1,721,456 research outputs found
Development of a volumetric 3D particle tracking velocimetry system and its application to mixing in a stirred tank
No full textQuantitative fluid flow visualization and measurements are highly demanded in mechanical, chemical, medical and many other science and engineering fields to investigate fluid phenomena, understand theoretical principles and support computational prediction. Three-dimensional Particle Tracking Velocimetry (3D-PTV) is a powerful and comprehensive measurement technique that provides instantaneous 3D volumetric velocity information and Lagrangian description of particle trajectories. This work is based on the 3D-PTV technique that was developed at the Institute of Geodesy and Photogrammetric at the Swiss Federal Institute of Technology, Zurich. Theoretical principles of the technique were studied based on geometric imaging and computer vision. A complete 3D-PTV system was designed, assembled, synchronized, and tested. A study of the accuracy of the 3D-PTV system in terms of the influence of each component was performed. 2D-PIV (Particle Image Velocimetry) measurements were done on the same experimental setup used in the 3D-PTV system. Results showed good quantitative agreement between the velocity information obtained with the two systems, which validates the results of the 3D-PTV measurement system. The developed 3D PTV system was applied to the study of mixing in a stirred tank showing that this technique has great potential for the study of low Reynolds number flows where the time-resolved trajectory of particles is important. Further improvement on the configurations and data analysis of the system can provide higher accuracy, higher spatial and temporal resolution, and less complexity, which will lead to an extension on its application.M.S.Includes bibliographical references (p. 116-118)by Ye Chen
A study of the fine-scale three-dimensional flow structures in turbulence using time-resolved stereoscopic scanning particle image velocimetry
No full textA time-resolved stereoscopic scanning particle image velocimetry (TR-SSPIV) system was developed to investigate the fine-scale 3D structures in free shear turbulent jets. The system provided a simultaneous measurement of the three-component velocity field in a three-dimensional volume (3D3C) with Kolmogorov-scale (eta) resolution, providing a true representation of the complete nine-component velocity gradient tensor. Quantitative visualization of the coherent structures at fine-scale turbulence is obtained and four basic structural shapes (sheets, tube, square ribbons and spherical blobs) are identified as building blocks of complex turbulent structures. The measurement volume had dimensions of 43eta x 20eta x 18eta, which allowed isolating individual structures. These rendered shapes had dimensions that range from 1.5-5eta to 20-30eta. The local acceleration du/dt is obtained and represented as 3D structures. These showed a strong anti-alignment with the convective acceleration term, which helps validate experimentally the Random Taylor Hypothesis. A novel vortex identification scheme is also introduced based on the local pressure. The method is compared to other published ones including enstrophy, Q, Lambda2 and Delta criteria. Four different flow configurations are tested and extensive statistical analyses are performed to study the probability density function (PDF), joint PDF, and spectra of the velocity gradients. The analysis also considered the vorticity, rate of strain, enstrophy, and dynamic parameters such as enstrophy production rate and energy dissipation rate. Accuracy assessments included result comparison to isotropy theory and evaluation of the local conservation of mass. The flow statistics and scaling of turbulence at fine scales are compared extensively to published theoretical, numerical, and experimental results.Ph. D.Includes bibliographical referencesby Ye Chen
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
supporting_information – Supplemental material for A new lignan from <i>Schefflera arboricola</i>
No full textSupplemental material, supporting_information for A new lignan from Schefflera arboricola by Chang-Qing Ye, Jia-Yi Zhang, Zhi-Cheng Ye, Mei-Tian Xiao, Xu-Dong Zhou and Jing Ye in Journal of Chemical Research</p
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
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