1,721,047 research outputs found
Performance of a Family of Surface Piercing Propellers
No full textExperimental tests have been performed on a systematic series of surface piercing propellers with varied number of blades (4 and 5) and pitch ratio (from 0.8 to 1.4). Some aspects of scaling the performance of this kind of propulsor have been investigated.
Influence of depth of immersion and shaft inclination is discussed and results for variations in these parameters are presented.
Regression equations are given describing the relationship of the thrust and torque coefficients for advance coefficients above the critical values.
This work is the result of a research on the performances of surface piercing propellers undertaken by the University of Genoa and was partly developed as a doctoral thesis on surface piaercing propellers
Performance of a Family of Surface Piercing Propellers
No full textExperimental tests have been performed on a systematic series of surface piercing propellers with varied number of blades (4 and 5) and pitch ratio (from 0.8 to 1.4). Influence of depth of immersion and shaft inclination is discussed and results for variations in these parameters are presented. Regression equations are given describing the relationship of the thrust and torque coefficients for advance coefficients above the critical values. Influence on Weber number is briefly considered, confirming results of previous works. This work is the result of a research on the performances of surface piercing propellers undertaken by the University of Genoa and was partly developed as a doctoral thesis
UTILIZZO DI MACROMODELLI PER LO STUDIO DELLA DOMANDA DI TRASPORTO AEREO DOMESTICA DEI PRINCIPALI PAESI EUROPEI
No full textIn questa nota vengono esaminati alcuni modelli per la macroanalisi della domanda di trasporto aereo, viene eseguita una loro applicazione alla domanda di trasporto aereo domestica dei principali paesi europei, è effettuato l'esame dei risultati del procedimento di stima, con particolare riguardo ai problemi di multicollinearità che possono sorgere nell'utilizzo dell'estimatore dei minimi quadrati omoscedastico.
Sono considerati i tipi di macromodello denominati: "corrente" e "parzialmente aggiustato". Sono riassunte alcune loro applicazioni, riportate in letteratura, relative al traffico aereo interno statunitense.
Vengono quindi esaminate le principali caratteristiche della domanda di trasporto aereo interna dei principali paesi europei: Italia, Francia, Spagna, Gran Bretagna e Germania. I due tipi di macromodello presi in considerazione sono poi applicati alla serie storica del traffico aereo interno dei principali paesi europei. Le variabili esplicative utilizzate nei modelli sono: il prodotto interno lordo pro capite, come variabile socioeconomica, e la tariffa media domestica per passeggero-chilometro, come attributo del servizio di trasporto. Variabili di questo tipo sono reputate essere quelle che influenzano maggiormente il livello generale della domanda di trasporto aereo.
I modelli considerati si riducono tutti ad un modello di regressione lineare multipla. E' esaminato il problema della multicollinearità: sono analizzati gli effetti, sulla qualità delle stime dei parametri del modello, dell'esistenza di relazioni di multicollinearità fra le variabili esplicative. Sono riportati i risultati del procedimento di stima, eseguito utilizzando l'estimatore dei minimi quadrati omoscedastico. Sono riportati, per i modelli in esame, gli indici di misura del "grado di multicollinearità": "variance inflaction factors" e "condition indexes". Sono inoltre riportate le matrici delle proporzioni delle varianze
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
La mobilità attratta da generatori di tipo commerciale: la definizione di una metodologia per il caso italiano
No full textRegioselective Copper-catalyzed Alkylation of 2.2.2-Acylnitroso Cycloadducts: Remarkable Effect of the Halide of Grignard Reagents
No full textRing opening with organometallic reagents of [2.2.2]-acylnitroso cycloadducts, including an enantioselective kinetic resolution of these compounds, has been accomplished for the first time. By the careful choice of reaction conditions, it was possible to obtain new cyclohexenyl hydroxamic acids with complete anti-stereoselectivity and a nice regioalternating control. A remarkable effect of the halogen of the Grignard reagent was observed during ring opening
Tomodensitométrie et syndrome de détresse respiratoire aiguë: physiopathologie et utilisation clinique.
No full text- …
