1,721,111 research outputs found
La conservazione ex situ della biodiversità delle specie vegetali spontanee e coltivate in Italia: stato dell’arte, criticità e azioni da compiere
No full textGrid-Forming Converters in Weak Grids – The Case of a Mediterranean Island
No full textThe existing power network of a Mediterranean island is used as test bed for the study of grid-forming converter dynamics in weak grid conditions. The control scheme adopted for the converter falls in the category of the so called virtual synchronous machines (VSM). Particular attention is committed to the interaction between the converter controls and the synchronous machines dynamics. Time delays typically associated to measurements and filters are considered in the study, and included in the system model with a specific mathematical approach. Time-domain simulations show the occurrence of oscillatory instability in the system, with VSM and synchronous machines swinging against each other and progressively diverging. The modal analysis is performed for a deeper grasp of the system dynamics: the reasons of the instability are identified as the lack of damping in the system and the swinging interaction between grid-forming converter and synchronous machines. The opportunity of different corrective actions is analyzed and discussed, recognizing PSS-like control and active power phase compensation as the most suitable methods for the stabilization of the system
Grid-forming per la stabilità dei sistemi elettrici
No full textL’articolo descrive rischi e opportunità della tecnologia grid-forming applicata a convertitori elettronici di potenza di generatori rinnovabili e sistemi di accumulo per la stabilità oscillatoria dei sistemi elettrici. Infine, si presenta una discussione critica dei progetti pilota basati su tale tecnologia
COMPORTAMENTO IN TRANSITORIO DI IMPIANTI DI TERRA INTERCONNESSI SOGGETTI A FULMINAZIONE ATMOSFERICA
Full text linkL’attività di ricerca è orientata all’analisi del comportamento in transitorio, durante una eventuale condizione di fulminazione atmosferica diretta e/o indiretta, di impianti di terra interconnessi in sistemi elettrici in media tensione (MT). Usualmente l’interconnessione è realizzata attraverso la guaina metallica dei cavi in MT o mediante l’impiego di corde di rame nudo interrate parallelamente al percorso dei cavi stessi. Tale interconnessione, impiegata durante il normale servizio elettrico per limitare l’ampiezza dell’eventuale corrente di guasto a terra, contribuisce anche a modificare la distribuzione della corrente di fulmine in caso di fulminazione diretta o indiretta dell’impianto e, di conseguenza, le eventuali tensioni pericolose trasferite. L’approccio seguito è quello di campo (full wave) già impiegato con successo per l’analisi di un sistema di protezione dalle scariche atmosferiche (LPS) [1]. E’ basato sulla risoluzione numerica di una versione modificata dell'equazione integrale del campo elettrico (EFIE) nel caso thin-wire (1), nel dominio della frequenza, impiegando l’analisi di Fourier discreta (DFFT)
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
ON THE POTENTIAL IMPACT OF GREEN HYDROGEN FACILITIES ON THE PLANNING OF RES PLANTS IN SICILY
No full textA recent report on climate change and global warming, soil and oceans and the cryosphere [1]
highlighted the disastrous effects that would be produced if climate change were not stopped
Il diniego di autotutela nel diritto vivente, tra punti fermi, contraddizioni e perduranti incertezze
No full textIl saggio conduce una ricognizione, alla luce di significative pronunce della Suprema Corte, sui limiti, le condizioni e gli strumenti di tutela avverso un diniego di autotutela in materia tributaria, con l’obiettivo di suggerire una lettura evolutiva dell’istituto, anche alla stregua di importanti sentenze della Corte di giustizia
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
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