• 소음진동
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• 제2권2호
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• pp.107-116
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• 1992

An adaptive signal processing technique is implemented for the active noise cancellation of the plane acoustic wave propagating in a duct. To avoid the instability caused by the acoustic feedback from the control speaker to the detect microphone, an off-line modeling of the acoustic feedback plant is done using the FIR filter. Auxiliary path required for the filtered-x LMS algorithm is modeled as well. Before going into the experiments, a simulation is carried out under the same conditions with experiments. The simulation shows that the longer the length of the adaptive filter is, the better the results are achieved. Experiments have been carried out at lower audio frequency range (50 - 400Hz), and the results are in good agreements with those of simulation study. As a results of this adaptive noise control, around 50dB is reduced for a pure tone noise, and for a bandlimited noise with the bandwidth of 316Hz, a maximum of 30dB noise reduction is attained.

• 대한조선학회논문집
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• 제43권6호
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• pp.647-655
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• 2006

In this paper, submerged body dynamics model in vertical plane which can include the effect of free surface and wave is suggested to simulate the motions of submerged body moving beneath free surface precisely. A controller is designed, which can maintain a constant depth below the mean sea level and minimize the pitch angle. Numerical simulations show that the designed controller is effective on depth keeping and minimizing pitch angle in regular waves and irregular waves.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.399-406
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• 1998

Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the Fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

• Earthquakes and Structures
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• 제9권3호
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• pp.577-601
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• 2015

The thermomagnetic effect on plane wave propagation at the liquid-solid interface with nonclassical thermoelasticity is investigated. It is assumed that liquid-solid half-space is under initial stress. Numerical computations are performed for the developed amplitude ratios of P, SV and thermal waves under Cattaneo-Lord-Shulman theory, Green-Lindsay theory and classical thermoelasticity. The system of developed equations is solved by the application of the MATLAB software at different angles of incidence for Green and Lindsay model. The effect of initial stress and magnetic field in the lower half-space are discussed and comparison is made in LS, GL and CT models of thermoelasticity. In the absence of magnetic field, the obtained results are in agreement with the same results obtained by the relevant authors. This study would be useful for magneto-thermoelastic acoustic device field.

• Steel and Composite Structures
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• 제27권4호
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• pp.439-451
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• 2018

In the present investigation, a plane P (longitudinal) wave is made incident upon a transversely isotropic magnetothermoelastic solid slab of uniform thickness, interposed between two different semi-infinite viscoelastic solids. The transversely isotropic magnetothermoelastic sandwiched layer is homogeneous with combined effects of two temperature, rotation and Hall current in the context of GN Type-II and Type-III (1993) theory of thermoelasticity. The amplitude ratios of various reflected and refracted waves are obtained by using appropriate boundary conditions. The effect of energy dissipation on various amplitude ratios of longitudinal wave with angle of incidence are depicted graphically. Some cases of interest are also deduced from the present investigation.

• 전자공학회논문지D
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• 제35D권12호
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• pp.21-29
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• 1998

E-분극된 평면파가 입사되는, 임의의 쐐기각을 갖는 완전도체쐐기에 대해 파수영역에서의 쌍적분 방정식을 유도하였다. 급수전개된 완전도체쐐기의 정확한 경계면 전자파를 파수영역에서의 쌍적분 방정식에 대입하여 해석적으로 적분함으로써 점근해를 유도하였다. 가상공간에서 적분 결과가 0이 되는 것을 보임으로써 적분과정의 타당성을 보였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.143-150
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• 1999

Elastic wave propagation in a multilayered elastic half-plane is studied by using the Cagniard-de Hoop method. After the unknowns are expressed in terms of the reflection and transmission coefficients in the in terms of the reflection and transmission coefficients in the integral-transformed domains they are assmbled to form the global matrix equation. The inverse Laplace transform of each term is done by applying the Cagniard-de Hoop methods. As a numerical example a four-layered half-plane is considered where a point source is applied to the first layer. The method described in the present study can be used in checking other numerical methods such as FDM.

• 한국광학회지
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• 제2권2호
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• pp.74-82
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• 1991

서로 마주보며 비춰진 원형편극된 두 $TEM_{00}$ 레이저 광속내에 부양된 균질구에 작용하는 광압분포를 조사하였다. 두 레이저 광속의 간섭효과를 고려하여 광압성분의 해석적 표현이 유도되었으며 정상 평면전자기파의 경우와 비교되었다. 광압분포에 대한 수치해석 결과가 제공되었으며 그 물리적 의미가 논의되었다.

• 한국통신학회논문지
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• 제15권3호
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• pp.232-242
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• 1990

외부 평면파에 의해 유기되는 단일 전송선로의 EMI(Electromagnetic Interference) 전류에 관한 Smith의 해석법을 이용하여 연쇄 접속된 전송선로의 부하 EMI전류를 구한다. 동일한 특성 임피던스를 갖는 선로가 연쇄 접속 되었다는 가정하에 수치계산을 하여 Smith의 연구 결과와 비교한 결과 두 결과가 잘 일치함을 확인하였으며, 선로의 폭과 길이가 각각 1/10로 줄어들면 부하 EMI 전류는 약 40dB 정도 감소함을 알 수 있었다.

• 한국통신학회논문지
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• 제22권4호
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• pp.605-610
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• 1997

An analysis method for the electromagnetic scattering of a Tm polarized plane wave from a periodic strip grating over a grounded dielectric slab is considered from the viewpoint of reflection grating problem. The parameters of strip gratings showing Bargg and Off-Bragg blazing phenomena at the frequency of 10GHz are derived teoretically. The strip grating structure is implemented using Aluminum plate(groung conductor), paraffin(dielectric material.epsilon.$_{r}$=2.24), and copper(strip conductor0.08m thickness). The experimental results(reflection power) of Bragg as well as Off-Bragg blazing phenomenon for TM polarized plane wave have been compared with the theoretical results and fairly good agreements between theory and experiment have been observed.d.