Control de sistemas dinámicos mediante procesos gaussianos

Los problemas de control representan una categoría en el ámbito del aprendizaje automático especializada en el manejo de un sistema dinámico mediante distintas técnicas. La categoría más comúnmente utilizada para resolver este tipo de problemas es el aprendizaje por refuerzo, en el que se ajusta el aprendizaje en base a la calidad de las acciones que realiza el controlador, medida con una función de coste. Desde el planteamiento de este tipo de problemas, ha habido distintas aproximaciones para abordarlos, pero en la mayoría de casos se repetían los mismos problemas, mayormente derivados del número de intentos necesarios durante las simulaciones para que el controlador aprendiese, lo que significa una alta repercusión en el entorno y un tiempo elevado, imposibilitando su utilización en robots u otros aparatos de bajo coste o con una vida útil corta. Durante este TFG se desarrolla una idea planteada por Carld Edward Rasmussen y Marc Peter Deisenroth llamada PILCO. En ella se aborda la creación de un sistema que aprende a resolver problemas de control utilizando técnicas de aprendizaje automático poco comunes en este tipo de problemas, como los métodos basados en modelos. La mayor virtud de PILCO reside en la eficiencia de datos y la velocidad en la que el controlador aprende su tarea asignada. Esto es posible gracias al funcionamiento del sistema propuesto, por el cual se obtiene información del entorno con la que se crea una imitación del mismo en los aspectos que influyen en las dinámicas que sigue el objeto a controlar. Mediante este sistema, se puede simular de forma artificial el entorno, permitiéndonos obtener datos acerca del efecto de las acciones realizadas por el controlador con las que entrenarlo, reduciendo el número de datos necesarios del entorno y aumentando la velocidad de aprendizaje del controlador radicalmente. Este sistema utiliza Procesos Gaussianos para modelar el entorno, aprendiendo las dinámicas del sistema y sirviendo de guía al controlador durante su aprendizaje. También han sido utilizadas redes neuronales para representar el rol de controlador. Además, cabe destacar la utilización del framework TensorFlow durante toda la implementación del trabajo, ampliando la base recibida durante el grado con conocimientos directamente aplicables en otros tipos de problemas de aprendizaje automátic

Plataforma de Análisis de Sostenibilidad de Edificios en Proyectos BIM

Máster en Investigación e Innovación en Inteligencia Computacional y Sistemas InteractivosEl sector de la edificación es uno de los principales consumidores de recursos y productores deemisiones contaminantes a nivel global; por ello, existe una serie de mecanismos que buscan reducirsu impacto y mejorar el rendimiento general de los proyectos de edificación a través del uso de técnicasde sostenibilidad.El trasfondo sobre el que se implementan la mayor parte de soluciones existentes es BIM (Buil-ding Information Modeling). Siguiendo los estándares y metodologías BIM, se consigue una mejorcomunicación entre los distintos profesionales implicados en un proyecto de edificación, así como unareducción de costes y emisiones generados en este proceso. Esto último ocurre gracias a la existenciade certificaciones de sostenibilidad que se aplican a lo largo del proceso. Este sector, además, cons-tituye uno de los sectores con menor grado de adopción de la tecnología en el mundo, con lo que seplantea como un buen escenario para el desarrollo de una herramienta software.En este Trabajo de Fin de Máster se plantea una investigación acerca del ámbito de la edificacióny el uso de técnicas de sostenibilidad en éste, a fin de comprender mejor el marco de la cuestión, parala creación de una herramienta que mejore la adopción de aspectos de sostenibilidad en proyectosde edificación. Esta herramienta permitirá desempeñar tareas de análisis de sostenibilidad, de formaque los profesionales encargados de realizar mediciones y estudios acerca de los puntos débiles deun proyecto de edificación en los aspectos sostenibles, se ayuden de ella para automatizar algunos delos pasos, facilitando esta tarea.Durante la fase de investigación, se lleva a cabo una búsqueda sistemática en la literatura disponi-ble, que culmina en una revisión de la información recogida. Respecto a la creación de la herramientade análisis de sostenibilidad de proyectos de edificación, se realiza un proceso de desarrollo softwareutilizando metodologías y técnicas de Ingeniería del Software aplicadas en la actualidad. Este procesode desarrollo concluye con la creación de una herramienta de rellenado simultáneo de certificados desostenibilidad en proyectos de edificación, tras un cambio de enfoque del proyecto motivado por losresultados obtenidos en las primeras fases del proceso de desarrollo software.Como conclusión, se ha obtenido una visión completa del funcionamiento del ámbito de la edifi-cación y, más concretamente, de la adopción de la sostenibilidad en este sector. También se ha pro-fundizado en el ámbito de la Ingeniería del Software, entrando en detalle en el proceso de desarrollosoftware del proyecto y aprendiendo a realizar los pasos necesarios para la obtención de un productosoftware de calidad. Finalmente, se ha obtenido una herramienta software para el rellenado simultáneode certificados de sostenibilidad en proyectos de edificación, cumpliendo con los objetivos principalesdel trabajo, a pesar de las dificultades encontradas a lo largo de la realización de éste

