1,721,087 research outputs found
Identification of the modal masses of an UAV structure in operational environment
No full textIn the framework of Operational Modal Analysis, several methods have been developed to estimate the modal parameters, that is natural frequencies, damping ratios, and mode shapes of a structure in its operative conditions. However, it is not possible to directly estimate the modal masses associated to each mode shape due to the unknown excitation. The modal masses are usually evaluated from the analysis of the change of the modal parameters by testing the structure in correspondence of two mass configurations. In this paper the efficiency and the accuracy of two procedures for the estimate of the modal masses are assessed by performing laboratory vibration tests. Vibration response data recorded during flight tests of an unmanned aerial vehicle (UAV) are used for this purpose as well as a mass changing device was developed to produce the mass variation of the structure. Results from the traditional input/output experimental modal analysis and the operational modal analysis are compared in terms of modal parameters, modal masses, and synthesized frequency response functions
Using neural networks for F.E. model updating of structures in operational conditions
No full textIn this paper, a finite element model updating method based on neural networks is presented. The main objective of the paper is to identify the dynamic properties of a structure from response data recorded during operating conditions, extending the use of results from operational modal analysis to the neural networks-based updating methodologies. The neural networks used in this study have a feed-forward architecture and their inputs are the modal parameters, that is natural frequencies, damping ratios, and mode shapes of a structure in its operative conditions, whereas their outputs are the physical properties of the considered structure. Typically, the first step of neural networks is their training and it will be shown that trained neural networks are successful when simulated cases are considered but they have some limits when experimental data are used. For this reason an algorithm based on not-trained neural networks has been developed. Both numerical and experimental analyses carried out on simple structures will be presented to demonstrate the accuracy of the proposed updating approach
Closed-loop control of the smart spring. An analytical solution for the actuator model
No full textThe analytical modeling of the Smart Spring actuator for vibration reduction of periodically excited systems is performed. The mathematical model is developed in the frequency domain using the harmonic balance method, assuming that the solution is harmonic on the exciting frequency. Both the fixed-base and base-excited configurations are studied. It is shown that the Smart Spring transmissibility at the target frequency depends on only three dimensionless parameters associated with the stiffness modulation characteristics of the device for the fixed-base configuration and five dimensionless parameters for the base-excited configuration. The fundamental values for the Smart Spring closed-loop control are discussed
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
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