Examinando por Materia "Sensitivity analysis"
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Ítem 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 MatemáticoThis 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.Ítem 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. Departamento de Ingeniería Mecánica; Estudios en Mantenimiento (GEMI)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.Ítem 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.; Catano-Lopez A.; Rojas-Diaz D.; Laniado H.; Arboleda-Sánchez S.; Puerta-Yepes M.E.; Lizarralde-Bejarano D.P.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesVectorial 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 AuthorsÍtem 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 MatemáticoVectorial 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 AuthorsÍtem Análisis de la sensibilidad paramétrica del proceso de producción de ciclo-trimetileno-triamina(Centro de Informacion Tecnologica, 2014-01-01) Ojeda, J.C.; Gilpavas, E.; Dobrosz-Gómez, I.; Gómez, M.Á.; Ojeda, J.C.; Gilpavas, E.; Dobrosz-Gómez, I.; Gómez, M.Á.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)Analyses of temperature, conversion, and their sensitivity with respect to the initial temperature were investigated by parametric sensitivity analysis using a dimensionless batch reactor model for the cyclotrimethylene- triamine synthesis. At first, an expression for its reaction rate was fitted from experimental data available in the literature. Then, a new simple sensitivity-based criterion was used to determine critical operating conditions analyzing temperature sensitivity trajectories. The critical condition of runaway reaction corresponds to a Semenov number (F) equals to 0.684, a heat of reaction parameter (B) equals to 15 and an Arrhenius-type number (?) of 20.Ítem Análisis de la sensibilidad paramétrica y del comportamiento dinámico de la hidrólisis del isocianato de metilo(Centro de Informacion Tecnologica, 2016-01-01) Ojeda, J.C.; GilPavas, E.; Dobrosz-Gómez, I.; Gómez, M.A.; Ojeda, J.C.; GilPavas, E.; Dobrosz-Gómez, I.; Gómez, M.A.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)In this work, parametric sensitivity and dynamic analysis were combined to determine the thermal instability conditions inherent in the methyl isocyanate hydrolysis reaction. This highly exothermic reaction tragically proved to be very sensible to temperature changes in the so-called Bhopal disaster in 1984. A stirred tank reactor in transient state was considered for simulating the reactive system. First, critical operational conditions were defined from the parametric sensitivity analysis. Subsequently, in a rigorous way, the dynamic analysis determined the thermal instability regions, Hopf bifurcations, and the thermal oscillatory behavior of the reactive system. The Matcont® software was used to solve the differential equations set. It was demonstrated that runaway conditions and the periodic solutions of temperature are closely related with the cooling temperature and the dimensionless parameters (f-dimensionless flow and l-heat transfer term) and their critical parameters were obtained: /c=752.39 and fc=1.57.Ítem Análisis de sensibilidad aplicado al Modelo Hidrogeológico Numérico (MHN) en el acuífero aluvial del río Nechí, Antioquia(Universidad EAFIT, 2022) Revelo Aristizábal, Mauricio Felipe; Buriticá Cortés, Lady Johana; Restrepo Correa, Isabel CristinaÍtem COMPLEX VARIABLE SENSITIVITY ANALYSIS OF THE RADIO FREQUENCY ABLATION PROCESS FOR CANCER TREATMENT(International Center for Numerical Methods in Engineering, 2015-01-01) Monsalvo, J.F.; García, M.J.; Monsalvo, J.F.; García, M.J.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Mecánica AplicadaThe complex Taylor series expansion (CTSE) method is applied in the sensitivity analysis of radio frequency ablation (RFA) procedures, in which the temperature distribution has to be accurately predicted in order to apply proper temperature values to tumor tissue and to avoid unwanted damage of healthy one. For this reason. the CTSE method was used to calculate local sensitivity. In this work, we solve a basic 2D model of the RFA process modelled by the bioheat transfer equation, and coupled with Joule heating equation. The accuracy, robustness and step -size independence are the main advantages of the CTSE method.