IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
Volume 125, Issue 2
Displaying 1-19 of 19 articles from this issue
Special Issue on Magnetic Shielding Technology and its Applications
Special Issue Review
Special Issue Paper
  • Yoshiaki Adachi, Masakazu Miyamoto, Jun Kawai, Gen Uehara
    2005 Volume 125 Issue 2 Pages 85-91
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Biomagnetometry is a powerful method for the investigation of the neural activity. We developed a multi channel superconducting quantum interference devices (SQUIDs) biomagnetometer system for the measurement of the evoked magnetic field from stimulated spinal cords. The system is equipped with three dimensionally configured SQUID vector gradiometers, which can detect not only the radial components of the magnetic field to the subject but also the tangential components. With the system, we could successfully observe the distribution of the evoked magnetic field corresponding to neuronal signals transmitting in the spinal cord of small animals as momentarily changing vector map.
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  • Kiyotaka Kamata, Kazutomo Yunokuchi, Keita Yamazaki, Kazuo Kato, Tomoa ...
    2005 Volume 125 Issue 2 Pages 92-98
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    The fluctuations of magnetic field (FMF) from automobiles of different shapes and sizes running north to south, and east to west are measured and the characteristics are grasped. The direction of magnetization of the automobile is assumed by the waveform and amplitude of the FMF obtained by the measurements. In this report, the distribution of disturbance magnetic fields around the automobile is measured, by which the size, direction and location of magnetic dipole is predicted. In order to obtain the size and direction of dipole M of the automobile, the distribution of disturbance magnetism around that is measured and is calculated, using the BTnet method. Finally, the amplitude of the FMF calculated using the size and direction of magnetic dipole M of the automobiles are compared with those measured.
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  • Kazuo Kato, Keita Yamazaki, Tomoya Sato, Akira Haga, Takashi Okitsu, K ...
    2005 Volume 125 Issue 2 Pages 99-106
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    We developed a new shielding system composed of shielding panels by means of an active compensation technique for biomagnetic measurements and electron beam lithography system. The new active compensation system has the main advantage that the panels can be assembled in any shape for the various demands because the unit panel is low weight and small size. In this study, we attempt to confirm the shielding performance of the shielding panel unit in itself and of combined several unit panels by numerical and experimental approaches. Shielding performance of the shielding panel unit and cubic model composed of 24 panels indicate 1/46 and 1/17, respectively.
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Paper
  • Yusuke Kudo, Toshiyuki Sugimoto, Yoshio Higashiyama
    2005 Volume 125 Issue 2 Pages 107-112
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    A free wire particle located in the electric field between parallel plate electrodes manifests several motions; standing, precession on the electrode, crossing and breakdown via the particle. During the stable standing or precessional motion, corona discharge involves inevitably. To clarify the influence of discharge phenomenon on the behavior of the wire particle, the corona discharge characteristic of the particle in the precession was investigated experimentally in a dc electric field formed with parallel plate electrodes where positive voltage was applied to the upper electrode. The waveforms of corona discharge current flowing through a 6mm-wire particle were measured under the two conditions when a free wire was in precession on the lower electrode and when a wire was fixed between the electrodes vertically with a spacing less than 1mm between the lower electrode and the bottom of the particle. From the comparison of the waveform of corona discharge occurring at the particle in precession with that of the fixed particle, it was found that both micro-gap discharge and negative corona occurred simultaneously only when the particle was in the precession with a relatively small elevation angle. The particle lifted up when the magnitude of corona discharge current was decreased bellow around 15 μA.
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  • Tetsuo Fukuchi, Koshichi Nemoto, Kouji Matsumoto, Yoshiki Hosono
    2005 Volume 125 Issue 2 Pages 113-118
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    An acousto-optic laser deflector was used for visualization of high-speed phenomena, such as shock waves and density perturbations accompanying an impulse discharge, or shock waves generated by laser-induced breakdown in air. Using a continuous wave laser as the light source, shadowgraphs of shock waves and density perturbations were obtained at shutter speeds down to 1μs. Results showed that shock waves propagated at a speed of 417 m/s in the case of an impulse discharge, and 485 m/s in the case of laser-induced breakdown. Pre-discharge phenomena such as leaders progressing from the high voltage electrode were also visualized. Compared to conventional high-speed imaging techniques, this method is useful when using a laser light source, since the acousto-optic crystal can accomodate high intensity laser light.
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  • Hiroshi Kanai, Naoki Hamamura, Motoshige Yumoto
    2005 Volume 125 Issue 2 Pages 119-124
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Surface modification of PMMA (polymethylmethacrylate) was carried out by the irradiation of low-energy nitrogen ions about 100 eV, which is expected to improve the surface property by introduction of a thin modified layer. To clarify the structure and the properties of the modified layer, depth profiles of composition and chemical bonds were analyzed using AR-XPS (Angle Resolved X-ray photoelectron spectroscopy). And, surface hardness was measured by using the nanoindentation test.
    From the results, it was confirmed that surface hardness increased and crosslinked structures containing oxygen with nitrogen bonds existed in the modified layer. It was suggested that the existence of the structure brought about the increase of surface hardness.
