Dynamique du niveau de motorisation automobile des ménages français

ED EPSCe document propose un modèle catégoriel probit ordonné dynamique avec hétérogénéité pour analyser le degré de motorisation automobile choisi par les ménages en France. Trois états d'équipement sont considérés : la non, mono, et multi motorisation. L'estimation utilise les observations pondérées du panel Parc Auto 1999-2001. Nous situons notre étude dans le cadre statistique bayésien et résolvons le modèle par la méthode de l'échantillonneur de Gibbs. Nous traitons par ailleurs l'approximation des conditions initiales avec une méthode inspirée de HECKMAN (1981), et de l'estimateur de BLUNDELL et SMITH (1991). En spécifiant un modèle latent autoregressif simple, nous adaptons quelques méthodes issues des modèles linéaires dynamiques pour interpréter notre modèle de choix ordonnés. Notamment, nous évaluons pour des ménages moyens les effets à court et long terme d'un changement résidentiel vers une zone francilienne sur leurs probabilités de motorisation, ainsi que les élasticités au revenu de court et long terme des trois probabilités d'équipement

Addiction à l'usage de l'automobile en France et mesures d'élasticités

ED EPSDans ce papier, nous menons une étude du comportement d'usage des automobiles, et nous intéressons au kilométrage annuel parcouru par les ménages, i.e. leur « automobilité ». Pour caractériser cette consommation individuelle de kilomètres, le modèle d'addiction rationnelle de BECKER a été déployé sur le panel 1999-2001 de l'enquête française « Parc Automobile ». Les résultats font tout d'abord apparaître qu'on ne peut réfuter l'hypothèse microéconomique d'addiction concernant l'usage de la voiture. Quelques valeurs d'élasticité du kilométrage au prix des carburants dans un premier temps, puis au revenu des ménages ensuite, sont reportées, avec des résultats tout à fait plausibles. Puis, un éclairage est porté sur les différences géographiques, en confrontant les ménages des trois aires franciliennes et la Province, et en simulant l'effet d'un changement résidentiel sur leur mobilité. Enfin, nous voyons dans quelle mesure un changement des caractéristiques de motorisation (nombre d'automobiles, de permis, transitions ‘essence-diesel') affecte l'automobilité des ménages français

Evidence for an endogenous rebound effect impacting long-run car use elasticity to fuel price

This paper presents a structural equation model of household fleet fuel efficiency and car use. It allows to weigh the contribution of car equipment changes and car use adjustments to the price elasticity of household demand for fuel. This model is implemented using a panel dataset of 322 households that were present in each annual wave of the French Car Fleet survey from 1999 to 2007. The longitudinal dimension of this dataset enables to assess the short and long-run adjustments at the household level over a period of fuel price increase. The estimated price elasticities of the demand for fuel are fully consistent with the literature: -0.30 in the short run and -0.76 in the long run. Regarding car use elasticities, accounting for an endogenous rebound effect allowed a striking finding: the sensitivity of household car use to fuel price changes is lower on the long run than on the short run. This paper thus not only provides the latest estimations of elasticities for France, in the early 2000's, it also shows that, on the long run, French households have managed to mitigate the impact of increasing fuel prices on their car mobility by using more fuel efficient cars.Elasticity, Fuel Price, Rebound effect, Energy consumption, Energy efficiency, Car use, Household, Panel data

Addiction to car use and dynamic elasticity measures in France

This article presents a microeconometric analysis of the annual mileage travelled by French households with their personal cars, defining their automobility. To feature car use dependence, the rational addiction model of Becker et al. (1994) is applied on a panel dataset, drawn from the French "Car Fleet" survey over the period 1999-2001. Importantly, the estimates show that the assumption of addiction to car use cannot be rejected. Furthermore, the model yields realistic kilometric-price and income elasticities of household automobility, for both the short and the long runs.Transportation ; Car use ; Consumption ; Addiction ; Panel ; GMM

