Examinando por Materia "Modelado geométrico"
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Ítem Boundary Representation of Anatomical Features(2002) Ruíz, Óscar E.; Karangelis, Grigorios; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn Simulationen für Bestrahlungstherapieplanung und andere medizinischen und bioingenieur wissenschaftlichen Anwendungen hat man traditionellerweise die anatomischen Eigenschaften mittels volumenbasierten Techniken angezeigt -- Trotzdem, während der Bedarf an Behandlung, Organsimulation und Erzeugung von Prothese präziser wird, reicht es nicht die Menge und die Position von solchen Features zu wissen, sondern auch Detailstufen, die vergleichbar sind zu denjenigen, die man für ingenieurwissenschaftliche Techniken verwendet (finite element analysis, rapid prototyping, Herstellung, usw.) -- Dieser Artikel präsentiert Bemühungen und Ergebnisse in der Anwendung von computerunterstützten geometrischen Algorithmen auf biomedizinischen Applikationen, wobei diese Algorithmen sich ursprünglich auf die Begrenzung von Formen gerichtet haben, die auf Planarmustern von anatomischen Zielregionen basiertenPublicación Computational Geometry in Medical Applications(Universidad EAFIT, 2016) Cortés Acosta, Camilo Andrés; Ruíz Salguero, Óscar Eduardo; Flórez Esnal, JuliánÍtem Computational geometry in the preprocessing of point clouds for surface modeling(1998) Ruíz, O.E.; Posada, J.L.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn Computer Aided Geometric Design ( CAGD ) the automated fitting of surfaces to massive series of data points presents several difficulties: (i) even the formal definition of the problem is ambiguous because the mathematical characteristics (continuity, for example) of the surface fit are dependent on non-geometric considerations, (ii) the data has an stochastic sampling component that cannot be taken as literal, and, (iii) digitization characteristics, such as sampling interval and directions are not constant, etc -- In response, this investigation presents a set of computational tools to reduce, organize and re-sample the data set to fit the surface -- The routines have been implemented to be portable across modeling or CAD servers -- A case study is presented from the footwear industry, successfully allowing the preparation of a foreign, neutral laser digitization of a last for fitting a B-spline surface to it -- Such a result was in the past attainable only by using proprietary software, produced by the same maker of the digitizing hardwareÍtem Coupling Terrain and Building Database Information for Ray-Tracing Applications(2003) Fontán, F.P.; Ruíz S., O.E.; Peña, S.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn this paper a methodology for the combination and integration into a single data base of terrain and building data is presented -- This study is justified if ray-tracing techniques are to be used in propagation and channel modeling studies -- Usually terrain is available in grid or elevation form while building information is normally facet-oriented -- Ray-tracing (RT) techniques deal with flat facets and straight edges, if possible in triangular format -- To allow the use of RT on urban areas over irregular terrain a common format made up of facets and edges is therefore needed -- In this article, the procedure to accomplish this data homogeneity is presented -- It is assumed that terrain data is available in two formats: a) grid elevation and b) contour or iso-altitude lines -- Building data is assumed available in plant, polygonal planar contour form, a primitive and yet widely used format which is yet to be transformed into 3D entities -- The geometric modeling of joint terrain and building data is further difficuledt because union of surface objects (even after achieving a unified format) is undefined from the point of view of 3D boolean operationsÍtem Digital material laboratory: Wave propagation effects in open-cell aluminium foams(Elsevier, 2012-09) Saenger, E.H.; Uribe, D.; Jänicke, R.; Ruíz, O.; Steeb, H.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis paper is concerned with numerical wave propagation effects in highly porous media using digitized images of aluminum foam -- Starting point is a virtual material laboratory approach -- The Aluminum foam microstructure is imaged by 3D X-ray tomography -- Effective velocities for the fluid-saturated media are derived by dynamic wave propagation simulations -- We apply a displacement-stress rotated staggered fnite-difference grid technique to solve the elastodynamic wave equation -- The used setup is similar to laboratory ultrasound measurements and the computed results are in agreement with our experimental data -- Theoretical investigations allow to quantify the influence of the interaction of foam and fluid during wave propagation – Together with simulations using an artificial dense foam we are able to determine the tortuosity of aluminum foamÍtem Estimation of large domain Al foam