• Journal of KSNVE
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• v.6 no.5
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• pp.575-585
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• 1996

In order to build a quiet and comfortable ship, the noise levels on board ship must be predicted at early design stage. Statistical Energy Analysis (SEA) developed by R. H. Lyon has been well known to be the most useful frame work to study the energy flow of noise and vibration in structure. This paper applied this theory to predict the transmission loss of structure-borne noise of model structure and has developed computer program. Components constructions model structure have been all considered as SEA elements. And we also estimated the SEA parameters from the model structure. Using SEA and a new conception of STL, we found the transimission character of structure-borne noise theoretically by the idealized ship model, and then compared the results with three cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.158-163
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• 2008

Muffler design in the exhaust system is critical to provide for low noise in shipboard spaces. In an attempt to effectively design the low noise muffler, it is important to evaluate the performance of the muffler considering not only the noise, but also pressure drop as well. For this purpose, a test system of large exhaust muffler for ship propulsion systems was designed based on ISO 7235. The substitution test for determining both the insertion loss and pressure drop of mufflers was carried out. A ship exhaust muffler is considered as a test example and the insertion loss and pressure drop are obtained.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.12
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• pp.1237-1242
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• 2008

A muffler design in the exhaust system is critical to provide fur low noise in shipboard spaces. In an attempt to effectively design the low noise muffler, it Is important to evaluate the performance of the muffler considering not only the noise, but also pressure drop as well. For this purpose, a test system of large exhaust mufflers fur ship propulsion systems was designed based on ISO 7235. The substitution test fur determining both the insertion loss and pressure drop of mufflers was carried out. A ship exhaust muffler is considered as a test example and the insertion loss and pressure drop were obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.223-230
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• 1995

본 연구에서는 선박소음해석을 수행하기 위한 기초작업으로서 실선 선박모델을 크게 3가지 경우로 구분하여 모델링 하였으며, SEA법을 적용하여 고체소음의 전달손실을 이론적으로 예측할 수 있는 방법을 제시하였으며, 또한 STL을 도입하여 각 요소간의 에너지 흐름 및 구성판요소의 재료별 방진효과를 알아보았다. 이 방법의 결과 다음과 같은 결론을 얻을 수 있었다. 1) 내장판의 종류에 따른 전달특성은 고주파 대역에서는 plywood, 저주파 대 역에서는 rockwool이 높은 손실값을 보였으며, glasswool은 전 주파수 대역에서 고른 손실값을 가짐을 확인하였다. 2) 기진원으로부터의 거리가 멀어짐에 따라 내장판의 효과가 크게 나타나며, 기진원의 근방 요소에서는 내장판의 효과보다는 강판의 두께의 영향이 두드 러짐을 알 수 있었다. 3) 내장판 요소중 plywood의 방진효과가 가장 크게 나타남을 알 수 있었다. 4) 본 SEA법에 의한 연구에서는 구성 판요소의 재질과 두께에 따른 고쳇음 의 전달특성을 이론적으로 해석하였으며, 차후 실험을 통한 검증이 요구되어 진다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.6
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• pp.432-439
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• 2015

In order to reduce the structure borne noise of the equipment sufficiently, its exciting force should be restricted and additional anti-vibration devices such as resilient mount and bellows should be applied. Since the structure borne noise is dependent on the design of the base for the equipment, it is very important to design the base with low vibration. Therefore, in this research, various types of the base design for the shipboard equipment are investigated to reduce the structure borne noise. In order to design the base with low vibration, the exciting force at the center of the gravity of the equipment is firstly defined through the experiment. Using the exciting force identified by experiments, various types of base designs for the typical turbo machine are evaluated by FEM(finite element method) analysis.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.117-122
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• 2001

The shock test of shipboard equipments is performed for the evaluation of the shock-resistant. capability by analyzing the maximum acceleration, the effective time duration and the shock response spectrum, etc. But some measured signals have impulsive noise and gaussian white noise because of the ambient noise, the acquisition equipment error and the transient movement of cables during the shock test. The improved transient signal analysis method which removes the noise of measured signal using the threshold policy of the median filter and the orthogonal wavelet coefficients is proposed. It was verified that the signal-to-noise ratio was improved about 30dB by the numerical simulation. And the shock response spectrum was extracted using the denoised shock response signal which was applied by this proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.71-77
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• 2001

In this paper, stress wave propagation characteristics of MR(Magneto-rheological) inserts are experimentally investigated. Generally, stress waves of structures such as warships or submarines are induced by shock waves from underwater explosion. Their fatal effects on the shipboard equipments or structures damage the performance of warships. But, such a problem can be solved by controlling the stress waves propagating through structures by means of MR inserts. MR insert consists of two aluminum layers and MR fluid filled in between. Two piezoceramic disks are embedded on the host plate as a transmitter and a receiver of stress waves. Pulse waves are generated by the transmitter and they reach to the receiver through the MR insert. Permanent magnet and magnetic coil are used to produce magnetic field at the MR insert. In the presence of magnetic field, MR particles are arranged in chains parallel to the magnetic field such that the transmitted stress waves are reduced. Attenuation of stress waves is experimentally investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.803-808
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• 2011

The shipboard working environment of navy vessel is very inferior to the ground working environment. For this reason, the crew of a navy vessel suffer from an occupational disease such as lumbar pain, hearing loss, etc. Although standard for navy vessel's environmental vibration is applied, the criterion of the environmental vibration is too high. So it doesn't help to improve habitability of crew. In this study, for improving its habitability of crew, the current vibration level of navy vessel was examined and the standard of navy vessel's environmental vibration was investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.294-297
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• 2014

A Shipboard power system consists of three or four diesel generator sets connected to a grid. In case of dual fuel diesel generator sets employed LNG ship as a prime mover, large amounts of electricity are required for electric propulsion, auxiliary machinery and accommodation facilities. The electrical connection between generators through a network, torsional vibration can lead power swings. In this paper, the influence on the network by the torsional vibration of diesel generator sets in grid operation were studied. The torsional vibration characteristics were investigated and analyzed through theoretical analysis and the vibration measurement and the results were presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.2
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• pp.139-145
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• 2012

The shipboard working environment of navy vessel is very inferior to the ground working environment. For this reason, the crew of a navy vessel suffer from an occupational disease such as lumbar pain, hearing loss, etc. Although standard for navy vessel's environmental vibration is applied, the criterion of the environmental vibration is too high. So it doesn't help to improve habitability of crew. In this study, for improving its habitability of crew, the current vibration level of navy vessel was examined and the standard of navy vessel's environmental vibration was investigated.