1,720,956 research outputs found
Multiple response levels of structures with wedge friction dampers
No full textWedge dampers are widely used in turbomachines to reduce the amplitude of blade vibrations. Computation of the forced response of turbine blades in the presence of these dampers will give non-unique solutions due to the possibility of having different contact forces that still satisfy the equilibrium. In the paper, the response variability, in terms of upper and lower limit, is investigated for a lumped-parameter system simulating multiple wedge dampers pressed between adjacent vibrating blades. An optimization algorithm is developed by considering, as further dofs of the system, a series of coefficients representing the ratio between the tangential force and the Coulomb limit, assumed as initial hypothesis in the construction of the hysteresis loop within the contact model. This algorithm maximizes or minimizes the loss factor of the system, allowing the response limits to be identified. Several combinations of preload and geometry of the dampers are considered, and the evolution of the variability of the dynamic response of the blades is then investigated
An Experimental Investigation on the Dynamic Response Variability of a Turbine Blade With Midspan Dampers
Full text linkThis paper addresses two main subjects. First, a novel test setup is described to experi-mentally study the nonlinear dynamic behavior of a turbine blade coupled with two mid-span dampers (MSDs). To this end, a representative turbine blade and midspan friction dampers are originally designed, and they are assembled to a special test rig which has been previously developed at Politecnico di Torino. Second, the variability of the dynamic response is intensively investigated with a purposely defined loading/unloading strategy. To better understand the inherent kinematics of the blade–damper interaction, contact forces are measured through the novel design of the experimental campaign. It is shown that multiple responses, which are obtained in different tests while keeping all user-controlled inputs nominally same, are due to nonunique contact forces that provide different static force equilibria on the damper. This outcome is further supported by the qualitative illustration of hysteresis cycles. This study contributes to the understanding of the response repeatability linked to the nonuniqueness of friction forces
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
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
Comparison between control-based continuation and phase-locked loop methods for the identification of backbone curves and nonlinear frequency responses
Full text linkControl-based continuation (CBC) and phase-locked loops (PLL) are two experimental testing methods that have demonstrated great potential for the non-parametric identification of key nonlinear dynamic features such as nonlinear frequency responses and backbone curves. Both CBC and PLL exploit stabilizing feedback control to steer the dynamics of the tested system towards the responses of interest and overcome important difficulties experienced when applying conventional testing methods such as sine sweeps to nonlinear systems. For instance, if properly designed, the feedback controller can prevent the system from exhibiting untimely transitions between coexisting responses or even losing stability due to bifurcations. This contribution aims to highlight the similarities that exist between CBC and PLL and present the first thorough comparison of their capabilities. Comparisons are supported by numerical simulations as well as experimental data collected on a conceptually simple nonlinear structure primarily composed of a thin curved beam. The beam is doubly clamped and exhibits nonlinear geometric effects for moderate excitation amplitudes
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