Examinando por Materia "Algorithms"
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Ítem 2D shape similarity as a complement for Voronoi-Delone methods in shape reconstruction(PERGAMON-ELSEVIER SCIENCE LTD, 2005-02-01) Ruiz, O.E.; Cadavid, C.A.; Granados, M.; Peña, S.; Vásquez, E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn surface reconstruction from planar cross sections it is necessary to build surfaces between 2D contours in consecutive cross sections. This problem has been traditionally attacked by (i) direct reconstruction based on local geometric proximity between the contours, and (ii) classification of topological events between the cross sections. These approaches have been separately applied with limited success. In case (i), the resulting surfaces may have overstretched or unnatural branches. These arise from local contour proximity which does not reflect global similarity between the contours. In case (ii), the topological events are identified but are not translated into the actual construction of a surface. This article presents an integration of the approaches (i) and (ii). Similarity between the composite 2D regions bounded by the contours in consecutive cross sections is used to: (a) decide whether a surface should actually relate two composite 2D regions, (b) identify the type and location of topological transitions between cross sections and (c) drive the surface construction for the regions found to be related in step (a). The implemented method avoids overstretched or unnatural branches, rendering a surface which is both geometrically intuitive and topologically faithful to the cross sections of the original object. The presented method is a good alternative in cases in which correct reproduction of the topology of the surface (e.g. simulation of flow in conduits) is more important than its geometry (e.g. assessment of tumor mass in radiation planning). © 2004 Elsevier Ltd. All rights reserved.Ítem Adaptative cubical grid for isosurface extraction(2009) Congote, John; Moreno, Aitor; Barandiaran, Iñigo; Barandiaran, Javier; Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis work proposes a variation on the Marching Cubes algorithm, where the goal is to represent implicit functions with higher resolution and better graphical quality 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 are reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more detailed, as the results shall confirm -- The proposed algorithm corrects some topological problems that may appear in the discretisation process using the original gridÍtem Adaptative cubical grid forisosurface extraction(2009-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis work proposes a variation on the Marching Cubes algorithm, where the goal is to represent implicit functions with higher resolution and better graphical qualiry 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 betvveen the implicit and the explicit representations are reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more detailed, as the results shall confirm. The proposed algorithm corrects some topological problems that may appear in the discretisation process using the original grid.Ítem Algoritmo de estimación de parámetros y modulación de una señal recibida por un SDR(Universidad EAFIT, 2017) Toro Betancur, Verónica; Marulanda Bernal, José IgnacioÍtem Algunas consideraciones del modelo bidominio basado en el método de volúmenes finitos(Universidad EAFIT, 2014) González Galeano, Andrei Alain; Gil Gómez, Javier Hernán; Villegas Gutiérrez, Jairo AlbertoEn este trabajo se estudia la actividad eléctrica cardíaca por medio del modelo del bidominio, el cual, describe el comportamiento eléctrico del tejido cardíaco, basado en el flujo de corriente, la distribución del potencial eléctrico y la conservación de carga y corriente [7], para esto se utiliza el esquema de volúmenes finitos construido sobre mallas rectangulares, donde se realiza un análisis cualitativo de acuerdo a las simulaciones realizadas -- La discretización se enfocará en los algoritmos existentes para ecuaciones elípticas y parabólicas donde su convergencia estará garantizada por la teoría clásica -- En general el modelo de los volúmenes finitos involucra los siguientes pasos (42): a) Descomposición del dominio en volúmenes de control -- b) Formulación de las integrales sobre cada volumen de control -- c) Aproximación de las integrales por integración numérica -- d) Aproximación de las derivadas por algún esquema numérico como el de Euler -- e) Montaje y solución del sistema algebraico discretoÍtem An algorithmic approach for simulating realistic irregular tilings(Universidad EAFIT, 2012) Betancourt Arango, Alejandro; Marín Sánchez, Freddy Hernán; Duque Cardona, Juan CarlosÍtem CUDA capable GPU as an efficient co-processor(Universidad EAFIT, 2010) Ortega Calle, Julián; Trefftz, Christian; Trefftz Gómez, HelmuthÍtem Desprendimiento de rocas en laderas: una guía para la evaluación del riesgo en vías(Universidad EAFIT, 2014) Arango Vélez, Ismael Fernando; Echeverri Ramírez, Gloria ElenaEn este trabajo se presenta una metodología y los lineamientos para evaluar el riesgo en vías por desprendimiento de rocas desde las laderas -- Esta guía puede ser utilizada en las diferentes etapas de un proyecto vial como diseño, construcción, operación y mantenimiento -- El proceso consta de varias fases las cuales se describen detalladamente para facilitar su aplicación -- Estas fases incluyen la clasificación preliminar con base en el diseño geométrico de la vía y la unidad morfogeológica; la obtención de parámetros estructurales del macizo rocoso y datos geotécnicos requeridos para el análisis; la modelación considerando la trayectoria del bloque desprendido y la evaluación con métodos observacionales; la determinación del grado de amenaza y la evaluación del riesgo -- Todas las etapas indicadas se ilustran con el estudio de un caso localÍtem Development of a proteomics-based search engine tool(Universidad EAFIT, 2012) Suárez Durán, Hernando Gustavo; Alzate, Oscar; Londoño, CarolinaÍtem Digital opties tool for multi-purpose experimental applications(2010-01-01) Sierra-Sosa, D.