1,720,975 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
Thermal Buckling in CWR Tracks: Critical Aspects of Experimental Techniques for Lateral Track Resistance Evaluation
No full textAfter the introduction of continuous welded rail, thermal track buckling has been recognized to be one of the unsolved problems caused by this technological railroad improvement. In general, both weak ballast strength in the lateral direction and large alignment defects are the principal causes of such phenomenon.
In the UIC 720 Leaflet, which is the reference standard for the realization and maintenance of continuous welded rail tracks, two safety criteria against thermal track buckling are described: one is based on the maximum (∆Tmax) and minimum (∆Tmin) buckling temperatures, the other only on the minimum buckling temperature.
In the literature, it is found that a correlation exists between ∆Tmax and the maximum (or peak, FP) lateral resistance value of the tie-ballast system, and, analogously, between ∆Tmin and the minimum (or limit, FL) lateral resistance. For this reason, railway technicians had to paid special attention in the assessment of FP and FL.
Because FP concerns lateral displacements equal to 5÷10 mm, and FL occurs for lateral displacements greater than 80÷100 mm, some researchers have proposed to measure FP with a quasi-non-destructive experimental technique, the Single Tie Push Test (STPT), and, successively, to evaluate FL as a function of FP by empirical formulas, in place of the experimental evaluation of the full lateral resistance curve of the tie-ballast system.
Based on these considerations, a concerning issue arises whether it is sufficient, and above all safe, to use the simpler, less destructive, and less expensive STPT technique, which requires that only one tie is detached from the rails, or if it is necessary to perform lateral resistance tests on track panels composed by 4 to 6 ties, as in the case of the Discrete Cut Panel Pull Test (DCPPT).
For this purpose, in this paper the experimental results obtained in situ in full scale conditions with the two testing techniques are reported, and the differences obtained by performing tests with one, two, and four ties are analyzed with the aim of ensuring a safe evaluation of the main input parameters required for buckling temperatures calculation.
It is found that the limit lateral resistance depends neither on the chosen experimental technique, nor on the compaction level of the ballast bed, whereas the peak lateral resistance appears to be dramatically altered if it is evaluated by mean of the STPT, with serious risks of an unsafe evaluation of the buckling temperatures
On the effects of multiple railway track alignment defects on the CWR thermal buckling
No full textThe lateral stability of the continuous welded rail (CWR) depends on a number of parameters which contribute to the progressive loss of the initial alignment of the track and its consequent predisposition to deform sideways, gradually or sharply, with serious risks for the safety both of passengers and operators. Different types of initial lateral defect, in terms of shape and size, are introduced by many authors in their own numerical and analytical model, but essentially all of them can be traced back — except for small “personalizations” — to the model proposed by Andrew Kish, who hypothesized the existence of a misalignment defect having the shape of a sine curve extended for half-wavelength, characterized by amplitude and wavelength values typical of the USA railroads. Moreover, all previous studies focused their attention on the introduction, in a geometrically perfect railway track, of a single defect confined in a zone of finite dimensions and having a rather simple geometry which qualitatively approximates the real defect, with the aim of simplifying the calculation of the buckling temperatures of the track associated with such geometry.
In this paper, it was preliminarily analyzed the way the defect introduced in the track affects the critical temperature values. It started with a defect created artificially, applying to a geometrically perfect track and in the absence of thermal loads, a lateral displacement in the central transversal section of the track, and calculating, with the hypothesis of linear elastic behavior, the resulting deformed shape, which was assumed, after zeroing the corresponding stress field, as the input geometry for the subsequent buckling calculation. The deformed shape so obtained, being a Zimmermann deformed shape type, has no geometrical discontinuities near the defect and interprets in a natural way the defected geometry of the track, due to the dependence of its configuration on the flexural stiffness of the entire track in the lateral plane.
Afterwards, modeling was carried out taking into account the real behavior of the track after the loss of its rectilinear configuration: the defect was created simulating the response of the track to a momentary lateral load — resulting, e.g., from train passages — which succeeded to cause a permanent displacement resulting from the elastic-plastic response of the track. The deformed shape of the track obtained in this way was used as the input geometry for the calculation of the buckling temperatures, once without resetting the stress field induced in the structure by the loading–unloading hysteresis cycle, and then considering the track free from internal stresses. The results show that both the numerical model that contemplate the defect introduced “plastically”, and that where the track is free from internal stresses, lead to more conservative results against the risk of thermal buckling in railway tracks made with CWR.
A better approximation of the realistic representation of a generic defected railway track was pursued considering an indefinite number of defects distributed along the track, where each defect was characterized by different amplitude and wavelength values. The obtained results show that the presence of multiple defects further reduces the safety factor against the thermal track buckling phenomenon. The paper ends with the proposal of an evaluation criterion that takes into account the effects of multiple alignment defects on the critical buckling temperatures in continuous welded rail tracks
Train-Induced Load Effects on the Thermal Track Buckling
No full textThermal track buckling is probably the major problem due to the advent of continuous welded rail track. In fact, when the rails temperature rises over a critical value, the track can buckle, suddenly or progressively, in the lateral plane. Both poor ballast conditions and large lateral alignment defects are the principal causes of such phenomenon.
In a previous paper, a parametric finite element model for thermal track buckling simulation was presented and validated by comparison with analytical results of the literature. In this study, the finite element model has been further validated by comparison with analytical and numerical results obtained by three other authors.
Moreover, to take into account the effect on the buckling temperatures of the vertical loads due to train passes, the tie-ballast lateral resistance has been modified along the track, taking into account the vertical reaction forces distribution induced by axle loads.
A sensitivity analysis has been carried out both for tangent and curved track, considering two values of the alignment defect amplitude, and different values of the parameters that characterize actual railway vehicles.
It is found that the conditions to trigger progressive buckling (△Tmax ≈ △Tmin) are attained with small values of the truck center distance, and in a more accentuated manner in the presence of high values of the lateral alignment defect.
△Tmax and △Tmin increase with axle spacing, and this increase is more pronounced for low values of the truck center spacing. △Tmax and △Tmin also increase with curve radius, but decrease for increasing values of the misalignment defect amplitude.
In explosive buckling conditions (△Tmax ≠ △Tmin), there is a limit value of the truck center distance above which the vertical load has no more effects, and the results of the static thermal buckling are found
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
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