1,720,967 research outputs found
Mechanical properties updating of a non-uniform natural fibre composite panel by means of a parallel genetic algorithm
No full textThis article presents an investigation on the mechanical properties of a composite panel made of unidirectional flax fibres embedded in a polyethylene matrix (flax-PE). An initial set of mechanical properties was identified by classical static tests. Then, an experimental modal analysis was performed in order to get information on natural frequencies and mode shapes, which are related to the mechanical properties. The experimental modal results were compared with numerical ones, obtained through finite element model using the initial set of mechanical properties. Finally, in order to get a good numerical-experimental correlation, the mechanical properties throughout the panel were updated using an inverse modelling method based on parallel genetic algorithms
Numerical and experimental results for the frequency response of plates in similitude
Full text linkThe concept of structural similitude provides a powerful tool for engineers and scientists to predict the behaviour of a structure using an appropriate scaled model. Even tough theoretical and numerical investigations of similarity conditions or scaling laws have shown to be feasible, their accuracy is not necessarily guaranteed when these laws are applied to real (experimental) structures. Herein, structural scaling laws are investigated for the analysis of the dynamic response of simple flexural plates. Specifically, the possibility to define exact and distorted similitudes is discussed through numerical and experimental data. This paper focuses on exact and distorted similitudes in the analysis of the dynamic response of flexural plates. The similitude laws are defined by invoking the classical modal approach and looking for (in)equalities in the structural dynamic response. A total of seven aluminium rectangular plates with one clamped edge are modelled in finite elements and tested experimentally to study the effect of distorted similitudes and experimental variations in the performance of the predicted dynamic response
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
Evaluation of plates in similitude by experimental tests and artificial neural networks
No full textIn the last century, the introduction of similitude theory allowed engineers to define the conditions to design a scaled-up or down version of the full-scale structure by means of a set of tools known as similitude methods: the scaled structure can be tested more easily, and then, by using the scaling laws, the prototype behavior can be recovered. However, such a response reconstruction may become hard for complex structure under incomplete or distorted similitude frameworks. Machine learning methods, with their automating characteristics, may help to circumvent these difficulties. This work is divided into two parts. First, five clamped-free-clamped-free plates in similitude are experimentally tested. In the case of complete similitude, these laws allow to accurately reconstruct the response. When the similitude is distorted, these laws are not always valid, failing to predict the dynamic behavior in some of the frequency ranges. Then, the experimental results are used to validate the prediction and identification capabilities of artificial neural networks. The artificial neural networks proved to be robust to noise and very helpful in predicting the response characteristics and identifying the model type, although an adequate number of training examples is needed. Further tests proved that the number of samples is drastically reduced by choosing accurately the features
Support of Dynamic Measurements Through Similitude Formulations
Full text linkUp to now, similitude methods have been used in order to overcome the typical drawbacks of experimental testing and numerical simulations by reconstructing the full-scale model behavior from that of the scaled model. The novelty of this work is the application of similitude theory not as a tool for predicting the prototype dynamic response, but for supporting, and eventually validating, experimental measurements polluted by noise. Two Aluminium Foam Sandwich (AFS) plates are analyzed with Digital Image Correlation (DIC) cameras. First, an algorithm for blind source separation problems is used to extract information about the excitation; then, SAMSARA (Similitude and Asymptotic Models for Structural-Acoustic Research Applications) similitude method is applied to both the force spectra and velocity responses of prototype and model. The reconstruction of force and velocity curves demonstrates that the similitude results are coherent with the quality of the experimental measurements: when the spatial pattern in resonance is recognizable, then the curves overlap. Instead, when the displacement field of just one model is not well identified, the reconstruction exhibits discrepancies. Therefore, similitude methods reveal to be an interesting tool for understanding if a set of measurements is reliable or not and their application should not be underestimated, especially in the light of the expanding range of approaches which can extract important information from noisy observations
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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