Computation of 2D vibroacoustic waves dispersion for optimizing acoustic power flow in interaction with adaptive metacomposites

International audienceThis paper presents an integrated methodology for optimizing vibroacoustic energy flow in interaction between an adaptive metacomposite made of periodically distributed shunted piezoelectric material glued onto passive plate and open acoustic domain. The computation of interacting Floquet-Bloch propagators is also used to optimize vibroacoustic behavior. The main purpose of this work is first to propose a numerical methodology to compute the fluid-structure multi-modal wave dispersions. In a second step, optimization of electric circuit is used to control the acoustic power flow. 3D standard computation is used to confirm the efficiency of the designed metacomposite in terms of acoustic emissivity and absorption

Long term dynamics of inequalities between French households concerning automobile

International audienceFor each quartile of income per household or per consumption unit, annual time-series have been estimated from panel surveys, with annual waves of observations from 1974 to 2007: INSEE2 Households' "Conjoncture" survey from 1974 to 1994 ; panel "Parc-Auto"3 Sofres4 since mid-80's. In these data sources, household behaviour is described through ; car ownership (percentage of households with at least one car, of which percentage of multi-car households, average number of cars per adult over 18, which is the minimum age for driving license in France) ; car use (annual mileage per household or per car). The repeated sample structure of data has been used for improving the accuracy of time-series of variables highly correlated for subsequent years [Cochran, 1977]. In mid-70's, car ownership and use were quite low for the poorest income quartile, but the difference has much decreased with all the three higher income groups, which are more homogeneous. Thus, multi-car ownership, which is mainly structured by geographic and demographic determinants, has slowed down -but not reversed- the social diffusion of automobile. As the curves representing car ownership (number of cars per adult) and car use (annual mileage per household) seem to become quite horizontal during the most recent period, logistic curves have been estimated according to time, then to real income. For each quartile of the distribution of households by income per consumption unit, saturation thresholds are estimated, as well as the date or the point of inflection. Follows a discussion on the legitimacy of pooling the data. The relationship between temporal elasticities (for each quartile) and cross-sectional income elasticities, which can be considered as a measurement of inequality at each point in time, will be discussed [Gardes and Madre, 2005]

Are we heading towards a reversal of the trend for ever-greater mobility?

In most industrialised countries, it can be seen that urban mobility and car traffic have stagnated since the early 2000s. In France, the report on traffic conducted by the National Transport Accounts Commission shows a similar break in the trend, which was confirmed by household travel surveys (EMDs) in most major cities, including Lille, Lyon and Strasbourg, and later by the National Transport and Travel Survey (ENTD), which shows that the trend can be attributed primarily to people living in large urban areas and provides an overall view of mobility: trips have become less frequent (with unbroken workdays) and less exclusively taken by car (as more young adults adopt multimodal behaviours), and car ownership is decreasing in the centre of greater Paris, as, for that matter, in the centre of London. Does this levelling-off of traffic suggest that the saturation point is near (with a decoupling of traffic and income trends in the most densely populated areas or above a certain standard of living) or, rather, a cancelling out of opposite trends (continued growth in rural and suburban areas and decline amongst residents of the most densely populated areas)? Is this a structural phenomenon (population ageing, etc.) or a cyclical one linked to rising and volatile fuel prices and the recession? We shall explore these issues in the light of data collected in France, supplemented by selected data from other developed countries, and then move on to a comparison with a number of Mexican cities in order to consider the extent to which, and in what timeframe, these trends could spread southward to the emerging economies

The thirty gigahertz instrument receiver for the QUIJOTE experiment: preliminary polarization measurements and systematic-error analysis

