Enhancing regression models for complex systems using evolutionary techniques for feature engineering

This work proposes an automatic methodology for modeling complex systems. Our methodology is based on the combination of Grammatical Evolution and classical regression to obtain an optimal set of features that take part of a linear and convex model. This technique provides both Feature Engineering and Symbolic Regression in order to infer accurate models with no effort or designer's expertise requirements. As advanced Cloud services are becoming mainstream, the contribution of data centers in the overall power consumption of modern cities is growing dramatically. These facilities consume from 10 to 100 times more power per square foot than typical office buildings. Modeling the power consumption for these infrastructures is crucial to anticipate the effects of aggressive optimization policies, but accurate and fast power modeling is a complex challenge for high-end servers not yet satisfied by analytical approaches. For this case study, our methodology minimizes error in power prediction. This work has been tested using real Cloud applications resulting on an average error in power estimation of 3.98%. Our work improves the possibilities of deriving Cloud energy efficient policies in Cloud data centers being applicable to other computing environments with similar characteristics.

Finite element code-based modeling of a multi-feature isolation system and passive alleviation of possible inner pounding

The existing seismic isolation systems are based on well-known and accepted physical principles, but they are still having some functional drawbacks. As an attempt of improvement, the Roll-N-Cage (RNC) isolator has been recently proposed. It is designed to achieve a balance in controlling isolator displacement demands and structural accelerations. It provides in a single unit all the necessary functions of vertical rigid support, horizontal flexibility with enhanced stability, resistance to low service loads and minor vibration, and hysteretic energy dissipation characteristics. It is characterized by two unique features that are a self-braking (buffer) and a self-recentering mechanism. This paper presents an advanced representation of the main and unique features of the RNC isolator using an available finite element code called SAP2000. The validity of the obtained SAP2000 model is then checked using experimental, numerical and analytical results. Then, the paper investigates the merits and demerits of activating the built-in buffer mechanism on both structural pounding mitigation and isolation efficiency. The paper addresses the problem of passive alleviation of possible inner pounding within the RNC isolator, which may arise due to the activation of its self-braking mechanism under sever excitations such as near-fault earthquakes. The results show that the obtained finite element code-based model can closely match and accurately predict the overall behavior of the RNC isolator with effectively small errors. Moreover, the inherent buffer mechanism of the RNC isolator could mitigate or even eliminate direct structure-tostructure pounding under severe excitation considering limited septation gaps between adjacent structures. In addition, the increase of inherent hysteretic damping of the RNC isolator can efficiently limit its peak displacement together with the severity of the possibly developed inner pounding and, therefore, alleviate or even eliminate the possibly arising negative effects of the buffer mechanism on the overall RNC-isolated structural responses.

A study of feature combination for vehicle detection based on image processing

Video analytics play a critical role in most recent traffic monitoring and driver assistance systems. In this context, the correct detection and classification of surrounding vehicles through image analysis has been the focus of extensive research in the last years. Most of the pieces of work reported for image-based vehicle verification make use of supervised classification approaches and resort to techniques, such as histograms of oriented gradients (HOG), principal component analysis (PCA), and Gabor filters, among others. Unfortunately, existing approaches are lacking in two respects: first, comparison between methods using a common body of work has not been addressed; second, no study of the combination potentiality of popular features for vehicle classification has been reported. In this study the performance of the different techniques is first reviewed and compared using a common public database. Then, the combination capabilities of these techniques are explored and a methodology is presented for the fusion of classifiers built upon them, taking into account also the vehicle pose. The study unveils the limitations of single-feature based classification and makes clear that fusion of classifiers is highly beneficial for vehicle verification.

