1,720,961 research outputs found
Dynamic characterization of high performance materials for application to cultural heritage
Get PDFNatural hazards, such as earthquakes, can compromise the integrity of the cultural heritage with potentially devastating effects. The reduction of the seismic vulnerability of the cultural heritage constitutes a question of maximum importance especially in countries where vast cultural heritage combines with a medium or high seismic risk, such as in Italy. From the second half of the last century, the scientific community edited a number of important documents and charts for the conservation, reinforcement and restoration of the cultural heritage. The aim is to mitigate the seismic vulnerability of the cultural heritage. This research focused on high performance materials for applications aimed to structural and seismic protection of cultural heritage, with a special focus on historical masonry structures. In particular, the final aim is to define a self-diagnosis strategy for fibres, yarns and ties in view of efficient, non-invasive and reversible interventions on cultural heritage buildings. In order to set up the scene, the present thesis starts by introducing the reader to the seismic protection of cultural heritage thorough an extensive review on high performance materials, strengthening techniques and systems, taking care to highlight real world applications and limitations of their use. The second step of this work concerns in the mechanical and rheological characterization of high performance material fibres. The materials investigated are essentially Kevlar® 29 (para-aramid), Carbon and Silicon Carbide. To reach this goal, an extensive experimental testing campaign was conducted on fibres and yarns in accordance with specific protocols. A further step was defining appropriate damage indices for different materials, with a special focus on Kevlar® 29. Within the same research programme, a novel testing machine was also designed in cooperation with the Laboratory of Electronic Measurements of the Politecnico di Torino. A prototype-testing machine for dynamic testing on high resistance fibres was built using recycled materials and components. A distinctive feature of this machine is that it can apply to the sample any kind of dynamic excitation (random, impulse, harmonic etc.). A second testing campaign concerned the durability of Kevlar® 29 fibres, which are known to be sensitive to long-term exposure to UV radiation. Accordingly, for this campaign, the samples were artificially damaged by using UV lamps. The analysis of the resonance profiles allowed for the extraction of parameters such as the elastic moduli, quality factors, and non-linear coefficient for a set of fibres. In particular, non-linearity parameters derived from the Krylov-Bogoliubov method demonstrated to be consistent with the damage affecting the fibres. The final chapter of the dissertation concerns a new concept for a tie endowed with self-diagnosis properties, which are obtained by integrating a low cost testing device into the tie model. The self-diagnosis properties system of existing structures has an important role in the preservation of the cultural heritage because the best therapy is preventive maintenance. Specifically, the para-aramid tie system proposed for the reinforcement of historic building constitutes a non-invasive, reversible and repeatable intervention, as required by the main guidelines on preservation of cultural heritage
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
A new testing machine for the dynamic characterization of high strength low damping fiber materials
Get PDFThis work describes a novel method for measuring the damping, the elastic modulus and the non-linear behavior of high strength low damping fiber materials such as para-aramids, silicon carbide (SiC) and carbon. The method is based on resonant response characterization of a spring-mass system excited by a sine-wave forcing term which is applied as a vertical force to the suspended mass. The damping is obtained from the measured resonance quality factor Q, the elasticity modulus is calculated from the resonance frequency, and the non-linear coefficient is obtained with the backbone approach from resonance profile variations as a function of the forcing term amplitude. It is argued that the method is very sensitive, to the point that a maximum excitation amplitude of the order of a few percent of resistance is sufficient to obtain an estimate of the non-linear coefficient. This claim is supported by experimental results. A testing machine is also discussed, which provides the necessary sensitivity at such small excitation amplitudes and the capability of evaluating very small damping values, as expected in high strength low damping fiber materials. The sensitivity is guaranteed by an optical position sensor with sub-micron resolution. To evaluate small damping values, particular care has been taken to ensure that energy dispersions in the generator are much smaller than energy dispersions in the fibers themselves. Examples of dynamic characterization are shown for para-aramid, silicon carbide, and carbon fibers
Modelling of a road infrastructure adapted for dynamic inductive recharging for maintenance and monitoring
No full textWireless charging is an attractive technology that is expected to promote customer acceptance of electric vehicles in urban environment because it can improve convenience and sustainability. This paper analyzes various problems related to the interaction between the electric vehicle and the infrastructure adapted for inductive charging. From a structural point of view, both the dynamic properties and the long-term behaviour of these particular devices have to be investigated. In the present study, a model was developed to simulate vehicle behavior and analyze its impact on the infrastructure. Special models have been also used to predict the long-term behavior of the overall system, this allowing to define specific requirements for the installation of the system, as well as for its maintenance, life-cycle analysis and monitorin
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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