permeability by Finite Difference methods(WILEY-VCH Verlag, 2013) Osorno, María; Steeb, Holger; Uribe, David; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEClassical methods to calculate permeability of porous media have been proposed mainly for high density (e.g. granular) materials -- These methods present shortcomings in high porosity, i.e. high permeability media (e.g. metallic foams) -- While for dense materials permeability seems to be a function of bulk properties and occupancy averaged over the volume, for highly porous materials these parameters fail to predict it -- Several authors have attacked the problem by solving the Navier-Stokes equations for the pressure and velocity of a liquid flowing through a small domain (Ωs) of aluminium foam and by comparing the numerical results with experimental values (prediction error approx. 9%) -- In this article, we present calculations for much larger domains (ΩL) using the Finite Difference (FD) method, solving also for the pressure and velocity of a viscous liquid flowing through the Packed Spheres scenario -- The ratio Vol(ΩL)/Vol(Ωs) is around 103 -- The comparison of our results with the Packed Spheres example yields a prediction error of 5% for the intrinsic permeability -- Additionally, numerical permeability calculations have been performed for Al foam samples -- Our geometric modelling of the porous domain stems from 3D X-ray tomography, yielding voxel information, which is particularly appropriate for FD -- Ongoing work concerns the reduction in computing times of the FD method, consideration of other materials and fluids, and comparison with experimental dataÍtem FEA-driven Geometric Modelling for Meshless Methods(Springer Paris, 2005-11) Ruíz, Óscar; Granados, Miguel; Cadavid, Carlos; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEOptimized Boolean Operations against orthogonal Fixed Grids (FG) for 2-manifold construction in quasi-meshless methods for Finite Element Analysis are presented -- A Piecewise Linear (PL) or Boundary Representation (B-Rep) B is assumed to be the boundary of a solid S ⊂ R3 -- On the other hand, R3 is partitioned into a 3-dimensional array of cubic, uniform cells Ci,j,k . Cells Ci,j,k with Ci,j,k ∩ S ≠Φ and Ci,j,k ∩ S ≠ Ci,j,k are particularly important for FG applications -- These are the cells Ci,j,k intersecting B, which happen to be Neither Inside nor Outside (NIO) of B -- The boundary ∂(Ci,j,k ∩ S ) of Ci,j,k ∩ S must be calculated from ∂Ci,j,k and B for a large number of cells Ci,j,k , which makes the normal boolean operations unpractical -- The article illustrates with examples the immersion of B-Rep models in Fixed Grids, visits the downstream results of the stress-strain calculations using FG and explains how this approach is used in Product Design OptimizationÍtem Gabriel-constrained Parametric Surface Triangulation(2008-10) Ruíz, Óscar E.; Cadavid, Carlos; Lalinde, Juan G.; Serrano, Ricardo; Peris-Fajarnés, Guillermo; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe Boundary Representation of a 3D manifold contains FACES (connected subsets of a parametric surface S : R2−R3) -- In many science and engineering applications it is cumbersome and algebraically difficult to deal with the polynomial set and constraints (LOOPs) representing the FACE -- Because of this reason, a Piecewise Linear (PL) approximation of the FACE is needed, which is usually represented in terms of triangles (i.e. 2-simplices) -- Solving the problem of FACE triangulation requires producing quality triangles which are: (i) independent of the arguments of S, (ii) sensitive to the local curvatures, and (iii) compliant with the boundaries of the FACE and (iv) topologically compatible with the triangles of the neighboring FACEs -- In the existing literature there are no guarantees for the point (iii) -- This article contributes to the topic of triangulations conforming to the boundaries of the FACE by applying the concept of parameter independent Gabriel complex, which improves the correctness of the triangulation regarding aspects (iii) and (iv) -- In addition, the article applies the geometric concept of tangent ball to a surface at a point to address points (i) and (ii) -- Additional research is needed in algorithms that (i) take advantage of the concepts presented in the heuristic algorithm proposed and (ii) can be proved correctÍtem Geometric and numerical modeling for porous media wave propagation(2014) Uribe, D.; Osorno, M.; Steeb, H.; Saenger, E.H.; Ruíz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEDetermining hydro-mechanical properties of porous materials present a challenge because they exhibit a more complex behaviour than their continuous counterparts -- The geometrical factors such as pore shape, length scale and occupancy play a definite role in the materials characterization -- On the other hand, computational mechanics calculations for porous materials face an intractable amount of data -- To overcome these difficulties, this