The Experts below are selected from a list of 4887 Experts worldwide ranked by ideXlab platform
G. Unal - One of the best experts on this subject based on the ideXlab platform.
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Active polyhedron: Surface Evolution theory applied to deformable meshes
2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05), 2005Co-Authors: G. Slabaugh, G. UnalAbstract:This paper presents a novel 3D deformable Surface that we call an active polyhedron. Rooted in Surface Evolution theory, an active polyhedron is a polyhedral Surface whose vertices deform to minimize a regional and/or boundary-based energy functional. Unlike continuous active Surface models, the vertex motion of an active polyhedron is computed by integrating speed terms over polygonal faces of the Surface. The resulting ordinary differential equations (ODEs) provide improved robustness to noise and allow for larger time steps compared to continuous active Surfaces implemented with level set methods. We describe an electrostatic regularization technique that achieves global regularization while better preserving sharper local features. Experimental results demonstrate the effectiveness of an active polyhedron in solving segmentation problems as well as Surface reconstruction from unorganized points.
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CVPR (2) - Active polyhedron: Surface Evolution theory applied to deformable meshes
2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05), 2005Co-Authors: G. Slabaugh, G. UnalAbstract:This paper presents a novel 3D deformable Surface that we call an active polyhedron. Rooted in Surface Evolution theory, an active polyhedron is a polyhedral Surface whose vertices deform to minimize a regional and/or boundary-based energy functional. Unlike continuous active Surface models, the vertex motion of an active polyhedron is computed by integrating speed terms over polygonal faces of the Surface. The resulting ordinary differential equations (ODEs) provide improved robustness to noise and allow for larger time steps compared to continuous active Surfaces implemented with level set methods. We describe an electrostatic regularization technique that achieves global regularization while better preserving sharper local features. Experimental results demonstrate the effectiveness of an active polyhedron in solving segmentation problems as well as Surface reconstruction from unorganized points.
R. Keriven - One of the best experts on this subject based on the ideXlab platform.
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Variational principles, Surface Evolution, PDE's, level set methods and the stereo problem
5th IEEE EMBS International Summer School on Biomedical Imaging 2002., 2002Co-Authors: O. Faugeras, R. KerivenAbstract:We present a novel geometric approach for solving the stereo problem for an arbitrary number of images (greater than or equal to 2). It is based upon the definition of a variational principle that must be satisfied by the Surfaces of the objects in the scene and their images. The Euler-Lagrange equations which are deduced from the variational principle provide a set of PDE's which are used to deform an initial set of Surfaces which then move towards the objects to be detected. The level set implementation of these PDE's potentially provides an efficient and robust way of achieving the Surface Evolution and to deal automatically with changes in the Surface topology during the deformation, i.e. to deal with multiple objects. Results of a two dimensional implementation of our theory are presented on synthetic and real images.
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Variational principles, Surface Evolution, PDEs, level set methods, and the stereo problem
IEEE Transactions on Image Processing, 1998Co-Authors: O. Faugeras, R. KerivenAbstract:We present a novel geometric approach for solving the stereo problem for an arbitrary number of images (/spl ges/2). It is based upon the definition of a variational principle that must be satisfied by the Surfaces of the objects in the scene and their images. The Euler-Lagrange equations that are deduced from the variational principle provide a set of partial differential equations (PDEs) that are used to deform an initial set of Surfaces which then move toward the objects to be detected. The level set implementation of these PDEs potentially provides an efficient and robust way of achieving the Surface Evolution and to deal automatically with changes in the Surface topology during the deformations, i.e., to deal with multiple objects. Results of an implementation of our theory also dealing with occlusion and visibility are presented on synthetic and real images.
Marcello Papini - One of the best experts on this subject based on the ideXlab platform.
