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A variable neighborhood search algorithm to minimize the total weighted tardiness on a batch processing machine
(Revista Ingeniería Industrial, 2011-08-11) López Jiménez, Juan Diego; Vélez Gallego, Mario César; López Jiménez, Juan Diego; Vélez Gallego, Mario César; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; Gestión de Producción y Logística
This paper presents the results of a research project conducted to solve a production scheduling problem observed in a system in which meeting customer due dates is the primary objective -- Each job to be scheduled is defined by its processing time, ready time, due date, weight and size -- The Batch Processing Machine (BPM) can process several jobs simultaneously as a batch as long as its capacity is not violated -- The processing time of a batch is the largest processing time among the jobs in the batch, and the batch ready time is the largest ready time among the jobs in the batch -- Given that the problem is NP-hard we propose a Variable Neighborhood Search (VNS) heuristic to minimize the total weighted tardiness on a single BPM -- The computational experiments conducted to assess the quality of the solutions found show that in a computational time restricted to a maximum of 30 minutes, the proposed heuristic finds solutions considerably better than the solutions obtained after implementing a mixed integer programming model available in the literature in a commercial solver
Adaptive System for the Generation of Emerging Behaviors in Serious Emerging Games
(Instituto Politecnico Nacional, 2020-01-01) Aguilar, Jose; Altamiranda, Junior; Diaz, Francisco; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
A video game adaptation system (SAV) for serious emergent games (JSE), allows emergent behaviors in the game, such as the appearance of environments, events, narratives and characters, among others, in order to adapt to the context in the one that is developing. In previous articles the architecture of a JSE engine has been proposed. Furthermore, a first subsystem has been proposed that allows the emergence of a JSE according to the objectives of the environment, based on the ant colony optimization algorithm (ACO). In the present work, the second component of said architecture is specified, the SAV, which allows its dynamic adaptation (during the JSE). The SAV is made up of the sub-layers of strategies, sequences and properties, which manage each of these types of possible emergencies in a JSE, with the intention of dynamically adapting it to the context-domain where the game is being played. Furthermore, in this work the behavior of these sublayers is analyzed in a specific case study, showing very encouraging results of SAV in the educational context of an intelligent classroom (SaCI).
Airline choice model for an international round-trip flight considering outbound and return flight schedules
(Warsaw University of Technology, 2020-01-01) Munoz C.; Laniado H.; Córdoba J.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
This paper quantified the impact of outbound and return flight schedule preferences on airline choice for international trips. Several studies have used airline choice data to identify preferences and trade-offs of different air carrier service attributes, such as travel time, fare and flight schedule. However, estimation of the effect return flight schedules have on airline choice for an international round-trip flight has not yet been studied in detail. Therefore, this study introduces attributes related to return flight characteristics and round-trip flight schedule interaction into the airline choice models, which have not previously been reported in the literature. We developed a stated preference survey that includes round-trip fares based on flight schedule combinations and the number of days prior to departure fares was purchased. We applied modelling techniques using a set of stated preference data. A mixed logit model was tested for the presence of heterogeneity in passengers' preferences. Our results indicated that models with attributes related to return flight and its interaction with outbound flight attributes have a superior fit compared with models only based on attributes reported in the literature review. The model found shows that airfare, travel time, arrival preference schedule in the outward journey, departure preference in the return journey and the schedule combination of round-trip flight are significantly affecting passenger choice behaviour in international round-trip flights. Sensitivity analysis of airline service characteristics and their marketing implications are conducted. The analysis reports seven policies with the greatest impact on each airline choice probabilities. It shows that by reducing travel time and airfare and by adopting an afternoon and night schedule preference for outbound and return flight, respectively, the highest probability on airline choice would be reached. This research contributes to the current literature by enhancing the understanding of how passengers choose airlines, considering both outbound and inbound journey characteristics. Thus, this study provides an analytical tool designed to provide a better understanding of international round-trip flight demand determinants and support carrier decisions. © 2020 Warsaw University of Technology. All rights reserved.
