Gabriel Bugeda
Universitat Politecnica de Catalunya, Civil Engineering, Faculty Member
In this chapter, we present a general introduction to Monte Carlo (MC)-based methods, sampling methodologies, stratification methods, and variance reduction techniques. In the first part, we will discuss the theoretical basis and the... more
In this chapter, we present a general introduction to Monte Carlo (MC)-based methods, sampling methodologies, stratification methods, and variance reduction techniques. In the first part, we will discuss the theoretical basis and the convergence proprieties of MC methods. The next part is devoted to pseudorandom and quasi-random number generation, the generation of random variables and the application of stratification. It is followed by techniques for correlation and discrepancy control. The third part presents the concept of Latin Hypercube Sampling (LHS). The last part introduces the concept of Multi-Level Monte Carlo (MLMC).
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Obtaining pressure radiated by flat surfaces is not a new problem. This problem has studied by the complexity of the topic and its application to design flat speakers. These kind of speakers are the speakers that we use in televisions,... more
Obtaining pressure radiated by flat surfaces is not a new problem. This problem has studied by the complexity of the topic and its application to design flat speakers. These kind of speakers are the speakers that we use in televisions, ceilings, cinema screens, panels, etc. in this cases usually we have rectangular speakers.
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Aircraft emission targets worldwide and their climatic effects have put pressure in government agencies, aircraft manufacturers and airlines to reduce water vapour, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) resulting... more
Aircraft emission targets worldwide and their climatic effects have put pressure in government agencies, aircraft manufacturers and airlines to reduce water vapour, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) resulting from aircraft emissions. The difficulty of reducing emissions including water vapor, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) is mainly due to the fact that a commercial aircraft is usually designed for a particular optimal cruise altitude but may be requested or required to operate and deviate at different altitudes and speeds to archive a desired or commanded flight plan, resulting in increased emissions. This is a multi- disciplinary problem with multiple trade-offs such as optimizing engine efficiency, minimizing fuel burnt and emissions while maintaining prescribed aircraft trajectories, altitude profiles and air safety. There are possible attempts to solve such problems by designing new wing/aircraft shape, new efficient engine, ATM technology, or modifying the aircraft flight plan. Based on the rough data provided by an air carrier company, who was willing to assess the methodology, this paper will present the coupling of an advanced optimization technique with mathematical models and algorithms for aircraft emission, and fuel burnt reduction through flight plan optimization. Two different approaches are presented; the first one describes a deterministic optimization of the flight plan and altitude profile in order to reduce the fuel consumption while reducing time and distance. The second approach presents the robust design optimization of the previous case considering uncertainties on several parameters. Numerical results will show that the methods are able to capture a set of useful trade-offs solutions between aircraft range and fuel consumption, as well as fuel consumption and flight time.
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Research Interests: Mathematics, Computer Science, Aerodynamics, Robust control, Optimization Problem, and 12 moreShape Optimization, Robust optimization, Multi objective optimization, Polynomial Approximation Theory, Robust Design, Navier Stokes, Evolutionary Algorithm, Mathematical Optimization, Non-dominated Sorting Genetic Algorithm-II (NSGA-II), Operant Conditioning, Fitness Function, and Pareto front
Research Interests: Engineering, Mechanical Engineering, Ocean Engineering, Aerospace Engineering, Mathematics, and 12 moreApplied Mathematics, Biomedical Engineering, Plasticity, Linear Elasticity, Finite element method, Industrial Engineering, Marine Engineering, Constitutive Equation, Engineering Civil, Engineering Manufacturing, Water Softening, and Multidisciplinary Engineering Optimisation
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L’objet de ce rapport est de presenter l’approche choise par le CIMNE afin d’optimiser des forms, dans le cadre des équations du potentiel incompressible portant. Plus... more
L’objet de ce rapport est de presenter l’approche choise par le CIMNE afin d’optimiser des forms, dans le cadre des équations du potentiel incompressible portant. Plus précisément, nous nous intéresserons ici à étudier l’influence de la partie “maillage adaptatif” sur la convergence globale d’un problème d’optimisation de formes. Les formes à optimiser sont des profils d’ailes d’avions (dimension 2). L’approche retenue utilice paramétrisation des formes considérées par des B-splines. Chaque domaine de calcul est alors discrétisé à l’aide d’un algorithme de maillage classique appelé méthode frontale avancée. Afin de definir à l’avance la taille des éléments de la d’erreur pour la solution des équations du potentiel incompressible (c’est l’influence de la précision requise pour cet estimateur, sur la convergence globale du processus, que nous étudierons). Enfin, on écrit le problème de reconstruction sous la forme d’un problème de minimisation, résolu par une méthode de quasi-Newton où le gradient de la fonctionnelle à minimiser est calculé exactement. &nbsp
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This work proposes a new adaptive remeshing strategy based on the sensitivity of the point wise error in stresses with respect to the nodal coordinates, which is computed using the adjoint-state method. This sensitivity provides... more
This work proposes a new adaptive remeshing strategy based on the sensitivity of the point wise error in stresses with respect to the nodal coordinates, which is computed using the adjoint-state method. This sensitivity provides information about the influence of the discretization of each zone of the computational domain in the estimation of the error in stresses at a specific point. This information is also used for the development of an adaptive remeshing strategy that provides a strict and economical control of this error.
