1,720,966 research outputs found
A Unified Scheme for Processing, Recovery, and Quality Improvement of Synchrophasor Data
Full text linkRÉSUMÉ: Les applications de l'unité de mesure de vecteur de phase (PMU) ont considérablement évolué ces dernières années. La prolifération des applications basées sur les synchrophaseurs nécessite le développement de méthodes novatrices et efficaces de réseautage, de traitement, d'amélioration de la qualité, et d'archivage de données. L'une des fonctions clés des réseaux synchrophaseurs est le concentrateur de données de vecteurs de phase (PDC) qui collecte les données des PMUs transmises à partir de différents lieux géographiques du réseau électrique, puis les transmet aux applications cibles. Les natures incertaines des systèmes de communication et des PMUs limitent les performances des PDC et compromettent les applications en imposant des délais excessifs, des pertes de données, des erreurs de mesure, et du bruit. Le délai, la disponibilité et la qualité des données déterminent si un réseau des synchrophaseurs peut prendre en charge certaines applications. De plus, un réseau des synchrophaseurs efficace doit être capable de traiter et d'archiver des quantités massives de données. Cette thèse propose une solution unifiée pour améliorer la disponibilité, les délais et la qualité des données de synchrophaseurs. Les principaux algorithmes de la solution proposée sont la coordination optimale de PDCs, la récupération de données synchrophaseurs manquantes, et la compression efficace pour l'archivage. Les algorithmes proposés fonctionnent en temps réel et compatibles avec toutes les exigences des applications de données de synchrophaseurs. Les modèles mathématiques du réseau de synchrophaseurs sont développés et les paramètres des PDCs sont ajustés de manière optimale pour maximiser le débit des données fournies à l'application dans les limites de temps spécifiées. L'algorithme temps réel de la récupération des données de synchrophaseurs manquantes utilise un problème non-convexe de complétion de matrices (MC) avec la pénalité quasi-norme de Schatten-q. L'algorithme d'approximation de rang réduit proposé est utilisé pour la réduction de bruit dans les données. Enfin, la méthode de compression proposée comprend une technique de réduction de dimensionnalité basée sur la décomposition en valeurs singulières (SVD) et un algorithme de partitionnement progressif. L'algorithme de partitionnement sépare les données en différentes partitions selon leurs conditions, par exemple, les conditions normales d'opération, les perturbations et les défauts. La dimensionnalité de ces partitions est réduite en rejetant les modes SVD dominés par l'erreur de mesure PMU. De nombreux tests numériques sont effectués à l'aide de données de terrain et synthétiques de PMU pour évaluer les performances des algorithmes proposés. ABSTRACT: The applications of phasor measurement unit (PMU) have significantly matured in recent years. The proliferation of synchrophasor-based applications necessitates the development of novel and efficient data networking, processing, quality improvement, and archiving methods. One of the key functions of synchrophasor networks is phasor data concentrator (PDC) that collects PMU data from different locations of the electrical grid, and then transmits them to target applications. The uncertain natures of the communication system and PMUs limit the performance of PDCs and compromise applications by imposing excessive latencies, data loss, measurement error, and noise. Data latency, availability, and quality dictate whether a synchrophasor network can support particular applications. Moreover, an efficient synchrophasor network must be capable of processing and archiving massive amounts of data. This thesis proposes a unified scheme to improve the availability, timeliness, and quality of the synchrophasor data. The proposed scheme comprises three main algorithms, namely, optimal coordination of PDCs, missing synchrophasor data recovery, and efficient compression for archiving. The proposed algorithms are real-time and compatible with all the requirements of the synchrophasor data applications. Mathematical models of the synchrophasor network are developed, and the parameters of PDCs are optimally designed to maximize application throughput within the specified time constraints. The real-time algorithm for the recovery of missing synchrophasor data employs a nonconvex matrix completion (MC) problem with the Schatten-q quasi-norm (lq) penalty. The proposed low-rank approximation algorithm is employed to suppress the noise in data. Finally, the proposed compression method includes a singular value decomposition (SVD)-based dimensionality reduction technique and a progressive partitioning algorithm. The partitioning algorithm separates data into different partitions according to their conditions, e.g., normal operating conditions, disturbances, and faults. The dimensionality of these partitions is reduced by rejecting the SVD modes dominated by PMU measurement error. Extensive numerical tests are performed using field and simulated PMU data to evaluate the performance of the proposed algorithms. The proposed optimal coordination of PDCs significantly reduces the end-to-end latency in networks that use legacy and non-legacy communications. The recovery of consecutive and simultaneous missing data points confirms the advantages of the proposed MC algorithm, especially during disturbances and events. Finally, the results show that the proposed compression method significantly achieves high compression ratio (CR) while preserving critical information of different operating conditions
