• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.20-22
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• 2014

선박, 해양플랜트에 적용되는 PAGA System 는 선내 모든 선원 및 승객에 대하여 정보전달 기능뿐 아니라 위급 상황 발생시 신속한 상황 전달 및 대피를 위한 안전상의 이유로서 매우 중요시 되고 있다. PAGA 의 핵심이 되는 Audio Coverage 의 경우, 초기 설계단계에서 해석을 통해 스피커 배치가 이루어지는데, 본 논문에서는 이러한 PAGA Audio Coverage 관련 요구조건과 합리적인 적용방안, 해석 및 평가 방안에 대하여 사례를 통해 소개하고자 한다.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.10-17
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• 2004

In this research, a numerical simulation for the acoustic sounds around a two-dimensional circular cylinder in a uniform flaw was developed, using the finite difference lattice Boltzmann model. We examine the boundary condition, which is determined by the distribution function concerning density, velocity, and internal energy at the boundary node. Pressure variation, due to the emission of the acoustic waves, is very small, but we can detect this periodic variation in the region far from the cylinder. Daple-like emission of acoustic waves is seen, and these waves travel with the speed of sound, and are synchronized with the frequency of the lift on the cylinder, due to the Karman vortex street. It is also apparent that the size of the sound pressure is proportional to the central distance to the circular cylinder. The lattice BGK model for compressible fluids is shown to be a powerful tool for the simulation of gas flaws.

• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.30-36
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• 2008

Underwater ambient noise originating from geophysical, biological, and man-made acoustic sources contains information on the source and the ocean environment. Such noise affectsthe performance of sonar equipment. In this paper, three steps are used to identify the ambient noise source, detection, feature extraction, and similarity measurement. First, we use the zero-crossing rate to detect the ambient noisesource from background noise. Then, a set of feature vectors is proposed forthe ambient noise source using the Hilbert-Huang transform and the Karhunen-Loeve transform. Finally, the Euclidean distance is used to measure the similarity between the standard feature vector and the feature vector of the unknown ambient noise source. The developed algorithm is applied to the observed ocean data, and the results are presented and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.312.2-312
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• 2002

Theoretical analysis of transient torsional vibration was started from early 1960's for high power synchronous motor application. Especially, its simulation and measuring techniques in marine engineering field have been steadily studied by manufacturers of flexible coupling and designers of four stroke marine diesel engine. In this paper, the simulation method of transient torsional vibration of four stroke marine diesel engine using the Newmark method are introduced. (omitted)

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.229-237
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• 2017

In this paper we propose an auto tonal detection method which exploits short term stationary when targets located in a detection beam area and then additional methods are proposed in order to reduce the computational complexity of the proposed method. The proposed method is adaptive to input signals and robust against interference caused by multiple targets because it compares an expected value of input signals with a threshold value which are estimated from a single beam while signals are keep stationary. The performances of the proposed methods are evaluated using by simulated data and acquired data from real ocean. The proposed method has shown better performance than conventional CFAR (Constant False Alarm Rate) methods.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.228-236
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• 2021

In order to understand the underwater noise source factor of the linear pump type forced ejection system, a reduced-model compressed water experiment device was developed. The reduced-model compressed water experiment device consists of a reverberation tank, a linear pump type forced ejection device, and an underwater vehicle. The underwater noise source was selected from the hydraulic ram moving speed, the hydraulic ram/piston pipe spacing, the ejection pipe inlet/water ram area ratio, and the number of water ram inlets. The underwater vehicle was ejected into the reverberation tank by the device. The source level was derived from the measured sound pressure. The source level tends to increase as the hydraulic ram/piston tube spacing and the hydraulic ram moving speed increase. The source level tended to increase as the area ratio was increased, but the level was weak. The number of water ram inlet did not affect the source level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.523-526
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• 2014

Recently, all the generators needed of the boats are being imported, so our objective is to make a national production of soundproof generators. We have already built a marine soundproof generator and it has also been hrough an endurance test for its commercialization. This paper has the noise vibration measurements needed for maintaining its durability and performance. We concluded that the difference of the noise values with and without the case was of 11.4dB.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1998.06a
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• pp.105-106
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• 1998

• The Journal of the Acoustical Society of Korea
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• v.37 no.3
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• pp.129-138
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• 2018

In port and coastal areas where ship traffic is frequent, ship noise dominantly influences underwater noise in low frequency band below 1 kHz. In this paper, we propose a modeling method to estimate the underwater shipping noise using the voyage information of ship observed in AIS (Automatic Identification System). For the purpose of ship noise modeling, the navigation information of the vessels operating in the southern part of Jeju was observed using AIS and underwater noise was measured by installing a hydrophone in the experimental area to verify the modeled ship noise. AIS data were used to model the noise level of ship and compared with measured underwater noise. The variation of noise level with time was found to be similar, and the cause of the error was discussed. Through this study, it was confirmed that the noise level of ship can be estimated within 5 dB error range using AIS data.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.67-68
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• 2001

멸치를 어획하는 주 어구인 초망어업은 우리나라 남해안과 제주도 연안에서 행해지는 고유어법으로서, 이러한 초망어업은 큰 챗대 1개와 작은 챗대 1개는 반 기계적으로, 콧대 1개와 그물작업은 인력으로 조작되고 있는데, 멸치어군의 집어는 집어등을 선수 전방에 설치하여 2-3노트의 속력으로 항해하면서 멸치어군을 표층으로 부상시킨다. 이때 집어등만으로 멸치어군이 표층으로 부상하지 않으면 쇠파이프로 어선의 외관을 두드리거나 또는 기관 회전수를 빠르게 하여 공회전 시키면서 수중 소음을 발생시켜 멸치어군을 표층으로 유집시킨다. (중략)