1,721,100 research outputs found
Thermomechanical Pressure Analysis for HVDC Cables
No full textFor some mass-impregnated (MI) paper insulated HVDC cables, unacceptably high pressures or pressure drops occur at the insulation-sheath interface under rapid loading changes, due to a strong impregnant thermal expansion or contraction. As this can degrade cables by either causing sheath plastic deformations or introducing voids into the insulation, it is important to investigate/model this thermo-mechanical phenomenon. Based on the theory of elasticity, this paper presents an analytical calculation of interfacial pressures as a function of the cable loading. Results obtained will benefit both cable operators and manufactures by provide guidelines of rating calculations and insulation designs, following a thermo-mechanical constraint
An Investigation of thermal Ratings for High Voltage Cable Crossings Through the Use of 3D Finite Element Analysis
No full textWith the growing complexity of underground cable systems, cable crossings are inevitably found in urban areas in power distribution systems or sometimes even in transmission systems. It is critical to accurately rate such cables because dangerously high temperatures can occur at crossing points, resulting in premature aging of cable insulation and potentially cable failures. The only existing explicit method for rating cable crossings is IEC 60287 [1], which is analytical and makes a number of simplifying assumptions like constant surrounding ambient conditions. With improvements in computational power, 3D models based on Finite Element Analysis (FEA) become viable for rating crossing cables. This provides an alternative method to assess these problems using a more detailed cable representation and realistic environmental modelling. In addition, it allows the accuracy of the existing analytical method to be assessed. With the eventual aim of examining the accuracy of IEC 60287 for rating cable crossings, FEA models have been developed to allow a detailed comparison to the analytical calculation. Due to the complexity of the crossing structure, firstly two 400kV single XLPE cables crossing at right angles have been modelled. A sensitivity analysis on model parameters (for instance buried depth, cable spacing, crossing angle and cable length) has been conducted and compared against IEC 60287 to gain confidence of the modelling process. By extension of the modelling techniques developed for the single cables crossing case, a 3D FEA model of two directly buried three-phase cable circuits crossing has been created. Each circuit is horizontal in flat formation and the model is solved for various crossing angles and vertical spacings. The results of IEC 60287 is are compared against 3D FEA model with various ground boundary conditions and temperature-dependent ac conductor resistance, both of which have been suggested in previous work as main reasons accounting for the conservatism of the analytical method [2][3]
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
Induced Losses in Three-core SL-type High Voltage Cables
No full textIt is considered that the present IEC 60287 standard overestimates the induced losses in SL-type armored cables, which are commonly used to connect offshore windfarms to the onshore grid. This paper addresses the issue through a series of equivalent-circuit models for the estimation of circulating-current, eddy-current, and armor losses in these cables. Finite-element models are used for further validation. Both the finite-element and the equivalent-circuit models use an equivalent-material representation of the armor layer, for which two calculation methods are developed. The results demonstrate clearly that the equation for armor loss in such cables as presently used in IEC standards is overly conservative
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
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