• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.403-407
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• 2009

It is reported that the heavy weight floor impact noise of a slab system is very sensitive to the location of microphone and impact load. In addition, it is known that the aspect raio, thickness and boundary condition of a slab also have great effect on the noise induced by impact load. However, the effect has been mainly evaluated by experimental test and numerical analysis is nearly performed to verify the effect quantitatively. In this study, the effect of the aspect ratio, thickness and boundary condition on the heavy weight floor impact noise is examined through numerical analysis for simple rectangular slab system. The results show that the thickness and boundary condition have a strong correlation with the noise of the slab, on the contrary, the aspect ratio has little relation with the noise.

• 한국콘텐츠학회논문지
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• 제14권12호
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• pp.555-564
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• 2014

DIBR(Depth Image Based Rendering)을 이용한 영상 합성 시에 발생하는 경계 잡음은 원래 전경 영역에 속하던 화소가 배경으로 흩어져 나와 생성된 잡음이며, 이는 주로 참조 영상과 깊이지도 간 경계 불일치나 참조 영상에서의 블러링 때문에 발생된다. 영상 합성 과정에서 발생된 홀 영역은 일반적으로 주위 화소를 이용하여 채워지게 되므로, 홀에 인접한 경계 잡음은 합성 영상의 화질을 저하시키는 주요 원인으로 작용한다. 이 문제를 해결하기 위해 본 논문은 깊이지도의 전처리를 이용한 새로운 경계 잡음 제거 알고리즘을 제안한다. 기존의 전처리 기법들은 경계 불일치에 따른 경계 잡음의 제거를 위해 참조 영상과 깊이지도의 경계가 일치되도록 깊이지도를 수정한다. 그러나 대부분의 기존 기법들이 신호 기울기 기반의 단순 경계 탐색 알고리즘에 기반을 두고 있어 블러링이 존재하는 경계에서는 탐색 성능의 저하가 나타난다. 제안 알고리즘은 이의 해결을 위해 2단계 경계 탐색을 이용함으로써 이행 영역과 배경 영역 간 경계를 보다 효과적으로 탐색할 수 있는 구조를 제안하였다. 실험 결과를 통해 제안 알고리즘이 기존 알고리즘에 비해 우수한 경계 잡음 제거 성능을 가짐을 보인다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.521-526
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• 2012

It is essential for the accurate time-domain prediction of broadband noise due to turbulence-cascade interaction to develop inflow/outflow boundary conditions to satisfy the following three requirements: to maintain the back ground mean flow, to nonreflect the outgoing disturbances and to generate the specified input gust. The preceding study(1) showed that Perfectly Matched Layer (PML) boundary condition was successfully applied to absorb the outgoing disturbances and to generate the specified gust in the time-domain computations of broadband noise due to interaction of incident gust with a cascade of flat-plates. In present study, PML boundary condition is extended in order to predict steady mean flow that is needed for the computation of noise due to interaction of incident gust with a cascade of airfoils. PML boundary condition is originally designed to absorb flow disturbances superimposed on the steady meanflow in the buffer zone. However, the steady meanflow must be computed before PML boundary condition is applied on the flow computation. In the present paper, PML equations are extended by introducing source term to maintain desired mean flow conditions. The extended boundary condition is applied to the benchmark problem where the meanflow around a cascade of airfoils is predicted. These illustrative computations reveal that the extended PML equations can effectively provide and maintain the target meanflow.

• 한국소음진동공학회논문집
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• 제22권7호
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• pp.685-691
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• 2012

It is essential for the accurate time-domain prediction of broadband noise due to turbulence-cascade interaction to develop inflow/outflow boundary conditions to satisfy the following three requirements: to maintain the back ground mean flow, to nonreflect the outgoing disturbances and to generate the specified input gust. The preceding study showed that perfectly matched layer(PML) boundary condition was successfully applied to absorb the outgoing disturbances and to generate the specified gust in the time-domain computations of broadband noise due to interaction of incident gust with a cascade of flat-plates. In present study, PML boundary condition is extended in order to predict steady mean flow that is needed for the computation of noise due to interaction of incident gust with a cascade of airfoils. PML boundary condition is originally designed to absorb flow disturbances superimposed on the steady meanflow in the buffer zone. However, the steady meanflow must be computed before PML boundary condition is applied on the flow computation. In the present paper, PML equations are extended by introducing source term to maintain desired mean flow conditions. The extended boundary condition is applied to the benchmark problem where the meanflow around a cascade of airfoils is predicted. These illustrative computations reveal that the extended PML equations can effectively provide and maintain the target meanflow.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.489-493
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• 2007

