Examinando por Materia "MODELOS MATEMATICOS"
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- Ponencia en CongresoAggregation languages for moving object and places of interest(2008) Gómez, Leticia Irene; Kuijpers, Bart; Vaisman, Alejandro Ariel"We address aggregate queries over GIS data and moving object data, where non-spatial information is stored in a data warehouse. We propose a formal data model and query language to express complex aggregate queries. Next, we study the compression of trajectory data, produced by moving objects, using the notions of stops and moves. We show that stops and moves are expressible in our query language and we consider a fragment of this language, consisting of regular expressions to talk about temporally ordered sequences of stops and moves. This fragment can be used not only for querying, but also for expressing data mining and pattern matching tasks over trajectory data."
- Artículo de Publicación PeriódicaBulk polymerization of styrene using multifunctional initiators in a batch reactor: A comprehensive mathematical model(2016-02) Berkenwald, Emilio; Laganá, María Laura; Acuña, Pablo; Morales Balado, Graciela Elizabeth; Estenoz, Diana"A detailed, comprehensive mathematical model for bulk polymerization of styrene using multifunctional initiators - both linear and cyclic - in a batch reactor was developed. The model is based on a kinetic mechanism that considers thermal initiation and chemical initiation by sequential decomposition of labile groups, propagation, transfer to monomer, termination by combination and re-initiation reactions due to undecomposed labile groups. The model predicts the evolution of global reaction variables (e.g, concentration of reagents, products, radical species and labile groups) as well as the evolution of the detailed complete polymer molecular weight distributions, with polymer species characterized by chain length and number of undecomposed labile groups. The mathematical model was adjusted and validated using experimental data for various peroxide-type multifunctional initiators: diethyl ketone triperoxide (DEKTP, cyclic trifunctional), pinacolone diperoxide (PDP, cyclic bifunctional) and 1,1-bis(tert-butylperoxy)cyclohexane (L331, linear bifunctional). The model very adequately predicts polymerization rates and complete molecular weight distributions. The model is used to theoretically evaluate the influence of initiator structure and functionality as well as reaction conditions."
- Artículo de Publicación PeriódicaCausality study and numerical response of the magnetic permeability as a function of the frequency of ferrites using Kramers–Kronig relations(2008) Fano, Walter Gustavo; Boggi, Silvina; Razzitte, Adrián C."In this paper, the numerical treatment of magnetic loss of NiZn, MnZn, Ni2Y, and NiZnCu ferrite and their composites, by using Krameres–Kronig relations, is investigated. The complex magnetic permeability spectra for ferromagnetic materials have been studied. Due to the principle of causality and time independence in the relation between magnetic induction B and magnetic field H, the real and the imaginary part of the complex magnetic permeability are mutually dependent, and the correlation is given by the Krameres–Kronig equations. Through them, it is possible to measure the real component of the complex magnetic permeability, assuming the real component is given, and by the Hilbert transform, the imaginary part of the magnetic permeability can be calculated. Magnetic circuit model has been studied theoretically, focusing on the model’s poles in the complex plane to verify the principle of causality and the temporary independence."
- Artículo de Publicación PeriódicaControl system to balance internal currents of a multilevel current-source inverter(2018-03) Cossutta, Pablo; Aguirre, Miguel Pablo; Angélico Engelhardt, Mathias; Valla, María Inés"Multilevel current-source inverters have proved to be a high-performance option for industrial applications due to reliability, fault-tolerant capabilities, quasi soft switching, and the use of lower filter capacitor values. One of its major challenges is to balance the internal currents that feed each module. Imbalances could be caused by manufacturing deviations of the reactive components, temperature drift or aging, nonlinear loads, and modulation errors, among others. Using the well-known phase-shift carrier sinusoidal pulse width modulation, a slight change in the amplitude of the carrier signals produces a variation in the average value of the internal currents. In this paper, we introduce a control strategy to balance the current of the inductors and its implementation in a prototype. Simulation and experimental results at different operating conditions show a robust behavior of the control system along with a low distortion in the output voltages and currents of the converter."