Simulación del comportamiento de materiales viscoelásticos y aplicación a la identificación de las propiedades mecánicas de la pared arterial

La simulación del comportamiento mecánico es una herramienta de gran importancia en las Ingenierías Civil y Mecánica. De igual forma, en la práctica médica es primordial la evaluación de las propiedades el asticas y viscosas de los tejidos biológicos debido a que estas pueden evidenciar un mal funcionamiento de la pared arterial. Por esta razón, en esta tesis, se desarrollan códigos para la simulación del comportamiento viscoel astico, y se evalúa su aplicabilidad en la identificación de las propiedades mecánicas de la pared arterial a partir de medidas experimentales in-vitro de presión y diámetro arterial. Se conoce que la pared arterial esta conformada por distintos materiales anisótropos, presentando cada uno diferentes respuestas reológicas. Sin embargo, el diagnóstico médico es usualmente realizado a partir de un conjunto de parámetros que caracterizan el comportamiento global de la pared arterial. Por lo anterior, en esta tesis, se desarrolla un código tridimensional viscoelástico e isótropo que permite considerar las grandes deformaciones. Más aún, para la identificación se considera un modelo de pared arterial perfectamente cilíndrica, compuesta por un unico material viscoelástico estándar, que permite considerar una pared arterial gruesa. Los códigos son validados utilizando soluciones analíticas y resultados numéricos obtenidos por otros códigos. Los códigos son utilizados para la identificación de propiedades en siete arterias de ovejas. Para la comparación con la bibliografía se desarrollan otros dos códigos que asumen la hipótesis de pequeñas deformaciones. También se utilizan los códigos que admiten las grandes deformaciones para la identificación, logrando cuantificar el efecto de la hipótesis de pequeñas deformaciones en el valor de los parámetros obtenidos. Se concluye que los resultados de los códigos de pequeñas deformaciones son comparables a los de la bibliografía, mientras que los del código de grandes deformaciones presentan diferencias significativas.The simulation of the mechanical behavior is a highly important tool for Civil and Mechanical Engineering. Likewise, in medical practice, evaluating parameters such as elastic and viscose properties of biological tissues is fundamental since they can show a malfunction on the arterial wall. Taking these into consideration, in this thesis, codes are developed in order to simulate the viscoelastic behavior, and to evaluate the applicability in the identification of the mechanical properties of the arterial wall considering experimental measures of arterial pressure and diameter. It is known that the arterial wall is formed by distinct anisotropic materials with diferent rheological responses. However, the current medical diagnosis is based on a set of parameters which characterize the arterial wall from a global point of view. For that reason, in this work a tridimensional viscoelastic and isotropic code is developed, which allows an analysis under large deformations. Moreover, a simple model is considered for the identification where the artery is perfectly cylindrical and constituted by a unique standard viscoelastic material, which allows considering a thick arterial wall. The codes are validated using analytical solutions and numerical results obtained with other codes. The codes are used for identifying properties of seven sheep arteries. In order to compare with the bibliography, other two codes for small deformation analysis are developed. The large deformation codes are also used for the identifi2cation of the mechanical properties in order to quantify the efect of the small deformation hypothesis on the values obtained for the parameters. It is concluded that the results of the small deformations codes are comparable with those of the bibliography, while the results of the large deformations codes present notorious diferences

Analysis of high-order interpolation schemes for solving linear problems in unstructured meshes using the finite volume method

