1,721,213 research outputs found
Two dimensional flow simulation using discrete vortex methods on MIMD processor arrays
No full textThe discrete vortex method is a Lagrangian technique for solving the two-dimensional Navier- Stokes equations for an incompressible homogeneous Newtonian fluid. The construction of a robust numerical solver, based on the discrete vortex method, is discussed in detail. The viscous effects are modelled using both the random walk and diffusion velocity techniques. The computational cost is reduced by using a zonal decomposition algorithm for the velocity summation and by formulating an implementation suitable for execution on MIMD' parallel architecture computers. The code is validated using the problem of impulsively started flow past a circular cylinder at Reynolds numbers ranging from 300 to 31,700. Short/medium time solutions for both the rotating and non-rotating cases are used to confirm the accuracy of the method by comparison with experimental and numerical results from the literature. Long time solutions for the non- rotating case reveal non-determinism at high Reynolds numbers: the flows can exhibit a multiplicity of vortex shedding patterns. The low-speed stall process on NACA four-digit wing sections is visualised. A detailed comparison of the flow past a symmetric aerofoil with the flow past a cambered aerofoil shows that the camber delays the onset of the stall. Multiple Instruction Multiple Data</p
Phenomenological aspects of supersymmetric family symmetries
No full textWe study the phenomenological consequences of models with family symmetries which are broken close to the GUT scale. First, we consider a string-inspired model which becomes a supersymmetric Pati-Salam model with an abelian family symmetry at energy scales between the string scale and the GUT scale. We use the predicted rates of BR(µ → eγ) to gauge the relative importance of a number of contributions to flavour violation, including from auxiliary fields associated with the spontaneous breaking of the family symmetry close to the GUT scale. Secondly, we consider the effect of an operator expansion in the Kähler sector similar to the operator expansions in the superpotentials of family symmetry models. When the family symmetry is broken, the fields in the effective theory become non-canonical, and have to be rescaled and mixed. This process can change the Yukawa textures, but we show that the effects on physical observables are sub-dominant provided that the textures are hierarchical.</p
Direct liquid crystal templating of mesoporous silica and platinum
No full textMesoporous silicas have been prepared with hexagonal (H1) pore morphologies from TMOS/Brij 56/water/HCl mixtures. A detailed study of the synthesis of mesoporous silica from such mixtures revealed that ordered structures are formed at both high (~50 wt%) and low (~0.1 wt%) surfactant concentrations. The liquid crystal phase behaviour of Brij 56 in water showed that at low surfactant concentrations an H1 structure formed from a phase separated solution. At the high concentrations of surfactant the H1 phase was homogeneous throughout the sample and the hexagonal pore structure was a replica of the initial H1 lyotropic phase with ~3.6 nm diameter pores and ~1.7 nm thick walls.Direct liquid crystal templating of platinum has been studied by the reduction of a platinum salt in the aqueous domains of an H1 phase to C16EO8. The most successful method of preparing H1 platinum employed reduction with iron metal at room temperature. BET surface area analysis showed the mesoporous platinum to have a surface area of ~60 m2g-1. This is almost twice the surface area for commercially available platinum black materials. The pore size of the H1 materials was found to be ~2.9 nm with ~3.9 nm thick walls. A phase diagram study of the C16EO8/H2PtCl6/H2O system made it possible to obtain cubic (V1) and lamellar (Lα) mesoporous platinum. Finally, mesoporous silicas have been successfully loaded with H2PtCl6 and reduced to platinum metal as a method of preparing a supported platinum catalyst. The platinum was found to aggregate into particles rather than line the pores of the mesoporous structure after reduction.</p
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
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