A Fast Learning Algorithm for Image Segmentation with Max-Pooling Convolutional Networks

We present a fast algorithm for training MaxPooling Convolutional Networks to segment images. This type of network yields record-breaking performance in a variety of tasks, but is normally trained on a computationally expensive patch-by-patch basis. Our new method processes each training image in a single pass, which is vastly more efficient. We validate the approach in different scenarios and report a 1500-fold speed-up. In an application to automated steel defect detection and segmentation, we obtain excellent performance with short training times

From Supervised to Reinforcement Learning: a Kernel-based Bayesian Filtering Framework

International audienceIn a large number of applications, engineers have to estimate a function linked to the state of a dynamic system. To do so, a sequence of samples drawn from this unknown function is observed while the system is transiting from state to state and the problem is to generalize these observations to unvisited states. Several solutions can be envisioned among which regressing a family of parameterized functions so as to make it fit at best to the observed samples. This is the first problem addressed with the proposed kernel-based Bayesian filtering approach, which also allows quantifying uncertainty reduction occurring when acquiring more samples. Classical methods cannot handle the case where actual samples are not directly observable but only a non linear mapping of them is available, which happens when a special sensor has to be used or when solving the Bellman equation in order to control the system. However the approach proposed in this paper can be extended to this tricky case. Moreover, an application of this indirect function approximation scheme to reinforcement learning is presented. A set of experiments is also proposed in order to demonstrate the efficiency of this kernel-based Bayesian approach

Automatic Polynomial Form Correction with Autocorrelation Functions

12 pages, also available on the WEB in HTML at: http://cmm.ensmp.fr/~nion/Travaux/FormCorrection/Dealing with a surface's form is an essential part of any topographical study of the said surface's roughness. We present here a method for automatic correction of the form, using very simple concepts to solve a problem where top notch technologies were not enough mature to tackle. After explaining how well known mathematical tools such as the correlation function relate to this problem, we will see how they helped us to design an automatic procedure that we applied in order to get a highly reliable data set, that, in turn, underpinned a fine grain study on rough surfaces conducted at ArcelorMittal Research

Kernelizing Vector Quantization Algorithms

International audienceThe kernel trick is a well known approach allowing to implicitly cast a linear method into a nonlinear one by replacing any dot product by a kernel function. However few vector quantization algorithms have been kernelized. Indeed, they usually imply to compute linear transformations (e.g. moving prototypes), what is not easily kernelizable. This paper introduces the Kernel-based Vector Quantization (KVQ) method which allows working in an approximation of the feature space, and thus kernelizing any Vector Quantization (VQ) algorithm

Application de deux méthodes de télédétection rapprochée à l'étude des escarpements rocheux instables : la photogrammétrie et la scannerisation laser

