1,720,959 research outputs found
A Model of Engine-Propeller Coupling for the Dynamic Response of Ship’s Propulsion System
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Viscous‐inviscid coupling in free surface ship flows
No full textAn application of multidomain decomposition to the computation of the steady free surface flow past a ship hull is presented. Viscous effects are taken into account in the neighbourhood of solid walls and in the wake by the Reynolds averaged Navier‐Stokes equations, whereas the assumption of irrotationality in the external flow allows a description by a potential model. Free surface boundary conditions have been implemented in a linearized form at the undisturbed waterplane. Suitable matching conditions are enforced at the interface between the viscous and the potential regions. The numerical results obtained for two merchant ship forms (the HSVA tanker and the Series 60 hull) are compared with experimental data available in the literature. Copyright © 1995 John Wiley & Sons, Lt
Dynamic Loads on Fast Ferry Hull Structures Induced by the Engine-Propeller Coupling
No full textIn this paper the problem of the vibrations induced on the hull by the propulsion system is considered. Although the problem has been widely studied in the technical literature, some new aspects concerning the propulsion system model are here investigated. In particular the engine is modelled taking into account its exact crankshaft dynamics, leading to variable inertia effects and parametric excitation. The pulsating propeller torque in the hull wake is studied as well, by solving the flow about the propeller by a boundary element technique. The derived model allows an accurate calculation of the reaction forces transmitted by the engine-propeller system to the ship structures; in this way the characteristic time history of the vibrational motion of important parts of the ships can be predicted. The attention is focused on a typical fast passenger ship, the finite element model of which is developed. Preliminary test results are shown and the performed numerical simulations suggest that the global propeller-engine-structure model could be a useful tool in the frame of the optimization of the vibrational ship design
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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