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  • Satoru Arakawa, Eiji Suzuki, Hiroyasu Ota, Kenichi Arai
    2005 Volume 125 Issue 2 Pages 125-132
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    When probes are positioned close to a device being tested, the electromagnetic field distribution is inevitably changed to some extent. The change affects the measurement accuracy and the operation of devices. In order to perform magnetic near-field measurement with high accuracy in the GHz frequency range, we are developing an optical magnetic field probe that consists of a loop antenna element and an LiNbO3 crystal. In this paper, the invasiveness of the optical magnetic field probe was quantitatively evaluated by experiment and FDTD method simulation. The undesired output caused by electric field is substantially suppressed owing to the symmetrical structure of the probe. The disturbance of the surrounding electromagnetic field is reduced by eliminating the metallic cable and consisting of a few metallic elements. The influence on operation of the device is comparatively small when the probe is positioned close to the device. This study indicated that the optical magnetic field probe is less invasive and suitable for an accurate measurement.
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  • Atsushi Sasaki, Yuji Niwamoto, Hidenori Itoh, Kohki Sato, Hiroaki Taga ...
    2005 Volume 125 Issue 2 Pages 133-137
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Hydrogenated amorphous silicon carbide films have been deposited on Si substrates using tetramethylsilane and hydrogen gas mixtures by the RF plasma CVD (chemical vapor deposition) technique. In situ diagnosis of chemical bonding states on the substrates exposed to plasmas has been also performed by FT-IR (Fourier transform infrared) spectrophotometry technique. The influences of the substrate temperature and the effective self-bias potential of the powered electrode on the impurities of deposition have been investigated. It has been found that the impurities of the deposited films were decreased sufficiently by increasing the substrate temperature to 1073 K. It has been also shown that the impurities were decreased by decreasing the effective self-bias potential of the powered electrode.
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  • Tadashi Kawamoto, Tadasu Takuma
    2005 Volume 125 Issue 2 Pages 138-144
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Abnormal electric field appears at a wedge-like edge of a conductor(electrode) or a dielectric interface, which usually becomes infinitely high. This paper analyses the electric field near such an edge by the analytical variable separation method and by the numerical one of the charge simulation method. The analysis focuses on the special conditions where the electric field becomes zero at an edge. These conditions are important for the insulation design to suppress the discharge inception at such edges of conductors and dielectric interfaces.
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  • Cheol-Kyou Lee, Yoshinobu Murakami, Naohiro Hozumi, Masayuki Nagao, Ka ...
    2005 Volume 125 Issue 2 Pages 145-152
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    This paper deals with the precision of the ultrasonic microscopy for biological tissue characterization. The estimation error of sound speed influenced by the selection of reference points for obtaining the reference signal is described. In well known scanning type microscope, a focused ultrasonic signal is irradiated to the glass substrate on which a thin sliced tissue is attached. The reflected signal from the front surface of the tissue is compared with the signal from the glass substrate on which no tissue is attached. As the scanning plane and glass substrate are not completely in parallel, it is necessary to locate the glass surface at each measuring point. For this purpose, several reference points on which no tissue is attached are selected in the view field. The equation of the plane representing the glass surface is consequently obtained using the reflection at these reference points. However, the glass surface has an apparent surface roughness. This brings an estimation error of the equation of the plane. This error can be reduced by increasing the number of reference points. In order to extract a sufficient number of reference points automatically, an algorithm using the reflected wave was proposed to discriminate the points where the glass surface is exposed. Although the estimation error of sound speed with three reference points was as large as 31 m/s (as the double of standard deviation), it was reduced into as small as 16 m/s, when 1000 reference points had been automatically extracted.
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  • Hiroyuki Toyota, Shigeyasu Matsuoka, Kunihiko Hidaka
    2005 Volume 125 Issue 2 Pages 153-158
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    A square pulse voltage is useful for studying electrical discharge physics and/or very fast transient overvoltage issues. This paper describes sparkover voltages and time lag (V-t) characteristics of SF6-N2 gas mixtures in a very short time range below a microsecond, which are measured by using a steep-front square voltage with a rise time of 16 nanoseconds and a peak value of 200 kilovolts. SF6-N2 gas mixture, which contains nitrogen gas at a ratio of 60 % or less, has equivalent dielectric strength to pure SF6 gas even in the short time range around 10 nanoseconds. Sparkover voltage and time lag characteristics are evaluated by using the equal area criterion even in the short time range below a microsecond.
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  • Takanobu Mori, Hiroyuki Sato, Ryukichi Takahashi
    2005 Volume 125 Issue 2 Pages 159-164
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Fe-13%Ni-Mo alloy is investigated in order to develop ferromagnetic field winding support shaft of superconducting generator. Solidification test and solidification simulation show that reducing Mo content of the alloy to 1.5% and selecting 1050mm-diameter electroslag remelting process is necessary to avoid harmful macro segregation in the ingot. A trial forging of Fe-13%Ni-1.5%Mo alloy having identical cross section of ferromagnetic field winding support shaft of 200MW machine is manufactured from 1050mm-diameter ingot. A series of test proves that it has no harmful macro segregation and has appropriate properties, that is, stable fracture toughness down to 4K, ferromagnetic property with high flux density, good machinability and weldability. An example of electrical design of 200MW machine shows that the ferromagnetic field winding support shaft can improve output density, efficiency and stability of electrical power system as compared to conventional nonmagnetic one.
