Examinando por Autor "Ruíz, Oscar"
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Ítem Analytical method for the kinetostatic analysis of the second-class RRR ASSUR Group allowing for friction in the kinematic pairs(SciELO Brasil, 2010) Durango, Sebastián; Calle, Gabriel; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe calculation of forces in the kinematic pairs of mechanisms by inverse dynamics is usually performed without friction considerations -- In practice, when examination of articulated mechanisms takes into account friction, the solution of the inverse dynamics results in a complex procedure -- If a modular approach for the inverse dynamics is used, then exact solutions are available, but not necessarily are practical -- For example, the analytical solution for a second-class first-type Assur group is a 16th degree equation -- Previous researches proposed an approximated but practical (graphical) method to calculate the forces on the kinematic pairs taking into account the friction forces -- In this article, an analytical interpretation of the Artobolevski approximated method is developed for the second-class Assur group with three rotational pairs -- The final results for the reactions calculated with the implemented method present a good approximation with respect to the graphical solution -- Future work should consider friction forces not only in second-class groups with rotational joints, but also in second-class groups with prismatic joints and high-class Assur groupsÍtem Bi-curve and multi-patch smoothing with application to the shipyard industry(2007) Leiceaga, Xoán A.; Ruíz, Oscar; Vanegas, Carlos; Soto, Eva; Prieto, José; Rodríguez, Manuel; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEAlgorithms are proposed and implemented in a commercial system which allow for the C1-continuity matching between adjacent B-spline curves and B-spline patches -- These algorithms only manipulate the positions of the control points, therefore respecting the constraint imposed by the sizes of the available commercial steel plates -- The application of the algorithms respect the initial hull partition made by the designers and therefore the number and overall shape and position of the constitutive patches remains unchanged -- Algorithms were designed and tested for smoothing the union of (a) two B-spline curves sharing a common vertex, (b) two B-spline surfaces sharing a common border, and (c) four B-spline surfaces sharing a common vertex -- For this last case, an iterative heuristic degreeof-freedom elimination algorithm was implemented -- Very satisfactory results were obtained with the application of the presented algorithms in shipyards in SpainÍtem Evaluation of interest point detectors for image information extraction(2012) Barandiaran, Iñigo; Goenetxea, Jon; Congote, John; Graña, Manuel; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEInterest points extraction and matching is a common task in many computer vision based application, which are used in different domains, such as 3D reconstruction, object recognition, or tracking -- We present an evaluation of current state of the art about interest point extraction algorithms to measure several parameters, such as detection quality, invariance to rotation and scale transformation, and computational efficiencyÍtem Extending Marching Cubes with Adaptative Methods to obtain more accurate iso-surfaces(Springer Berlin Heidelberg, 2010) Congote, John; Moreno, Aitor; Barandiaran, Iñigo; Barandiaran, Javier; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis work proposes an extension of the Marching Cubes algorithm, where the goal is to represent implicit functions with higher accuracy using the same grid size -- The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved -- After each iteration, the difference between the implicit and the explicit representations is reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more accurate, as the results shall confirm -- The proposed algorithm corrects some topological problems that may appear in the discretization process using the original gridÍtem Hessian Eigenfunctions for Triangular Mesh Parameterization(SCITEPRESS, 2016) Mejía, Daniel; Ruíz, Oscar; Cadavid, Carlos A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEHessian Locally Linear Embedding (HLLE) is an algorithm that computes the nullspace of a Hessian functional H for Dimensionality Reduction (DR) of a sampled manifold M -- This article presents a variation of classic HLLE for parameterization of 3D triangular meses -- Contrary to classic HLLE which estimates local Hessian nullspaces, the proposed approach follows intuitive ideas from Differential Geometry where the local Hessian is estimated by quadratic interpolation and a partition of unity is used to join all neighborhoods -- In addition, local average triangle normals are used to estimate the tangent plane TxM at x ∈ M instead of PCA, resulting in local parameterizations which reflect better the geometry of the surface and perform better when the mesh presents sharp features -- A high frequency dataset (Brain) is used to test our algorithm resulting in a higher rate of success (96.63%) compared to classic HLLE (76.4%)Ítem HexFlex Mechanism Modeling by Design of Computer Experiments(Springer London, 2010-04) Acosta, Diego; Restrepo, David; Ruíz, Oscar; Durango, Sebastián; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAECompliant mechanisms are an instance of mechanical devices