• 한국음향학회지
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• 제19권3호
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• pp.77-85
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• 2000

사질퇴적물의 함량이 높은 대한해협 퇴적물에 대해 새로운 음파전달속도 측정 장비(sediment sound velocimeter)를 이용 음파전달속도와 물리적 성질을 측정하여, 연구지역의 지음향 및 물리적 특성을 제시하였다. 연구지역 퇴적물의 물성 및 음파전달속도 변화는 조직의 변화에 의해 크게 좌우되는 것으로 나타났다. 연구결과 음향 및 물성 값을 바탕으로 연구지역을 3개 지역(provinces; mid-shelf, shelf margin and trough)으로 구분할 수 있었으며, 이러한 결과는 탄성파 단면 분석을 통해 시스템 트랙과 퇴적계로 지역구분한 기존의 결과[14]와 잘 일치한다. 연구를 통해 새롭게 제시된 3개 지역의 지음향모델은 Briggs and Fischer[5]가 제시한 기존의 대한해협 지 음향모델의 수정모델로 제시한다.

• The Journal of the Acoustical Society of Korea
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• 제24권3E호
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• pp.90-98
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• 2005

Enhanced approach using computational and experimental method is proposed and performed to describe very well the behavior of loudspeaker than conventional method. Proposed procedure is composed of four parts. First, Thiele-Small parameters for test loudspeaker are identified by an electrical impedance method like as a delta mass method. Second part includes the processes to measure physical properties. Physical data like masses and thicknesses of loudspeaker's components are measured by an electrical precision scale and a digital vernier caliper. Third, the identified Thiele-Small parameters are proposed to be used as load boundary conditions for vibration analysis instead of electromagnetic circuit analysis to get a driving force upon bobbin part. Also, these parameters and physical data are used to modify physical properties required for computation to accommodate simulated sound pressure level with measured one for loudspeaker enclosure system. These data like as Young's modulus and thickness for a diaphragm are required for vibration analysis of loudspeaker but not measured accurately. Finally, it was investigated that simulated sound pressure level with full acoustic modeling including an acoustic port for test loudspeaker agreed with experimental result very well in the midrange frequency band(from 100 Hz to 2,000 Hz). In addition, several design parametric study is performed to grasp acoustical behaviors of loudspeaker system due to variations of diaphragm thicknesses and shapes of dust cap.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.711-714
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• 2000

In this study, the physical properties of the acoustic element and case with metal-piezoelectric ceramics were analyzed. The dielectric and piezoelectric properties of 0.5 wt% MnO$_2$and NiO doped 0.1Pb(Mg$\_$1/3Nb$\_$2/3)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. Also, the acoustic characteristics for the geometrical form of case have been investigated. The design and fabrication method worked in this paper can be utilized in development of actuator and acoustic device.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.413-416
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• 2000

In this study, the physical properties of the acoustic element and case with metal-piezoelectric ceramics were analyzed. The dielectric and piezoelectric properties of 0.5 wt% MnO$_2$ and NiO doped 0.1Pb(Mg$_{1}$3/Nb$_{2}$3/)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. Also, the acoustic characteristics for the geometrical form of case have been investigated. The design and fabrication method worked in this paper can be utilized in development of actuator and acoustic device.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.244-249
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• 1997

The enclosure with a small opened area is extensively used in power plants to reduce the propagating noise from transformers. The radiation impedance associated with the location and width of the opened area, and the geometric configurations of internal acoustic field is very important to determine the basic acoustic characteristics of this partial enclosure. In this study, two-dimensional rectangular chambers with opened areas are investigated to examine the acoustic properties of the enclosure. The mode expansions of the physical variables defined on boundary surfaces are introduced to derive a simple algebraic equation. The acoustic characteristics can be easily predicted by this analytical approach, and the results well agree with physical grounds. Physical concepts as results of this work will be helpful to use the partial enclosure as a noise control element.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1984년도 추계학술발표회 논문집
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• pp.27-32
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• 1984

When chopped light inpinges on some condenced matters such as HgS, HgI2 and GaSe semiconductors, in an enclosed cell, the acoustic signals are produced within the cell. These acoustic signals were detected by using a gas-phase microphone in order to investigate the physical properties of the samples. In order to carry out investigation, PA-cell was first designed and made so as to produce higher sensitivity to acoustic signals. Second, an analysis of the photoacoustic spectrum of the various compounds was carried out to obtain the intensity of the PA-signal in terms of light wavelength and to calculate the energy band gaps occuring according to energy transitions. The agreement between the results obtained by this conventional PAS technique and the results obtained by the optical spectrum method was good. In additional analysis conducted on the basis of the R-G theory and the Sze theory are capable of determining the characteristics of energy transition of semiconductors.

