Yoshihiro Michiguchi

Development of Signal Processing Methods for Imaging Buned Pipes

A new imaging technique for subsurface radars is described for reconstructing clear images of buried pipes in soil. The method developed has two signal processing stages; preprocessing and aperture synthesis. The preprocessing extracts signals scattered from the pipes by reducing clutter noise. The synthetic-aperture processing analyzes only the scattered signals derived by the first stage and reconstructs high-quality images in a short processing time. The imaging technique developed was successfully applied to the imaging of actual buried metallic pipes. It was experimentally confirmed that the new imaging method was capable of reconstructing clear images in a short time without losing image quality.

Advanced subsurface radar system for imaging buried pipes

A subsurface radar system for imaging buried pipes was developed. The system is capable of reconstructing clear pipe images under unfavorable conditions, such as large attenuation rate of the radio waves propagating in soil. The output power of a pulse generator, the amplifier gain, and average number are controlled by moving the observation depth to improve the detection capability. Fast image processing methods are also used. A 6.5-cm-diameter steel pipe, buried at a depth of 2.5 m, was clearly reconstructed as a color image averaged attenuation rate of 12.6 dB/m in the soil. A plastic pipe (6.5 cm in diameter), buried at a depth of 1 m, was also imaged by the system. >

Unknown sound evaluating method and apparatus

Method and apparatus for evaluating location of an unknown sound generated in a structure such as a pressure vessel. A plurality of sound detectors are mounted on the structure for detecting sounds generated in the structure. On the basis of sound information of the unknown sound source derived from the outputs of the detectors, the location where the unknown sound is produced is determined. To this end, reference sounds are first generated at a plurality of known reference sound source positions, wherein information of the reference sounds derived from the outputs of the detectors are stored in a storage unit. Equi-pattern-distance curves each of which is in an equal pattern distance between a supposed unknown sound source and each of the reference sound sources are calculated on the basis of the reference sound information. The equi-pattern-distance curves are further corrected in accordance with the reference sound information. Upon occurrence of an unknown sound, pattern distances between the desired reference sound source positions and the unknown sound source position are calculated through pattern recognition procedure from the sound information derived from the outputs of the detector and the reference sound information stored. On the basis of the calculated pattern distances and the equi-pattern-distance curves, the position of the unknown sound source is determined. On the basis of the position of the unknown sound source, kinetic energy thereof may be arithmetically determined.

Development of a Collector Ring Monitor for Sparking Detection on Generators

Continuous monitoring techniques are described for sparking detection of collector rings on generators.

Methods of metallic loose parts location and impact energy estimation from information on reference impact sounds

Abstract Reference impacts were employed to achieve accurate location and energy estimation of metallic loose parts in inhomogeneous systems such as nuclear reactor vessels. Impact positions are determined using distances from reference impacts and pattern recognition technique. To confirm the method, experiments were carried out using a cylindrical steel tank (diameter = 2m, height = 5m, thickness = 2m). The reference impacts were arranged on lattice points, separated by 1 meter, on the tank wall. The signal amplitudes of various impacts positions with a uniform impact energy and the same propagation path length exhibited deviations of around one order of magnitude. This fact would seem to limit the posibility of achieving accurate location and energy estimations from the amplitude data. However, the results were surprisingly good. Using amplitude data, the impact positions on the tank were located within an error of 13cm and impact energies were estimated within an error of 25%.

Application of Shear Wave Focused Image Holography to Nondestructive Testing

This paper describes a method for sizing vertical and oblique flaws or defects within metal structures be the use of scanned acoustical holographic interferometry in the focused image hologram mode. The image of an internal flaw obtained from focused image holography consists of interference fringes or contour lines across the flaw’s surface. The fringe separation represents half wavelength deviations in depth from the scanning plane and the length of the fringes corresponds to the width of the flaw. Thus, it is possible to evaluate flaw size by measuring the number and length of fringes appearing on the focused image hologram.