65 research outputs found

    A Fisher-Rao metric for paracatadioptric images of lines

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    In a central paracatadioptric imaging system a perspective camera takes an image of a scene reflected in a paraboloidal mirror. A 360° field of view is obtained, but the image is severely distorted. In particular, straight lines in the scene project to circles in the image. These distortions make it diffcult to detect projected lines using standard image processing algorithms. The distortions are removed using a Fisher-Rao metric which is defined on the space of projected lines in the paracatadioptric image. The space of projected lines is divided into subsets such that on each subset the Fisher-Rao metric is closely approximated by the Euclidean metric. Each subset is sampled at the vertices of a square grid and values are assigned to the sampled points using an adaptation of the trace transform. The result is a set of digital images to which standard image processing algorithms can be applied. The effectiveness of this approach to line detection is illustrated using two algorithms, both of which are based on the Sobel edge operator. The task of line detection is reduced to the task of finding isolated peaks in a Sobel image. An experimental comparison is made between these two algorithms and third algorithm taken from the literature and based on the Hough transform

    Effect of Addition of PET in the Thermal Properties of Polymer-Mortar Composite Materials

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    The polymer-mortar composites are often used as low-cost promising materials for preventing or repairing various reinforced concrete structures. The Thermal behavior of the ¶building materials ¶is relevant to any use of concrete or composite, especially in relation to structures where it is desirable to have low thermal conductivity, dimensional stability, high specific heat and little or no decrease of stiffness upon heating. Although much work has been done on the effect of admixture and the mechanical properties of concrete or composite, relatively little work has been done on the thermal conductivity. So, Thermal conductivity (l), thermal resistance (R) and the surface coefficients of transmission (U) of polymer-mortar composites made up of mixtures of polyethylene terephthalate PET waste were measured. To determine the effect of the PET on the thermal conductivity of PET-mortar composites, PET was added as replacement for cement by decreasing the cement weights in the ratios of 2.5%, 5% and 7.5% by weight. The highest thermal conductivity of 1.45 W/mK was observed with the samples containing only plain cement. It decreased with the increase of PET as replacement for cement. The lowest value of thermal conductivity and the surface coefficient of transmission were obtained with the samples prepared with PET waste polymer at 7.5 % replacement of cement. The composites were also observed by DTA, MOP led to the positive identification of the products’. In this way, the results obtained highlight the beneficial effect of waste PET as thermal insulation in comparison with other insulation materials. In addition, the obtained PET-mortar composites would appear to be low-cost materials which would contribute to resolving some of the solid waste problems in addition to conserving energy

    MALADIE DE CASTLEMAN THORACIQUE A LOCALISATION SCISSURALE. A PROPOS D’UN CAS EXCEPTIONNEL

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    Introduction: Castleman’s disease is a benign lymphoid proliferation of unknown etiology. It has two different clinical classifications: localized and multicentric type. Trough a case report of thoracic Castleman’s disease, we will try to define the clinical, radiological and pathological features of this rare disease. Case report: We report a case of 33 years-old woman, presenting a left hilar opacity fortuitously discovered on the chest x-ray. We evoked the diagnosis of hydatid cyst because of our endemic context. During the surgical operation, an inter-lobar mass in intimate contact with the branches of the pulmonary artery was discovered. The tumor was removed completely, and was diagnosed to be the hyalin vascular type of Castleman’s disease histopathologically. Discussion: Thoracic Castleman’s disease is located most commonly in the mediastinum. Interlobar location, such our patient is unusual. Its management is surgical. Three pathologic classifications have been developed: hyalin vascular variant, plasma cell variant and mixed variant. Conclusion: Castleman’s disease is a benign and uncommon etiology of thoracic tumors. The diagnosis is histological after a surgical resection.Introduction : La maladie de Castleman est une prolifération lymphoïde bénigne d’étiologie inconnue. Elle se présente sous forme localisée ou multiviscérale. A travers une observation d’une maladie de Castleman à localisation thoracique, nous rappelons les aspects cliniques, radiologiques et anatomo-pathologiques de cette pathologie rare. Observation : Patiente de 33 ans, ayant été admise au service de chirurgie thoracique pour une opacité hilaire gauche, de découverte fortuite, évoquant un kyste hydatique du poumon gauche, vu notre contexte endémique. La patiente a bénéficié d’une exploration chirurgicale qui a découvert une masse scissurale au contact intime avec les branches de l’artère pulmonaire gauche. Le geste chirurgical a consisté en une résection complète de la tumeur. L’étude anatomopathologique de la pièce opératoire a montré une forme vasculo-hyaline de la maladie de Castleman. Discussion : La localisation médiastinale est la plus fréquente des formes thoraciques de la maladie de Castleman. La localisation scissurale, cas de notre patiente est exceptionnelle. Son traitement est chirurgical. On distingue 3 formes histologiques, la forme vasculo-hyaline, la forme plasmocytaire et la forme mixte. Conclusion : La maladie de Castleman est l’une des étiologies rares et bénignes des tumeurs intrathoraciques. Son diagnostic est anatomo-pathologique après une exérèse chirurgicale

