Improving situation awareness of a single human operator interacting with multiple unmanned vehicles: first results

In the context of the supervision of one or several unmanned vehicles by a human operator, the design of an adapted user interface is a major challenge. Therefore, in the context of an existing experimental set up composed of a ground station and heterogeneous unmanned ground and air vehicles we aim at redesigning the human-robot interactions to improve the operator's situation awareness. We base our new design on a classical user centered approach

Object Description Based on Spatial Relations between Level-Sets

International audienceObject recognition methods usually rely on either structural or statistical description. These methods aim at describing different types of information such as the outer contour, the inner structure or texture effects. Comparing two objects then comes down to averaging different data representations which may be a tricky issue. In this paper, we introduce an object descriptor based on the spatial relations that structures object content. This descriptor integrates in a single homogeneous representation both shape information and relative spatial information about the object under consideration. We use this description in the context of image retrieval and show results on a butterfly image database compared with both GFD and SIFT descriptors

Experimental simulation of magma mixing at high pressure

International audienceMagma mixing features are observed in many plutonic and volcanic environments. They result from the juxtaposition of two chemically contrasted magmas, usually during the replenishment of a magmatic reservoir, but also syn-eruptively within the conduit. Despite its ubiquity, only a few experimental studies have explored mixing between magmas. Existing data have been mostly acquired at atmospheric pressure and high shear rates (> 10- 1 s- 1), which differ from those accompanying magma mixing in reservoirs. To fill this gap, we performed high pressure mixing experiments at strain rates ranging from 4.10- 4 to 1.10- 3 s- 1. Layers of a synthetic crystal-free haplotonalite and a natural partially-molten basalt were juxtaposed in a Paterson apparatus at 300 MPa, and deformed between 900 and 1200 °C. The experiments shed light on the first stages of magma mixing and illustrate the role and behavior of crystals, either pre-existing or newly grown. Experiments evidence a rheological threshold for mafic material disruption, which sets in abruptly as its melt fraction exceeds 50%, which in the experiments occurs in the narrow temperature interval 1160-1170 °C. Below this threshold, plagioclase crystals in the mafic magma form a rigid touching network and all the deformation is accommodated by the less viscous felsic layer. Above it the crystal network collapses, allowing typical mingling/mixing features to appear altogether, such as enclaves, melt filaments or single xenocrysts isolated into the felsic end-member, coexisting with newly grown phases (plagioclase and pyroxene) whose compositions spread out over considerable ranges. The pre-existing fabric of the mafic magma is only slightly affected by deformation, altogether providing few clues on either the regime or geometry of applied deformation during the magmatic stage

Porosity redistribution enhanced by strain localization in crystal-rich magmas

International audienceMagma degassing, characterized by changes in permeability and porosity distribution, has a crucial control on the style of eruption. During ascent, magma might develop large porosities and crystallise while it is subjected to shear. Shear, in turn, enhances complex fabrics that result from the reorganization of the different phases (crystals, gas, melt). Such fabrics have not yet been evaluated experimentally on a 3-phase system. We performed torsion experiments on a synthetic crystal-rich hydrous magma at subsolidus conditions with 11 vol.% porosity to establish a link between strain partitioning and porosity redistribution. Crystals induce non-Newtonian deformation, resulting in localization of the shear strain. 3-D microtomography and 2-D Scanning Electron Microprobe (SEM) imaging show gas accumulation in local microstructures caused by shear-induced crystal fabric. Our data show that strain localization is a mechanism that could enable magma degassing at very low vesicularity

Generalized method for determining fluoroacidity by electrochemical diffusion coefficient measurement (application to HfF4)

A universal method for fluoroacidity evaluation was developed and based on a mass transport approach: it simply consists in measuring the diffusion coefficient of an electroactive species in various molten media. The reduction behaviour of Hf(IV) ions was investigated in molten fluorides and diffusion coefficients of Hf(IV) ions were measured. Results showed that diffusion coefficients decrease with fluoroacidity, due to the effect of solvent viscosity (which is linked to bridged fluorines). A global approach of mass transport in solution was then proposed, taking into account both solute and solvent. The Schmidt number (Sc) defined as the ratio between solvent viscosity and solute diffusivity was calculated in order to take into account these two parameters. Results showed that Sc increases with fluoroacidity, in a much more sensitive way than D. This universal method can extended to all electroactive species and to all bath fluoroacidity