Escuela en Hunstanton de A+P Smithson: el Nuevo Brutalismo en Inglaterra

La tesis estudia en detalle la Hunstanton Secondary School y su trascendencia. Así, se trata de analizar el conjunto de procesos que hace que esta obra sea entendida como el manifiesto construido del Nuevo Brutalismo en Inglaterra. La Escuela en Hunstanton fue la primera obra proyectada y construida por los Smithson y, si se considera que el legado que dejaron Alison y Peter fue más de carácter teórico que constructivo, ésta se ha convertido en un edificio relevante dentro de su trayectoria profesional. Además, el rigor con el que fue realizado el proyecto y la ratificación de las ideas que subyacían tras él, a pesar del extenso intervalo temporal que caracterizó su proceso constructivo, hacen que esta obra se convierta en una síntesis de la filosofía arquitectónica gestada en Inglaterra tras la guerra. Por otro lado, hay que contemplar que la sencillez del lenguaje constructivo empleado, viene dada por la compleja reiteración de los sistemas proyectuales tipo que formulan para este proyecto y el establecimiento de una gramática casi matemática. La sistematización de su vocabulario hace que, tras el análisis de su arquitectura, se encuentren nuevos parámetros capaces de documentar este momento de la historia de la arquitectura en Inglaterra. La envolvente del edificio constituye al tiempo fachada y estructura. Esta característica ha pasado inadvertida cuando, en numerosas ocasiones y durante seis décadas, se han venido publicando las fotografías de la obra terminada y los dibujos que los Smithson habían realizado en la fase de proyecto. Como consecuencia, ha proliferado el conocimiento de la arquitectura de la escuela a un nivel más superficial, mostrando el resultado formal de la misma y con ello, simplemente se ha dejado intuir la gran influencia que Mies Van der Rohe provocó en los Smithson en los primeros años de desarrollo de su labor como arquitectos. El objetivo principal de esta tesis es, por tanto, facilitar el entendimiento del espacio que propusieron los Smithson a partir del análisis pormenorizado de los distintos sistemas constructivos empleados y del equipo personal que se vio implicado en su construcción. Para ello, es necesario abordar el estudio de los materiales y mecanismos proyectuales que hicieron posible que este conjunto de espacios –interiores y exteriores- resultase definido a través de la relación entre dos variables: una evidente austeridad en la utilización de los materiales y la combinación de los distintos sistemas intervinientes a partir del recurso de la repetición. La Escuela de Hunstanton, a pesar de las inoportunas intervenciones realizadas para adaptar el centro a unas necesidades derivadas de su número de alumnos actual (el doble que en su inicio), continúa proclamando su integridad espacial. Partiendo de la hipótesis de que la arquitectura de la Secondary School en Hunstanton, representa el manifiesto construido del Nuevo Brutalismo en Inglaterra, se concluye que el resultado de su construcción fue consecuencia de numerosas influencias que, en relación con los Smithson, estuvieron presentes durante los años en que se gestó. Algo que va más allá de la conclusión de aquellos debates arquitectónicos que se habían emprendido, por escrito, en las distintas revistas locales de arquitectura. Los mecanismos compositivos empleados, también habían tenido mucho que ver con lo que los historiadores del arte habían venido aportando a la historia de la arquitectura hasta ese momento. Desde los años 40, éstos últimos habían emprendido una nueva manera de contar la historia en la que quedaba fuertemente involucrada su capacidad crítica, provocando interferencias en la mentalidad de los arquitectos de nueva generación y otorgándoles un bagaje cultural subliminalmente determinado y subjetivo. Por supuesto, en el resultado arquitectónico final, también tuvieron mucho que ver los recursos materiales de que se disponía en aquel momento. Así como la optimización de los mismos a través de la adopción de nuevas metodologías de trabajo como puede ser la organización multidisciplinar. La inclusión del ingeniero Ronald Jenkins en el equipo de trabajo de los Smithson supuso una gran oportunidad. Este ingeniero, propuso poner en práctica la entonces innovadora Teoría Plástica en la metodología de cálculo estructural y, con ello consiguió enriquecer el resultado espacial, posibilitando la percepción de una arquitectura ligera –a pesar de sus grandes dimensiones- y vinculada al paisaje donde se inserta. Pero todos estos condicionantes fueron pasados a su vez por el filtro del deseo de una regeneración social, que buscaba el modelo de la sociedad americana. El Buen Vivir que propugnaban los americanos, viajaba a Europa de la mano de la publicidad. Y, al igual que la componente publicitaria tuvo algo que ver en el proceso creativo de la arquitectura de la escuela, también lo tuvo el conocimiento del arte pop y sus recursos compositivos. ABSTRACT The thesis examines in detail the project of Hunstanton Secondary School and the architectural language’s significance used in it. Thus, it is reinterpreting the set of processes that makes this work to be understood as the “built manifesto” of the English New Brutalism. Hunstanton School’s project was the first work designed and built by the Smithsons and, considering their legacy -more theoretical than constructed-, make