-E.; Angel-Toro, L.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThis work presents the results concerning the application of a Discrete Fresnel Transform algorithm (DFT), which was upgraded for modeling and experimenting with scalar diffraction fields, whose characteristics are analyzed. The MATLAB® software environment was used to implement this algorithm, which allows the user to set the initial conditions, corresponding to the optical information at the input plane, by using a graphic friendly user interface (GUI). Then, by using the DFT algorithm, light propagation from the input to the output plane is achieved. The outputs of the algorithm are the maps corresponding to the 2-D distributions amplitude and phase-modulo 2p, or equivalently, the corresponding real and imaginary parts of the complex analytical field. Also, to assist the analysis, line profiles for these maps are provided. Results allow the user synthesizing Fresnel diffraction in presence of multiple components, like lenses, prisms, diffractive gratings, and holographic elements. Indeed, by implementing a series of successive steps, applications like image forming and spatial filtering can be demonstrated. The basis of the algorithm's architecture and some typical results, which closely resemble those from the experiments, are presented.Ítem Dynamic server allocation in virtual environments, using quadtrees for dynamic space partition(2003-01-01) Restrepo, A.; Montoya, A.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las ComunicacionesIn actual applications of virtual environments, one of the problems that has received attention is the way to assign computational resources to those who participate in the system. In most cases, static resource allocation is used. Static allocation is simple but has several limitations, among them, the missutilization of resources. In this paper we present a proof-of-concept of a new system and report the results of experiments with a system that accomplishes dynamic resource allocation by using Quadtrees for space partitioning, in a Shared Virtual Environment.Ítem Edge and corner identification for tracking the line of sight(Fondo Editorial EAFIT, 2005) Orozco, María S.; Ruíz, Óscar E.; Jasnoch, Uwe; Kretschmer, Ursula; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents an edge-corner detector, implemented in the realm of the GEIST project (an Computer Aided Touristic Information System) to extract the information of straight edges and their intersections (image corners) from camera-captured (real world) and computer-generated images (from the database of Historical Monuments, using observer position and orientation data) -- Camera and computer-generated images are processed for reduction of detail, skeletonization and corner-edge detection -- The corners surviving the detection and skeletonization process from both images are treated as landmarks and fed to a matching algorithm, which estimates the sampling errors which usually contaminate GPS and pose tracking data (fed to the computer-image generatator) -- In this manner, a closed loop control is implemented, by which the system converges to exact determination of position and orientation of an observer traversing a historical scenario (in this case the city of Heidelberg) -- With this exact position and orientation, in the GEIST project other modules are able to project history tales on the view field of the observer, which have the exact intended scenario (the real image seen by the observer) -- In this way, the tourist “sees” tales developing in actual, material historical sites of the city -- To achieve these goals this article presents the modification and articulation of algorithms such as the Canny Edge Detector, SUSAN Corner Detector, 1-D and 2-D filters, etceteraÍtem Efficient use of mobile devices for quantification of pressure injury images(IOS Press, 2018-01-01) Garcia-Zapirain B; Sierra-Sosa D; Ortiz P D; Isaza-Monsalve M; Elmaghraby A; Garcia-Zapirain B; Sierra-Sosa D; Ortiz P D; Isaza-Monsalve M; Elmaghraby A; Universidad EAFIT. Departamento de Ciencias; Modelado MatemáticoPressure Injuries are chronic wounds that are formed due to the constriction of the soft tissues against bone prominences. In order to assess these injuries, the medical personnel carry out the evaluation and diagnosis using visual methods and manual measurements, which can be inaccurate and may generate discomfort in the patients. By using segmentation techniques, the Pressure Injuries can be extracted from an image and accurately parameterized, leading to a correct diagnosis. In general, these techniques are based on the solution of differential equations and the involved numerical methods are demanding in terms of computational resources. In previous work, we proposed a technique developed using toroidal parametric equations for image decomposition and segmentation without solving differential equations. In this paper, we present the development of a mobile application useful for the non-contact assessment of Pressure Injuries based on the toroidal decomposition from images. The usage of this technique allows us to achieve an accurate segmentation almost 8 times faster than Active Contours without Edges (ACWE) and Dynamic Contours methods.We describe the techniques and the implementation for Android devices using Python and Kivy. This application allows for the segmentation and parameterization of injuries, obtain relevant information for the diagnosis and tracking the evolution of patient's injuries. © 2018 - IOS Press and the authors.