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Vibration characteristics of smart sandwich beams embedded with magnetorheological elastomer cores
No full textMagnetorheological Elastomer (MRE) material consisting of a natural or synthetic rubber filled with micron sized iron particles is a smart material whose properties can be controlled by external excitation. Due to rubber-like properties, MRE maybe appropriate to apply as a core material in sandwich structures. In this paper, the dynamic characteristics of an MRE core embedded smart sandwich beam are investigated. An analytical model based on Frostig’s high order beam theory is enhanced to include viscoelastic material properties and their frequency dependence. In numerical simulations, sandwich beam-like structures with varying portions of MRE core and different boundary conditions are considered. Based on numerical study, mode shapes are changed at some particular frequencies depending on the strength of magnetic field. The maximum change of the resonant frequency is up to 12% and the first resonant peak decreases by about 8dB due to increased damping in MRE when magnetic field applied. MRE core embedded sandwich beam are shown as being able to achieve adjustable stiffness and damping to design tuneable vibration absorber for applications in ship structures
Power flow analysis for a floating sandwich raft isolation system using a higher-order theory
Get PDFA higher-order sandwich theory is implemented in conjunction with an equivalent mobility-based power flow progressive method to determine power flow for a sandwich configured floating raft vibration isolation system. The power spectrum changes in whole frequency range effectively when core materials’ properties change. It is also shown that the loss factors of the sandwich configured floating raft influence the power flow transmitted to the foundation effectively in the medium- to high-frequency range and that the resonant peak cannot be avoided by increasing damping only in high-frequency ranges which is not found in floating raft isolation systems with isotropic beams
Characterisation of magnetorheological elastomer materials for the core of smart sandwich structures
No full textThis paper presents results from tests carried out on the effect of magnetorheological elasotmer (MRE) material make-up, processing features and cure under the magnetic field with respect to the volume of iron particles on shear properties. As core material of smart sandwich structure, performance characterization of the smart function in terms of curing time, air bubble effect and the volume of iron particles of MRE is explored. The purpose of this paper is to find out storage shear modulus and loss factor of MRE specimens and to explore the ideal volume fraction of iron particles, curing time under magnetic field and air bubble effect to maximize shear modulus changes. Since shear properties of MRE changes dominantly in small strain ranges, MRE is shown as being a core material of a sandwich beam which achieves adjustable stiffness
Vibration characteristics of sandwich beams with steel skins and magnetorheological cores
No full textMagnetorheological elastomer (MRE) cored sandwich beams with steel skins offer potentially advantageous features when used in the context of structural dynamics. Modelling of the dynamic behaviour is undertaken in this investigation by adopting a higher order sandwich beam theory. Frequency responses from the theoretical modelling are compared with experimental results on MRE cored sandwich beams. The experimental responses are generated from a specially designed test rig to study dynamic behaviour, damping effects, localised magnetic field effects and energy dissipation with varying topology. A numerically based parametric study is conducted to find the optimum geometry for skins and core material to enhance damping performance. Under the same magnetic field strength, sandwich beams with thinner skins and thicker MRE core dissapate more vibration energy. Correlation between the experimental results and numerical studies has been found to be reasonably goo
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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