• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.25-31
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• 2011

The performance of fan for engine room of ship is absolutely important when it take into consideration work efficiency, work condition, and the performance of various equipments. Fan performance test should be carried out during sea trial to satisfy owner's requirement as above mentioned. We have considered various values to affect fan test result. In here, various values are to be silencer, fan inlet shape, and arrangement of fan room. In general, the shapes of fan inlet is overall circular type because of the shapes of axial fan. So, all vessels built at SHI have been applied fan inlet of circular type. And now, in order to reduce sound of noise from supply fan, big silencer often has been installed at high value vessels. In this case, the capacity of supplied air can be insufficient due to silencer which is an obstructer about air flow. In this paper, we have studied the performance of fan through comparison between a circular shape and a square shape of fan inlet. We also compare with CFD results and experimental results.

• 한국음향학회지
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• 제32권5호
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• pp.402-407
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• 2013

본 논문은 인접한 두 격실의 매질이 다를 때 공통 벽을 통한 음파의 전파를 해석한 내용을 다루었다. 통계적 에너지해석법(statistical energy energy)을 사용하여 두 격실의 음향에너지와 벽의 진동에너지간의 에너지 평형을 고려하였으며 소음원실의 음압이 벽을 투과하는 성분 외에 벽의 구조소음으로 인한 음의 방사(radiation)가 수음원실의 음압에 미치는 영향을 검토하였다. 예제로 선박의 엔진실과 물탱크가 크기 $8.4{\times}4$ m인 강판을 사이에 두고 접한 경우를 해석하였다. 강판의 임계주파수(critical frequency)가 관심주파수대역보다 큰 경우 63 Hz이하의 저주파수대역을 제외하고 음파의 전달은 강판을 투과하는 성분에 의해 주로 결정되며 강판의 구조소음에 기인한 방사소음은 무시할 정도로 기여도가 작음을 확인하였다.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.152-159
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• 2005

The method of induction noise reduction can be classified by using passive control or active control method. However, the passive control method has a demerit to reduce the effect of noise reduction to low frequency (below) 500Hz) range and to be limited in a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used in LMS (Least-Mean-Square) algorithm because it can obtain the complex transfer function easily in real-time. Especially, Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm could not match if the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. So, in order to solve the problem in this study, the Moving Bandpass Filter(MBPF) was proposed and implemented. The ANC using MBPF for the reduction of the induction noise shows that more noise reduction as 4dB than without MBPF.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.551-554
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• 2005

The method of the reduction of the automotive induction noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the LMS (Least-Mean-Square) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm goes bad when the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. Thus Normalized FXLMS algorithm was developed to improve the control performance under the rapid acceleration. The advantage of Normalized FXLMS algorithm is that the step size is no longer constant. Instead, it varies with time. But there is one additional practical difficulty that can arise when a nonstationary input is used. If the input is zero for consecutive samples, then the step size becomes unbounded. So, in order to solve this problem. the Correlation FXLMS algorithm was developed. The Correlation FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Correlation FXLMS Is presented in comparison with that of the other FXLMS algorithms based on computer simulations.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.195-203
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• 2002

In the engine room and the aft part areas of the ship, there exist so many tank structures contacting with fresh water or sea water or oil. If these structures exhibit excessive vibrations during the sea trials, it takes a lot of cost, time and effort to improve vibration situation because the reinforcement work requires emptying the fluid out of the tanks, additional welding and special painting. It is therefore very important to predict a precise vibration characteristics of the tank structures at the design stage, however it is not easy to estimate vibration characteristics of the structures because of difficulties for accurate evaluation of the added (or virtual) mass effect due to the fluid inside the tank. In this paper, numerical and experimental approaches have been performed to present same fundamental data necessary for anti-vibration design of tank structures contacting with fluid, by investigating vibration behaviors of rectangular tank structure for various water depths.

• 수산해양기술연구
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• 제28권4호
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• pp.412-417
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• 1992

In full-speed cruising, the airborne sound pressure levels are measured from 11 small fishing boats operated around Cheju Island. In these measurement, 9 measuring positions are selected in each fishing boats. The results of measurements and analyses are as follows: 1. The sound pressure levels in FRP boats are higher than those in wooden boats. 2. The highest sound pressure level is 112dB(A) at the engine room in C boat, while the lowest one is 72dB(A) at the front deck in K boat. 3. The highest sound pressure level is shown to be in the frequency band less than 500Hz. 4. The highest sound pressure level is shown to be in the frequency band less than 500Hz. 5. Through all 9 positions, the sound pressure levels are higher in B and C boat and lower in E and K boats.