Allocation of intermediate buffer storage capacities in a production line
(2013-07-24) Vélez Gallego, Mario César; Jaramillo Jiménez, Jhull B.; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; jjaram61@eafit.edu.co; Gestión de Producción y Logística
In this research proposal we consider a production line with random demand and subject to random failures at each workstation -- Every time a workstation fails, a corrective maintenance activity is triggered to repair the workstation -- In order to palliate the effect of the random failures in the performance of the system, intermediate buffers are placed in-between workstations -- An inventory holding cost that increases with the stage of the process is associated to each buffer -- The research objective in this work is to allocate capacity to each intermediate buffer in the line so that the average cost per time unit is minimized while the average service level is kept above a minimum value -- In this paper we assume that unsatisfied demand is lost and the service level is defined as the long term proportion of satisfied demand -- A greedy simulation–based heuristic is presented to find a feasible solution to the problem in a reasonable computational time
An alternative model to explain the vectorial capacity using as example Aedes aegypti case in dengue transmission
(Elsevier BV, 2019-01-01) Catano-Lopez A.; Rojas-Diaz D.; Laniado H.; Arboleda-Sánchez S.; Puerta-Yepes M.E.; Lizarralde-Bejarano D.P.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Vectorial capacity (VC), as a concept that describes the potential of a vector to transmit a pathogen, has had historical problems related to lacks in dimensional significance and high error propagation from parameters that take part in the model to output. Hence, values estimated with those equations are not sufficiently reliable to consider in control strategies or vector population study. In this paper, we propose a new VC model consistent at dimensional level, i.e., the definition and the equation of VC have same and consistent units, with a parameter estimation method and mathematical structure that reduces the uncertainty in model output, using as a case of study an Aedes aegypti population of the municipality of Bello, Colombia. After a literature review, we selected one VC equation following biological, measurability and dimensional criteria, then we rendered a local and global sensitivity analysis, identifying the mortality rate of mosquitoes as a target component of the equation. Thus, we studied the Weibull and Exponential distributions as probabilistic models that represent the expectation of mosquitoes infective life, intending to include the best distribution in a selected VC structure. The proposed mortality rate estimation method includes a new parameter that represents an increase or decrease in vector mortality, as it may apply. We noticed that its estimation reduces the uncertainty associated with the expectation of mosquitoes' infective life expression, which also reduces the output range and variance in almost a half. Virology; Applied mathematics; Health sciences; Epidemiology; Infectious disease; Mortality; Uncertainty analysis; Vectorial capacity; Sensitivity analysis; Dengue © 2019 The Authors
Analysis of chaotic behaviour in supply chain variables
(Journal of Economics, Finance and Administrative Science, 2011-12) Peña Zapata, Gloria Elena; Ramírez Echeverri, Sergio Augusto; Universidad EAFIT. Departamento de Ingeniería de Producción; ramire@eafit.edu.co; gepena@unal.edu.co; Gestión de Producción y Logística
In this article we develop a supply chain model of four levels through the utilization of system dynamics with Ithink® and Mathlab® softwares to analyze data -- The supply chain is studied from the chaos theory perspective, which helps identifying the sensitive variables that can lead to a state of chaos -- A generic structure model that comprehends factory links, distribution, wholesale, retail and the client is constructed -- The difficulty of operations and logistics managers to decide how much to order and when to do it is simulated accordingly to what occurs in the links of the preceding and subsequent levels with two decision parameters: The first parameter denominated A indicates the participation (between 0 and 1) of the number of product units that are taken into account in the actual stock and the pending orders at the moment of performing an order – Thesecond parameter, denominated B, is the participation (between 0 and 1) of the number of units in the supply line (in transit) at the moment of performing orders of each of the links of the supply chain
Anteversión pélvica como causa de dolor lumbar, síndrome patelofemoral y dolores del crecimiento
