Implicit large eddy simulation of acoustic loading in supersonic turbulent boundary layers

This paper investigates the accuracy of implicit Large Eddy Simulation in the prediction of acoustic phenomena associated with pressure fluctuations within a supersonic turbulent boundary layer. We assess the accuracy of implicit Large Eddy Simulation against Direct Numerical Simulation and experiments for attached turbulent supersonic flow with zero-pressure gradient, and further analyze and discuss the effects of turbulent boundary layer pressure fluctuations on acoustic loading both at the high and low frequency regimes. The results of high-order variants of the simulations show good agreement with theoretical models, experiments, as well as previously published Direct Numerical Simulations

Voice disorders and mental health in teachers: a cross-sectional nationwide study

International audienceBACKGROUND:Teachers, as professional voice users, are at particular risk of voice disorders. Among contributing factors, stress and psychological tension could play a role but epidemiological data on this problem are scarce. The aim of this study was to evaluate prevalence and cofactors of voice disorders among teachers in the French National Education system, with particular attention paid to the association between voice complaint and psychological status.METHODS:The source data come from an epidemiological postal survey on physical and mental health conducted in a sample of 20,099 adults (in activity or retired) selected at random from the health plan records of the national education system. Overall response rate was 53%. Of the 10,288 respondents, 3,940 were teachers in activity currently giving classes to students. In the sample of those with complete data (n = 3,646), variables associated with voice disorders were investigated using logistic regression models. Studied variables referred to demographic characteristics, socio-professional environment, psychological distress, mental health disorders (DSM-IV), and sick leave.RESULTS:One in two female teachers reported voice disorders (50.0%) compared to one in four males (26.0%). Those who reported voice disorders presented higher level of psychological distress. Sex- and age-adjusted odds ratios [95% confidence interval] were respectively 1.8 [1.5-2.2] for major depressive episode, 1.7 [1.3-2.2] for general anxiety disorder, and 1.6 [1.2-2.2] for phobia. A significant association between voice disorders and sick leave was also demonstrated (1.5 [1.3-1.7]).CONCLUSION:Voice disorders were frequent among French teachers. Associations with psychiatric disorders suggest that a situation may exist which is more complex than simple mechanical failure. Further longitudinal research is needed to clarify the comorbidity between voice and psychological disorders

Do teachers have more health problems? Results from a French cross-sectional survey

BACKGROUND: Although only a few studies have been published on teachers' health, certain ideas are widely accepted, such as for example, the preconceived notion that teachers suffer from an excessively high rate of mental health problems. The objective of this study is to compare teachers' mental and physical health to that of a control group. METHODS: A cross-sectional postal survey was conducted among a sample of 3,679 teachers and 1,817 non-teachers aged 20 to 60 years old. RESULTS: No lifetime prevalence of any psychiatric disorder (with the exception of undifferentiated somatoform disorder in men) or mean scores of psychological distress were found to be significantly higher in teachers. However, multiple analyses, adjusted for all confounding variables, revealed a higher risk of lifetime anxiety disorders in male teachers. On the other hand, significant differences were observed for some physical ailments: a higher lifetime prevalence of rhinopharyngitis/laryngitis in both male and female teachers, of conjunctivitis and lower urinary tract infection in male teachers and of bronchitis, eczema/dermatitis and varicose veins in female teachers. No significant difference was found for chronic pain between the two groups. CONCLUSION: Teachers do not seem to have poorer mental health. However, their physical condition is characterized by a higher prevalence of health problems related to the ENT tract, and to a lesser extent, depending on the gender, to skin, eyes, legs and lower urinary tract

Individual and contextual covariates of burnout: a cross-sectional nationwide study of French teachers

<p>Abstract</p> <p>Background</p> <p>Limited information on the covariates of burnout syndrome in French teachers is available. The aim of this study was to evaluate the relative contributions of individual and contextual factors on the three burnout dimensions: emotional exhaustion, depersonalization, and reduced personal accomplishment.</p> <p>Methods</p> <p>The source data come from an epidemiological postal survey on physical and mental health conducted in 2005 among 20,099 education workers (in activity or retired) selected at random from the health plan records of the national education system. The response rate was 52.4%. Teachers in activity currently giving classes to students who participated in the survey (n = 3,940) were invited to complete a self-administered questionnaire including the Maslach Burnout Inventory. 2,558 teachers provided complete data (64.9%). Variables associated with high emotional exhaustion (highest quartile of score), high depersonalization (highest quartile), and reduced personal accomplishment (lowest quartile) were evaluated using multivariate logistic regression. Studied variables referred to demographic characteristics, socio-professional environment, job dissatisfaction, experienced difficulties at work, and teaching motivations.</p> <p>Results</p> <p>Different variables were associated with each burnout dimension. Female teachers were more susceptible to high emotional exhaustion and reduced personal accomplishment, whereas male teachers were more susceptible to high depersonalization. Elementary school teachers were more susceptible to high emotional exhaustion, but less susceptible to high depersonalization and reduced personal accomplishment than their higher school level counterparts. Experienced difficulties with pupils were associated with all three dimensions. A socio-economically underprivileged school neighbourhood was also related to high emotional exhaustion and high depersonalization.</p> <p>Conclusion</p> <p>Programs to enhance teaching environment might be an interesting approach to try to prevent burnout. It would be useful to take the different dimensions into account in planning the intervention.</p

Preparation of GaSb(100) surfaces by ultraviolet irradiation

International audienceThe preparation of GaSb(100) surfaces by ultraviolet (UV) irradiation, prior to molecular beam epitaxy (MBE) growth, has been investigated. After optimization of the UV irradiation parameters (type of lamp, distance between the lamp and the sample, time exposure), GaSb surfaces present no detectable carbon contamination, a stoichiometry close to the MBE surface one, and a very good morphology. The oxide layers grown an the substrate surface have been analyzed by Auger electron spectroscopy and x-ray photoelectron spectroscopy. Large differences in the oxide composition, resulting from variations of the UV irradiation conditions, have been observed and analyzed. We discuss the experimental results and particularly the carbon desorption, in terms of oxide growth mechanisms and we propose a model of oxide growing in the optimal conditions. (C) 1997 American Vacuum Society

UV AND OZONE CLEANING OF GASB (100) SURFACES PRIOR TO MBE GROWTH

International audienceThe formation of sacrificial oxides by UV-ozone exposure on GaAs and InP is a well established procedure in the preparation of clean substrates for MBE growth. We describe a UV-ozone treatment used to prepare GaSb(100) substrates and report results obtained by Auger (Auger electron spectroscopy) which show that the quality of the so prepared substrates is excellent for MBE (molecular beam epitaxy)