1,721,061 research outputs found
Computational thermal-hydraulic analysis of the helium inlet options for the ITER Central Solenoid
No full textA new 3D CFD model has been developed and applied to the hydraulic analysis of three different inlet options for the ITER Central Solenoid. From the point of view of flow repartition among the petals, it appears that shorter, more compact options have even a marginal advantage over a long slit inlet; their hydraulic impedance is larger, but always within the allowable. No overheating associated to low n value of the Nb3Sn conductor is predicted for either inlet optio
Development and validation of the 4C thermal–hydraulic model of the ITER Central Solenoid modules
Get PDFThe ITER Central Solenoid (CS) consists of a stack of six modules, each made of 40 pancakes wound with Nb3Sn Cable-In-Conduit Conductors (CICCs) cooled with supercritical helium (SHe). All six modules (plus one spare) are to be individually cold-tested at the General Atomics final test facility in San Diego (USA), in order to check their performance; the first CS Module (CSM1) was tested in early 2020.A test campaign on a CSM Mock-up (CSM MU) wound with 16 dummy pancakes, i.e., with nonsuperconducting (copper) strands, was already carried out in San Diego at the end of 2017, for the commissioning of the test facility. The analysis of the CSM MU experimental data is presented here.Each CSM is a full magnet with 554 turns; it did not have any thermal-hydraulic (TH) or electrical sensors inside the winding due to insulation reasons, so that, e.g., SHe pressure, temperature and mass flow rate, as well as the voltage, were only measured at the ends of selected pancakes.Therefore, it was essential to employ a thermal-hydraulic (TH) model in order to obtain information on the quantities of interest inside the coil, e.g. which was the voltage across the coil at the moment when the current sharing temperature (TCS) was reached for the first time somewhere in that double-pancake (DP) during a TCS test.The TH model of the CSM, developed and implemented in the validated 4C code, and eventually adopted for the test preparation and interpretation, includes some free parameters, i.e., the inter-pancake and inter-turn thermal coupling, whose uncertainty is mainly due to the complex, multi-layer structure of the turn and pancake insulation. The calibration of these parameters is required to correctly capture the TH behavior of the CSM. For this purpose, the results of the experimental campaign on the CSM MU have been used. The detailed topology of the CSM MU is described and implemented here in a dedicated 4C model. Both slow and fast transients are used for the calibration, e.g., quasi-steady state heating of the SHe, entering a single DP and heat slug tests, respectively. It is shown that the transverse heat transfer within the winding pack could be largely overestimated if the ideal heat conduction across a bulk insulation layer is considered. The calibrated model is then validated on the CSM1 test results
Coupling and Hysteresis Loss Measurements on the ITER CS Module #4
No full textThe fourth CS Module (CSM#4) of the ITER Central Solenoid was tested in November/December 2022 at the premises of General Atomics, Poway, US. During the measurement campaign, the CSM#4 was submitted to dumps of the transport current from different initial values (from 0 to 40 kA) to 0 kA. The tests were performed both in virgin conditions and after 10 slow current cycles. This work analyses the experimental dumps of the CSM#4 to determine the losses in the CICC via the measurement of the energy deposited in the supercritical helium. The losses in the magnet are presented pointing out the impact of the slow current cycles. The latter also allow one measuring the hysteresis losses of the magnet. In the previous module tests, as well as in the tests of a single layer solenoid (referred to as CS Insert), it was very difficult to retrieve reliable values of the hysteresis losses in the CS conductor. However, the knowledge of hysteresis losses is crucial for a correct heat inventory of the magnet in operation. This study reports the results of their measurement, which represents a relevant added value of the CSM#4 tests. Finally, the experimental data are compared with the results of analytical models developed for the loss computation
Modeling the ITER CS AC Losses Based on the CS Insert Analysis
Get PDFThe cable-in-conduit conductor that will be used for the manufacturing of the ITER central solenoid (CS) modules has undergone a long series of qualification tests: the latest was performed in 2015 at QST, Naka, Japan, on the central solenoid insert (CSI) coil. In this work, the AC losses dataset collected during the CSI test campaign is interpreted using a lumped-parameter model for the coupling and hysteresis losses. The model is first benchmarked against the results of the THELMA code and then, after the implementation in the 4C thermal-hydraulic code, successfully validated against experimental data from tests performed on the CSI.With the validatedACloss model, the predictive analysis of the performance of the ITER CS is then carried out using again the 4C code, both in nominal conditions and with a reduced coolant mass flow rate in the most loaded pancake; it is shown that the minimum temperature margin required by the design is always satisfied, for both virgin (1 K) and cycled (1.5 K) conductor
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
AC Losses in the First ITER CS Module Tests: Experimental Results and Comparison to Analytical Models
Get PDFThe ITER Central Solenoid (CS) will be manufactured by assembling a stack of six modules, which are under fabrication by the US ITER organization and its subcontractors. The tests of the first CS Module have been performed at the premises of the General Atomics (GA) facility in Poway (US), in order to check compliance to the ITER requirements. Among other tests, the magnet was submitted to exponential dumps of the transport current from different initial values (10, 15, 20, 22.5, 25, 35, 40 kA) down to 0 kA. These tests are aimed at conducting DC breaker commissioning of the test facility and were used to measure the AC losses in the coil during electrodynamic transients. This paper presents the results of these measurements, along with a comparison with analytical computations of the losses in the magnet
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
- …
