• Journal of KSNVE
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• v.6 no.6
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• pp.749-754
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• 1996

In this paper, a design method of matching layers is presented for the sandwich type broad band underwater acoustic vibrators. The characteristic impedances of matching layers are determined to be matched to the characteristic impedance of head mass material. For the dynamic characteristic analysis of the sandwich type transducers, one dimensional FEM technique is also introduced. A test vibrator with the quarter wave matching layers has been designed to verify the proposed method. And the wide band characteristics of the input impedance and transmitting voltage response (TVR) are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.370.2-370
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• 2002

Magnetostrictive materials are used low-frequency sonar transmitter instead of piezoelectric materials. But it is difficult to analyze due to the nonlinearity and hysteresis of magnetostrictive materials. This paper deals with the program development based on finite element method to model the magnetostrictive tonpilz transducers and to analyze their acoustic characteristics. (omitted)

• The Journal of the Acoustical Society of Korea
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• v.17 no.6
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• pp.23-28
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• 1998

고분자 압전 필름인 PVDF를 이용하여 단일막과 이층막의 초음파 변환기를 제작하 여 임펄스 응답특성을 이론식에서 계산하여 실험적으로 확인하여 보았다. 또한 RF 펄스를 이용하여 초음파 변환기의 다층막에 따른 주파수 특성을 조사하였다. 그 결과 임펄스 응답 특성은 이론식과 잘 일치하였으며, 단일막의 변환기가 이층막에 비하여 지속시간이 짧은 펄 스를 나타내었다. RF펄스에 대한 주파수특성은 이층막의 변환기가 단일막에 비하여 광대역 의 특성을 나타냄을 알 수 있었다.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.61-66
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• 1989

Welding residual stress was measured by ultrasonic birefringence technique. Acoustoelastic constant was taken by averaging the values in the literature. The initial birefringence from prefered orientation of grains was measured. The EMAT transducers were used to remove couplant effect. The results show that the distribution and magnitude of welding residual stress from ultrasonic measurement are in good agreements with those from semi destructive hole drilling measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.194-195
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• 2012

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.40-44
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• 1998

This paper describes variable speed drive and power control of a doubly fed induction machine(DFIM) for wind energy generation without rotational transducers. A stator flux orientation scheme and rotor speed estimator are employed to achieve decouple control of active and reactive power. To verify the theoretical analysis, a 5-hp DFIM prototype system and PWM power converter are built. Results of computer simulation are presented to support the discussion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1012-1016
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• 1996

This paper presents an automatic calibration technique for piezoelectic low pressure transducer, which is useful to measure a pressure within 500 psi. This system with automatic calibration function and error correction algorithm generates standard dynamic pressure for the calibration of sensor. With the compensation for the offset voltage and the pressure error, the accuracy and the usefulness of the proposed scheme is validated.

• The Journal of the Acoustical Society of Korea
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• v.4 no.3
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• pp.16-20
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• 1985

압전형 초음파 변환자의 특성을 압전체, matching layer, backing, 매질, tuning 및 구동 회로를 고려하여 해석하였다. 압전체는 KLM 모델을 이용하였고, 모델변수를 실험적으로 추정하여 시뮬레이션 에 대입하였다. 실험적인 RTIL은 면반사에 대한 pulse-echo를 측정하여 계산하였으며, 이론치와 비교할 때 20 dB 주파수 대역내에서 3 dB 이하의 오차가 관찰되었다.

• The Journal of the Acoustical Society of Korea
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• v.12 no.1E
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• pp.48-55
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• 1993

초음파 탐촉자의 개발에 필요한 압전재료의 선택을 위하여 탐촉자의 성능에 영향을 미치는 탄성, 유전, 압전 상수의 영향을 알아보았다. 해석 방법으로는 등가회로를 통한 두께 모드 발신기, 수신기, 펄스 반사기의 전달함수를 구하였으며, 이로부터 압전재료의 각 물성치가 가져야 할 바람직한 특성을 제시하였다. 본 연구의 결과는 재료의 선택시와 더불어 세라믹 공학자들이 초음파용 압전소자를 개발함에 있어 적절한 지침이 될 수 있을 것이다.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2443-2445
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• 2000

In this paper, the Intergrated SCADA is used to computer systems designed to perform the following functions for power plant. - to collect data from industrial plant devices or transducers - to process and perform calculations on the collected data - to present collected and derived data on displays on MMI - to accept commands entered by human operators and act on them such as sending control commands to plant devices. This system is characterised by open architectured that is based on the internationally recognized industrial standard for industrial automation control language, the IEC 1131-3