1,721,028 research outputs found
Evaluation on the operational state of turboexpanders in a helium refrigerator for nuclear fusion experimental devices using principal component analysis
Full text linkORCID 0000-0002-1989-867XThe operational state of helium turboexpanders has been evaluated using principal component analysis (PCA). For the evaluation, two models which were single and multiple ones were utilized. The single and the multiple models assess a single turboexpander and seven turboexpanders, respectively. In the model development, we used measurement data of helium turboexpanders for a cryogenic system in the Large Helical Device. Using the two models, the changes in the turboexpanders' condition before and after the occurrence of the trouble were clarified. Consequently, the PCA is very useful to monitor the turboexpanders. Comparing the two models, the single is more practical than the multiple one.journal articl
Investigating the Effect of Coil Length, Alignment Errors and Cooling Down on a Superconducting Magnet With Active Shielding for Rotating Gantry
Full text linkORCID 0000-0002-1989-867XA superconducting magnet with active shielding has been proposed for use in a heavy-ion beam rotating gantry in order to decrease weight. The magnet consists of two types of coils, dipole and active shielding coils, both of which are wound using Nb-Ti wires. In this study, three-dimensional coil configurations were designed, based on coil cross-sections designed in a previous study. Using the coil configurations, the magnetic field distribution in the longitudinal and radial directions of the coil and its peak magnetic field were calculated. The results indicated that the effect of the coil end section on magnetic field distributions became greater as the coil length becomes shorter. Also, the difference of the coil length has no impact on the peak field. In addition, the influence of coil alignment errors on the electromagnetic (EM) force, and that of cooling-down on coil deformation were investigated, using a coil cross-sectional model. As a result, EM forces caused by alignment errors of several mm in the shielding coil were negligible, compared to EM forces generated in the coil under a rated operation. Also, the maximum deformation of the coil cross-section was a few millimeters when the coil was cooled from 300 K to 5 K.journal articl
Electromagnetic-Structural Analysis of a Superconducting Magnet With Active Shielding for a Rotating Gantry
Full text link0000-0002-1989-867XAs a magnet utilized for a rotating gantry in heavy particle radiotherapy, a superconducting magnet with active shielding has been proposed to reduce the magnet weight. The magnet is composed of a dipole coil and an active shielding coil wound with NbTi wires. In this study, an electromagnetic-structural analysis of the magnet with active shielding was conducted using an FEM model. The results of the analysis indicate that the coil deformation, due to an electromagnetic force, slightly affects the field quality but negligible for the operation. The design concept of superconducting magnets with active shielding is valid in terms of magnetic field and the support structure for a rotating gantry. In addition, based on the previous study, the weight of the superconducting magnet with active shielding was revaluated. As a result, the superconducting magnet with active shielding can be one-third lighter than a superconducting magnet surrounded with an iron yoke, in terms of the magnet weight per unit length
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
Self-field measurements of a REBCO Rutherford-type cable
No full textORCID 0000-0002-1989-867XSelf-field measurements of a Rutherford-type cable immersed in liquid nitrogen have been performed. A 1-meter straight Rutherford-type cable composed of 60 REBCO tapes (12 sub-cables) was tested. The measurement results indicated that the self-field was unaffected by the cable energization ramp-rate. Based on the measurement results, a current center position within the cable cross-section was investigated during cable energization. The current center position remained unchanged during the charging. Consequently, the current distribution of the Rutherford-type cable was stable.
In addition, the 1-meter straight Rutherford-type cable was compared to other cable samples composed of stacked REBCO tapes. Under the same sample shape and cooling condition, the Rutherford-type cable and the stacked assembled in rigid structure (STARS) cable have similar characteristics with respect to the current center position during cable excitation.journal articl
Measurements of self-field and voltage for the REBCO stacked tapes assembled in rigid structure (STARS) conductor at 77 K
No full textThe measurements of self-fields and voltages for the stacked tapes assembled in rigid structure (STARS) conductor were carried out when the conductor immersed in liquid nitrogen was energized. In the measurements, a 3 m straight line shaped STARS conductor, which is composed of 45 REBCO tapes (15 tapes × 3 rows) embedded in a copper stabilizer, was used as a conductor sample. The measurement results indicate that the ramp rate at the conductor excitation and the one-time thermal cycle of the conductor do not affect the self-fields but the voltages.
The current center position in the conductor cross-section during the conductor excitation was analyzed from the measurement results of the self-fields. The current center position always maintains the same position in the middle of the cross-section during the excitation. The analysis indicates that the current distribution of the STARS conductor is stable during the excitation. In addition, two-dimensional magnetic field calculations were conducted using the various models for the cross-sectional configuration of the STARS conductor. As a result, the calculation results agree with the measurement results regarding the self-fields
Modeling of Stacked Single-Layer Coils Wound with Bi2223 Tapes Using a Lumped Constant Circuit
Full text link0000-0002-1989-867XStacked single-layer (SSL) coils wound with Bi2223 HTS tapes were modeled with a lumped circuit. Using the model, we investigated the effect of the joint resistance at coil terminals on the generated voltage for the SSL coils. The investigation shows that the joint resistance must be reduced as much as possible to restrain the voltage occurred in the SSL coils and each joint resistance should be uniform to make the current distribution uniform in the SSL coils. Additionally, we investigated the effect of inductance on the current distribution in the SSL coils and the effect of the tape's degradation on the coil performance. As a result, the current distribution of the SSL coils can be uniform due to the joint resistance even though the SSL coils have different inductances in each coil winding. Further, the current distribution and the voltage of the SSL coils are influenced by the tape's degradation.journal articl
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