Application de la méthode semi-Hertzienne pour la simulation du passage d'un TGV sur un appareil de voie

Dans la plupart des simulations en dynamique ferroviaire, le profil de rail est supposé constant le long de la voie. Cette hypothèse ne peut plus être retenue si l'on considère des appareils de voie. Les cœurs à pointes mobiles sont des composants d'appareils de voie conçus pour éviter le franchissement d'une lacune (présente dans les appareils classiques) permettant ainsi un roulement le plus continu possible, recherché dans le cas des grandes vitesses. L'objet des simulations est le calcul des contraintes à l'interface roue-rail lors du franchissement d'une pointe mobile par un TGV. Le problème du contact roue-rail est résolu par la méthode dite "semi-Hertzienne" qui autorise des formes d'empreintes plus réalistes que les ellipses de Hertz. Le principe de la méthode est brièvement présenté. Le cas traité permet de montrer l'avantage de la méthode lorsque l'on s'intéresse aux contraintes de contact

Multibody simulation benchmark for dynamic vehicle-track interaction in switches and crossings: results and method statements

A Benchmark of railway multibody dynamics software application to switches and crossings (S&C) is presented, comparing all major commercially available software and a few independent codes. Two different representative S&C have been implemented, using the Manchester Benchmark passenger vehicle. The final results show that all software offer a reliable and efficient way to understand the kinematic and dynamics forces between the wheels and the track elements. The highest challenges are found when modelling a combination of multiple rails in simultaneous contact with a wheel (check-stock or switch-stock), large longitudinal variations in rail shape (crossings) and high lateral steering forces (diverging cases in tight radius). In those cases, the codes able to account for the exact relative motion of each wheels with respect to each rails independently are the most apt. The most significant variations between software are found in the contact prediction with an influence on the detailed contact tangential and normal forces. The user variability is found to be very small, with the most time-consuming and error prone being the task of handling the input data for the variable rails definition. All software could benefit from improvements to assist the user and ensure higher reliability and efficiency generally

Radiographic manifestations of experimental aluminum toxicity in growing bone

To evaluate the effect of aluminum on growing bone in the presence of normal renal function, the following experiment was performed. Eight littermate pair-fed pigs (5 weeks old) were randomly assigned to one of two study groups: control C, n =4, or aluminum treated Al, n =4. Daily intravenous injections of either aluminum 1.5 mg/kg/day (Al group) or vehicle only (C group) were given during the 8-week duration of the study. The radiographic findings which appeared in the aluminum-treated group and not in the controls consisted of areas of sclerosis in the submetaphyseal regions and the periphery of epiphyses. In addition there was separation of the anterior tibial tubercle. The growth plates did not increase in width despite the presence of osteomalacia and histologic evidence of extensive deposition of aluminum in bone. The area of sclerosis visualized in the radiographs correlated histologically with thickened bony trabeculae. The increased width of these trabeculae is attributable to an increase in primary spongiosum and broadened seams of osteoid.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46782/1/256_2004_Article_BF00356955.pd

Cross-national variations in reported discrimination among people treated for major depression worldwide: The ASPEN/INDIGO international study

Background: No study has so far explored differences in discrimination reported by people with major depressive disorder (MDD) across countries and cultures. Aims: To (a) compare reported discrimination across different countries, and (b) explore the relative weight of individual and contextual factors in explaining levels of reported discrimination in people with MDD. Method: Cross-sectional multisite international survey (34 countries worldwide) of 1082 people with MDD. Experienced and anticipated discrimination were assessed by the Discrimination and Stigma Scale (DISC). Countries were classified according to their rating on the Human Development Index (HDI). Multilevel negative binomial and Poisson models were used. Results: People living in 'very high HDI' countries reported higher discrimination than those in 'medium/low HDI' countries. Variation in reported discrimination across countries was only partially explained by individual-level variables. The contribution of country-level variables was significant for anticipated discrimination only. Conclusions: Contextual factors play an important role in anticipated discrimination. Country-specific interventions should be implemented to prevent discrimination towards people with MDD

Acute mountain sickness.

Acute mountain sickness (AMS) is a clinical syndrome occurring in otherwise healthy normal individuals who ascend rapidly to high altitude. Symptoms develop over a period ofa few hours or days. The usual symptoms include headache, anorexia, nausea, vomiting, lethargy, unsteadiness of gait, undue dyspnoea on moderate exertion and interrupted sleep. AMS is unrelated to physical fitness, sex or age except that young children over two years of age are unduly susceptible. One of the striking features ofAMS is the wide variation in individual susceptibility which is to some extent consistent. Some subjects never experience symptoms at any altitude while others have repeated attacks on ascending to quite modest altitudes. Rapid ascent to altitudes of 2500 to 3000m will produce symptoms in some subjects while after ascent over 23 days to 5000m most subjects will be affected, some to a marked degree. In general, the more rapid the ascent, the higher the altitude reached and the greater the physical exertion involved, the more severe AMS will be. Ifthe subjects stay at the altitude reached there is a tendency for acclimatization to occur and symptoms to remit over 1-7 days

Stigma and discrimination against people with schizophrenia related to medical services.

OBJECTIVE: To investigate whether people with schizophrenia experience discrimination when using health care services. METHODS: A cross-sectional survey in 27 countries in centres affiliated to the INDIGO Research Network, using face-to-face interviews with 777 participants with schizophrenia (62% male and 38% female). We analysed the data related to health issues, including health care, disrespect of mental health staff, and also personal privacy, safety and security, starting a family, pregnancy and childbirth. Discrimination was measured by the Discrimination and Stigma Scale (DISC), which consists of 36 items comprising three sub-scales: positive experienced discrimination; negative experienced discrimination; and anticipated discrimination. RESULTS: More than 17% of patients experienced discrimination when treated for physical health care problems. More than 38% of participants felt disrespected by mental health staff, with higher ratings in the post-communist countries. CONCLUSIONS: Mental health service providers have a key role in decreasing stigma in their provision of health care, and by doing more against stigmatizing and discriminating practices on the therapeutic and organizational level. This will require a change of attitudes and practices among mental and physical health care staff

Wheel-rail contact models in the presence of switches and crossings

The development and implementation of wheel-rail contact models in multibody codes are two active research topics, aiming at improving the accuracy of numerical results and computational efficiency of the dynamics analysis. However, the realism of numerical results is challenged when considering switches and crossings (S&C), where the most adverse wheel-rail contact conditions occur. This paper presents a benchmark study where the performance of the multibody codes MUBODyn, VOCO and VI-Rail are assessed using three case scenarios that involve typical contact conditions observed in S&C. A focused description of the relevant methods to determine the wheel-rail contact forces is presented for each software. The three scenarios considered in this work have been designed to represent typical challenging contact conditions observed in S&C, i.e. conformal contact, contact with a sharp edge, and impact loads. The scenarios proposed in this work are fully described, making them easily reproducible. The agreement between results is discussed in the framework of the methods implemented in each code. This work highlights the impact of wheel-rail contact methods on the results as well as on the computational efficiency of the multibody codes.info:eu-repo/semantics/publishedVersio