1,721,126 research outputs found
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
Physikalisch motivierte Materialklassifizierung und Prozessoptimierung für plastifizierende additive Fertigungsverfahren
No full textProzessnahe Schwindungsanalyse mehrkomponentiger duroplastischer Kunststoffe für die Anwendung in Flüssigimprägnierverfahren
No full textThermoset (DP) resin systems are used as matrix systems in fibre-reinforced plastics (FRP). They are cured in industrial manufacturing processes mostly under pressure and temperature influence. The curing reaction is characterised through a developing three-dimensional cross linked network-structure. During the processing, various processing aids (e.g. internal release agents) are used. In addition to the processing aids, the resin systems are subject to conditioning due to their storage in barrels or day tanks, so that environmental factors can also influence the processing. Knowledge of the processing behaviour with different process parameters (manufacturing parameters: Curing temperature and pressure; material parameters: Dosage fluctuations, gas loading, release agents, moisture) in the form of phenomenological models or material models is an important part of process design, material development and the prediction of component properties. The three-dimensional crosslinking changes the density of the DP resin systems. A distinction can be made between chemical shrinkage resulting from the formation of covalent bonds and thermal shrinkage when the material temperature changes, e.g. during cooling from processing to service temperature. Component properties and process control are equally influenced by shrinkage. The analysis of shrinkage under process conditions of industrial liquid impregnation processes (increased curing pressure, isothermal curing temperature) with modern highly reactive resin systems is possible for the first time with the Real Process Condition Shrinkage Analyser (RPCSA) developed at the Institute of Plastics Processing (IKV). Two epoxy resin systems (EP resin systems) and a polyurethane resin system (PU resin systems) were investigated for the identification and qualitative description of shrinkage-influencing process parameters. All three resin systems are used in industrial applicationsAn influence of curing temperature on shrinkage was found in all resin systems. However, an influence of the curing pressure was only relevant for the EP resin systems. The effects of further material parameters were exclusively determined on a highly reactive EP resin system. The results of the shrinkage analysis also suggest a change in the heterogeneous network morphology with changed process parameters for EP resins
Plasma-coated membranes for gas separation
No full textThe increase in global energy demand for chemical reactions and subsequent downstreaming processes boosts greenhouse gas emissions and accelerates climate change. Applying polymeric gas separation membranes instead of thermally driven processes offers great potential in enhancing the processes’ energy efficiency. Since commercial membranes still lack the necessary separation performance for many applications, researchers have developed many new membrane materials over the past decades. Unfortunately, the synthesis routes for those materials are often complex, challenging to scale up, and the polymers tend to exhibit strong non-ideal effects. As a result, none of those new materials made the step into industrial application. Unlike most published membrane materials, this work builds upon an already-established technology. So-called plasma-enhanced chemical vapor deposition (PECVD) is used to deposit barrier coatings on polymer films. In this process, monomers and auxiliary gases are injected into a low-pressure vacuum chamber; a plasma is ignited, thereby triggering a chemical reaction. This results in the deposition of an organosilica polymer on a substrate. This thesis aims to utilize PECVD to produce organosilica films with tailored chemical and permeation properties. The deposited films shall be used as highly selective membranes for gas separation and physical aging mitigation coatings. Nanometer-thin organosilica films were deposited on a PDMS composite membrane or polymers with intrinsic microporosity (PIMs). The thesis investigated the influence of the plasma parameters on the chemical structure and membrane performance of the organosilica layer. The membranes prepared with low plasma energy input showed the lowest oxygen and highest carbon concentrations. Moreover, they exhibited superior size sieving behavior and high permeances. With the gained knowledge, highly selective gas separation membranes were fabricated. These were then tested in various pure and mixed gas environments. Although the deposited organosilica membranes showed signs of voids in their structure, they had excellent helium separation properties. In addition, the influence of organosilica layers on the physical aging behavior of PIMs was investigated. Here, highly oxidized films showed excellent protection against rapid aging for films as thin as 10 nm. They reduced the physical aging velocity by more than two orders of magnitude. Thus, this thesis shows the capability of PECVD to fabricate highly size-selective gas separation membranes and effective physical aging mitigation layers. Furthermore, since the PECVD process is already established in the industry as continuous roll-to-roll process, the findings open a promising route to fabricating nanometer-thin membranes by a tunable plasma-assisted process and utilizing them in currently challenging separation tasks
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
Analyse der Porenstrukturen in nanostrukturierten Funktionsschichten auf Kunststoffen und Modellierung des porengesteuerten Stofftransports
No full textAppropriate 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
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