Escuela de Ciencias Aplicadas e Ingeniería

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2D Shape similarity as a complement for Voronoi-Delone methods in shape reconstruction
(Elsevier, 2005) Ruíz S., Óscar E.; Cadavid, Carlos A.; Granados, Miguel; Peña, Sebastián; Vásquez, Eliana; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In surface reconstruction from planar slices it is necessary to build surfaces between corresponding 2D regions in consecutive levels -- The problem has been traditionally attacked with (i) direct reconstruction based on local geometric proximity between the regions, and (ii) classification of topological events between the slices, which control the evolution of the cross cuts -- These approaches have been separately applied with mixed success -- In the case (i), the results may be surfaces with over-stretched or unnatural branches, resulting from a local contour proximity which does not correspond to global similarity between regions -- In (ii), the consequences from topological events upon the actual surface realization have not been drawn -- In this paper an integration of (i) and (ii) is presented, which uses a criteria of similarity between composed 2D regions in consecutive slices to: (a) decide if a surface should actually relate those regions, (b) identify the topological transitions between levels and (c) construct the local surface for the related regions -- The method implemented hinders over-stretched and unnatural branches, therefore rendering a surface which adjusts to geometrically-sound topological events -- This is a good alternative when the surface reconstructed needs to be topologically faithful (for example in flow simulation) in addition to represent the a rough geometrical space (for example in radiation planning)
2D simulation pipeline implementing the Lattice-Boltzmann method
(TRANS TECH PUBLICATIONS LTD, 2013-09-01) Gomez, Rodrigo Orlando; Gomez, Rodrigo Orlando; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
3D Collaborative Virtual Environment for Real-Time GUI Sketching
(2011-07-01) Trefftz, Helmuth; Trefftz, Helmuth; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
A comparative computational study of blood flow pattern in exemplary textile vascular grafts
(Taylor and Francis Ltd., 2018-01-01) Valencia, R.A.; García, M.J.; Bustamante, J.; Mecánica Aplicada
Textile vascular grafts are biomedical devices and play an important role serving as a solution for the partial replacement of damaged arterial vessels. It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall. Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and cellular transport through the wall. The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction between platelets in textile grafts, related with the graft occlusion. This study involves both experimental and computational tests. Experimental tests are performed to characterize the permeability and porosity according to the ISO 7198 standard. The numerical process is based on a multi-scale approach where the fluid flow is solved with the Finite Element Method and the discrete particles are solved with the Molecular Dynamic Method. The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect both the local fluid dynamics and the level of penetration of platelets through the wall, thus indicating their importance as design parameters. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
A computationally efficient method for delineating irregularly shaped spatial clusters
(Springer Berlin Heidelberg, 2011-12-01) Duque, Juan C.; Aldstadt, Jared; Velasquez, Ermilson; Franco, Jose L.; Betancourt, Alejandro; Universidad EAFIT. Departamento de Economía y Finanzas; Research in Spatial Economics (RISE)
In this paper, we present an efficiency improvement for the algorithm called AMOEBA, A Multidirectional Optimum Ecotope-Based Algorithm, devised by Aldstadt and Getis (Geogr Anal 38(4):327-343, 2006). AMOEBA embeds a local spatial autocorrelation statistic in an iterative procedure in order to identify spatial clusters (ecotopes) of related spatial units. We provide an analysis of the computational complexity of the original AMOEBA and develop an alternative formulation that reduces computational time without losing optimality. Empirical evidence is provided using georeferenced socio-demographic data in Accra, Ghana. © 2010 Springer-Verlag.
A Debugging Scheme of Functional Logic Programs
(Elsevier BV, 2002-01-01) Correa, Francisco Jose; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
A FIRST-ORDER TIME CONSTANT ESTIMATION FOR NONLINEAR DIFFUSION PROBLEMS
(TAYLOR & FRANCIS INC, 2014-06-03) Simon, Laurent; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
A Laplace transform-based procedure was proposed to calculate the effective time constant for a class of nonlinear diffusion problems. The governing mathematical representation was first estimated with a linear model by omitting the nonlinear term. The solution to this problem was later introduced into the original equation, which was solved with Laplace transforms, resulting in a first-order approximation of the real system's behavior. A time constant was calculated using frequency-domain expressions. Two case studies were considered to illustrate the methodology. As the rate of heat supplied to a rod is raised, the speed at which the temperature reached an equilibrium value decreased. Increasing the maximum velocity in reaction-diffusion transport by a factor of three lowered the time constant by only 1.7%. The applications of this method range from biosensor dynamics to process control. © 2014 Copyright Taylor and Francis Group, LLC.