Ítem Evaluación financiera y recomendación gerencial para la reactivación del campo Libertad y la Estación de Tratamiento de Crudo Estrella (ETCE)(2019) Cubides Cardona, Juan Sebastián; Urrea Morales, Jair Leonardo; Waserman Álvarez, Jean PaulThis document discloses the recommendations given by the authors to the company, Oil Company S.A., as a result of the financial valuation of three different technical alternatives proposed for the restarting of the Libertad oil field and Estrella crude oil treatment station. The authors are based on financial concepts and tools, such as: 1. Valuation, which allows to build projections and financial planning, 2. Cash flow method, using the cost of weighted average capital that, as an advantage, contemplates free cash flow discounting the costs and expenses incurred in the operation, 3. Econometric models, that allows the estimation of high impact variables. This document will be part of the tools used by the management of the Libertad field, in order to make them able to support the final choice that generates the most value, and in this way focus all its resources on a short, medium and long term strategic plan that help them to achieve the objectives of the company.Ítem MultiZ: A Library for Computation of High-order Derivatives Using Multicomplex or Multidual Numbers(Association for Computing Machinery (ACM), 2020-01-01) Aguirre-Mesa A.M.; Garcia M.J.; Millwater H.; Mecánica AplicadaMulticomplex and multidual numbers are two generalizations of complex numbers with multiple imaginary axes, useful for numerical computation of derivatives with machine precision. The similarities between multicomplex and multidual algebras allowed us to create a unified library to use either one for sensitivity analysis. This library can be used to compute arbitrary order derivates of functions of a single variable or multiple variables. The storage of matrix representations of multicomplex and multidual numbers is avoided using a combination of one-dimensional resizable arrays and an indexation method based on binary bitwise operations. To provide high computational efficiency and low memory usage, the multiplication of hypercomplex numbers up to sixth order is carried out using a hard-coded algorithm. For higher hypercomplex orders, the library uses by default a multiplication method based on binary bitwise operations. The computation of algebraic and transcendental functions is achieved using a Taylor series approximation. Fortran and Python versions were developed, and extensions to other languages are self-evident. © 2020 ACM.Ítem NORGAS : Análisis del proyecto de inversión Okianus(Universidad EAFIT, 2022) Rivas, Jorge Alberto; Vallejo Bravo, Diego; Vergara Garavito, Judith CeciliaCase study consisting of assessing the feasibility of an investment project to import liquefied petroleum gas, implemented since 2019 by the utility company NORGAS S.A. Historical figures are analyzed, indicators are projected, the project is valued with the discounted cash flow model and a sensitivity analysis is performed to determine its feasibility.Ítem On efficient methods for sensitivity analysis of FEM problems using hypercomplex numbers(Universidad EAFIT, 2019) Aguirre Mesa, Andrés Mauricio; García Ruiz, Manuel JulioÍtem Reporte Burkenroad Celsia S.A.(Universidad EAFIT, 2021) Restrepo Gallego, Luis Felipe; Loaiza Salazar, Eduardo; Restrepo Tobón, Diego AlexanderThe recommendation to hold is the result of a value per share of $ 4,296. Based on the assumption that the share is owned within the portfolio, an estimated target price for month 12 higher than the price on the valuation day, allows for profit from its sale.Ítem Sensitivity Analysis and Uncertainty Reduction in Large-Scale Models(Universidad EAFIT, 2024) Hinestroza Ramírez, Jhon Edinson; Quintero Montoya, Olga Lucía; Rendón Perez, Angela MaríaÍtem Sensitivity analysis for radiofrequency induced thermal therapies using the complex finite element method(ELSEVIER SCIENCE BV, 2017-11-01) Monsalvo, Juan F.; Garcia, Manuel J.; Millwater, Harry; Feng, Yusheng; Mecánica AplicadaIn radiofrequency induced thermal procedures for cancer treatment, the temperature of the cancerous tissue is raised over therapeutic values while maintaining the temperature of the surrounding tissue at normal levels. In order to control these temperature levels during a thermal therapy, it is important to predict the temperature distribution over the region of interest and analyze how the variations of the different parameters can affect the temperature in the healthy and damaged tissue. This paper proposes a sensitivity analysis of the radiofrequency induced thermal procedures using the complex Taylor series expansion (CTSE) finite element method (ZFEM), which is more accurate and robust compared to the finite difference method. The radiofrequency induced thermal procedure is modeled by the bioheat and the Joule heating equations. Both equations are coupled and solved using complex-variable finite element analysis. As a result, the temperature sensitivity with respect to any material property or boundary condition involved in the process can be calculated using CTSE. Two thermal therapeutical