- Tesis de doctoradoEl convertidor multinivel fuente de corriente modular y sus aplicaciones(2019-05) Cossutta, Pablo; Valla, María Inés; Aguirre, Miguel Pablo"En esta tesis se realiza el análisis de una topología de Convertidor Multinivel Fuente de Corriente (MCSI) modular. Se analiza detalladamente el funcionamiento de la topología y se formula el marco matemático teórico necesario para el diseño, simulación y el control del convertidor. Se analiza el comportamiento de un módulo y luego se extiende el concepto a las versiones multinivel tanto simétrica, donde todos los módulos son iguales, como asimétrica, donde los módulos son de características similares pero de capacidades de corriente diferentes. Se detallan las técnicas de modulación que se utilizan en la actualidad, Modulación por Ancho de Pulso Sinusoidal (SPWM) y Modulación Vectorial (SVM). Para la modulación SPWM se propone un método simplificado para su implementación. Además, se evalúa la utilización de Control Predictivo Basado en Modelo de Conjunto Finito de Estados (FCS-MPC) para las diversas variantes del convertidor. Se presenta e implementa en una Matriz de Puertas Programables (FPGA) el balance de las corrientes internas del convertidor en su versión simétrica de 7 niveles. Se presenta además un aplicación en la cual se utiliza un MCSI como interfaz entre la red eléctrica y una celda de combustible basada en hidrógeno, validando los resultados en un modelo a escala que permite extrapolar los resultados a otros niveles de potencias. Se desarrolla e implementa un algoritmo de sincronización con la red eléctrica y una plataforma de adquisición de datos basados en una FPGA que permiten la conexión de un convertidor a la red eléctrica. Finalmente, se presentan y analizan tanto resultados de simulación como experimentales obtenidos utilizando un prototipo de laboratorio."
- Tesis de maestríaEvaluation of StarCCM+ to predict thermoacoustic instabilities using Large Eddy Simulation(2017) Indlekofer, Thomas; Ariatabar, Behdad; Bauer, Hans-Jörg; Hermeth, Sebastian"Self-sustained pressure and heat-release oscillations yielded by thermoacoustic coupling are a major problem of gas turbine operation and methods to predict them are needed. This work investigates the capabilities of Large Eddy Simulation (LES) in StarCCM+ to predict these instabilities in the academic Volvo bluff-body combustor. First, simplified cases are studied to assess boundary condition treatment and numerical accuracy of the methods available. The non-reactive operating point is predicted accurately, showing good agreement for velocity fields as well as the ability to predict the vortex shedding frequency in the intrinsically unsteady region of the recirculation zone. For a reacting-stable operating point the acceleration downstream of the bluff body is overpredicted and the flow fields are not predicted accurately. Low frequency oscillations of the unstable operating points are evidenced coincididing with experimental results and an acoustic analysis based on Comsol Multiphysics. Up to = 1:0 the coherence of the equivalence ratio and the magnitude of the instabilities is predicted qualitatively."
- Ponencia en CongresoAn extension of chaotic probability models to real-valued variables(2008-07) Fierens, Pablo Ignacio"Previous works have presented a frequentist interpretation of sets of measures as probabilistic models which have denominated chaotic models. Those models, however, dealt only with sets of probability measures on finite algebras, that is, probability measures which can be related to variables with a finite number of possible values. In this paper, an extension of chaotic models is proposed in order to deal with the more general case of real-valued variables."
- Artículo de Publicación PeriódicaLearning and imitation: transitional dynamics in variants of the BAM(2004) Heymann, D.; Perazzo, Roberto P. J.; Schuschny, A. R."We study the dynamics of self-organized systems when disturbed by shocks. For this purpose, we consider extensions of the “Bar Attendance Model” [1] (BAM), which provides a stylized setting for the analysis of the emergence of coordination in the behavior of a large collection of agents. We represent the learning process of the agents through genetic algorithms, which respond to global (publicly available) information. In addition, we allow the actions of agents to be influenced by local information, as expressed in the behavior and performance of neighboring individuals. In the context of the BAM, we show that, in the event of a shock, the imitation behavior may become widespread and generate a contagion cascade which mimics a collective panic. We use this framework to represent features of the dynamics of an actual bank run."
