IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
Volume 129, Issue 5
Displaying 1-8 of 8 articles from this issue
Review
  • Teruo Matsushita
    2009 Volume 129 Issue 5 Pages 339-344
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    Electromagnetic phenomena in superconductors are reviewed. In superconductor in a transverse magnetic field, the electromagnetic phenomena are described by the critical state model assuming a balance between the Lorentz force and pinning force. In this case the Josephson equation for the induced electric field, E = B × v, holds for the motion of flux lines with velocity v. On the other hand, the electromagnetic phenomena in a longitudinal magnetic field of current-carrying superconductor are quite different from those in the transverse magnetic field. For example, the Josephson relation does not hold and even a negative potential drop is locally observed in the resistive state above the critical current. In this review it is shown that these peculiar phenomena are explainable using the flux motion driven by a force-free torque, a restoring torque against rotationally shearing deformation of flux lines due to the force-free current parallel to flux lines.
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  • Katsumi Hattori
    2009 Volume 129 Issue 5 Pages 345-351
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    Despite its extreme importance and years of efforts, practical short-term earthquake prediction still remains to be achieved in future. However, earthquake-related electromagnetic phenomena are recently considered as a promising candidate for short-term earthquake prediction. There have been accumulated a lot of evidences of precursory signatures in a wide frequency range. This paper deals with various electromagnetic phenomena associated with the 2004 Sumatra-Andaman earthquake (M9) in order to show the state of the art of seismo-electromagnetics for prediction research. Both post- and/or co-seismic and pre-seismic phenomena such as ULF geomagnetic and ionospheric disturbances are presented.
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Paper
  • Kota Watanabe, Yoshinori Taka, Osamu Fujiwara
    2009 Volume 129 Issue 5 Pages 352-356
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    To evaluate the quality of wine, we previously measured the complex relative permittivity of wine in the frequency range from 10 MHz to 6 GHz with a network analyzer, and suggested a possibility that the maturity and alcohol concentration of wine can simultaneously be estimated from the Cole-Cole plot. Although the absolute accuracy has not been examined yet, this method will enable one to estimate the alcohol concentration of alcoholic beverages without any distillation equipment simply. In this study, to investigate the estimation accuracy of the alcohol concentration of wine by its Cole-Cole plots, we measured the complex relative permittivity of pure water and diluted ethanol solution from 100 MHz to 40 GHz, and obtained the dependence of the Cole-Cole plot parameters on alcohol concentration and temperature. By using these results as calibration data, we estimated the alcohol concentration of red wine from the Cole-Cole plots, which was compared with the measured one based on a distillation method. As a result, we have confirmed that the estimated alcohol concentration of red wine agrees with the measured results in an absolute error by less than 1 %.
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  • Tsuyoshi Maeno, Hiroya Ueyama, Michihira Iida, Osamu Fujiwara
    2009 Volume 129 Issue 5 Pages 357-362
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    It is well known that electromagnetic disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring-harnesses from vehicle-mounted printed circuit boards (PCBs) with common ground patterns with slits. To suppress the noise current outflows from the PCBs of this kind, we previously measured noise current outflows from simple two-layer PCBs having two parallel signal traces and different ground patterns with/without slits, which revealed that making slits with open ends on the ground patterns in parallel with the traces can reduce the conducted noise currents. In the present study, with the FDTD simulation, we investigated reduction characteristics of the FM-band cross-talk noise levels between two parallel signal traces for eighteen PCBs, which have different ground patterns with/without slits parallel to the traces and dielectric layers with different thickness. As a result, we found that the cross-talk reduction effect due to slits is obtained by 3.6-5.3dB, while the cross-talks between signal traces are reduced in inverse proportion to the square of the dielectric-layer thickness and in proportion to the square of the trace interval and, which can quantitatively be explained from an inductive coupling theory.
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  • Takashi Kurihara, Toshihiro Takahashi, Yoshinobu Mizutani, Hiroshi Suz ...
    2009 Volume 129 Issue 5 Pages 363-372
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    Three types of resin-coated papers were investigated; kraft papers and heat-resistant kraft papers partially covered with epoxy resin, and a kraft paper covered with phenol resin; those were laminated to certain thickness. They were thermally degraded at 120°C for 240 to 1320 hours, and their mechanical characteristics such as tensile strength and average polymerization degree were measured. As a result, it was found that the tensile strength of the first and second resin-coated papers was larger than that of the pressboard, but the tensile strength of the third one was smaller. As the effect of the heating time, it was found that the tensile strength of the first resin-coated paper decreased down to that of pressboards after 500 hours of heating time while those of the second and third ones almost retained the initial values after 1320 hours of the heating time. Then, electrical breakdown characteristics of composite insulation systems with a resin-coated paper and insulation oil were investigated. In the system, an oil-filled gap was artificially introduced between a resin-coated paper and a plane electrode to induce partial discharges (PDs) at the same location. PDs occurred before breakdowns and it was found that their PD inception electric field strength was almost as high as that of the pressboard and the effect of the heating time was negligible. It was also found that the electrical breakdown field strength has similar characteristics to those of the PD inception field strength; negligible effects of the type of resin-coated papers and the heating time. Electrical breakdown occurred at the oil-filled gap and the edge of a high voltage electrode.
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  • Keisuke Ishii, Kunihiro Nagata, Hiroshi Osawa, Noriyuki Nanba
    2009 Volume 129 Issue 5 Pages 373-378
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    The effects of the poling and the measuring conditions on the piezoelectricity were studied in foamed-fluorinated-ethylene- propylene-copolymer films having isolated voids with the average diameter of 0.05 mm. The piezoelectric constant in the thickness direction, d33 larger than 300 pC/N was observed in the samples poled at 16 kV for one minute. Because of the breakdown in the void walls, d33 decreased when the applied voltage was higher than 16 kV, or the poling period was longer than one minute. Even at the temperature higher than 170°C, the poled samples maintained d33 larger than 80 % of the value in the samples poled and measured at room temperature. The d33 considerably decreased under the static stress higher than 30 kPa. The pretreatments before the poling, such as a helium-gas displacement in the voids, a uniaxial compression, and an RF O2 plasma radiation greatly improved the piezoelectricity.
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  • Mika Nakano, Kenji Takahara, Toshinori Kajiwara
    2009 Volume 129 Issue 5 Pages 379-385
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    This paper describes the instructional design to develop communication ability for students in the electrical engineering majors. It is based on the case of Fukuoka Institute of Technology which started new courses for communication skills in 2007. A series of communication education from the freshman year to the third grade is systematized, considering the developmental process of students' argumentation. In the classes, students continually learn dialogue and cooperation through various styles of discussion, debate, presentation and so on. The first introductory class of all is “Communication Theory I”, which is aimed at developing self-awareness and improving discussion skills for interpersonal relationship. In this course, students acquire skills to construct their arguments about the given issues and to evaluate others' presentation performances each other. To cultivate students' communication ability, education should not be closed in a class, but support system from departmental level is essential.
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