1,720,970 research outputs found
Investigating the Interaction between Degradation and Thermal Behaviour in Lithium-Ion Batteries
Get PDFThe overall aim of this thesis is to generate knowledge on the interplay of battery degradation and thermal behaviour. We focused on the temperature dependency of degradation on the one hand and on the effect of degradation on heat generation, thermal transport and temperature distribution inside Lithium-ion Batteries (LiB) on the other.
In Article I., we reviewed studies investigating the capacity loss and resistance increase of commercial LiB due to both cycling and calendric degradation, covering different anode and cathode active materials, geometries and nominal capacities. The sensitivity of degradation behaviour towards operation conditions was examined. The potential thermal effect of C-rate-induced degradation was investigated in the light of a sufficiently simplified thermal battery model. We pointed out the need for more comparable data and experimental studies for deeper analysis - including an estimate of the actual cell temperature rather than the ambient temperature, as we found the difference between ambient temperature and actual cell temperature can vary significantly. We also pointed out the challenge both when comparing different studies and when transferring results from laboratory experiments to real applications, as cooling conditions differ. Therefore, measuring and reporting the actual battery (surface) temperature was found to be crucial to allow for a proper interpretation of results, especially when evaluating charging and discharging at high rates.
Based on the knowledge about the importance of the actual battery temperature for degradation from Article I., we conducted a degradation study focusing on the changes in battery temperature as part of Article II.. This was done by conducting a degradation study for a wide spread of thermal management strategies and charging and discharging rates, with a special focus on measuring and reporting the battery temperature. We assessed the effect of degradation on heat generation and temperature distribution in LiB. We found that for cells with LCO cathodes, entropic heating plays a major role in the overall heat generation - causing large variations in the heat generation rate and therefore battery temperature over the State-of-Charge (SoC). The maximum battery temperature was found to increase when the cell degrades as irreversible heat generation increases. It appeared that a maximum in heat generation during a full discharge was reached at a SoH between 75 % and 85 % for cells cycled with C-rates greater than 1. Temperature variation over the thickness of the cell appeared to be more substantial than in-plane and it was found that the variation was increasing significantly once the cell degraded. Degraded cells also showed significant thickness increases, where higher temperatures resulted in larger thickness increases with clear signs of gassing.
The changes in thermal transport due to degradation were examined in Article III., specifically the effect of thermal management and clamping. The thermal conductivities of electrodes extracted from cells both at Beginning-of-Life (BoL) and End-of-Life (EoL) were measured, as well as the overall cell cooling efficiency. The effective full-cell thermal conductivities were calculated, and the changes due to degradation were compared to measured changes in overall cell cooling efficiency. A reduction of thermal conductivity of up to 65 % compared to BoL was found. The reduction appeared to be the most extreme for dry graphite anodes. It was found that clamping cells during cycling has the potential to mitigate the reduction. The thermal conductivity of graphite anodes cycled at cold temperatures appeared to reduce significantly less than when the cell was cycled at moderate or high temperatures. The overall cell cooling efficiency was reduced by 50 % from BoL to a SoH of 70 to 75 %. It was found that the main reduction in the thermal conductivity of the full cell is due to changes in the anode and a reduction in the electrolyte solvent.
Finally, the role of the ambient temperature on degradation was further examined in Article IV., utilizing incremental capacity analysis (ICA). We showed how incremental capacity (IC) simulations in combination with analyzing Features-of-Interest (FoI) within the IC curves enables the observation of differences that are difficult to identify from the IC curves alone. The importance of differentiating between degradation and capacity loss became very important: Despite the rate of capacity loss appearing to be very similar for clamped cells cycled at 15 ◦C and 25 ◦C, as well as 5 ◦C and 35 ◦C, the degradation modes and mechanisms appeared to be very different. Using ICA, the degradation of cells cycled at 25 ◦C and higher, as well as 15 ◦C and lower, each show similar degradation behaviour. In general, Loss of Lithium Inventory (LLI) appeared to be the main degradation mechanism, especially for cells cycled at higher temperatures, while the cells cycled at lower temperatures indicated a large degree of inhomogeneous degradation within the single cells. With a suitable Features-of-Interest (FoI) versus State-of-Health (SoH) map, the FoI appeared to enable a simple approach to identify if cells have been pressurized during the use phase and narrow down the temperature range a cell has been cycled at. A possible option for applying this process is identifying cells with unknown cycling histories suitable for second-life applications
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
- …
