Vibration-Based structural health monitoring using piezoelectric transducers and parametric t-SNE

In this paper, we evaluate the performance of the so-called parametric t-distributed stochastic neighbor embedding (P-t-SNE), comparing it to the performance of the t-SNE, the non-parametric version. The methodology used in this study is introduced for the detection and classification of structural changes in the field of structural health monitoring. This method is based on the combination of principal component analysis (PCA) and P-t-SNE, and it is applied to an experimental case study of an aluminum plate with four piezoelectric transducers. The basic steps of the detection and classification process are: (i) the raw data are scaled using mean-centered group scaling and then PCA is applied to reduce its dimensionality; (ii) P-t-SNE is applied to represent the scaled and reduced data as 2-dimensional points, defining a cluster for each structural state; and (iii) the current structure to be diagnosed is associated with a cluster employing two strategies: (a) majority voting; and (b) the sum of the inverse distances. The results in the frequency domain manifest the strong performance of P-t-SNE, which is comparable to the performance of t-SNE but outperforms t-SNE in terms of computational cost and runtime. When the method is based on P-t-SNE, the overall accuracy fluctuates between 99.5% and 99.75%.Peer ReviewedPostprint (published version

Damage diagnosis for offshore fixed wind turbines

This paper proposes a damage diagnosis strategy to detect and classify different type of damages in a laboratory offshore-fixed wind turbine model. The proposed method combines an accelerometer sensor network attached to the structure with a conceived algorithm based on principal component analysis (PCA) with quadratic discriminant analysis (QDA). The paradigm of structural health monitoring can be undertaken as a pattern recognition problem (comparison between the data collected from the healthy structure and the current structure to diagnose given a known excitation). However, in this work, as the strategy is designed for wind turbines, only the output data from the sensors is used but the excitation is assumed unknown (as in reality is provided by the wind). The proposed methodology is tested in an experimental laboratory tower modeling an offshore-fixed jacked-type wind turbine. The obtained results show the reliability of the proposed approach.Peer ReviewedPostprint (published version

Soft computing techniques applied to finance

Soft computing is progressively gaining presence in the financial world. The number of real and potential applications is very large and, accordingly, so is the presence of applied research papers in the literature. The aim of this paper is both to present relevant application areas, and to serve as an introduction to the subject. This paper provides arguments that justify the growing interest in these techniques among the financial community and introduces domains of application such as stock and currency market prediction, trading, portfolio management, credit scoring or financial distress prediction areas.Publicad

Del conocimiento como puesta en relación. El paradigma de la imagen dialógica en el cine de no ficción

Históricamente la exploración de la realidad desde la práctica audiovisual, tanto en cine como en formatos televisivos de no ficción, se ha regido por una lógica de representación que privilegia el valor de la imagen como índice. Frente a esto, el presente artículo aboga por rescatar dinámicas de pensamiento dialógico puestas en marcha desde espacios marginales de la institución cine. Aquí el gesto fundamental reside en la puesta en relación de discursos como base de un proceso de conocimiento que cuestiona la validez de la imagen como evidencia axiomática, y sustituye este principio por el devenir incierto de la reflexión filosófica. Siguiendo esta línea de trabajo, el texto se centra en el análisis de prácticas que de forma consciente trabajan para socavar el valor documental de las imágenes, planteando que el mismo debe articularse en continua tensión con los parámetros discursivos que estructuran cualquier ejercicio audiovisual.Non-fiction discourses in both cinema and TV have mostly been determined by what we can term as ‘the logic of reality representation’ whereby factuality resides to an extent in the value of the image as index. In opposition to this, the present article advocates the importance of knowledge as an open-ended process as illustrated by a number of examples in film history. Here, the clash of discourses lays the foundations of a truly dialogic conception of knowledge. As a result, axiomatic values are openly questioned and philosophical reflection is put forward as a valid model for non-fictional cinematic practice in spite of its uncertainty and lack of resolution. Following this, the text focuses on films and examples which consciously undermine a documentary logic, defending the need to assess the latter in constant tension with the discursive parameters inherent to any audiovisual exercise

Applied Computational Intelligence for finance and economics

This article introduces some relevant research works on computational intelligence applied to finance and economics. The objective is to offer an appropriate context and a starting point for those who are new to computational intelligence in finance and economics and to give an overview of the most recent works. A classification with five different main areas is presented. Those areas are related with different applications of the most modern computational intelligence techniques showing a new perspective for approaching finance and economics problems. Each research area is described with several works and applications. Finally, a review of the research works selected for this special issue is given.Publicad

Analysis of Ausubel auctions by means of evolutionary computation

IEEE Congress on Evolutionary Computation. Edimburgo, 2-5 September 2005The increasing use of auctions has led to a growing interest in the subject. A recent method used for carrying out examinations on auctions has been the design of computational simulations. The aim of this paper is to develop a genetic algorithm to find bidders' optimal strategies for a specific dynamic multi-unit auction. The algorithm provides the bidding strategy (defined as the action to be taken under different auction conditions) that maximizes the bidder's payoff. The algorithm is tested under several experimental environments, number of bidders and quantity of lots auctioned. The results suggest that the approach leads to strategies that outperform canonical strategies

Evolutionary rule-based system for IPO underpricing prediction

Genetic And Evolutionary Computation Conference. Washington DC, USA, 25-29 June 2005Academic literature has documented for a long time the existence of important price gains in the first trading day of initial public offerings (IPOs).Most of the empirical analysis that has been carried out to date to explain underpricing through the offering structure is based on multiple linear regression. The alternative that we suggest is a rule-based system defined by a genetic algorithm using a Michigan approach. The system offers significant advantages in two areas, 1) a higher predictive performance, and 2) robustness to outlier patterns. The importance of the latter should be emphasized since the non-trivial task of selecting the patterns to be excluded from the training sample severely affects the results.We compare the predictions provided by the algorithm to those obtained from linear models frequently used in the IPO literature. The predictions are based on seven classic variables. The results suggest that there is a clear correlation between the selected variables and the initial return, therefore making possible to predict, to a certain extent, the closing price.This article has been financed by the Spanish founded research MCyT project TRACER, Ref: TIC2002-04498-C05-04M

En torno a las imágenes del horror. Montaje del conocimiento en Tierra sin pan y Noche y niebla

A través del análisis de Tierra sin pan (Buñuel, 1933) y Noche y niebla (Alain Resnais, 1955), las siguientes páginas tienen como finalidad discutir el valor de uso de las imágenes del horror en ejercicios de “montaje del conocimiento”. Esta expresión, tomada del trabajo crítico de Georges Didi-Huberman, enfatiza tanto la puesta en relación de estas imágenes con otros discursos como el valor desestabilizador de las mismas, su capacidad para perturbar narrativas canónicas en diferentes ámbitos. Metodológicamente, la aproximación a ambos filmes privilegia el examen históricamente situado de las intenciones discursivas latentes en estos textos, prestando especial atención a las formas en las que ambas películas cuestionan aspectos de la cultura audiovisual de la que forman parte.The following pages aim to discuss the way in which horror images have been used in order to produce knowledge. This is done in relation to two films: Land Without Bread (Buñuel, 1933) and Night and Fog (Alain Resnais, 1955). The critical work of Georges Didi-Huberman represents a major reference in both its foregrounding of the link between the images of horror and other discourses, and also in highlighting the disturbing value of such images. Methodologically, the text privileges a historically situated examination of both films’ discursive intentions and, in particular, of the ways in which both examples question concrete aspects of the visual culture they themselves inhabit