• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.217-221
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• 2008

To investigate the enhancing effects in transdermal permeation of drug using newly designed ultrasound apparatus of 500 kHz, the transdermal permeation studies through the hairless mouse skin were conducted with lidocaine. The ultrasound apparatus of 500 kHz frequency and transducer were newly developed. The drug permeation studies were performed according to the ultrasound frequencies such as 1 MHz and 500 kHz at $1W/cm^2$ in intensity in continuous mode or pulsed mode, respectively. The results on transdermal permeation of lidocaine according to ultrasound intensity showed that the drug permeation increased as the intensity was higher.

• The Journal of the Acoustical Society of Korea
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• v.34 no.5
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• pp.371-376
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• 2015

In this study, we use 1:1, 1:2, and 1:4 scale zig-zag shape acoustic metamaterial structure to achieve broad and effective sound blocking at the subwavelength scale. The SPL(Sound Pressure Level) results show that the SPL loss of the scaled metamaterial slab in series is a superposition of individual SPL losses. Also, we show that the metamaterial tailors the material properties to achieve high impedance and high refractive index using effective medium theory. Our results show that broad and effective sound blocking is possible at the subwavelength scale just by scaling acoustic metamaterial.

• Journal of the Korean Geophysical Society
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• v.4 no.2
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• pp.95-102
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• 2001

As a basic study of characterizing fracture condition in bore hole, conventional geophysical well log data consisting of sonic, gamma-gamma and resistivity logs were compared with geological core log and acousic televiewer log in limestone geology. Discontinuities shown on the acoustic televiewer log and the core log show fairly good correlation. The conventional Geophysical log is also shown to bi effective in locating discontinities in limestone geology; sonic log shows the best result and resistivity shows the worst. Particularly, the combination method of density and sonic logs is shown to be the most effective in delineating discontinuities.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.795-801
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• 1999

An experimental investigation has been conducted with the objective of studying the mixing mechanism near the nozzle exit in a tone-excited jet diffusion flame. The fuel jet was pulsed by means of a loudspeaker-driven cavity. The excitation frequencies were chosen for the two cases of the non-resonant and resonant frequency identified as a fuel tube resonance due to acoustic excitation. The effect of tone-excitations on mixing pattern near the nozzle exit and flame was visualized using various techniques, including schlieren photograph and laser light scattering photograph from $TiO_2$ seed particles. In order to clarify the details of the flame feature observed by visualization methods, hotwire measurements have been made. Excitation at the resonant frequency makes strong mixing near the nozzle. In this case, the fuel jet flow in the vicinity of nozzle exit breaks up into disturbed fuel parcels. This phenomena affects greatly the combustion characteristics of the tone excited jet and presumably occurs by flow separation from the wall inside the fuel nozzle. As a result, in the resonant frequency the flame length reduces greatly.

• The Journal of the Acoustical Society of Korea
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• v.14 no.6
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• pp.48-53
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• 1995

A considerable number of methods are available for predicting traffic noise levels of road networks where sound is freely propagating. But surrounding buildings reflect back sound to the road and sound energy is increased by these reflectors. Therefore, this study was focussed on the establishment of the prediction method of road traffic noise under reflective conditions. This prediction method was developed by establishing prediction formulas of noise level such as $L_{10},\;L_{50},\;L_{90}\;and\;L_{eq}$. The sound energy density was employed to establish prediction formulas in terms of independent variables. The validity of the proposed prediction formulas was been confirmed by applying them to actually measured parameters of road traffic noise and noise level data. On the whole, the agreement between measured and predicted noise levels appeared to be satisfactory. The conclusion might be reached that the method developed in this study could be used to predict road traffic noise under reflective conditions.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.197-200
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• 2001

