121,892 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
No full textThe 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
First measurement of the current sharing temperature at 80 kA in the ITER Toroidal Field Model Coil (TFMC)
No full textCoupling 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
No full textThe 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
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
Analysis of the ITER central solenoid insert (CSI) coil stability tests
No full textAt the end of the test campaign of the ITER Central Solenoid Insert (CSI) coil in 2015, after 16,000 electromagnetic (EM) cycles, some tests were devoted to the study of the conductor stability, through the measurement of the Minimum Quench Energy (MQE). The tests were performed by means of an inductive heater (IH), located in the high-field region of the CSI and wrapped around the conductor. The calorimetric calibration of the IH is presented here, aimed at assessing the energy deposited in the conductor for different values of the IH electrical operating conditions. The MQE of the conductor of the ITER CS module 3L can be estimated as ~200 J ± 20%, deposited on the whole conductor on a length of ~10 cm (the IH length) in ~40 ms, at current and magnetic field conditions relevant for the ITER CS operation. The repartition of the energy deposited in the conductor under the IH is computed to be ~10% in the cable and 90% in the jacket by means of a 3D Finite Elements EM model. It is shown how this repartition implies that the bundle (cable + helium) heat capacity is fully available for stability on the time scale of the tested disturbances. This repartition is used in input to the thermal-hydraulic analysis performed with the 4C code, to assess the capability of the model to accurately reproduce the stability threshold of the conductor. The MQE computed by the code for this disturbance is in good agreement with the measured value, with an underestimation within 15% of the experimental value
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