Sport utility vehicle | EPFL Graph Search

vignette|alt=Le Tesla Model X est un SUV électrique produit par le constructeur américain Tesla Motors depuis 2015.|Le Tesla Model X est, au sens américain, un crossover à sept places du segment SUV. Un SUV (sigle de l'anglais sport utility vehicle ), aussi appelé tout-terrain de loisir ou véhicule utilitaire sport (VUS) au Canada, est une automobile bicorps familiale polyvalente, dotée d'une carrosserie surélevée et volumineuse, pouvant posséder des capacités de tout-terrain ou de remorquage élevées. À la fin du , le volume de vente de ce segment automobile décolle aux États-Unis, puis en Europe au début du . « Le SUV a remplacé en partie les monospaces dans les achats des Français ; les acheteurs étant avant tout des familles qui ne mettront pas trois ou quatre enfants dans une citadine ». En dépit de leur succès, ils font l’objet de plusieurs controverses, notamment sur les aspects de sécurité, de pollution, d'émissions de gaz à effet de serre et d'encombrement. Ils entraîneraient

Updated braking forces for the assessment of road bridges

João Miguel De Oliveira Durães Alves Martins

Safety assessments of road bridges to braking events combine the braking force, acting along the longitudinal axis of the deck, with a vertical load that accounts for the vertical component of the traffic action. In modern design standards the vertical load models result from probabilistic calibration procedures targeting predefined return periods. On the contrary, the braking force was derived from a deterministic characterization of the vehicle configurations and of the braking process. Therefore, the return period of the braking force is unclear and may not be consistent with that of the vertical load model. Significant deviations from the target return period might lead to either uneconomical decisions, e.g. uncalled-for retrofitting interventions, or to inaccurate structural safety verifications. This thesis presents an original stochastic model to compute site-specific values of the braking force as a function of the return period. The developed stochastic model takes into account the length of the bridge deck and its dynamic properties for vibrations in the longitudinal direction, as well as different sources of randomness related to braking events, all of which comply with real-world measurements, including: - vehicle configurations, resorting to a time-history of crossing vehicles; - driver response times, randomly generated from probability distributions defined in the scope of this project; - deceleration profiles of the vehicles, resampled from catalogues of realistic deceleration profiles. The stochastic model uses Monte Carlo simulation of braking events and computes the maximum of the dynamic response of the bridge to each event. The computed maxima are collected in an empirical distribution function of the braking force. In the end, the model returns the quantile of this distribution that is suitable for safety assessments. This value of braking force is specific to the bridge given properties, to the traffic characteristics, and to the target return period. An additional novelty of this research work is the estimation of a rate of occurrence on motorways of braking events per vehicle-distance travelled. This parameter enables the estimation of the period of time covered by the simulations of braking events as a function of traffic flow and of the total number of braking events simulated. This step is fundamental to determine the value of the braking force that has a given return period. The braking forces returned by the stochastic model show significant dependence on the bridge length, the natural vibration period of the deck in the longitudinal direction, and the number of directions of traffic on the deck. On the contrary, damping ratio, traffic on the fast-lane or on weekends, and an augmentation of traffic in 20% show no substantial influence on the braking force. Moreover, the two motorway locations considered as sources of traffic data, Denges and Monte Ceneri, both in Switzerland, yielded braking forces with similar magnitudes, despite the significant differences in traffic characteristics. Finally, the results compiled served to calibrate an updated braking force that depends explicitly on the parameters found relevant, as well as on the return period so that it can be adopted by different standards even if they enforce different safety targets. This updated expression evidences that the braking forces of current codes tend to be conservative and, hence, can be improved based on the findings of this project.

EPFL2016

Adaptive Highways on a Grid

Hajir Roozbehani

The primary objective of this paper is to introduce the adaptive highways algorithm, a path planning algorithm for vehicles moving on a grid. We consider a workspace that consists of a symmetric grid and a large number of vehicles that move on the grid to accomplish a certain task. Each vehicle is assigned the task of visiting a set of randomly selected locations, which are updated over time. The dynamics of the vehicles are described by a constrained linear double-integrator model. The objective is to find, in real time, a set of trajectories that maximize the average speed of the vehicles while ensuring safety. The trajectory optimization problem is solved locally, whereas a central entity is employed for distribution of information. Safety guarantees are provided through a space reservation mechanism. Several algorithms are presented and compared in terms of performance.

Springer-Verlag Berlin2011

Engineering of chitosan-based derivatives for non-viral gene delivery

Laura Camille Louise Nicolle

Gene therapy offers the possibility to treat or even cure diseases originating from genetic defects by introducing a therapeutic gene in target cells or correcting the initial defective gene. Amongst different options, non-viral vectors rely on the delivery of such genes using vehicles composed of lipids, inorganic nanoparticles or polymers. These systems are designed to protect the genetic material, while efficiently delivering it to the cells of interest. The initial backbone can be complemented with various components to help it overcome the many physiological barriers it may encounter during its journey. Amongst polymers, chitosan is a polysaccharide presenting many advantages for such purpose. Besides its biocompatibility and biodegradability, its potential for functionalization, thanks to numerous primary amines and hydroxyl groups, make it a backbone of choice for the preparation of a polymeric delivery vehicle. This work describes the covalent functionalization of chitosan with other polymers, peptides, and small molecules to later form polymeric nanoparticles condensing therapeutic DNA. Each component brings additional features to the initial system, thus finely tuning it for biological applications. The final system aims at treating liver inherited diseases such as ornithine transcarbamylase deficiency and phenylketonuria.This manuscript first exposes the preparation of a chitosan-based cationic system able to properly condense anionic DNA through electrostatic interactions. Due to its excellent DNA condensation properties, polyethylenimine was grafted to chitosan via a succinyl linker. The first in vitro investigations confirmed the potential of the resulting core system, but in vivo experiments highlighted toxicity coming from the remaining cationic charge on the nanoparticles. In order to better shield this cationic charge, bifunctional polyethylene glycol chains terminated by carboxylic acid moieties were grafted to chitosan amines. The resulting polymer was used to coat the first polymeric system through electrostatic interactions between the carboxylate groups and the remaining free amines of the chitosan-polyethylenimine derivative. The newly formed core-shell complex showed sustained cell viability in vitro and induced higher transfection efficiency of the gene as compared to the core system alone. However, its in vivo evaluation via retrograde intrabiliary infusion did not confirm such results: although transfection efficiency was retained, the core-shell complex did not significantly decrease the toxicity previously reported.The last part of this work includes the decoration of the core-shell system with targeting ligands making possible to perform in vivo assays via intravenous injection, for which the developed polymeric systems did not induce toxicity in preliminary experiments. So far, only a proof-of-concept with folic acid, an anti-cancer targeting ligand, was achieved. To do so, the shell polymer was further functionalized with folic acid-derived polyethylene glycol chains through strain-promoted azide-alkyne cycloaddition. The same strategy shall be applied in the near future with a liver-specific targeting ligand. Lastly, the improvement of the system's cell-penetration features was tackled by the grafting asparagusic acid-derived polyethylene glycol chains following the same strategy than for folic acid.