A localization and updating strategy of large finite element models in structural dynamics

The purpose of this paper is to evaluate the application of the error of constitutive law method to the updating of large FE models of space structures using FRF experimental results. First, we briefly recall the theoretical basis of this method in modal and frequency approaches. Then, the notion of visibility is introduced to improve the modelling of localization error and the quality of modal updating, for low frequencies. Finally we propose a global strategy and discuss the results we obtained on satellite JASON2

Reliability approach in spacecraft structures

This paper presents an application of the probabilistic approach with reliability assessment on a spacecraft structure. The adopted strategy uses meta-modeling with first and second order polynomial functions. This method aims at minimizing computational time while giving relevant results. The first part focuses on computational tools employed in the strategy development. The second part presents a spacecraft application. The purpose is to highlight benefits of the probabilistic approach compared with the current deterministic one. From examples of reliability assessment we show some advantages which could be found in industrial applications

Robust design of spacecraft structures under lack of knowledge

International audienceIn robust design, lacks of knowledge are rarely taken into account explicitly, but this is the case in the RRDO-IG. This paper summarises the ongoing developments and perspectives for the use of the RRDO-IG methodology in a spatial industrial context, where non-linearities have to be treated. After shortly describing the RRDO-IG methodology and the actual encountered problems, we will construct an improvement strategy based on a state of the art in metamodelisation and failure probability computation

Application des surfaces de réponse pour l’analyse fiabiliste d’une structure spatiale

Cette communication présente une application des surfaces de réponse pour l’analyse de la fiabilité d’une structure satellite. Les méta-modèles sont construits par régression itérative où seul les termes significatifs sont sélectionnés parmi une liste de régresseurs potentiels préalablement déterminée par une analyse de sensibilité. Les méta-modèles sont ensuite vérifiés par une méthode de bootstrap où les variations observées sur les prédictions sont prises en compte dans le calcul des probabilités de défaillance afin de valider le résultat

Predictability of Volcano Eruption: lessons from a basaltic effusive volcano

Volcano eruption forecast remains a challenging and controversial problem despite the fact that data from volcano monitoring significantly increased in quantity and quality during the last decades.This study uses pattern recognition techniques to quantify the predictability of the 15 Piton de la Fournaise (PdlF) eruptions in the 1988-2001 period using increase of the daily seismicity rate as a precursor. Lead time of this prediction is a few days to weeks. Using the daily seismicity rate, we formulate a simple prediction rule, use it for retrospective prediction of the 15 eruptions,and test the prediction quality with error diagrams. The best prediction performance corresponds to averaging the daily seismicity rate over 5 days and issuing a prediction alarm for 5 days. 65% of the eruptions are predicted for an alarm duration less than 20% of the time considered. Even though this result is concomitant of a large number of false alarms, it is obtained with a crude counting of daily events that are available from most volcano observatoriesComment: 4 pages, 4 figure

PHARAO Laser Source Flight Model: Design and Performances

In this paper, we describe the design and the main performances of the PHARAO laser source flight model. PHARAO is a laser cooled cesium clock specially designed for operation in space and the laser source is one of the main sub-systems. The flight model presented in this work is the first remote-controlled laser system designed for spaceborne cold atom manipulation. The main challenges arise from mechanical compatibility with space constraints, which impose a high level of compactness, a low electric power consumption, a wide range of operating temperature and a vacuum environment. We describe the main functions of the laser source and give an overview of the main technologies developed for this instrument. We present some results of the qualification process. The characteristics of the laser source flight model, and their impact on the clock performances, have been verified in operational conditions.Comment: Accepted for publication in Review of Scientific Instrument

Reverse Detection of Short-Term Earthquake Precursors

We introduce a new approach to short-term earthquake prediction based on the concept of selforganization of seismically active fault networks. That approach is named "Reverse Detection of Precursors" (RDP), since it considers precursors in reverse order of their appearance. This makes it possible to detect precursors undetectable by direct analysis. Possible mechanisms underlying RDP are outlined. RDP is described with a concrete example: we consider as short-term precursors the newly introduced chains of earthquakes reflecting the rise of an earthquake correlation range; and detect (retrospectively) such chains a few months before two prominent Californian earthquakes - Landers, 1992, M = 7.6, and Hector Mine, 1999, M = 7.3, with one false alarm. Similar results (described elsewhere) are obtained by RDP for 21 more strong earthquakes in California (M >= 6.4), Japan (M >= 7.0) and the Eastern Mediterranean (M >= 6.5). Validation of the RDP approach requires, as always, prediction in advance for which this study sets up a base. We have the first case of advance prediction; it was reported before Tokachi-oki earthquake (near Hokkaido island, Japan), Sept. 25, 2003, M = 8.1. RDP has potentially important applications to other precursors and to prediction of other critical phenomena besides earthquakes. In particular, it might vindicate some short-term precursors, previously rejected as giving too many false alarms.Comment: 17 pages, 5 figure

オルターモダン時代の中で自分のマニエラを作ることの思考

東京藝術大学平成25年

オルターモダン時代の中で自分のマニエラを作ることの思考 [要旨]

東京藝術大学平成25年

Prise en compte des environnements vibratoires dans les processus de validation des satellites

L'objectif de cette présentation dans le cadre du Congrès Français de Mécanique est d'évoquer le périmètre que représentent les démonstrations du bon comportement fonctionnel des satellites lorsqu'ils sont soumis à des environnements vibratoires. Pour ce faire, il est important de bien assimiler ce que sont ces environnements vibratoires que les différents constituants de ces satellites vont subir tout au long de leur existence. Il est question des phases de lancement pendant lesquelles les différents lanceurs susceptibles d'embarquer les satellites vont agir. Il est question également des phases de la vie orbitale où les opérations de fonctionnalité relatives à la mission du satellite devront s'accommoder de toutes les sources génératrices d'environnements vibratoires. Mais il est fortement question, pour finir, de tous les événements vibratoires venant agresser le satellite dans sa phase au sol et ce, soit pour reproduire au mieux les environnements vibratoires des phases lancement et vie orbitale en guise de validation, soit pour valider toutes les opérations inévitables que sont les transports, manutentions et réglages