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  • Yasushi Minamitani, Atsushi Ogami, Yoshio Higashiyama
    2005 Volume 125 Issue 2 Pages 165-171
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Streamer discharges generated by pulsed power are used for decomposition of harmful gas and liquid. The homogeneous formation of streamer discharges in a large volume in a reactor improves the efficiency of decomposition. To produce streamer discharges homogeneously, the performance of space ionization by a surface corona discharge for pre-ionization has been investigated. The increase of a pulse width from 20 ns to 100 ns brings the increase of about 2 times of ultraviolet intensity and an electron density. For the positive discharge with the pulsed voltage of 6 kV and the rise time of 11 ns, the electron density was increased from 1.2x108 to 2.3x108 cm-3 with the pulse width from 20 to 100 ns (FWHM). As the magnitude of pulsed voltage was increased from 6 to 10 kV, the ultraviolet intensity and the electron density were increased about 3 times. In contrast, the rise time of the pulsed voltage slightly affects the ultraviolet intensity and the electron density. The decrease of the rise time from 30 to 10 ns brings the increase of 5 % of the ultraviolet intensity and 10 % of the electron density.
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  • Naohiro Hozumi, Koji Nishioka, Takeshi Suematsu, Yoshinobu Murakami, M ...
    2005 Volume 125 Issue 2 Pages 172-178
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Feasibility of self-healing insulation system was studied. A silicone rubber without filler was mounted on a glass substrate with a needle electrode. An ac voltage with 4 kV in rms was applied. The voltage was cut off when the tree had propagated into 150 micrometers in length. After the cut-off, the partial discharge inception voltage was periodically observed. The partial discharge inception voltage had once reduced into as low as 2 kV. However, it gradually increased with time, and finally exceeded the tree inception voltage (4 kV) when 30 - 60 hours had passed. It was also observed by optical microscope that the tree gradually disappeared in parallel with the recovery of the partial discharge inception voltage. The same phenomenon was observed even if 1 kV ac voltage had been continuously applied during the process of the recovery. A simulation using a needle-shaped void was performed in order to clarify the mechanism of the self-healing effect. It was observed that the tip of the needle-shaped void gradually got wet with a liquid material. It would be the result of "bleed-out" of the low molecular component included in the rubber. The tip of the void was finally filled with the liquid, however, the rest of the needle-shaped void stayed without being filled. In this type of tree, it was suggested that the self-healing effect is expected if the diameter of the tree did not exceed ca. 5 micrometers.
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  • Hiroyoshi Kitabayashi, Haruhisa Fujii
    2005 Volume 125 Issue 2 Pages 179-184
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    In the fabrication of electronic products, charging of glass substrate induced in separation process is probable to cause the electrostatic discharge to the devices. We measured the charging potential of glass substrate which was separated from a plate, by using an electrostatic voltmeter. From the experiment, we obtained the following results. The contact electrification potential of glass substrate was dependent on the material of the plate. This phenomenon was related to their effective work functions. Furthermore, the charge quantity on glass depended on the number of contact with the plate and was higher in the smooth surface than in the rough surface.
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Letter
  • Taro Kimura, Takahisa Hayashi, Susumu Suzuki, Haruo Itoh
    2005 Volume 125 Issue 2 Pages 185-186
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Negative ion mobility of oxygen molecules in oxygen has been measured by high pressure ion drift tube. The ion drift tube equips a positive corona gap as a negative ion detector. It allows for the measurement under the atmospheric pressure. The ion drift space is varied from 1 to 9 cm using a micrometer attached on a feedthrough of the chamber. The observed mobility decreases against E/p0 and the tendency becomes remarkable in the shorter ion drift space. This would be caused by the field distortion effect near the mesh electrode. The electric field analysis is performed using a finite element method. It is found that field distortion is found by mesh electrode, separated the ion drift gap and the ion detecting gap. The mesh is changed in to new one of which diameter is 0.05mm. The obtained mobility can be improved and the reduced mobility μ0-=2.31±0.03cm2/V·s is obtained.
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  • Mamoru Takamatsu, Yoshio Nakashima, Sunao Fujii, Yukinori Saeki, Hiroy ...
    2005 Volume 125 Issue 2 Pages 187-188
    Published: 2005
    Released on J-STAGE: May 01, 2005
    JOURNAL FREE ACCESS
    Today, many goods are developed using the mental effect by the color. As a typical example, bath salts can be mentioned. In this study, the SD technique was used to quantitatively determine about how the color of solution influence the mental effect by 15 subjects. The results showed that effects by the red shades such as “warmth", and by the blue and purple shades such as “composedness", were high. Also, it clarified about the influence by the white muddiness.
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