• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.267-270
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• 2000

강제가진을 받는 진동장은 직접장과 반사장으로 이루어진다. 직접장은 무한구조요소가 점입력을 받을 때의 해와 같으며, 반사장은 직접장에 의해 발생되는 1차 반사파 및 추가로 발생하는 무수한 반사파들의 합으로 나타낼 수 있다. 본 논문에서는 점가진을 받는 유한한 평판의 단일 주파수 해석을 수행하기 위한 레이추적기법을 연구하였다. 이를 위해, 직접장은 고주파수 가정을 이용하여 원형전달파로 근사화하고. 이 원헝전달파를 다수의 파동관 (wave tube)으로 이산화하였다. 균일한 경계조건과 무시할 만큼의 미약한 굴절효과를 가정하고 경계에서의 정반사 (specular reflection)만을 고려하여, 경계에서의 입사파동관. 전달 및 반사파동관의 기하학적 관계를 제안하였다. 이들 파동관이 평판 내부를 진행하면서 관측점에 미치는 영향들을 합성하여 비교적 정확한 강제진동응답을 얻을 수 있음을 단일 평판의 예제를 통하여 확인할 수 있었다 그러나, 연성된 평판의 경우에는 다소 부정확한 결과를 얻었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1454-1459
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• 2010

This paper presents the comparison of electric field penetration in Bell laboratories and IEC 61000-2-9 standard when HEMP source penetrates through an aperture in a planar conducting plane of infinite extent. HEMP electric field distributions assume in order to interpret this problem. Integral equation is derived and solved by Galerkin's method of moments for calculating the penetrating electric field. It is shown that penetrated electric field of IEC 61000-2-9 standard is greater than the Bell Laboratories waveform in resonance of lower frequency band, but those waveforms are similar in shape to frequency domain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1201-1211
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• 2014

The purpose of this paper is to present the aperture cut-off filter for reduction of electromagnetic field penetration through a slot in conducting screen. The reduction characteristics of electric field penetration by the aperture cut-off filter are considered. In order to establish the concept of the aperture cut-off filter, the integral equation on the slot aperture field distribution is derived and solved by method of moments, and the reduction characteristics of penetration electric fields for the incident plane wave are calculated. The numerical results showed that the aperture cut-off filter for reduction of electric field penetration through the slot can be realized. To check the validity of the concept of an aperture cut-off filter and the theoretical analysis, the calculated electric field penetration of the metallic wall with narrow slot were compared with the experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.767-773
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• 2014

This paper presents the reduction characteristics of electromagnetic penetration through a slit in conducting screen by loaded plate. The FDTD method is used in theoretical analysis. And the characteristics of penetrated electric fields are calculated in terms of length, width, shape, position, and height of the loaded plate to find out how the geometry of plate influences the reduction characteristics of the electromagnetic penetration and shielding effectiveness. The results show that the characteristics of penetrated electric field and shielding effectiveness depend on the geometry of loaded plate. In particular, the optimal geometry of loaded plate which minimize penetrated electric field are verified.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.168-176
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• 2007

The mixture sound speed in bubbly fluids is highly dispersive due to differences of the density and compressibility between bubbles and fluids. The dispersion range in bubbly fluids expands to a higher frequency than the resonance frequency of an air bubble. A theoretical model was developed to compute the reduction of radiation noise that is generated by a force applied on an infinite flat plate using a bubble layer as a compliant baffle. For evaluating the effectiveness of a bubble layer in reducing the structure-borne noise of an infinite elastic plate, the noise reduction levels for various parameters such as the thickness of bubble layers, the volume fractions and the distribution types of bubbly fluids are calculated numerically. The noise reduction effect of an air bubble layer on an infinite flat plate is considerable level and similar to the tendency of dispersion of bubbly fluids. It is recommended that the thickness of a bubble layer should be increased with keeping an appropriate volume fraction of an air bubble for the most effective reduction of the radiation noise.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1094-1099
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• 2012

This paper presents the reduction characteristics of electromagnetic penetration through a slot in conducting screen by loaded plate. The FDTD method is used in theoretical analysis. And the characteristics of penetrated electric fields are calculated in terms of length, width, position, and height of the loaded plate to find out how the geometry of plate influences the reduction characteristics of the electromagnetic penetration. The results show that the characteristics of penetrated electric field depend on the geometry of loaded plate. In particular, the optimal geometry of loaded plate which minimize penetrated electric field are verified.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.433-440
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• 2002

A branched crack in a semi-infinite plate under uniform tension and bending moment is considered in this study By using the superposition, the stress and moment intensity factors for the branched crack subjected to uniform tension and bending moment we evaluated. The stress intensity factors we obtained by using the finite element method and the J-based mutual integral. The moment intensity factors are calculated by extrapolating the values of the moment new the crack tip. Numerical results lot the normalized stress and moment Intensity factors we shown as functions of the ratio of branched crack length to main crack length and the branching angle.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1647-1652
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• 2011

This paper presents the shielding effectiveness for the IEC 61000-2-9 standard when HEMP source penetrates through an aperture in a planar conducting plane of infinite extent. An integral equation is derived and solved by applying Galerkin's method of moments for calculating the electric shielding effectiveness. The electric shielding effectiveness is examined based on changing the aperture length and width. It is shown that the electric shielding effectiveness is suddenly decreases as the aperture width of 0.4 ~ 0.45${\lambda}$. It is also found that the penetrated electric field for the IEC 61000-2-9 incident field is different from the Bell Laboratory incident field, but the frequency characteristic of the electric shielding effectiveness becomes the same shape.

• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.219-226
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• 2015

In this paper, derivation of the STL (Sound Transmission Loss) of a square plate installed in an impedance tube is discussed using an analytic method. Coupled motion of the plate vibration and acoustic field is considered. Vibration of the plate and pressure field inside the tube are expressed in terms of the infinite series of modal functions. Under the plane wave assumption, it is shown that consideration of the first few modes yields sufficiently accurate results. When the boundary of the plate is clamped, vibration mode is assumed as a multiplication of the beam modes corresponding to the crosswise directions. The natural frequencies of the clamped plate are calculated using the Rayleigh-Ritz method. It is found that the STL shows a dip at the lowest natural frequency of the plate, and increases as the frequency decreases below the natural frequency. Comparison of the result in this paper with the STL obtained by measurements and FE computations in the reference shows an excellent agreement.

• Journal of KSNVE
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• v.6 no.5
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• pp.617-624
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• 1996

Finite Element Method(FEM) is one of the most popularly used method in analyzing the dynamic behaviors of structures. But unless the number of finite elements is large enough, the results from FEM are somewhat different form exact analytical solutions, especially at high frequency range. On the other hand, as the Spectral Element Method(SEM) deals directly with the governing equations of structures, the results from this method cannot but be exact regardless of any frequency range. However, despite two dimensional structures are more general, the SEM has been applied only to the analysis of one dimensional structures so far. In this paper, therefore, new methodologies are introduced to analyze the two dimensional plate structure using SEM. The results from this new method are compared with the exact analytical solutions by letting the two dimensional plate structure be one dimensional and showed the dynamic responses of two dimensional plate by including various waves propagated into x-direction.