1,720,954 research outputs found
The role of load models and reactive power support during large frequency transients
No full textThe goal of this work is to study the different dynamic behavior of the Italian electric power system, when subject to large disturbances, in relation to adopted load model and reactive power compensation devices considered for the network. Effectiveness of Defence Plans has already been proved by system Operators, but little attention is paid sometimes to the influence of used models. The adoption of a realistic load model implies a better representation of the system: in particular, the conclusions are that if the load is modeled as dynamic and voltage and frequency dependent, frequency perturbations resulting from the simulated contingencies are less dangerous as compared to more simplified models. Furthermore, the possibility to support voltages at particular buses damps voltage transient consequent to large perturbations and avoids further disconnection of loads, keeping the same security level. The conclusions are supported by tests carried out both on a relatively small portion of the Italian system (Sicily) and on a larger area (central and southern part)
Load modeling and reactive support to handle large disturbances
No full textLAUREA MAGISTRALELo scopo di questa Tesi è quello di dimostrare come il modello di carico utilizzato e la presenza nel sistema elettrico di compensatori sincroni per la compensazione di potenza reattiva influenzano il comportamento a regime e dinamico della rete, a seguito di grandi perturbazioni. Lo studio è stato effettuato su un modello di rete che rappresenta il sistema elettrico italiano di alta e altissima tensione a metà del 2015; la stretta collaborazione con Terna SpA, l'operatore che gestisce la rete di trasmissione italiana, ha permesso di sviluppare uno studio che si focalizza su aspetti mirati dell'analisi di rete, riguardanti eventuali miglioramenti da apportare alla rete e tuttora in fase di verifica. Nel particolare, vengono studiati gli effetti che derivano dall’utilizzo di un modello dinamico di carico comprendente la dipendenza da tensione e frequenza. Se guasti singoli e multipli vengono simulati, ne consegue che il Piano di Difesa, necessario per alcuni casi a ripristinare una situazione di equilibrio in tempi rapidi ed in modo affidabile, è impiegato in modalità e tempi diversi. Un generale miglioramento si nota sia per quanto riguarda il modello di carico che per l'adozione di compensazione di potenza reattiva, in termini di maggior controllo delle tensioni, dei flussi di potenza e delle quantità di carico alleggerito durante le procedure di emergenza.The goal of this Thesis is that of study the different dynamic behavior of the Italian electric power system, when subjected to large disturbances, in relation to adopted load model and reactive power compensation devices considered for the network. Effectiveness of Defence Plans has already been proved by system Operators, but it is tested here once again, both on a relatively small portion of the network (Sicily) and on a larger area (central and southern Italian system). The adoption of a more realistic load model implies a better representation of the system: in particular, the conclusions are that if the load is modeled as dynamic, voltage and frequency dependent, frequency perturbations resulting from the simulated contingencies are less dangerous if compared to more simplified system models. Furthermore, the possibility to support voltages in particular buses improves steady-state power flows and damps voltage transient consequent to large perturbations; they also avoid further disconnection of loads, keeping the same security level
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
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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