1,720,986 research outputs found
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
Modulare Keramik-Komposite mit periodischer Mikrostruktur
Get PDFThis work describes the development and characterization of novel modular, periodic materials based on ceramic building-blocks. The composite formation included three steps:
1. production of uniform ceramic building-blocks in large quantities by means of a new forming technology
2. periodic assembly of the building-blocks in different 2D and 3D lattice symmetries by vibration assisted self-assembling and spacing meshes
3. composite formation by infiltration of a connecting polymer interphase
Building-blocks of different shapes were formed by molding mask technique of a paraffin-based alumina feedstock (> 10^3 per batch). They were assembled to closest packings in 2D-layers by means of vibration assisted self-assembling, which led to packing densities over 90 %. Furthermore, assemblies with controlled inter-building-block distances were produced by placing into spacing meshes.
These 2D-assemblies were connected via infiltration with an epoxy resin to form the modular material. Fitting of data from digital image analysis of cross sections by a developed algorithm revealed the high symmetry within the 2D monolayers. Subsequently those periodic monolayers were stacked to 3D arrangements with an equal lattice symmetry of quasi-crystalline structure.
Local stress distribution of the two-phase material could be visualized and measured by means of stress-optical analysis. Interaction of intrinsic stresses and building-block arrangement showed significant effects on single building-block behavior within the material as well as mechanical performance of the whole composite during fracture. Pull-out and compact tension tests were applied to analyze toughening mechanisms like crack deflection and crack bridging dominated by the lattice periodicity.
It could be shown that failure was pull-out dominated and material toughness was governed by lattice constants and building-block shape. In addition, optically determined stress distributions were consistent with finite element analysis.
Feasibility of more complex building-block shapes was demonstrated and new process technologies were described that enable production of modular composites consisting of other material combinations.In dieser Arbeit wurden Herstellung, Aufbau und mikromechanisches Verhalten neuartiger, modularer, periodischer Materialien untersucht, die auf keramischen Building- Blocks basierten. Die Herstellung der modularen Materialien erfolgte in drei Schritten:
1. Fertigung gleichförmiger, keramischer Building-Blocks in großer Stückzahl mit Hilfe eines neu entwickelten Formgebungsverfahrens
2. periodische Anordnung der Building-Blocks in unterschiedlichen 2D und 3D Gittersymmetrien durch vibrationsgestützte Selbstanordnung und Abstandsgitter
3. Bildung des Verbundwerkstoffes durch Einbringen einer konnektierenden Polymerphase
Mittels Maskenverfahren konnten die Building-Blocks in verschiedenen Formen aus Paraffin-basierter Al2O3-Abformmasse in großer Stückzahl hergestellt werden (> 10^3 pro Charge). Eine schnelle 2D-Ausrichtung der Building-Blocks zu dichtestmöglichen Packungen in der Ebene wurde durch vibrationsgestützte, gravitative Selbstanordnung erreicht. Sie führte zu defektfreien, hohen Packungsdichten über 90 %. Zusätzlich wurden Anordnungen mit definierten Abständen über das Setzen der Building-Blocks in Abstandsgitter erzeugt.
Diese 2D-Anordnungen wurden durch Epoxidharzinfiltration zum modularen Komposit verbunden, dessen Gitterparameter mit Hilfe einer neu entwickelten Methode zur Analyse der digitalen Schnittbildinformationen bestimmt wurden und eine hohe Symmetrie in der Ebene zeigten. Die periodischen Monolagen konnten wiederum zu 3D-Gittern gestapelt werden, die ebenfalls eine hohe Periodizität der Building- Blocks im Raum zeigten. Das modulare Material war daher von quasi-kristalliner Gitterstruktur.
Neben der Geometrie wurde die lokale Spannungsverteilung des zweiphasigen Materials mit Hilfe der Spannungsoptik visualisiert und quantifiziert. Das Zusammenspiel von intrinsischen Spannungen und innerer Geometrie zeigte einen signifikanten Einfluss auf das mechanische Verhalten der einzelnen Building-Blocks im Verbund sowie des gesamten modularen Materials bei Versagen. Um diese Zusammenhänge klären zu können, wurden u. a. die bekannten Prüfverfahren des Push-Out-Tests und des CT-Tests an die Building-Block-Geometrie und Werkstoffabmessungen angepasst und durchgeführt. Aus den mechanischen und geometrischen Kennwerten konnten die Verstärkungsmechanismen wie Rissablenkung und Rissüberbrückung mit den Gitterparametern korreliert werden.
