324 research outputs found

    Tolosa-Hunt syndrome mimicking cavernous sinus tumor

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    Diatomita para prevenção de pragas em silos

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    Orientador : Francisco RosaMonografia (especialização) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Curso de Especialização em Economia e Meio AmbienteInclui referência

    On the evaluation of photogrammetric methods for dense 3D surface reconstruction in a metrological context.

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    This paper discusses a methodology to evaluate the accuracy of recently developed image-based 3D modelling techniques. So far, the emergence of these novel methods has not been supported by the definition of an internationally recognized standard which is fundamental for user confidence and market growth. In order to provide an element of reflection and solution to the different communities involved in 3D imaging, a promising approach is presented in this paper for the assessment of both metric quality and limitations of an open-source suite of tools (Apero/MicMac), developed for the extraction of dense 3D point clouds from a set of un- ordered 2D images. The proposed procedural workflow is performed within a metrological context, through inter-comparisons with \u2018reference\u2019 data acquired with two hemispherical laser scanners, one total station, and one laser tracker. The methodology is applied to two case studies, designed in order to analyse the software performances in dealing with both outdoor and environmentally controlled conditions, i.e. the main entrance of Cath\ue9drale de la Major (Marseille, France) and a custom-made scene located at National Research Council of Canada 3D imaging Metrology Laboratory (Ottawa). Comparative data and accuracy evidence produced for both tests allow the study of some key factors affecting 3D model accuracy

    E-heritage : the future for integrated applications in cultural heritage

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    A number of factors are combining to change the structure and contents of documentation of cultural heritage: 1) the exponential growth in data generated by imaging techniques makes it possible for a site or an artifact to be recorded at a resolution of over 16 megapixels and at a density of several hundred million cloud points; 2) high-resolution imaging is becoming more affordable and/or available; 3) the economics and legal constraints of conservation practice are gradually pushing towards more stringent documentation standards; 4) improved communications infrastructure and mobile computing facilities are changing the way that data is recorded, processed, stored and – inevitably - used; 5) increasingly available computerized expert systems will be integrated into the very systems that conservators and documentation specialists carry around with them or access on a daily basis; 6) the advent of web-based systems will afford super-computer processing power and large-system database handling to the documentation specialist and the conservator in the field and permit greater flexibility for teleworking; 7) Computerised Project-based Management techniques will gradually spread from the realm of large institutions to SME’s and individual practitioners making digital image processing in architecture and archaeology more akin to the exchange of engineering drawings in automobile design industry. 8) The availability of cheap local or distributed processing power means that most of the above advantages will be present in both developed and developing countries. This paper explores. e-heritage as an integrated project which aims at providing a seamless yet structurally and inherently up-gradeable technological platform for all activities within cultural heritage conservation and management.peer-reviewe

    DIGITAL 3D RECONSTRUCTION OF SCROVEGNI CHAPEL WITH MULTIPLE TECHNIQUES

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    The use of 3D digitization and modeling in documenting heritage sites has increased significantly over the past few years. This is mainly due to advances in laser scanning techniques, 3D modeling software, image-based-modeling techniques, computer power, and virtual reality. There are many approaches currently available. The most common remains based on surveying and CAD tools and/or traditional photogrammetry with control points and a human operator. This is very time consuming and can be tedious and lingering effort. Lately, modeling methods based on laser scanners data and more automated image-based techniques are becoming available. Initially, the goal of this work was to discuss advantages and disadvantages of those 3D modeling techniques applied to a cultural heritage building, i.e. the Scrovegni chapel in Padova, Italy, by comparing the geometry and visual quality of related models for asbuilt documentation, restoration and interactive visualization purposes. To this aim the chapel was imaged with a color digital camera and surveyed with both different kind of laser scanners and traditional topographic instrument. Unfortunately due to the long time wasted before all requested laser scanners were available from the dealers and difficulties encountered during the subsequent 3D modeling, due to the bad quality of some range data, at the present date only the range data model is available. Therefore in this paper we will discuss only the results obtained by generating a unique 3D model of the Scrovegni Chapel using four different laser scanners: Cyrax 2500, Mensi GS 100, Optech ILRIS 3D and Riegl LMS-Z210. In order to assess the performance of these sensors when applied for cultural heritage survey, data quality, geometric accuracy, sensor noise, ease of use, speed of data collection, will be the topics of this work. 1

    Verification of micro-scale photogrammetry for smooth three-dimensional object measurement

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    By using sub-millimetre laser speckle pattern projection we show that photogrammetry systems are able to measure smooth three-dimensional objects with surface height deviations less than 1 μm. The projection of laser speckle patterns allows correspondences on the surface of smooth spheres to be found, and as a result, verification artefacts with low surface height deviations were measured. A combination of VDI/VDE and ISO standards were also utilised to provide a complete verification method, and determine the quality parameters for the system under test. Using the proposed method applied to a photogrammetry system, a 5 mm radius sphere was measured with an expanded uncertainty of 8.5 μm for sizing errors, and 16.6 μm for form errors with a 95 % confidence interval. Sphere spacing lengths between 6 mm and 10 mm were also measured by the photogrammetry system, and were found to have expanded uncertainties of around 20 μm with a 95 % confidence interval

    A biomimetic study of natural attachment mechanisms: imaging cellulose and chitin part 2

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