1,721,012 research outputs found
Parametric Design Optimization of Multiple-repair Composite Structures
Full text linkLa riparazione di pannelli in materiale composito ha assunto sempre maggiore importanza a causa dell’aumento del loro utilizzo in ambito aeronautico, ad opera di compagnie come per esempio Airbus e Boeing. Esistono diverse tecniche di riparazione attualmente usate; tra queste, la riparazione mediante patch in metallo bullonata viene utilizzata per strutture in materiale composito spesse e molto sollecitate, oppure qualora sia necessaria una riparazione in tempi brevi di un danneggiamento di modesta entità. L’ottimizzazione strutturale della riparazione acquisisce importanza in quanto può permettere la riduzione del peso della riparazione a parità di carico sopportato dalla struttura riparata.
L’obiettivo principale di questo lavoro di tesi è stato realizzare un modello di un pannello in materiale composito che presenta stringer e rib; il danneggiamento, modellato di forma rettangolare, interessa lo stringer e lo skin, ed è riparato con una piastra metallica bullonata. Il modello è parametrico nella geometria del pannello e della riparazione, nel numero dei rinforzi, nel numero di danneggiamenti, nei materiali e layup. Con questo modello parametrico è stato possibile realizzare una pseudo-ottimizzazione per studiare l’interazione di due riparazioni. In particolare si sono analizzate due diverse configurazioni di danneggiamento: configurazione A, dove vi sono due cricche, una fissa e l’altra mobile, sullo stesso stringer; configurazione B, dove vi sono due cricche ognuna su uno stringer diverso, di cui una sola è mobile. Per ognuna di queste due configurazioni si analizzano tre posizioni diverse della cricca mobile e si confrontano i risultati numerici.
Successivamente è stato realizzato un modello di un pannello simile, con due stringer e due rib, che presenti il danneggiamento nella baia. Questo difetto non è riparato; l’obbiettivo infatti è analizzare l’influenza dei parametri di progettazione del pannello, quali layup e dimensione degli stringer, sulla capacità di carico residua. Per questo scopo è stata pensata un’ottimizzazione dei suddetti parametri utilizzando l’algoritmo genetico e avendo come obbiettivo la minimizzazione del peso complessivo della struttura e la minimizzazione del massimo stress di Von Mises.
I modelli numerici sono agli elementi finiti (FEM) e sono stati realizzati con il software commerciale Abaqus versione 6.13; sono stati scritti degli script in linguaggio Python che generano i modelli FEM all’interno di Abaqus. Con gli script è possibile variare i parametri di progettazione quali geometria del pannello, numero di danneggiamenti, condizioni di carico e così via. L’ottimizzazione è gestita interfacciando gli script in Python con il software MATLAB, e utilizzando l’algoritmo genetico già implementato nel software.
Gli sviluppi futuri di questo lavoro includono: una validazione sperimentale del modello; l’introduzione di un criterio di danneggiamento per il materiale composito (per esempio il criterio di Hashin); la modellazione del comportamento elasto-plastico dei bulloni per simulare la ridistribuzione del carico; il completamento del processo di ottimizzazione.The repair of composite panels is becoming more and more important as the use of composite materials for commercial aircraft is increasing, by companies such Airbus and Boeing. There are several repair techniques; among these, the repair with a metallic bolted patch is used for thick composite structures and for highly loaded composite structures, or when there is a minor damage with the need of a fast repair. The structural optimization of the repair then is becoming important as it can allow a weight reduction of the repair, keeping the same load carried by the repaired structure.
The main aim of this work is to develop a numerical model of a composite panel with stringers and ribs; the damage, modelled with a rectangular shape, affects both the stringer and the skin, and it is repaired with a metallic bolted patch. The model is parametric in the geometry of the panel and of the repair, in the number of stringers and ribs, in the number of damages, in the materials and layups. A pseudo-optimization was then carried with this model, for studying the interaction between two repairs. Two configuration were analysed: configuration A, where there are two cracks on the same stringer, one is fixed and the other is moving; configuration B, where there are two cracks, one on a single stringer, one is fixed and the other is moving. For these two configurations there are three position of the moving crack that are considered; the numerical results are then compared.
A similar model was then developed, with just two stringers and two ribs, with the damage in the bay. This damage is not repaired; the aim is to analyse the influence of the parameters of the panel, such as the layup and stringer dimensions, on the residual strength. For this reason, an optimization of these parameters was programmed, using genetic algorithm and using for objective function the minimization of the total weight of the structure and the minimization of the maximum Von Mises stress.
The models are finite element models and they were developed using Abaqus commercial software (version 6.13); the scripts that generate the FEM model were written in Python language. With these scripts, the parameters as geometry of the panel, number of damages, loading conditions and so on are easily changeable. The optimization procedure was carried connecting the Python scripts with MATLAB software, and using the genetic algorithm already provided by the software.
The future developments of this work can be an experimental validation of the model; the introduction of a damage criterion for composite material (for example the Hashin criterion); the modelling of the elaso-plastic behaviour of bolts for the simulation of load redistribution; the conclusion of the optimization process
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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