- Tesis de doctoradoMathematical modeling of discontinuous bulk styrene polymerization processes using multifunctional initiators(2016) Berkenwald, Emilio; Estenoz, Diana; Marqués, Dardo"En esta tesis, se estudia el uso de iniciadores multifuncionales para la polimerización en masa de estireno. El objetivo general es desarrollar modelos matemáticos detallados, y a la vez genéricos, que permitan describir la compleja fisicoquímica de estos procesos y predecir las variables principales de polimerizacióon, la evolución de la estructura molecular y las caracteríticas físicas del producto obtenido. La labor teórica se complementa con trabajos experimentales que permiten ajustar y validar los modelos propuestos."
- Artículo de Publicación PeriódicaModel selection: using information measures from ordinal symbolic analysis to select model subgrid-scale parameterizations(2017) Pulido, Manuel; Rosso, Osvaldo A."The use of information measures for model selection in geophysical models with subgrid parameterizations is examined. Although the resolved dynamical equations of atmospheric or oceanic global numerical models are well established, the development and evaluation of parameterizations that represent subgrid-scale effects pose a big challenge. For climate studies, the parameters or parameterizations are usually selected according to a root-mean-square error criterion that measures the differences between the model-state evolution and observations along the trajectory. However, inaccurate initial conditions and systematic model errors contaminate root-mean-square error measures. In this work, information theory quantifiers, in particular Shannon entropy, statistical complexity, and Jensen–Shannon divergence, are evaluated as measures of the model dynamics. An ordinal analysis is conducted using the Bandt–Pompe symbolic data reduction in the signals. The proposed ordinal information measures are examined in the two-scale Lorenz-96 system. By comparing the two-scale Lorenz-96 system signals with a one-scale Lorenz-96 system with deterministic and stochastic parameterizations, the study shows that information measures are able to select the correct model and to distinguish the parameterizations, including the degree of stochasticity that results in the closest model dynamics to the two-scale Lorenz-96 system."
- Tesis de doctoradoNuevos desarrollos en el modelado matemático del proceso continuo para la producción en masa de polímeros de estireno en presencia de elastómeros =(2022-07) Laganá, María Laura; Estenoz, Diana; Stripeikis, Jorge"El objetivo general de esta tesis es investigar aspectos aún no dilucidados en el área de la ingeniería del proceso de polimerización en masa de estireno (St) en presencia de elastómeros para la producción de Poliestireno de alto impacto (HIPS). La investigación se enfoca en el entendimiento y modelado matemático de los fenómenos fisicoquímicos involucrados, en el estudio y empleo de nuevas técnicas de modelado para la simulación de sistemas complejos, y en la optimización de los procesos. Se pretende lograr desarrollos que contribuyan a diseñar y operar los procesos industriales continuos con alto grado de comprensión, y optimizados desde el punto de vista de la productividad y de la calidad del producto final."
- PósterSimulación de la curva de capnografía a partir modelo matemático descriptivo de la vía aérea(2019) Racca, Dora María"Desarrollo de un modelo matemático descriptivo de la vía aérea que permite la simulación de la curva de capnografía en tiempo y volumen. Validación del sistema y su implementación en un simulador de mecánica respiratoria para entrenamiento médico."
- Proyecto final de GradoSimulación del capnograma y estimación de parámetros respiratorios a partir de un modelo matemático descriptivo de la vía aérea(2018) Racca, Dora María; Madorno, Matías"La necesidad de ventilación mecánica es la principal causa de internación en unidades de terapia intensiva. Establecer la estrategia óptima de ventilación suele ser una tarea que requiere extenso conocimiento y esta puede ser realizada, en momentos de emergencia, sin el adecuado conocimiento de la fisiopatología del paciente. La evaluación cuantitativa de modelos de la fisiología respiratoria permite comprender el funcionamiento del sistema modelado, además de asistir en la predicción de comportamientos basado en variables de entrada o de salida. El presente trabajo busca ampliar el conocimiento cuantitativo de la fisiología respiratoria de los pacientes con asistencia ventilatoria mecánica a través del uso de un modelo descriptivo de la vía aérea."