investigation propose a workflow (Image segmentation, surface triangulation and parametric surface fitting) to model porous materials (starting from a high-resolution industrial micro-CT scan) and transits across different geometrical data (voxel data, cross cut contours, triangular shells and parametric quadrangular patches) for the different stages in the computational mechanics simulations -- We successfully apply the proposed workflow in aluminum foam -- The various data formats allow the calculation of the tortuosity value of the material by using viscoelastic wave propagation simulations and poroelastic investigations -- Future work includes applications for the geometrical model such as boundary elements and iso-geometrical analysis, for the calculation of material propertiesÍtem Geometric modeling in design of naval elements(2003) Ruíz S., Óscar E.; Leiceaga Baltar, Xoán; Rodrígez Pérez, Manuel; Prieto Villar, José; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEBoundary Representations (B-Reps) of actual solid parts are correct from the geometrical and topological points of view -- However, when the solid to model has extreme slender ratios, the rigid rules of the B-Rep force a large number of finite elements required to model the solid interior of a closed shell (also called a 2-manifold without border) -- In the practice, modelling is then pursued by using only a partial shell (2-manifold with border), excluding the “interior” of it -- For the same reasons, other slender elements (trusses or beams) must be modelled as 1-dimensional wires (1-manifolds with border) -- Assumptions are made in both cases to replace the solid model information left aside -- The scenarios in which both 2-manifolds and 1-manifolds must coexist are undesirable from the mathematical point of view, since they render flawed topologies and geometries -- However, in the engineering domain, they are required, and enabled, by replacing the information lost in the modelling with additional kinematic and structural constraints -- These constraints force the 1-manifolds and 2-manifolds to intervene together in the numerical solution, therefore rendering realistic results, without actually coexisting in the geometric model -- These techniques are discussed here and applied to examples of shipbuilding industry, where slender forms and extremely large models are ubiquitousÍtem Topologically consistent partial surface reconstruction from range pictures(2000) Ruíz S., Óscar E.; Neugebauer, Peter; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAESurface or shape reconstruction from 3D digitizations, range pictures play an important role as the sizes and accessibility of the sampled object become intractable -- Range pictures, however, present challenges regarding: (i) recovery of topological structure from geometrical information of a partial view: (ii) inclusion of several or self obstructing objects on the same picture, and (iii) conciliation of partial topological and geometrical information from the individual views into a main model -- Issue (i) and (ii) require introduction of data structures and algorithms able to consistently represent incompleteness and discontinuities in the surface -- Aspect (iii) demands the application of statistical methods to sort redundant e inconsistent information in the overlaps between the individual views -- In this investigation, tasks (i) and (ii) have been undertaken by designing and populating an extended Boundary Representation (B-rep), using equivalence relations that induce partitions on the data sets -- Task (iii) has been carried out by using data processing tools (DigitLAB) that filter, resample, and recover shape from planar digitizations, by applying formalisms of differential topologyÍtem Web based hybrid volumetric visualisation of urban GIS data: Integration of 4D Temperature and Wind Fields with LoD-2 CityGML models(EDP Sciences, 2012) Congote, J.; Moreno, A.; Kabongo, L.; Pérez, J.-L.; San-José, R.; Ruíz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAECity models visualisation, buildings, structures and volumetric information, is an important task in Computer Graphics and Urban Planning -- The different formats and data sources involved in the visualisation make the development of applications a big challenge -- We present a homogeneous web visualisation framework using X3DOM and MEDX3DOM for the visualisation of these urban objects -- We present an integration of different declarative data sources, enabling the utilization of advanced visualisation algorithms to render the models -- It has been tested with a city model composed of buildings from the Madrid University Campus, some volumetric datasets coming from Air Quality Models and 2D layers wind datasets -- Results show that the visualisation of all the urban models can be performed in real time on the Web -- An HTML5 web interface is presented to the users, enabling real time modifications of visualisation parameters