Teruhiko Ida

National Defense Academy of Japan, Йокосука, Kanagawa, Japan

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Publications (6)1.88 Total impact

  • Source
    Teruhiko IDA · Toyohiko ISHIHARA · Keiji GOTO
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    ABSTRACT: Frequency-domain and time-domain novel uniform asymptotic solutions for the scattered fields by an impedance cylinder and a dielectric cylinder, with a radius of curvature sufficiently larger than the wavelength, are presented in this paper. The frequency-domain novel extended UTD and the modified UTD solutions, derived by retaining the higher-order terms in the integrals for the scattered fields, may be applied in the deep shadow region in which the conventional UTD solutions produce the substantial errors. The novel time-domain uniform asymptotic solutions are derived by applying the saddle point technique in evaluating the inverse Fourier transform. We have confirmed the accuracy and validity of the uniform asymptotic solutions both in the frequency-domain and in the time-domain by comparing those solutions with the reference solutions calculated from the eigenfunction expansion (frequency-domain) and from the hybrid eigenfunction expansion and fast Fourier transform (FFT) method (time-domain).
    Preview · Article · Nov 2005 · IEICE Transactions on Electronics
  • Source
    T. Ida · K. Goto · T. Ishihara
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    ABSTRACT: We have derived the uniform time-domain asymptotic solutions for the scattered fields by a dielectric cylinder and an impedance cylinder. By comparing with the reference solution obtained numerically, we have confirmed the accuracy and validity of the proposed time-domain asymptotic solutions.
    Preview · Conference Paper · Aug 2005
  • T. Ida · T. Ishihara
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    ABSTRACT: We derive a novel uniform asymptotic solution (extended UTD solution) for the field scattered by a dielectric circular cylinder. The extended UTD solution, derived by applying higher-order asymptotic formulas for the cylindrical functions, can be applied in the wide area extending from the illuminated region to the deep shadow region where the current UTD becomes increasingly inaccurate with the increasing frequency and azimuthal distance. We also derive the modified UTD solution from the new extended Pekeris carot function by applying the residue theorem. The modified UTD solution is the improved version of the current GTD and the UTD, and can be applied uniformly from the transition region in the illuminated region to the deep shadow region, including the region near the cylinder where the UTD deviates substantially from the eigenfunction solution. Comparisons with the exact solution calculated from the eigenfunction expansion confirm the validity and the utility of the extended UTD solution and the modified UTD solution.
    No preview · Conference Paper · Jul 2004
  • Teruhiko Ida · Toyohiko Ishihara
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    ABSTRACT: Studies on the scattering of electromagnetic fields by a dielectric cylinder have been an important research subject for a variety of applications in the area of antennas and propagation. In this study, a time-domain asymptotic analysis is discussed for the scattered electromagnetic fields when the cylindrical wave radiated from a magnetic line source is incident on a dielectric cylinder. We assume the Gaussian-type modulated pulse source whose spectrum is distributed in the high-frequency domain. The time-domain scattered field solutions derived in this paper are applicable in the transition regions near the geometrical boundaries, produced by the incident ray on the dielectric cylinder from the tangential direction, and near the caustics, produced by the family of the reflected ray group on the concave side of the dielectric cylinder. Comparisons of the time-domain asymptotic solution with the reference solution calculated numerically from a combination of the eigenfunction representation and the First Fourier Transform (FFT) code confirm the validity and the utility of the proposed time-domain asymptotic solution.
    No preview · Article · Jan 2003 · AP-S International Symposium (Digest) (IEEE Antennas and Propagation Society)
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    ABSTRACT: Domain structures on (001) plates of PZN-9%PT and PMN-32%PT were visualized by piezoresponse force microscopy (PFM) at various sample temperatures ranging from 25°C to 200°C. Zebra pattern domain structures were observed on both relaxors at various temperatures ranging from 25°C to the Curie temperatures and above. It was found that these domain boundaries did not move at these temperatures excluding the case of domain switching by PFM modulation voltage.
    No preview · Article · Jan 2002 · Ferroelectrics
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    ABSTRACT: Four kinds of domain structures (180° c-c, 180° a-a, 90° a-a and 90° a-c domains) on grown surfaces of PbTiO3 single crystals were imaged successfully using vertical and lateral piezoresponse force microscopy (PFM). Domain orientations (i.e., polarization vector distributions) at the surface of each domain structure are presented. These domain images are compared with simultaneously observed surface topographic images decorated by an acid etching treatment.
    No preview · Article · Sep 2001 · Japanese Journal of Applied Physics