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Prediction of machined Surface Evolution in the abrasive jet micro-machining of metals
Wear, 2012Co-Authors: S. Ally, Jan K. Spelt, Marcello PapiniAbstract:Abstract Surface Evolution models have been used in the past to accurately predict the cross-sectional profile of micro-channels resulting from the abrasive jet micro-machining (AJM) of glass and polymeric substrates. In the present paper, the models are suitably modified and applied for the first time to the AJM of metallic substrates. The dependence of erosion rate on abrasive jet inclination angle was measured for aluminum 6061-T6, Ti–6Al–4V alloy, and 316L stainless steel using 50 μm Al 2 O 3 abrasive powder launched at an average velocity of 106 m/s. For all three systems the peak erosion rate was found to occur when the jet was inclined between 20° and 35° relative to the Surface. The AJM etch rate was found to be much lower than that found in glass and polymers, and it was found that a significant amount of particle embedding occurred in the 316L stainless steel. When the erosion data were used in an AJM Surface Evolution model, the resulting predicted cross-sectional profiles of unmasked and masked channels were in reasonable agreement with the measured profiles up to an aspect ratio (channel depth/width) of 1.25. The results demonstrate that Surface Evolution during the abrasive jet micro-machining of metals can be predicted using existing models, originally developed for glass and polymers.
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Modelling of Surface Evolution in abrasive jet micro-machining including particle second strikes: A level set methodology
Journal of Materials Processing Technology, 2012Co-Authors: T. Burzynski, Marcello PapiniAbstract:Abstract A previous implementation of narrow band level set methodology for the modelling of the Surface Evolution of masked features in abrasive jet micro-machining (AJM) including the effect of mask erosive wear was extended to include the effect of particle second strikes. The model uses a ray tracing/node tracking algorithm to allow the prediction of the effect of particle ricochets from the mask edges and the sidewalls of the machined feature on the resulting Surface Evolution of high aspect ratio features. Using the model, for the first time, the prediction of the particle second strike effects from inclined masked features is made possible. When compared to previous models that did not account for mask wear and second strike effects, the present model significantly improved the prediction of measured masked micro-channels machined using AJM in glass. When compared to previous particle tracking computer simulations, the present model was found to have a much shorter execution time, and in some cases also showed an improved prediction. The model can be useful in predicting the feature shape in the AJM of brittle targets for aspect ratios greater than 1, and hence for the micro-fabrication of microfluidic and MEMS devices.
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A level set methodology for predicting the Surface Evolution of inclined masked micro-channels resulting from abrasive jet micro-machining at oblique incidence
International Journal of Machine Tools & Manufacture, 2011Co-Authors: T. Burzynski, Marcello PapiniAbstract:Abstract A novel implementation of narrow band level set methods (LSM) was used to predict the Surface Evolution of inclined masked micro-channels in glass and poly-methyl-methacrylate (PMMA) made using abrasive jet micro-machining (AJM) at oblique incidence. The resulting inclined PMMA channels had straight walls and rectangular bottoms, while the glass profiles had curved walls and rounded bottoms. The inclined micro-channels rapidly become multi-valued, and the Hamilton–Jacobi type partial differential equation describing their Evolution cannot be solved using traditional analytical or numerical techniques. To predict the decrease in particle flux at the mask edge, a previously developed analytical model was generalized from the normal to the oblique incidence case. The local Surface velocity function was non-convex, necessitating the development of a modified extension velocity methodology to address the problem of grid ‘visibility’ of the particle flux. The agreement between LSM-predicted and measured Surface Evolution was fair. Since in its current form the model ignores particle ‘second-strike effects’ and mask wear, it is best suited to predict AJM Surface Evolution in ductile targets where mask wear is minimal, and not for brittle targets (e.g. glass). Since AJM at oblique incidence can be used to machine three-dimensional suspended micro-structures, the work has important implications for the micro-fabrication of novel MEMS and microfluidic devices.
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Level set methods for the modelling of Surface Evolution in the abrasive jet micromachining of features used in MEMS and microfluidic devices
Journal of Micromechanics and Microengineering, 2010Co-Authors: T. Burzynski, Marcello PapiniAbstract:The time-dependent Evolution of an abrasive jet micro-machined Surface is described by a partial differential equation which is difficult to solve using traditional analytical or numerical techniques. As a result, traditional Surface advancement models can give incorrect predicted profile depths. In this work, level set methods were used to develop novel models of the abrasive jet machined Surface Evolution of unmasked and masked channels and holes in glass and polymethylmethacrylate. The level set-predicted eroded profiles were compared to those experimentally obtained, as well as to those predicted by existing analytical and computer models. For the majority of cases, the level set-predicted Surface advancement was closer to the measured profiles than those predicted by existing analytical and computer models. The work demonstrates the potential of the level set methodology as a generally applicable tool for the prediction of abrasive jet machined Surface profiles, and provides a foundation for future simulation of more complex abrasive jet micro-machining operations.