Ítem Ellipse-based principal component analysis for self-intersecting curve reconstruction from noisy point sets(SPRINGER, 2011-03-01) Ruiz, 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 1-manifold for the surface reconstruction to proceed. This article describes an implemented algorithm for the reconstruction of planar curves (1-manifolds) out of noisy point samples of a self-intersecting or nearly self-intersecting planar curve C. C:[a,b]R?R 2 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 self-intersect. Existing algorithms for curve reconstruction out of either noisy point samples or pixel data, do not produce a (possibly disconnected) Piecewise Linear 1-manifold approaching the whole point sample. The algorithm implemented in this work uses Principal Component Analysis (PCA) with elliptic support regions near the self-intersections. 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 non-correlation at the self-intersections (non-manifold neighborhoods) but also to occasional high noise at the non-self-intersecting (1-manifold) neighborhoods. © 2010 Springer-Verlag.Ítem Ellipse-based principal component analysis for self-intersecting curve reconstruction from noisy point sets(SPRINGER, 2011-03-01) Ruiz, O.; Vanegas, C.; Cadavid, C.; Ruiz, O.; Vanegas, C.; Cadavid, C.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesSurface reconstruction from cross cuts usually requires curve reconstruction from planar noisy point samples. The output curves must form a possibly disconnected 1-manifold for the surface reconstruction to proceed. This article describes an implemented algorithm for the reconstruction of planar curves (1-manifolds) out of noisy point samples of a self-intersecting or nearly self-intersecting planar curve C. C:[a,b]R?R 2 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 self-intersect. Existing algorithms for curve reconstruction out of either noisy point samples or pixel data, do not produce a (possibly disconnected) Piecewise Linear 1-manifold approaching the whole point sample. The algorithm implemented in this work uses Principal Component Analysis (PCA) with elliptic support regions near the self-intersections. 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 non-correlation at the self-intersections (non-manifold neighborhoods) but also to occasional high noise at the non-self-intersecting (1-manifold) neighborhoods. © 2010 Springer-Verlag.Ítem Especificación de un metamodelo para apoyar y extender la propuesta TD - MBUID(Universidad EAFIT, 2014) Orozco Morales, Daniel Fernando; Giraldo Orozco, Willliam Joseph; Trefftz Gómez, HelmuthEste trabajo de grado propone una nueva herramienta CASE, basada en trabajos anteriores, para la generación automática de interfaces gráficas de usuario -- La investigación realizada se centró, básicamente, sobre el trabajo de Giraldo[26] -- En este trabajo, Giraldo expone toda una integración de Procesos y Notaciones, y en lo que respecta a la presente investigación se retomó y continuó el tema de la integración de Notaciones, por lo que el resultado de este trabajo de grado es una herramienta CASE propuesta que integra las notaciones CIAN y UML logrando combinar el diseño, el prototipado (la generación) y la evaluación de las interfaces gráficas de usuario -- La manera en cómo se desarrolló este trabajo de grado y su resultado fue una dinámica sistemática -- Inicialmente, se estudiaron los metamodelos iniciales de Chico y CIAN, luego, se integraron estos dos metamodelos recibiendo nuevas funcionalidades, entre ellas: El diagrama de transformación y la gestión propia de los diagramas al interior del metamodelo resultante -- Una vez cumplido este primer objetivo, se procedió con la definición de la sintaxis concreta; en otras palabras: la construcción del DSL gráfico que soportara la generación de distintos tipos de diagramas y sus respectivos elementos y relaciones -- Teniendo ya la herramienta construida, el esfuerzo siguiente se centró en los algoritmos de transformación, tanto para transformar de modelo a modelo como para transformar de modelo a código -- Finalmente, se procedió a validar todo lo anteriormente realizado a través del planteamiento de un caso de estudioÍtem Estandarización de datos y priorización de algoritmos para un sistema de recomendación(Universidad EAFIT, 2019) González Arroyave, Dider León; Múnera Montoya, Edwin NelsonÍtem Estudio de la Web Colombiana: topología y visualización(Universidad EAFIT, 2007) Núñez Giraldo, Jorge Alejandro; Ardila Padilla, Carlos Andrés; Toro Escobar, Hernán DaríoÍtem 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 Exploring the role of system operation modes in failure analysis in the context of first generation cyber-physical systems(Universidad EAFIT, 2018) Ruíz Arenas, Santiago; Horváth, Imre; Mejía Gutiérrez, Ricardo; Rusák, Zoltan