- Proyecto final de GradoSistemas eólicos de generación de energía con almacenamiento en hidrógeno: análisis de la tecnología y perspectiva de mercado en la Argentina(2008) Tuccillo, Julián I.; Lauretta, Juan Ricardo"En el trabajo se expone el concepto de generación distribuida de energía con sistemas que combinan aerogeneración y producción de hidrógeno mediante electrólisis de agua. Se estudia el dimensionamiento óptimo de estos sistemas, y su implementación en la Argentina en términos de factibilidad tecnológica y económico-financiera. Para dicho análisis se proyectan tres posibles modelos de negocio, pensando en un usuario o grupo de usuarios responsables de la propia generación de energía. A los fines de resolver las cuestiones de análisis, se desarrolla un modelo matemático de optimización que contempla los beneficios financieros sujetos a las restricciones de mercado, de inversión en recursos y a la demanda satisfecha. El modelo se construye en el programa MS Excel, y pretende ser una herramienta versátil para la toma de decisiones frente a las cambiantes situaciones tecnológicas y de mercado que se presenten a lo largo del tiempo. Finalmente, como conclusión se discuten las perspectivas de inserción tecnológica de estas energías renovables de la mano de un cambio cultural global."
- Tesis de doctoradoTheoretical and experimental study on the phase inversion process during the bulk synthesis of high impact polystyrene(2021-03-26) Maffi, Juan M.; Estenoz, Diana; Berkenwald, Emilio"In this thesis, the phenomenon of phase inversion is studied from a qualitative, theoretical and experimental point of view. The general objective is to contribute to the understanding of this fuid- and thermodynamic phenomenon in its particular application in the case of HIPS. The aim is to develop a physical-mathematical model capable of predicting the point of phase inversion during the reaction from the reactor conditions. Among the different alternatives, approaches based on the rheological evolution of the reaction mixture and others based on the fuid dynamics of the dispersed system are explored."
- Ponencia en CongresoA visual EEG epilepsy detection method based on a wavelet statistical representation and the Kullback-Leibler divergence(2017-10) Quintero-Rincón, Antonio; Pereyra, Marcelo; D'Giano, Carlos; Batatia, Hadj; Risk, Marcelo"This paper presents a statistical signal processing method for the characterization of EEG of patients suffering from epilepsy. A statistical model is proposed for the signals and the Kullback-Leibler divergence is used to study the differences between Seizure/Non-Seizure in patients suffering from epilepsy. Precisely, EEG signals are transformed into multivariate coefficients through multilevel 1D wavelet decomposition of different brain frequencies. The generalized Gaussian distribution (GGD) is shown to model precisely these coefficients. Patients are compared based on the analytical development of Kullback-Leibler divergence (KLD) of their corresponding GGD distributions. The method has been applied to a dataset of 18 epileptic signals of 9 patients. Results show a clear discrepancy between Seizure/Non-Seizure in epileptic signals, which helps in determining the onset of the seizure."
- Ponencia en CongresoVoltage-driven hysteresis model for resistive switching: SPICE modeling and circuit applications(2017-12) Patterson, Germán; Suñé, Jordi; Miranda, Enrique"Resistive switching devices are nonlinear electrical components that have drawn great attention in the design of new technologies including memory devices and neuromorphic circuits. In this paper, an SPICE implementation of a novel compact model is presented and put under test by means of different circuit configurations. The model is based on two identical opposite-biased diodes in series with a resistor where the switching behavior is governed by the creation and rupture of multiple conductive channels. Results show that the model is stable under different input sources and amplitudes and, with special interest, in multielement circuits. The model is validated with experimental data available in the literature. Both the corresponding SPICE code and schematic are provided in order to facilitate the model use and assessment."