Valeur d'exposition | EPFL Graph Search

La valeur d’exposition est une mesure du domaine de la pollution atmosphérique, de l'eau ou des sols, notamment utilisée dans les réglementations officielles. Valeur limite d'exposition professionnelle (VLEP) Elle représente le niveau maximal de concentration de substances polluantes (par exemple dans l'air), fixé sur la base de connaissances scientifiques, au-delà duquel une exposition de courte durée présente un risque pour la santé humaine ou de dégradation de l'environnement, à partir duquel des mesures d'urgence doivent être prises. Ce terme est très général et ne donne pas de précision sur la durée d'exposition. En France, le calcul des VLEP se fait selon une méthodologie décrite par un document de référence pour l’élaboration de valeurs limites d’exposition à des agents chimiques en milieu professionnel (ANSES, 2017). Ce document définie la VLEP comme la valeur limite des indicateurs biologiques pertinents pour une exposition à une substance chimique donnée. Tou

Pedestrian navigation method and apparatus operative in a dead reckoning mode

Quentin Ladetto

A displacement of a pedestrian is determined from his or her accelerations by detecting accelerations which is substantially non vertical, determining a characteristic feature in the detected accelerations correlated with a step frequency, determining the displacement on the basis of said determined characteristic.The acceleration data can be submitted to waveform analysis to determine an actualized time interval of an occurring feature, such a maximum values, from which it is determined whether the actualized time period falls within determined limit values. The currently detected characteristic feature is then determined as corresponding to a displacement step if the actualized time period falls within said determined limit value.By using non-vertical acceleration measurements, the invention can make it possible to distinguish between forward, backward, left and right stepping movements and take these into account for the navigation.

2004

Controlling motion artefact levels in MR images by suspending data acquisition during periods of head motion

Bogdan Draganski

Purpose: Head movements are a major source of MRI artefacts. Prospective motion correction techniques significantly improve data quality, but strong motion artefacts may remain in the data. We introduce a framework to suspend data acquisition during periods of head motion over a predefined threshold. Methods: Data was acquired with prospective motion correction and an external optical tracking system. A predictor of motion impact was introduced that accounts for the amplitude of the signal acquired at the time of the motion. From this predictor, a threshold was defined to trigger the suspension of data acquisition during periods of motion. The framework was tested on 5 subjects, 2 motion behaviors, and 2 head coils (20 and 64 channels). Results: The best improvements in data quality were obtained for a threshold value of 0, equivalent to suspending the acquisition based on head speed alone, at the cost of a long prolongation of scan time. For threshold values similar to 3.5e(-4), image quality was largely preserved, and prolongation of scan time was minimal. Artefacts occasionally remained with the 64-channel head coil for all threshold values, seemingly due to head movement in the sharp sensitivity profile of this coil. Conclusion: The proposed suspension strategy is more efficient than relying on head speed alone. The threshold for suspension of data acquisition governs the tradeoff between image degradation due to motion and prolonged scan time, and can be tuned by the user according to the desired image quality and participant's tolerability.

2018

Dealing with fuel contaminants in biogas-fed solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) plants: Degradation of catalytic and electro-catalytic active surfaces and related gas purification methods

Hossein Madi, Davide Papurello, Jan Van Herle

Fuel cell and hydrogen technologies are re-gaining momentum in a number of sectors including industrial, tertiary and residential ones. Integrated biogas fuel cell plants in wastewater treatment plants and other bioenergy recovery plants are nowadays on the verge of becoming a clear opportunity for the market entry of high-temperature fuel cells in distributed generation (power production from a few kW to the MW scale). High-temperature fuel cell technologies like molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) are especially fit to operate with carbon fuels due to their (direct or indirect) internal reforming capability. Especially, systems based on SOFC technology show the highest conversion efficiency of gaseous carbon fuels (e.g., natural gas, digester gas, and biomass-derived syngas) into electricity when compared to engines or gas turbines. Also, lower CO2 emissions and ultra-low emissions of atmospheric contaminants (SOx, CO, VOC, especially NOx) are generated per unit of electricity output. Nonetheless, stringent requirements apply regarding fuel purity. The presence of contaminants within the anode fuel stream, even at trace levels (sometimes ppb levels) can reduce the lifetime of key components like the fuel cell stack and reformer. In this work, we review the complex matrix (typology and amount) of different contaminants that is found in different biogas types (anaerobic digestion gas and landfill gas). We analyze the impact of contaminants on the fuel reformer and the SOFC stack to identify the threshold limits of the fuel cell system towards specific contaminants. Finally, technological solutions and related adsorbent materials to remove contaminants in a dedicated clean-up unit upstream of the fuel cell plant are also reviewed. (C) 2017 Elsevier Ltd. All rights reserved.

2017

Hossein Madi, Davide Papurello, Jan Van Herle

2017