Inflation of the Aira Caldera (Japan) detected over Kokubu urban area using SAR interferometry ERS data

International audienceNine ERS-1 and ERS-2 descending orbit data acquired over Aira Caldera between June 1995 and November 1998 were used to create 36 differential interferograms. Although the interferograms exhibit a relatively low level of coherence, even for couples sampling short time intervals (6 months), Synthetique Aperture Radar (SAR) observations reveal a distinct range change pattern over Kokubu urban area whose amplitude increases with the time separation between SAR images. The analysis of the ground deformation time series relative to the earliest ERS images showed a maximum uplift of about 20 mm between the north and the south of the urban area during the period covered by our satellite observations. Taking the reduced surface of the coherent area into account, we performed a simple modeling of the deformation field assuming an inflating spherical source within an elastic half-space medium located beneath the centre of the Aira Caldera. This simple model predicts a maximum volume increase of 20–30×106 m3 between 1995 and 1998, which would produce an inflation of about 70 mm at the centre of the Aira Caldera and 40 mm in the Kokubu south urban area. These results are in good agreement with other geophysical observations carried out on the Aira caldera during this period. Despite the limited spatial extent of the coherent areas around the Aira Caldera, this study shows that DinSAR method using data collected in C band can be successfully used to detect subtle ground displacement changes of the volcanic complex and thus provides complementary information to ground-based geodetic monitoring of dynamic processes of the Aira Caldera and Sakurajima volcano

Implementation of Augmented Reality in a Mechanical Engineering Training Context

Global industry is at the heart of its fourth industrial revolution, being driven by the emergence of new digital solutions: Augmented reality allows us to consider the evolution towards the “the augmented operator”. This technology is currently little used in higher education, especially for mechanical engineers. We believe that it can facilitate learning and develop autonomy. The objective of this work is to assess the relevance of augmented reality in this context, as well as its impact on learning. The difficulties for a student approaching a technical system are related to reading and understanding 2D and even 3D representations, lack of knowledge on components functions, and the analysis of the chain of power transmission and transformation of movement. The research is intended to see if AR technologies are relevant to answer these issues and help beginners get started. To that end, several AR scenarios have been developed on different mechanical systems, using the relevant features of the AR interfaces that we have identified. Otherwise, these experiences have enabled us to identify specific issues linked to the implementation of AR. Our choice of AR devices and software allows us to have an integrated digital chain with digital tools and files used by mechanical engineers. Finally, we sought to assess how this technology made it possible to overcome the difficulties of learners, in different learning situations

Dynamics of quasi-two-dimensional turbulent jets

The study of quasi-two-dimensional turbulent jets is relevant to chemical reactors, the coking process in oil refinement, as well as rivers flowing into lakes or oceans. In the event of a spillage of pollutants into a river, it is critical to understand how these agents disperse with the flow in order to assess damage to the environment. For such flows, characteristic streamwise and cross-stream dimensions can be much larger than the fluid-layer thickness, and so the flow develops in a confined environment. When the distance away from the discharge location is larger than ten times the fluid-layer thickness, the flow is referred to as a quasi-two-dimensional jet. From experimental observations using dyed jets and particle image velocimetry, we find that the structure of a quasi-two-dimensional jet consists of a high-speed meandering core with large counter-rotating eddies developing on alternate sides of the core. The core and eddy structure is self-similar with distance from the discharge location. The Gaussianity of the cross-stream distribution of the time-averaged velocity is due, in part, to the sinuous instability of the core. To understand the transport and dispersion properties of quasi-two-dimensional jets we use a time-dependent advection--diffusion equation, with a mixing length hypothesis accounting for the turbulent eddy diffusivity. The model is supported by experimental releases of dye in jets or numerical releases of virtual passive tracers in experimentally-measured jet velocity fields. We consider the statistical properties of this flow by releasing and then tracking large clusters of virtual particles in the jet velocity field. The probability distributions of two-point properties (such as the distance between two particles) reveal large streamwise dispersion. Owing to this streamwise dispersive effect, a significant amount of tracers can be transported faster than the speed predicted by a simple advection model. Using potential theory, we determine the flow induced by a quasi-two-dimensional jet confined in a rectangular domain. The streamlines of the induced flow predicted by the theory agree with experimental measurements away from the jet boundary. Finally, we investigate the case of a quasi-two-dimensional particle-laden jet. Depending on the bulk concentration of dense particles, we identify different flow regimes. At low concentrations, the jet features the same core and eddy structure observed without the particles, and thus quasi-two-dimensional jet theory can apply to some extent. At larger concentrations, we observe an oscillating instability of the particle-laden jet.This work was supported by BP through the BP Institute, University of Cambridge, EPSRC through DAMTP, University of Cambridge, and the Cambridge Philosophical Society

PRÉFACE – Abstracta Iranica 25-2002

AI fête ses 25 ans. La revue paraît avec quelques mois de retard, mais huit mois seulement après le numéro 24. Les différentes rubriques sont d’importances variables : les inégalités ne sont pas encore résorbées mais les solutions sont en bonne voie. De nouveaux collaborateurs nous ont rejoints, enrichissant plusieurs rubriques. Par ailleurs, il faut se réjouir de voir la publication de la traduction persane du numéro 24 reprendre son rythme et sortir en même temps que ce numéro 25. Depuis un..

PRÉFACE – Abstracta Iranica 29 – 2006

Ce vingt neuvième numéro d’Abstracta Iranica, avec plus de 450 entrées, reflète une masse de publications relativement stable depuis quelques années : les domaines couverts varient un peu, soit en fonction de la plus ou moins grande abondance de documents, soit en raison de la disponibilité de nos collaborateurs. Ceux-ci, bien que très nombreux (66. pour ce numéro) travaillent bénévolement, prenant sur leur temps de recherche ou d’enseignement pour lire les ouvrages et rédiger les comptes-ren..

PRÉFACE – Abstracta Iranica 27 - 2004

A la parution du numéro 26, nous annoncions la mise en ligne prochaine d’Abstracta Iranica sur le site de revues.org : c’est chose faite depuis décembre 2005. Les numéros 25 et 26 sont consultables en ligne, en attendant, avant la fin de 2006, les numéros 24 et 23. Quant à ce volume 27, il est mis en ligne concomitamment à la sortie de la version papier, formule qui sera dorénavant poursuivie. Ce volume contient près de 400 entrées : certaines rubriques ont repris vie, du fait de l’intérêt de..

PRÉFACE – Abstracta Iranica 29 – 2006

Ce vingt neuvième numéro d’Abstracta Iranica, avec plus de 450 entrées, reflète une masse de publications relativement stable depuis quelques années : les domaines couverts varient un peu, soit en fonction de la plus ou moins grande abondance de documents, soit en raison de la disponibilité de nos collaborateurs. Ceux-ci, bien que très nombreux (66. pour ce numéro) travaillent bénévolement, prenant sur leur temps de recherche ou d’enseignement pour lire les ouvrages et rédiger les comptes-ren..

PRÉFACE – Abstracta Iranica 28 – 2005

Avec plus de 500 entrées, ce numéro 28 d’Abstracta Iranica offre un panorama plus large des publications 2005 et de quelques oublis de 2004. Certaines rubriques sont particulièrement fournies, reflétant la richesse des publications dans le domaine, mais aussi, soulignons-le, le travail des collaborateurs. Ceux-ci, toutes rubriques confondues, sont aujourd’hui près de 80 et viennent de divers pays, dont l’Iran. Ils seront certainement plus nombreux encore pour le numéro 29, actuellement en pré..