1,720,963 research outputs found
Low-Frequency Variations of Force Coefficients on Square Cylinders with Sharp and Rounded Corners
Full text linkSquare lighting poles with sharp or round corners have been observed to exhibit large amplitude oscillations with a frequency that is near that of their first mode. This frequency is one order of magnitude lower than that of the vortex shedding frequency for the observed wind speeds. As such, lock-in resonance between the vortex shedding and the poles motions has been ruled out as the cause of these oscillations. In this work, numerical simulations of flows over square cylinders with different aspect ratios and cross-sectional shapes have been carried out to explore and quantify low-frequency variations of the aerodynamic forces and their sources. The results show that low-frequency components are a basic aspect of the flow over finite length cylinders and are associated with the three-dimensional flow characteristics near the free end of the cylinder. This aspect is related to the loss of synchronization of the vortex shedding which, in turn, results in variations of the mean drag coefficient along the cylinder. This ability to numerically simulate the flow over a lighting pole and detailed results, as presented here, could be used to overcome wind tunnel test limitations imposed by the size of the test section and blockage ratio, and of meeting geometric similarity requirements for high aspect ratio configurations. Consequently, results from such simulations could play an important role in improving code specifications which, to date, have been based on wind tunnel simulations
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
Il caso di Poggio Meta. Indagini sul versante orientale del colle
Full text linkIl lavoro illustra i risultati delle indagini archeologiche e di topografia urbana effettuate nell'estate del 2014 sul versante orientale della collina di Poggio Meta, all'interno dell'abitato di Akragas. E' stato messo in luce parte di un isolato, la cui cronologia va dall'età arcaica alla tarda età ellenistica, e, anche in seguito alle indagini da telerilevamento (ripresa a bassa quota da drone e indagini georadar) è stato possibile avanzare delle ipotesi sul piano urbanistico della città, che in questa area presenta due orientamenti sovrapposti e leggermente divergenti, verificando in tal modo alcune ipotesi avanzate nella carta archeologica del Parco di Agrigento
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
Porosity effect on tensile behavior of Ti-6Al-4V specimens produced by laser engineered net shaping technology
No full textMicrostructural characteristics of additively manufactured Ti-6Al-4V specimens are analyzed in this study. Laser Engineered Net Shaping technology, a direct energy deposition additive manufacturing process, is used to fabricate specimens. Effects of process parameters including machine head laser power, head write speed, layer height, hatch spacing, and powder flow rate on the morphological features of the material are investigated. A first batch of samples is built with a combination of parameters leading to full density metal parts across each layer and near-zero defects likewise more conventional process techniques (i.e. wrought and casting). A second batch of samples is built with a set of processing parameters aimed to induce defects within the parts like voids and porosity. Samples from both batches were stress-relieved in order to remove internal residual stresses generated by the additive manufacturing process. Optical microscopy, scanning electron microscopy and X-ray diffraction were used to characterize the microstructure of all samples. Tensile properties were measured after the stress-relief heat treatment. It was found that Laser Engineered Net Shaping technology parts are strongly sensitive to variations of building process parameters. Different structure morphologies were observed for different incident energies and cooling rates due to the combination of laser power and head write speed. The grain size distribution and shape are influenced by the powder flow rate resulting in either equiaxed or columnar grain microstructures with the development of material defects such as pores, gas entrapment and lack of fusion. Non-porous specimens revealed comparable tensile and ductility properties with the wrought counterpart; however, porous specimens were found to have a reduced strength and ductility
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