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The FractalComs Project [1] was a basic research activity developed by the FractalComs consortium during a two years period (2002-2003) and founded by the European Commission through its Future and Emerging Technologies program included... more
The FractalComs Project [1] was a basic research activity developed by the FractalComs consortium during a two years period (2002-2003) and founded by the European Commission through its Future and Emerging Technologies program included in the Information Society Technologies priority of the 5 Framework Programme. The main goal of the Project was the basic research on Fractal Electrodynamics to ascertain the fundamental and technological performance limits of fractal-shaped miniature devices for their potential use in the future wireless telecommunication systems. The FractalComs consortium had five European partners: the Electromagnetics & Photonics Engineering Group of the Polytechnic University of Catalonia (UPC, Spain), the Lab. of Electromagnetics and Acoustics of the Federal Polytechnic Institute of Lausanne (EPFL, Switzerland), the Dept. of Electromagnetics and Physics of Matter of the University of Granada (UGR, Spain), the Interuniversity Research Center for Disordered Systems and Fractals in Chemical Engineering and Dept. of Electronic Engineering of the “La Sapienza” University of Rome (Italy), and the International Center for Numerical Methods in Engineering (CIMNE). The multidisciplinary nature of Fractal Electrodynamics required the cooperation of experts from different fields, such as electromagnetic theory, fractal mathematics, design of microwave antennas and devices, and numerical modelling. This paper briefly presents some of the main conclusions and results of the FractalComs Project.
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En esta tesis se describe el desarrollo e implementación de un sistema informático para el tratamiento de toda la información necesaria para un análisis por el Método de los Elementos... more
En esta tesis se describe el desarrollo e implementación de un sistema informático para el tratamiento de toda la información necesaria para un análisis por el Método de los Elementos Finitos o por otros métodos numéricos (diferencias finitas, volúmenes finitos, métodos de contorno, métodos de puntos, etc.).Algunas de sus partes se refieren principalmente al diseño y organización de un sistema de estas características. En otras, se describen los nuevos algoritmos que ha sido necesario desarrollar para cumplir los objetivos propuestos.Las diversas disciplinas que se describen a lo largo de la tesis se pueden diferenciar en:* Organización del sistema. Consiste en definir el tratamiento de todos los datos de un análisis genérico de manera uniforme. También se dan criterios sobre el ordenamiento interno de los datos.* Modelación geométrica. Se presenta una serie de algoritmos que se han desarrollado para tratar y modificar la geometría del modelo.* Generación de malla. Se describen diferentes técnicas y algoritmos para poder realizar la generación de la malla.* Adaptabilidad del sistema a diferentes análisis. Se describe como se ha diseñado y como se realiza la adaptación del sistema a un código de análisis cualquiera.La implementación del conjunto de criterios y algoritmos descritos a lo largo de esta tesis, ha permitido la creación de un sistema que da soporte al proceso de análisis mediante métodos numéricos de modelos, tanto a nivel académico como industrial
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Research Interests: Mechanical Engineering, Ocean Engineering, Aerospace Engineering, Applied Mathematics, Computer Science, and 14 moreBiomedical Engineering, Aerodynamics, Industrial Engineering, Marine Engineering, Shape Optimization, Industrial Engineering and Management, Adaptive Mesh Refinement, Mathematical Optimization, Interdisciplinary Engineering, Airfoil, Engineering Civil, Engineering Manufacturing, Multidisciplinary Engineering Optimisation, and Euler Equation
Research Interests: Engineering, Mechanical Engineering, Ocean Engineering, Aerospace Engineering, Biomedical Engineering, and 12 moreBiomaterials, Recycling, Aviation, Composite Materials, Industrial Engineering, Marine Engineering, Hybrid, Secondary Structure, Engineering Civil, Sandwich, Engineering Manufacturing, and Multidisciplinary Engineering Optimisation
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This paper investigates the High Lift System (HLS) application of complex aerodynamic design problem using Genetic Algorithms (GAs) coupled to Game strategies. Two types of optimization methods are used; the first method is a standard GA... more
This paper investigates the High Lift System (HLS) application of complex aerodynamic design problem using Genetic Algorithms (GAs) coupled to Game strategies. Two types of optimization methods are used; the first method is a standard GA based on Pareto dominance and the second method hybridises GA with a wellknown Nash Game strategies named Hybrid-GA. These optimization techniques are coupled to a pre/post processor GiD providing unstructured meshes during the optimisation procedure and a transonic analysis software PUMI. The computational efficiency and quality design obtained by GA and Hybrid-GA are compared. The numerical results for the multi-objective HLS design optimisation clearly shows the benefits of hybridising a GA with the Nash game and makes promising the above methodology for solving other more complex multi-physics optimisation problems in Aeronautics.
