Search results for "Metro"
showing 10 items of 620 documents
Neural Adaptation to Optical Quality Defects
2010
From an optical perspective the eye is far from perfect. This is a fact that is extensively supported by literature; for instance, Prof. Navarro recently provided us with a fantastic critical review on the various theories behind the different eye models and their flaws.1 The human eye has considerable amounts of higher-order aberrations even when it is emmetropic,2 with great inter-individual variability. Besides, higher-order aberrations are still postulated to have a role in the development of the refractive error, although it is not clear the extent to which this may be (see Charman WN for a review).3 The known optical limitations of the normal human eye raised the question as to what t…
Needle-shape quality control by shadowgraphic image processing
2011
International audience; We propose a needle-shape quality-control method. To this end, we have devised a new acquisition system that combines a camera and a backlight. Needle measurements are carried out at a micrometric scale using shadowgraphic image processing. Our method not only distinguishes good needles from bad ones, but also allows classifying flawed needles into various categories of defects. This classification is important because some categories of defects can affect the entire production, whereas others do not. The results of our needle-shape quality-control method are validated using real samples directly off the manufacturing line. Needles are correctly classified at >97%, a…
3D part inspection path planning of a laser scanner with control on the uncertainty
2011
International audience; This article concerns the measurement process of mechanical parts using laser scanners. From the point of view of industrial applications, the objective is to guarantee the measurement accuracy during the scanning with regard to the geometrical product specifications. The proposed method can be summarized as follow: the first step consists of analyzing the interval of tolerance for the different specifications and to attribute to every geometrical entity a maximal uncertainty of measurement. This uncertainty depends on the angle of incidence between the laser plane and the scanned surface. In the second step, an approach based on the concept of visibility is used fro…
Using of a uncertainty model of an polyarticulated coordinates measuring arm to validate the measurement in a manufacturing processsus
2014
International audience; Coordinates Measuring Arms (CMA) are increasingly used to control industrial parts and are often an alternative to CMM controls that require conditions of laboratory measurement and involve significant costs. However, the control of uncertainties is often not guaranteed because the measurement process is complex and there is no standard for setting a framework qualification process of the measurement process.The proposed study, in this paper, is a first approach to model the measurement uncertainties of a CMA with contact sensor. The problem is complex because there are many sources of uncertainty, largely due to variability in the handling carried out by the operato…
3D Displacements and Strains Solid Measurement based on the Surface Texture with a Scanner Laser
2013
International audience; The developments of non-contact measurement are today widely due to the unprecedented progress of optronic. The applications of these techniques are wide and varied for the 3D measurement of industrial products. In addition to the forms and dimensions, we show in this paper that the devices of laser scanning permit to measure displacements and deformations. In this case, it is necessary to follow a solid particle in its motion. It is then necessary to identify the particle between two configurations of the body before and after displacement. The method of greyscale patterns, obtained by applying a spray, is generally used. The originality of the proposed method is ba…
Parameters analysis influencing 3D measurement without contact by laser scanner to establish a local correction procedure
2007
International audience; The techniques of measuring without contact by laser scanning allows acquisition of a large number of points, at a very high rate speed ; nevertheless with less precision than the one obtained by classical techniques of measuring with contact. We present in this article the research and the experimental analysis of the influential parameters on the precision of the measure by laser sensor without contact. Firstly, a methodology of correction of the relative uncertainties in the conditions of the measuring laser is presented. Then, we apply it to a typical part and compare the results to those obtained by a classical procedure of measuring with a contact sensor. We fi…
Taking digitized points quality into account in geometrical specification measurement by laser sensor
2004
International audience; Today, the new measurement techniques without contact like the laser sensors are used more and more in industrial applications. They allow to obtain many points in a short time. However these techniques have a less good accuracy than the classical process with contact probe for metrology application. The work presented in this paper, is part of a research project on the in-process product inspection. In the case of in-process product inspection, the throughput time must be the shortest with a good dimensional accuracy. So, it is necessary to increase the measurement accuracy of the points cloud for using the laser scanners. For this first approach, we suggest to buil…
Comparison of Flow Measurement by 4D Flow Magnetic Resonance Imaging and by Particles Image Velocimetry on Phantom of Abdominal Aortic Aneurysm
2016
International audience; Predicting the rupture of Aortic Aneurysms is a complex problem that interests, from several decades, many researchers. The works on this issue are very complex, involving both the study of mechanical behavior of the artery as the flow of blood. The Magnetic Resonance Imaging (MRI) technique allows to obtain anatomic information of the arteries, than the flow inside thereof. The goal of this study is an inter comparison betweenflow data from MRI and those obtained by Particle Image Velocimetry (PIV). An experimental device simulating hemodynamic circulation is used. Initially in order to validate the device, the flow in a cylindrical glass tube is measured by these t…
Where Alonso meets Sierpinski: an urban economic model of a fractal metropolitan area
2004
International audience; La coexistence d'activités résidentielles et agricoles dans des ceintures périurbaines caractérise de nombreuses aires métropolitaines modernes. Malheureusement, peu de modèles théoriques de l'économie urbaine prennent en compte ce type de mixité spatiale. L'article contribue à combler cette lacune : les auteurs présentent un modèle de localisation résidentielle (standard en économie urbaine) opérant dans un espace structuré par la géométrie spatiale. Plus précisément, d'un côté, un tapis de Sierpinski est utilisé pour rendre compte de l'organisation hiérarchisée de sites urbains et ruraux dans une aire métropolitaine. D'un autre côté, un ménage maximise, sous contra…
Développement de méthodes de référence pour les biomarqueurs du bilan lipidique : application au contrôle qualité en biologie clinique
2013
Reliable measurements in medical biology are essential for early screening and appropriate follow-up of patients. Ensuring metrological traceability of clinical measurements to higher order reference methods or certified reference materials enables to obtain comparable results over time and between different laboratories that could use different methods to quantify the same biomarker.In this study, reference methods were developed and validated for lipid profile biomarkers (total cholesterol, triglycerides, HDL-C, and LDL-C). Their value added in proficiency testing schemes was demonstrated against consensus mean. They were also used to characterize a certified reference material (CRM) that…