1,720,956 research outputs found
Volume Reduction of Traction Power Inverter EMI Filter Based on Mitigation Techniques at the Source
Get PDFSwitching converters require effective EMI filters to comply with conducted emission regulations. However, these
filters often pose significant challenges, being expensive, bulky and heavy. The situation is further exacerbated with the latest generation of converters, utilizing WBG semiconductor devices, which operate at higher switching frequencies. Reduction of the filter size can be achieved through conducted EMI mitigation techniques that address emissions at the source, particularly at low frequencies. This paper analyzes the CM filter volume reduction when using two CM mitigation techniques acting at the source, namely Spread Spectrum Modulation (SSM) and the Delay Compensation Technique (DCT). The considered techniques are implemented on a WBG traction power inverter and the volume reduction of the CM EMI filter is evaluated through computer simulations
From Radio to In-Pipe Acoustic Communication for Smart Water Networks in Urban Environments: Design Challenges and Future Trends
Get PDFThe smart management of water resources is an increasingly important topic in today’s
society. In this context, the paradigm of Smart Water Grids (SWGs) aims at a constant monitoring through a network of smart nodes deployed over the water distribution infrastructure. This facilitates a continuous assessment of water quality and the state of health of the pipeline infrastructure, enabling early detection of leaks and water contamination. Acoustic-wave-based technology has arisen as a viable communication technique among the nodes of the network. Such technology can be suitable for replacing traditional wireless networks in SWGs, as the acoustic channel is intrinsically embedded in the water supply network. However, the fluid-filled pipe is one of the most challenging media for data communication. Existing works proposing in-pipe acoustic communication systems are romising, but a comparison between the different implementations and their performance has not yet been reported. This paper reviews existing works dealing with acoustic-based ommunication networks in real large-scale urban water supply networks. For this purpose, an overview of the characteristics, trends and design challenges of existing works is provided in he present work as a guideline for future research
A Wireless Communication System for Urban Water Supply Networks Based on Guided Acoustic Waves
Get PDFThe structural complexity of real-world pipeline networks makes it difficult to derive physics-based models of acoustic propagation. This work deals with the design of a communication system based on the propagation of acoustic waves in water-filled pipes. A method based on the experimental characterization of the communication channel is proposed. This approach is applied to an urban water distribution pipeline, and a black-box model representing its frequency response is obtained. The derived two-port model is used for the simulation of a complete communication system, comprising transmitter and receiver models, with the aim of using the water pipe as a wireless communication channel. It is shown that the choice of modulation parameters is critical in order to deal with issues such as the frequency selectivity of the channel and multipath wave propagation. A communication system is presented and the experimental results of the communicated data are provided
A Baseband Wireless VNA for the Characterization of Multi-Port Distributed Systems
Get PDFFrequency characterization of spatially-large structures has become increasingly required, mostly in the fields of Structural Health Monitoring and Communication Systems based on non conventional media. When the ports of the system under measurement are far apart, methods based on traditional wired instruments become unattractive for field applications, due to the increased complexity, cost and signal integrity related issues. Aiming towards removing the wired connection from the ports of the system under test and the elaboration unit, the main issue to be dealt with is the time-synchronization of measurements at the ports. This contribution proposes a solution to such an issue by presenting a Wireless Vector Network Analyzer, suitable for the characterization of distributed systems. For this purpose, a wireless synchronization scheme is proposed, which is based on the disciplining of the signal sampling clock from the 1-Pulse-Per-Second reference signal. The proposed synchronization method reduces clock jitter at different ports at 1.13 μs over a 300 s observation interval. The hardware and software implementation of the system are detailed and experimental results proving its operation are provided
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
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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