1,720,965 research outputs found
Technical KPIs for microgrids
No full textThe design of electrical systems with renewable and conventional in-house generation involves economic, environmental and technical aspects. Often these instances are conflicting: conventional sources have lower Capex and good controllability, while renewable sources have lower Opex and are environmentally friendly but often present erratic behaviors. For these reasons, the best design solution is typically a variable mix of conventional and renewable sources. Today no standardized tool or procedure is available for evaluating and quantifying the technical aspects that drive the design of a Microgrid. Economical aspects are a consequence of the selected set-up, and may lead to an iterative design. This paper defines a set of technical Key Performance Indexes (KPI) that gives a quantitative evaluation of the technical performances of a Microgrid for the comparison of different design solutions. The proposed KPIs consider the system stability, the power quality, the saved fossil fuel, and the maintenance demand for conventional machines, and they can be used for an economic analysis of different technical solutions and sizing
Real time simulator for microgrids
No full textMicrogrids today include more and more renewable sources both for environmental and economic reasons. The advantage of microgrids is their capacity of running isolated. The presence of largely uncontrollable sources (PV plants and wind farms) makes the grid control a complex task. During the design stage it is mandatory to consider the expected variations of both loads and sources to identify proper solution for stabilizing the Microgrid when it runs isolated. The paper presents a simulator that was developed to support the design of the Microgrid both in terms of power devices and control techniques. The main goal of this simulator is to test the automation system of the Microgrid before its site installation. The simulator calculates the dynamic behavior of conventional generators, renewable source, and loads. The model of renewable sources includes the expected power variations as well as the random profile of loads. If required, energy storage systems can be integrated in the simulator. All the control set-point of controllable equipment and the calculated frequency and voltage of the Microgrid are interfaced with the control system using a standard Ethernet-base fieldbus. Such a solution makes it possible to study different control logics and to tune the control parameters of the system using the real control system. The data exchange between the simulator and the control system is identical to the real data flow that will be found in the Microgrid. With the use of the simulator, the control system of the Microgrid is implemented during the design stage, with reduced development, testing, and commissioning times
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
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