    Semi-Dense 3D Reconstruction with a Stereo Event Camera

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    Event cameras are bio-inspired sensors that offer several advantages, such as low latency, high-speed and high dynamic range, to tackle challenging scenarios in computer vision. This paper presents a solution to the problem of 3D reconstruction from data captured by a stereo event-camera rig moving in a static scene, such as in the context of stereo Simultaneous Localization and Mapping. The proposed method consists of the optimization of an energy function designed to exploit small-baseline spatio-temporal consistency of events triggered across both stereo image planes. To improve the density of the reconstruction and to reduce the uncertainty of the estimation, a probabilistic depth-fusion strategy is also developed. The resulting method has no special requirements on either the motion of the stereo event-camera rig or on prior knowledge about the scene. Experiments demonstrate our method can deal with both texture-rich scenes as well as sparse scenes, outperforming state-of-the-art stereo methods based on event data image representations.Comment: 19 pages, 8 figures, Video: https://youtu.be/Qrnpj2FD1e

    Identifying and mitigating residual vibrations in wave-based control of lumped, flexible systems

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    The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Wave-based control (WBC) is a technique for motion control of under-actuated flexible sys-tems. It envisages actuator motion as launching a motion wave into the system, while simulta-neously absorbing any wave returning from the system. For rest-to-rest motion the net launch displacement is set at half the target displacement. In absorbing the returning wave and vibra-tions, WBC moves the system the remaining distance to the target, with zero steady-state error. The focus of this paper is on very small residual vibrations around the target position which can endure for a long time after arrival at target. This issue was discovered through a recent devel-opment within WBC context on controlling complex two-dimensional, mass-spring, beam-like arrays. To date their existence has been unidentified. This paper investigates and interprets the nature of these vibrations, explains and identifies them based on wave ideas, and finally offers a new wave-based approach to mitigate or suppress them. It also discusses their implication, not just for WBC but for the general problem of control of flexible systems

    Effect of incorporating PVC waste as aggregate on the physical, mechanical, and chloride ion penetration behavior of concrete

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    WOS:000348658700004International audienceWith the growing needs for resource materials and the environmental protection requirements associated with sustainable development, it has become necessary to study all the possibilities of reusing and recycling industrial wastes and by-products, especially in the field of civil engineering. In the work presented here, non-biodegradable plastic aggregates made of polyvinylchloride (PVC) waste, obtained from scrapped PVC pipes, were used in partial replacement of conventional aggregates in concrete. For this purpose, a number of laboratory prepared concrete mixes were tested, in which natural sand and coarse aggregates were partially replaced by PVC plastic waste aggregates in the proportions of 30, 50, and 70% by volume (granular classes 0/3 and 3/8). Fresh concrete mixtures were tested for workability and density, and hardened concrete specimens were used to investigate compressive strength, ultrasonic wave velocity, and resistance to chloride ion penetration. The results of the laboratory study showed that concrete made with 50 and 70% of recycled PVC aggregates fell into the category of structural lightweight concrete in terms of unit weight and strength properties. This study gave quite encouraging results and opened up a new way of recycling PVC waste as a lightweight aggregate in concrete
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