1,721,039 research outputs found
Sizing and economic assessment for auxiliar components and grid connection of a MgB2-LH2 hybrid power cable
No full textThe successful integration in the transportation of two very different commodities, namely electricity and liquid hydrogen LH2, in hybrid cables requires several auxiliary components, including storage tanks for hydrogen before and after terminal points, current leads designed for the efficient coupling and decoupling of current-cryogen flow within the transmission line, a pumping system to ensure the effective circulation of the cryogenic fluid and grid connections from the electric power production plant to the grid through the superconducting cable. These components significantly impact on the overall cost structure and are crucial for the potential market adoption of the technology. This study focuses the dimensioning of the auxiliary components through an evaluation of their thermal-hydraulic parameters, followed by an assessment of their effects on overall costs and economic viability. The reference case study is a 30 km-long MgB2 cable, capable of transmitting 10 kA at 30 kV of voltage, cooled by 20 K-liquid hydrogen. This provides essential insights into the potential scalability and sustainability of the proposed system
Design, Construction and Test of a Model Superconducting Quadrupole for the Interaction Region of Super B Factory
No full textSuper is an asymmetric energy e(+)e(-) collider operating at the gamma(4S) peak (root s similar to 10.58 GeV) to be built in Italy, with a design peak luminosity of 10(36) Hz/cm(2). In order to get the required high luminosity, a novel collision scheme, the so called "large Piwinski angle and crab waist", has been designed. This scheme requires that two doublets of high gradient superconducting quadrupoles (denominated in the Super naming scheme as QD0 and QF1) are placed as close as possible to the interaction point. This layout is critical because the space allowed to the doublets is very small. An advanced design of the quadrupole has been developed, based on the so-called helical coil concept. The paper discusses the design and construction concept of a model of the superconducting quadrupole based on NbTi technology
Analysis of Electric Fault in a MV DC MgB 2 Transmission Line Cooled by Liquid Hydrogen
No full textA submarine superconducting cable for the hybrid transmission of electricity and liquid hydrogen from a wind and solar offshore plant is under investigation in the frame of a project funded by the Italian Ministry of University and Research. The DC MgB2 line is designed to connect the 300 MW offshore plant to the Ravenna port (Italy), approximately 22 km away, at an operating voltage of 30 kV. In this work, an electric model based on a lumped-parameter circuit of a DC medium voltage (MV) line including a MgB2 conductor is coupled with a fluid-dynamic model suited to simulate fast thermodynamic transients in liquid hydrogen
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
Analysis of the Evolution of Accidental Transients in the Cooling of a MgB2-LH2 Hybrid Power Cable
No full textThe safe and reliable operation of superconducting cables is critically dependent on efficient cooling strategies, and this point becomes even more relevant when hybrid cables cooled by liquid hydrogen (LH2) considered. This study analyzes the evolution of accidental transients in the cooling of a submarine 30 km hybrid cable in MgB2, capable to transfer 10kA at 30 kV and a mass flow rate up to 1 kg/s of LH2 at 20 K. Three key failure scenarios are examined: a loss-of-flow accident (LOFA), a loss-of coolant accident (LOCA) and a loss-of-vacuum accident (LOVA). For each of the accidents, the phenomenology leading to the cable cooling deterioration is first discussed and the qualitative or quantitative evolution of the thermal-hydraulic transient in an unprotected situation is presented. The diagnostics most suited to detect the accident are then identified. This work, the first of its kind, suggests instrumentation to detect the occurrence of the different scenarios to protect the investment associated with the future hybrid power cables. The analysis shows that the loss of flow is easy to detect and the operators can reduce the cable power without any loss of LH2. The LOCA is more severe, as it requires fast detection that could be achieved using optic fibers, whereas overpressures and opening of relief valves are difficult to avoid especially for large ruptures. The LOVA is the most severe among the accidents investigated here, as it is difficult to detect without optic fibers
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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