“Dust in the wind...”, deep learning application to wind energy time series forecasting

To balance electricity production and demand, it is required to use different prediction techniques extensively. Renewable energy, due to its intermittency, increases the complexity and uncertainty of forecasting, and the resulting accuracy impacts all the different players acting around the electricity systems around the world like generators, distributors, retailers, or consumers. Wind forecasting can be done under two major approaches, using meteorological numerical prediction models or based on pure time series input. Deep learning is appearing as a new method that can be used for wind energy prediction. This work develops several deep learning architectures and shows their performance when applied to wind time series. The models have been tested with the most extensive wind dataset available, the National Renewable Laboratory Wind Toolkit, a dataset with 126,692 wind points in North America. The architectures designed are based on different approaches, Multi-Layer Perceptron Networks (MLP), Convolutional Networks (CNN), and Recurrent Networks (RNN). These deep learning architectures have been tested to obtain predictions in a 12-h ahead horizon, and the accuracy is measured with the coefficient of determination, the R² method. The application of the models to wind sites evenly distributed in the North America geography allows us to infer several conclusions on the relationships between methods, terrain, and forecasting complexity. The results show differences between the models and confirm the superior capabilities on the use of deep learning techniques for wind speed forecasting from wind time series data.Peer ReviewedPostprint (published version

A Genetic Clustering Algorithm for Automatic Text Summarization

Abstract. Automatic text summarization has become a relevant topic due to the information overload. This automatization aims to help humans and machines to deal with the vast amount of text data (structured and un-structured) offered on the web and deep web. In this research a novel approach for automatic extractive text summarization called SENCLUS is presented. Using a genetic clustering algorithm, SENCLUS clusters the sentences as close representation of the text topics using a fitness function based on redundancy and coverage, and applies a scoring function to select the most relevant sentences of each topic to be part of the extractive summary. The approach was validated using the DUC2002 data set and ROUGE summary quality measures. The results shows that the approach is representative against the state of the art methods for extractive automatic text summarization.La generación automática de resúmenes se ha posicionado como un tema de gran importancia debido a la sobrecarga informativa. El objetivo de esta tecnología es el ayudar humanos y maquinas a lidiar con el gran volumen de información en forma de texto (estructurada y no estructurada) que se encuentra en la red y en la red profunda. Esta investigación presenta un nuevo algoritmo para la generación automática de resúmenes extractivos llamado SENCLUS. Este algoritmo es capaz de detectar los temas presentes en un texto usando una técnica de agrupación genética para formar grupos de oraciones. Estos grupos de oraciones son una representación aproximada de los temas del texto y estos son formados usando una función aptitud basada en cobertura y redundancia. Una vez los grupos de oraciones son encontrados, se aplica una función puntuación para seleccionar las oraciones mas relevantes de cada tema hasta que las restricciones de longitud del resumen lo permitan. SENCLUS fue validado en una serie de experimentos en los cuales se usò el conjunto de datos DUC2002 para la generación de resúmenes de un solo documento y se usò la medida ROUGE para medir de forma automática la calidad de cada resumen. Los resultados mostraron que el enfoque propuesto es representativo al ser comparado con los algoritmos presentes en el estado del arte para la generación de resúmenes extractivos.Maestrí

