Examinando por Autor "Ruíz, O."
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Ítem 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 Ellipse-based Principal Component Analysis for Self-intersecting Curve Reconstruction from Noisy Point Sets(Springer Berlin Heidelberg, 2011) Ruíz, O.; Vanegas, C.; Cadavid, C.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAESurface reconstruction from cross cuts usually requires curve reconstruction from planar noisy point samples -- The output curves must form a possibly disconnected 1manifold for the surface reconstruction to proceed -- This article describes an implemented algorithm for the reconstruction of planar curves (1manifolds) out of noisy point samples of a sel-fintersecting or nearly sel-fintersecting planar curve C -- C:[a,b]⊂R→R is self-intersecting if C(u)=C(v), u≠v, u,v∈(a,b) (C(u) is the self-intersection point) -- We consider only transversal self-intersections, i.e. those for which the tangents of the intersecting branches at the intersection point do not coincide (C′(u)≠C′(v)) -- In the presence of noise, curves which self-intersect cannot be distinguished from curves which nearly sel fintersect -- Existing algorithms for curve reconstruction out of either noisy point samples or pixel data, do not produce a (possibly disconnected) Piecewise Linear 1manifold approaching the whole point sample -- The algorithm implemented in this work uses Principal Component Analysis (PCA) with elliptic support regions near the selfintersections -- The algorithm was successful in recovering contours out of noisy slice samples of a surface, for the Hand, Pelvis and Skull data sets -- As a test for the correctness of the obtained curves in the slice levels, they were input into an algorithm of surface reconstruction, leading to a reconstructed surface which reproduces the topological and geometrical properties of the original object -- The algorithm robustly reacts not only to statistical noncorrelation at the self-intersections(nonmanifold neighborhoods) but also to occasional high noise at the nonselfintersecting (1manifold) neighborhoodsÍtem Force-Displacement Model of Compliant Mechanisms using Assur Sub-Chains(2011-06) Durango, S.; Correa, J.; Ruíz, O.; Aristizábal, M.; Restrepo-Giraldo, J.; Achiche, S.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article develops a modular procedure to perform force-displacement modeling of planar flexurebased compliant mechanisms (CMs) -- The procedure is mostly suitable for planar lumped CMs -- To achieve the position analysis of CMs requires: (i) to implement the kinematic analysis as for ordinary mechanisms, (ii) to solve equilibrium problem by means of an static analysis and (iii) to model the flexures behavior through a deflection analysis -- The novel contribution of this article relies on the fact that a division strategy of the CM into Assur subchainsm is implemented, so that any CM subjected to such disaggregation can be accurately modeled -- For this purpose a mathematical model for leaf-spring flexure type is presented and used through this paper -- However any other flexure model can be used instead -- To support the technique, a three Degrees–Of–Freedom (3-DOF) flexure-based parallel mechanism is used as case study -- Results are compared to a Finite Element Analysis (FEA)Ítem 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 functions in computer aided geometric design(Fondo Editorial Universidad EAFIT, 2008-01-01) Ruíz, O.; Cadavid, C.El libro da una visión valiosa en principios para robótica, visión por computador, diseño, manufactura, cinemática y dinámica desde un punto de vista práctico. Al mismo tiempo, mantiene un contacto con las propiedades matemáticas decisivas.Ítem Hardware-accelerated Web Visualization of Vector Fields. Case Study in Oceanic Currents(2012) Aristizábal, Mauricio; Congote, John Edgar; Segura, Álvaro; Moreno, Aitor; Arregui, Harbil; Ruíz, O.Visualization of vector fields plays an important role in research activities nowadays -- Increasing web applications allow a fast, multi-platform and multi-device access to data -- As a result, web applications must be optimized in order to be performed heterogeneously as well as on high-performance as on low capacity devices -- This paper presents a hardware-accelerated scheme for integration-based flow visualization techniques, based on a hierarchical integration procedure which reduces the computational effort of the algorithm from linear to logarithmic, compared to serial integration methodologies -- The contribution relies on the fact that the optimization is only implemented using the graphics application programming interface (API), instead of requiring additional APIs or plug-ins -- This is achieved by using images as data storing elements instead of graphical information matrices -- A case study in oceanic currents is implementedÍtem Symmetrical Observability of Kinematic Parameters in Symmetrical Parallel Mechanisms(Editora Edgard Blücher Ltda., 2014-05) Durango, S.; Restrepo, D.; Ruíz, O.; Restrepo-Giraldo, J.; Achiche, S.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents an application of symmetry group theory in kinematic identification of parallel mechanisms of nlegs legs -- Kinematic Identification implies the estimation of the actual geometrical parameters (as opposed to nominal ones) of a physical mechanism -- For a symmetric mechanism, KI requires configuring sets of leg positions with symmetrical observability – This article presents as main contributions: (i) a conjecture that allows mapping the symmetries of the mechanism into the active-joint workspace, (ii) a set of necessary conditions to express leg parameters in coordinate systems which allow symmetrical observability, and (iii) a procedure for exploiting symmetries in pose selection for kinematic identification of symmetrical parallel mechanisms -- For the kinematic identification itself, we adopt a divide-and-conquer (DC) identification protocol -discussed by us in another publication- in which each leg of the mechanism is independently identified by using the inverse calibration method -- In this article we emphasize how to exploit the symmetries existent in (nlegs − 1) legs of the parallel mechanism allowing to apply to other legs the symmetry-transformed sample protocol used for the kinematic identification of a reference leg -- The symmetrical observability of sets of leg parameters allows to reduce the costs of the pose selection procedure by a factor of (1/nlegs) compared to a complete DC procedure in which the poses of each leg are selected independently -- The pose selection is carried out only for the reference leg -- For the (nlegs−1) remaining legs the poses are dictated by symmetry operations performed onto the poses of the reference leg -- An application of the symmetrical observability is presented through the simulated kinematic identification of a 3RRR symmetrical parallel mechanismÍtem 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