The Latent Structure of Dictionaries

How many words (and which ones) are sufficient to define all other words? When dictionaries are analyzed as directed graphs with links from defining words to defined words, they reveal a latent structure. Recursively removing all words that are reachable by definition but that do not define any further words reduces the dictionary to a Kernel of about 10%. This is still not the smallest number of words that can define all the rest. About 75% of the Kernel turns out to be its Core, a Strongly Connected Subset of words with a definitional path to and from any pair of its words and no word’s definition depending on a word outside the set. But the Core cannot define all the rest of the dictionary. The 25% of the Kernel surrounding the Core consists of small strongly connected subsets of words: the Satellites. The size of the smallest set of words that can define all the rest (the graph’s Minimum Feedback Vertex Set or MinSet) is about 1% of the dictionary, 15% of the Kernel, and half-Core, half-Satellite. But every dictionary has a huge number of MinSets. The Core words are learned earlier, more frequent, and less concrete than the Satellites, which in turn are learned earlier and more frequent but more concrete than the rest of the Dictionary. In principle, only one MinSet’s words would need to be grounded through the sensorimotor capacity to recognize and categorize their referents. In a dual-code sensorimotor-symbolic model of the mental lexicon, the symbolic code could do all the rest via re-combinatory definition

Camera Pose Estimation with Semantic 3D Model

International audienceIn computer vision, estimating camera pose from correspondences between 3D geometric entities and their projections into the image is a widely investigated problem. Although most state-of-the-art methods exploit simple primitives such as points or lines, and thus require dense scene models, the emergence of very effective CNN-based object detectors in the recent years have paved the way to the use of much lighter 3D models composed solely of a few semantically relevant features. In that context, we propose a novel model-based camera pose estimation method in which the scene is modeled by a set of virtual ellipsoids. We show that 6-DoF camera pose can be determined by optimizing only the three orientation parameters, and that at least two correspondences between 3D ellipsoids and their 2D projections are necessary in practice. We validate the approach on both simulated and real environments

Les retrouvailles anachroniques d’une communauté avec son fondateur

Depuis l'année 994, une quinzaine de villes et villages autour de Limoges exhibent somptueusement les crânes-reliques de saints qu'ils honorent en tant qu'ancêtres communs et fondateurs de leurs communautés. Depuis le xviie siècle et la Contre-Réforme, ces fêtes ostensionnaires sont renouvelées régulièrement tous les sept ans. Les rites de dévotions aux saints patrons consistent ici à construire un lien étroit, organique, entre l'espace géographique et politique de vie (le terroir communal) et une entité transcendante à la fois divine et humaine (le saint), « objectifiée » dans une relique ; ils apportent une dimension transcendantale au terroir qui le fonde en territoire, au sens fort du terme. En vénérant leurs saints, les gens construisent leur propre interlocuteur divin et conservent ainsi, face à l'Église, la maîtrise du rite religieux qui leur permet d'élaborer symboliquement une souveraineté sociale qu'ils revendiquent aussi sur le mode politique.A Local Community’s Anachronic Encounter with its Founder: Holy Relics and Territory in the Limoges Area. – Since 994 AD, approximately fifteen villages and towns around Limoges (France) have been sumptuously exhibiting relics (skulls) of patron saints revered as common ancestors who founded their communities. Since the 17th century, and the Counter Reformation, these ostentatious celebrations have regularly taken place every seven years. Rites of veneration of these saints construct a narrow, organic bond between the geographical and political locality and a transcendent entity (the saint) who, both divine and human, is “objectified” in a relic. These ceremonies endow the locality with a transcendental dimension making it into a territory in the strong sense of the word. By venerating their saints, local people construct their own divine intercessor and thus maintain, irrespective of the Catholic Church, control over these religious rites which serve as the basis for symbolically constructing the social sovereignty that they demand in the political realm too

