1,720,961 research outputs found
Vibration analysis of shaft-bladed disk system by using substructure synthesis and assumed modes method
No full textAn analytical substructure synthesis and assumed modes method is developed to investigate the effect of the flexibility of a bladed disk assembly on the vibrational modes of a flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments and centrifugal stiffening effects are taken into account. Then the coupled vibrations between the shaft and bladed disk are extensively investigated, by using simplistic models, as the shaft rotational speed and the pretwist and stagger angles of blade are varied. (C) 1996 Academic Press Limite
Vibration analysis of a rotor with multiple flexible disks using assumed modes method
No full textAn assumed modes method is developed to investigate the effect of multiple flexible disks on the vibrational modes of a flexible rotor system. The analysis rotor model consists of multiple disks on a flexible shaft, as used for steam turbines or computer storage devices. In modeling the system, centrifugal stiffening and disk flexibility effects are taken into account. To demonstrate the effectiveness of the method a hard disk drive spindle system commonly used in personal computers and a simple flexible rotor system with two disks are selected as examples. In particular, the dynamic coupling between the vibrational modes of the shaft and the duplicate disks is investigated with the shaft rotational speed varied
Evaluation of the longitudinal coupled vibrations in rotating, flexible disks spindle systems
No full textThe natural frequencies and modes of the longitudinal coupled vibrations in a flexible shaft with multiple flexible disks are determined through a substructure synthesis technique. The analysis rotor model consists of multiple flexible disks attached to a flexible shaft with varying annular cross-section, as used for steam turbines or computer storage devices. In modelling the system, disk flexibility and centrifugal stiffening effects are taken into account. Commercial computer hard disk drive spindle systems are selected as illustrative examples. In particular, the effects of disk flexibility on the longitudinal coupled vibrations between the shaft and disks are investigated with varying spindle rotational speed. The results indicate that the substructure synthesis technique allows a clear physical insight into the effect of disk flexibility with reasonable computational effort. (C) 1997 Academic Press Limited
Tuning of simulated natural frequencies for a flexible shaft multiple flexible disk system
No full textThe vibration of a flexible shaft coupled with multiple flexible disks is investigated by using a substructure synthesis technique with the assumed modes method to be compared with experimental results. According to the nature of coupling with the rotor, disk vibratory modes are classified into three groups: uncoupled disk modes with more than one nodal diameters, umbrella modes coupled with the shaft longitudinal vibrations and disk modes with a single nodal diameter coupled with the shaft bending vibrations. The natural frequencies and mode shapes for each group are calculated by employing different solution and tuning techniques. It is shown that the tuning technique is capable of accurately predicting the natural frequencies of the complicated coupled vibratory system. (C) 1997 Academic Press Limited
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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