Glissière de sécurité | EPFL Graph Search

Une glissière de sécurité, parfois appelée « rail de sécurité » ou « garde-fou » (ou encore « bertrame » en Suisse), est une barrière métallique, en béton, ou en bois, disposée le long d'une voie de circulation routière pour amoindrir la gravité des accidents, en évitant notamment les sorties de route. Fonction La glissière est rigide (béton) ou déformable (métallique, et, plus rarement, faite de câbles) pour, en cas d'accident, amortir le choc et ne pas renvoyer le véhicule dans le sens inverse (sur une route à double voie) et pour qu'il ne rebondisse pas vers la voie de gauche sur les autoroutes. Les glissières de sécurité sont surtout utilisées :

comme délimitation du « refuge » ou « terre-plein » central sur les routes à double chaussées ;
comme protection sur les ponts, échangeurs et leurs accès ;
sur les routes de montagne (pente, verglas, virages, lacets) ;
en bordure d'autoroute et de voie rapide à cause de la vitesse élevée des véhicules.

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Theoretical study of electronic transport in TCV ELMy H-mode

Gaël Induni

High-confinement mode (H-mode) is a promising reference scenario for ITER. But we are still facing major issues because of instabilities. They expel periodically some of the energy, which can damage the device. These instabilities are called the edge localized modes (ELM) and are not yet fully theoretically understood. The present work is a study on the profiles evolution in between ELMs and on the ELM effects. This may help to have a better understanding of the conditions before the ELM. We use the simulations as theoretical tool. For the purpose of the simulations, we build an H-mode χ e profile according to a standard L-mode one that we truncate at the edge to create a transport barrier. This gives a good agreement with the experimental data. Several scaling laws were successfully used. The first one is the energy confinement time scaling which was used for the thermal diffusivity to scale the temperature profile. A scaling between the core and pedestal energies was found recently. It was used to compute the pedestal χ e to scale the temperature pedestal, which was successful. Finally, we used a scaling for transport barriers which links the density gradient length to that of the temperature to compute the density in the pedestal. It was already found to be good in TCV electron internal transport barriers and in ASDEX Upgrade H-mode pedestals. Looking at the MHD stability parameters, it was found that for our reference case, ELMs are not likely to be triggered by the time evolution of the pressure gradient and the current density profiles in our model, as these are only varying significantly during the first millisecond after the crash, and are almost constant during the long remaining time until the next crash. Studying different cases, we investigate the behavior of the plasma when replacing the edge heating by central one to observe the influence of the heating profile, but no significant difference was found, neither in the MHD stability parameters. Further we change the particle diffusion coefficient to compare the dynamic behavior of the density. Slowing down the density dynamic behavior also slows down the pressure one, this can be seen on the MHD stability parameters. We also vary the ELM period to compare to the change due to the variation of the particle diffusivity. It was found that there may be a sort of relation between the particle diffusivity and the ELM period at least for the density, since both cases change the density recovery time with respect to the ELM period. A last case considered is doubling the radial ELM interaction range. This is done in order to observe the difference to the reference simulation that takes the density top of pedestal as ELM range, and to compare the spatial range influenced by the MHD activity and the one by the transport improvement. It was found that the MHD stability parameters in the pedestal exhibit a different behavior with the pressure gradient starting to increase very fast.

2011

Working with extreme urban density: Hong Kong. A prototype of mixed-use building in Hong Kong

Wing-Chung Cheung, Joana Varela

Urban sprawl, a solution to house fast-growing metropolitan populations, dilutes the substance of cities and generates extensive uniformly built fabrics lacking structural poles of attraction. Hong Kong is one of the seldom exceptions of this general tendency. Constrained by its geographic conditions and its historical background, the city has remained compact and reached elevated levels of density. This extreme concentration of population and its impact upon urban form constitute an excellent laboratory to experiment new forms of density. Furthermore, Hong Kong becomes even more relevant as it is a development model for its emerging Chinese neighbours. Our intention is to maintain and enhance density in the urbanized areas and to improve the living environment in the denser cores of the city. The main challenges are to provide more public spaces and to ensure equal light and spatial qualities for everyone. To achieve this objective, the project must find an architectural solution that proposes a new interpretation of the standard Hong Kong tower. Firstly, we would like to avoid the urban barrier created by the common podium typology, by making the latter more permeable and public. Secondly, the density of Hong Kong encourages the existence of a mixed-use building, combining various functions and allowing for the cohabitation of public and private programs. Consequently the various programs can be located optimally in the building according to factors such as light, view, orientation and connection.

2008

Modeling consideration for electric vehicles and plug-in electric vehicles in car renewal

Maurin Baillif, Michel Bierlaire, Matthieu Marie Cochon de Lapparent, Anna Fernández Antolín

We propose a behaviorally sound model capable of simulating choice set generation for car renewal. It appears at an upper layer of a choice model of a new car. Our model sheds light on potential latent demand for electric cars. We develop a hierarchical latent variable approach to model consideration for electric and plug-in hybrid electric vehicles in car renewal. It drives the observed outcomes that regard how much an individual would account or not for electric cars when planning to renew one. We model it as a latent factor that is defined as a linear combination of attitudes and perceptions. In our application, respondents are asked to whether they would consider or not a 100% electric and a plug-in hybrid electric vehicle. Attitudes and perceptions are also latent factors. These are additional variables that we model. They here are of three types: range anxiety, environmental concerns, and perception about compatibility of use in everyday life. They are measured through a series of questions that concern barriers and motivations to adoption of electric cars. For each of them, respondents are asked to rate on a 5 points Likert scale. We use data from the 2012 Nissan-Renault Alliance survey for application. It covers 5 European countries (France, Germany, Italia, Spain, UK). The sample size is about 5000 observations. In addition to observed outcomes that we model, we have information about individuals, structures of their households, the current cars they own and the way they use them (driven mileages). The measurement model takes the form of a mixed multivariate ordered Logit model. We discuss identification conditions to uncover the structural parameters of our system. It is estimated by maximization of the associated simulated log-likelihood function. Estimates live up to our expectations and are in line with existing literature.