• 대한조선학회논문집
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• 제55권5호
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• pp.394-400
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• 2018

Various numerical methods have been adopted for indoor noise assessments of ship plant. Acoustical radiosity method is one of the high frequency approaches for acoustic field analysis, which assumes diffuse reflections by boundaries so that it could be efficiently applied to the acoustically diffused indoor space noise analysis. In this study, an acoustic field analysis program has been developed based on radiosity method, which could apply for acoustically large enclosures such as ship's indoor space. For this purpose, the procedure of the acoustical radiosity method has been summarized and implemented to an acoustic field analysis program using MATLAB. Numerical example for a rectangular indoor space has investigated validity of the implemented program. Steady state sound pressure levels calculated for a continuous acoustic source signal have shown good agreement with those by other solutions such as an analytic solution and a ray tracing method. Instantaneous sound pressure levels calculated for an impulsive acoustic signal have provided the clues of direct/reflected acoustic field and reverberation time.

• 천문학논총
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• 제30권2호
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• pp.443-445
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• 2015

We provide results of near-infrared (NIR) spectroscopic observations of 83 nearby (0.002< z <0.48) and bright (K <14 mag) type 1 active galactic nuclei (AGNs). For the observations, we used the Infrared Camera (IRC) on AKARI allowing us to obtain the spectrum in the rarely studied spectral range of $2.5-5.0{\mu}m$. The $2.5-5.0{\mu}m$ spectral region suffers less dust extinction than ultra violet (UV) or optical wavelength ranges, and contains several important emission lines such as $Br{\beta}$ ($2.63{\mu}m$), $Br{\alpha}$ ($4.05{\mu}m$), and polycyclic aromatic hydrocarbon (PAH; $3.3{\mu}m$). The sample is selected from the bright quasar surveys of Palomar Green and SNUQSO, and AGNs with black hole (BH) masses estimated from reverberation mapping method. We measure the Brackett line properties for 11 AGNs, which enable us to derive BH mass estimators and investigate circum-nuclear environments. Moreover, we perform spectral modeling to fit the hot and warm dust components by adding photometric data from SDSS, 2MASS, WISE, and ISO to the AKARI spectra, and estimate hot and warm dust temperatures of ~1100K and ~220 K, respectively.

• 한국음향학회지
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• 제21권4호
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• pp.421-429
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• 2002

해수면에서의 음파산란 특성을 파악하기 위한 해수면 후방산란실험을 2000년 11월 동해시 연안에서 수행하였다. 평면입사각의 범위는 20°∼40°였고 주파수는 60 kHz였다. 실험해역의 풍속은 3 m/s, 해수면 거칠기는 1 m이하로 관측되었다. 분석된 해수면 후방산란강도는 경계면 산란강도 예측 모델에 비해서 높게 나타났으며 이러한 차이는 작은 평면입사각에서 더욱 크게 나타났다. 이러한 차이를 설명하기 위하여 해수면 부근의 공기방울층에 의한 산란 효과를 고려한 결과 실측치와 모델이 잘 일치하였다.

• 한국재난정보학회 논문집
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• 제12권3호
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• pp.235-241
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• 2016

최근 우리나라는 사회경제적 발전과 본격적인 고도기술사회로 진입하였다. 그러나, 재난에 대응하는 개인의 능력은 사회의 복접성 증가로 낮아지고 있다. 재난 발생 시 개인이 파악할 수 있는 정보의 한계로, 정확한 상황판단 및 재난대응이 어려워졌다. 지금까지는 일반 스피커를 활용한 재난경보방송을 하였다. 그러나 일반 스피커는 음의 반사에 의한 잔향음, 음의 감쇠현상 등에 의하여 명료한 음의 청취가 어려웠다. 이러한 문제점을 해결하기 위하여 음이 직진하는 특성과 음의 감쇠가 없는 지향성스피커를 활용하여 구난자에게 재난발생 상황 및 피난에 유효한 정보들을 효과적으로 제공할 수 있는 방안에 대하여 제안한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.501-505
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• 2013

It is well known that monolithic glass has specific coincidence dip allowing transmittance of noise around the critical frequency. Laminated glass, made of a polyvinyle butyral(PVB) interlayer sandwiched by two panes of glass sheet, has long served for the advantage in noise attenuation properties as well as the safety purpose. More research on the improvement of sound insulation performance is needed, considering much of the noise is still transmitted through the glass. As a preliminary study, authors have made several test specimens, varied combinations of glass and interlayer film, to optimize the acoustic performance. Experimental investigation was carried out to study the sound transmission loss of test specimens in the reverberation chamber by using sound intensity method. Several new applications, instead of the existing PVB laminated glass, show better results in sound transmission loss and low temperature have a bad influence on the acoustic performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.367-370
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• 2005

