Evaluation de la sécurité du trafic par microsimulation

Actuellement, les analyses de sécurité des réseaux routiers sont essentiellement « réactives », s’efforçant de localiser des points noirs à partir de relevés d’accidents. La présente étude propose de mener des analyses de sécurité « actives » en déterminant un indicateur de sécurité issu de la microsimulation des flux de circulation. Limitée à la problématique des accidents en file, la présente recherche propose un nouvel indicateur de sécurité : la densité d’insécurité UD (pour Unsafety Density). Dans la microsimulation, des modèles de comportement gouvernent la progression des véhicules, en interdisant toute collision. Le paramètre UD proposé se base sur le concept d’une hypothétique collision survenant entre deux véhicules se suivant, en prenant en compte aussi bien la probabilité que la gravité de l’accident. Une étude de cas sur une portion autoroutière fournit des résultats encourageants, démontrant les potentialités de la microsimulation pour l’évaluation de la sécurité routière. Des zones présentant une dangerosité plus importante que le reste du réseau peuvent ainsi être localisées en fonction des conditions de trafic. En complément aux indicateurs classiques de performance, la densité d’insécurité permet une analyse globale, fournissant une aide précieuse lors de la gestion, mais aussi de la conception de réseaux routiers

Géométrie tridimensionnelle des voies de circulation

L’étude des projets routiers se déroule depuis toujours selon un découpage parfaitement défini qui donne lieu à l’étude successive des trois aspects du tracé que sont le plan de situation, le profil en long et le profil en travers. Pris indépendamment, ces trois espaces-plans étroitement liés sont faciles d’accès. Le problème devient plus ardu si on les traite simultanément. Pourtant, une vision globale en trois dimensions est nécessaire pour certains paramètres comme la visibilité, la lisibilité ou l’intégration dans le site, caractéristiques fondamentales dont dépendront la sécurité, la viabilité et la qualité d’une route. La maîtrise de ces questions d’interaction d’espaces-plans est donc indispensable. L’avènement et le développement des logiciels de conception assistée par ordinateur (CAO) ont permis de répondre en partie aux besoins de traitement tridimensionnel, notamment au niveau de la visualisation des projets, formidable outil de communication avec les professionnels et le public. Néanmoins des lacunes subsistent. La présente étude permet la prospection et l’étude théorique de méthodes et principes de base permettant une meilleure maîtrise spatiale du tracé. Sans révolutionner totalement la conception routière, elle apporte un « cahier des charges » pour les logiciels routiers de CAO permettant de mieux appréhender la conception, mais aussi le contrôle des voies de circulation, par exemple lors d’audits de sécurité

PrivateRide: A Privacy-Enhanced Ride-Hailing Service

In the past few years, we have witnessed a rise in the popularity of ride-hailing services (RHSs), an on-line marketplace that enables accredited drivers to use their own cars to drive ride-hailing users. Unlike other transportation services, RHSs raise significant privacy concerns, as providers are able to track the precise mobility patterns of millions of riders worldwide. We present the first survey and analysis of the privacy threats in RHSs. Our analysis exposes high-risk privacy threats that do not occur in conventional taxi services. Therefore, we pro- pose PrivateRide, a privacy-enhancing and practical solu- tion that offers anonymity and location privacy for riders, and protects drivers’ information from harvesting attacks. PrivateRide lowers the high-risk privacy threats in RHSs to a level that is at least as low as that of many taxi services. Using real data-sets from Uber and taxi rides, we show that PrivateRide significantly enhances riders’ privacy, while preserving tangible accuracy in ride matching and fare calculation, with only negligible effects on convenience. Moreover, by using our Android implementation for experimental evaluations, we show that PrivateRide’s overhead during ride setup is negligible. In short, we enable privacy- conscious riders to achieve levels of privacy that are not possible in current RHSs and even in some conventional taxi services, thereby offering a potential business differentiator

Seasonal dynamics and turnover of microbial phosphorusin a permanent grassland

Microbial activity is known to be high under permanent grassland, but consequences for soil phosphorus (P) dynamics and availability are not well understood. Our main objective was to assess the microbial P turnover derived from the seasonal fluctuations in microbial P (measured as hexanol-labile P (Phex) at 13 sampling times during 9months) in a permanent grassland in Switzerland as affected by different P fertilization treatments (P inputs of 0 (NK) or 17kgPha−1year−1 in the form of superphosphate (NPK) or dairy slurry (DS)). Plant P uptake, available inorganic P measured as resin-extractable P (Pres), potential organic P mineralization indicated by acid phosphomonoesterase activity and climatic conditions were also recorded. Despite significant differences in plant P uptake and Pres (NPK > DS > NK), the turnover rate of Phex was similar in all treatments (approximately once per growing season). Thus, the seasonal P flux through Phex was similar to the stock of Phex, which was about 18, 25 and 37kgPha−1 in NK, NPK and DS, respectively, and larger than the corresponding seasonal plant P uptake of 6, 17 and 12kgPha−1. The estimate of Phex turnover based on seasonal dynamics did not confirm previous tracer-based findings of a much faster Phex turnover under low availability of inorganic P, and the magnitude of Phex turnover depended on the number of sampling points taken into account. Fluctuations in Pres and Phex were related to soil moisture and indicated competition between plants and microorganisms for available P

PET/CT Staging Followed by Intensity-Modulated Radiotherapy (IMRT) Improves Treatment Outcome of Locally Advanced Pharyngeal Carcinoma: a matched-pair comparison

BACKGROUND: Impact of non-pharmacological innovations on cancer cure rates is difficult to assess. It remains unclear, whether outcome improves with 2- [18-F]-fluoro-2-deoxyglucose-positron emission tomography and integrated computer tomography (PET/CT) and intensity-modulated radiotherapy (IMRT) for curative treatment of advanced pharyngeal carcinoma. PATIENTS AND METHODS: Forty five patients with stage IVA oro- or hypopharyngeal carcinoma were staged with an integrated PET/CT and treated with definitive chemoradiation with IMRT from 2002 until 2005. To estimate the impact of PET/CT with IMRT on outcome, a case-control analysis on all patients with PET/CT and IMRT was done after matching with eighty six patients treated between 1991 and 2001 without PET/CT and 3D-conformal radiotherapy with respect to gender, age, stage, grade, and tumor location with a ratio of 1:2. Median follow-up was eighteen months (range, 6-49 months) for the PET/CT-IMRT group and twenty eight months (range, 1-168 months) for the controls. RESULTS: PET/CT and treatment with IMRT improved cure rates compared to patients without PET/CT and IMRT. Overall survival of patients with PET/CT and IMRT was 97% and 91% at 1 and 2 years respectively, compared to 74% and 54% for patients without PET/CT or IMRT (p = 0.002). The event-free survival rate of PET/CT-IMRT group was 90% and 80% at 1 and 2 years respectively, compared to 72% and 56% in the control group (p = 0.005). CONCLUSION: PET/CT in combination with IMRT and chemotherapy for pharyngeal carcinoma improve oncological therapy of pharyngeal carcinomas. Long-term follow-up is needed to confirm these findings