(Ediciones Doyma, S.L., 2014-01-01) Vélez-Patiño, J.A.; Ríos-Sánchez, L.M.; Ochoa-Jaramillo, F.L.; Díaz-León, C.A.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Introduction: Back pain, patellofemoral syndrome and "growing pains" are increasingly common in children and adolescents, both with incidence and precocity of appearance. In most cases their etiology is unknown. Objective: The objective of this research was to explore the possible association of these three entities with pelvic anteversion. Methods: This is a cross-sectional study with case-control analysis, comprising a group of 30 symptomatic children aged between 6 and 17 years (cases) who had consulted for low back pain, "growing pains" or sore knees, and a control group of 30 children with no history of pain in these areas (controls). To measure the position of the pelvis and other biomechanical variables a software programme was developed that quantifies these measurements from reflective markings located on specific anatomical landmarks of each child. Other measurements were obtained through semiological tests and interviews with children and their parents. Results: Children and adolescents with pain had more pelvic anteversion compared with controls (mean 13.3 and 5.4 degrees, p < 0.001). They also had less strength in muscles: Lumbar extensor, abdominals, psoas and diaphragm. We found that psoas is the muscle most responsible for pelvis anteversion in symptomatic group. Compared with children without pain, those with back pain, patellofemoral syndrome or "growing pains" have 4.2 times more frequent poor or regular strength in the column extensor muscles. They also have nearly 18 times as likely to have a pelvic angle greater than 10 degrees compared with no pain children. Conclusions: Children and adolescents who suffer from back pain, patellofemoral syndrome and "growing pains" have increased pelvic anteversion and lower muscle strength, mainly in the thoracolumbar spine extensors, abdominals, diaphragm and psoas. The study found that the psoas muscle is most responsible for the development of pelvis anteversion. Pelvic anteversion is associated with low back pain, patellofemoral pain syndrome and "growing pains". © 2015 Arán Ediciones, S.L.
Application of the continuous wavelet transform in the extraction of directional data on RTM imaging condition wavefields
(Ecopetrol, 2018-01-01) Paniagua-Castrillón J.-G.; Quintero-Montoya O.-L.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Low-frequency artifacts in reverse time migration result from unwanted cross-correlation of the source and receiver wavefields at nonreflecting points along ray-paths. These artifacts can hide important details in migrated models and increase poor interpretation risk. Some methods have been proposed to avoid or reduce the number of these artifacts, preserving reflections, and improving model quality, implementing other strategies such as modification of the wave equation, proposing other imaging conditions, and using image filtering techniques. One of these methods uses wavefield decomposition, correlating components of the wavefields that propagate in opposite directions. We propose a method for extracting directional information from the RTM imaging condition wavefields to obtain characteristics allowing for better, more refined imaging. The method works by separating directional information about the wavefields based on the continuous wavelet transform (CWT), and the analysis of the main changes on the frequency content revealed within the scalogram obtained by a Gaussian wavelet family. Through numerical applications, we demonstrate that this method can effectively remove undesired artifacts in migrated images. In addition, we use the Laguerre-Gauss filtering to improve the results obtained with the proposed method. © 2018 Ecopetrol S.A. All Rights Reserved.
An approach to emotion Recognition in Single-channel EEG Signals using Stationary Wavelet Transform
(SPRINGER, 2017-04-01) MEJIA, GUSTAVO ANTONIO; QUINTERO, OLGA LUCIA; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
An approach to emotion recognition in single-channel EEG signals: a mother child interaction
(IOP Publishing, 2016) Gómez, A.; Quintero, L.; López, N.; Castro, J.; Gómez, A.; Quintero, L.; López, N.; Castro, J.; Mathematical Modeling Research Group, GRIMMAT, School of Sciences, Universidad EAFIT, Medellín, Colombia; Medical Technology Laboratory, Faculty of Engineering, Universidad Nacional de San Juan, Argentina; Psychology, Education and Culture Research Group Faculty of Social Science Politécnico Grancolombiano University Institution, Argentina; Universidad EAFIT. Escuela de Ciencias; agomez13@eafit.edu.co; oquinte1@eafit.edu.co; Modelado Matemático
In this work, we perform a first approach to emotion recognition from EEG single channel signals extracted in four (4) mother-child dyads experiment in developmental psychology -- Single channel EEG signals are analyzed and processed using several window sizes by performing a statistical analysis over features in the time and frequency domains -- Finally, a neural network obtained an average accuracy rate of 99% of classification in two emotional states such as happiness and sadness
arboles binomiales para la valoración de opciones sobre procesos derivados de la ecuacion diferencial estocástica autónoma
(Fondo Editorial Universidad EAFIT, 2010-12-01) Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Are neural networks able to forecast nonlinear time series with moving average components?