顔表情自動認識における西洋人と東洋人の基本的表情の違いに対する分析

Facial Expression Recognition (FER) has been one of the main targets of the well-known Human Computer Interaction (HCI) research field. Recent developments on this topic have attained high recognition rates under controlled and “in-the-wild” environments overcoming some of the main problems attached to FER systems, such as illumination changes, individual differences, partial occlusion, and so on. However, to the best of the author’s knowledge, all of those proposals have taken for granted the cultural universality of basic facial expressions of emotion. This hypothesis recently has been questioned and in some degree refuted by certain part of the research community from the psychological viewpoint. In this dissertation, an analysis of the differences between Western-Caucasian (WSN) and East-Asian (ASN) prototypic facial expressions is presented in order to assess the cultural universality from an HCI viewpoint. In addition, a full automated FER system is proposed for this analysis. This system is based on hybrid features of specific facial regions of forehead, eyes-eyebrows, mouth and nose, which are described by Fourier coefficients calculated individually from appearance and geometric features. The proposal takes advantage of the static structure of individual faces to be finally classified by Support Vector Machines. The culture-specific analysis is composed by automatic facial expression recognition and visual analysis of facial expression images from different standard databases divided into two different cultural datasets. Additionally, a human study applied to 40 subjects from both ethnic races is presented as a baseline. Evaluation results aid in identifying culture-specific facial expression differences based on individual and combined facial regions. Finally, two possible solutions for solving these differences are proposed. The first one builds on an early ethnicity detection which is based on the extraction of color, shape and texture representative features from each culture. The second approach independently considers the culture-specific basic expressions for the final classification process. In summary, the main contributions of this dissertation are: 1) Qualitative and quantitative analysis of appearance and geometric feature differences between Western-Caucasian and East-Asian facial expressions. 2) A fully automated FER system based on facial region segmentation and hybrid features. 3) The prior considerations for working with multicultural databases on FER. 4) Two possible solutions for FER with multicultural environments. This dissertation is organized as follows. Chapter 1 introduced the motivation, objectives and contributions of this dissertation. Chapter 2 presented, in detail, the background of FER and reviewed the related works from the psychological viewpoint along with the proposals which work with multicultural databases for FER from HCI. Chapter 3 explained the proposed FER method based on facial region segmentation. The automatic segmentation is focused on four facial regions. This proposal is capable to recognize the six basic expression by using only one part of the face. Therefore, it is useful for dealing with the problem of partial occlusion. Finally a modal value approach is proposed for unifying the different results obtained by facial regions of the same face image. Chapter 4 described the proposed fully automated FER method based on Fourier coefficients of hybrid features. This method takes advantage of information extracted from pixel intensities (appearance features) and facial shapes (geometric features) of three different facial regions. Hence, it also overcomes the problem of partial occlusion. This proposal is based on a combination of Local Fourier Coefficients (LFC) and Facial Fourier Descriptors (FFD) of appearance and geometric information, respectively. In addition, this method takes into account the effect of the static structure of the faces by subtracting the neutral face from the expressive face at the feature extraction level. Chapter 5 introduced the proposed analysis of differences between Western-Caucasian (WSN) and East-Asian (ASN) basic facial expressions, it is composed by FER and visual analysis which are divided by appearance, geometric and hybrid features. The FER analysis is focused on in- and out-group performance as well as multicultural tests. The proposed human study which shows cultural differences in perceiving the basic facial expressions, is also described in this chapter. Finally, the two possible solutions for working with multicultural environments are detailed, which are based on an early ethnicity detection and the consideration of previously found culture-specific expressions, respectively. Chapter 6 drew the conclusion and the future works of this research.電気通信大学201

O uso da Divergência de Kullback-Leibler e da Divergência Generalizada como medida de similaridade em sistemas CBIR

