1,721,014 research outputs found
Design of a medium-access-control protocol for wireless sensor networks considering the battery state of charge and state of health
Full text linkTesis para optar al grado de Doctora en Ingeniería EléctricaLa disponibilidad de energía es una de las limitaciones que presentan las Redes de Sensores
Inalámbricas (WSN, Wireless Sensor Network). Tradicionalmente, las baterías han sido utilizadas para proveer energía a los nodos de sensores y al tener una vida útil limitada afectan
el tiempo de vida de la red. Soluciones como el uso de baterías de gran tamaño o el reemplazo
de ellas no son viables, debido al gran número de sensores que componen la red y a
que pueden ser desplegados en zonas de difícil acceso. Esta situación ha motivado que las
soluciones para la conservación de la energía en las WSNs se enfoquen en el desarrollo de
técnicas que actúen a nivel de las capas física y de enlace de datos, como es el caso de los
protocolos de Control de Acceso al Medio (MAC, Medium Access Control).
Los protocolos MAC son una de las soluciones ampliamente estudiadas y utilizadas porque
permiten un equilibrio entre la conservación de energía y otros parámetros críticos de la red,
como el rendimiento, latencia, reducción de colisiones y mensajes de control. También tienen
la facilidad de adaptarse a las nuevas aristas de trabajo que surgen al incorporar nuevas
tecnologías como lo son los Dispositivos de Recolección de Energía (EHD, Energy Harvesting
Device). Otro aspecto que está siendo considerado y estudiado en el diseño de los protocolos
MAC es la información que se puede extraer de la batería, ya que al estimar la capacidad
disponible de la misma, el mecanismo del Duty Cycling (DuC) puede ser ajustado con el
propósito de aumentar la eficiencia energética y por lo tanto, extender la vida útil de la red.
Es necesario desarrollar técnicas que incorporen un mecanismo de conservación de energía
que integre información de la batería a través de indicadores como el Estado de Carga (SOC,
State of Charge) y Estado de Salud (SOH, State of Health) para mejorar la eficiencia energética
en WSN. La idea de incorporar información de la batería se debe a que la capa MAC
está a cargo de controlar los modos de operación del nodo sensor, lo que está directamente
relacionado con la cantidad de corriente exigida a la batería. Conocidos los perfiles de uso de
la batería es posible estimar los indicadores SOC y SOH que se han utilizado ampliamente
en diversas aplicaciones para conocer la cantidad de energía disponible en la batería y la
degradación que ha sufrido la misma.
En este trabajo se propuso el desarrollo de un protocolo que actúa en la subcapa MAC y
que considera la información de la batería para tomar decisiones con respecto al tiempo activo
y de reposo del nodo de sensor, con la finalidad de promover el uso eficiente de la energía
y extender la vida útil de la red. Los resultados obtenidos validan esta nueva propuesta
de algoritmo y establecer pautas para guiar el diseño de protocolos MAC que se centren en
minimizar el consumo de energía teniendo en cuenta los dispositivos de recolección de energía
y la información de la batería
Implementation of the LMS Algorithm for Noise Cancellation on Speech Using the ARM LPC2378 Processor.
No full textOn this thesis project, the LMS algorithm has been applied for speech noise filteringand different behaviors were tested under different circumstances by using Matlabsimulations and the LPC2378 ARM Processor, which does the task of filtering in realtime. The thesis project is divided into two parts: the theoretical and practical part. In the theoretical part there is a brief description of the different aspects of signalprocessing systems, filter theory, and a general description of the Least-Mean-SquareAdaptive Filter Algorithm. In the practical part of the report a general description of the procedure will besummarized, the results of the tests that were conducted will be analyzed, a generaldiscussion of the problems that were encounter during the simulations will be mention,and suggestion for the problems will be given
Robust speech recognition in noisy and reverberant environments using deep neural network-based systems
Full text linkDoctor en Ingeniería EléctricaIn this thesis an uncertainty weighting scheme for deep neural network-hidden Markov model (DNN-HMM) based automatic speech recognition (ASR) is proposed to increase discriminability in the decoding process. To this end, the DNN pseudo-log-likelihoods are weighted according to the uncertainty variance assigned to the acoustic observation. The results presented here suggest that substantial reduction in word error rate (WER) is achieved with clean training. Moreover, modelling the uncertainty propagation through the DNN is not required and no approximations for non linear activation functions are made. The presented method can be applied to any network topology that delivers log likelihood-like scores. It can be combined with any noise removal technique and adds a minimal computational cost. This technique was exhaustively evaluated and combined with uncertainty-propagation-based schemes for computing the pseudo-log-likelihoods and uncertainty variance at the DNN output. Two proposed methods optimized the parameters of the weighting function by leveraging the grid search either on a development database representing the given task or on each utterance based on discrimination metrics. Experiments with Aurora-4 task showed that, with clean training, the proposed weighting scheme can reduce WER by a maximum of 21% compared with a baseline system with spectral subtraction and uncertainty propagation using the unscented transform.
Additionally, it is proposed to replace the classical black box integration of automatic speech recognition technology in human-robot interaction (HRI) applications with the incorporation of the HRI environment representation and modeling, and the robot and user states and contexts. Accordingly, this thesis focuses on the environment representation and modeling by training a DNN-HMM based automatic speech recognition engine combining clean utterances with the acoustic channel responses and noise that were obtained from an HRI testbed built with a PR2 mobile manipulation robot. This method avoids recording a training database in all the possible acoustic environments given an HRI scenario. In the generated testbed, the resulting ASR engine provided a WER that is at least 26% and 38% lower than publicly available speech recognition application programming interfaces (APIs) with the loudspeaker and human speakers testing databases, respectively, with a limited amount of training data.
This thesis demonstrates that even state-of-the-art DNN-HMM based speech recognizers can benefit by combining systems for which the acoustic models have been trained using different feature sets. In this context, the complementarity of DNN-HMM based ASR systems trained with the same data set but with different signal representations is discussed. DNN fusion methods based on flat-weight combination, the minimization of mutual information and the maximization of discrimination metrics were proposed and tested. Schemes that consider the combination of ASR systems with lattice combination and minimum Bayes risk decoding were also evaluated and combined with DNN fusion techniques. The experimental results were obtained using a publicly-available naturally-recorded highly reverberant speech data. Significant improvements in WER were observed by combining DNN-HMM based ASR systems with different feature sets, obtaining relative improvements of 10% with two classifiers and 18% with four classifiers, without any tuning or a priori information of the ASR accuracy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Implementation of the LMS Algorithm for Noise Cancellation on Speech Using the ARM LPC2378 Processor.
No full textOn this thesis project, the LMS algorithm has been applied for speech noise filteringand different behaviors were tested under different circumstances by using Matlabsimulations and the LPC2378 ARM Processor, which does the task of filtering in realtime. The thesis project is divided into two parts: the theoretical and practical part. In the theoretical part there is a brief description of the different aspects of signalprocessing systems, filter theory, and a general description of the Least-Mean-SquareAdaptive Filter Algorithm. In the practical part of the report a general description of the procedure will besummarized, the results of the tests that were conducted will be analyzed, a generaldiscussion of the problems that were encounter during the simulations will be mention,and suggestion for the problems will be given
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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