1,720,955 research outputs found
ONDA TRASVERSALE STAZIONARIA INDOTTA DAL DISTACCO ALTERNATO DEI VORTICI IN CORRISPONDENZA DI UNA SCHIERA DI CILINDRI VERTICALI
Get PDFAn array of vertical cylinders in an otherwise uniform open channel flow can generate a
seiche in the transverse direction due to the lift associated with vortex shedding behind
each cylinder. Seiche amplitude attains a maximum at resonance, i.e., when the vortex
shedding frequency is close to the natural standing wave frequency.
The phenomenon at hand was studied both theoretically and experimentally.
A model to predict the maximum seiche amplitude has been proposed. The model is
based on the analytical solution of the linearized shallow water equations.
A large set of accurate experimental data has been collected aimed at validating the
proposed model and increasing our knowledge about the phenomenon.
The results are encouraging:
- the maximum relative wave amplitude is found to depend on hydraulic parameters, such
as the Froude number, and geometric parameters, such as the cylinders diameter and
density, and the channel width. The effects of these parameters are properly included in
the model to predict the maximum relative amplitude of the seiche, A/h. This is confirmed
by the good agreement between the theoretical and experimental results. In addition, the
proposed model agrees quite well with further experimental data available in the literature;
- for the first time two peaks of A/h in mode 1 have been detected;
- the formation of a longitudinal progressive wave, which composed with the transverse
seiche produces a metachronal wave, was experimentally observed.
The latter two points deserve further investigations.
The first two chapters of the thesis introduce the phenomenon and its main theoretical
aspects; the third chapter describes the mathematical model; the fourth chapter illustrates
the experimental investigation; the comparison between theoretical and experimental
results are presented and discussed in the fifth chapter; the sixth chapter is devoted to
some preliminary investigations on the longitudinal wave
Vortex-induced cross-flow seiching in cylinder arrays
No full textAn array of vertical cylinders in an otherwise uniform open channel flow can generate a seiche in the transverse direction due to the lift associated with vortex shedding behind each cylinder. Seiche amplitude attains a maximum at resonant conditions, i.e., when the vortex shedding frequency is close to the natural standing wave frequency. In this work we propose a model to predict maximum seiche amplitude based on the analytical solution to the linearized shallow water equations. The model prediction compares favorably with available experimental data from the literature outperforming pre-existing models. The model is also used to highlight that even small disturbances in the flow largely affect the dynamics and can dramatically reduce the wave amplitude
Free surface waves induced by vortex shedding in cylinder arrays
Get PDFThe paper presents and discusses the results of an accurate and extensive experimental investigation on the waves that originate when an array of cylinders is placed in an otherwise uniform open channel flow. The study was originally aimed at providing new and more accurate data to calibrate and validate a theoretical model recently proposed in the literature. However, two interesting characteristics of the phenomenon at hand, never reported in the literature, also emerged from the experimental study, i.e. (i) the wave produced by the cylinders is actually a metachronal wave rather than a pure transverse seiche; (ii) two different resonant conditions exist for each single wave mode, i.e. two typical Strouhal numbers characterize the resonance frequency of vortex shedding from the cylinders in an array. Evidence of the metachronal wave, as well as some preliminary data on the longitudinal component of this wave, are given in the paper. Also, the double resonance condition is experimentally demonstrated and discussed
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
- …
