• The Journal of the Acoustical Society of Korea
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• v.28 no.2E
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• pp.51-59
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• 2009

Mutual radiation impedance becomes more important in the design and analysis of acoustic transducers for higher power, better beam pattern, and wider bandwidth at low frequency sonar systems. This review paper focused on literature survey about the researches of mutual radiation impedance in the acoustic transducer arrays over 60 years. The papers of mutual radiation impedance were summarized in terms of transducer array structures on various baffle geometries such as planar, cylindrical, spherical, conformal, spheroidal, and elliptic cylindrical arrays. Then the computation schemes of solving conventional quadruple integral in the definition of mutual radiation impedance were surveyed including spatial convolution method, which reduces the quadruple integral to a double integral for efficient computation.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.446-450
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• 2005

We have built a spherically focused, not using acoustic mirrors, capacitive micromachined air-coupled ultrasonic transducer. A flexible backplate of a copper/polyimide backplate is used, permitting it to conform to a spherically shaped substrate. The backplate is patterned with $40-{\mu}m$ depressions having $80-{\mu}m$ center-to-center spacing. A $6-{\mu}m$ thick aluminized Mylar film completing the transducer is deformed to allow it to conform to the spherical backplate. The device's frequency spectrum is centered at 805kHz with -6dB points at 440 and 1210kHz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.2
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• pp.157-163
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• 2004

Optimal transducer positions are important as much as the control algorithms and hardware performance in the active noise control system. This study is similar to the past researches on the optimal transducer locations but with a far field noise source having a plane wave characteristic and the noise coming through an opening such as a window in an enclosure. Optimization techniques are used to find sets of optimal loudspeaker positions from a larger possible loudspeaker positions. Loudspeakers are placed on the surface of opening at the wall and inside of the enclosure. Using the measured acoustic transfer impedances and numerical simulations with the optimization technique, optimal positions are identified and compared. When a small number of loudspeakers are used. loudspeaker positions on the opening near the center seems to be the best place, but when a larger number of loudspeakers are used it was difficult to find simple patterns in the optimal positions. With the optimally positioned loudspeakers, optimal microphone positions are also studied.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.1
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• pp.80-87
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• 1998

In this study, a multi-element ultrasound transducer has been developed aiming at basic experiment of three-dimension endovascular ultrasound endscopy for clinical diagnos, and experimental results of two-dimensional object imaging in the water are presented by the ultrasound tranducer and neural network. Each ultrasound echo received by thirty-six angular transducer elements is inputed to the eural network, and then backpropagation is used as a learning algorithm. A three-layer artificial neural network is used for learning and imaging of targetw placed in front of the transducer. The object shape of imaging is restricted to rectangular shapes by considering experimental restraint conditions. As a result, rough visualization can be realized even for objects with unlearned shapes through the training by primitive patterns of a various sized rectangular targets.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.6
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• pp.17-23
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• 1980

The transmission and reception characteristics of surface acoustic wave devices are analyzed by introducing three different types of transducers. such as single-electrode transducer. double-electrode transducer and triple-electrode transducer. Utilizing an electromagletic field theory technique, the output signal has been derived theoretically. The basic analysis used here can be extended for other configurations. The surface acoustic devices have been shown promising as a means of improving the operation efficiency by modifying the Beometric configuration of transducer strips.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.98-104
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• 2001

Recently, the researches on the prevention of marine oil pollution being strengthened. Sludge oils were unavoidably produced in ship's operations, therefore it is necessary to manage the sludge oils inside the ship itself with the view to prevent marine oil pollution from ship. The present study deals with the ultrasonic breaking systems that recycle the sludge oil from ships into usable oil to be burnt. At the first instanceexperimental studies were carried out to investigate the homogenizing effect of the marine oils and the erosion aspect of horn disc by repeated vibration of ultrasonic transducer. The erosion damages for horn disc SS41 steel with weight loss rate and the irradiation time to max. erosion rate were examined according to the variation of the transducer amplitude, the oil temperature and the immersing depth of horn disc. As the result of it, the erosion aspects of horn disk were varied with oil environments and testing time.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.2
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• pp.67-73
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• 2003

In this paper, the impedance of a piezoelectric transducer is calculated using the three-dimensional finite element method. The validity of numerical routine is confirmed experimentally. Using this numerical routine, the effects of material coefficients on piezoelectric actuators characteristics are analyzed. The material constants, which make significant effects, are selected and the relations between material constants are studied. Using these processes, three variables of material constants for a piezoelectric transducer are selected and the design sensitivity method is adopted as an inversion scheme. The validity of the inversion scheme for a piezoelectric transducer is confirmed by applying the proposed method to the sample piezoelectric transducer.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1142-1144
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• 1999

A 4-beam cross type silicon elastic body was fabricated for the electromagnetic type vibration micro transducer. To improve energy transfer efficiency, the structure and size of vibration transducer were optimized by the FEA simulation package. Experimental results of the fabricated transducer shows $0.5{\sim}8$ dyne of vibration force at the condition of $1{\sim}4$ mA of current source $100{\sim}7000$ Hz of frequency band width. These results presented the useful applications for micro actuators and sensors.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1157-1159
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• 1999

A new method was developed to fabricate 1-3 piezo composite, a part of ultrasonic transducer. PZT rod arrays were made by pressing PZT green sheet with LIGA mold, and were sintered. Its dielectric constant and electro-mechanical coupling coefficient showed 4000 and 55% at 1kHz, respectively. So, PZT rod arrays made by means of this process can be applied to ultrasonic transducer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.301-312
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• 2009

This paper presents a theoretical approach to calculate the resonant frequency of a thickness vibration mode in the radial direction for a 1-3 piezoelectric composite transducer of circular arch shape. For the composite transducer composed of a piezoelectric ceramic and a polymer, vibration parameters were derived according to the volume ratio of a ceramic, and a vibration characteristic equation was derived from the piezoelectric governing equations with adequate boundary conditions. The fundamental resonant frequencies were calculated numerically and verified by comparing them with those obtained from the finite element analysis and the experiment. The volume ratio and the thickness are more substantial than the curvature radius to determine the fundamental resonant characteristics, and the fundamental resonant frequency becomes higher for the larger volume ratio of the piezoelectric ceramic and for the smaller thickness.