1,720,956 research outputs found
Numerical study of bicycle racing wheels aerodynamic performances
Get PDFImproving the aerodynamic performance in one of the major challenges in the engineering research
applied to racing bicycle. In fact, aerodynamic drag is the main source of losses in cycling and causes
between 70% and 90% of total losses in flat road pace (i.e., when not climbing).
Moreover, also lateral forces imposed by crosswinds play an important role because they can
destabilize the bike itself.
The body of the cyclist is actually the most important source of drag, because of its relevant frontal
area. However, it is necessary to improve also the bike’s components aerodynamics, which account
for about the 33% of the total drag. This quite relevant percentage is mainly due to the wheels and
the frame design.
According to Greenwell, wheel drag is responsible for 10% to 15% of total aerodynamic drag;
therefore improving the design of this component can reduce the resistance of the bicycle by 2-3%.
These numbers, in view of the high level required by either the today’s competitions or the bicycle
market justify the effort involved in cycling components aerodynamics.
The aim of this work isto assess the capability of CFD RANS simulations to predict the aerodynamic
performance of modern racing bicycle wheels, and therefore build a numerical testing method to
help the comparison between different solution and design.
The Thesis is subdivided in five chapters after an introduction to bicycle aerodynamics and a
literature review of the previous literature regarding the wheel aerodynamics; we give a look at the
theory regarding the computational fluid dynamics and the different model used in this work.
An initial method is build tested validated and refined showing the capabilities of the CFD to resolve
the aerodynamic forces on a rotating wheel using a simpler steady-state analysis, applying the MRF
method imposing a rotating frame to the region containing the wheel.
Different wheels were tested and the results compared with wind tunnel results obtained by
Campagnolo; using this method we compared different design and introduced a performance index
to characterize the wheel performances.
We performed brief analysis using and unsteady state model and a rigid body motion to compare
the method with the steady model.
Good agreement with experimental wind tunnel studies suggests that the approach we outline
holds considerable promise. Owing to the flexibility of this methodology, it is now possible to use
CFD to provide more definitive answers on some of the open questions within the competitive
cycling and triathlon communities.
Additional word regard the testing of an open-source code, because commercial codes are indeed
expensive, we tried a simple three-spoke model with the OpenFOAM code, and highlight the pro
and the cons of an open-source code.
Finally, there is a brief description of different force balance layouts
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
Studio numerico sperimentale delle perdite meccaniche di un motore motociclistico
No full textil lavoro qui presente riguarda le perdite meccaniche relative ad un motore motociclistico, il lavoro eseguito prevede: 1-Rivedere il metodo di Morse integrandolo con una simulazione numerica per separare le perdite totali misurate in perdite organiche e perdite per attrito. 2-Utilizzare il metodo del trascinamento con montaggio parziale per conoscere le perdite specifiche per ogni componente appartenente al motore in provareservedEmbargo permanente per motivi editorial
Studio numerico sperimentale delle perdite meccaniche di un motore motociclistico
No full textil lavoro qui presente riguarda le perdite meccaniche relative ad un motore motociclistico, il lavoro eseguito prevede: 1-Rivedere il metodo di Morse integrandolo con una simulazione numerica per separare le perdite totali misurate in perdite organiche e perdite per attrito. 2-Utilizzare il metodo del trascinamento con montaggio parziale per conoscere le perdite specifiche per ogni componente appartenente al motore in prov
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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