Critical current and microstructure of uniaxially aligned, polycrystalline YBa2Cu3O7−δ

Three processing routes that generate uniaxial alignment but otherwise yield very different microstructure and critical current are compared. Fine grain size and c-axis alignment are obtained in magnetically aligned ceramics, pyrolyzed thick films, and in situ deposited thin films. The dense, well-aligned microstructure of the in situ process produces the highest zero field critical current Jc > 104 A/cm2 at 77 K. However, the critical current is suppressed in low magnetic field, suggesting that uniaxial alignment is not sufficient to avoid Josephson-type intergranular coupling. Above 1 T, the critical current of the aligned ceramic dominates in spite of its less ideal microstructure. The critical current in this high field region is one to two orders of magnitude greater than that of nonaligned material. This result implies the existence of a 3-d percolative network of strong links.

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High-Field Critical Current and Mechanical Properties Of In Situ Processed V3Ga Superconductors

Advances in Cryogenic Engineering Materials ◽

10.1007/978-1-4613-3542-9_51 ◽

1982 ◽

pp. 515-524 ◽

Cited By ~ 14

Author(s):

H. Kumakura ◽

K. Togano ◽

K. Tachikawa

Keyword(s):

Mechanical Properties ◽

Critical Current ◽

High Field

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Cherenkov and Slow Cyclotron Instability in Periodically Corrugated Cylindrical Waveguide with Low Magnetic Field Region

IEEJ Transactions on Fundamentals and Materials ◽

10.1541/ieejfms.124.477 ◽

2004 ◽

Vol 124 (6) ◽

pp. 477-482 ◽

Cited By ~ 5

Author(s):

Hoshiyuki Yamazaki ◽

Osamu Watanabe ◽

Yuichiro Yamashita ◽

Makoto Iwai ◽

Yoshitaka Suzuki ◽

...

Keyword(s):

Magnetic Field ◽

Cylindrical Waveguide ◽

Field Region ◽

Cyclotron Instability ◽

Magnetic Field Region ◽

Slow Cyclotron ◽

Low Magnetic Field

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A Computer-controlled, Fully Automatic NMR/NQR Double Resonance Spectrometer

Zeitschrift für Naturforschung A ◽

10.1515/zna-1992-1-266 ◽

1992 ◽

Vol 47 (1-2) ◽

pp. 395-400 ◽

Cited By ~ 1

Author(s):

Feng Zhenye ◽

Edwin A. C Lücken ◽

Jacques Diolot

Keyword(s):

High Field ◽

Double Resonance ◽

Low Frequency ◽

High Sensitivity ◽

Automatic Tuning ◽

Zero Field ◽

Field Region ◽

Fully Automatic ◽

Computer Controlled ◽

Frequency Power

AbstractA completely automatic computer-controlled NMR/NQR double resonance spectrometer is described. It features automatic tuning of the low, variable frequency power amplifier, thus permitting untended use over long periods, with high sensitivity and signal reproducibility. The sample is transferred between the low-frequency, zero-field region and the high-field region using compressed air and the possibility of switching on a field of several tens of gauss during the transfer of the sample is also included

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HIGH VERSUS LOW FIELD VISCOMETRIC CHARACTERIZATION OF BIDISPERSE MR FLUIDS

International Journal of Modern Physics B ◽

10.1142/s0217979207045840 ◽

2007 ◽

Vol 21 (28n29) ◽

pp. 4922-4928 ◽

Cited By ~ 10

Author(s):

G. T. NGATU ◽

N. M. WERELEY

Keyword(s):

Magnetic Field ◽

Yield Stress ◽

High Field ◽

Magnetic Flux Density ◽

Flow Curves ◽

Bingham Plastic ◽

Low Field ◽

Mr Fluids ◽

Low Magnetic Field

Our bidisperse magnetorheological fluids are suspensions of micron (2-10μm) and nanometer (~40nm) scale magnetic iron particles in silicone or hydraulic oil. Earlier studies were conducted to determine the yield stress of these fluids at low magnetic field induction. These studies have shown the absence of saturation yield stress implying the possibility of a higher yield stress by increasing the applied field. In this study, three different bidisperse MR fluids were investigated to determine the maximum available yield stress that can be obtained at or near saturation magnetic flux density. The iron loading in the fluids varied from 50% to 80% by weight. Two types of MR cells, a low field and a high field cells, were used for the investigation. Using a parallel disc rheometer alternatively equipped with one of the two MR cells, the flow curves of the MR fluids were obtained and their yield stress determined. The yield stress of the MR fluids as a function of applied magnetic field was identified using the Bingham-Plastic constitutive model. Results show that the high field cell (maximum 1 Tesla) was able to measure shear stress up to saturation, whereas the low field cell (maximum 0.26 Tesla) could not.

