1,720,981 research outputs found
Geautomatiseerde in silico ontwikkeling van materialen voor energie- en plasmatoepassingen
No full textAbstract: Materials and their properties play a vital role in most applications we use on a daily basis. Many of the revolutions in industry are instigated by the discovery, by accident or design, of a new material that makes an application commercially viable. Historically, the study of materials has largely relied on an intuition-driven trial and error approach. However, considering the enormous design space of possible materials, as well as the fact that many of the straightforward materials have already been discovered, this process has become too expensive and time-consuming. Since the middle of the 20th century, a new paradigm in materials science has been developing, where computer simulations are used to calculate the properties of materials from rst principles. This new approach has steadily become more and more successful, pushed forward by the ever-increasing performance of modern computers and rapid progress in theoretical methods. During the past few decades, computational materials science has started evolving more and more into a predictive tool instead of simply oering theoretical insight into the physical processes of materials of interest. In combination with increasingly available tools for automating the required calculations, this has led to the concept of in silico materials design, where large numbers of compounds are investigated using computer simulations in order to gauge their potential for a specic application. Among the most successful theoretical frameworks for computational materials science is density functional theory, which can determine the electronic structure of many compounds with ever increasing accuracy using a reasonable amount of computational resources. However, the connection between the electronic structure of a material and the property of interest for a specic application is rarely trivial. The main goal of this thesis is to provide or improve this connection, by analyzing existing metrics for aws or anomalies, and developing new descriptors of material properties as well as the tools for calculating them using automated work ows. These methods are then applied to a set of topics, including solar cells, Li-ion batteries and ion-induced secondary electron emission. The structure of the thesis is as follows: Chapter 1 brie y introduces the concept of in silico materials design, and provides a guide to the reader of this thesis for navigating and consulting the available resources. Chapter 2 explains the density functional theory framework, as well as some practical computational techniques for calculating the electronic structure using this framework. Chapter 3 outlines the work ows used for the automation of the required density functional theory calculations of each descriptor or metric. Chapter 4 discusses the Shockley-Queisser limit and spectroscopic limited maximum eciency, two metrics used to determine the potential of a material as the absorber layer of a single-junction solar cell. Next, it makes a comparison of the CuAu-like and chalcopyrite phase in the context of thin-lm photovoltaics. Chapter 5 presents an investigation of the stability of the oxygen framework of Li-rich Li2MnO3 and Li2IrO3 battery cathodes, as well as a limited substitution of Mn as a potential recipe for improving the structural stability of these materials. Moreover, it discusses the energy landscapes of LiCB11H12 and NaCB11H12 polyborane salts in the context of solid electrolytes. Chapter 6 discloses a new model for calculating the secondary electron emission yield from ions neutralized at a semiconductor and metal surface, and applies this descriptor to a set of elemental surfaces spanning the periodic table in a high-throughput approach
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
Quantitative modeling of secondary electron emission from slow-ion bombardment on semiconductors
No full textAbstract: When slow ions incident on a surface are neutralized, the excess potential energy is passed on to an electron inside the surface, leading to emission of secondary electrons. The microscopic description of this process, as well as the calculation of the secondary electron yield, is a challenging problem due to its complexity as well as its sensitivity to surface properties. One of the first quantitative descriptions was articulated in the 1950s by Hagstrum, who based his calculation on a parametrization of the density of states of the material. In this paper, we present a model for calculating the secondary electron yield, derived from Hagstrum's initial approach. We use first-principles density functional theory calculations to acquire the necessary input and introduce the concept of electron cascades to Hagstrum's model in order to improve the calculated spectra, as well as remove its reliance on fitting parameters. We apply our model to He+ and Ne+ ions incident on Ge(111) and Si(111) and obtain yield spectra that match closely to the experimental results of Hagstrum
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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