Escuela de Ciencias Aplicadas e Ingeniería

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10 Challenges for the Specification of Self-Adaptive Software
(IEEE, 2018-01-01) Munoz-Fernandez, JC; Mazo, R; Salinesi, C; Tamura, G; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
The demand for systems that continue on operation by adapting themselves in response to disturbing changes in their environment has increased in the last decades. Those systems, termed self-adaptive software (SAS) systems, should be developed with techniques and methods appropriated for analysing and designing this kind of systems, starting from the requirements phase. Several contributions propose approaches to improve the specification of requirements for those systems. This paper aims to review the most significant challenges still open in the domains of languages for requirements specification and methods for model verification of self-adaptive systems, independently of their particular application areas. More concretely, the main contribution of this paper is a list of ten challenges to achieve a better-defined specification of requirements for SAS systems, and a more effective verification of such specifications. These challenges are well worthy of being addressed in both communities, the requirements engineering (RE) and the SAS one.
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/CAE
In 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.
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 flue implementing the lattice-boltzmann method
(TRANS TECH PUBLICATIONS LTD, 2014-01-01) Ruiz, D.B.; Mesa, A.A.; Alvis, R.G.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
Currently in the process of engineering, but increasingly implemented simulation methods since they are an economical and feasible to predict the behavior of some variable you wish to benefit. The problem of fluid simulation is a broad field of study, traditionally in this area are implemented domain discretization methods, volumes, differences or finite elements (Computational Fluid Dynamics), in this work, a different approach where the discretization is made on the physical properties of fluid and the fluid for reconstruction from its microscopic properties, simulating these, propagating Boltzmann distribution functions for the grid of nodes, this set is comprised of a fluid group of nodes, nodes fluid the border and nodes structure, docked the method to the boundary conditions necessary to simulate Glycerol in a pipe. © (2014) Trans Tech Publications, Switzerland.
2D simulation flue implementing the lattice-boltzmann method
(TRANS TECH PUBLICATIONS LTD, 2014-01-01) Ruiz, D.B.; Mesa, A.A.; Alvis, R.G.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Mecánica Aplicada
Currently in the process of engineering, but increasingly implemented simulation methods since they are an economical and feasible to predict the behavior of some variable you wish to benefit. The problem of fluid simulation is a broad field of study, traditionally in this area are implemented domain discretization methods, volumes, differences or finite elements (Computational Fluid Dynamics), in this work, a different approach where the discretization is made on the physical properties of fluid and the fluid for reconstruction from its microscopic properties, simulating these, propagating Boltzmann distribution functions for the grid of nodes, this set is comprised of a fluid group of nodes, nodes fluid the border and nodes structure, docked the method to the boundary conditions necessary to simulate Glycerol in a pipe. © (2014) Trans Tech Publications, Switzerland.
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 Metaheuristic Approach for the Cumulative Capacitated Arc Routing Problem
(Springer, 2018-09-12) Lenis, Sergio Andres; Carlos Rivera, Juan
In this paper we propose a new variant of the capacitated arc routing problem (CARP). In this new problem the objective function becomes a cumulative objective computed as the traveled distance multiplied by the vehicle load. A metaheuristic approach
A Metaheuristic Approach for the Cumulative Capacitated Arc Routing Problem
(Springer, 2018-09-12) Lenis, Sergio Andres; Carlos Rivera, Juan; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
In this paper we propose a new variant of the capacitated arc routing problem (CARP). In this new problem the objective function becomes a cumulative objective computed as the traveled distance multiplied by the vehicle load. A metaheuristic approach
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 for functional logic programs
(Elsevier BV, 2002-01-01) Alpuente, M.; Correa, F.; Falaschi, M.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
We present a generic scheme for the declarative debugging of functional logic programs which is valid for eager as well as lazy programs. In particular we show that the framework extends naturally some previous work and applies to the most modern lazy strategies, such as needed narrowing. First we associate to our programs a semantics based on a (continuous) immediate consequence operator, TR, which models computed answers. We show that, given the intended specification of a program R, it is possible to check the correctness of R by a single step of TR. We consider then a more effective methodology which is based on abstract interpretation: by approximating the intended specification of the success set we derive a finitely terminating diagnosis method, which can be used statically and is parametric w.r.t. to the chosen approximation. In order to correct the bugs, we sketch a preliminary deductive approach which uses example-guided unfolding. We specialize the incorrect rules w.r.t. sets of positive and negative examples which are gathered (bottom-up) during the diagnosis process, so that all refutations of negative examples and no refutation of positive examples are excluded. Our debugging framework does not require the user to either provide error symptoms in advance or answer difficult questions concerning program correctness. We extend an implementation of our system to the case of needed narrowing and illustrate it through some examples which demonstrate the practicality of our approach. © 2002 Published by Elsevier Science B.V.
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 Metaheuristic Approach for the Cumulative Capacitated Arc Routing Problem
(Springer Verlag, 2018-09-03) Rivera, Juan Carlos; Lenis, Sergio Andres; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones
In this paper we propose a new variant of the capacitated arc routing problem (CARP). In this new problem the objective function becomes a cumulative objective computed as the traveled distance multiplied by the vehicle load. A metaheuristic approach is proposed which is based on the hybridization of three known procedures: GRASP, VND and Set covering model. The metaheuristic is tested with some benchmark instances from CARP. The results allow to evaluate the performance with the different metaheuristic components and to compare the solutions with the classical objective function. © 2018, Springer Nature Switzerland AG.
A Mixed-Integer Linear Programming Model for a Selective Vehicle Routing Problem
(Springer International Publishing, 2018-09-03) Rivera, Juan Carlos; Posada, Andrea; PALACIO, JUAN DAVID
A Mixed-Integer Linear Programming Model for a Selective Vehicle Routing Problem
(Springer International Publishing, 2018-09-03) Rivera, Juan Carlos; Posada, Andrea; PALACIO, JUAN DAVID; Universidad EAFIT. Departamento de Ciencias; Matemáticas y Aplicaciones

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