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Surface Evolution models for abrasive jet micromachining of holes in glass and polymethylmethacrylate (PMMA)
Journal of Micromechanics and Microengineering, 2007Co-Authors: Amin Ghobeity, Marcello Papini, H. Getu, Jan K. SpeltAbstract:Models are presented to predict the shape and size of masked and unmasked holes machined in glass and polymethymethacrylate (PMMA) using abrasive jet micromachining (AJM). An existing AJM Surface Evolution model for brittle materials was modified by introducing a curvature-dependent smoothing (viscosity) term to the Surface velocity function, greatly improving the prediction of hole shape in cases where the erosive power creates a sharp corner. The modified model predicts hole profiles that agree well with both experiments and a computer simulation. The profiles of holes machined in PMMA using a mask are also compared with the predictions of a recently developed theoretical model for the AJM of ductile materials. There is good agreement in both shape and depth with a maximum error of 13% up to an aspect ratio of 0.6 in PMMA.
M Papini - One of the best experts on this subject based on the ideXlab platform.
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Surface Evolution models for abrasive slurry jet micro machining of channels and holes in glass
Wear, 2014Co-Authors: H Nouraei, K Kowsari, J K Spelt, M PapiniAbstract:Abstract Abrasive slurry jet micro-machining (ASJM) uses a jet of abrasive slurry to erode features with relatively high resolution without the need for a patterned mask. The present study investigated the ability of a Surface Evolution model to predict the profiles of micro-channels and holes machined in borosilicate glass with a newly developed ASJM system. The system could produce micro-channels with depth and width variations along their length of less than 3%, and a channel-to-channel repeatability within 5%. The fundamental erosion rate of the borosilicate glass was measured as a function of impact angle using a slurry of water mixed with a low concentration of 10 and 25 µm nominal diameter aluminum oxide particles. This erosion rate-impact angle relationship was used in an existing model developed previously for the abrasive air jet micro-machining of brittle materials. The results demonstrated that, despite the differences in abrasive flow patterns between air and slurry based systems, the Surface Evolution model accurately predicted the profiles of micro-channels with a maximum error of 7% for aspect ratios (depth/width) of up to 5. The predicted profiles of holes were also in reasonable agreement with a maximum error of 14% for aspect ratios close to 1.
G. Slabaugh - One of the best experts on this subject based on the ideXlab platform.
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Active polyhedron: Surface Evolution theory applied to deformable meshes
2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05), 2005Co-Authors: G. Slabaugh, G. UnalAbstract:This paper presents a novel 3D deformable Surface that we call an active polyhedron. Rooted in Surface Evolution theory, an active polyhedron is a polyhedral Surface whose vertices deform to minimize a regional and/or boundary-based energy functional. Unlike continuous active Surface models, the vertex motion of an active polyhedron is computed by integrating speed terms over polygonal faces of the Surface. The resulting ordinary differential equations (ODEs) provide improved robustness to noise and allow for larger time steps compared to continuous active Surfaces implemented with level set methods. We describe an electrostatic regularization technique that achieves global regularization while better preserving sharper local features. Experimental results demonstrate the effectiveness of an active polyhedron in solving segmentation problems as well as Surface reconstruction from unorganized points.
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CVPR (2) - Active polyhedron: Surface Evolution theory applied to deformable meshes
2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05), 2005Co-Authors: G. Slabaugh, G. UnalAbstract:This paper presents a novel 3D deformable Surface that we call an active polyhedron. Rooted in Surface Evolution theory, an active polyhedron is a polyhedral Surface whose vertices deform to minimize a regional and/or boundary-based energy functional. Unlike continuous active Surface models, the vertex motion of an active polyhedron is computed by integrating speed terms over polygonal faces of the Surface. The resulting ordinary differential equations (ODEs) provide improved robustness to noise and allow for larger time steps compared to continuous active Surfaces implemented with level set methods. We describe an electrostatic regularization technique that achieves global regularization while better preserving sharper local features. Experimental results demonstrate the effectiveness of an active polyhedron in solving segmentation problems as well as Surface reconstruction from unorganized points.
