1,720,963 research outputs found
Prestazioni limite di cavi per AAT su lunghe distanze
No full textNella memoria vengono esposte procedure di analisi (per collegamenti trifase in corrente alternata realizzati con cavi AAT) fondate sulle classiche equazioni di trasmissione alle funzioni iperboliche, ma organizzate in modo da individuare tutti i regimi equilibrati compatibili con i vincoli posti dall'ampacity, dai livelli di tensione e dalle lunghezze previste per i cavi stessi; le procedure conducono a efficienti e significative rappresentazioni grafiche delle prestazioni ottenibili (espresse dalle potenze complesse conseguibili nell'ambito dei quattro quadranti): tali grafici, denominati "capability chart", costituiscono strumenti indispensabili per compendiare simultaneamente tutti i regimi ammissibili in un collegamento di lunghezza prefissata, e formano una valida guida per confrontare le diverse prestazioni; introdotto poi il concetto di Potenza Attiva Trasmissibile (PAT), si perviene a un originale diagramma, che permette di collocare con chiarezza la Lunghezza d'Attitudine alla Trasmissione (LAT) nel contesto dei problemi in gioco. Le capability chart sono di agevole costruzione per qualsiasi tipo di linea riconducibile a parametri uniformemente distribuiti e si rivelano pertanto assai utili per condurre confronti immediati tra le diverse prestazioni realizzabili nei cavi o in altri tipi di elettrodotti
Analysis of Inertial response and primary frequency power control provision by doubly fed induction generator wind turbines in a small power system
No full textExpansion Var planning model in a meshed/mixed AC/DC network
No full textThe importance of wind power generation has risen
in the last years so much to be considered the most important and
affordable renewable energy source with a growing rate faster
than other mainstream technologies in the word. Due to the lack
of land resources and some environmentalist opposition, the wind
strategy is now looking at offshore installations. This requires
new criteria to set out the appropriate architecture for future
offshore grids. The use of HVAC Cables and LCC (Line
Commutated Convertion) and VSC (Voltage Source Conversion) technologies stress the importance of extending the long-term expansion planning to the var support. Coping adequately with the problem of the voltage security assessment in a long-term expansion planning, is the purpose of this work. In this paper a model for the reactive expansion planning is proposed in the presence of a meshed AC/DC grid
Verso le Supergrid: il caso irlandese
No full textGli obiettivi di politica energetica dell’UE al 2050 impongono la necessità di sfruttare siti di generazione da fonte rinnovabile caratterizzati da elevata potenza disponibile ma distanti dai centri di carico. Ciò pone nuove sfide per la realizzazione di “autostrade” per l’energia elettrica, le Super Grid
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
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