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This volume contains twelve lectures delivered by scientist and technologists at a Seminarof a European project named PROMUVAL. The main objective of the Seminar has been to offer internationally recognized experts a forum to present... more
This volume contains twelve lectures delivered by scientist and technologists at a Seminarof a European project named PROMUVAL. The main objective of the Seminar has been to offer internationally recognized experts a forum to present state of the art lectures on advanced Verification & Validation methodologies in Multiphysics areas including experimental investigations, modellingand numerical simulation, all necessary in the understanding of complex multiphysic phenomena,environmental and coupled problems of fundamental, industrial and societal interest. The volume is subdivided in 12 chapters which are grouped around four main themes: Multidisciplinary problems in rotorcraft technology; Multidisciplinary simulation and validation; Computational Aeroacoustics; Virtual Integrated Design; Fluid-Structure interaction problems
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Research Interests: Engineering, Evolutionary algorithms, Computational Fluid Dynamics, Mesh generation, Aerodynamics, and 15 moreIndustrial Engineering, Marine Engineering, Optimization, Mathematical Sciences, Taguchi Methods, Physical sciences, Multi objective optimization, Evolutionary Algorithm, Mathematical Optimization, Lift, Optimal Design, Engineering Materials, Response Surface Modeling, Engineering Civil, and Wing
Genetic Algorithms (GA) are useful optimization methods for exploration of the search space, but they usually have slowness problems to exploit and converge to the minimum. On the other hand, gradient based methods converge faster to... more
Genetic Algorithms (GA) are useful optimization methods for exploration of the search space, but they usually have slowness problems to exploit and converge to the minimum. On the other hand, gradient based methods converge faster to local minimums, although are not so robust (e.g., flat areas and discontinuities can cause problems) and they lack exploration capabilities. This article presents a hybrid optimization method trying to combine the virtues of genetic and gradient based algorithms, and to overcome their corresponding drawbacks. The performance of the Hybrid Method is compared against a gradient based method and a Genetic Algorithm, both used alone. The rate of convergence of the methods is used to compare their performance. To take into account the robustness of the methods, each one has been executed more than once, with different starting points for the gradient based method and different random seeds for the Genetic Algorithm and the Hybrid Method. The performance of t...
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The use of composite materials has grown exponentially in transport structures due to their weight reduction advantages, added to their capability to adapt the material properties and internal micro-structure to the requirements of the... more
The use of composite materials has grown exponentially in transport structures due to their weight reduction advantages, added to their capability to adapt the material properties and internal micro-structure to the requirements of the application. This flexibility allows the design of highly efficient composite structures that can reduce the environmental impact of transport, especially if the used composites are bio-based. In order to design highly efficient structures, the numerical models and tools used to predict the structural and material performance are of great importance. In the present paper, the authors propose a multi-objective, multi-scale optimization procedure aimed to obtain the best possible structure and material design for a given application. The procedure developed is applied to an aircraft secondary structure, an overhead locker, made with a sandwich laminate in which both, the skins and the core, are bio-materials. The structural multi-scale numerical model h...
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In this work the problem of overcoming local minima in the solution of nonlinear optimisation problems is addressed. As a first step, the existing nonlinear local and global optimisation methods are reviewed so as to identify their... more
In this work the problem of overcoming local minima in the solution of nonlinear optimisation problems is addressed. As a first step, the existing nonlinear local and global optimisation methods are reviewed so as to identify their advantages and disadvantages. Then, the major capabilities of a number of successful methods such as genetic, deterministic global optimisation methods and simmulated annealing, are combined to develop an alternative global optimisation approach based on a Stochastic-Probabilistic heuristic. The capabilities, in terms of robustness and efficiency, of this new approach are validated through the solution of a number of nonlinear optimisation problems. A well know evolutionary technique (Differential Evolution) is also considered for the solution of these case studies offering a better insight of the possibilities of the method proposed here.