of this building an important work within their career. In addition, the rigor with which it was carried out the project and the ratification of the ideas lying behind him, make this work becomes a synthesis of the architectural philosophy gestated in England after the war, despite the extensive time interval that characterized its construction process. On the other hand, it must be considered the simplicity of the constructive language used in this project. It is given by the complex projective repetition of the type systems and by the establishment of a quasi-mathematical grammar. The systematization of its vocabulary makes, after a deep analysis of its architecture, to recognize new parameters able to document this moment in the history of English architecture. The building envelope is, at the same time, facade and structure. This feature has been overlooked when many photographs of the finished work and its drawings -made by the Smithsons during the design phase- has been exposed over six decades. As a result, it has proliferated the knowledge of Hunstanton Secondary Modern School’s architecture as a more superficial level, just by showing the formal outcome of its project and thus simply been left the sensation of the great influence that Mies Van der Rohe provocated in the Smithson thinking during their first years of developing his work as architects. Therefore, the main objective of this thesis is to facilitate an understanding of the Smithsons’ proposed space. This is made possible through the detailed analysis of the different systems used in it and, by understanding the knowledge of the team involved in its construction. To prove this, it is necessary to pay attention to the study of the materials and to different project mechanisms that make possible to this group of spaces -inner and outer- be defined through the game played by two variables: an apparent austerity in the use of materials and the combination of the various participant systems through the resource of repetition. Despite the untimely interventions made in order to adapt the center to the new needs (the large increase in the number of students), Hunstanton School’s building continues proclaiming its spatial integrity. Assuming that Hunstanton Secondary School’s architecture represents the manifesto of New Brutalism in England, it is concluded that the result of its construction was the result of numerous influences that, in connection with the Smithsons, were present during the years in which its project was conceived. This meaning goes beyond the conclusions made from the architectural debate that was published in many of local architectural magazines. The compositional mechanisms employed, are also linked to what art historians had contributed to the history of architecture until then. Since the 40s, historians had undertaken a new way to tell History. This new mode strongly implied its critical capacity. All this, was causing interferences in the mentality of the architects of the new generation and, giving them a subliminally determined and very subjective cultural background. Of course, the final architectural result had much to do with the material resources available at that time and, with its optimization through the adoption of new working methods as the multidisciplinary organization. The inclusion of engineer Ronald Jenkins in the team of the Smithsons was a great opportunity. He proposed to implement the new Plastic Theory in the structural calculation and thereby he got enrich the spatial results achieved, by enabling the perception of a lightweight construction, despite its large size and, linked to the landscape where it is inserted. But all these conditions were passed through the filter of social regeneration’s desire, following the American society’s model. This American model travelled to Europe in the hands of advertising. And, in the same way that publicity had something to do with the creative process of this architecture, also had a lot to do the knowledge of pop art and its compositional resources.

Multiple feature points representation in target localization of wireless visual sensor networks

This paper discusses the target localization problem in wireless visual sensor networks. Additive noises and measurement errors will affect the accuracy of target localization when the visual nodes are equipped with low-resolution cameras. In the goal of improving the accuracy of target localization without prior knowledge of the target, each node extracts multiple feature points from images to represent the target at the sensor node level. A statistical method is presented to match the most correlated feature point pair for merging the position information of different sensor nodes at the base station. Besides, in the case that more than one target exists in the field of interest, a scheme for locating multiple targets is provided. Simulation results show that, our proposed method has desirable performance in improving the accuracy of locating single target or multiple targets. Results also show that the proposed method has a better trade-off between camera node usage and localization accuracy.

Feature issue introduction: light, energy and the environment, 2014

This feature issue highlights contributions from authors who presented their research at the OSA Light, Energy and the Environment Congress, held in Canberra, Australia from 2-5 December, 2014.