• Journal of KSNVE
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• v.6 no.1
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• pp.65-70
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• 1996

The sensor response of a piezoelectric transducer embedded in a fluid loaded structure is modeled using a hybrid numerical approach. The structure is excited by an obliquely incident acoustic wave. Finite element modeling in the structure and fluid surrounding the transducer region, is used and a plane wave representation is exploited to match the displacement field at the mathematical boundary. On this boundary, continuity of field derivatives is enforced by using a penalty factor and to further achieve transparency at the mathematical boundary, drilling degrees of freedom (d.o.f.) are introduced to ensure continuity of all derivatives. Numerical results are presented for the sensor response and it is found that the sensor at that location is not only non-intrusive but also sensitive to the characteristic of the structure.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.125-132
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• 2006

This paper presents the feasibility of a lateral mode piezoelectric oscillator to detect damages in civil infrastructures. The lateral mode oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric lateral mode vibrator to be attached to a structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of a resonant frequency of the structure. The oscillator sensors can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified in this work with a sample aluminum plate where artificial cracks of different lengths and number were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of a plate with cracks.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1423-1424
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• 2015

본 연구는 IoT 환경에서 수면 중 비정상호흡 모니터링을 위한 모듈개발 사전연구로, 베개 안에 삽입할 수 있는 가속도, 진동 측정 모듈을 제작하고, 측정된 신호를 기반으로 수면 중 발생하는 호흡활동을 관찰하는 것을 목적으로 한다. 이를 위하여 압전센서 및 3축 가속도 센서를 내장한 진동, 가속도 측정 모듈 프로토타입을 설계 및 제작하였으며, 파일럿 실험을 통하여 개발된 모듈의 동작을 확인하였다. 실험 결과 가속도 및 압전센서에서 획득된 신호에서 호흡성분이 검출되는 것을 확인하였으나, 샘플링율, 센서 민감도 설정에 따라 코골이 성분은 검출되지 않았다.

• Electrical & Electronic Materials
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• v.1 no.4
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• pp.311-318
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• 1988

초음파센서(수신기)에 응용가능한 압전세라믹스를 제조하기 위하여 Ba변조된 Pb(ZR, Ti)O$_{3}$계 세라믹스에 MnO$_{2}$를 첨가하여 첨가량과 소성온도에 따른 영향을 조사하였다. 또한 제조된 압전세라믹스를 이용하여 초음파 수신기를 제작하여 수신특성을 확인하여 보았다. 그 겨로가 MnO$_{2}$가 0.4(wt%)첨가되었을 때 압전 g정수가 가장 크고 수신감도가 우수한 것으로 밝혀졌다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.311-314
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• 2011

최근 콘크리트 구조물의 안전성강화를 위해 탄소섬유 강화 플라스틱(CFRP) 보강 공법이 널리 사용되고 있지만 잘 알려진 바와 같이 CFRP 보강재와 콘크리트 표면사이의 부착면 탈락은 보강재 자체의 손상보다 발생할 확률이 높고 이러한 부착면 탈락은 보강의 효과를 무의미하게 만들기 때문에 구조물 전체의 파괴로 직결될 수 있다. 이에 본 연구에서는 CFRP 부착면 탈락손상을 실시간으로 검색하기 위해 압전센서를 사용하는 구조물 건전성 평가 기술을 적용하였다. 이의 검증을 위해 CFRP로 보강된 콘크리트 보를 제작하였고 3단계로 증가하는 부착면 탈락 손상을 발생시켰다. 손상 증가 단계마다 CFRP 표면에 배열된 압전센서로부터 임피던스와 유도초음파 신호를 계측하였고 손상에 따른 신호변화를 정량화하기 위해 손상지수인 RMSD를 계산하였다. 더 구체적인 부착면 탈락 손상위치 탐색을 위해서 두 가지 계측 기법으로부터 구해진 RMSD 값를 중첩시키는 Superposed RMSD 가 제안되었다. 구해진 Superposed RMSD 값을 사용하여 커브 피팅이 수행되었고 도출된 커브의 최고값에 해당하는 위치값을 찾아 실제 손상위치와 비교함으로써 제안된 기법의 가능성을 검증해 보았다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.151-157
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• 2018

Among the various sensors for measuring traffic, PVDF (polyvinylidene fluoride) piezoelectric sensors are used to classify vehicles because they can detect the axle of the vehicle. Piezoelectric sensors are embedded in road pavements and are always exposed to traffic loads and environmental loads. Therefore, the life expectancy is very short, less than 6 years. Traffic control is essential for reinstallation and data collection is interrupted during the failure period. The lifespan will increase if the sensor installation depth is increased. In this study, the sensor signal output was analyzed with a variable depth of sensor installation to verify the possibility of deeper installation. Furthermore, various parameters, such as the weight and speed, were analyzed. The wheel load is applied using APT. As a result, the MSI BL sensor output signal is higher than 100mV when installed at 3cm, which is reliable. If the location of the sensor is deeper in the pavement, the expected lifetime of the sensor is also increased. On the other hand, the MSI cable was found to be less than 100mV at the shallowest depth of 1cm, making it impossible for field applications.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.4 s.310
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• pp.30-34
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• 2006

To enhance the performance of the piezoelectric transducer for the transit-time type ultrasonic sensors, we investigated and verified the effect of it's size and raw materials using FEM(Finite Element Method) technique. Radiation angle of $25^{\circ}$ could be realized through the control of the matching layer's shape and its raw materials. Based on the results, the flowmeter is fabricated and characterized in real application, which thereby proves good sensitivity of 10 times better than current commercial one.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.108-116
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• 2015

An acoustic vector sensor is a device that is capable of measuring the direction of wave propagation and the acoustic pressure. In this paper, the modeling of micro-cantilever sensor for the vector sensor are proposed by consideration of acoustic phenomenon in water. Two models based on unimorph structure are proposed in this paper and corresponding transfer function which describes the relation between input pressure wave and output voltage depending on incidence angle and frequency of pressure wave is derived based on lumped model. It has been shown that very thin and flexible micro-cantilever can be used to measure directly the particle velocity component in water.

• Electrical & Electronic Materials
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• v.17 no.1
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• pp.10-16
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• 2004

• The Journal of the Acoustical Society of Korea
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• v.16 no.6
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• pp.61-67
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• 1997

Piezoelectric gyroscopes are the devices to measure angular rotational velocity of a system with respect to an inertial frame of reference means of the Coriolis principle. Most of current piezoelectric gyroscopes detect rotational velocity about a single axis of rotation. This paper describes development of a new dual axial gyroscope made out of the piezoelectric ceramic, PZT, which can overcome the limitation of the current single axial type. The validity of the new structure is checked through finite element analysis. Based on the design, an experimental sample of the sensor is fabricated and its performance is discussed in comparison with the theoretical expectation. The resutls show that the present gyroscope is capable of measuring the rotational velocity over two orthogonal axes simultaneously with good enough sensitivity and distinction between the two axial components of the rotation.