• Journal of KSNVE
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• v.5 no.4
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• pp.537-542
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• 1995

In this paper the method of modeling and optimization for the joint of the vehicle structure is proposed. First it is described that the method of substituting equivalent beam elements to spring elements for the joint. The stiffnesses of the spring elementsare calculated using the section properties of equivalent beam elements. To get required dynamic characteristics section properties of equivalent beam element are set to design variables and optimized. The study shows that joint stiffnesses can be effectively determined in designing vehicle structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.890-895
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• 2002

The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous investigators. The analogy error is demonstrated by the corrected equivalent electroacoustic circuit approach in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.952-955
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• 2007

경량충격음레벨을 평가하기 위해서는 수음실의 잔향시간을 측정하여 규준화 바닥충격음레벨을 구하여야 한다. 본 논문에서는 규준화 바닥충격음레벨과 표준화 바닥충격음레벨을 구할 때 고려하는 보정레벨을 중심으로 등가 흡음력을 결정하는 잔향시간과 수음실의 체적을 변수요인으로 분석하였다. 그 결과 측정된 잔향 시간은 공간에 관계없이 기준보다 2배 이상 길게 나타났고, 등가 흡음력은 기준보다 침실의 경우 1/2 정도 작지만 거실의 경우 기준과 거의 유사하게 나타나 침실의 경우 두 보정레벨이 유사하지만 거실의 경우 전자가 후자보다 낮게 보정되는 것으로 나타났다.

• Journal of the Korean Society for Railway
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• v.2 no.3
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• pp.26-35
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• 1999

The acoustic power reduction method can be used to design a quiet structure. To calculate the acoustic power radiated from a vibrating structure, the dynamic responses have to be determined. It is not easy to analyse the structure composed of the corrugated panels because of the structural complexity and the long analysing time. To make up for these defects, the equivalent orthotropic panel is presented. Also the acoustic power prediction method of the vibrating structures is proposed. As examples, the equivalent material properties of the corrugated plates are obtained and the acoustic powers of the floor structure are calculated at several frequency regions for the Korean High Speed Train.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.387.2-387
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• 2002

The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous researchers. The analogy error is demonstrated by the corrected equivalent electroacoustir circuit approach proposed en this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.51-55
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• 1995

본 연구에서는 회전동력전달계의 진동특성을 해석하고 이를 설계자료로 이용하기 위하여, 계 전체의 유효강성행렬 (effective stiffness matrix)을 실험적으로 결정할 수 있는 방법을 제안하였다. 이것은 비교적 측정이 용인한 관성행렬이 알려져 있다고 가정한 경우 기존의 선형 모델링을 그대로 이용하고, 위의 모든 기계요소의 해석이 불가능한 강성들을 포함한 등가강성(equivalent stiffness)으로 구성된 계의 유효강성행렬을, 실험에 의해 얻어진 계의 여러 작동상황과 이에 따른 고유진동수에 매칭(matching)시켜 결정하는 것이다. 또한, 이의 검증을 위하여 유성기어와 클러치로 이루어진 가상의 동력전달계를 구성하고 이의 시뮬레이션 결과를 이용하여, 유효강성 결정법을 통해 얻어진 등가강성들과 실제값들의 비교함으로서 그 신뢰도를 추정하였다.

• Journal of KSNVE
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• v.9 no.3
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.643-648
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• 2011

This paper deals with the ESM(equivalent source method) with the continuation of acoustic near-field for NAH(near-field acoustic holography) to overcome the finite measurement aperture effect and reconstruct the normal velocity on an arbitrarily shaped structure surface. The continuation method is an extension of the measured sound field into a region outside and is based on the Green's function relating acoustic quantities on the two conformal surfaces. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces. The ESM is an alternative approach of BEM-based NAH for the reconstruction on a general structure. In ESM the acoustic field is represented by a set of point sources located over a surface that is close to the structure surface. The simulation results of this study shows that the reconstruction error of particle velocity on the source surface is 11% and 16% for planar and cylindrical sources separately.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.452-456
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• 2006

The critical speeds and mode shapes are most important to determine the behaviors of rotor in designing rotating machinery. As the capacity and span of turbine-generator increases, the turbine-generator system is composed of many components such as bearings, pedestal, turbine and hood and so on. Also, it is getting flexible and has many critical speeds. Especially, as the characteristics of bearing-pedestal are very complicated, they affect the entire vibration characteristics of turbine-generator system. In this paper, it is observed how to determine the equivalent dynamic stiffness of bearing-pedestal by analytical and experimental method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.516-519
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• 2012

This study proposes a method of an equivalent bell model in order to tune the beat period of a Korean bell. In a Korean bell having a slight asymmetry, each circumferential mode splits into a mode pair which has a slight difference in frequency, and the interaction of the mode pair makes a beat in vibration and sound. An equivalent bell model which consists of an axi-symmetric bell and an equivalent point mass, has the same mode property as in a real bell. The equivalent bell model is constructed by the finite element analysis based upon the theory of a revolutionary shell Using the equivalent bell model, the beat period is predicted when the bell thickness is locally decreased to improve the beat property. The predicted result is verified by experiment on a test bell. The proposed method is useful to save the time required for tuning the beat period of a large bell.