1,721,096 research outputs found
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
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
A Review and Comparison of Floating Offshore Wind Turbine Model Experiments
Get PDFAbstractFloating offshore wind turbines provide more access to deeper water than conventional fixed-bottom wind turbines, which expands the viable area for wind energy development, reduces visibility from shore, and can potentially be located in areas with a higher and steadier wind characteristic. However, since floating turbines are in the early prototype stage of development, there are very limited data to use for validating computer models of these machines. This lack of validation increases uncertainty and risk for future installations. In lieu of large scale test turbines, which are expensive to build and operate, a few institutions have conducted small scale experiments in wave basins. This paper will present a review of the past and planned model-scale floating offshore wind turbine experiments, with a focus on types of data collected and challenges encountered by these tests.The objective of this review is to provide a background for the Integrated Research Program on Wind Energy (IRPWind), specifically for Work Packages 6.1 and 6.2. The goal of these work packages is to create a database of both fixed-bottom and floating offshore wind turbine test cases that can be accessed by researchers to verify and validate computer-aided engineering codes. The database will consist of a number of benchmarks that will validate different parts of a given design code. This review will discuss two model experiments that are likely to be included in the IRPWind database
Safety Indicators for the Marine Operations in the Installation and Operating Phase of an Offshore Wind Farm
Get PDFAbstractAs a measure of performance, safety indicators are already used for many types of operations, such as in the offshore oil and gas industry. The indicators are used by operators to enhance the safety and performance of the individual plants or vessels and total productivity of the system.This paper reviews existing safety analyses of the offshore wind industry, the onshore wind industry and offshore oil and gas indus- tries. An offshore wind farm is divided into subsystems and operational phases. Safety indicators are developed for the phases and subsystems by reviewing existing safety indicators from related industries and adapting them to the offshore wind industry. The indicators for the individual subsystems and phases are then combined to provide safety indicators for the whole wind farm over the lifetime. Finally, the indicators are matched against incident data from the offshore wind industry and an outlook for further research and indicator validation is given
The Compliant Tower Concept for Offshore Wind Turbines
Get PDFOffshore wind turbines are getting larger and the water depths where they are located are getting deeper as well. This causes problems of eigen frequencies for rigid structures where a jacket structure could be too expensive in depths around 50 meters. At this depth, floating structures will not be efficient due to the hydrodynamic behaviour and the mooring system for this depth can be challenging. That is the reason why compliant structures are analysed for depths around 50 meters due to their low eigenfrequencies of the structure while having a load path into the seabed.
For the realization of the thesis, two main tasks have been done. First, the implementation of a code to calculate all the steps in the design of an offshore wind turbine. This method has covered from the determination of natural frequencies of the structure and the solution of the dynamical equation of dynamics to obtain displacements depending on time for different environmental conditions in the tower, to the obtention of the force response of the structure and the code checks necessary to satisfy the guidelines and requirements for Ultimate Limit State, Fatigue Limit State and Serviceability Limit State. This methodology will be the base for a preliminary design of the structure. The main theory to develop this program has been the finite element method and the type of beam used for the calculation can be decided by the user between the Bernoulli beam and the Timoshenko beam.
The second main task is the design of a compliant tower for a specified site location using the methodology for preliminary design create beforehand. The location of the compliant tower is the Dutch North Sea and an analysis has been performed to try to locate the optimal natural frequencies for the structure based on the frequencies of the environmental loads acting on the tower. Different tests have been done and different options for the design have been studied like the use of guy cables to control the displacements, the incorporation of a mass trap in the structure and changes in geometrical aspects have been done to achieve a lower natural frequency. These changes are the length from the seabed level to the rotor-nacelle assembly and the slenderness of the monopile studied. All the elements introduced in the code can be changed easily and therefore, this program will be useful for many different cases.
The rotor-nacelle assembly used has a rating of 5 MW and a rotor radius of 126 m. Possibility of a larger wind turbine has been studied to reduce even more the natural frequencies.
Another important factor like the soil-tower interaction has been also considered and the analysis of the behaviour of the soil has been done according to p-y curves. Differences in behaviour for different types of soil has been evaluated.
After arriving to a final design of the compliant tower satisfying all the limit states evaluated, the results of the program are shown and it can be seen that the representation of deflections are reliable while the data for bending moment reactions and shear forces is not completely exact due to the higher influence of bending strain energy than for the shear energy for high flexibility members.
Although further research is needed about compliant towers, this preliminary analysis is satisfactory to ensure that compliant towers could become much more common in the future
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
Computer-aided optimization of an offshore jacket for a wind turbine with a simplified load model
Get PDFIn this report the jacket structure of a 5MW reference offshore wind turbine has been explored in terms of structural redundancy and for optimisation of the node locations. This has been done by the creation and utilisation of fully parametric scripts that creates input and post processes results from Abaqus CAE. The dynamic nature of offshore wind turbine forms a basis for complex loading of the jacket structure. This makes the analysis work needed to fully understand such structures substantial. Fatigue may be the limiting factor for structure life time, and this has been the evaluating factor for results for both redundancy and optimisation. Five different load cases are employed to evaluate different weather, and give a fuller picture of what the structure may experience. Differences in the evaluated configurations show a nonlinear performance variation in the load cases, which complicates a clear optimal configuration. A further study of the lifetime expected distribution of load cases could be done to better understand this, but only the findings for the individual load cases has been presented in this report. For structural redundancy, the loss of a structural member shows disparity between members in the legs or braces, where the legs shows greater contribution to the stiffness and strength of the tower
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