Today, studying an unstable cliff requires on-site fracture measurement by means of a clinometer compass. From accessibility and safety point of view, this method is far from perfect. Teledetection techniques provides an alternative for studying the cliffs morphology without such in-place measurements. Two methods seams beforehand particularly well suited. Photogrammetry on the one hand leads to the computation of the XYZ position of a point starting from its 2D position in two photographs taken from slightly different point of view. Numeric cameras have brought great improvements to this robust technique. Laser scanning on the other hand, consist in computing the position of a large number of points on the wall by measuring the time used by a laser impulse to reflect on the cliff. These two methods are subject two different limitations in terms of resolution, precision, on-site acquisition time and required computing power. Photogrammetry and laser scanning have been used on four sites to test their efficiency on real unstable cliffs. The Rocher du Midi zone (Vercors, 38, France), has been first studied with two laser scans acquired with a very grazing point of view from the top of the unstable wall. It has also been photographed with a large field silver camera from an helicopter. The Ravin de l'aiguille (Chartreuse, 38, France) has been studied through two laser scans realized ahead from the wall. The first one at grazing angle and the other one almost from a front point of view. These acquisitions were possible thanks to the crest line specific geometry. A photographic cover has also been realized from a numeric reflex on helicopter board. The Rocher de la bourgeoise (Vercors, 38, France), has been measured by means of a laser scanning on helicopter board and by mean of pictures taken at the same time from a numeric camera. The Gorges de Paganin (06, France) have been studied with three laser scan from the bottom of the cliff. To be able to use laser scan data from these four sites, the concept of solid image developed by the Turin Polotecnico has been reimplemented in the ImageJ software. Thus, add-ons have been easily developed for each measurement usefull for the ex-ploitation. Comparing the results obtained by this technique with those obtained with photogrammetry or direct on-site measurement have proved, with several restrictions, the efficiency of both teledection methods. Teledetection in general and the solid image concept in particular provide a noticeable added value compared to on-site measurements because they can be used as a support to complementary geophysic measurements or they can help the computation of a full geometric model preliminary tostability simulation. Despite these good results, improvements could still be obtained to exploit at bestthe laser scan and the photogrammetry techniques.A l'heure actuelle, l'étude d'une falaise instable nécessite la mesure sur place, à l'aide d'une boussole clinomètre, de sa fracturation. Ce n'est pas sans inconvénient pour des raisons d'accessibilité et de dangerosité de la mesure. Pour étudier la morphologie de ces falaises sans recourir à ces mesures in-situ, il faut faire appel à des méthodes de télédétection. Deux méthodes semblent a priori particulièrement adaptées pour ce faire. La photogrammétrie permet de calculer la position XYZ d'un point à partir de la position de l'image de ce point sur deux photographies prisent depuis des points de vue différents. Cette technique éprouvée connait un nouvel essor avec les progrès des appareils numériques. La scannerisation laser, quant à elle, consiste à calculer la position d'un très grand nombre de points de la paroi en mesurant le temps de trajet aller-retour d'une impulsion laser. Ces deux méthodes connaissent des limitations différentes en terme de résolution, de précision, de temps d'acquisition sur site et de traitement a posteriori. La photogrammétrie et la scannerisation laser ont été utilisées sur quatre sites afin de tester l'efficacité de ces méthodes sur des cas concrets de falaise instable. Le site du Rocher du Midi (Vercors, 38, France) a été étudié à l'aide de deux scans laser réalisés depuis le sommet de la paroi instable, avec des points de vue très rasants sur fa zone d'étude, ainsi qu'au moyen d'une couverture photographique réalisée avec un appareil argentique grand format depuis un hélicoptère. Le Ravin de L'aiguille (Chartreuse, 38, France) a été étudié à partir de deux scannerisations laser réalisées en tête de paroi, l'une depuis un point de vue très rasant et l'autre depuis un point de vue presque frontal, permis par la géométrie très échancrée de la ligne de crête, ainsi qu'avec une couverture photographique réalisée avec un reflex numérique depuis un hélicoptère. Le Rocher de la Bourgeoise (Vercors, 38 France) a été étudié au moyen d'une scannerisation laser héliportée et d'une couverture photographique réalisée en même temps avec un appareil numérique. Les gorges de Paganin (06, France) ont été étudiées au moyen de trois scannerisations laser réalisées depuis le pied de la paroi. Pour pouvoir exploiter les données de scannerisation laser issues de ces quatre sites, le concept d'image solide, développé par le Politecnico de Turin, a été réimplanté dans le logiciel ImageJ afin de développer aisément des greffons pour chacune des mesures utiles à l'exploitation. La comparaison des résultats obtenus par cette méthode avec ceux obtenus par photogrammétrie et ceux issus des mesures directe sur site valide l'efficacité des deux méthodes de télédétection, avec cependant quelques réserves. Les méthodes de télédétection, et en particulier l'image solide, apportent une plus value notable par rapport aux mesures in-situ en terme de capacité de support aux mesures géophysiques complémentaires et de réalisation d'un modèle géométrique complet en prélude à une simulation de stabilité. Cependant des développements restent à faire, tant sur l'exploitation des scannerisations laser que sur l'utilisation de la photogrammétrie, pour permettre de tirer le meilleur parti possible de ces deux techniques

