• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.147-150
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• 2004

The reverberation characteristics of the Korean Traditional buildings aren't well-known, but there could be many particular properties. In this study, we compare the reverberation characteristics of a Korean traditional building of a temple, ‘Magoksa’, with three modern buildings. We use 5 parameters which have been widely studied in architectural acoustics such as reverberation time, early decay time, clarity, initial-time delay gap and R/D ratio.

• 한국음향학회지
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• 제21권1호
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• pp.37-41
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• 2002

본 논문에서는 실내 잔향곡선의 초기감쇠시간을 복수 채널을 사용하여 단축시켰다. 실내에서 수음된 음성신호는 MINT(Multiple - input / output INverse Theorem)에 기초하여 풀밴드와 서브밴드로 역필터링하였으며, 복수 채널의 적응필터는 LMS(least Mean Square)와 NLMS(Normalized Least Mean Square) 알고리즘을 사용하였다. 실험결과 잔향곡선에서 -20 dB까지 감소하는데 걸리는 시간이 2개의 마이크로폰을 사용하였을 때 풀밴드 NLMS에서 약 1/3로 단축됨을 확인하였다. 실제 음장의 전달함수를 사용한 주관평가에서는 80%의 청취자가 MINT에 의해 초기감쇠시간이 단축된 음성의 명료도가 향상되었다고 평가하였다.

• 천문학회보
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• 제38권1호
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• pp.47.1-47.1
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• 2013

Supersonic turbulence is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to investigate the role of global magnetic fields and structures. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in warm neutral medium. Early evolution is consistent with previous studies characterized rapid decay of turbulence with the decaying time shorter than a flow crossing time and power-law temporal decay of turbulent kinetic energy with slope of -1. If initial magnetic fields are strong and perpendicular to the sheet, however long term evolutions of kinetic energy shows that a significant amount of turbulent energy still remains even after ten flow crossing times, and decaying rate is reduced as field strengths increase. We analyse power spectra of remaining turbulence to show that incompressible, in-plane motions dominate.

• Journal of Astronomy and Space Sciences
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• 제6권2호
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• pp.101-108
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• 1989

1983년 초 세 부분-COSMOS 1402-A, B, C-으로 분리되어 추락한 소련 위성 COSMOS 1402호의 낙하를 추정하기 위한 알골이즘을 개발하였다. 이 인공위성의 궤도에 영향을 미치는 섭동력으로는 지구의 비대칭 중력포텐셜과 지구의 대기 저항에 의한 섭동력이 고려되었고, 고도에 따른 지구의 대기 밀도를 구하기 위해 표준대기모델을 만들었다. COSMOS 1402호의 낙하시 NASA GSFC가 보내온 궤도요소 자료를 이용하여 COSMOS 1402-A와 C의 낙하시각과 낙하지점을 추정하고, 미국무성의 발표와 비교해 보았다. COSMOS 1402-C의 경우 모두 잘 일치함을 보이나 COSMOS 1402-A 의 경우 낙하시각이 1분, 낙하지점은 경위도 각각 2도씩의 오차를 보였다.

• 현장농수산연구지
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• 제6권1호
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• pp.81-89
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• 2004

포도 "캠벨얼리" 송이에 새로 개발된 봉지를 괘대하여 봉지 내부의 미기상의 변화, 생리장해 및 병 발생, 과실품질, 수확기 판정의 편이성을 조사하였다. 개발봉지의 미기상은 온도 및 광투과율은 차이가 없었으나, 상대습도 및 봉지 표면의 수분 증발량은 변화를 주었다. 수정불량과, 착색불량과, 동녹 발생율 및 회색곰광이 발생율은 처리 간 큰 차이가 없었다. 열과 및 탄저병 발생은 무대과에 비하여 개발봉지가 현저히 감소하였다. 특히 탄저병 발생정도는 개발봉지가 현저히 덜 심하였다. 과방, 과립 및 과경의 생장 및 가용성고형물, 산 함량, 과색과 과분 발생에는 큰 차이가 없었다. 개발봉지는 수확기 판정의 편이성이 우수하였으며, 과색 및 과분 발생정도가 높아 과실의 품질을 향상시킬 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제24권3호
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• pp.18-27
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• 1996

