1,721,035 research outputs found
Water jet cutting technique for PMC
No full textAmong the different cutting techniques employed in machining polymer composite materials, water jet (WJ) and abrasive water jet (AWJ) one is very interesting techniques. The present paper analyzes the performance of a non-traditional cutting methodology, water jet WJ, and abrasive AWJ, used for machining PMC materials. In particular, the WJ technique has been water jet, applied to the three major class of PMC materials (i.e. GFRP, CFRP and KFRP) in order to compare the quality of the cuts and to assess whether this methodology is suitable to be applied to any of the testes PMC materials. The experimental set-up was mostly split in two phases: -cuts -observation and analysis of the cut superficies by means of image analysis techniques
Analisi e progettazione di azionamenti ad alta frequenza, modulari e ad elevato livello di integrazione
No full textGli azionamenti integrati -intesi come l’insieme di macchina elettrica e convertitore di potenza racchiusi all’interno di uno stessa struttura meccanica- sono stati introdotti all’inizio degli anni ’90. Nelle prime realizzazioni i problemi termici, meccanici e di limitata potenza specifica lato convertitore, non ne hanno consentito la diffusione sul mercato, nonostante avessero peculiarità tali da renderli vantaggiosi. Tuttavia, a seguito di recenti sviluppi nel campo dell’elettronica di potenza, introdotti dai semiconduttori ”wide bangap”, tali strutture sono state oggetto di un progressivo interesse.
Gli switch ai Nitruri di Gallio od ai Carburi di Silicio permettono invero di operare a frequenze di switching ed a temperature operative ben maggiori di quelle ottenibili con i tradizionali componenti al Silicio, pur preservando redimenti elevati. La maggiorazione delle temperature operative ammesse mitiga le problematiche termiche; allo stesso tempo, il funzionamento ad alte frequenze conduce ad una diminuzione intrinseca dei pesi e dei volumi dei componenti passivi, calmierando le problematiche di tipo meccanico.
Dal punto di vista della macchina elettrica, le alte frequenze di switching aprono la strada a macchine ad elevato numero di poli ed elevata velocità di rotazione, le quali sono naturalmente caratterizzate da coppie e potenze specifiche maggiori. Va evidenziato però, che se non opportunamente trattate esse sono causa di perdite aggiuntive.
Questa tesi di dottorato esplora l’utilizzo dei semiconduttori di ultima generazione negli azionamenti ad elevato grado di integrazione di tipo modulare, caratterizzati da un’elevata resilienza al guasto. Al fine di beneficiare appieno dei vantaggi di questa soluzione, e di limitarne gli svantaggi, viene proposto l’impiego della macchina elettrica a flusso assiale a magneti permanenti con avvolgimento di tipo coreless ed avente un rapporto poli-bobine frazionario. Nella tesi vengono inoltre sviluppati gli strumenti per l’analisi e la progettazione della macchina elettrica e del convertitore di potenza; di entrambi vengono costruiti dei prototipi, la cui sperimentazione al banco prova fornisce i dati per la
validazione finale degli argomenti trattati nel lavoro di tesi
Image analysis of millistructure for mechanical characterization of aluminum foam
No full text[No abstract available
Progettazione e realizzazione di un apparato per lo studio del comportamento biomeccanico della ricostruzione del tendine crociato in condizione di trauma distorsivo
No full text
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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