The Experts below are selected from a list of 69603 Experts worldwide ranked by ideXlab platform
Romain Aubry - One of the best experts on this subject based on the ideXlab platform.
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ensuring a smooth transition from semi structured Surface boundary layer Mesh to fully unstructured anisotropic Surface Mesh
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Romain AubryAbstract:Anisotropic Surface Mesh is considered in this work. First, a semi-structured boundary layer Surface Mesh is generated to maintain strong normality in the Mesh. Then a fully unstructured anisotropic Mesh completes the final Mesh. In order to get a smooth and coherent anisotropic size distribution, anisotropic sources are used. Boundary layer parameters are therefore perceived from the Mesher through this global anisotropic sizing field. Some anisotropic sources are presented, as well as the algorithm to generate a meaningful anisotropic sizing field corresponding to a distance based sizing field. Some numerical examples illustrate the method.
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a three dimensional parametric Mesher with Surface boundary layer capability
Journal of Computational Physics, 2014Co-Authors: Romain Aubry, B K Karamete, Eric Mestreau, Saikat DeyAbstract:Abstract A novel parametric Surface Meshing technique is presented. Its distinctive feature relies on successive approximations of the CAD geometry through a hierarchical process where geometric information is gathered incrementally. A detailed review of zero- and first-order Surface approximations and their impact on parametric Surface Meshing algorithms is performed. The proposed approach emphasizes the use of three-dimensional information in order to be as independent as possible of the parametrization to overcome limitations of Meshing purely in the parametric plane. The presented technique includes semi-structured boundary-layer Surface Mesh generation which is a critical capability for accurate solutions to flows around geometries that have leading edge features. Numerous examples illustrate the method's robustness and ability to high-quality Meshes for complex CAD geometries.
D.j. Hawkes - One of the best experts on this subject based on the ideXlab platform.
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Endoluminal Surface registration for CT colonography using Haustral Fold Matching
Medical Image Analysis, 2013Co-Authors: D.j. HawkesAbstract:Computed Tomographic (CT) colonography is a technique used for the detection of bowel cancer or potentially precancerous polyps. The procedure is performed routinely with the patient both prone and supine to differentiate fixed colonic pathology from mobile faecal residue. Matching corresponding locations is difficult and time consuming for radiologists due to colonic deformations that occur during patient repositioning. We propose a novel method to establish correspondence between the two acquisitions automatically. The problem is first simplified by detecting haustral folds using a graph cut method applied to a curvature-based metric applied to a Surface Mesh generated from segmentation of the colonic lumen. A virtual camera is used to create a set of images that provide a metric for matching pairs of folds between the prone and supine acquisitions. Image patches are generated at the fold positions using depth map renderings of the endoluminal Surface and optimised by performing a virtual camera registration over a restricted set of degrees of freedom. The intensity difference between image pairs, along with additional neighbourhood information to enforce geometric constraints over a 2D parameterisation of the 3D space, are used as unary and pair-wise costs respectively, and included in a Markov Random Field (MRF) model to estimate the maximum a-posteriori fold labelling assignment. The method achieved fold matching accuracy of 96.0% and 96.1% in patient cases with and without local colonic collapse. Moreover, it improved upon an existing Surface-based registration algorithm by providing an initialisation. The set of landmark correspondences is used to non-rigidly transform a 2D source image derived from a conformal mapping process on the 3D endoluminal Surface Mesh. This achieves full Surface correspondence between prone and supine views and can be further refined with an intensity based registration showing a statistically significant improvement (p
Eric L. Miller - One of the best experts on this subject based on the ideXlab platform.
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Three-Dimensional Surface Mesh Segmentation Using Curvedness-Based Region Growing Approach
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2007Co-Authors: Anupama Jagannathan, Eric L. MillerAbstract:A new parameter-free graph-morphology-based segmentation algorithm is proposed to address the problem of partitioning a 3D triangular Mesh into disjoint subMeshes that correspond to the physical parts of the underlying object. Curvedness, which is a rotation and translation invariant shape descriptor, is computed at every vertex in the input triangulation. Iterative graph dilation and morphological filtering of the outlier curvedness values result in multiple disjoint maximally connected subMeshes such that each subMesh contains a set of vertices with similar curvedness values, and vertices in disjoint subMeshes have significantly different curvedness values. Experimental evaluations using the triangulations of a number of complex objects demonstrate the robustness and the efficiency of the proposed algorithm and the results prove that it compares well with a number of state-of-the-art Mesh segmentation algorithms.
Gabor Szekely - One of the best experts on this subject based on the ideXlab platform.
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high quality Surface Mesh generation for multi physics bio medical simulations
International Conference on Conceptual Structures, 2007Co-Authors: D Szczerba, Robert Mcgregor, Gabor SzekelyAbstract:Manual Surface reconstruction is still an everyday practice in applications involving complex irregular domains, necessary for modeling biological systems. Rapid development of biomedical imaging and simulation, however, requires automatic computations involving frequent re-Meshing of (r)evolving domains that human-driven generation can simply no longer deliver. This bottleneck hinders the development of many applications of high social importance, like computational physiology or computer aided medicine. While many commercial packages offer Mesh generation options, these depend on high quality input, which is rarely available when depending on image segmentation results. We propose a simple approach to automatically recover a high quality Surface Mesh from low-quality, oversampled and possibly non-consistent inputs that are often obtained via 3-D acquisition systems. As opposed to the majority of the established Meshing techniques, our procedure is easy to implement and very robust against damaged or partially incomplete, inconsistent or discontinuous inputs.
Rao V Garimella - One of the best experts on this subject based on the ideXlab platform.
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polygonal Surface Mesh optimization
Engineering With Computers, 2004Co-Authors: Rao V Garimella, Mikhail ShashkovAbstract:A procedure has been developed to improve polygonal Surface Mesh quality while maintaining the essential characteristics of the discrete Surface. The Surface characteristics are preserved by repositioning Mesh vertices so that they remain on the original discrete Surface. The repositioning is performed in a series of triangular-facet-based local parametric spaces. The movement of the Mesh vertices is driven by a nonlinear numerical optimization process. Two optimization approaches are described, one which improves the quality of elements as much as possible and the other which improves element quality but also keeps the new Mesh as close as possible to the original Mesh.
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triangular and quadrilateral Surface Mesh quality optimization using local parametrization
Computer Methods in Applied Mechanics and Engineering, 2004Co-Authors: Rao V Garimella, Mikhail Shashkov, Patrick M KnuppAbstract:A procedure is presented to improve the quality of Surface Meshes while maintaining the essential characteristics of the discrete Surface. The Surface characteristics are preserved by repositioning Mesh vertices in a series of element-based local parametric spaces such that the vertices remain on the original discrete Surface. The movement of the Mesh vertices is driven by a non-linear numerical optimization process. Two optimization approaches are described, one which improves the quality of elements as much as possible and the other which improves element quality but also keeps the new Mesh as close as possible to the original Mesh.