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
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
Design and Implementation of a Centralized Disturbance Detection System for Smart Microgrids
Full text linkRÉSUMÉ: L'excursion de fréquence et de tension sont parmi les défis nombreux qui se posent aux microréseaux. La détection des perturbations peut être effectuée par le système de surveillance centralisé de micro-réseaux qui utilise des données de synchrophasor rapportées à partir de différents noeuds. Les réseaux de communication de synchrophasor présentent des retards et des Pertes de paquets qui peuvent détériorer l'intégrité des données et donc compromettre la fiabilité des systèmes de surveillance et de contrôle des micro-réseaux intelligents. Ce mémoire présente un nouveau concentrateur de données de vecteurs de phase avancé (APDC) capable de contrer les manques de la communication et d'améliorer la qualité des ressources de la production décentralisée (DER) dans les micro-réseaux. L'APDC proposé utilise un système de compensation adaptatif pour obtenir une estimation efficace des éléments de données manquants. L'estimateur adaptatif utilise le taux de changement d'éléments de données pour choisir entre l'estimateur LMMSE et un estimateur basé sur les dérivés pour prédire les valeurs futures des éléments de données. Si, à un instant donné, les éléments de données synchrophasors de certaines unités de mesure de phasor (PMU) manquent, les valeurs estimées sont utilisées pour compenser les données manquantes. En outre, une unité de surveillance est proposée pour détecter de manière fiable les excursions en fréquence et identifier les DERs affectés par les îlotages. L'unité de surveillance utilise un algorithme de détection centralisé élaboré qui traite les données de fréquence pour distinguer entre l'îlotage possible des DERs et les perturbations du réseau de distribution. L'APDC proposé est développé sur la plate-forme OpenPDC en temps réel et sa performance est évaluée à l'aide d'une configuration expérimentale comprenant trois PMUs, un réseau de télécommunications, des interrupteurs, et un concentrateur de données de vecteurs de phase classique (PDC). Les résultats expérimentaux confirment une intégrité des données de haut niveau dans les conditions normales et perturbées des micro- réseaux. Des études sur l'effet du bruit de mesure montrent que l'APDC proposé est même efficace en présence de bruits sévères. De plus, une détection rapide et fiable des événements d'îlotage est obtenue en raison de l'amélioration considérable du temps de détection même en cas de pertes de données sévères et de bruit de mesure. Enfin, la performance de l'APDC proposé est comparée à une méthode d'estimation existante. Les résultats montrent l'avantage important de l'APDC, en particulier dans des conditions perturbées. ABSTRACT: Microgrids are subject to various disturbances such as voltage transients and frequency excursions. Disturbance detection can be performed by a microgrid centralized monitoring system that employs synchrophasor data reported from different nodes within the microgrid. Synchrophasor communication networks exhibit delays and packet dropout that can undermine the data integrity and hence compromise the reliability of the monitoring and control systems of the smart microgrids. In this thesis, an advanced phasor data concentrators (APDC) is proposed that is capable of counteracting the communication impairments and improving the quality of monitoring of distributed energy resources (DERs) in microgrids. The proposed APDC utilizes an adaptive compensation scheme to achieve an efficient estimate of missing data elements. The adaptive estimator employs the rate of change of data elements to choose between the vector linear minimum mean square error (LMMSE) and the derivative-based estimators to predict the future values of data elements. Whenever the synchrophasor data elements of some phasor measurement units (PMU) are missing, the estimated values are used to compensate for the missing data. Moreover, a monitoring unit is proposed to reliably detect frequency excursions and identify the DERs affected by islanding events. The monitoring unit utilizes an elaborate centralized detection algorithm that processes frequency data to distinguish between possible islanding of DERs and disturbances occurred within the host grid. The proposed APDC is developed on a real-time OpenPDC platform and its performance is evaluated using an experimental setup including three PMUs, communication links, switches, and a conventional phasor data concentrator (PDC). The experimental results confirm a high-level data integrity under both normal and disturbed conditions. Studies on the effect of measurement noise show that the proposed APDC is even efficient in the presence of noise. Moreover, fast and reliable detection of islanding events is achieved even under severe data losses and measurement noise. Finally, the performance of the proposed APDC is compared with a recently proposed estimation method that shows the significant advantage of the APDC, especially under disturbed conditions
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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