Finite-volume strategies in fluid-structure interaction problems would be of crucialvimportance in many engineering applications such as in the analysis of reed valves in reciprocating compressors. The efficient implementation of this strategy passes from the formulation of reliable high-order schemes on 3D unstructured meshes. The development of high-order models is essential in bending-dominant problems, where the phenomenon of shear blocking appears. In order to solve this problem, it is possible to either increase the number of elements or increase the interpolation order of the main variable. Increasing the number of elements does not always yield good results and implies a very high computational cost that, in real problems, is inadmissible. Using unstructured meshes is also vital because they are necessary for real problems where the geometries are complex and depart from canonical rectangular or regular shapes. This work presents a series of tests to demonstrate the feasibility of a high-order model using finite volumes for linear elasticity on unstructured and structured meshes. The high-order interpolation will be performed using two different schemes such as the Moving Least Squares (MLS) and the Local Regression Estimators (LRE). The reliability of the method for solving 2D and 3D problems will be verified by solving some known test cases with an analytical solution such as a thin beam or problems where stress concentrations appear.P. Castrillo gratefully acknowledges the Universitat Politècnica de Catalunya and Banco Santander for the financial support of his predoctoral grant FPI-UPC (109 FPI-UPC 2018). The authors are supported by the Ministerio de Economía y Competitividad, Spain, RETOtwin project (PDC2021-120970-I00).Peer ReviewedPostprint (published version

Simulation of fluid-structure interaction and impact force on a reed valve

The cyclic impact force between a reed valve and the seat plate is the main reason of the valve failure in many thermo-technical devices as compressors, engines, etc. According to experimental observations the latter is due to fatigue and usually occurs in the leading part of the valve ‘neck’. In this work, a complex numerical analysis is presented aimed to studying the external forces and internal stresses suffered by the valve. In particular, the impact force between the valve and the seat is studied. The numerical analysis relies on the coupled synergy of two different simulation concepts. In order to do so, two codes are used: (1) first, the in-house Computational Fluid Dynamics (CFD) code presented in [1] is employed to simulate the Fluid-Structure Interaction (FSI) between gas and valve, extracting reference data for valve displacement and external gas pressures; (2) second, the analysis of the internal structure stresses, together with the impact forces with the plate is implemented in a Computational Solid Dynamics (CSD) code developed in FreeFEM++ [2]. The impact force representation is based on the formulation presented in [3] where a conserving algorithm for frictionless dynamic contact/impact is developed. Due to the importance of obtaining an adequate impact force, an exhaustive study is carried out on its characterization in terms of numerical parameters, such as the penalty stiffness. Under this framework, the valve displacement and impact velocities are verified. Hence, impact forces are analysed in different scenarios, obtaining interesting observations about stresses distribution, with a particular focus on the points where failure is experienced.The authors acknowledge Voestalpine Precision Strip AB company for the previous research collaboration project that allowed to validate experimentally the presented numerical methods. P. Castrillo gratefully acknowledges the Universitat Politecnica de Catalunya and Banco Santander for the financial ` support of his predoctoral grant FPI-UPC (109 FPI-UPC 2018). E. Schillaci acknowledges the financial support of the Programa Torres Quevedo (PTQ2018-010060). This work has also been financially supported by a competitive R+D project (ENE2017-88697-R) by the Spanish Research Agency.Postprint (published version

Towards a narrative definition of the American political thriller film

The Hollywood political thriller is a film genre of unique relevance in the United States, often acting as a reflection of the fears and anxieties of its historical times. At the same time, however, the definition of its identity and boundaries still leaves room for further specification, perhaps due to the frequent consideration of the political thriller as part of the broader categories of either thriller narratives or political films. By revising the available literature and filmography and analyzing the narrative features of the classical political thriller, this article proposes a deeper definition of the genre that takes into account the nature of the broader ‘thriller’ category of films springing from a specific mode of crime fiction that focuses on a victim or threatened individual as its protagonist, depicts and conveys intense emotional states, portrays an unbalanced and highly existentialist worldview, and travels into the extraordinary while at the same time holding on to very concrete expectations of verisimilitude. The political thriller specifies this broader form of narration and links it to dramatic conflicts of political nature, investigative plots, reactive characters, historically grounded antagonists, a proximity to the sociopolitical history of the United States, and a certain iconography relating to institutional power. By establishing the main narrative traits of the political thriller, this definition hopes to lay the foundations for a better understanding of the genre, its history, and its seeming renaissance at the onset of the 21st Centur

Experimental and Numerical Analysis Of Reed Valve Movement In An Impact Fatigue Test System and Reciprocating Compressors