The content-based image retrieval is important for various purposes like disease diagnoses from computerized tomography, for example. The relevance, social and economic of image retrieval systems has created the necessity of its improvement. Within this context, the content-based image retrieval systems are composed of two stages, the feature extraction and similarity measurement. The stage of similarity is still a challenge due to the wide variety of similarity measurement functions, which can be combined with the different techniques present in the recovery process and return results that aren’t always the most satisfactory. The most common functions used to measure the similarity are the Euclidean and Cosine, but some researchers have noted some limitations in these functions conventional proximity, in the step of search by similarity. For that reason, the Bregman divergences (Kullback Leibler and I-Generalized) have attracted the attention of researchers, due to its flexibility in the similarity analysis. Thus, the aim of this research was to conduct a comparative study over the use of Bregman divergences in relation the Euclidean and Cosine functions, in the step similarity of content-based image retrieval, checking the advantages and disadvantages of each function. For this, it was created a content-based image retrieval system in two stages: offline and online, using approaches BSM, FISM, BoVW and BoVW-SPM. With this system was created three groups of experiments using databases: Caltech101, Oxford and UK-bench. The performance of content-based image retrieval system using the different functions of similarity was tested through of evaluation measures: Mean Average Precision, normalized Discounted Cumulative Gain, precision at k, precision x recall. Finally, this study shows that the use of Bregman divergences (Kullback Leibler and Generalized) obtains better results than the Euclidean and Cosine measures with significant gains for content-based image retrieval.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorDissertação (Mestrado)A recuperação de imagem baseada em conteúdo é importante para diversos fins, como diagnósticos de doenças a partir de tomografias computadorizadas, por exemplo. A relevância social e econômica de sistemas de recuperação de imagens criou a necessidade do seu aprimoramento. Dentro deste contexto, os sistemas de recuperação de imagens baseadas em conteúdo são compostos de duas etapas: extração de característica e medida de similaridade. A etapa de similaridade ainda é um desafio, devido à grande variedade de funções de medida de similaridade, que podem ser combinadas com as diferentes técnicas presentes no processo de recuperação e retornar resultados que nem sempre são os mais satisfatórios. As funções geralmente mais usadas para medir a similaridade são as Euclidiana e Cosseno, mas alguns pesquisadores têm notado algumas limitações nestas funções de proximidade convencionais, na etapa de busca por similaridade. Por esse motivo, as divergências de Bregman (Kullback Leibler e Generalizada) têm atraído a atenção dos pesquisadores, devido à sua flexibilidade em análise de similaridade. Desta forma, o objetivo desta pesquisa foi realizar um estudo comparativo sobre a utilização das divergências de Bregman em relação às funções Euclidiana e Cosseno, na etapa de similaridade da recuperação de imagens baseadas em conteúdo, averiguando as vantagens e desvantagens de cada função. Para isso, criou-se um sistema de recuperação de imagens baseado em conteúdo em duas etapas: off-line e on-line, utilizando as abordagens BSM, FISM, BoVW e BoVW-SPM. Com esse sistema, foram realizados três grupos de experimentos utilizando os bancos de dados: Caltech101, Oxford e UK-bench. O desempenho do sistema de recuperação de imagem baseada em conteúdo utilizando as diferentes funções de similaridade foram testadas por meio das medidas de avaliação: Mean Average Precision, normalized Discounted Cumulative Gain, precisão em k, e precisão x revocação. Por fim, o presente estudo aponta que o uso das divergências de Bregman (Kullback Leibler e Generalizada) obtiveram melhores resultados do que as medidas Euclidiana e Cosseno, com ganhos relevantes para recuperação de imagem baseada em conteúdo

