1,721,016 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
Multiple linear regression MOS for short-term wind power forecast
No full textMàster en Meteorologia. Directors: Bernat Codina i Gregor GiebelShort-term (0 - 36 h ahead) wind power forecast is a central issue for the correct management of a grid connected wind farm. A combination of physical and statistical treatments to post-process Numerical Weather Predictions (NWP) outputs is needed for successful short-term wind power forecasts. One of the most promising and effective approaches for statistical treatment is the Model Output Statistics (MOS) technique. In this study a MOS based on multiple linear regression is proposed: the model screens the most relevant NWP forecast variables and selects best predictors in order to fit a regression equation that minimizes the forecast errors, utilizing wind farm power output measurements as input. The performance of the method is evaluated in two wind farms, located in different topographical areas and with different NWP grid spacing. Due to the high seasonal variability of NWP forecasts, it was considered appropriate to implement monthly stratified MOS. In both wind farms, first predictors were always wind speeds (at different heights) or friction velocity. When friction velocity is the first predictor, proposed MOS forecasts resulted to be highly dependent on the friction velocity - wind speed correlation. Negligible improvements were encountered when including more than 2 predictors in the regression equation. Proposed MOS performed well in both wind farms and its forecasts compare positively with actual operative model in use at Risø DTU and other MOS types, showing minimum BIAS and improving NWP power forecast of around 15% in terms of root mean square error. Further improvements could be obtained by the implementation of a more refined MOS stratification, e.g. fitting specific equations in different synoptic situations.Risø DTU - National Laboratory for Sustainable Energy - Technical University of Denmar
Evaluación del recurso eólico a escala micro. Aplicación a proyectos de electrificación rural
No full textEn proyectos de electrificación rural en la sierra andina se han comprobado las diferencias depotencial eólico entre casas de una misma comunidad; el objetivo de este estudio esdesarrollar y validar una metodología para realizar mapas de viento en estos contextos.Primeramente se analizan los métodos de evaluación del recurso eólico y se identifican lasherramientas más adaptas para el estudio en una comunidad (micro-escala); sucesivamente, secomparan diferentes programas de estimación de viento analizando los parámetros de entradamás importantes y se define un procedimiento estándar a utilizar para el estudio del recurso enuna comunidad. Mediante la elaboración de un manual de buenas prácticas, se esperacontribuir a la generación y difusión del conocimiento en la evaluación del recurso eólico paraproyectos de electrificación rural
Evaluación del recurso eólico a escala micro. Aplicación a proyectos de electrificación rural
Get PDFEn proyectos de electrificación rural en la sierra andina se han comprobado las diferencias de
potencial eólico entre casas de una misma comunidad; el objetivo de este estudio es
desarrollar y validar una metodología para realizar mapas de viento en estos contextos.
Primeramente se analizan los métodos de evaluación del recurso eólico y se identifican las
herramientas más adaptas para el estudio en una comunidad (micro-escala); sucesivamente, se
comparan diferentes programas de estimación de viento analizando los parámetros de entrada
más importantes y se define un procedimiento estándar a utilizar para el estudio del recurso en
una comunidad. Mediante la elaboración de un manual de buenas prácticas, se espera
contribuir a la generación y difusión del conocimiento en la evaluación del recurso eólico para
proyectos de electrificación rural
Design of off-grid renewable energy community electrification projects : analysis of micro-scale resource variations and development of optimization methods
Get PDFTesi per compendi de publicacionsProjects relying on renewable energies are a suitable and sustainable option to electrify isolated communities autonomously. These systems produce electricity in a clean and environmentally respectful way and their cost is often lower than national grid extension. Hybrid systems that combine different energy resources (wind and solar) and distribution through microgrids are the most efficient design configurations.
When considering hybrid systems and microgrids, the design of rural electrification projects is referred to as the AVEREMS problem. The optimization of the AVEREMS problem is a complex task that requires the use of specific support tools. In this context, some shortcomings have been encountered in the current state-of-the-art in the design of off-grid electrification projects based on renewable energies, in specific: the lack of knowledge about detailed wind resource studies for this kind of projects and the need of procedures for solving the AVEREMS problem considering generation also far from the demand in order to take advantage of best resource areas.
The main objective of this thesis is to tackle these limitations by means of: 1) defining a method for detailed wind resource assessment in rural electrification projects, 2) the development and 3) application of procedures to solve the AVEREMS problem considering micro-scale resource variations and generation in every point of a community (being a demand or a no-demand point).
Firstly, a method for detailed wind resource assessment is presented relying on the use of micro-scale wind flow models: the method is validated in two mountainous communities and applied for the design of a real project in Cape Verde.