This paper investigated the sound characteristics in an apartment complex. The field measurement was conducted in order to examine the acoustical characteristics of the apartment complex in situ. As a result, it shows that there are around 3 sec. reverberation time and the additional sound reinforcements at the area of high height due to the surrounded buildings. Thus, 1:50 Scale model measurement and Raynoise computer simulation were carried out with insertion of the parapet and the canopy on the balcony. In case of a single building, the parapet was effective to reduce noise level at low floor levels, and the canopy was effective to reduce noise level at high floor levels. But it also shows that both the parapet and the canopy were not effective to reduce noise level at middle floor levels. In case of an apartment complex, the canopy was less effective to reduce noise level at each floor in comparison with case of the single building.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.785-790
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• 1994

The active noise control which regards the acoustic power as a target function to be minimized, is analyzed to test its feasibility of which simplifies the measurement system compared with the global acoustic energy based active noise control system. In fact, it is found that the acoustic power based active noise control strategy is equally likely as good as the global acoustic energy based active noise control method if the acoustic field of interest is diffusive or very low model density one. In the intermediate model density field, we also demonstrate that the power based control gives the similar results as the energy based control in terms of global sound energy reduction for the lightly damped enclosure which might be most important system in practical application. From all the theoretical and power based control strategy is dependent on the characteristics of the acoustic field to be controlled; i.e., the model density distribution, the degree of reverberation, and on the strength of modal interaction of the control source with the primary source; i.e., the location of control source.

• 한국음향학회지
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• 제40권5호
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• pp.452-459
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• 2021

서로 떨어져 설치된 두 개의 음향 수신기에 도달하는 신호의 상호 지연 시간을 추정하는 것은 실내 음향과 소나 등에서 목표물 위치 추정 문제나 추적 등 여러 방면에서 쓰이고 있다. 시간 지연을 구하는 방법에서는 두 수신 신호 사이의 상호 상관을 이용한 방법으로 대표되는 비 파라메트릭 방법과 시스템 인식을 기반으로 하는 파라메트릭 방법이 있다. 본 논문에서는 파라메트릭 방법에 기반을 둔 시간 지연 추정 방법을 제안한다. 특히 음향 수신기에 잡음이 부과되는 것을 고려한 방법을 제안한다. 그리고 백색 잡음 및 잔향 환경에서 기존의 일반 상호 상관법과 적응 고유치 분석법과 비교를 통해서 새로 제안한 알고리즘이 더 우수함을 확인한다.

• 천문학회보
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• 제44권1호
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• pp.77.3-77.3
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• 2019

Aims. The evolution of scaling relations between SMBHs and their host galaxies becomes uncertain at high redshifts. The HULQ project proposes to use gravitational lensing to measure the masses of QSO host galaxies, an otherwise difficult goal. SMBH masses of QSOs are relatively easy to determine using either reverberation mapping or the single-epoch method. These measurements, if made for a substantial number of QSOs at various redshifts, will allow us to study the co-evolution of SMBHs and their host galaxies. To determine the feasibility of this study, we present how to estimate the number of sources lensed by QSO hosts, i.e. the number of deflector QSO host galaxies (hereafter QSO lenses). Method and results. Using SMBH masses measured from SDSS DR14 spectra, and the M_BH - Sigma relation, the Einstein radii are calculated as a function of source redshift, assuming singular isothermal sphere mass distributions. Using QSOs and galaxies as sources, the probability of a QSO host galaxy being a QSO lens is calculated, depending on the limiting magnitude. The expected numbers of QSO lenses are estimated for ongoing and future wide-imaging surveys, and additional factors that may affect these numbers are discussed.

• 한국음향학회지
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• 제40권3호
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• pp.254-260
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• 2021

시료의 흡음률 측정을 위해서는 비용이 많이 드는 잔향실 혹은 저주파수에서의 측정에 한계가 있는 임피던스 튜브를 사용한다. 본 논문에서는 마이크로폰을 사용하지 않고 단지 스피커 임피던스와 이로부터 도출된 Thiele/Small 변수만을 사용하여 시료의 음향임피던스와 흡음률을 구하는 기법을 제안하였다. 스피커의 등가회로를 이용하여 이 방법의 이론을 설명하였으며, 시료의 측정을 통하여 본 방법의 유효성을 증명하였다. 본 방법은 기존에 신뢰하기 어려웠던 저주파 대역에서의 흡음률을 매우 쉽게 측정할 수 있음을 확인하였다. 본 방법의 장점과 제한사항, 그리고 응용 분야에 대해서 검토하였다.