• Geophysics and Geophysical Exploration
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• v.26 no.4
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• pp.229-237
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• 2023

The use of artificial sources such as explosives and mechanical vibrations for seismic exploration in urban areas poses challenges, as the vibrations and noise generated can lead to complaints. As an alternative to artificial sources, the surface waves generated by traffic noise can be used to investigate the subsurface properties of urban areas. However, traffic noise takes the form of plane waves moving continuously at a constant speed. To apply existing surface wave processing/inversion techniques to traffic noise, the recorded data need to be transformed into a virtual shot gather format using seismic interferometry. In this study, various seismic interferometry methods were applied to traffic noise data, and the optimal method was derived by comparing the results in the Radon and F-K domains. Additionally, the data acquired using various receiver arrays were processed using seismic interferometry, and the results were compared and analyzed to determine the most optimal receiver array direction for exploration.

• 전기의세계
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• v.31 no.2
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• pp.141-146
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• 1982

In this paper, surface acoustic wave (SAW) bandpass filter is designed using the Fourier series approach and the I$_{0}$-shin window function. And also we studied a method to realize SAW filter using the apodized ID transducer which was fabricated with aluminum metallization of about 1500 A over .deg. thickness on Y-cut Z-propagating LiNbO$_{3}$, crystal by photolithographic technique (lift-off method). Experimental results on SAW bandpass filter responses show good agreements with the theoretical characteristics.s.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.88-98
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• 1993

In this paper, the effective permittivity in the piezoelectric material is numerically obtained and greens function is derived from that. It is shown that the admittance and the transfer function of an interdigital transducer is represented by electrostatic charge distribution using Quasi-static approximation. To prove the validity of the quasi-static approximation, numerical results for the uniform IDT of a filter mounted on 128 $^{\circ}$ rotated Y-cut X-propagating Lithium Niobate are compared with the measured ones.

• The Journal of the Acoustical Society of Korea
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• v.3 no.2
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• pp.23-29
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• 1984

In this paper surface acoustic wave beam track changers using symmetric multistrip coupler are designed on the basis of the perturbation theory, and its characteristics are studied. SAW beam track changers, which have the configuratio of the periodic array of metal strips, are designed with the following specifications ; the number of strips : 140, the strip period: 0.25λ, the ratios of the strip width to the period a/p: 0.5, 0.375, 0.25, respectively, and approximately consistent with the theoretical values, and also the bulk wave mode and the 2nd-order effects are suppressed by these track changers.

• The Journal of the Acoustical Society of Korea
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• v.4 no.2
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• pp.48-55
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• 1985

포물선형 혼 도파관을 사용하여 입사파의 음향전력밀도를 증대시킴으로써 압전물질의 압전비선 형성을 이용한 평판형 구조의 탄성 음향파 콘벌버를 제작하고 스펙트럼 확산 통신방식에서 S/N 비가 S 높으며 프로그램이 가능한 자기상관정합 필터로 사용될 수있음을 실험적으로 제시하였다. 본 실험에서 는 포물선형 혼 도파관을 사용한 탄성 음향파 콘벌버를 압전 재료인 YZ-LiNbO\sub 3\ 위에 중심 주파 수 100MHz 압축비 11:1, 적분시간 6인 IDT, 포물선형 혼 도파관 및 출력단자를 설계한 후 이를 포토리 토그라피 바업으로 제작하여 100 MHz 로 펄스 변조된 신호를 탄성 음향파 콘벌버의 양 입력에 인가하 여 자기상관 출력을 얻음으로써 신호 처리 이득이 18dB인 정합필터를 구현하였다.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.166-171
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• 2006

In this study, in using a piezoelectric material of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ (PMN-PT), which has a high electromechanical coupling coefficient, we have tried to study about this material can be practically available as a new biosensor to detect protein by using surface acoustic wave (SAW). As the results, the filtering of the center frequency of the PMN-PT substrate is a superior result to that of the $LiTaO_3$ (LT) substrate, but the result was not completely satisfactory. Also this study attempts to develop a sensing method to detect mismatched DNA in order to diagnose cancer. We could directly immobilize the MutS to the NTA using the EDC solution. But, we immobilized MutS using nickel and it is judged that is more effective method to detect mismatched DNA.

• Korean Journal of Crystallography
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• v.7 no.2
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• pp.175-182
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• 1996

ZnO thin films were deposited on Corning 7059 glass substrates to study fundamental properties of films. According to the experimental results, (002) preferred ZnO thin films were grown by purging Ar/O2 mixed gas, but not without oxygen gas. The structure and the orientation of ZnO thin films were much affected by the substrate temperature and rf power. High quality ZnO films were obtained by increasing their values. Optimum deposition parameters were : 300W rf power, 300℃ substrate temperature, Ar/O2=70/30. To characterize SAW propagation properties, IDT was fabricated by etching Al films deposited on diamond/Si wafer with RIE. Measured λ(wavelength) was 24μm and experimental results were well matched with simulation. Center frequency was 250MHz, and the calculated phase velocity of ZnO/ diamond structure was about 6000m/s.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.14-25
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• 2022

The passive surface wave method measures seismic signals from ambient noises or vibrations of natural phenomena without using an artificial source. Since passive sources are usually in lower frequencies than artificial ones being able to ensure the information on deeper geological structures, the passive surface wave method can investigate deeper geological structures. In the passive method, frequency dispersion curves are obtained after data acquisition, and the dispersion curves are analyzed by assuming 1D-layered earth, which is like the method of active surface wave survey. However, when computing dispersion curves, the passive method first obtains and analyzes coherence curves of received signals from a set of receivers based on spatial autocorrelation. In this review, we explain how passive surface wave methods measure signals, and make data processing and interpretation, before analyzing field application cases.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.5
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• pp.340-346
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• 1999

Minimum reflection and backward radiation methods on liquid/solid interrace were used to determine the velocity dispersion relation of acoustical surface wave for brass and aluminum substrates and copper/stainless steel nickel/brass, and nickel/aluminum layered substrates. Dispersion data agreed to dispersion characteristics of a generalized Lamb wave. The difference between velocities determined by two phenomena was closely related to the dispersion characteristics. This correspondence was explained by considering the generation mechanism of surface waves and the concept of group velocity.

• The Journal of the Acoustical Society of Korea
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• v.6 no.4
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• pp.5-11
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• 1987

In this paper, the measurement of SAW velocity on piezoelectric ceramic is studied. It can be done by using oscilloscope and pulse generator, and measure the velocity especially when feed-through is appeared. The propagating distance was exactly calculated considering that IDT responses are obtained by convolution theory, therefore the velocity was measured by the above simple method. As the results, the measurement velocity at room temperature was 3480 m/sec for $YZ-LiNbO_3$ single crystal and 2770 m/sec for a family of $PbTiO_3$ceramics with feed-through signal.