designed to transfer or transmit motion, force, or energy from specified input ports to output ports by elastic deformation of at least one of its members -- The main advantage of compliant mechanisms with respect to traditional rigid-link mechanism is that fewer parts, fewer assembly process and no lubrication are required -- The HexFlex is a parallel compliant mechanism for nano-manipulating that allows six degrees of freedom of its moving stage -- This mechanism was designed for high precisión an repeatability -- This article presents a methodology to model compliant mechanisms behavior under quasi-static conditions using computer experiments, reducing costs of experimentation of product development -- The methodology is used to establish a mathematical model that relates the actuator forces at the input ports with the position and orientation the end-effector stage of the Hexflex -- This mathematical model has direct application in model-based control as an advantage with respect to other models, e.g. Finite Element Method -- The mathematical model of the HexFlex is achieved using metamodels -- The term methamodel is used to represent a simplified and efficient mathematical model of unknown phenomenon or computer codes – The metamodel of the HexFlex is performed from virtual analyses made using the Finite Element Method (FEM) -- Simulations of the metamodel were made founding good accuracy with respect to the virtual experimentsÍtem Interactive visualization of volumetric data with WebGL in real-time(ACM, 2011-06) Congote, John; Kabongo, Luis; Moreno, Aitor; Segura, Alvaro; Posada, Jorge; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents and discusses the implementation of a volume rendering system for the Web, which articulates a large portion of the rendering task in the client machine -- By placing the rendering emphasis in the local client, our system takes advantage of its power, while at the same time eliminates processing from unreliable bottlenecks (e.g. network) -- The system developed articulates in efficient manner the capabilities of the recently released WebGL standard, which makes available the accelerated graphic pipeline (formerly unusable) -- The dependency on specially customized hardware is eliminated, and yet efficient rendering rates are achieved -- The Web increasingly competes against desktop applications in many scenarios, but the graphical demands of some of the applications (e.g. interactive scientific visualization by volume rendering), have impeded their successful settlement in Web scenarios -- Performance, scalability, accuracy, security are some of the many challenges that must be solved before visualWeb applications popularize -- In this publication we discuss both performance and scalability of the volume rendering by WebGL ray-casting in two different but challenging application domains: medical imaging and radar meteorologyÍtem Microscale investigations of highfrequency wave propagation through highly porous media(WILEY-VCH Verlag, 2012-12-03) Uribe, David; Saenger, Erik; Jänicke, Ralf; Steeb, Holger; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEWave propagation in highly porous materials has a well established theoretical background -- Still there are parameters which require complex laboratory experimentation in order to find numerical values -- This paper presents an effective method to calculate the tortuosity of aluminum foam using numerical simulations -- The work flow begins with the acquisition of the foam geometry by means of a micro-CT scanner and further image segmentation and analysis -- The elastodynamic wave propagation equation is solved using a velocity-stress rotated staggered finite-difference technique -- The effective wave velocities are calculated and using the fluid and, aluminum effective properties, the tortuosity is determinedÍtem ReWeb3D: enabling desktop 3D applications to run in the web(ACM, 2013) Glander, Tassilo; Moreno, Aitor; Aristizábal, Mauricio; Congote, John; Posada, Jorge; García-Alonso, Alejandro; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAECurrently, 3D rendering is accessible within Web browsers through open standards such as WebGL, X3D, and X3DOM -- At the same time, there is wealth of mature desktop software which comprises algorithms, data structures, user interfaces, databases, etc -- It is a challenge to reuse such desktop software using the Web visualization resources -- In response to this challenge, this article presents a novel framework, called ReWeb3D, which minimizes the redevelopment for migration of existing 3D applications to the Web -- The redeployed application runs on a Web server -- ReWeb3D captures lowlevel graphic calls including geometry, texture, and shader programs -- The captured content is then served as a WebGLenabled web page that conveys full interactivity to the client -- By splitting the graphics pipeline between client and server, the workload can be balanced, and highlevel implementation details and 3D content are hidden -- The feasibility of ReWeb3D has been tested with applications which use OpenSceneGraph as rendering platform -- The approach shows good results for applications with large data sets (e.g. geodata), but is less suited for applications intensive in animations (e.g. games)Ítem Volume Ray Casting in WebGL(Intech Open, 2012) Congote, John; Kabongo, Luis; Moreno, Aitor; Segura, Alvaro; Beristain, Andoni; Posada, Jorge; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE