determine the impacts of this treatments on the dielectric behavior of alumina treated. It's so necessary to know this effects in order in the first time identify the industrial steps which could damage the dielectric properties of the substrates and in the second time used this results for power integration. The dielectrics characteristics which were evaluate are the dielectric breakdown, the electric volume and surface conduction, the dielectric losses, and the permittivity. This permit to estimate for each treatment the gradation of the effects generate by this treatments. The conclusions of our experiences have show that the dielectric properties which depend of the volume of alumina were not affect by the thermal treatments. On a scientific point of view, we we are focused on the origin of the modification of the electric properties from to the microstructural changes create by the different treatments. The experiments results obtain, have permit to reinforce some hypothesis generate during previously realized at Laplace laboratory. The mechanism controlling the conduction at high field was identified and associates to the grain size of alumina. Concerning the dielectric breakdown, some capital informations concerning this origin was permit to delete some incertitudes about the part of the surface state. At last, this work was permit to generate some proposition of specific treatments which could permit to reduce the dimensions of substrates by means of a reduction of the electric surface constraints
Short-term effects of amelogenin gene splice products A+4 and A-4 implanted in the exposed rat molar pulp
In order to study the short-time effects of two bioactive low-molecular amelogenins A+4 and A-4, half-moon cavities were prepared in the mesial aspect of the first maxillary molars, and after pulp exposure, agarose beads alone (controls) or beads soaked in A+4 or A-4 (experimental) were implanted into the pulp. After 1, 3 or 7 days, the rats were killed and the teeth studied by immunohistochemistry. Cell proliferation was studied by PCNA labeling, positive at 3 days, but decreasing at day 7 for A+4, whilst constantly high between 3 and 7 days for A-4. The differentiation toward the osteo/odontoblast lineage shown by RP59 labeling was more apparent for A-4 compared with A+4. Osteopontin-positive cells were alike at days 3 and 7 for A-4. In contrast, for A+4, the weak labeling detected at day 3 became stronger at day 7. Dentin sialoprotein (DSP), an in vivo odontoblast marker, was not detectable until day 7 where a few cells became DSP positive after A-4 stimulation, but not for A+4. These results suggest that A +/- 4 promote the proliferation of some pulp cells. Some of them further differentiate into osteoblast-like progenitors, the effects being more precocious for A-4 (day 3) compared with A+4 (day 7). The present data suggest that A +/- 4 promote early recruitment of osteogenic progenitors, and evidence functional differences between A+4 and A-4
Establishing the acute physiological and sleep disruption characteristics of wind farm versus road traffic noise disturbances in sleep: a randomized controlled trial protocol
Advance access publication 6 September 2023Study Objectives: Despite the global expansion of wind farms, effects of wind farm noise (WFN) on sleep remain poorly understood. This protocol details a randomized controlled trial designed to compare the sleep disruption characteristics of WFN versus road traffic noise (RTN). Methods: This study was a prospective, seven night within-subjects randomized controlled in-laboratory polysomnography-based trial. Four groups of adults were recruited from; 15 s events) from sleep by each noise type with acute (20-s) and more sustained (3-min) noise exposures. Secondary analyses will compare dose–response effects of sound pressure level and noise type on EEG K-complex probabilities and quantitative EEG measures, and cardiovascular activation responses. Group effects, self-reported noise sensitivity, and wake versus sleep noise exposure effects will also be examined. Conclusions: This study will help to clarify if wind farm noise has different sleep disruption characteristics compared to road traffic noise.Gorica Micic, Branko Zajamsek, Bastien Lechat, Kristy Hansen, Hannah Scott, Barbara Toson, Tessa Liebich, Claire Dunbar, Duc Phuc Nguyen, Felix Decup, Andrew Vakulin, Nicole Lovato, Leon Lack, Colin Hansen, Dorothy Bruck, Ching Li Chai-Coetzer, Jeremy Mercer, Con Doolan and Peter Catchesid
Gene-enhanced tissue engineering for dental hard tissue regeneration: (2) dentin-pulp and periodontal regeneration
Potential applications for gene-based tissue engineering therapies in the oral and maxillofacial complex include the delivery of growth factors for periodontal regeneration, pulp capping/dentin regeneration, and bone grafting of large osseous defects in dental and craniofacial reconstruction. Part 1 reviewed the principals of gene-enhanced tissue engineering and the techniques of introducing DNA into cells. This manuscript will review recent advances in gene-based therapies for dental hard tissue regeneration, specifically as it pertains to dentin regeneration/pulp capping and periodontal regeneration
One-step partial or complete caries removal and bonding with antibacterial or traditional self-etch adhesives: study protocol for a randomized controlled trial
Vivre la ville. Des habitudes urbaines ?
Decup Benoîte. Vivre la ville. Des habitudes urbaines ?. In: Raison présente, n°102, 2e trimestre 1992. Ville et Société. pp. 71-77
MALADIE CARIEUSE ET DIAGNOSTIC (ASPECT GENERAL ET EVALUATION CLINIQUE D'UN NOUVEAU MOYEN D'AIDE AU DIAGNOSTIC : LE DIAGNODENT*)
MONTROUGE-BUFR Odontol.PARIS5 (920492101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Restaurations postérieures partielles sur la dent pulpée par l'utilisation d'inlays et onlays en céramique
MONTROUGE-BUFR Odontol.PARIS5 (920492101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
La famille et l'architecte : les coups de dés des concepteurs
" La famille dans tous ses espaces
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