1,720,953 research outputs found
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
A methodology for the experimental characterisation and computational modelling of Nitinol wires used in stent-graft devices
Get PDFStent-grafts are medical devices designed to treat abdominal aortic aneurysms (AAAs). These devices are usually composed of a Nitinol wireframe and a fabric graft. The design of next generation stent-grafts is directed towards a very low-profile when compacted. Such devices can treat narrow access vessels and tortuous anatomies while inducing less trauma to patients. Therefore, Nitinol stents are required to undergo greater deformations during manufacture without compromising the performance and durability of the medical device.Experimental characterisation of the material is required to demonstrate its mechanical behavioural characteristics. Since Nitinol wires are subjected to multi-mode loading conditions, investigation should incorporate all loading modes and thermomechanical conditions that a device encounters during its life cycle. The resulting data can then enable the derivation of the material’s constitutive properties which are necessary for computational analyses. Finite element analysis (FEA) has become an integral part of the design of medical devices and computational analyses reports are used nowadays as scientific evidence to support medical device submissions. The Nitinol constitutive model that is implemented in the finite element software Abaqus is considered the industry standard. However, its capabilities and limitations are not fully explored since there are no experimental data available for this purpose.In the present work, a methodology was developed to characterise medical grade Nitinol wires in tension, compression, bending and torsion. The mechanical behaviour of the material was examined under high-strain tensile deformation. The relevant constitutive parameters were identified from the experimental results and the Abaqus Nitinol model was assessed, including its superelastic-plastic modelling capabilities, by simulating the mechanical tests of all loading modes. The key findings from the present work are summarised below.High straining of the material during compaction results in decreased austenite stiffness, decreased load and unload plateaus and increased residual strain. These features are more pronounced when multiple compaction attempts take place. A recommendation is made, to limit the compaction strain to 10%, if possible. This is because if more than one compaction attempts take place at 10% strain, the effect on the unload plateau, which influences the radial strength of the stent, will be small. In addition, up to 10% compaction strain there is only a small, gradual increase of residual strain. The bending response of the material is load-rate sensitive. Therefore, compaction should take place slowly in order to avoid potential rate effects. Sterilization is not expected to have a negative impact on the stress levels experienced by Nitinol wires during this process, since temperature sensitivity was not observed within the post-transformation region.The Abaqus Nitinol model provided results that were in agreement with the experiments when modelling tension within the superelastic range, as only minor qualitative differences were identified between computational and experimental responses. However, the material model was incapable of forecasting the sensitivity of the unload plateau to the high strain loading. The present work shows that this limitation can be overcome by implementing Fortran subroutines that modify the transformation stresses during unloading as a function of the plastic strain reached during the simulation. Tension-compression asymmetry was also exhibited in the FEA results. The austenite stiffness and the start of the transformation during loading in compression agreed quantitatively with the experimental results, exhibiting negligible errors. However, the unloading transformation stresses in compression were underpredicted by up to 36.6% compared to the experimental data.The flexural stiffness of austenite was also underestimated in the computational bending responses by up to 28.8%, although the transformation during loading started at the same force levels for FEA and experimental results. Results show that the loading path of the bending response can be improved if the flexural modulus of austenite is used as input parameter. However, the unloading path of the bending response was not captured correctly since it took place at lower forces compared to the experimental curves. The computational response in torsion was also not in agreement with the experimental results, as the torsional stiffness was underestimated by 11.2% while the loading and unloading paths took place in lower load levels. The model however, was able to capture the qualitative features of the combined tension-torsion deformation.Stent-grafts are medical devices designed to treat abdominal aortic aneurysms (AAAs). These devices are usually composed of a Nitinol wireframe and a fabric graft. The design of next generation stent-grafts is directed towards a very low-profile when compacted. Such devices can treat narrow access vessels and tortuous anatomies while inducing less trauma to patients. Therefore, Nitinol stents are required to undergo greater deformations during manufacture without compromising the performance and durability of the medical device.Experimental characterisation of the material is required to demonstrate its mechanical behavioural characteristics. Since Nitinol wires are subjected to multi-mode loading conditions, investigation should incorporate all loading modes and thermomechanical conditions that a device encounters during its life cycle. The resulting data can then enable the derivation of the material’s constitutive properties which are necessary for computational analyses. Finite element analysis (FEA) has become an integral part of the design of medical devices and computational analyses reports are used nowadays as scientific evidence to support medical device submissions. The Nitinol constitutive model that is implemented in the finite element software Abaqus is considered the industry standard. However, its capabilities and limitations are not fully explored since there are no experimental data available for this purpose.In the present work, a methodology was developed to characterise medical grade Nitinol wires in tension, compression, bending and torsion. The mechanical behaviour of the material was examined under high-strain tensile deformation. The relevant constitutive parameters were identified from the experimental results and the Abaqus Nitinol model was assessed, including its superelastic-plastic modelling capabilities, by simulating the mechanical tests of all loading modes. The key findings from the present work are summarised below.High straining of the material during compaction results in decreased austenite stiffness, decreased load and unload plateaus and increased residual strain. These features are more pronounced when multiple compaction attempts take place. A recommendation is made, to limit the compaction strain to 10%, if possible. This is because if more than one compaction attempts take place at 10% strain, the effect on the unload plateau, which influences the radial strength of the stent, will be small. In addition, up to 10% compaction strain there is only a small, gradual increase of residual strain. The bending response of the material is load-rate sensitive. Therefore, compaction should take place slowly in order to avoid potential rate effects. Sterilization is not expected to have a negative impact on the stress levels experienced by Nitinol wires during this process, since temperature sensitivity was not observed within the post-transformation region.The Abaqus Nitinol model provided results that were in agreement with the experiments when modelling tension within the superelastic range, as only minor qualitative differences were identified between computational and experimental responses. However, the material model was incapable of forecasting the sensitivity of the unload plateau to the high strain loading. The present work shows that this limitation can be overcome by implementing Fortran subroutines that modify the transformation stresses during unloading as a function of the plastic strain reached during the simulation. Tension-compression asymmetry was also exhibited in the FEA results. The austenite stiffness and the start of the transformation during loading in compression agreed quantitatively with the experimental results, exhibiting negligible errors. However, the unloading transformation stresses in compression were underpredicted by up to 36.6% compared to the experimental data.The flexural stiffness of austenite was also underestimated in the computational bending responses by up to 28.8%, although the transformation during loading started at the same force levels for FEA and experimental results. Results show that the loading path of the bending response can be improved if the flexural modulus of austenite is used as input parameter. However, the unloading path of the bending response was not captured correctly since it took place at lower forces compared to the experimental curves. The computational response in torsion was also not in agreement with the experimental results, as the torsional stiffness was underestimated by 11.2% while the loading and unloading paths took place in lower load levels. The model however, was able to capture the qualitative features of the combined tension-torsion deformation
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
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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