• 한국실내디자인학회논문집
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• 제15권1호
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• pp.158-165
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• 2006

The space of leisure boats & yachts is formed by interior design elements and shapes are formed by combination of those elements. By means of configuration of the design elements, space is made in a ship and patterns in an inside space are made through production. These space can be categorized as (1) cabin(common cabin, staterooms, one-cabin), (2) salon, (3) galleys & dinette, (4) heads(showers, toilets, bidets, sinks), (5) cockpit, (6) wheelhouses, navigation stations, (7) fore peaks, (8) engine room, (9) deck etc. Interior materials are classified into (1) walls(bulkheads & lining wall), (2) floors(sole), (3) ceilings(overheads), (4) doors & windows, (5) furniture, (6) lightings and (7) Hardware & decoration in large, medium and small sizes, which constitute interior design elements of a leisure boat & yacht. The materials used in leisure boats & yachts have properties of lightweight, noise and vibration resistance, fire & flame retardant, stability, strengths, lifespan, appearance and special operation in construction.

• 해양환경안전학회지
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• 제29권6호
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• pp.620-627
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• 2023

선내 소음은 선원의 거주성과 건강을 위한 중요한 요소 중의 하나로, 선내 소음을 줄이기 위한 노력이 활발하게 진행되고 있다. 소음 저감 방법에는 수동소음제어(PNC) 방법과 능동소음제어(ANC) 방법이 있다. 자동차, 항공기와 달리 선박에서는 ANC를 이용한 소음 저감 대책이 미미한 실정이다. 본 연구는 능동소음제어(ANC)와 같이 방음판과 고주파진동원을 이용하여 기관실에 발생한 소음을 줄이고자 하였다. 이를 위해 아크릴 상자를 이용하여 실험 모형을 만들었고, 4가지 조건별로 소음 저감 효과를 측정하였다. 실험 결과는 다음과 같다. 첫째, 방음판은 55 dB ~ 85 dB까지 모든 범위에서 소음 저감 효과가 있었다. 고주파진동원은 낮은 소음에서 효과가 없었으나, 70.8 dB(A)과 85 dB(A)와 같은 높은 소음에서는 효과가 있었다. 둘째, 방음판과 고주파진동원을 동시에 사용하는 경우에는 최대 -2.2 dB(A) 만큼의 소음 저감 효과가 있었다. 본 실험의 결과는 아크릴판으로 제작한 실험모형에서 얻은 결과로 철판으로 된 실제 선박과 다를 수 있다. 추후 연구에서 실제 선박에서 사용하는 철판(재질과 두께, 구조를 고려)을 이용하여 실험하고자 한다. 이 연구가 선박에 승선하는 선원들의 거주성 향상과 건강 증진에 도움이 되기를 기대한다.

• 한국음향학회지
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• 제21권8호
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• pp.708-718
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• 2002

본 연구에서는 진동-음향계에서 방사되어 생성된 일반 근접장에서 음향 인텐시티 기법을 이용해 소음원을 파악하는 방법의 문제점에 관하여 논한다. 이를 위해 자동차나중장비의 엔진실을 모사하는 3차원 구조물 모델을 고려한다. 실제 상황과 유사하도록 모델에는 음원들이 복잡한 형상의 표면에 상호 연관성이 있는 또는 없는 형태로 분포한다. 즉, 음원들은 음향학적으로 단단한 상자들에 의해 형성된 좁은 공간으로 연결되어 있다. 따라서 반사가 심한 음장에 면한 표면에 배치되어 있으며, 전체 구조의 바닥 부분은 하부의 바닥과 작은 틈새만큼 떨어져 있다. 음향 경계요소법을 이용하여 근접 음장과 내부 음장의 인텐시티를 계산한다. 주어진 음원들간의 상대적 위상, 주파수, 위치에 따른 효과를 조사하였고, 그 결과를 등인텐시티선도, 벡터도 및 에너지 유선으로 표현하였다. 현장에서 종종 행해지는 바와 같이, 예를들어 엔진룸 상부에서 인텐시티를 측정하여 음원을 조사하는 것과 같은, 반사장이 강한 음장에서 음향 인텐시티 기법을 적용하여 음원탐색을 시도할 경우 가짜 음원이 검색될 수 있음을 보였다. 이와 같은 음장에서 정확한 결과를 얻기 위해서는, 음원탐색 수행 전에 음장의 리액티비티에 대한 조사가 먼저 필요하며, 측정을 시행하기 전에 음장의 리액티비티를 없애거나 대폭적으로 줄이는 작업이 선행되어야 할 것이다.

• 대한조선학회논문집
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• 제49권2호
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• pp.158-163
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• 2012

Recently, reducing underwater radiated noise (URN) of ships has become an environmental issue to protect marine wildlife. URN of ships can be predicted by various methods considering its generating mechanism and frequency ranges. For URN prediction due to ship structural vibration in low frequency range, the fluid-structure interaction analysis technique based on finite element and boundary element methods (FE/BEM) is regarded as an useful technique. In this paper, URN due to a double bottom-shaped structure vibration has been numerically investigated based on a coupled method of FE/BEM to enhance the prediction accuracy of URN due to the vibration of real ship engine room structure. Acoustic radiation efficiency and URN transfer function in case of vertical harmonic excitation on the top plate of double bottom structure have been evaluated. Using the results, the validity of an existing empirical formula for acoustic radiation efficiency estimation and a simple URN transfer function, which are usually adopted for URN assessment in initial design stage, is discussed.