Es zeigte sich, dass das Versagen des modularen Komposits Pull-Out-dominiert war und die Zähigkeit von den Gitterkonstanten und der Building-Block-Form bestimmt wurde. Zudem stimmten die optisch aufgenommenen Spannungsverteilungen sehr gut mit den FEM-Simulationen überein, die mit den ermittelten Materialkennwerten errechnet wurden.
Im Hinblick auf die Weiterentwicklung der modularen Materialien wurden die Machbarkeit komplexerer Building-Block-Geometrien nachgewiesen und neue Prozesstechniken zur Herstellung modularer Komposite aus anderen Materialkombinationen und mit weiteren Gitterstrukturen exemplarisch demonstriert
Rapid Prototyping von Keramik/Metall-Verbundwerkstoffen
Get PDFBinary and ternary MAX-based composites were fabricated using 3DP multistep processing technique. While 3DP provides an opportunity to produce porous ceramic preforms with a high degree of freedom in geometry and shape, a subsequent liquid metal infiltration into these preforms offers a way to fabricate dense materials through exothermic reaction. Upon sintering prior to melt infiltration a porous microstructure with interconnected porosity in the preform can be achieved. Furthermore, a carbothermal reduction process of Nb2O5 to NbO2 was found to provide adequate condition for pressureless infiltration of Al melt. Nanolaminate structure of MAX phase Nb2AlC grains give rise for extended plasticity resulting in excellent damage tolerance and thermal shock resistance. The high capacity of Nb2AlC for absorbing and distributing damage during Vickers indentation has been demonstrated. Under compression-shear deformation Nb2AlC exhibits a quasi-plasticity deformation behavior, which can be explained by the multiple basal plane slip between microlamellae, intergrain sliding, lamellae, or grain push-out. A kinking-based model in the literature can explain the quasi-plasticity and damage tolerance triggered by the nanolaminate structure of Nb2AlC. Nano-laminated Ti3AlC2 offers a significant toughening performance in Ti3AlC2-Al2O3-TiAl3 composites which showed non-catastrophic failure behavior. Similar deformation and damage mechanisms can be extensively observed in Ti3SiC2 samples subjected to compression and indentation loads (results in the literature). Ab initio calculations of cleavage energy and electron density in Ti3AlC2 crystal confirmed the experiment-based deformation and damage mechanism of Ti3AlC2 in the composites.Binäre und ternäre MAX-Phasen-basierte Komposite wurden über dreidimensionalen Drucken (3D-Drucken) hergestellt. 3D-Drucken bietet die Möglichkeit, poröse keramische Vorkörper mit einem hohen Freiheitsgrad in der Geometrie herzustellen. Durch anschließende reaktive Schmelzinfiltration wurden dichte Materialien erzeugt. Durch Sintern der 3D-gedruckten Grünlinge konnte ein poröses Gefüge mit einem durchgängigen Porennetzwerk erreicht werden, dass günstige Bedienung für die Infiltration mit metallischen Schmelzen bietet. Die Nanolaminatstruktur der MAX-Phase Nb2AlC bietet die Voraussetzung für quasi-plastische Verformung, die zu ausgezeichneter Schadenstoleranz und Temperaturwechselbeständigkeit führt. Die Schadenstoleranz wurde über lokale Verformungsexperimente (Vickerseindrückmethode) nachgewiesen. Bei einer Druckscherverformung weist Nb2AlC ein plastisches Verformungsverhalten auf, was durch die Basalgleitung zwischen Mikrolamellen dominiert wird, die zu ausgeprägten Lamellen-Knick-Vorgängen (Kinking) (a kinking-based model in the literature) führt. Ti3AlC2-Nanolaminat basierte Verbundwerkstoffe bieten eine Bruchzähigkeitssteigerung in den Ti3AlC2-Al2O3-TiAl3 Kompositen, die kein katastrophales Bruchversagen aufweisen. Ähnliche Verformungs- und Schadensmechanismen wurden in Ti3SiC2 Proben unter Druckbelastung und nach Vickerseindrücken beobachtet (Ergebnisse in der Literatur). Ab-initio-Rechnungen der Spaltungsenergie und Elektronendichteverteilung im Ti3AlC2 Kristall bestätigen die experimentellen Ergebnisse der Verformungs- und Schadensmechanismen-Hypothese von Ti3AlC2
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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