During operation of a reciprocating compressor, its flapper valve opens to allow the passage of gases and closes by striking against the valve impact plate. This reed valve movement and impact is repeated billions of times. This cyclic movement has a significant influence on the impact fatigue life of the reed valve and, hence, the lifetime of a compressor. Inside a reciprocating compressor, a number of parameters including: the valve design, valve material, compressor operating frequency and suction/exhaust pressure, influence the reed valve movement. The valve movement can be defined in terms of valve frequency, valve lift, valve velocity and impact velocity. These response parameters heavily influence the compressor efficiency and impact fatigue life of reed valves. In this paper, we first studied the valve movement parameters for a reed valve design using an experimental test setup. In experimental testing, the valves were excited into movement using air pressure pulses at 100 Hz frequency (air pulse width of 5 milliseconds). The valve movement was recorded by a laser sensor at 10 000 frames per second. The operating conditions such as the operating frequency, air pulse width, applied pressure and airflow rate were measured. The valves were not tested to failure but only to collect the dynamic data of valve movement such as the valve movement curve (valve displacement vs time), average valve lift and reed velocity data. The experimental results were employed to validate a complex in-house 3D CFD finite-volume model aimed at studying in detail the valve and gas dynamics, whose interaction is solved by means of a Fluid-Structure Interaction (FSI) algorithm. The complete valve movement curve obtained from simulations – reed valve displacement vs time – correlated with that obtained from the experimental tests with small error. Similarly, the difference in experimental and numerically obtained average valve lift and impact velocity values were quite small for practical purposes. Finally, fluid-dynamic results for pressure and impact forces were employed to feed a finite-element based code aimed at studying the structural behavior of the reed vale. Bending fatigue and impact fatigue stresses induced in the reed valve during its movement cycle were calculated. The magnitude of stresses and their positioning was determined, which correlated with the commonly observed areas of fracture initiation in these valves. The numerical models, as well as the information obtained from this study will help the compressor manufacturers to design their compressors to enhance efficiency and reed valve’s reliability. This type of information is not readily available from a working compressor

Analysis of high-order interpolation schemes for the finite-volume resolution of linear problems on unstructured meshes

Finite-volume strategies in fluid-structure interaction problems would be of crucial importance in many engineering applications such as in the analysis of reed valves in reciprocating compressors. The efficient implementation of this strategy passes from the formulation of reliable high-order schemes on 3D unstructured meshes. The development of high-order models is essential in bending-dominant problems, where the phenomenon of shear blocking appears. In order to solve this problem, it is possible to either increase the number of elements or increase the interpolation order of the main variable. Increasing the number of elements does not always yield good results and implies a very high computational cost that, in real problems, is inadmissible. Using unstructured meshes is also vital because they are necessary for real problems where the geometries are complex and depart from canonical rectangular or regular shapes. This work presents a series of tests to demonstrate the feasibility of a high-order model using finite volumes for linear elasticity on unstructured and structured meshes. The high-order interpolation will be performed using two different schemes such as the Moving Least Squares (MLS) and the Local Regression Estimators (LRE). The reliability of the method for solving 2D and 3D problems will be verified by solving some known test cases with an analytical solution such as a thin beam or problems where stress concentrations appear

Logística Urbana: ¿Son realmente sostenibles las políticas sostenibles?

Road Freight transport is causing a number of social, environmental and economic negative impacts in many cities around the world.Therefore sustainable city logistics must be the solution to the problems of urban centers, with the main objective of researchers reduce these impacts, without penalizing the needs of cities. Cause of this several sustainable initiatives and policies have been implemented to help reduce them. But are the sustainable policies really sustainable? So this paper aims to evaluate one of these policies in a quantitative way to answer the question. Therefore be presented and implement a model based on VRP logic to evaluate the differences between the distances traveled by vehicles of a logistics company in a city with a policy regulating access and the distance traveled without such regulation. And based on the results obtained attempt draw conclusions to answer the question.La Logística Urbana sostenible debe ser solución ante los numerosos problemas sociales, medioambientales y económicos causados por el transporte de mercancías por carretera en las ciudades. De hecho son varias las iniciativas y políticas sostenibles que se han llevado a cabo para intentar reducir estos problemas. Pero ¿son realmente sostenibles estas políticas sostenibles? Este trabajo tiene como objetivo evaluar una de estas políticas de forma cuantitativa para poder responder a dicha pregunta. Así se evaluaron las diferencias entre las distancias recorridas por los vehículos de una empresa de logística en una ciudad con y sin una política de acceso regulado