Mmulti-domain noise analysis method using Power Flow Boundary Element Method(PFBEM) has been developed successfully. Some applications are introduced. several examples. PFBEM is a numerical analysis method formulated by applying Boundary Element Method(BEM) to Power Flow Analysis(PFA). PFBEM is very powerful in predicting noise level in medium-to-high frequency ranges. However there are restrictions in analyzing the coupled structures and multi-media. In this paper, an analysis method for multi-domain acoustic problems in the diverse acoustic fields is suggested. And the developed method is applied to the car interior and exterior multi-domain noise analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1056-1061
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• 2001

This paper describes the evaluation of noise influence of residental and boundary areas from power plant noise sources of 1200MW combined cycle power plant. Noise assessments are carried out by based on the ISO 3744, ISO 9613-1 and ISO 9613-2 to predict the noise distribution to satisfy the recommended noise level at specific locations and to calculate properly the octave noise power of main noise sources such as power transformers. air-intakes, stacks.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.791-796
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• 2003

Some basic guidelines for changing non-uniform boundary condition in an acoustically small cavity are presented. In this paper, modal summation technique is used to represent inside sound field. From this formulation, corner effect is defined and proposed. The corner in a cavity is good position for changing boundary condition effectively. Impedance circle with same absorption coefficient is defined to find appropriate impedance of absorptive material for better noise control performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.568-574
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• 2012

Turbulent boundary layer noise is already a significant contributor to sonar self noise. For developing acoustic window of sonar system to reduce self noise, a parametric study of design factors of acoustic window is presented. Distance of sensor array from acoustic window, material and damping layer are studied as design factors to influence in the characteristics of the transfer function of self noise. As the result these design factors make change the characteristics of transfer function slightly. Among design factors the location of sensor array is most important parameter in the self noise reduction.

• 한국멀티미디어학회논문지
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• 제6권3호
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• pp.419-428
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• 2003

어떤 물체 영역의 골격(skeleton)을 얻기 위해 세건화(thinning)하는 과정에서 잔가지(parasitic branch)가 발생하므로, 이러한 것을 효과적으로 제거하기 위한 여러 가지 연구가 이루어져 왔다. 이중에서 잔가지가 한 픽셀 두께의 가지로 나타나는 속성에 착안하여, 윤곽선 추적에 의한 대칭 경로(symmetric path)를 검출함으로써 잔가지를 제거하는 방법이 매우 효과적인 것을 알 수 있었다. 본 연구에서는, 이 방법을 영상 분할이나 연결 요소 추출 등에 의해 구해진 물체 영역의 윤곽선 부분에 나타나는 잡영가지 (noise branch)를 제거하는데 활용할 수 있도록 개선한 방법을 제안한다. 즉, 한 픽셀 두께의 잡영가지 뿐만 아니라, 부분적으로 두 픽셀 이상이 뭉쳐져 둥그스름한 덩어리(잡영블랍, noise blob)를 형성하고 있는 잡영가지도 제거할 수 있는 개선된 방법을 제안한다. 대칭 경로를 찾기 위해 4-8방향 윤곽선 추적 알고리즘을 이용하며, 잡영블랍이 포함된 경우에는 준대칭(quasi-symmetric) 경로를 정의하여 추출한다. 제안한 방법의 시간 복잡도는 윤곽선 픽셀수의 선형 함수로 표현되며, 사용자가 잡영블랍과 잡영가지의 크기를 임의로 설정하도록 하여 융통성있고 다양하게 잡영가지를 제거할 수 있도록 하였다. 실제 형상과 인위적 형상에 대한 실험을 통해 제안된 방법의 유용성을 확인할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.392-398
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• 1998

In order to check the validity of nonlinear normal modes of continuous, systems by means of the energy-based formulation, we consider a beam with a nonlinear boundary condition. The initial and boundary e c6nsl of a linear partial differential equation and a nonlinear boundary condition is reduced to a linear boundary value problem consisting of an 8th order ordinary differential equations and linear boundary conditions. After obtaining the asymptotic solution corresponding to each normal mode, we compare this with numerical results by the finite element method.