입사된 음파에 대한 배진동 주파수의 발생과 입사 음파들간의 합$\cdot$차 주파수 발생은 물체내 결함이 존재할때에 나타나는 중요한 비선형 효과라는 것을 이용하여 단순화된 실험실 조건의 겹쳐진 두 장의 유리판에 적용하였다. 본 논문에서는 적층 접합 물체에 있어서의 비파괴 검사법을 위해 접합되지 않은 결함 부분은 두 장의 유리판 사이의 공기 층으로 단순화하였고, 접합되어진 부분은 물 층으로 단순화하여 실험을 진행하였다. 서로 다른 조건의 두 접합 부분으로부터 발생된 입사된 기본 주파수의 배진동 주파수 발생과 합 $\cdot$차 주파수 발생을 관측함으로써 구조물 내의 결함 유$\cdot$무를 판별하였다. 배진동 주파수의 발생과 합$\cdot$차 주파수의 발생은 결함이 존재할 경우에 두드러지게 나타났지만, 결함이 존재하지 않는 경우에서는 비선형 반응의 발생이 억제되었다. 이 결과로부터 비선형 현상의 발생은 이차원적인 적층 구조물에도 적용 가능하며, 비선형 비파괴 음향 탐사법에 의한 결함의 존재 유$\cdot$무 판별이 가능하였다.

• Korean Educational Research Journal
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• v.39 no.1
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• pp.15-38
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• 2018

This study aimed to confirm that the lateral lines of fish indicate water temperature, water pressure, water flow, and sound waves by conducting a direct experiment. To confirm the superiority of fish lateral lines to detect material stimuli after the experimental study of the fish lateral line's sensation function, the lateral line's tissue was expanded and the shape of the lateral side of the fish was created using a 3-D printer to realize the lateral stripe parity. The amplification effect was confirmed by measuring the sound waves, which was the material stimulus of the lateral diagonal parabola. This proved that fish lateral lines are biotechnologically superior sensory organs.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.307-310
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• 2000

평판에서 발생되는 램파가 물체 내에 존재할 수 있는 미세 결함과의 상호작용에 의해 비선형 음향효과를 발생시키는지 관찰하고 이로부터 결함의 존재 유$\cdot$무를 확인하고자 했다. 이차원의 판형 매질로서 $2000{\times}110{\times}2{\cal}mm^3$인 강철판을 사용했으며 결함은 강철판의 임의의 위치에 인위적으로 미세틈새를 형성하여 모델화시켰다. 488kHz의 저주파수 연속파와 톤버스트 형태의 1MHz 고주파수 음파를 입사시켰다. 결함의 유$\cdot$무에 따른 강철판에서의 수신음파에 대한 주파수 응답을 통하여 비선형 음향반응인 배진동 주파수와 합$\cdot$차 주파수의 발생을 관측함으로써 매질 내의 결함 유$\cdot$무를 판별하고자 했다. 결함이 존재할 경우, 존재하지 않을 경우와 비교했을 때 배진동 주파수는 진폭이 15dB, 합$\cdot$차주파수는 진폭이 18dB이상 증가됨을 관찰함으로써 평판에서의 결함의 존재 유$\cdot$무를 확인할 수 있었다.

• Defense and Technology
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• no.3 s.145
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• pp.17-25
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• 1991

Sting Ray는 현대의 첨단기술로 제작된 경어뢰로서, 완전히 디지털 컴퓨터 제어에 의해 작동한다. 항공기에 장착된 유도미사일과 그 기능을 견줄수 있는 최첨단 수중유도무기이며, 수중에서의 음파탐지 및 식별에 수반되는 각종 난관을 극복하였다. 수중에서의 음의 반사 및 굴절효과로 인해 복잡성이 가중된 잡음의 근원과 바닷물의 특성이 수시로 변화되는 상황에서 음향장치 사용을 결정하는 것은 매우 어려운 과제이나, Sting Ray는 이러한 어려운 환경을 극복할수 있도록 설계되었다. 또한 선박, 항공기 또는 헬기등 어디에서 발사되더라도 자율적으로 자체의 전술을 창조하는 Shaped Charge형 탄두는 어떠한 표적에도 치명적 피해를 줄수 있다

• The Journal of the Acoustical Society of Korea
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• v.10 no.6
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• pp.77-81
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• 1991

단백질수용액중의 초음파흠수 mechanism을 규명하기 위하여 천연단백질인 egg white의 초음파 흡수측정을 주파수 0.2-10MHz, 온도 10-50℃에서 행하엿다. 측정방법은 0.2-10MHz 주파수범위에서 초 음파흡수측정이 가능한 plano-concave 공명법을 사용하였다. 그 결과 0.2-10MHz의 주파수범위에 대해 흡수계수는 측정한 전 온도에서 주파수의 1.25(±0.02) 승에 비례하고, egg white의 농후부분과 수용성부 분 및 aging 효과에 대한 음향학적인 차는 나타나지 않았다.