• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.376-380
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• 2009

Surface acoustic wave (SAW) device is widely used as a bandpass filter, a chemical or physical sensor, and an actuator. In this paper, we propose the capacitive gap measurement system with high precision through the signal processing using SAW device. The research process is mainly composed of theoretical part and experimental part. In theoretical part, equivalent circuit model was used to simulate the SAW response by the change of capacitance. In experimental part, commercialized capacitor was used to see the SAW response by the change of load capacitance. After that, gap adjustment system was made physically and the SAW response by the change of gap which caused the capacitance change was measured. And resolution and stroke was decided comparing the signal change and basic measurement noise level.

• 센서학회지
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• 제17권4호
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• pp.289-294
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• 2008

The purpose of this study is to materialize the viscosity sensor by using the SH-SAW sensor of which the center frequency is operated at higher than 50 MHz. In order to measure the viscosity, SAW sensor of which the center frequency is operated at 100 MHz is developed. By using the developed sensor, phase shift, delay time, insertion loss, and frequency variation are measured at different viscosity. The result shows that the phase shift difference between the viscosity variations is such that the difference between the distilled water and the 100 % glycerol solution is approximately $45^{\circ}$, the change of the insertion loss is approximately 9 dB, and the difference of frequency variation is approximately 5.9 MHz. Therefore, it is shown that viscosity of unknown solution can be measured with the surface acoustic wave sensor.

• 전기학회논문지
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• 제62권12호
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• pp.1730-1736
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• 2013

Slanted and chirp interdigital transducer(IDT) configurations were studied for generating the surface acoustic wave(SAW) with wide bandwidths on a piezoelectric substrate. These devices can be applied to manipulate optical path of light along the waveguide, ultimately used for optical switches and holographic image implementation. Prior to fabrication, the coupling of modes(COM) modeling and simulation were performed to extract optimal design parameters. The optimally designed wideband device showed wide bandwidth of 30MHz, low insertion loss of -25dB, and abrupt side suppression ratio (SSR). Several design conditions were determined during device implementation, such as slanted angle, aperture length, number of fingers, and central frequencies of IDTs. These factors were experimentally analyzed and described in details in this paper.

• 센서학회지
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• 제8권2호
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• pp.108-114
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• 1999

표면 탄성파 가스센서는 소자의 크기가 작고, 값이 싸며, 가스에 대한 감도가 매우 높고 소자의 신뢰도가 높은 장점을 갖고 있다. 본 연구에서는, $LiTaO_3$ 단결정 압전기판 위에 이중지연선을 갖는 표면 탄성파 $NO_2$ 가스센서를 설계 및 제작하였다. 제조된 IDT의 커패시턴스는 79.3MHz의 주파수에서 326.34pF였다. 임피던스 매칭이 된 IDT의 반사손실은 79.3MHz의 주파수에서 최대인 -16.74dB로 나타났다. SAW 발진기를 성하여 고주파증폭기의 이득을 적절히 조정함으로써 안정된 발진이 이루어짐을 확인하였다. SAW 발진기의 $NO_2$ 가스에 대한 발진주파수의 변이는 28Hz/ppm으로 나타났다.

• 한국재료학회지
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• 제11권6호
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• pp.477-482
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• 2001

쐐기형 전극 사이에 열처리전 비정질 ($Fe_{1-x}$ $Co_{x}$ )$_{89}$ $Zr_{ 11}$ (x=0~1.0) 자성막이 증착된 MSAW 소자를 구성하고 외부 인가자기장에 의한 MSAW 속도변화율을 조사하였다. 그 결과 MSAW 속도변화율은 직류 인가자기장, 구동주파수, 자성막의 두께 및 조성에 민감하게 의존하였으며, 특히 구동주파수 및 자성막의 두께가 증가할수록 증가함을 확인하였다. 열처리전 시편에서 나타난 최대 속도변화율은 x=0.8에서 얻어진 0.062%였다.

• 한국음향학회지
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• 제20권1호
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• pp.68-76
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• 2001

유한요소법을 이용하여 압전 수중음향센서의 모델링 및 음향특성을 해석하였다. 압전 수중음향센서의 해석에서 기본적인 압전-탄성 구조물과 유체-구조물의 연성해석을 위한 유한요소 정식화를 하였으며 무한영역의 음향유체를 처리하기 위하여 IWEE (Infinite Wave Envelop Element)를 도입하였다. Tonpilz형 수중음향센서를 수중 산란체로 볼 경우 입사파가 산란체의 표면을 가진할 때 산란체로부터 발생되는 산란파는 IWEE로 인하여 무한 유체영역에서의 산란파의 감소특성을 갖게 되어 무한영역을 유한영역으로 나눈 인위적인 경계에서 반사가 일어나지 않게 되므로 산란파의 음압을 정확히 구할 수 있었다. 또한, 이러한 산란해석을 바탕으로 입사파에 대한 음향센서 내부의 전기적 응답특성인 RVS (Receiving Voltage Signal)를 구하였다. 이러한 일련의 연구 과정들은 소나 시스템을 정확히 해석하고 음향특성을 예측하는데 큰 도움이 될 것이다.

