1,721,069 research outputs found
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No full textPhasor Measurement Unit with Digital Inputs: Synchronization and Interoperability Issues
Full text linkIn recent years, electrical substations are experiencing a rapid transition toward a fully digital measurement infrastructure in terms of data acquisition, storage, and processing. The IEC Std 61850-9-2 defines the data format, also known as sampled value (SV), to be employed by instrument transformers, merging units, and controller devices. In this scenario, it is reasonable to expect that the phasor measurement units (PMUs) will be directly connected with digital instrument transformers and will be required to process directly the SV data stream. In this article, we present the design and development of a stand-alone PMU based on digital inputs. The prototype has been characterized in terms of estimation accuracy and enriched with a novel functionality that allows for monitoring the time quality of the SV data stream. In this way, the device truly becomes an intelligent electronic device (IED) that guarantees higher interoperability and a more robust management of sporadic synchronization issues. The proposed results confirm the potential of SV-based PMUs and highlight the possibility of further enhancement for synchrophasor measurements based on digital inputs only
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
Power Quality Meters Based on Digital Inputs: A Feasibility Study
No full textModern power systems are experiencing a rapid transition towards a fully digital monitoring and control paradigm. In compliance with the specifications of the IEC 61850 standards family, measurement data shall be output by non-conventional instrument transformers according to the Sampled Value (SV) communication protocol. It is thus reasonable to expect that also Power Quality (PQ) measurements shall rely on SV data streams. Furthermore, due to the limited sampling frequency values considered in the standard, it is essential to evaluate the impact of different samples per cycle or packet loss conditions while detecting a PQ event. This paper investigates the feasibility of a PQ meter specific for voltage dips detection based only on SVs. To this end, a prototype hardware and software architecture is presented and characterized in standard and real-world test conditions. An experimental validation against a commercial device confirms the potential of the proposed SV-based PQ meter and the performance dependence on SV data stream integrity
Improved Fine Particles Monitoring in Smart Cities by Means of Advanced Data Concentrator
Full text linkTraffic reduction and air-quality improvement are among the main goals of several projects worldwide. This article presents a fine particle monitoring based on heterogeneous air quality mobile sensors and an advanced data concentrator (AdDC), so that the level of pollution in the urban area, where few accurate fixed measurement stations are present, can be assessed with better accuracy. Some urban buses are used to carry low-cost sensors, thus implementing a mobile sensor network and increasing the time and space resolution of air quality information. The data obtained by these low-cost sensors are significantly affected by uncertainties, also due to atmospheric factors, such as humidity. The proposed AdDC processes all the obtained measurements and exploits the information obtained by the accurate fixed stations to improve the accuracy of the low-cost mobile sensors. In particular, a new compensation methodology, specifically targeted to the fine particles monitoring, is proposed. The monitoring of relative humidity is added, with the relevant on-the-fly calibration, so that the measured values can be used to correct the effects of humidity on PM2.5 sensors. The validity of the proposed system is proven by means of simulations performed on an appropriate set up
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