• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.768-773
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• 2001

The self-noise from blade cascade at off-design points mainly comes from separated boundary layer and vortex sheddings, and is also dependent on blade shape. If the incidence angle to the cascade increases, the stalling in blades may occur and the noise level increases significantly. The hybrid method using acoustic analogy was employed to compute the far-field noise spectra and directivity patterns from the separated vortex shedding at off-design points of the cascade of impeller. This paper is compared with the experimental data of a stationary cascade in the same conditions. The simulated result is in excellent .agreement with the measured data except th slight under-prediction near the maximum radiation angle for a dipole sound.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• 환경정책연구
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• 제11권3호
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• pp.49-65
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• 2012

도로교통소음은 자동차의 이동 즉 교통량과 통행속도등 도로교통환경과 밀접하게 관련되는바 본 논문에서는 교통류특성과 도로교통소음과의 관계를 분석하고자 몇 가지 문제를 제기하였다 첫째는 "최대 소음이 언제 발생하는가?"라는 문제로 교통량이 많은 첨두시간대에 과연 최대소음이 발생할 것인지를 교통류측면에서 검토하고자 하였다. KHTN 모델을 통해서 LOS를 분석한 결과 실제 최대 소음은 용량상태인 LOSE가 아닌 LOSD에서 발생하는 것으로 나타났다. 이는 실제 첨두시간대에는 교통량은 많지만 통행속도가 낮기 때문에 오히려 첨두시간을 전후하여 최대소음이 발생할 가능성이 높다는 것을 보여준다. 둘째는 교통소음예측에 이용되는 차종별 통행속도 추정에 관한 것으로, 보다 쉬우면서도 정확성을 지닌 통행속도추정기법을 찾고자 하였다. 이를 위해 스케치 플래닝 기법으로 도로용량편람의 '고속도로 기본구간의 속도 교통량 곡선과 서비스수준' 그래프를 이용하는 방법을 제시하였다. 각 설계속도별 추세선 모형식 산정결과 최적의 함수유형은 2차 다항식이며 각각 $R^2$가 0.96이상의 값을 가지고 있어 적합한 모형으로 판단된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.385.1-385
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• 2002

Operational Modal Analysis also known as Ambient Modal Analysis has an increasing interest in mechanical cngineering. Especially on big structures where the excitation and not less important the determination of the forces is most often a problem. In a structure like a wind turbine wing where the modes occur both close in frequency and bi-directional the Ambient excitation has big advantages. (omitted)

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.504-514
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• 2003

We investigate global bifurcation in the subharmonic motion of a circular plate with one-to-one internal resonance. A system of autonomous equations are obtained from the partial differential equations governing the system by using Galerkin's procedure and the method of multiple scales. A perturbation method developed by Kovacic and Wiggins is used to find Silnikov type homoclinic orbits. The conditions under which the orbits occur are obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.704-709
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• 2003

Vibration localization characteristics of repeated mistuned structures are investigated by two ways. The mistuning often creates significant response discrepancies among subcomponents of the repeated structures. As a result of the discrepancies, critical fatigue problems often occur in repeated structures. Therefore, it is of great importance to predict the vibration response of the mistuned repeated structures accurately. In this paper, a simplified model is employed and dimensionless parameters that influence the localization characteristics are first identified. Through the parameter study, the two localization phenomena are investigated and compared.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.139-145
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• 1997

Nowadays, the axial stiffness of crankshaft of long-stroke diesel engine is low compared to that of the old types of engine by increasing stroke/bore ratio and major critical speed might occur within engine operation speed. An axial damper needs to be installed in order to reduce the axial vibration of the crankshaft in the event of reduced or stopped axial damper function are discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.489-494
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• 2003

Vibration localization characteristics of open loop repeated structures with mistuning are investigated in this paper. Mistuning of a periodic structure often creates significant non-uniformity in vibration responses. As a result of the localization, critical fatigue problems often occur in repeated structures. Therefore, it is of great importance to predict the vibration response of the mistuned repeated structures accurately. In this paper, a simplified model for the open-loop repeated structure is introduced and dimensionless parameters which influence the localization characteristics are identified. The effects of the parameters on the localization characteristics are investigated through numerical study.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.214-216
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• 2019

최근 다양한 분야에서 디지털 장비의 사용이 증가함에 따라 영상 및 신호처리의 중요성이 높아지고 있다. 하지만 디지털 신호는 송수신 과정에서 많은 종류의 잡음이 발생하며, 이러한 잡음은 시스템의 최종 출력에 큰 영향을 미친다. 본 논문은 임펄스 잡음과 AWGN이 혼합된 잡음 환경에서 화소 유사성에 따른 잡음 제거를 통해 효과적으로 영상을 복원하는 알고리즘을 제안하였다. 제안한 알고리즘은 잡음 종류에 따라 기준치를 설정하여, 기준치와 유사한 화소에 필터링을 적용하여 최종 출력을 구한다. 시뮬레이션 결과 제안한 알고리즘은 우수한 잡음제거 특성을 나타내었으며, 기존 방법들과 비교하기 위해 PSNR 등을 이용하여 비교 및 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3092-3097
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• 2007

Although noise of a RAC can be reduced effectively by decreasing RPM, condensation problems can occur to reduce reliability of the RAC for low RPM. Thus, this research has been performed to propose a design guideline of the RAC for low-noise RPM with high reliability. The internal and external flows of the RAC have been visualized and analyzed by a PIV technique to solve the condensation problem at an outlet and impeller. Then, the design guideline has been proposed by the analyzed results and confirmed by wind-tunnel and noise tests to reduce the condensation problem. Finally the shapes of the outlet with reduced condensation problem and the impeller with low noise have been obtained in this study.