examples, hyperthermia and ablation induced by radio frequency, are presented to illustrate the capabilities and accuracy of the method. Relative sensitivities of the temperature were computed for a broad range of parameters involved in the radiofrequency induced thermal process using ZFEM. The major feature of the method is that it enables a comprehensive evaluation of the problem sensitivities, including both model parameters and boundary conditions. The accuracy and efficiency of the method was shown to be superior to the finite difference method. The computing time of a complex finite element analysis is about 1.6 times the computing time of real finite element analysis; significantly lower than the 2 times of forward/backward finite differencing or 3 times of central differencing. It was found that the radiofrequency hyperthermia procedure is very sensitive to the electric field and temperature boundary conditions. In the case of the radiofrequency ablation procedure, the cooling temperature of the electrodes has the highest liver/tumor temperature sensitivity. Also, thermal and electrical conductivities of the healthy tissue were the properties with the highest temperature sensitivities. The result of the sensitive analysis can be used to design very robust and safe medical procedures as well as to plan specific patient procedures.Ítem Sensitivity analysis in optimized parametric curve fitting(EMERALD GROUP PUBLISHING LIMITED, 2015-03-02) Ruiz, Oscar E.; Cortes, Camilo; Acosta, Diego A.; Aristizabal, Mauricio; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEPurpose-Curve fitting from unordered noisy point samples is needed for surface reconstruction in many applications. In the literature, several approaches have been proposed to solve this problem. However, previous works lack formal characterization of the curve fitting problem and assessment on the effect of several parameters (i.e. scalars that remain constant in the optimization problem), such as control points number (m), curve degree (b), knot vector composition (U), norm degree (k ), and point sample size (r) on the optimized curve reconstruction measured by a penalty function ( f ). The paper aims to discuss these issues. Design/methodology/approach-A numerical sensitivity analysis of the effect of m, b, k and r on f and a characterization of the fitting procedure from the mathematical viewpoint are performed. Also, the spectral (frequency) analysis of the derivative of the angle of the fitted curve with respect to u as a means to detect spurious curls and peaks is explored. Findings-It is more effective to find optimum values for m than k or b in order to obtain good results because the topological faithfulness of the resulting curve strongly depends on m. Furthermore, when an exaggerate number of control points is used the resulting curve presents spurious curls and peaks. The authors were able to detect the presence of such spurious features with spectral analysis. Also, the authors found that the method for curve fitting is robust to significant decimation of the point sample. Research limitations/implications-The authors have addressed important voids of previous works in this field. The authors determined, among the curve fitting parameters m, b and k, which of them influenced the most the results and how. Also, the authors performed a characterization of the curve fitting problem from the optimization perspective. And finally, the authors devised a method to detect spurious features in the fitting curve. Practical implications-This paper provides a methodology to select the important tuning parameters in a formal manner. Originality/value-Up to the best of the knowledge, no previous work has been conducted in the formal mathematical evaluation of the sensitivity of the goodness of the curve fit with respect to different possible tuning parameters (curve degree, number of control points, norm degree, etc.). © Emerald Group Publishing Limited.Ítem Sensitivity analysis in optimized parametric curve fitting(EMERALD GROUP PUBLISHING LIMITED, 2015-03-02) Ruiz, Oscar E.; Cortes, Camilo; Acosta, Diego A.; Aristizabal, Mauricio; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosPurpose-Curve fitting from unordered noisy point samples is needed for surface reconstruction in many applications. In the literature, several approaches have been proposed to solve this problem. However, previous works lack formal characterization of the curve fitting problem and assessment on the effect of several parameters (i.e. scalars that remain constant in the optimization problem), such as control points number (m), curve degree (b), knot vector composition (U), norm degree (k ), and point sample size (r) on the optimized curve reconstruction measured by a penalty