Deep learning architectures applied to wind time series multi-step forecasting

Forecasting is a critical task for the integration of wind-generated energy into electricity grids. Numerical weather models applied to wind prediction, work with grid sizes too large to reproduce all the local features that influence wind, thus making the use of time series with past observations a necessary tool for wind forecasting. This research work is about the application of deep neural networks to multi-step forecasting using multivariate time series as an input, to forecast wind speed at 12 hours ahead. Wind time series are sequences of meteorological observations like wind speed, temperature, pressure, humidity, and direction. Wind series have two statistically relevant properties; non-linearity and non-stationarity, which makes the modelling with traditional statistical tools very inaccurate. In this thesis we design, test and validate novel deep learning models for the wind energy prediction task, applying new deep architectures to the largest open wind data repository available from the National Renewable Laboratory of the US (NREL) with 126,692 wind sites evenly distributed on the US geography. The heterogeneity of the series, obtained from several data origins, allows us to obtain conclusions about the level of fitness of each model to time series that range from highly stationary locations to variable sites from complex areas. We propose Multi-Layer, Convolutional and recurrent Networks as basic building blocks, and then combined into heterogeneous architectures with different variants, trained with optimisation strategies like drop and skip connections, early stopping, adaptive learning rates, filters and kernels of different sizes, between others. The architectures are optimised by the use of structured hyper-parameter setting strategies to obtain the best performing model across the whole dataset. The learning capabilities of the architectures applied to the various sites find relationships between the site characteristics (terrain complexity, wind variability, geographical location) and the model accuracy, establishing novel measures of site predictability relating the fit of the models with indexes from time series spectral or stationary analysis. The designed methods offer new, and superior, alternatives to traditional methods.La predicció de vent és clau per a la integració de l'energia eòlica en els sistemes elèctrics. Els models meteorològics es fan servir per predicció, però tenen unes graelles geogràfiques massa grans per a reproduir totes les característiques locals que influencien la formació de vent, fent necessària la predicció d'acord amb les sèries temporals de mesures passades d'una localització concreta. L'objectiu d'aquest treball d'investigació és l'aplicació de xarxes neuronals profundes a la predicció \textit{multi-step} utilitzant com a entrada series temporals de múltiples variables meteorològiques, per a fer prediccions de vent d'ací a 12 hores. Les sèries temporals de vent són seqüències d'observacions meteorològiques tals com, velocitat del vent, temperatura, humitat, pressió baromètrica o direcció. Les sèries temporals de vent tenen dues propietats estadístiques rellevants, que són la no linearitat i la no estacionalitat, que fan que la modelització amb eines estadístiques sigui poc precisa. En aquesta tesi es validen i proven models de deep learning per la predicció de vent, aquests models d'arquitectures d'autoaprenentatge s'apliquen al conjunt de dades de vent més gran del món, que ha produït el National Renewable Laboratory dels Estats Units (NREL) i que té 126,692 ubicacions físiques de vent distribuïdes per total la geografia de nord Amèrica. L'heterogeneïtat d'aquestes sèries de dades permet establir conclusions fermes en la precisió de cada mètode aplicat a sèries temporals generades en llocs geogràficament molt diversos. Proposem xarxes neuronals profundes de tipus multi-capa, convolucionals i recurrents com a blocs bàsics sobre els quals es fan combinacions en arquitectures heterogènies amb variants, que s'entrenen amb estratègies d'optimització com drops, connexions skip, estratègies de parada, filtres i kernels de diferents mides entre altres. Les arquitectures s'optimitzen amb algorismes de selecció de paràmetres que permeten obtenir el model amb el millor rendiment, en totes les dades. Les capacitats d'aprenentatge de les arquitectures aplicades a ubicacions heterogènies permet establir relacions entre les característiques d'un lloc (complexitat del terreny, variabilitat del vent, ubicació geogràfica) i la precisió dels models, establint mesures de predictibilitat que relacionen la capacitat dels models amb les mesures definides a partir d'anàlisi espectral o d'estacionalitat de les sèries temporals. Els mètodes desenvolupats ofereixen noves i superiors alternatives als algorismes estadístics i mètodes tradicionals.Arquitecturas de aprendizaje profundo aplicadas a la predición en múltiple escalón de series temporales de viento. La predicción de viento es clave para la integración de esta energía eólica en los sistemas eléctricos. Los modelos meteorológicos tienen una resolución geográfica demasiado amplia que no reproduce todas las características locales que influencian en la formación del viento, haciendo necesaria la predicción en base a series temporales de cada ubicación concreta. El objetivo de este trabajo de investigación es la aplicación de redes neuronales profundas a la predicción multi-step usando como entrada series temporales de múltiples variables meteorológicas, para realizar predicciones de viento a 12 horas. Las series temporales de viento son secuencias de observaciones meteorológicas tales como, velocidad de viento, temperatura, humedad, presión barométrica o dirección. Las series temporales de viento tienen dos propiedades estadísticas relevantes, que son la no linealidad y la no estacionalidad, lo que implica que su modelización con herramientas estadísticas sea poco precisa. En esta tesis se validan y verifican modelos de aprendizaje profundo para la predicción de viento, estos modelos de arquitecturas de aprendizaje automático se aplican al conjunto de datos de viento más grande del mundo, que ha sido generado por el National Renewable Laboratory de los Estados Unidos (NREL) y que tiene 126,682 ubicaciones físicas de viento distribuidas por toda la geografía de Estados Unidos. La heterogeneidad de estas series de datos permite establecer conclusiones válidas sobre la validez de cada método al ser aplicado en series temporales generadas en ubicaciones físicas muy diversas. Proponemos redes neuronales profundas de tipo multi capa, convolucionales y recurrentes como tipos básicos, sobre los que se han construido combinaciones en arquitecturas heterogéneas con variantes de entrenamiento como drops, conexiones skip, estrategias de parada, filtros y kernels de distintas medidas, entre otros. Las arquitecturas se optimizan con algoritmos de selección de parámetros que permiten obtener el mejor modelo buscando el mejor rendimiento, incluyendo todos los datos. Las capacidades de aprendizaje de las arquitecturas aplicadas a localizaciones físicas muy variadas permiten establecer relaciones entre las características de una ubicación (complejidad del terreno, variabilidad de viento, ubicación geográfica) y la precisión de los modelos, estableciendo medidas de predictibilidad que relacionan la capacidad de los algoritmos con índices que se definen a partir del análisis espectral o de estacionalidad de las series temporales. Los métodos desarrollados ofrecen nuevas alternativas a los algoritmos estadísticos tradicionales.Postprint (published version