Thermal Monitoring of Embankment Dams by Fiber Optics

International audienceInternal erosion is the main cause of failure of earthen hydraulic structures. Moreover, it is often difficult for the operator to detect internal erosion at an early stage. For the last twenty years, leakage detection by thermometry has been developed mainly in Europe. The principle is based on the fact that a leakage through an embankment dam changes its temperature field. In this regard, fiber optics buried in the structures can be used as temperature sensors. Their principal advantage is distributed temperature measurements, at every meter along their length, and over long distances. Indeed, once deployed, optical fiber proves to be an effective mean of probing several kilometers, making it extremely useful for monitoring dikes. Various methods have been developed for analysis of temperature data acquired by these powerful sensors. Thesephysico-statistical and signal processing methods allow to propose a system for "early warning" or for long-term monitoring. Based on the results of several tests at controlled and industrial sites, this presentation will demonstrate the improvement of this surveillance methodology for the safety procedures of embankment dam

Etanchéité par géomembranes des ouvrages pour les eaux de ruissellement routier : vol. 1 guide technique : vol. 2 document complémentaire

This technical guide is intended for consultants, project engineers and project owners involved in the design, building and maintenance of geomembrane waterproofing systems in works for road runoff water. The main types of waterproofing are described, together with the criteria to be taken into account to develop the project, specifications for the components and the wording of guarantees. Recommandations are made for the installation of the waterproofing systems and the organisation of the quality approach, and for their maintenance and rehabilitation. Standard texts are proposed to help in the pre-contact negotiations and the preparation of contract documents.Ce guide technique s'adresse aux bureaux d'études, maîtres d'oeuvres et d'ouvrages concernés par la conception, la réalisation et la maintenance de dispositifs d'étanchéité par géomembrane des ouvrages pour les eaux de ruissellement routier. Les grands types de dispositifs utilisables sont précisés ainsi que les critères à prendre en compte pour rétablir le projet, les spécifications relatives aux différents composants et le libellé des garanties. Des recommandations sont données pour la mise en oeuvre des dispositifs et l'organisation de la démarche qualité ainsi que pour leur entretien et leur réhabilitation. Des textes types sont proposés pour aider à la consultation des entreprises et la préparation des pièces de marché

Thermal Behavior of Parts Made by Direct Metal Laser Sintering

The Direct Metal Laser Sintering (DMLS) manufacturing technique induces thermal stresses in parts. When such parts are used at elevated temperatures, residual stresses are relaxed and the part can suffer significant distortion. This study presents values of geometrical distortion for two laser exposure strategies and for different heat treatment temperatures and durations. Surface and bulk hardness data are provided as well as porosity measurements. At temperatures above 300 the geometrical changes become important. A stabilization treatment. at 600°C can help reduce distortions.Mechanical Engineerin

Thermal behavior of parts made by direct metal laser sintering

The Direct Metal Laser Sintering (DMLS) manufacturing technique induces thermal stresses in parts. When such parts are used at elevated temperatures, residual stresses are relaxed and the part can suffer significant distortion. This study presents values of geometrical distortion for two laser exposure strategies and for different heat treatment temperatures and durations, Surface and bulk hardness data are provided as well as porosity measurements. At temperatures above 300 degrees C, the geometrical changes become important. A stabilization treatment at 600 degrees C can help reduce distortions

Embolic strokes of undetermined source: Prevalence and patient features in the ESUS Global Registry

Background: Recent evidence supports that most non-lacunar cryptogenic strokes are embolic. Accordingly, these strokes have been designated as embolic strokes of undetermined source (ESUS). Aims: We undertook an international survey to characterize the frequency and clinical features of ESUS patients across global regions. Methods: Consecutive patients hospitalized for ischemic stroke were retrospectively surveyed from 19 stroke research centers in 19 different countries to collect patients meeting criteria for ESUS. Results: Of 2144 patients with recent ischemic stroke, 351 (16%, 95% CI 15% to 18%) met ESUS criteria, similar across global regions (range 16% to 21%), and an additional 308 (14%) patients had incomplete evaluation required for ESUS diagnosis. The mean age of ESUS patients (62 years; SD = 15) was significantly lower than the 1793 non-ESUS ischemic stroke patients (68 years, p ≤ 0.001). Excluding patients with atrial fibrillation (n = 590, mean age = 75 years), the mean age of the remaining 1203 non-ESUS ischemic stroke patients was 64 years (p = 0.02 vs. ESUS patients). Among ESUS patients, hypertension, diabetes, and prior stroke were present in 64%, 25%, and 17%, respectively. Median NIHSS score was 4 (interquartile range 2-8). At discharge, 90% of ESUS patients received antiplatelet therapy and 7% received anticoagulation. Conclusions: This cross-sectional global sample of patients with recent ischemic stroke shows that one-sixth met criteria for ESUS, with additional ESUS patients likely among those with incomplete diagnostic investigation. ESUS patients were relatively young with mild strokes. Antiplatelet therapy was the standard antithrombotic therapy for secondary stroke prevention in all global regions