Then, different solving procedures are developed: first some indicators are proposed to support algorithms¿ design, and then two procedures (a deterministic heuristic and a metaheuristic algorithm) are presented in order to solve the AVEREMS problem. Different algorithm versions are analyzed in order to select the ones that give best results. The proposed algorithms, besides considering generation in every point of a certain area (being a demand or a no-demand point), enhance the performance of the currently available tools.
Finally, the design of a real electrification project in Nicaragua is carried out including a micro-scale wind resource assessment and the application of the developed metaheuristic procedure for design optimization.
The wind resource assessment method and the solving procedures developed in this Thesis can be easily applied to support the design of off-grid rural electrification projects with renewable energies. Their utilization will improve projects efficiency and sustainability reducing some of the technical issues that still limit their implementation in isolated communities.Los proyectos de electrificación basados en energías renovables han demostrado ser una opción adecuada y sostenible para abastecer comunidades aisladas de forma autónoma. Estos sistemas producen energía de manera limpia y respetuosa del medio ambiente y su
coste es a menudo inferior al de extender la red eléctrica nacional. Las configuraciones de diseño más fiables y eficientes utilizan sistemas híbridos que combinan varios recursos (eólico y solar) y distribución mediante microrredes.
El diseño de proyectos de electrificación rural considerando sistemas híbridos y microrredes se ha definido como el problema AVEREMS. La optimización del problema AVEREMS es una tarea compleja que requiere el uso de herramientas de soporte.
Actualmente, el proceso de diseño de proyectos de electrificación basados en energía renovables presenta algunas limitaciones. Entre ellas, destacan la falta de conocimientos sobre estudios del recurso eólico y la necesidad de procedimientos para resolver el problema AVEREMS incluyendo la generación alejada de los puntos de consumo para aprovechar las áreas de mayor potencial.
El principal objetivo de esta tesis es abordar dichas limitaciones, mediante: 1) la definición de un método para evaluar en detalle el recurso eólico en proyectos de electrificación rural; 2) el desarrollo y 3) la implementación de procedimientos para resolver el problema AVEREMS considerando la variación del recurso a micro-escala y generación en todos los puntos (sean estos de consumo o de no-consumo) de una determinada área.
Primero se presenta un método para realizar estudios del recurso eólico mediante el uso de modelos de flujo de viento a micro-escala. El método se valida en dos comunidades montañosas y se aplica para el diseño de proyectos reales en Cabo Verde. Sucesivamente, se desarrollan diferentes procedimientos resolutivos: primero se definen unos indicadores de soporte al diseño, y sucesivamente se presentan dos algoritmos (uno heurístico y otro meta-heurístico) para resolver el problema AVEREMS. Se analizan diferentes versiones de los algoritmos para finalmente seleccionar las que obtienen los mejores resultados. Además de considerar generación en todos los puntos (de consumo o de no-consumo) de una cierta área, los algoritmos propuestos mejoran considerablemente las prestaciones de los métodos disponibles actualmente. Finalmente, se analiza el diseño de un proyecto de electrificación en una comunidad rural en Nicaragua incluyendo la evaluación de recurso a micro-escala y la aplicación del algoritmo meta-heurístico para la optimización del diseño.
La metodología para la evaluación del recurso eólico y los algoritmos resolutivos desarrollados en esta tesis se pueden fácilmente aplicar para suportar el diseño de proyectos de electrificación rural con energías renovables. Su utilización permitirá mejorar la eficiencia y sostenibilidad de estos proyectos reduciendo algunos de los problemas técnicos que limitan su implementación en comunidades aisladasDOCTORAT EN ADMINISTRACIÓ I DIRECCIÓ D'EMPRESES (Pla 2007
Evaluación del recurso eólico a escala micro. Aplicación a proyectos de electrificación rural
Get PDFEn proyectos de electrificación rural en la sierra andina se han comprobado las diferencias de
potencial eólico entre casas de una misma comunidad; el objetivo de este estudio es
desarrollar y validar una metodología para realizar mapas de viento en estos contextos.
Primeramente se analizan los métodos de evaluación del recurso eólico y se identifican las
herramientas más adaptas para el estudio en una comunidad (micro-escala); sucesivamente, se
comparan diferentes programas de estimación de viento analizando los parámetros de entrada
más importantes y se define un procedimiento estándar a utilizar para el estudio del recurso en
una comunidad. Mediante la elaboración de un manual de buenas prácticas, se espera
contribuir a la generación y difusión del conocimiento en la evaluación del recurso eólico para
proyectos de electrificación rural
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
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