• Journal of Institute of Control, Robotics and Systems
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• v.2 no.3
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• pp.194-199
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• 1996

평면 배열형 소나 센서에서는 트랜스듀서 상호간의 간섭효과들이 음을 방사하는 각각의 트랜스듀서 및 평면 배열의 빔패턴에 영향을 주게된다. 따라서 음향 방사출력의 계산은 소나용 트랜스듀서의 성능및 효율을 평가하는데 필수적이다. 음향 방사출력을 예측하기 위하여 무한 강성 배플에 고정된 수개의 트랜스듀서를 이론해석의 대상으로 설정하였다. 각 트랜스듀서는 자기방사 임피던스 및 상호방사 임피던스로 구성되어 있으며 이것의 총 방사 임피던스 및 음향반사 출력의 추출은 등가 전기회로 모델을 이용하였다. 이론및 수치해석의 결과에 근거하여 음향방사 출력은 각 트랜스듀서 상호간의 간섭의 양에 의존함을 보였으며 상호간섭에 의한 음향출력 손실은 25.05%에서 최고 51.52%정도임을 확인하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.56-62
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• 1990

Surface Acoustic Waves(SAW) are generated on silicon wafer and $YZ-LiTaO_3$ substrate and are detected by noncontact method. As wave sources two kinds of transducers are used : the wedge-type of 20.0 MHz and fabricated Interdigital Transducer(IDT) of 20.8 MHz. SAW are modulated by the optical chopper frequency and are syncronized with a laser beam. In signal processing, intensity variations of light due to the intensity of SAW are analyzed using lock- in amplifier. From the results, corresponding to the applied input power, the intensity variations of a deflected light by corrugations on the substrates are increased and saturation phenomenon is observed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.79-83
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• 2014

In this paper, SAW devices are fabricated using various IDT shape(Single/Double) to check an effect of the IDT on SAW device. And based on theory of a particle velocity moved by SAW and IDT, a particle velocity is measured and calculated. Depend on insert power, a particle velocity using Single-IDT SAW device is about two times bigger than Double-IDT SAW device and it's almost same with a theoretical different.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.8-15
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• 2006

Guided-waves-based mortar-filled steel pipe inspection is carried out through using EMAT (Electro magnetic acoustic transducer) and wavelet transform. Possibly existing anomalies such as separation (or void) and inclusion are made in the fabricated mortar-fled steel pipes: these anomalies are infected. Since guided waves have the long range inspection capability, EMAT has its own advantages over the conventional PZT (Piezoelectric zirconate titanate), and wavelet transform gives the multi-resolution on time-frequency domain results, the suggested technique gives an alternative way for inspecting mortar-filled steel pipes, which are popularly used for supporting marine structures such as piers, wharfs, moles, and dolphins. Through this study, it is show that the suggested technique is promising for detecting the amounts of separations and inclusions.

• The Journal of Information Technology
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• v.5 no.2
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• pp.69-80
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• 2002

Conventionally, we have used an acoustic microscope at single operating frequency. The resolution and quality of the measured images are determined by transducer of the microscope. In this paper, we have studied Vertical Resolution Enhancement with Acoustic Reflection Microscope using combining bases of support for SFR(Spatial Frequency Response). Increased Vertical resolution can be obtained by taking three-dimensional images at more that one frequency and numerically combining the results. As results of the experiment, we could get enhanced images with the rate of contrast in proportion to the changing rate of depth.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.947-952
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• 2001

In this paper, a wideband SAW convolver using a parabolic horn waveguide was designed and its characteristics were investigated. The convolver was made with parabolic horn waveguide at compression ratio 9:1 for reducing propagation loss and for improving convolution efficiency between two input IDTs of center frequency 193.78 ㎒. The SAW convolver utilizing acoustic nonlinearities of piezoelectric material demonstrated that it can provide large S/N ratio and can be use for programmable matched filter(PMF) in spread spectrum communication system.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.2
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• pp.195-206
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• 2022

The separation of spectrally overlapped broadband echo signals from free-swimming Japanese needlefish Hypohamphus sajori using the fractional Fourier transform (FrFT) was investigated. The broadband echo signals were measured over frequency ranges of 40-80 and 110-220 kHz. The overlapped echo signals were separated after eliminating noise signals in the smoothed pseudo-Wigner-Ville distribution domain. The echo signal from a 40 mm WC sphere suspended just below a chirp transducer was used to calibrate the broadband of the chirp echo sounder and estimate the frequency dependence of target strength for the separated echo signals. The experimental results show that the proposed FrFT method can analyze the time-frequency image of broadband echo signals from free-swimming individual fish effectively and can be used as a quantitative tool for extracting the acoustic features used for fish species identification.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.361-368
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• 2010

ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.97-108
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• 2011

Systems for underwater environment monitoring and natural resources can be considered as a part of digital convergence where real-time data transmission is possible with the help of underwater wireless sensor network (UWSN). One of key technologies required for the deployment of the systems is underwater acoustic micro modem. In this work, we design and implement an acoustic modem equipped with a commercial omnidirectional transducer. We also make experiments at the northern Han river for the verification of the developed modem. According to the experiments, the modem supports the working distance of 250 m and the data rate of 200 bps with a negligible bit error rate. It is expected that the acoustic modem can be used for various applications based on UWSN in a near future.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.467-475
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• 2019

A high-intensity ultrasound wave generates acoustic streaming and acoustic radiation forces when propagating through a medium. An acoustic radiation force generated in a three-dimensional space can produce a solid tactile sensation, delivering spatial information directly to the human skin. We placed 154 ultrasound transmit elements with a frequency of 40 kHz on a concave circular dish, and generated an acoustic radiation force at the focal point by transmitting the ultrasound wave. To feel the tactile sensation better, the transmit elements were excited by sine waves whose amplitude was modulated by a 60 Hz square wave. As an application of ultrasonic tactile sensing, a region where tactile sense is formed in the air is used as an indicator for the position of the hand. We confirmed the utility of ultrasonic tactile feedback by implementing a system that provides the number of fingers to a machine by receiving the shape of the hand at the focal point where the tactile sense is detected.