Combined use of geophysical methods and remote techniques for characterizing the fracture network of a potential unstable cliff site (the “Roche du Midi”, Vercors massif, France)

International audienceStability assessment of a cliff strongly depends on the fracture pattern and the face topography. Geological observations as well as classical geodetic measurements are difficult to perform on high nearly vertical cliffs like the ones surrounding the town of Grenoble (French Alps). In this study we combine remote and ground imaging techniques for characterizing the geometry and the fracture pattern of potential unstable cliff sites. A Dense Digital Surface Model (DDSM) of the rock face can now be obtained from laser scanning (Lidar) or photogrammetry. These techniques are safer and quicker than direct measurements. They offer the possibility to collect structural data and to sample the shape of the outcrop at a centimetric resolution. We applied these two techniques to a potential unstable site (the “Roche du Midi”, Vercors massif) for determining the main fracture families affecting the rock mass and we obtained results similar to direct measurements performed on the nearby outcrops and on the cliff face itself. The laser scanning data suffers a bias in the illumination of the site. Geophysical experiments were also conducted on the plateau and on the cliff face in order to delineate the fracture pattern inside the rock mass. ERT (Electrical Resistivity Tomography) and GPR (Ground Penetrating Radar) profiles were performed on the plateau and allowed near-vertical open fractures to be located in the vicinity of the surface. Best geophysical results in terms of penetration and resolution were however obtained from GPR profiles conducted directly on the cliff face. Laser scanning data were combined with GPR data in order to take into account the shape of the sampled profiles. The combination of vertical and short horizontal profiles allowed the strike and dip of the discontinuities to be determined. The two main families were imaged, as well as a major continuous inward dipping reflector which was not shown during the initial reconnaissance. Further investigation inside the mass effectively showed the existence of this fracture. These results highlight the power of the GPR technique in characterizing the discontinuity pattern inside rock mass for improving the model in view of hazard assessment

Numerical simulation of thin paint film flow

International audienceBeing able to predict the visual appearance of a painted steel sheet, given its topography before paint application, is of crucial importance for car makers. Accurate modeling of the industrial painting process is required. The equations describing the leveling of the paint are complex and their numerical simulation requires advanced mathematical tools, which are described in detail in this paper. Simulations are validated using a large experimental database obtained with a wavefront sensor developed by PhasicsTM

A QUANTITATIVE METHOD FOR ANALYSING 3-D BRANCHING IN EMBRYONIC KIDNEYS: DEVELOPMENT OF A TECHNIQUE AND PRELIMINARY DATA

The normal human adult kidney contains between 300,000 and 1 million nephrons (the functional units of the kidney). Nephrons develop at the tips of the branching ureteric duct, and therefore ureteric duct branching morphogenesis is critical for normal kidney development. Current methods for analysing ureteric branching are mostly qualitative and those quantitative methods that do exist do not account for the 3- dimensional (3D) shape of the ureteric "tree". We have developed a method for measuring the total length of the ureteric tree in 3D. This method is described and preliminary data are presented. The algorithm allows for performing a semi-automatic segmentation of a set of grey level confocal images and an automatic skeletonisation of the resulting binary object. Measurements of length are automatically obtained, and numbers of branch points are manually counted. The final representation can be reconstructed by means of 3D volume rendering software, providing a fully rotating 3D perspective of the skeletonised tree, making it possible to identify and accurately measure branch lengths. Preliminary data shows the total length estimates obtained with the technique to be highly reproducible. Repeat estimates of total tree length vary by just 1-2%. We will now use this technique to further define the growth of the ureteric tree in vitro, under both normal culture conditions, and in the presence of various levels of specific molecules suspected of regulating ureteric growth. The data obtained will provide fundamental information on the development of renal architecture, as well as the regulation of nephron number