1,720,954 research outputs found
Modeling of geometrical stiffening in a rotating blade—A review
Full text linkThe present work reviews different approaches adopted for modeling the geometrical or centrifugal stiffening of a beam due to rotation about an axis perpendicular to its longitudinal axis. The longitudinal displacement of the beam consists of three components: the axial displacement of the neutral axis (elastic extension), displacement associated with rotation of the plane section and the displacement due to the foreshortening effect. A widely used approach for modeling the geometrical stiffening is based on the foreshortening effect, which essentially is the longitudinal shrinkage due to the transverse motion of the beam. This approach uses nonlinear strain–displacement relations. As a result, the equations of motion and associated boundary conditions are nonlinear. The geometric stiffening terms in the nonlinear models are fundamentally a linear/quadratic function of the high-frequency axial elastic deformation. Various nonlinear models are discussed and summarized based on the different approximations of the strain–displacement relation. The solution procedure of these nonlinear models is complicated and computationally expensive due to coupling between high-frequency axial and low-frequency bending modes. Simplifying the model by direct linearization of the equations of motion eliminates the geometrical stiffening term resulting in an incorrect model. Different approaches to include geometrical stiffening terms in the linear model are discussed. One of the approaches is linearizing the nonlinear terms arising from the coupled axial-transverse motion around the steady-state axial solutions. The steady-state axial equilibrium equation can be linear or nonlinear depending on the type of strain measure employed. A comparison of the solution of these different linear/nonlinear steady-state axial equilibrium equations is presented. The applicability of these models based on the steady-state axial equations is tested, and the rotation speed limit within which these models are valid is also discussed. In another approach, the equations of motion are derived using a time-independent centrifugal force. The resulting equations are equivalent to those governing the transverse vibrations of beams subject to an external axial force. Nevertheless, another approach proposed by Kane et al. (1987) uses stretch as a variable in the formulation instead of the axial displacement. The linear geometrical stiffening models are discussed in detail. Further, the effects of geometric properties of the blade, such as taper, twist angle, pre-setting angle and asymmetry in cross-section on the modal characteristics are brought out. A comparison of the different beam theories used in studying the dynamics of rotating blades is also presented
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
Modal analysis of a rotating twisted and tapered Rayleigh beam
No full textFree vibration analysis of a twisted, double-tapered blade mounted on a rotating disk undergoing overall motion is presented here. The Lagrangian approach is adapted to study the modal characteristics of the blade modeled as a rotating Rayleigh beam. The expressions for the kinetic energy and potential energy of the cantilever blade are derived using hybrid deformation variables. The continuous deformation variables in these equations are discretized using a series of basis functions that satisfy all boundary conditions of the cantilever beam. The equations governing the coupled stretch–bending–torsion motion of the rotating blade are derived using Lagrange’s approach. The equations are then transformed into a non-dimensional form which are then solved for the eigenvalue problem for the modal characteristics of the blade. The results of the present model are verified with the results available in the literature. The variation of the natural frequencies with the rotating speed, taper ratio and pre-twist angle is presented. The tuned angular speed of the blade at which the angular frequency matches with any of the natural frequency of the blade resulting in the resonance is investigated. The Campbell diagram is plotted for the specific problem to identify the resonance where the natural frequency matches with the harmonics of the rotating speed. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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