1,721,001 research outputs found
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
Characterization of electrically insulating coatings for soft magnetic composite materials by means of surface sensitive analytical techniques
No full textPowder metallurgy (PM) is a cost effective and efficient process for producing net-shaped parts of high tolerances and homogeneous properties in large production volumes. These are few of the reasons why this technique is preferred in manufacturing soft magnetic composite (SMC) materials for electromagnetic applications. The concept of SMC consists of encapsulating pure iron particles with an electrically insulating coating which yields compacts of high bulk resistivity and isotropic magnetic behaviour. Such materials provide great freedom in design and exhibit improved magnetic performance compared to more traditional laminated steels and ferrites for a wide range of frequency applications.
In the present thesis, surface characterization of such type of composite powder in as-received state was performed using surface sensitive analytical techniques. Information regarding the nature of the surface layer is important in designing the process and tailoring the properties of a product towards a desired application. The material under examination was commercially available phosphated iron grade which was analyzed using X-ray photoelectron spectroscopy (XPS) and high resolution scanning electron microscopy (HR SEM) coupled with energy dispersive X-ray analysis (EDX). Based on these techniques, thickness estimation, morphology, coverage, chemical state and compositional depth profile analysis of the insulating coating was conducted.
The aim of this investigation was to evaluate the effect of the surface characteristics and geometry of powder on such type of analyses. For this purpose, gas and water atomized high purity iron grades, having spherical and irregular shape respectively, were used. Both kinds of powder were covered with uniform oxides layers of different thicknesses and they were both divided into different particle size fractions. Furthermore, standards and flat samples of similar composition to the metal powders were prepared and evaluated accordingly using additional thermoanalytical and X-ray diffraction (XRD) techniques in order to acquire reference values.
The results showed that the as-received state appears to have a greater contribution of oxide thickness than when it is fractioned. This is supposed to be a result of the fact that the unsieved powder has a significant difference in the particle size and this can cause more shading effects during the XPS analysis.Moreover, the SMC powder exhibited a complex surface layer structure consisting of a mixture of iron oxide and iron phosphate compounds of the order of few nanometres
Effect of Temperature on Mechanical Properties of Railway Wheel Steels [Elektronisk resurs]
No full textOne of the most important aspects in railway operation is the interaction between rail and wheel. The contact conditions give rise to wear and damage in both components. Medium carbon steels are used in these components due to their combination of high strength and good wear properties in relation to cost. In service, high surface temperatures develop because of frictional heating on traction, braking, curving and occasional full slippage. Furthermore, long-term block braking may heat the wheel rim to over 500°C. It is thus relevant to examine the high temperature performance of wheel material as well as the decrease in strength after thermal exposure. In the current thesis, two railway wheel steels are examined. These are the medium carbon steels UIC ER7T and ER8T (~0.55 wt.% C), heat-treated to a near pearlitic microstructure with some 5–10% pro-eutectoid ferrite in the wheel tread surface. Specimens were extracted from virgin wheels and pre-strained either monotonically or cyclically, to imitate plastic deformation developing in the wheel tread surface in service. Both un-deformed and pre-strained materials were heat treated at various temperatures from 250°C to 650°C for various time durations, and the change in room temperature hardness as measured before and after heat treatment was analysed. Samples were analysed using Scanning Electron Microscopy (SEM), to examine microstructure degradation. Additionally, Electron Backscatter Diffraction Analysis (EBSD) was used to evaluate if orientation gradients in the pearlitic colonies affect the spheroidisation of the pearlitic microstructure that is observed at higher temperatures.Analyses after the room temperature hardness measurements showed that hardening due to strain ageing takes place at around 300°C while microstructural degradation caused softening at higher temperatures. Spheroidisation of the pearlite started to become visible at 450°C for the un-deformed material and at around 400°C for the pre-strained. The spheroidised areas appear to have lost their initial orientation gradients after spheroidisation and obtain a more uniform orientation.Cyclic tests at elevated temperature revealed cyclic hardening at around 300°C, as an effect of dynamic strain ageing. At higher temperatures, cyclic softening followed due to a combination of increasing thermal activation and spheroidisation
Influence of combined thermal and mechanical loadings on pearlitic steel microstructure in railway wheels and rails [Elektronisk resurs]
No full textOne of the most important aspects in railway operation is the interaction between rail and wheel. The contact patch between these two components is around the size of a small coin, and since high loads act on this small area, stresses will give rise to wear and damage in both components. Frictional forces on the surface of wheels and rails caused by recurring train acceleration, braking, curving and occasional slippage can cause cyclic plastic deformation and heating, which in turn causes an aligned, anisotropic microstructure with altered mechanical behaviour. Control of material property degradation is an important topic for guiding maintenance, as well as ensuring safety of railways, since it will allow for a more accurate prediction of material wear and lifetime. The thesis focuses on the mechanical properties of railway wheel and rail steels after exposure to elevated temperatures and plastic deformation. Specifically examined are the carbon wheel steels, UIC ER7T and ER8T (~0.55 wt. %C) and rail steel R260 (~0.72 wt. %C). During their service life, the surface layers of rails and wheels are subjected to very high rolling contact loads. These lead to accumulation of large shear strains close to the running surface. Moreover the high thermal loads that wheels experience when block brakes are used can cause severe degradation of the material microstructure, more specifically spheroidisation of the pearlite, which combined with plastic deformation (that makes the material more prone to spheroidisation) can lead to severe deterioration of the material’s mechanical properties. Both un-deformed and pre-strained wheel materials were heat treated at various temperatures from 250°C to 600°C for various durations, and the change in room temperature hardness was analysed. Additionally, Electron Backscatter Diffraction Analysis (EBSD) was used to evaluate if orientation gradients in the pearlitic colonies affect the spheroidisation of the pearlitic microstructure, that is observed at higher temperatures. Uniaxial (tension-compression) and biaxial (including torsion) low cycle fatigue tests were performed to study the behaviour of R7T and R8T material at different temperatures. The influence of hold times as well as the ratchetting behaviour with mean stress effects were also studied. Virgin rail material was twisted using a biaxial machine to various shear strain levels to create a microstructure representative for the surface layer observed in field samples. The microstructure was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and hardness measurements. The results showed that wheel material hardening due to strain ageing takes place at around 300°C while microstructural degradation caused softening at higher temperatures. Spheroidisation of the pearlite started to become visible at 450°C for the un-deformed material and at around 400°C for the pre-strained. The spheroidised areas appear to have lost their initial orientation gradients after spheroidisation and obtain a more uniform orientation. Cyclic tests at elevated temperature revealed cyclic hardening at around 300°C, as an effect of dynamic strain ageing. At higher temperatures, cyclic softening followed due to a combination of increasing thermal activation and spheroidisation. Biaxial testing showed a more severe effect of strain hardening and shorter fatigue life. For the rail material, the dislocation density was found to increase with increasing shear strain. The flow stresses calculated using microstructural parameters such as dislocation density and interlamellar spacing of the pearlite seem to agree well with those evaluated from hardness measurements
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