• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.83-90
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• 1999

In this paper, we studied resolution to the FBP and BFP image reconstruction algorithms for ultrasonic diffraction tomography. In order to analyze the resolution to the tomographic images which can be reconstructed from the modified FBP image reconstruction algorithm by using fixed coordinate system and BFP image reconstruction algorithm which is suitable for plane structure object, we derived ambiguity functions to these algorithms and then analyzed lateral and depth resolution through simulation respectively. Simulation results show that the lateral and depth resolution to the FBP image reconstruction algorithm and the BFP image reconstruction algorithm was determined 0.27 λ, 0.70 λ and 0.39 λ, 0.98 λ at the 3dB respectively. These results imply that modified FBP and BFP image reconstruction algorithms for diffraction tomography is useful in the tomographic image reconstruction.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.5
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• pp.107-116
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• 1992

Recently, it is gradually raised necessity that interface is measured accurately and managed in industrial circle and medical world. An Ultrasonic wave transmitted from a focused beam tranducer is being expected as a powerful tool for NDE of the delamination. The Ultrasonic NDE of the delamination is based on the form of the wave reflected from the interface. In this study results, automatically repeated discrimination analysis method can be devided in the category of all kinds of defects on semiconductor package, and also can be possible to have a sampling of partial delamination.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.43-49
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• 1990

Ultrasonic testing is one of the most useful NDT method for detection of microdefect in the opaque materials. Recently, many applications of the ultrasonic techniques have been extended widely in the new field like electron is and advanced materials. From the result of the experiment, we have hardly found out a crack in the internal parts of the resin and a delamination between chip and resin because of poor performance of the system.

• Journal of Industrial Technology
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• v.8
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• pp.65-70
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• 1988

The intensity of ultrasound in liquid is calculated by improved analytic method. Helmholtz equation or Rayleigh's proposition does not offer the analytic solution. Considering a bounded medium, the use of the image source method in electromagnetic thoery gives a new way of calculating the total ultrasonic intensity in liquid. Some methods of measuring the intensities are also mentioned.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.696-704
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• 2011

In this paper, we propose a mobile robot navigation algorithm using data fusion of a monocular camera and ultrasonic sensors. Threshold values for binary image processing are generated by a fuzzy inference method using image data and data of ultrasonic sensors. Threshold value variations improve obstacle detection for mobile robot to move to the goal under poor illumination environments. Obstacles detected by data fusion of camera and ultrasonic sensors are expressed on the grid map and avoided using the circular planning algorithm. The performance of the proposed method is evaluated by experiments on the Pioneer 2-DX mobile robot in the indoor room with poor lights and a narrow corridor.

• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.78-89
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• 2005

An experimental study was carried out to investigate the effect of local ultrasonic forcing on a turbulent boundary layer. Stereoscopic particle image velocimetry (SPIV) was used to probe the characteristics of the flow. A ultrasonic forcing system was made by adhering six ultrasonic transducers to the local flat plate. Cavitation which generates uncountable minute air-bubbles having fast wall normal velocity occurs when ultrasonic was projected into water. The SPIV results showed that the wall normal mean velocity is increased in a boundary layer dramatically and the streamwise mean velocity is reduced. The skin friction coefficient (C$_{f}$) decreases 60$\%$and gradually recovers at the downstream. The ultrasonic forcing reduces wall-region streamwise turbulent intensity, however, streamwise turbulent intensity is increased away from the wall. Wall-normal turbulent intensity is almost the same near the wall but it increases away from the wall. In the vicinity of the wall, Reynold shear stress, sweep strength and production of turbulent kinetic energy were decreased. This suggests that the streamwise vortical structures are lifted by ultrasonic forcing and then skin friction is reduced.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.564-572
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• 2012

Harmonic imaging is introduced in the present article and its principle and physical characteristics is described in contrast to conventional ultrasonic imaging. The principle of the conventional image which uses ultrasonic echoes reflected at the interfaces between tissues is presented, and the nonlinear ultrasonic propagation which results in harmonic components is conceptually described. The pulse inversion technique which effectively extracts the harmonic components from the ultrasonic echo signals is introduced, and the advantages of the constructed harmonic images are summarized comparing with those of conventional ultrasonic images. The harmonic images are classified according to the mechanism of harmonic production, and the typical harmonic images obtained from patients are presented in contrast to the corresponding sonograms. Clinical significance and prospects of harmonic imaging and the future research areas are discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.4
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• pp.315-320
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• 2015

This paper describes the implemenation of localization and visualization scheme to find out an ultrasonic source caused by defects of a power distribution line equipment. To increase the fault detection performance, $2{\times}4$ sensor array is configured with MEMS ultrasonic sensors, and from the sensor signals aquired, the azimuth and elevation angles of the ultrasonic source is estimated based on the delay-sum beam forming method. Also, to visualize the estimated location, it is marked on the background image. Experimental results show applicability of the present technique.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.60-65
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• 1998

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of Ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.747-752
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• 1998

Ultrasonic sensors have been widely used to recognize the working environment for a mobile robot. However, their intrinsic problems, such as specular reflection, wide beam angle, and slow propagation velocity, require an excessive number of sensors to be integrated for achieving the sensing goal. This paper proposes a new measurement scheme which uses only two sets of ultrasonic sensors to determine the location and the type of a target surface. By measuring the time difference between the returned signals from the target surface, which are generated by two transmitters with 1 ㎳ difference, it classifies the type and determines the size of the target surface. Since the proposed sensor system uses only two sets of ultrasonic sensors to recognize and localize the target surface, it significantly simplifies the sensing system and reduces the signal processing time so that the working environment can be recognized in real time.