A General Meta-graph Strategy for Shape Evolution under Mechanical Stress
(Taylor and Francis Inc., 2019-01-01) Montoya-Zapata D.; Acosta D.A.; Ruiz-Salguero O.; Posada J.; Sanchez-Londono D.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
The challenges that a shape or design stands are central in its evolution. In the particular domain of stress/strain challenges, existing approaches eliminate under-demanded neighborhoods from the shape, thus producing the evolution. This strategy alone incorrectly (a) conserves disconnected parts of the shape and (b) eliminates neighborhoods which are essential to maintain the boundary conditions (supports, loads). The existing analyses preventing (a) and (b) are conducted in an ad-hoc manner, by using graph connectivity. This manuscript presents the implementation of a meta-graph methodology, which systematically lumps together finite element subsets of the current shape. By considering this meta-graph connectivity, the method impedes situations (a) and (b), while maintaining the pruning of under-demanded neighborhoods. Research opportunities are open in the application of this methodology with other types of demand on the shape (e.g., friction, temperature, drag, and abrasion). © 2019, © 2019 Taylor & Francis Group, LLC.
A General-Purpose Element-Based Approach to Compute Dispersion Relations in Periodic Materials with Existing Finite Element Codes
(World Scientific Publishing Co. Pte Ltd, 2019-01-01) Valencia C.; Gomez J.; Guarín-Zapata N.; Mecánica Aplicada
The numerical determination of dispersion relations in periodic materials via the finite element method is a difficult task in most standard codes. Here, we propose a novel technique which allows the computation of these band structures from local elemental subroutines in contrast with existing methods which impose Bloch boundary conditions on the global arrays. The proposed local approach is thus readily applicable to several physical contexts and space dimensionalities. Here we present the details of this element-based algorithm and provide verification results for three different kinematic assumptions applied to phononic crystals in a classical and a micropolar elastic medium. The paper also includes in the form of supplementary material, a fully-coded user subroutine and a test-problem to be used in a commercial finite element code. © 2019 IMACS.
A Local Stochastic Strategy for Rubik´s Cube,
(2013-06-01) Vélez, Juan Diego; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
A model for solving vehicle scheduling problems: a case study
(IMPRENTA UNIV ANTIOQUIA, 2018-09-01) Gulnara Baldoquin, Maria; Jose Rengifo-Campo, Alvaro; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
In this work we formulate a model to solve a type of vehicle scheduling problem, derived from the operation of the mass transit system (MIO) in Cali city, Colombia. Four companies operate the system with 3 types of buses and four depots. Two kinds of tasks should be assigned to operators' buses. A task is a sequence of consecutive travels of a route between two stations: initial and final. Each task should start and should finish in a depot, not necessarily the same. There are two main objectives defined by the operators. One objective is to minimize the total deadhead kilometers between depots and stations where tasks should start or end. The other objective is to minimize the maximum deviation of kilometers (commercial and deadhead) assigned to the operators regarding the ideal quantity of kilometers that they should have, according to the number of their buses in the fleet. We have implemented the proposed model in AMPL using Gurobi solver and we validate it using nine representative instances, generated with real data obtained from the system operation. The results obtained, in all cases, improve the solutions proposed by the company. Model variations are proposed to deal with new desirable constraints for the company.
