1,721,050 research outputs found
Chalcogenide thin film materials for next generation data storage
No full textData can be stored in the form of amorphous and crystalline marks within a chalcogenide thin film. Commonly Ge2Sb2Te5 is used as the active data storage material to record these two different phases. Changes in phase are induced by controlled heating and cooling with laser radiation or an electric current. The research reported here shows, for the first time, that phase changes are possible in two new materials: BiSbTe and GaLaS. A further, known, phase change system, GeSbTe, has been used to test combinatorial deposition techniques and high throughput characterisation methodologies. An optical system, the static tester, was developed to test the time necessary for phase transitions. The system, capable of automated operation, can sequentially characterise the phase change kinetics of composition spread, thin film, samples. The GeSbTe system was investigated, as a function of composition, using combinatorial deposition methods. This showed that combinatorial methods can be applied to phase change materials and allowed new material characterisation over the whole ternary system. Using combinatorial methods, the electrical sheet resistance of the amorphous material is shown to be correlated to the tellurium concentration and is thought to be due to correlated increases in lone-pair defect charge trapping centres. The material’s resistivity can change by more than an order of magnitude by increasing the Te content from 20 at.% to 50 at.%. Conversely, in the amorphous phase, the refractive index was shown to decrease with increasing Te proportion and this has been related to a decrease in the material’s polarizability. The Sb:Te binary system has been doped with Bi using two different methods; sputter deposition from a composite target and using combinatorial, thermal evaporation deposition of elemental targets. New results have shown that Sb8Te2 can be doped with up to 13at.% Bi and still exist in a stable amorphous state. A novel chalcogenide material consisting of gallium, lanthanum and sulphur was shown, for the first time, to phase change. The crystallisation time of Ga:La:S:Cu material was found to be 150ns and dependent on the Cu proportion. Increasing the Cu by 30 at.% increased the crystallisation time to 350ns. The electrical resistivity of these materials was approximately 4Ωm. This allows efficient Joule heating and electrical switching was demonstrated. A finite element analysis has shown that this material can be amorphised with a current of just 0.4µA in comparison to 2.5mA required for a similar volume of Ge2Sb2Te5. Therefore Ga:La:S:Cu shows potential as a future electrical phase change data storage material
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
Material optimisation for optical data storage
No full textHigh throughput synthesis and screening methodologies of optical data storage materials have allowed an in depth study of more than 4000 compositions. We report on the optical and electrical compositional dependence of these materials
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
The lightwave roadshow
No full textMany primary school children perceive science as boring and inaccessible. These misconceptions mould the paths these children will choose for their future education and careers, mirrored in reducing numbers of applicants for physics courses in higher education. We describe our experiences running a photonics outreach project, The Lightwave Roadshow, an interactive collection of photonics demonstrations and experiments aimed at children aged 5 to 11. We discuss how this programme can be instrumental in improving the profile of scientific education and careers for children of a young age
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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