1,720,954 research outputs found
Investigation of trim influence on resistance, seakeeping and propulsive performance
Get PDFThere has been a lot of interest in recent years in trim and ballast optimisation in which the ballast of a vessel is varied to reduce fuel consumption and greenhouse gas emissions. Trim optimisation is one of the easiest and cheapest methods among many fuel-saving measures recommended by IMO as it does not require any hull shape modification or engine upgrade. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life, the effect of trim on ships resistance and powering will be significant. However, limited research has been performed to investigate trim influence on ship performance. In many cases, the work has concentrated on minimisation of resistance; often focussing on calm-water resistance in model scale. The impact of trim on added resistance and propulsive performance of ships is less well understood.In this context, the main aim of this PhD study is to gain an improved understanding of the impact of trim on the resistance, seakeeping and propulsive performance of vessels by using Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) methods. This study covers model tests in towing tank, model scale and full scale CFD analyses for various operating points in calm water and waves.This study consists of three main parts. In the first part, trim influence on the calm water resistance of the KRISO Container Ship (KCS) was investigated. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions and also for ballast draft with the hull both fixed and free to sink and trim. Trim influence on individual resistance components was discussed. Full-scale numerical simulations are also carried out and differences between model scale and full-scale findings are discussed to investigate scale effects on optimum trim.In the second part of this study, the effects of trim angles on added resistance and motion responses of KCS were evaluated experimentally and numerically in six different trim angles. Effects of trim angles on added resistance were analysed and results concerning the performance of the vessel at different trim angles were plotted. Experimental and numerical results for the heave and pitch motions and the added resistance were compared. Furthermore, the range of trim and wave conditions were identified for the application of the rapid linear potential flow method.The study is then extended to include a model of the propeller to investigate the trim influence on the propulsive performance of the KCS. Self-propulsion simulations were performed using two different methods, namely, sliding mesh with 3-D propeller geometry and body force method based actuator disk approach. Effects of trim angles on propulsive characteristics were analysed and results concerning the performance of the vessel at different trim angles were plotted. The differences in optimum trim based on pure resistance simulations and self-propulsion simulations were investigated. As trim optimisation studies require the analysis of large number of different operating conditions, the applicability and accuracy of a quicker simplified actuator disk approach was tested.This author believes that methods and findings presented in this study contribute towards better understanding of the trim influence on resistance and powering performance of ships. Additionally, these findings may be used to further develop accurate and efficient trim optimisation tools for minimizing fuel consumption and emissions accordingly.There has been a lot of interest in recent years in trim and ballast optimisation in which the ballast of a vessel is varied to reduce fuel consumption and greenhouse gas emissions. Trim optimisation is one of the easiest and cheapest methods among many fuel-saving measures recommended by IMO as it does not require any hull shape modification or engine upgrade. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life, the effect of trim on ships resistance and powering will be significant. However, limited research has been performed to investigate trim influence on ship performance. In many cases, the work has concentrated on minimisation of resistance; often focussing on calm-water resistance in model scale. The impact of trim on added resistance and propulsive performance of ships is less well understood.In this context, the main aim of this PhD study is to gain an improved understanding of the impact of trim on the resistance, seakeeping and propulsive performance of vessels by using Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) methods. This study covers model tests in towing tank, model scale and full scale CFD analyses for various operating points in calm water and waves.This study consists of three main parts. In the first part, trim influence on the calm water resistance of the KRISO Container Ship (KCS) was investigated. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions and also for ballast draft with the hull both fixed and free to sink and trim. Trim influence on individual resistance components was discussed. Full-scale numerical simulations are also carried out and differences between model scale and full-scale findings are discussed to investigate scale effects on optimum trim.In the second part of this study, the effects of trim angles on added resistance and motion responses of KCS were evaluated experimentally and numerically in six different trim angles. Effects of trim angles on added resistance were analysed and results concerning the performance of the vessel at different trim angles were plotted. Experimental and numerical results for the heave and pitch motions and the added resistance were compared. Furthermore, the range of trim and wave conditions were identified for the application of the rapid linear potential flow method.The study is then extended to include a model of the propeller to investigate the trim influence on the propulsive performance of the KCS. Self-propulsion simulations were performed using two different methods, namely, sliding mesh with 3-D propeller geometry and body force method based actuator disk approach. Effects of trim angles on propulsive characteristics were analysed and results concerning the performance of the vessel at different trim angles were plotted. The differences in optimum trim based on pure resistance simulations and self-propulsion simulations were investigated. As trim optimisation studies require the analysis of large number of different operating conditions, the applicability and accuracy of a quicker simplified actuator disk approach was tested.This author believes that methods and findings presented in this study contribute towards better understanding of the trim influence on resistance and powering performance of ships. Additionally, these findings may be used to further develop accurate and efficient trim optimisation tools for minimizing fuel consumption and emissions accordingly
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
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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