Caractérisation électrique haute fréquence d'un fil de cuivre possédant un revêtement de Nickel

International audience Cette étude présente l'évolution des caractéristiques d'un fil de cuivre capable de travailler à 500◦C possédant un revêtement céramique, déposé sur une couche de Nickel servant de barrière de diffusion pour la réalisation de bobinage de machines électriques capables de fonctionner à Hautes Températures (500◦C) avec une alimentation MLI. Les caractéristiques en fréquence et en température de ce fil sont indispensables pour sa mise en œuvre au sein d'une machine électrique. Cette étude présente une approche analytique des phénomènes intervenant dans ce type de conducteur lorsque la fréquence des signaux augmente. Cette approche analytique repose sur l'étude d'un fil seul.  </div

Unexpected pathways toward college graduation

This study examines the dispositions and experiences of support of college students associated with unexpected pathways toward college graduation. The final sample was drawn from a national sample of 3,998 youths who participated in a longitudinal project. Using the k-nearest neighbors’ algorithm, we created four groups based on the Québec High School Average and the College Graduation status four years after admission (Unexpected Graduates; Expected Dropouts; Unexpected Dropouts; Expected Graduates). Compared to ED, UG showed lower aggressive behaviors and attentional problems and higher participation in institutional or targeted support measures in college. They were also more likely to have attended a private high school. Compared to EG, UD showed lower academic behaviors and motivation, lower perceptions of teaching quality and support, and lower economic capital and support from family. They were also more likely to enrol in a technical college program and less likely to have attended a private high school

Le profil psychosocial de couples consultant à une clinique de fertilité

L'objectif de la présente étude est de tracer le profil psychosocial de couples consultant à une clinique de fertilité. Plus spécifiquement, il s'agit (a) de comparer le statut psychosocial de sujets consultant à une clinique de fertilité à celui de sujets normaux ou d'individus souffrant de problèmes psychologiques, (b) de déterminer s'il existe des différences de profil entre les hommes et les femmes consultant pour un problème de fertilité" et (c) d'évaluer s'il est possible de prédire la nature du profil psychosocial des sujets à partir de diverses caractéristiques sociodémographiques et médicales. L'échantillon se compose de 30 couples qui consultent un spécialiste de la clinique de fertilité d'un hôpital de la région de Montréal. L'analyse des résultats démontre que le profil psychosocial des sujets consultant à une clinique de fertilité se situe à mi-chemin entre celui de sujets normaux et celui d'individus souffrant de problèmes psychologiques. Le statut psychologique des hommes et des femmes consultant à une clinique de fertilité diffère sur trois variables: dépression, estime de soi et stress. Enfin, les analyses de régression multiple ont permis d'identifier plusieurs caractéristiques médicales reliées à l'ampleur des difficultés psychosociales rapportées par les sujets infertiles. Le profil psychosocial de couples consultant à une clinique de fertilitéThe objective of this study is to draw the psychosocial profile of couples who consult fertility clinics. More specifically, it consists of a) comparing the psychosocial status of subjects who seek fertility consultation with that of normal subjects or individuals at grips with psychological problems; b) determining whether there are profile differences between men and women who seek fertility consultation; and c) assessing whether it is possible to predict the nature of the psychosocial profile of the subjects from various sociodemographic and medical characteristics. The sampling includes 30 couples who are consulting a specialist in a fertility clinic belonging to a Montréal-area hospital. Analysis of results shows that the psychosocial profile of subjects consulting a fertility clinic is midway between that or normal subjects and that of individuals suffering of psychological problems. The spy-chological status of men and women consulting a fertility clinic is different according to three variables: depression, self-esteem and stress. Finally, multiple regression analysis has allowed the author to identify several medical characteristics linked to the extent of the psychosocial difficulties experienced by the infertile subjects

Mothers’ and fathers’ autonomy-supportive and controlling behaviors : an analysis of interparental contributions

Objective. The goal of this study was to examine how mothers and fathers contribute to each other’s autonomy supportive and controlling behaviors toward their child. Design. The participants were heterosexual parental dyads from two prospective studies (Study 1, n =289; Study 2, n = 202). Mothers and fathers completed questionnaires assessing their autonomy supportive and controlling behaviors toward their adolescent child. Results. In both studies, results from structural equation modeling revealed reciprocal partner effects where mothers’ autonomy support at Time 1 predicted fathers’ autonomy support at Time 2, and fathers’ autonomy support at Time 1 predicted mothers’ autonomy support at Time 2. Reciprocal partner effects were also observed for controlling behaviors. These reciprocal relations were not statistically different across mothers and fathers. Conclusions. These results provide support for interparental contributions regarding autonomy supportive and controlling parenting behaviors. Mothers and fathers should thus be aware that their parenting behaviors can be influenced by each other, including both positive and negative parenting behavior

