Examinando por Materia "simulation"
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Ítem 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 ComunicacionesCurrently 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.Ítem Agents as tutors in augmented reality(2003-01-01) Álvarez, N.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las ComunicacionesInteraction between virtual entities and human beings should be similar to the normal interaction between human beings. Verbal interaction is the usual way of interaction among humans, but the interfaces that allow verbal communication between a human being and an agent (virtual human) have a limited vocabulary, need a lot of training and are expensive. In this paper we propose an Augmented Reality System with an unidirectional interface between an agent and a person. By using gestures, animations and adequate texts the agent can show a user how to perform a simple task. We hope that the tests to be conducted will show how useful this unidirectional interface is.Ítem A collaborative tool for synchronous distance education(2004-01-01) Agudelo, A.; Escobar, L.; Restrepo, J.; Quiroz, A.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las ComunicacionesIn this paper we report results of the use of a telepresence application in a simulated distance education setting. The application combines video-conference with a networked virtual environment in which the instructor and the students can experiment with virtual object in a collaborative manner. The teaching for Understanding (TFU) framework is used as the pedagogical approach. Current preliminary results show that the combination of the telepresence application with TFU, can compensate for the lack of physical presence of the instructor in the classroom.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 Exploring Undergraduate Students' Computational Modeling Abilities and Conceptual Understanding of Electric Circuits(Institute of Electrical and Electronics Engineers Inc., 2018-08-01) Ortega-Alvarez J.D.; Sanchez W.; Magana A.J.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosContribution: This paper adds to existing literature on teaching basic concepts of electricity using computer-based instruction; findings suggest that students can develop an accurate understanding of electric circuits when they generate multiple and complementary representations that build toward computational models. Background: Several studies have explored the efficacy of computer-based, multi-representational teaching of electric circuits for novice learners. Existing research has found that instructional use of computational models that move from abstract to concrete representations can foster students' comprehension of electric circuit concepts, but other features of effective instruction using computational models need further investigation. Research Questions: 1) Is there a correlation between students' representational fluency and their ability to reason qualitatively on electric circuits? and 2) Is the quality of student-generated computational representations correlated to their conceptual understanding of electric circuits? Methodology: The study comprised two cases in which 51 sophomore-engineering students completed a voluntary assignment designed to assess their representational fluency and conceptual understanding of electric circuits. Qualitative insights from the first case informed the design of a scoring rubric that served as both the assessment and the data collection instrument. Findings: The results suggest that a multi-representational approach aimed at the construction of computational models can foster conceptual understanding of electric circuits. The number and quality of students' representations showed a positive correlation with their conceptual understanding. In particular, the quality of the computational representations was found to be highly, and significantly, correlated with the correctness of students' answers to qualitative reasoning questions. © 1963-2012 IEEE.Ítem In vitro mechanical evaluation of mandibular bone transport devices(ASME, 2014-06-01) Zapata, Uriel; Watanabe, Ikuya; Opperman, Lynne A.; Dechow, Paul C.; Mulone, Timothy; Elsalanty, Mohammed E.; Zapata, Uriel; Watanabe, Ikuya; Opperman, Lynne A.; Dechow, Paul C.; Mulone, Timothy; Elsalanty, Mohammed E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaBone transport distraction osteogenesis (BTDO) is a surgical procedure that has been used over the last 30 years for the correction of segmental defects produced mainly by trauma and oncological resections. Application of BTDO has several clinical advantages over traditional surgical techniques. Over the past few years, several BTDO devices have been introduced to reconstruct mandibular bone defects. Based on the location and outline of the defect, each device requires a uniquely shaped reconstruction plate. To date, no biomechanical evaluations of mandibular BTDO devices have been reported in the literature. The present study evaluated the mechanical behavior of three different shaped prototypes of a novel mandibular bone transport reconstruction plate and its transport unit for the reconstruction of segmental bone defects of the mandible by using numerical models complemented with mechanical laboratory tests to characterize strength, fatigue, and stability. The strength test evaluated device failures under extreme loads and was complemented with optimization procedures to improve the biomechanical behavior of the devices. The responses of the prototypes were characterized to improve their design and identify weak and strong regions in order to avoid posterior device failure in clinical applications. Combinations of the numerical and mechanical laboratory results were used to compare and validate the models. In addition, the results remark the importance of reducing the number of animals used in experimental tests by increasing computational and in vitro trials. © VC 2014 by ASME.