function ( f ). The paper aims to discuss these issues. Design/methodology/approach-A numerical sensitivity analysis of the effect of m, b, k and r on f and a characterization of the fitting procedure from the mathematical viewpoint are performed. Also, the spectral (frequency) analysis of the derivative of the angle of the fitted curve with respect to u as a means to detect spurious curls and peaks is explored. Findings-It is more effective to find optimum values for m than k or b in order to obtain good results because the topological faithfulness of the resulting curve strongly depends on m. Furthermore, when an exaggerate number of control points is used the resulting curve presents spurious curls and peaks. The authors were able to detect the presence of such spurious features with spectral analysis. Also, the authors found that the method for curve fitting is robust to significant decimation of the point sample. Research limitations/implications-The authors have addressed important voids of previous works in this field. The authors determined, among the curve fitting parameters m, b and k, which of them influenced the most the results and how. Also, the authors performed a characterization of the curve fitting problem from the optimization perspective. And finally, the authors devised a method to detect spurious features in the fitting curve. Practical implications-This paper provides a methodology to select the important tuning parameters in a formal manner. Originality/value-Up to the best of the knowledge, no previous work has been conducted in the formal mathematical evaluation of the sensitivity of the goodness of the curve fit with respect to different possible tuning parameters (curve degree, number of control points, norm degree, etc.). © Emerald Group Publishing Limited.Ítem Sensitivity analysis of rainfall-induced shallow landslides using TRIGRS model. Case study : San Antonio de Prado, Medellín, Colombia(Universidad EAFIT, 2021) Osorio Rios, Leidy; Montoya Noguera, Silvana; Ramos Rivera, Johnatan; Montoya Noguera, Silvana; Ramos Rivera, JohnatanÍtem Spatiotemporal Modeling of Urban Growth Using Machine Learning(MDPI AG, 2019-12-28) Duque, J.; Jorge E. Patino; Gomez, J.; Passos, S.; Universidad EAFIT. Departamento de Economía y Finanzas; Research in Spatial Economics (RISE)This paper presents a general framework for modeling the growth of three important variables for cities: population distribution, binary urban footprint, and urban footprint in color. The framework models the population distribution as a spatiotemporal regression problem using machine learning, and it obtains the binary urban footprint from the population distribution through a binary classifier plus a temporal correction for existing urban regions. The framework estimates the urban footprint in color from its previous value, as well as from past and current values of the binary urban footprint using a semantic inpainting algorithm. By combining this framework with free data from the Landsat archive and the Global Human Settlement Layer framework, interested users can get approximate growth predictions of any city in the world. These predictions can be improved with the inclusion in the framework of additional spatially distributed input variables over time subject to availability. Unlike widely used growth models based on cellular automata, there are two main advantages of using the proposed machine learning-based framework. Firstly, it does not require to define rules a priori because the model learns the dynamics of growth directly from the historical data. Secondly, it is very easy to train new machine learning models using different explanatory input variables to assess their impact. As a proof of concept, we tested the framework in Valledupar and Rionegro, two Latin American cities located in Colombia with different geomorphological characteristics, and found that the model predictions were in close agreement with the ground-truth based on performance metrics, such as the root-mean-square error, zero-mean normalized cross-correlation, Pearson's correlation coefficient for continuous variables, and a few others for discrete variables such as the intersection over union, accuracy, and the f1 metric. In summary, our framework for modeling urban growth is flexible, allows sensitivity analyses, and can help policymakers worldwide to assess different what-if scenarios during the planning cycle of sustainable and resilient cities. © 2019 by the authors.Ítem Towards a holistic framework to model epidemics in presence of uncertainty : formulation of mathematical models and estimation of confidence intervals(Universidad EAFIT, 2021) Rojas Díaz, Daniel; Vélez Sánchez, Carlos Mario; Puerta Yepes, María Eugenia; Cadavid Moreno, Carlos Alberto