This paper presents preliminary polarization measurements and systematic-error characterization of the Thirty Gigahertz Instrument receiver developed for the QUIJOTE experiment. The instrument has been designed to measure the polarization of Cosmic Microwave Background radiation from the sky, obtaining the Q, U, and I Stokes parameters of the incoming signal simultaneously. Two kinds of linearly polarized input signals have been used as excitations in the polarimeter measurement tests in the laboratory; these show consistent results in terms of the Stokes parameters obtained. A measurement-based systematic-error characterization technique has been used in order to determine the possible sources of instrumental errors and to assist in the polarimeter calibration process.The authors would like to thank Spanish Ministry for Economy and Competitiveness for the financial support provided under the CONSOLIDER-INGENIO 2010 program under the reference CSD2010-00064 and the project under reference AYA2012-39475-C02-01

Antibodies against the flotillin-1/2 complex in patients with multiple sclerosis

Lleixa and Caballero-avila et al. report that antibodies targeting the flotillin-1/2 complex are present in a subgroup of patients with multiple sclerosis. Further studies are needed to understand the clinical and pathological relevance of anti-flotillin-1/2 autoantibodies in multiple sclerosis. Multiple sclerosis is a tissue-specific autoimmune disease of the central nervous system in which the antigen(s) remains elusive. Antibodies targeting the flotillin-1/2 complex have been described in 1-2% of the patients in a recent study. Other candidate antigens as anoctamin-2 or neurofascin-155 have been previously described in multiple sclerosis patients, although their clinical relevance remains uncertain. Our study aims to analyse the frequency and clinical relevance of antibodies against neurofascin-155, anoctamin-2 and flotillin-1/2 complex in multiple sclerosis. Serum (n = 252) and CSF (n = 50) samples from 282 multiple sclerosis patients were included in the study. The control group was composed of 260 serum samples (71 healthy donors and 189 with other neuroinflammatory disorders). Anti-flotillin-1/2, anti-anoctamin-2 and anti-neurofascin-155 antibodies were tested by cell-based assays using transfected cells. We identified six multiple sclerosis patients with antibodies against the flotillin-1/2 complex (2.1%) and one multiple sclerosis patient with antibodies against anoctamin-2 (0.35%). All multiple sclerosis patients were negative for anti-neurofascin-155 antibodies. Three of the anti-flotillin-1/2 positive patients showed anti-flotillin-1/2 positivity in other serum samples extracted at different moments of their disease. Immunoglobulin G subclasses of anti-flotillin-1/2 antibodies were predominantly one and three. We confirm that antibodies targeting the flotillin-1/2 complex are present in a subgroup of patients with multiple sclerosis. Further studies are needed to understand the clinical and pathological relevance of anti-flotillin-1/2 autoantibodies in multiple sclerosis

The Effects of Temperature on Clot Microstructure and Strength in Healthy Volunteers

BACKGROUND: Anesthesia, critical illness, and trauma are known to alter thermoregulation, which can potentially affect coagulation and clinical outcome. This in vitro preclinical study explores the relationship between temperature change and hemostasis using a recently validated viscoelastic technique. We hypothesize that temperature change will cause significant alterations in the microstructural properties of clot. METHODS: We used a novel viscoelastic technique to identify the gel point of the blood. The gel point identifies the transition of the blood from a viscoelastic liquid to a viscoelastic solid state. Furthermore, identification of the gel point provides 3 related biomarkers: the elastic modulus at the gel point, which is a measure of clot elasticity; the time to the gel point (TGP), which is a measure of the time required to form the clot; and the fractal dimension of the clot at the gel point, df, which quantifies the microstructure of the clot. The gel point measurements were performed in vitro on whole blood samples from 136 healthy volunteers over a temperature range of 27°C to 43°C. RESULTS: There was a significant negative correlation between increases in temperature, from 27°C to 43°C, and TGP (r = −0.641, P 37°C. CONCLUSIONS: This study demonstrates that the gel point technique can identify alterations in clot microstructure because of changes in temperature. This was demonstrated in slower-forming clots with less structural complexity as temperature is decreased. We also found that significant changes in clot microstructure occurred when the temperature was ≤32°C