The feasibility of using stress-wave technique in the transverse direction for the assessment of early stages of decay was investigated using compression test specimens having different annual ring orientations subjected to decay by Tyromyces palustris for various time intervals. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, and stress-wave elasticity) and their percent reduction due to decay, measured by stress-wave technique in the transverse direction. The use of stress-wave technique in the transverse direction for the application of this technique to structural members in service is desirable, when considering the easiness of attachment of accelerometers of stress-wave measuring device on the surface of members and also accurate detection of localized decayed areas. In stress-wave technique in the transverse direction, stress-wave parameters measured were different according to the angles between wave propagation path and annual ring, due to the anisotropy of wood structure. Therefore, it is recommended to use percent reduction in stress-wave parameters instead of stress-wave parameters. This evaluation method using percent reduction in stress-wave parameters is ideal when it is impossible to observe annual ring orientation on the transverse surface of wood.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.340-349
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• 2016

A coupled room system consists of adjacent rooms and apertures where the sound energy is exchanged between the two rooms. Acoustically, a coupled room system shows a non-exponential decay profile. Most of the related researches have been to analyze the acoustic properties of two-room coupled system so far whereas three-room coupled system were seldom studied. In this regard, this paper aims to analyse the distribution of sound pressure level, sound decay curve of three-room coupled system and sound energy flow between them by using the acoustic diffusion model and to further verify them through experiments. Firstly, the sound pressure level distribution and mean sound pressure level in the steady-state condition are analyzed at various frequencies and source locations. Good agreements are observed in both experiments and analysis results. Secondly, two double slope effect quantifiers of sound attenuation, LDT/EDT and LDT/T10 are compared at various frequencies and for different source locations. The result indicates that LDT/T10, less affected by the early reflection patterns than LDT/EDT, is more suitable to the analysis and experiments of a multi-slope sound decay curve. Lastly, the sound energy flow in each room is analyzed based on the acoustic diffusion model. After the early decay stage, the sound energy is observed to flow from the room with a long reverberation time to the room with a short one.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.250-255
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• 1997

The computer simulation and mock-up test are recently applied to the practical design for the room acoustics to predict and evaluate its characteristics. In this paper, the sound field properties predicted and evaluated by the computer simulation were compared to the measured data. Comparison and analysis between simulation data and measured data were performed for the Reverberation Time, Sound Pressure Level at the various measuring positions and frequencies and Definition, Early Decay Time, Speech Transmission Index.

• 한국음향학회지
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• 제38권5호
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• pp.558-567
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• 2019

스피치, 국악, 뮤지컬, 대중음악과 콘서트까지 다양한 장르의 공연이 이루어지는 방송용 다목적 홀의 경우 공연에 필요한 전기, 건축 음향적 요구 조건이 다양하다. 하지만 실제 음향 환경 가변을 위한 효율적인 운용 방법은 많지 않다. 본 연구는 무대 반사판의 설치 유 무와 전기 음향 사용 조건하에서 배너의 가변에 따른 홀의 음향 환경 변화를 살펴보았다. 그 결과 벽체 면적의 15 %에 해당하는 배너를 설치한 실제 측정에서 잔향 시간(Reverberation Time, $T_{30}$)은 최대 0.12 s, 초기감쇠시간(Early Decay Time, EDT)은 0.15 s, 음악 명료도(Clarity, $C_{80}$)는 0.76 dB, 음성 명료도(Definition, $D_{50}$)는 6.43 % 변하였다. 배너의 면적을 확장시킨 컴퓨터 시뮬레이션을 통해 전체 벽체 면적의 40 %에 해당하는 배너를 설치할 경우 잔향 시간은 0.11 s에서 최대 0.55 s까지 가변되는 것을 확인했다.

• 천문학회보
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• 제43권1호
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• pp.56.1-56.1
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• 2018

Tidal disruption events (TDEs) provide evidence for quiescent supermassive black holes (SMBHs) in the centers of inactive galaxies. TDEs occur when a star on a parabolic orbit approaches close enough to a SMBH to be disrupted by the tidal force of the SMBH. The subsequent super-Eddington accretion of stellar debris falling back to the SMBH produces a characteristic flare lasting several months. The theoretically expected bolometric light curve decays with time as proportional to $t^{-5/3}$. However, the light curves observed in most of the optical-UV TDEs deviate from the $t^{-5/3}$ decay rate especially at early time, while the light curves of some soft-X-ray TDEs are overall in good agreement with the $t^{-5/3}$ law. Therefore, it is required to construct the theoretical model for explaining these light curve variations consistently. In this paper, we revisit the mass fallback rates analytically and semi-analytically by taking account of the structure of the star, which is simply modeled by the polytrope. We find the relation between a polytropic index and the power law index of the mass fallback rate. We also discuss whether and how the decay curves, which we derived, fit the observed ones.