Leidenfrost drops on a heated liquid pool

We show that a volatile liquid drop placed at the surface of a non-volatile liquid pool warmer than the boiling point of the drop can experience a Leidenfrost effect even for vanishingly small superheats. Such an observation points to the importance of the substrate roughness, negligible in the case considered here, in determining the threshold Leidenfrost temperature. A theoretical model based on the one proposed by Sobac et al. [Phys. Rev. E 90, 053011 (2014)] is developed in order to rationalize the experimental data. The shapes of the drop and of the substrate are analyzed. The model notably provides scalings for the vapor film thickness. For small drops, these scalings appear to be identical to the case of a Leidenfrost drop on a solid substrate. For large drops, in contrast, they are different and no evidence of chimney formation has been observed either experimentally or theoretically in the range of drop sizes considered in this study. Concerning the evaporation dynamics, the radius is shown to decrease linearly with time whatever the drop size, which differs from the case of a Leidenfrost drop on a solid substrate. For high superheats, the characteristic lifetime of the drops versus the superheat follows a scaling law that is derived from the model but, at low superheats, it deviates from this scaling by rather saturating

Bobinage à faible impact environnemental

L'étude d'un nouveau fil émaillé dont le procédé d'élaboration réduit fortement son impact environnemental est présentée. Cette étude est associée à celle d'un vernis dont la quantité de Composés Organiques Volatiles (COV) est très faible. Les nombreux essais tant mécaniques qu'électriques montrent que ce fil est aussi performant que le fil émaillé classique. Sur certaine caractéristique comme le PDIV il est même meilleur. Enfin la problématique de l'imprégnation, souvent faite sous vide et pression pour être performante, est abordée. L'emploi d'un vernis monomère réactif et d'une pré-gélification par lampe UV, permet de réduire fortement la perte de masse et d'améliorer toutes tes caractéristiques mécaniques exigée pour le fonctionnement des moteurs en milieu hostile

Conception d'un prototype de machine Ultra-Haute Température (500°C)

International audienceLe papier présente les problématiques et les solutions adoptées pour construire le premier prototype d'un moteur électrique très compact doté de bobinages inorganiques capables de travailler en permanence à une température interne de l'ordre de 500°C. L'analyse des verrous technologiques qui empêchent de faire des machines très compactes à fort gradient de température interne montre que le principal verrou technologique est lié à la nature organique du Système d'Isolation Electrique (SIE). Le prototype de machine synchrone est construit autour de bobines inorganiques rigides montées sur les dents du stator. Ces bobines, testées à 500°C sont capables de résister aux surtensions provoquées par les fronts raides des convertisseurs MLI actuels

Correlation between the plasma characteristics and the surface ‎chemistry of plasma-treated polymers through partial least ‎squares analysis

We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy

Adjustment trajectories during the college transition : types, personal and family antecedents, and academic outcomes

This longitudinal study was aimed to describe and understand student adjustment trajectories during the college transition. Participants came from a large random sample of Quebec high school students. They completed a multidimensional measure of adjustment at two times before entering college and at two other times after college admission. Group-based trajectory analysis showed decreased adjustment for 6% (social adjustment) to 66.1% (academic adjustment) of students over this period, versus improved adjustment for 4.5% (social adjustment) to 11.6% (emotional and academic adjustment). All changes were linear, suggesting progressive changes from Secondary 4 to the second year of college. Multivariate and contingency analyses showed that personal anxiety, academic success, and attention problems in high school were significant determinants for adjustment trajectories, and that these trajectories were subsequently related to perseverance and college graduation

Simulation électromécanique 3D d'un conducteur 1+6 avec prise en compte des résistances de contact inter-brins

Dans cet article, nous proposons une méthode d'analyse par éléments finis 3D, pour prédire le comportement électrique d'un conducteur (1+6). La performance d'un conducteur dépend de la nature du matériau, de son état métallurgique mais aussi de la résistance électrique des zones de contact inter-fils. Dans ce travail, une première analyse mécanique permet de reproduire le processus de câblage pour déterminer les déformations élasto-plastiques des fils, la forme et les forces de pressions dans les interfaces de contact. Une seconde analyse électrique est menée pour déterminer la résistance électrique du conducteur déformé. La résistance de contact tangentielle et radiale est alors prise en compte. </p