Développement d'une puce instrumentée adaptée à la mesure de température dans les modules de puissance

International audienceLa mesure de la température des composants semi-conducteurs de puissance est primordiale, notamment pour l'évaluation des performances et dans la perspective de proposer le suivi de l'état de santé des systèmes de conversion d'énergie électrique. Aujourd'hui, les paramètres électriques thermosensibles (PETS) sont largement utilisés pour estimer une température représentative de celle de ces composants, souvent dans des conditions de fonctionnement différentes de l'environnement réel des systèmes (mesures off-line). Il existe néanmoins plusieurs PETS dédiés à la mesure de température dans des conditions de fonctionnement réel des composants (mesures on-line). La principale difficulté réside cependant dans l'approche de validation de la précision de mesure obtenue avec ces PETS. Cet article présente un moyen permettant d'estimer la température grâce à une puce instrumentée adaptée à une utilisation dans les modules de puissance. L'objectif est de fournir un outil robuste et fiable pour la mesure de la température dans les modules de puissance en fonctionnement. Les résultats préliminaires présentés dans cet article portent sur les procédés de réalisation du capteur et démontrent le bon fonctionnement de cette puce instrumentée en régime de dissipation continue

Quel impact de l'entrée vocale sur la conception graphique d'un service mobile ?

Le développement d’interfaces multimodales bénéficiant de l’entrée vocale se traduira dans un certain nombre de cas par une évolution d’une conception graphique existante. Entre adaptation mineure et reconception totale, se pose la question de savoir quel impact une telle évolution sur l’existant peut avoir. Pour apporter des éléments de réponse à cette question, une expérience a été menée dans le cadre du projet européen Use-Me.Gov pour lequel on devait reconcevoir un service existant de diffusion d'information sur des événements municipaux en y ajoutant une entrée vocale. Cet article rapporte les principaux résultats de cette expérience ainsi que les enseignements que nous en avons tirés

Revisiting Occurrence Typing

We revisit occurrence typing, a technique to re ne the type of variables occurring in type-cases and, thus, capture some programming patterns used in untyped languages. Although occurrence typing was tied from its inception to set-theoretic types-union types, in particular-it never fully exploited the capabilities of these types. Here we show how, by using set-theoretic types, it is possible to develop a general typing framemork that encompasses and generalizes several aspects of current occurrence typing proposals and that can be applied to tackle other problems such as the inference of intersection types for functions and the optimization of the compilation of gradually typed languages

Intra- and inter-tester reliability of spasticity assessment in standing position in children and adolescents with cerebral palsy using a paediatric exoskeleton

Background The L-STIFF tool of the Lokomat evaluates the hip and knee flexors and extensors spasticity in a standing position. It moves the lower limb at a controlled velocity, measuring joint resistance to passive movements. Since its reliability in children with cerebral palsy remains unknown, our goal was to evaluate the relative and absolute reliability of L-STIFF in children with cerebral palsy. Methods Reliability was determined in 16 children with cerebral palsy by two experienced therapists. The changes in resistive torque in hip and knee in both flexion and extension were measured. Relative and absolute reliability were estimated using the intraclass correlation coefficient, standard error of measurement, and minimal detectable change. Reliability was assessed on three levels: (1) intra- and (2) inter-tester within session, and (3) intra-tester between sessions. Results Intraclass correlation coefficients were moderate to excellent for intra-tester reliability (all p ≤ 0.01). The standard error of measurement ranged from 0.005 to 0.021 Nm/° (i.e., 7–16%) and minimal detectable change from 0.014 to 0.059 Nm/°. Inter-tester intraclass correlation coefficients ranged from 0.32 to 0.70 (all p ≤ 0.01), standard error of measurement ranged from 0.012 to 0.029 Nm/° (i.e., 6–39%), and minimal detectable change ranged from 0.033 to 0.082 Nm/°. L-STIFF reliability was better during fast and medium movement speeds compared to slow speeds. Conclusions The assessment tool L-STIFF is a promising tool for quantifying lower limb spasticity in children with cerebral palsy in a standing position. However, the results should be interpreted carefully