University of Marne-la-Vallée

About: University of Marne-la-Vallée is a based out in . It is known for research contribution in the topics: Estimator & Context (language use). The organization has 831 authors who have published 1855 publications receiving 55316 citations.

Seismic vulnerability assessment at urban scale: Case of Algerian buildings

Abstract: The main purpose of risk reduction methodological and operational approaches is to protect lives and properties against the impact of natural or industrial disaster. Although it is unrealistic to expect to live in a risk free environment, it is possible to reduce this risk through appropriate prediction and management strategies. This work presents an integrated framework for seismic damage assessment at urban scale in Algeria. Its main objective is the proposal of simplified methodological and operational approaches to assess urban vulnerability and socio-economic losses. It relies on the performance of probable seismic scenarios in urban areas exposed to earthquakes. This will enable decision makers to take adequate preventive measures and develop appropriate mitigation strategies, i.e. crisis prevention and management plans to reduce the losses. It deals with the assessment of building seismic risk of urban areas in Algeria by using the RADIUS Model (Risk Assessment Tools for Diagnosis of Urban Areas against Seismic Disaster) after a prior adaptation to the Algerian context. It estimates also the expected number of victims and their spatial distributions. This concept is adopted to estimate the urban seismic risk of the Great-Blida region (consisting of 4 cities, namely Blida, Ouled-Yaich, Bouarfa and Beni-Mered), west of Algiers region, by performing an earthquake scenario. The region of Blida has experienced strong earthquakes during the last centuries generating seismic intensities ranging between X and XI, of which that most significant, occurred on Mars 2, 1825. It represents an important administrative, military, economic and scientific pole, and features a high concentration of population (1390 inhabitants/km2). In order to draw reliable results, an extensive survey was carried out concerning the buildings (approximately 46,000 units). The data were mapped and stored in databases using GIS tools. The results of this earthquake scenario show that serious damages would be observed in the studied area. The results reported in this study will drive the decision-making, by the local authorities, adapted to the specific socio-environmental vulnerability context at the Great-Blida urban scale. For this purpose, the paper proposes a list of operational measures contributing to the seismic risk reduction, relying on the resilience-building demand. A complementary study, i.e. a separate paper (second part), deals about assessment of seismic risk related to road infrastructures and lifelines devoted to the Algerian urban context.

Dealing with execution-overruns to improve the temporal robustness of real-time systems scheduled FP and EDF

Abstract: This paper presents a mechanism for execution-overrun management in preemptive real-time systems composed of sporadic tasks. We consider faults due to Worst Case Execution Time violations. Based on fault prevention, we determine the allowance of a task defined as the maximum extra duration that can be granted to a faulty task without compromising the timeliness constraints of the tasks. We propose a solution to implement the allowance principle that we call the Latest Execution Time (LET), defined for a task as the latest absolute time a faulty task can proceed with its execution without compromising the real-time constraints of all the tasks in the system. This mechanism enables to cope with execution overruns before a deadline miss and is not based on execution overruns handlers. We show how to determine the LET based on existing real-time feasibility conditions for Fixed Priority (FP) and Earliest Deadline First (EDF) schedulings. We compare the performances of the LET mechanism with FP and EDF scheduling to classical execution overrun management solutions.

In-plane external fiber Fabry–Perot cavity comprising silicon micromachined concave mirror

Abstract: Light trapping in optical cavities has many applications in optical telecommunications, biomedical optics, atomic studies, and chemical analysis. Efficient optical coupling in these cavities is an important engineering problem that affects greatly the cavity performance. Reported in-plane external fiber Fabry–Perot cavities in the literature are based on flat micromachined mirrors. In this case, the diffraction loss in the cavity is usually overcome by using an expensive-lensed fiber or by inserting a coated lens in the cavity leading to a long cavity with a small free spectral range. In this work, we report a Fabry–Perot cavity formed by a multilayer-coated cleaved-surface single-mode fiber inserted into a groove while facing a three-dimensional concave micromirror; both are fabricated by silicon micromachining. The light is trapped inside the cavity while propagating in-plane of the wafer substrate. Theoretical modeling is carried out, taking into account the effect of asymmetry in the mirror radii of curvature resulting from the micromachining process. A cavity is formed using a concave mirror with 200 and 100 μm in-plane and out-of-plane radii curvature, respectively. The presented cavity has a measured line width of 0.45 nm around 1330 nm showing a quality factor of about 3000, which resembles a one order of magnitude improvement over a flat-mirror cavity.