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Testing of a Dual Field Magnetic Flux Leakage (MFL) Inspection Tool for Detecting and Characterizing Mechanical Damage Features

2008 7th International Pipeline Conference, Volume 2 ◽

10.1115/ipc2008-64377 ◽

2008 ◽

Cited By ~ 1

Author(s):

Alex Rubinshteyn ◽

Steffen Paeper ◽

Bruce Nestleroth

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Residual Stresses ◽

High Field ◽

Mechanical Damage ◽

Magnetic Flux Leakage ◽

Low Field ◽

Field Unit ◽

Low Magnetic Field ◽

Flux Leakage

Battelle has developed dual field magnetic flux leakage (MFL) technology for the detection and characterization of mechanical damage to pipelines. The basic principle involves the use of a high magnetic field between 140 and 180 Oersted (11.1 to 14.3 kA/m) and the use of a low magnetic field between 50 and 70 Oersted (4 to 5.6 kA/m). At high magnetic field levels, the flux leakage signal is primarily influenced by changes in the geometry of a pipe wall. At low magnetic field levels, the MFL signal is due to residual stresses and metallurgical changes as well as geometry changes to the pipe caused by mechanical damage and wall thinning. A decoupling signal processing method developed by Battelle is used to isolate the portion of the mechanical damage signals due to metallurgical damage and residual stresses, which allows the characteristics of a dent-gouge feature to be more clearly differentiated. The decoupling method involves first scaling down the high field signal to the level of the low field signal, and then subtracting it from the low field signal. This produces a decoupled signal that is primarily influenced by the residual stresses and metallurgical changes caused by mechanical damage. Rosen has developed a tool to test the dual field technology and is evaluating tool performance by running the tool in a 30 inch diameter pipeline segment. The tool itself is composed of three separate modules coupled together: a high field unit downstream of a low field unit which is downstream of a caliper arm unit that is used to detect and characterize reductions in the internal diameter. The general and magnetic design of the tool, along with the scaling algorithm is discussed. Results from a pull test in a pipe section with dents whose geometry has been independently characterized are also discussed. This work is partially funded by the U.S. Department of Transportation, Pipeline and Hazardous Materials Safety administration (DOT PHMSA) and the Pipeline Research Council International, Inc. (PRCI).

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Acoustic End Effects in Magnetohydrodynamic Submerged Vehicular Propulsors

Journal of Ship Research ◽

10.5957/jsr.1992.36.1.69 ◽

1992 ◽

Vol 36 (01) ◽

pp. 69-76

Author(s):

John S. Walker ◽

Gita Talmage ◽

Samuel H. Brown ◽

Neal A. Sondergaard

Keyword(s):

Magnetic Field ◽

Inertial Force ◽

Zero Field ◽

Uniform Field ◽

Field Region ◽

Characteristic Ratio ◽

Fringing Field ◽

Field Lines ◽

Channel Configuration ◽

The Magnetic Field

This paper treats the effects near the ends of the channel on the transmission and reflection of periodic acoustic waves generated at some cross section inside a magnetohydrodynamic (MHD) seawater propulsion system. A region of high uniform magnetic field inside the MHD submerged vehicular propulsor is separated from the essentially zero magnetic field outside the channel by a nonuniform, fringing magnetic field at each end of the channel. The channel configuration chosen here is that of a straight, rectangular duct with electrically insulating top and bottom walls perpendicular to the magnetic field and highly conducting sidewalls parallel to the field. In particular, the mathematical analysis focuses on determining the percentage of the incident wave which is reflected by the fringing-field region back into the uniform-field region and the percentage which is transmitted through the fringing-field region into the zero-field region. The key parameter is the acoustic interaction parameter N, which is the characteristic ratio of the electromagnetic body force opposing motions across magnetic field lines to the inertial "force" in the acoustic wave. Solutions are presented for the fundamental, plane acoustic mode for arbitrary values of Ν and for all acoustic modes for Ν < 1. The amplitudes of the reflected and transmitted waves depend on the wave frequency, the length of the fringing-field region, N, and the type of wave mode. The magnetic field introduces a strong anisotropy with strong damping of modes involving transverse motions across magnetic field lines and with weak damping of modes involving transverse motions along field lines. This is the third in a series of articles on MHD marine propulsion from the David Taylor Research Center MHD propulsion program [Brown et al (1990), Tempelmeyer (1990)].

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