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2015-07-01) Cogollo, M.R.; Velásquez, J.D.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
In nonlinear time series forecasting, neural networks are interpreted as a nonlinear autoregressive models because they take as inputs the previous values of the time series. However, the use of neural networks to forecast nonlinear time series with moving components is an issue usually omitted in the literature. In this article, we investigate the use of traditional neural networks for forecasting nonlinear time series with moving average components and we demonstrate the necessity of formulating new neural networks to adequately forecast this class of time series. Experimentally we show that traditional neural networks are not able to capture all the behavior of nonlinear time series with moving average components, which leads them to have a low capacity of forecast. © 2015 IEEE.
Aspects to consider for high quality administration of Corporate Distribution Centers (Centros de Distribución, CEDIS)
(Journal of Economics, Finance and Administrative Science, 2011-06) Arrieta Posada, Juan Gregorio; Universidad EAFIT. Departamento de Ingeniería de Producción; jarrieta@eafit.edu.co; Gestión de Producción y Logística
In this document we present different aspects that are necessary to perform an excellent administration and control of distribution centers that corporations may have -- If these ideas are implemented correctly in an efficient way, most of the productivity problems in the warehouse could be solved easily -- Thus, it is important to evaluate the products’ activity profile, thelayout of the warehouse and the products’ flow through the distribution center -- The objective of this process is to obtain the conditions of a world class warehouse
Author Correction: Unsupervised Scalable Statistical Method for Identifying Influential Users in Online Social Networks (Scientific Reports, (2018), 8, 1, (6955), 10.1038/s41598-018-24874-2)
(Nature Publishing Group, 2019-01-01) Azcorra A.; Chiroque L.F.; Cuevas R.; Anta A.F.; Laniado H.; Lillo R.E.; Romo J.; Sguera C.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
The original version of this Article contained an error in Affiliation 3, which was incorrectly given as ‘Department of Mathematical Sciences, Universidad EAFIT, Universidad Nacional de Colombia, Medellín, Colombia’. The correct affiliation is listed below: Department of Mathematical Sciences, Universidad EAFIT, Medellín, Colombia This error has now been corrected in the HTML and PDF versions of the Article and in the accompanying Supplementary Material file. © 2019, The Author(s).
Behavior comparison for biomass observers in batch processes
(Wiley-Blackwell, 2013-06-18) Amicarelli, Adriana; Lucia Quintero M, O.; Di Sciascio, Fernando; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
On-line estimation of biomass concentration in batch biotechnological processes is an active area of research because normally, the biomass is the desired process product output, and also because it is necessary for control purposes to replace the unavail
Benchmarking about Lean Manufacturing in the textile sector in Medellin
(Journal of Economics, Finance and Administrative Science, 2010-06) Arrieta Posada, Juan Gregorio; Romano Martínez, María Jimena; Botero Herrera, Victoria Eugenia; Universidad EAFIT. Departamento de Ingeniería de Producción; jarrieta@eafit.edu.co; vboteroh@eafit.edu.co; mromanom@eafit.edu.co; Gestión de Producción y Logística
This document shows the results of a benchmarking study among different firms from the clothing industry that seeks to evaluate their degree of implementation in Lean Manufacturing during their respective productive processes -- The study mainly targets firms that produce blue jeans, cotton shirts and t-shirts -- Indeed, this industrial sector in the city of Medellin is highly developed and one of the most dynamic, thus the interest to perform an evaluation in this area -- To achieve the benchmarking, a questionnaire was designed and applied to the different firms that were visited -- The most significant result obtained was that Lean Manufacturing techniques were not prevalent within the general public -- Only those companies with years in the business, exporters or foreign trademarks licensees, were knowledgeable of their application and development
Big data?: historia, definición, herramientas y aplicaciones en la industria
(2019-01-07) Toro, M.; Laniado, H.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Dan Ariely, profesor de psicología y economía de la Universidad de Duke, plantea que "El big data [en español, datos masivos] es como el sexo en la adolescencia: todo el mundo habla de ello, nadie sabe realmente cómo hacerlo, todos piensan que los demás
