Joint inversion of muon tomography and gravimetry - a resolving kernel approach

Both muon tomography and gravimetry are geophysical methods that provide information on the density structure of the Earth's subsurface. Muon tomography measures the natural flux of cosmic muons and its attenuation produced by the screening effect of the rock mass to image. Gravimetry generally consists in measurements of the vertical component of the local gravity field. Both methods are linearly linked to density, but their spatial sensitivity is very different. Muon tomography essentially works like medical X-ray scan and integrates density information along elongated narrow conical volumes while gravimetry measurements are linked to density by a 3-dimensional integral encompassing the whole studied domain. We develop the mathematical expressions of these integration formulas -- called acquisition kernels -- to express resolving kernels that act as spatial filters relating the true unknown density structure to the density distribution actually recoverable from the available data. The resolving kernels provide a tool to quantitatively describe the resolution of the density models and to evaluate the resolution improvement expected by adding new data in the inversion. The resolving kernels derived in the joined muon/gravimetry case indicate that gravity data are almost useless to constrain the density structure in regions sampled by more than two muon tomography acquisitions. Interestingly the resolution in deeper regions not sampled by muon tomography is significantly improved by joining the two techniques. Examples taken from field experiments performed on La Soufri\`ere of Guadeloupe volcano are discussed.Comment: Submitted to Geoscientific Model Developmen

Les "columnae" (AP, v. 173) et la boutique : une image horacienne à l'âge de l'imprimerie

Numéro thématique : " Horace, l'autre poétique " Actes des journées d'étude du 19 octobre 2010 et du 28 mai 2011, dir. Nathalie Dauvois.Texte intégral disponible en ligne : http://www.paris-sorbonne.fr/IMG/pdf/5-JOURDE.pd

Two contrasting Malagasy representations of democracy: the period of legalist means of resistance based on colonial French laws (1925-1945). The myth of democracy already at work in rural communities during the precolonial times (1950-1972)

Paper presented at the Wits History Workshop: Democracy, Popular Precedents, Practice and Culture, 13-15 July, 199

Linguistique et colonialisme : la place des études sur le XVIe siècle européen

Numéro thématique : " Linguistiques et colonialismes ", dir. Cécile Van den Avenne.Cet article vise à interroger les rapports linguistiques de domination propres à la Renaissance européenne en liant les deux dynamiques qui semblent déterminer la pensée linguistique de l'époque : les " découvertes " géographiques, qui augmentent considérablement le nombre de langues connues, et l'affirmation en Europe du vulgaire face au latin, qui permet l'émergence de nouvelles langues ainsi décrites et mises en valeur. Au-delà d'une réévaluation de l'histoire européocentrée du savoir linguistique, les textes du XVIe siècle présentent des caractéristiques particulières dans les processus d'enregistrement de la diversité linguistique et dans les modes de défense, ou au contraire de mise à l'écart, des vulgaires, caractéristiques qui obligent à questionner aussi la notion même de " littérature ". La prise en considération des rapports linguistiques de domination au début de l'époque moderne semble rendre nécessaire une redéfinition du geste littéraire, de ce qu'est " écrire " dans " une langue ". Document téléchargeable à l'adresse suivante : http://www.univ-rouen.fr/dyalang/glottopol/telecharger/numero_20/gpl20_02couffignal_jourde.pd

Characterisation of the transmissivity field of a fractured and karstic aquifer, Southern France

International audienceGeological and hydrological data collected at the Terrieu experimental site north of Montpellier, in a confined carbonate aquifer indicates that both fracture clusters and a major bedding plane form the main flow paths of this highly heterogeneous karst aquifer. However, characterising the geometry and spatial location of the main flow channels and estimating their flow properties remain difficult. These challenges can be addressed by solving an inverse problem using the available hydraulic head data recorded during a set of interference pumping tests.We first constructed a 2D equivalent porous medium model to represent the test site domain and then employed regular zoning parameterisation, on which the inverse modelling was performed. Because we aim to resolve the fine-scale characteristics of the transmissivity field, the problem undertaken is essentially a large-scale inverse model, i.e. the dimension of the unknown parameters is high. In order to deal with the high computational demands in such a large-scale inverse problem, a gradient-based, non-linear algorithm (SNOPT) was used to estimate the transmissivity field on the experimental site scale through the inversion of steady-state, hydraulic head measurements recorded at 22 boreholes during 8 sequential cross-hole pumping tests. We used the data from outcrops, borehole fracture measurements and interpretations of inter-well connectivities from interference test responses as initial models to trigger the inversion. Constraints for hydraulic conductivities, based on analytical interpretations of pumping tests, were also added to the inversion models. In addition, the efficiency of the adopted inverse algorithm enables us to increase dramatically the number of unknown parameters to investigate the influence of elementary discretisation on the reconstruction of the transmissivity fields in both synthetic and field studies.By following the above approach, transmissivity fields that produce similar hydrodynamic behaviours to the real head measurements were obtained. The inverted transmissivity fields show complex, spatial heterogeneities with highly conductive channels embedded in a low transmissivity matrix region. The spatial trend of the main flow channels is in a good agreement with that of the main fracture sets mapped on outcrops in the vicinity of the Terrieu site suggesting that the hydraulic anisotropy is consistent with the structural anisotropy. These results from the inverse modelling enable the main flow paths to be located and their hydrodynamic properties to be estimated

Muon tomography applied to active volcanoes

Muon tomography is a generic imaging method using the differential absorption of cosmic muons by matter. The measured contrast in the muons flux reflects the matter density contrast as it does in conventional medical imaging. The applications to volcanology present may advantadges induced by the features of the target itself: limited access to dangerous zones, impossible use of standard boreholes information, harsh environmental conditions etc. The Diaphane project is one of the largest and leading collaboration in the field and the present article summarizes recent results collected on the Lesser Antilles, with a special emphasis on the Soufri\`ere of Guadeloupe.Comment: 7 pages, 7 figures, International Conference on New Photo-detectors,PhotoDet2015, 6-9 July 2015, Moscow, Troitsk, Russia. Submitted to Po

COMM Notation for Specifying Collaborative and MultiModal Interactive Systems

International audienceMulti-user multimodal interactive systems involve multiple users that can use multiple interaction modalities. Although multi-user multimodal systems are becoming more prevalent (especially multimodal systems involving multitouch surfaces), their design is still ad-hoc without properly keeping track of the design process. Addressing this issue of lack of design tools for multi-user multimodal systems, we present the COMM (Collaborative and MultiModal) notation and its on-line editor for specifying multi-user multimodal interactive systems. Extending the CTT notation, the salient features of the COMM notation include the concepts of interactive role and modal task as well as a refinement of the temporal operators applied to tasks using the Allen relationships. A multimodal military command post for the control of unmanned aerial vehicles (UAV) by two operators is used to illustrate the discussion

e-COMM, un éditeur pour spécifier l'interaction multimodale et multiutilisateur

National audienceCet article présente l'éditeur e-COMM pour la spécification de systèmes interactifs multimodaux et multiutilisateurs à l'aide de la notation COMM. La majorité des notations dédiées à la conception des collecticiels offrent des moyens limités pour décrire l'interaction multimodale. Ainsi la notation COMM comble ce manque en introduisant de nouveaux concepts (tâche modale et rôle interactif) pour lier ces deux aspects : l'interaction multimodale et multiutilisateur. L'éditeur e-COMM vise alors deux objectifs : founir un outil facilement accessible et aider le concepteur à se concentrer sur la tâche d'édition en reposant autant que possible sur la manipulation directe