A multi-start evolutionary local search for the one-commodity pickup and delivery traveling salesman problem
(Springer Netherlands, 2020-01-01) Palacio J.D.; Rivera J.C.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
This article addresses the one-commodity pickup and delivery traveling salesman problem (1-PDTSP), which is a generalization of the well-known traveling salesman problem. The 1-PDTSP aims to find a Hamiltonian tour in which a set of supply points (pickup locations), demand points (delivery locations) are visited and, the total traveled distance is minimized. We propose a hybrid metaheuristic based on multi-start evolutionary local search and variable neighborhood descent to solve the 1-PDTSP. To test the performance of our algorithm, we solve instances with up to 500 nodes available in the literature and we demonstrate that our approach is able to provide competitive results when comparing to other existing strategies. Since a direct application of the 1-PDTSP arises as the bicycle repositioning problem, we also use our metaheuristic algorithm to solve a set of real-case instances based on EnCicla, the bicycle sharing system in the Aburrá Valley (Antioquia, Colombia). © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
A multistart iterated local search for the multitrip cumulative capacitated vehicle routing problem
(Springer Netherlands, 2015-05-01) Rivera, Juan Carlos; Christian Prins; H. Murat Afsar; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
A new mechatronics laboratory for technology integration
(Springer-Verlag France, 2017-02-01) Velasquez-Lopez, Alejandro; Rodriguez-Garcia, Alberto; Universidad EAFIT. Departamento de Ingeniería Mecánica; Mecatrónica y Diseño de Máquinas
While teams and projects tend to be multi-domain, the infrastructure required to integrate and build prototypes lags behind to allow an efficient interaction and to offer multi-disciplinary facilities. Hence this paper presents an infrastructure approach developed in a Latin American academic context, where the concept of an Engineering Building is explained in order to support the demands of a 3rd Generation University. A deeper emphasis of this article is placed upon the development of a Technology Integration Laboratory in terms of functionality, capacity, adjacencies, furnishing and, physiologic and psicologic support. The layout design is based on the concepts of Mechatronics and Technical Systems while enhancing a teaching–learning-building process. After 5 years of operation the results obtained in terms of prototyping, filed patents and projects with the triad government-industry-academy are discussed. Our experience shows that such hands-on engineering facilities are worth having, especially within a virtual education growing trend, and that openness has influenced an increment of the Intellectual Property results. © 2015, Springer-Verlag France.
A novel simple procedure to consider seismic soil structure interaction effects in 2D models
(SPRINGER, 2014-09-01) Diego Jaramillo, Juan; David Gomez, Juan; Restrepo, Doriam; Rivera, Santiago; Mecánica Aplicada
A method is proposed to estimate the seismic soil-structure-interaction (SSI) effects for use in engineering practice. It is applicable to 2D structures subjected to vertically incident shear waves supported by homogenous half-spaces. The method is attractive since it keeps the simplicity of the spectral approach, overcomes some of the difficulties and inaccuracies of existing classical techniques and yet it considers a physically consistent excitation. This level of simplicity is achieved through a response spectra modification factor that can be applied to the free-field 5%-damped response spectra to yield design spectral ordinates that take into account the scattered motions introduced by the interaction effects. The modification factor is representative of the Transfer Function (TF) between the structural relative displacements and the free-field motion, which is described in terms of its maximum amplitude and associated frequency. Expressions to compute the modification factor by practicing engineers are proposed based upon a parametric study using 576 cases representative of actual structures. The method is tested in 10 cases spanning a wide range of common fundamental vibration periods. © 2014, Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg.
A novel simple procedure to consider soil structure interaction effects in 2D models. Accepted in Earthquake Engineering and Engineering Vibration
(SPRINGER, 2014-09-01) GOMEZ, JUAN DAVID; Mecánica Aplicada
A q-exponential statistical Banach manifold
(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2013-02-15) Loaiza, G.; Quiceno, H. R.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
Let µ be a given probability measure and Mµ the set of µ-equivalent strictly positive probability densities. In this paper we construct a Banach manifold on Mµ, modeled on the space L 8(p{dot operator}µ) where p is a reference density, for the non-parametric q-exponential statistical models (Tsallis's deformed exponential), where 0<q<1 is any real number. This family is characterized by the fact that when q?1, then the non-parametric exponential models are obtained and the manifold constructed by Pistone and Sempi is recovered, up to continuous embeddings on the modeling space. The coordinate mappings of the manifold are given in terms of Csiszár's F-divergences; the tangent vectors are identified with the one-dimensional q-exponential models and q-deformations of the score function. © 2012 Elsevier Ltd.