Camera Relocalization with Ellipsoidal Abstraction of Objects

International audienceWe are interested in AR applications which take place in man-made GPS-denied environments, as industrial or indoor scenes. In such environments, relocalization may fail due to repeated patterns and large changes in appearance which occur even for small changes in viewpoint. We investigate in this paper a new method for relocalization which operates at the level of objects and takes advantage of the impressive progress realized in object detection. Recent works have opened the way towards object oriented reconstruction from elliptic approximation of objects detected in images. We go one step further and propose a new method for pose computation based on ellipse/ellipsoid correspondences. We consider in this paper the practical common case where an initial guess of the rotation matrix of the pose is known, for instance with an inertial sensor or from the estimation of orthogonal vanishing points. Our contributions are twofold: we prove that a closed-form estimate of the translation can be computed from one ellipse-ellipsoid correspondence. The accuracy of the method is assessed on the LINEMOD database using only one correspondence. Second, we prove the effectiveness of the method on real scenes from a set of object detections generated by YOLO. A robust framework that is able to choose the best set of hypotheses is proposed and is based on an appropriate estimation of the reprojection error of ellipsoids. Globally, considering pose at the level of object allows us to avoid common failures due to repeated structures. In addition, due to the small combinatory induced by object correspondences, our method is well suited to fast rough localization even in large environments

Feurs – Rue Motton, rue Gambetta, rue Michelet, rue Jules-Ferry

Deux interventions se sont déroulées chez des particuliers : des sondages avant la construction d’une maison individuelle, rue Michelet (responsable : M.-O. Lavendhomme) ; une surveillance de terrassements pour la construction de garages, rue Jules-Ferry (responsable : É. Plassot). À cela, s’ajoutent diverses observations effectuées lors du suivi de travaux de réaménagement de la voirie. Ceux-ci s’inscrivent dans un programme de restructuration de la circulation en centre-ville, engagé par l..

Monitoring of a Large Cracked Concrete Sample with Non-Linear Mixing of Ultrasonic Coda Waves

International audienceA high precision can be achieved with ultrasonic coda waves to monitor the mechanical properties of concrete material (~10-5 in relative). This high sensitivity can be used to detect damage initiation and to closely follow concrete mechanical properties evolution with time. This advantage is counterbalance by the influence of environmental conditions making reproducibility of any experiment in concrete a challenging issue especially when in situ measurements are performed. Indeed thermal and water gradients present in the thickness of the structures (several decimetres) cannot be controlled and must be compensated. In this paper a protocol to remove environmental bias is proposed. Furthermore, to follow the apparition of a tensile crack in a metric size structure, non-linear mixing of coda wave via frequency-swept pump waves is tested. It is shown that, when the crack is closed (by pre-stressing cables), it is still possible to detect its presence. The non-linearity of the cracked zone remains at a high level, comparable to the case when the crack was open

: Tubulin dimer binding proteins

International audienceMicrotubules play an essential role in eukaryotic cells, where they perform a wide variety of functions. In this paper, we describe the characterization of proteins associated to tubulin dimer in its native form, using affinity chromatography and mass spectrometry. We used an immunoaffinity column with coupled-monoclonal antibody directed against the alpha-tubulin C-terminus. Tubulin was first loaded onto the column, then interphase and mitotic cell lysates were chromatographed. Tubulin-binding proteins were eluted using a peptide mimicking the alpha-tubulin C-terminus. Elution fractions were analyzed by SDS-PAGE, and a total of 14 proteins were identified with high confidence by mass spectrometry. These proteins could be grouped in four classes: known tubulin-binding proteins, one microtubule-associated protein, heat shock proteins, and proteins that were not shown previously to bind tubulin dimer or microtubules

Handling Occlusion in Augmented Reality Systems: A Semi-Automatic Method

We present a semi-automatic approach to solve occlu- sion in AR systems. Once the occluding objects have been segmented by hand in selected views called key-frames, the occluding boundary is computed automatically in the in- termediate views. To do that, the 3D reconstruction of the occluding boundary is achieved from the outlined silhou- ettes. This allows us to recover a good prediction of the 2D occluding boundary which is refined using region-based tracking and active contour models. As a result, we get an accurate estimation of the occluding objects. Various results are presented demonstrating occlusion resolution on real video sequences. Results and videos are available at the URL: http://cvlab.epfl.ch/~lepeti

Conclusion

Les organisations professionnelles et syndicales en France ont-elles été incapables de constituer à elles seules un tissu conventionnel, juridique et institutionnel qui soit suffisamment solide pour réguler les rapports entre employeurs et salariés dans le champ du travail, de l’emploi et de la formation professionnelle ? Ou faut-il revenir sur l’hypothèse trop classique du comblement par l’État d’un vide de relations sociales, engendré, depuis la Révolution française, par la faiblesse des co..