1,720,998 research outputs found
Optimising lithium-ion cell design for plug-in hybrid and battery electric vehicles
Full text linkIncreased driving range and enhanced fast charging capabilities are two immediate goals of transport electrification. However, these are of competing nature, leading to increased energy and power demand respectively from the on-board battery pack. By fine-tuning the number of layers versus active electrode material of a lithium ion pouch cell, tailored designs targeting either of these goals can be obtained. Achieving this trade-off through iterative empirical testing of layer choices is expensive and often produces sub-optimal designs. This paper presents a model-based methodology for determining the optimal number of layers, maximising usable energy whilst satisfying specific acceleration and fast charging targets. The proposed methodology accounts for the critical need to avoid lithium plating during fast charging and searches for the optimal layer configuration considering a range of thermal conditions. A numerical implementation of a cell model using a hybrid finite volume-spectral scheme is presented, wherein the model equations are suitably reformulated to directly accept power inputs, facilitating rapid and accurate searching of the layer design space. Electrode materials exhibiting high solid phase diffusion rates are highlighted as being equally as important for extended range as the development of new materials with higher inherent capacity. The proposed methodology is demonstrated for the common module design of a battery pack in a plug-in hybrid vehicle, thereby illustrating how the cost of derivative vehicle models can be reduced. To facilitate model based layer optimisation, the open-source toolbox, BOLD (Battery Optimal Layer Design) is provided
Model-Supported Lithium-Ion Battery Diagnostics for Knowledge-Based Cell Optimization
Full text linkLithium-Ionen-Batterien sind von zentraler Bedeutung für ein breites Spektrum von Anwendungen, von Smartphones über Elektrofahrzeuge bis hin zu stationären Energiespeicherlösungen. Mit der schnell wachsenden Nachfrage nach diesen Batterien wird die effiziente Verarbeitung von teuren Rohstoffen in langlebige Zellen mit überlegenen Leistungsmerkmalen immer wichtiger.
In dieser Arbeit wird physikochemische Modellierung auf zwei grundlegend leistungs- und kostenbestimmende Phasen in der Herstellung von Lithium-Ionen-Batterien angewandt: Zelldesign und Zellproduktion. Zunächst werden anhand einer modellbasierten Designstudie die Herausforderungen optimalen anwendungsspezifischen Zelldesigns aufgezeigt. Dabei wird die Bedeutung der seltener untersuchten Ladeleistung in den Fokus gestellt, da diese für eine ganzheitliche Optimierung eines Zelldesigns entscheidend ist. Anschließend wird der Formierungsprozess, einer der teuersten Prozessschritte in der Batterieproduktion, analysiert. Dieser umfasst das erste Laden und Zyklisieren einer Lithium-Ionen-Batterie, welches eine kontrollierte Bildung der Solid Electrolyte Interphase (SEI) auf dem Anodenaktivmaterial gewährleistet. Trotz intensiver Forschung sind die initiale Bildung der SEI und ihr Effekt auf die Zelldegradation und -leistungsfähigkeit noch nicht vollständig verstanden. Aus diesem Grund wird ein Zell- und SEI-Modell entwickelt, das eine zerstörungsfreie Charakterisierung dieses komplexen Oberflächenfilms für verschiedene Formierungsprozeduren ermöglicht. Dabei stellt die gemeinsame Parametrierung mit Entladungsmessungen und elektrochemischen Impedanzspektren sicher, dass die ermittelten Parameter zuverlässige Einblicke in das Zellverhalten ermöglichen. Mit diesem Ansatz kann schließlich der Zellzustand unmittelbar nach der Formierung ermittelt und seine Veränderung im Laufe der Alterung untersucht werden.
Zusammenfassend zeigt diese Arbeit die Bedeutung eines ganzheitlichen Ansatzes für Zelldesign und -diagnostik. Ohne ein gutes Verständnis der Entlade- und Ladeeigenschaften einer Zelle ist eine eindeutige Identifizierung überlegener Zelldesigns für spezifische Anwendungen nicht möglich. Die gemeinsame Analyse experimenteller C-Ratentests und Impedanzdaten ist entscheidend für eine zuverlässige Differenzierung zwischen Zelleigenschaften auf Partikel- und Elektrodenebene. Mit diesem Ansatz konnten die Leistungsunterschiede nach verschiedenen Formierungsprozeduren detailliert untersucht werden. Die Ergebnisse deuten darauf hin, dass sich unterschiedliche Oberflächenfilme in der Anode und der Kathode ausbilden, die im Zusammenhang mit signifikanten mikrostrukturellen Änderungen in den Elektroden stehen
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
Advanced lithium-ion battery modelling for automotive applications
Full text linkA novel electrical circuit analogy is proposed to model electrochemical systems under realistic automotive operation conditions. The model is developed for a lithium ion battery and is based on a pseudo 2D electrochemical model. It calculates the evolution of species concentration distribution and diffusion for a given current load, as a result of electrochemical reactions. The application example is an automotive system, in which results are obtained at a rate faster than real-time and well within the accuracy requirements of a typical Battery Management System (BMS). This is the first Equivalent Circuit Network (ECN)-type model that tracks directly the evolution of species inside the cell, and includes implementation of complex electrochemical phenomena usually omitted such as double layer capacitance and overpotentials due to mass transport limitations in the electrode host material. Three networks, one for each of the three species present, electrons, Li ions, and intercalated Li atoms, are connected through a triple species element, which governs the conversion between species at the resulting activation, diffusion and passivating layer overpotentials. The link between the three networks is an important feature of this model, coupling information of each of the three joining circuit networks at this node. The model is fully thermally coupled and can account for capacity fade via a decrease in the amount of active species and for power fade via an increase in a resistive solid electrolyte inter-phase layer at both electrodes. The model’s capability to simulate cell behaviour under dynamic events from 0% to 100% State-of-Charge (SoC) conditions is demonstrated with various test procedures. Examples for model output are given for various standard battery testing load cycles as well as realistic automotive drive cycle loads. Although cast in the framework familiar to application engineers, the model is essentially an electrochemical battery model: all variables have a direct physical interpretation and there is direct access to all states of the cell via the model variables (species concentrations, potentials) for the later purpose of control systems design. Further model extensions are easily implemented atop the current framework. The presented methodology is further applicable for electrochemical system performance evaluation and prediction of battery performance in any kind of portable battery-powered electronic device and application with low computational power availability and online solution requirements.Open Acces
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
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