A Remark on the Heat Equation and Minimal Morse Functions on Tori and Spheres
(Fondo Editorial Universidad EAFIT, 2013-04-01) Vélez, Juan Diego; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
A review of regional science applications of satellite remote sensing in urban settings
(Elsevier Sci Ltd, 2013-01) Patino, J. E.; Duque, Juan C.; Universidad EAFIT. Escuela de Economía y Finanzas. Research in Spatial Economics (RiSE), Carrera 49 7 Sur-50, Medellín, Colombia.; Universidad EAFIT. Departamento de Economía y Finanzas; Patino, J.E. (jpatinoq@eafit.edu.co); Duque, Juan C. (jduquec1@eafit.edu.co); Research in Spatial Economics (RiSE); Research in Spatial Economics (RISE)
This paper reviews the potential applications of satellite remote sensing to regional science research in urban settings. Regional science is the study of social problems that have a spatial dimension. The availability of satellite remote sensing data has increased significantly in the last two decades, and these data constitute a useful data source for mapping the composition of urban settings and analyzing changes over time. The increasing spatial resolution of commercial satellite imagery has influenced the emergence of new research and applications of regional science in urban settlements because it is now possible to identify individual objects of the urban fabric. The most common applications found in the literature are the detection of urban deprivation hot spots, quality of life index assessment, urban growth analysis, house value estimation, urban population estimation and urban social vulnerability assessment. The satellite remote sensing imagery used in these applications has medium, high or very high spatial resolution, such as images from Landsat MSS, Landsat TM and ETM+, SPOT, ASTER, IRS, Ikonos and QuickBird. Consistent relationships between socio-economic variables derived from censuses and field surveys and proxy variables of vegetation coverage measured from satellite remote sensing data have been found in several cities in the US. Different approaches and techniques have been applied successfully around the world, but local research is always needed to account for the unique elements of each place. Spectral mixture analysis, object-oriented classifications and image texture measures are some of the techniques of image processing that have been implemented with good results. Many regional scientists remain skeptical that satellite remote sensing will produce useful information for their work. More local research is needed to demonstrate the real potential and utility of satellite remote sensing for regional science in urban environments.
A Revision of Philander (Marsupialia: Didelphidae), Part 1: P. quica, P. canus, and a New Species from Amazonia
(American Museum of Natural History, 2018-01-31) Voss, R.S.; Díaz-Nieto, J.F.; Jansa, S.A.; Universidad EAFIT. Departamento de Ciencias; Biodiversidad, Evolución y Conservación
This is the first installment of a revision of the didelphid marsupial genus Philander, commonly known as gray four-eyed opossums. Although abundant and widespread in lowland tropical forests from southern Mexico to northern Argentina, species of Philander are not well understood taxonomically, and the current literature includes many examples of conflicting species definitions and nomenclatural usage. Our revision is based on coalescent analyses of mitochondrial gene sequences, phylogenetic analyses of mitochondrial and nuclear genes, morphometric analyses, and firsthand examination of relevant type material. Based on these results, we provisionally recognize eight species, of which three are formally treated in this report: P. quica (Temminck, 1824), an Atlantic Forest endemic formerly known as P. frenatus (Olfers, 1818); P. canus (Osgood, 1913), a widespread species formerly treated as a synonym or subspecies of P. opossum (Linnaeus, 1758); and P. pebas, a new species endemic to Amazonia. The remaining, possibly valid, species of Philander can be allocated to two clades. The first is a cis-Andean complex that includes P. andersoni (Osgood, 1913); P. mcilhennyi Gardner and Patton, 1972; and P. opossum. The second is a trans-Andean complex that includes P. melanurus (Thomas, 1899) and P. pallidus (Allen, 1901). Among other nomenclatural acts, we designate a neotype for the long-problematic nominal taxon Didelphis superciliaris Olfers, 1818, and (in an appendix coauthored by Renate Angermann), we establish that Olfers' coeval binomen D. frenata is based on an eastern Amazonian type and is a junior synonym of P. opossum. © American Museum of Natural History 2018.

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