Cerebral Cortex Atlas of Emotional States Through EEG Processing
(SPRINGER, 2019-10-14) Gómez A.; Quintero O.L.; Lopez-Celani N.; Villa L.F.; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
This paper addresses the cerebral cortex maps construction from EEG signals getting an information simplification method for an emotional state phenomenon description. Bi-dimensional density distribution of main signal features are identified and a comparison to a previous approach is presented. Feature extraction scheme is performed via windowed EEG signals Stationary Wavelet Transform with the Daubechies Family (1–10); nine temporal and spectral descriptors are computed from the decomposed signal. Recursive feature selection method based on training a Random forest classifier using a one-vs-all scheme with the full features space, then a ranking procedure via gini importance, eliminating the bottom features and restarting the entire process over the new subset. Stopping criteria is the maximum accuracy. The main contribution is the analysis of the resulting subset features as a proxy for cerebral cortex maps looking for the cognitive processes understanding from surface signals. Identifying the common location of different emotional states in the central and frontal lobes, allowing to be strong parietal and temporal lobes differentiators for different emotions. © 2020, Springer Nature Switzerland AG.
Clasificación ABC Multicriterio: tipos de criterios y efectos en la asignación de pesos
(2011-11-28) Vélez Gallego, Mario César; Castro Urrego, Jaime Andrés; Castro Zuluaga, Carlos Alberto; Vélez Gallego, Mario César; Castro Urrego, Jaime Andrés; Castro Zuluaga, Carlos Alberto; Universidad EAFIT. Departamento de Ingeniería de Producción; ccastro@eafit.edu.co; marvelez@eafit.edu.co; jcastrou@eafit.edu.co; Gestión de Producción y Logística
ABC classification is traditionally performed in companies in order to define and implement an inventory control policy for all the products within the same category -- The classification of products into categories is done according to their importance or relevance for some kind of criteria, usually the consumption or annual usage (for raw materials or spare parts) or demand or annual sales (for finished goods) using the well-know Pareto´s principle -- However, sometimes it is highly recommended and necessary to use additional criteria in order to make a more effective differentiation of stocks -- Therefore, this paper presents a collection of useful criteria for ABC classification; describes its meaning and how it must be measured -- Additionally, an example of a critical stage of a classification ABC with three criteria, shows that depending on the weights assigned and the characteristics of the products included in the classification process, the validity of some criteria are lost in the analysis
Collaborative Networked Virtual Surgical Simulators (CNVSS) Implementing Hybrid Client-Server Architecture: Factors Affecting Collaborative Performance
(MIT PRESS, 2015-01-01) Diaz, Christian; Trefftz, Helmuth; Quintero, Lucia; Acosta, Diego A.; Srivastava, Sakti; Universidad EAFIT. Escuela de Ciencias; Modelado Matemático
Currently, surgical skills teaching in medical schools and hospitals is changing, requiring the development of new tools to focus on (i) the importance of the mentor's role, (ii) teamwork skills training, and (iii) remote training support. Collaborative Networked Virtual Surgical Simulators (CNVSS) allow collaborative training of surgical procedures where remotely located users with different surgical roles can take part in the training session. To provide successful training involving good collaborative performance, CNVSS should guarantee synchronicity in time of the surgical scene viewed by each user and a quick response time which are affected by factors such as users' machine capabilities and network conditions. To the best of our knowledge, the impact of these factors on the performance of CNVSS implementing hybrid client-server architecture has not been evaluated. In this paper the development of a CNVSS implementing a hybrid client-server architecture and two statistical designs of experiments (DOE) is described by using (i) a fractional factorial DOE and (ii) a central composite DOE, to determine the most influential factors and how these factors affect the collaboration in a CNVSS. From the results obtained, it was concluded that packet loss, bandwidth, and delay have a larger effect on the consistency of the shared virtual environment, whereas bandwidth, server machine capabilities, and delay and interaction between factors bandwidth and packet loss have a larger effect on the time difference and number of errors of the collaborative task.

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