• 한국가스학회지
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• 제4권1호
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• pp.55-62
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• 2000

Pit형 표면결함으로부터 발생하는 작은 피로균열의 거동을 초음파의 표면파를 이용하여 이를 위하여 피로시험중인 Al 2024-T3를 시험재료, 피로시험도중 초음파를 이용하여 피로균열의 거동을 조사하였다. 즉, 피로시험에서 균열이나 Pit로부터 발생하는 작은 피로균열을 여러 응력조건하에서 나타나는 표면파의 반사특성에 관하여 연구하였다. 또한 이론적 결과와 실험적 결과를 상호 비교, 분석하였고, SEM을 사용하여 이들 작은 피로균열을 관찰하였다. 초음파를 이용한 피로균열의 균열 개구 거동에 관한 연구에서 피로균열의 유효균열 특성을 초음파법으로 평가 할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1245-1246
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• 2015

광대역 표면 탄성파(Surface Acoustic Wave)를 이용하여 도파로 층의 빛을 특정 각도로 변조하여 편향 휴대용 홀로그램 디스플레이를 구현하기 위한 음향 광학(Acoustic-Optic) 장치를 개발했다. 개발된 시스템은 프리즘, 도파로층, 표면탄성파를 일으키는 IDT 및 스크린으로 구성된다. 도파로내에서 전파하는 빛은 표면탄성파에 에너지가 가해지지 않으면 도파로층의 진행중 경로 변화가 발생하지 않지만 표면 탄성파에 에너지를 가하면 빛의 편향된다. 큰 편향 각도와 고효율을 위해서 표면탄성파의 파워, 표면탄성파의 중심주파수, IDT aperture length, waveguide thickness 등을 조절하여 빛 편향각도 및 효율변화를 관찰하였다.

• 한국지진공학회논문집
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• 제19권6호
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• pp.257-263
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• 2015

Recently two seismic cloaking methods of earthquake engineering have been suggested. One is the seismic wave deflection method that makes the seismic wave bend away and the other is the shadow zone method that makes an area that seismic waves cannot pass through. It is called as seismic cloaking. The fundamental principles of the seismic cloaking by variable refractive index were explained. A two-dimensional cylindrical model which was composed of 40 layers of different density and modulus was tested by numerical simulation. The center region of the model to be protected is called 'cloaked area' and the outer region of it to deflect the incoming wave is called 'cloaking area' or 'cloak area.' As the incoming surface wave is approaching to the cloaking area, the refractive index is decreasing and, therefore, the velocity and impedance are increasing. Then, the wave bends away the cloaked area instead of passing it. Three cases are tested depending on the comparison between the seismic wavelength and the diameter of the cloaked region. The advantage and disadvantage of the method were compared with conventional earthquake engineering method. Some practical requirements for realization in fields were discussed.

• 천문학회지
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• 제24권2호
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• pp.129-149
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• 1991

An attempt has been made to examine the characteristics of acoustic and MHD waves generated in stellar convection zones($4000\;K\;{\leq}\;T_{eff}\;{\leq}\;7000\;K$, $3\;{\leq}\;\log\;g\;{\leq}\;4.5$). With the use of wave generation theories formulated for acoustic waves by Stein (1967), for MHD body waves by Musielak and Rosner (1987, 1988) and for MHD tube waves by Musielak et al.(l989a, 1989b), the energy fluxes are calculated and their dependence on effective temperature, surface gravity and megnetic field strength are analyzed by optimization techniques. In computing magneto-convection models, the effect of magnetic fields on the efficiency of convection has been taking into account by extrapolating it from Yun's sunspot models(1968; 1970). Our study shows that acoustic wave fluxes are dominant in F and G stars, while the MHD waves dominant in K and M stars, and that the MHD wave fluxes vary as $T_{eff}^4{\sim}T_{eff}^7$ in contrast to the acoustic fluxes, as $T_{eff}^{10}$. The gravity dependence, on the other hand, is found to be relatively weak; the acoustic wave fluxes ${\varpropto}\;g^{-0.5}$, the longitudinal tube wave fluxes ${\varpropto}\;g^{0.3}$ and the transverse tube wave fluxes ${\varpropto}\;g^{0.3}$. In the case of the MHD body waves their gravity dependence is found to be nearly negligible. Finally we assesed the computed energy fluxes by comparing them with the observed fluxes $F_{ob}$ of CIV(${\lambda}1549$) lines and soft X-rays for selected main sequence stars. When we scaled the corrected wave fluxes down to $F_{ob}$, it is found that these slopes are almost in line with each other.