1,720,973 research outputs found
Effect of wind turbine wakes on wind-induced motions in wood-pole overhead lines
No full textWood-pole overhead conductor lines are known to be subject to different wind induced motions, some which lead to conductor fatigue over long periods and others that can cause severe damage over short, isolated incidences. These lines are often located in rural areas and, with the ever increasing deployment of onshore wind farms, the potential impact of the wind turbine wakes on these conductor motions is a matter of interest. Discussion of the potential effects of conductor fatigue on wood-pole overhead conductor lines is important as this could impact the planning, modelling and siting of onshore wind farms. This paper presents a literature analysis of both the mechanism by which different conductor motions are excited and wind turbine wake characteristics with specific interest at low levels akin to wood-pole height. The archival value of this paper is that experimental data from an active wind farm, at wood-pole overhead line heights, is analysed and discussed for the first time and the results show that wake effects at these heights are likely to be minimal. However turbulent buffeting in particular is cited as a problem of interest and the potential effects of wood-pole motions are outlined
A reliability evaluation of offshore HVDC transmission network options
Full text linkThere are ambitious targets in place for the development of large amounts of offshore renewable energy in the coming years. The offshore wind sector is expected to provide the vast majority of the projected growth which means large scale and far from shore projects are likely to become common. The transmission distances involved suggest HVDC technology is likely to be deployed and analysis to date has suggested there will be value in delivering co-ordinated offshore grids as opposed to simpler radial connection to shore. However, there are numerous technology and design options available for the delivery of offshore HVDC networks and, given the offshore climate can makes access for component maintenance or repair challenging, the reliability performance of different options is an important factor which has not been explored in much of the existing literature. This thesis details a novel methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore or the interconnection of regions. A sequential Monte Carlo simulation methodology is used that allows investigation of realistic offshore phenomena such as the weather dependency of component repair times. A number of case studies are examined and a full cost benefit analysis is performed which compares the capital and operational costs, electrical losses and reliability performance of each grid option. There is shown to be clear value in options that include a degree of inherent redundancy and it is also shown that alternative protection strategies which avoid the use of expensive DC circuit breakers are potentially viable at lower cost and little expense to performance. An investigation of the key drivers behind overall offshore grid reliability is also made and it is found that low probability, high impact faults such as transmission branch failures have the greatest influence.There are ambitious targets in place for the development of large amounts of offshore renewable energy in the coming years. The offshore wind sector is expected to provide the vast majority of the projected growth which means large scale and far from shore projects are likely to become common. The transmission distances involved suggest HVDC technology is likely to be deployed and analysis to date has suggested there will be value in delivering co-ordinated offshore grids as opposed to simpler radial connection to shore. However, there are numerous technology and design options available for the delivery of offshore HVDC networks and, given the offshore climate can makes access for component maintenance or repair challenging, the reliability performance of different options is an important factor which has not been explored in much of the existing literature. This thesis details a novel methodology for investigating the reliability of different offshore grid design options for the connection of offshore wind power to shore or the interconnection of regions. A sequential Monte Carlo simulation methodology is used that allows investigation of realistic offshore phenomena such as the weather dependency of component repair times. A number of case studies are examined and a full cost benefit analysis is performed which compares the capital and operational costs, electrical losses and reliability performance of each grid option. There is shown to be clear value in options that include a degree of inherent redundancy and it is also shown that alternative protection strategies which avoid the use of expensive DC circuit breakers are potentially viable at lower cost and little expense to performance. An investigation of the key drivers behind overall offshore grid reliability is also made and it is found that low probability, high impact faults such as transmission branch failures have the greatest influence
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
Reliability analysis of design options for offshore HVDC networks
No full textThere is growing interest in developing offshore HVDC networks to connect both offshore wind power and provide interconnection between regions. There are a number of technology, topology and protection options available to developers each with varying levels of design complexity, capital cost and system redundancy. This paper highlights some of the available options and outlines a methodology for investigating the performance of a number of these through an investigation of their reliability against a lifetime of expected fault conditions, principally through a calculation of the expected level of curtailed energy associated with each network design. A number of case studies are investigated to provide a comparison between options including designs with and without HVDC circuit breakers and with varying levels of interconnection and system redundancy. The paper shows that there are potentially significant benefits in terms of reduction in curtailed energy through use of redundant paths for power transmission in the network design and that these can in certain cases outweigh the increased capital expenditure associated with their implementation. An investigation into the need case for HVDC circuit breakers is carried out through a comparison with an alternative sectionalised HVDC network topology and the impact on system reliability is found to be negligible in comparison to the cost of the breakers. Offshore network reliability is also found to be highly sensitive to input assumptions for failure and repair rates and the variability within the results was found to be large meaning it could be difficult to accurately predict the reliability of future offshore network implementations
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