• Applied Microscopy
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• 제50권
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• pp.25.1-25.11
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• 2020

Scanning acoustic microscopy (SAM) or Acoustic Micro Imaging (AMI) is a powerful, non-destructive technique that can detect hidden defects in elastic and biological samples as well as non-transparent hard materials. By monitoring the internal features of a sample in three-dimensional integration, this technique can efficiently find physical defects such as cracks, voids, and delamination with high sensitivity. In recent years, advanced techniques such as ultrasound impedance microscopy, ultrasound speed microscopy, and scanning acoustic gigahertz microscopy have been developed for applications in industries and in the medical field to provide additional information on the internal stress, viscoelastic, and anisotropic, or nonlinear properties. X-ray, magnetic resonance, and infrared techniques are the other competitive and widely used methods. However, they have their own advantages and limitations owing to their inherent properties such as different light sources and sensors. This paper provides an overview of the principle of SAM and presents a few results to demonstrate the applications of modern acoustic imaging technology. A variety of inspection modes, such as vertical, horizontal, and diagonal cross-sections have been presented by employing the focus pathway and image reconstruction algorithm. Images have been reconstructed from the reflected echoes resulting from the change in the acoustic impedance at the interface of the material layers or defects. The results described in this paper indicate that the novel acoustic technology can expand the scope of SAM as a versatile diagnostic tool requiring less time and having a high efficiency.

• 한국음향학회지
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• 제28권3호
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• pp.165-173
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• 2009

해양 탐사에 있어서 해저퇴적물의 물성을 파악하는 것은 해양 연구의 기초 자료로써 활용되고 있다. 이러한 해저퇴적물의 물성을 파악하기 위해서는 시추를 통한 직접적인 방법이 있지만 경제적, 시간적 손실이 크고 공간적인 한계가 있다. 이에 음향 장비를 이용한 해저퇴적물 분류 연구가 활발히 진행 중에 있다. 본 논문에서는 해저 지형 조사 장비의 일종인 음향측심기에 의한 음향 신호의 나카가미(Nakagami) 분포를 분석하여 해저퇴적물의 특성을 분류하는 연구를 수행하였다. 나카가미 변수인 m 값의 변화에 따라 해저퇴적물의 물리적 특성이 달라지는 것을 확인하였고, 이는 해저퇴적물특성 연구의 기초자료로 활용되리라고 여겨진다.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.12-19
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• 2001

In this study, the physical properties of the piezoelectric sounder with metal-piezoelectric ceramics were analyzed. The dielectric and piezoeletric properties of 0.5wt% MnO$_2$ and NiO doped 0.1Pb(Mg$\_$1/3/Nb$\_$2/3/)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ ceramics were investigated aiming at acoustic transducer applications. The acoustic characteristics of a thin circular disc-type with metal-piezoceramics have been investigated. Also, the acoustic characteristics for the geometrical form of case were investigated. The piezoelectric sounder with 200kHz resonant frequency and 20kHz bandwidth was designed by considering the sharp directivity and the sound pressure.

• 한국수산과학회지
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• 제27권4호
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• pp.434-444
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• 1994

여수해만 주변해역 퇴적물의 물리적 성질 및 음향학적 성질을 밝히기 위해서 총 36개 시추시료에서 10cm 간격으로 퇴적물의 조직(입도), 음파전달속도 및 물리적 성질(공극율, 전밀도, 함수율, 전단응력)을 측정하였다. 연구지역을 광양만, 여수해만, 남해대륙붕의 세 지역으로 나누어 각 지역간의 물성과 조직의 상관관계를 비교 검토하였다. 비교 모델로는 Hamilton(1970)의 북태평양 대륙붕 및 대륙사면 퇴적물을 이용하였다. 본 연구지역에서의 조직과 물성의 분포도(50cm 깊이)를 보면 평균입도($6.5{\sim}8.1{\phi}$), 점토함량($35{\sim}50\%$), 공극율($66{\sim}80\%$), 속도($1540{\sim}1525m/s$), 전단응력($2{\sim}8kPa$), 밀도($1.60{\sim}l.40a/cm^3$) 등이고 각각의 특성이 광양만에서부터 남해 대륙붕 지역으로 갈수록 점진적인 변화를 보이는 것으로 나타났다. 이런 특징은 본 연구지역의 주요한 공급원인 섬진강에서 유입되는 퇴적물이 광양만 및 여수해만을 통하여 남해 대륙붕 지역으로 이동하는 경로와 관련이 있는 것을 시사한다. 각 물성간의 상관관계를 보면 여수해만 및 남해 대륙붕 지역이 광양만보다도 Hamilton(1970)이 제시한 모델에 더 유사한 경향을 보인다. 물성 분포로 보아 여수해만 지역 퇴적물의 성질은 광양만과 남해대륙붕 지역 퇴적물의 중간적인 단계에 해당되는 것으로 생각된다.