Ítem In vitro mechanical evaluation of mandibular bone transport devices(ASME, 2014-06-01) Zapata, Uriel; Watanabe, Ikuya; Opperman, Lynne A.; Dechow, Paul C.; Mulone, Timothy; Elsalanty, Mohammed E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Bioingeniería GIB (CES – EAFIT)Bone transport distraction osteogenesis (BTDO) is a surgical procedure that has been used over the last 30 years for the correction of segmental defects produced mainly by trauma and oncological resections. Application of BTDO has several clinical advantages over traditional surgical techniques. Over the past few years, several BTDO devices have been introduced to reconstruct mandibular bone defects. Based on the location and outline of the defect, each device requires a uniquely shaped reconstruction plate. To date, no biomechanical evaluations of mandibular BTDO devices have been reported in the literature. The present study evaluated the mechanical behavior of three different shaped prototypes of a novel mandibular bone transport reconstruction plate and its transport unit for the reconstruction of segmental bone defects of the mandible by using numerical models complemented with mechanical laboratory tests to characterize strength, fatigue, and stability. The strength test evaluated device failures under extreme loads and was complemented with optimization procedures to improve the biomechanical behavior of the devices. The responses of the prototypes were characterized to improve their design and identify weak and strong regions in order to avoid posterior device failure in clinical applications. Combinations of the numerical and mechanical laboratory results were used to compare and validate the models. In addition, the results remark the importance of reducing the number of animals used in experimental tests by increasing computational and in vitro trials. © VC 2014 by ASME.Ítem Instability Analysis and Optimal Conditions for Methanol Production in a Lurgi Reactor.(Centro de Informacion Tecnologica, 2016-01-01) GIL PAVAS EDISON; Dobrosz-Gómez, I.; Gómez, Miguel Angel; GIL PAVAS EDISON; Dobrosz-Gómez, I.; Gómez, Miguel Angel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)In the present work, the operational conditions for methanol synthesis in a Lurgi reactor are analyzed. The industrial data for a packed reactor (consisting of 1620 tubes of 7 m long) are the basis of this study. At first, the industrial reactor...Ítem Modelos multinomiales: un análisis de sus propiedades(2011-06-13) Guarin Galeano, Arlen Yahir; Ramírez Hassan, Andrés; Torres, Juan FelipeThis paper develops an analysis of Multinomial models through simulation; this was done under correct and incorrect assumptions on the data generating process. Also, it was analyzed the performance of the models under different sample sizes. It was found that a correct specified model with samples of 200 or more observations achieves estimators which are unbiased and consistent, while incorrect assumptions about the data generating process causes biased and inconsistent estimators. On the other hand, conditional models with small sample sizes imply bad statistical properties, especially when Probit models are estimated.Ítem Numerical-analytical solutions of predator-prey models(World Scientific and Engineering Academy and Society, 2013-01-01) González-Parra Gilberto, G.; Arenas, A.J.; Cogollo, M.R.; Universidad EAFIT. Escuela de Ciencias; Modelado MatemáticoThis paper deals with the construction of piecewise analytic approximate solutions for nonlinear initial value problems modeled by a system of nonlinear ordinary differential equations. In real world several biological and environmental parameters in the predator-prey model vary in time. Thus, non-autonomous systems are important to be studied. We show the effectiveness of the method for autonomous and non-autonomous predator-prey systems. The method we have used is called the differential transformation method which has some suitable properties such as accuracy, low computational cost, easiness of implementation and simulation as well as preserving properties of the exact theoretical solution of the problem. The accuracy of the method is checked by numerical comparison with fourth-order Runge-Kutta results applied to several predator-prey examples.Ítem S-maup: Statistical test to measure the sensitivity to the modifiable areal unit problem(Public Library of Science, 2018-11-27) Duque J.C.; Laniado H.; Polo A.; Universidad EAFIT. Escuela de Ciencias; Modelado MatemáticoThis work presents a nonparametric statistical test, S-maup, to measure the sensitivity of a spatially intensive variable to the effects of the Modifiable Areal Unit Problem (MAUP). To the best of our knowledge, S-maup is the first statistic of its type and focuses on determining how much the distribution of the variable, at its highest level of spatial disaggregation, will change when it is spatially aggregated. Through a computational experiment, we obtain the basis for the design of the statistical test under the null hypothesis of non-sensitivity to MAUP. We performed an exhaustive simulation study for approaching the empirical distribution of the statistical test, obtaining its critical values, and computing its power and size. The results indicate that, in general, both the statistical size and power improve with increasing sample size. Finally, for illustrative purposes, an empirical application is made using the Mincer equation in South Africa, where starting from 206 municipalities, the S-maup statistic is used to find the maximum level of spatial aggregation that avoids the negative consequences of the MAUP. © 2018 Duque et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Ítem S-maup: Statistical test to measure the sensitivity to the modifiable areal unit problem(Public Library of Science, 2018-11-27) Duque J.C.; Laniado H.; Polo A.; Universidad EAFIT. Departamento de Economía y Finanzas; Research in Spatial Economics (RISE)This work presents a nonparametric statistical test, S-maup, to measure the sensitivity of a spatially intensive variable to the effects of the Modifiable Areal Unit Problem (MAUP). To the best of our knowledge, S-maup is the first statistic of its type and focuses on determining how much the distribution of the variable, at its highest level of spatial disaggregation, will change when it is spatially aggregated. Through a computational experiment, we obtain the basis for the design of the statistical test under the null hypothesis of non-sensitivity to MAUP. We performed an exhaustive simulation study for approaching the empirical distribution of the statistical test, obtaining its critical values, and computing its power and size. The results indicate that, in general, both the statistical size and power improve with increasing sample size. Finally, for illustrative purposes, an empirical application is made using the Mincer equation in South Africa, where starting from 206 municipalities, the S-maup statistic is used to find the maximum level of spatial aggregation that avoids the negative consequences of the MAUP. © 2018 Duque et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.