1,721,148 research outputs found
Prediction and analysis of JET fusion performance based on reduced first principle transport models
Full text linkThe design of a Tokamak device is carried out initially with a 0D approach aiming at defining the plasma engineering parameters estimated with the help of empirical scaling laws, and the technological limits of the device components. The assessment of local parameters (1D) is then required to define the optimal plasma performance during the entire time evolution of the discharge. In this contest, the transport of energy and particles in fusion plasmas is one of the main actor in determining the evolution of a plasma scenario both in present experiments and in future reactors.
The Joint European Torus (JET) experiment has operated in deuterium (D) and tritium (T) main ion plasma composition in 1997 (DTE1) and in 2021 (DTE2). The most important differences between the two experimental campaigns are related to the plasma facing components, carbon (C) in DTE1 and Be/W in DTE2, the increased additional heating power, and the presence of improved diagnostics, especially at the plasma edge which is determinant in the global plasma performance. After DTE1 the high levels of T retention in the C-wall have been considered unacceptable for a reactor, leading to the substitution of the C-wall with a metallic wall in the design of the International Tokamak Experimental Reactor (ITER). DTE2 campaign at JET aimed at studying D-T plasmas in the closest conditions to ITER operations. Differently from DTE1, the recent campaign focused on the stationarity of the performance and on addressing ITER-relevant aspects such as α-particles physics, plasma wall interactions and plasma heating schemes. In preparation to D-T operations, a wide experimental and modelling activity has been performed at JET in order to optimise the plasma scenarios.
The focus of this thesis is the extrapolation in D-T main ion plasma composition of the JET baseline scenario. The latter is a high confinement mode (H-mode) plasma, characterized by the presence of Edge Localized Modes (ELMs), where the confinement relies on high plasma current. In ITER D-T operations, the baseline scenario is envisaged to achieve a gain factor, defined as the ratio between the fusion power and the input power, Q = Pfus/Pin ≈ 10. The objective of the thesis has been achieved through extensive integrated modelling, based on the reduced first principles transport models QuaLiKiz and TGLF employing different assumptions, and in a wide range of plasma operating conditions. QuaLiKiz and TGLF transport models have been validated in reference D plasmas, and their extrapolation capability with different plasma parameters has been tested by performing blind predictions. The results of the predictive modelling have been compared with the experimental data and analysed in order to address the sensitivity of the plasma scenario to the experimental boundary conditions. The QuaLiKiz transport model has also been validated against the experimental results produced at JET in DTE1.
Before the start of the DTE2 campaign, an estimate of the particle sources required to sustain a 50-50 D-T baseline plasma has been obtained. This result has provided inputs to the JET control team in the preparation phase of the baseline fuelling scheme. This contribution boosted JET D-T operations without spending experimental time, neutron and T budget.
The results of the predictive modelling performed in preparation to DTE2 are presented and discussed. The sensitivity of the predictions to plasma parameters
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such as current, toroidal magnetic field, pedestal confinement and impurity content are analysed together with the sensitivity to the available amount of auxiliary heating power.
The experimental results obtained in DTE2 by the baseline scenario are also presented and discussed. In the last part of this thesis, the implications of the modelling assumptions performed on D pulses will be compared with the assumptions done on D-T discharges with the experimental boundary conditions. The key parameters needed for reliable predictions of future experiments are discussed both in D and D-T main ion plasma composition. The estimate of particle sources obtained before the DTE2 campaign are adjusted to reproduce the experimental conditions, leading to an estimate of the different fuelling channels and an evaluation of the wall sources.
The thesis is organised as follows:
• In Chapter 1 we introduce fusion as a potential energy source.
• In Chapter 2 we describe the Tokamak configuration and the JET experi- mental device, and we present a first comparison between the different D-T experimental campaign, and between the different scenarios prepared for DTE2.
• In Chapter 3 we introduce the issue of energy and particle transport in Tokamaks, we present the theoretical background and the state of the art of transport analysis. The models used in this work are presented together with the different assumptions implemented in JINTRAC.
• In Chapter 4 we present and discuss the validation of the reduced first principle transport models performed on D pulses. The extrapolations in D-T plasma mixture are presented with their sensitivity to the operating conditions.
• In Chapter 5 we present and discuss the baseline results obtained in DTE2. The predictive simulations are improved by adopting the actual boundary conditions of the D-T experiments, and we discuss the impact of the different assumptions on the modelling of D plasmas extrapolated to D-T plasma mixture. We show the limits of predictive simulations in integrated modelling, and we use the predictive simulations to obtain an estimate of the different fuelling sources in the D-T experiments
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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