• 한국정보통신학회논문지
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• 제15권9호
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• pp.1847-1853
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• 2011

실내 전파 채널 해석은 고전적으로 경로추적법이 많이 이용되었으나, 이 논문에서는 3차원 전파해석법인 시간영역 유한차분법을 이용하여 3차원 실내 구조에 대하여 채널 모델링하였다. 시간영역 유한차분법의 여기신호로는 평면파를 이용했으며, 이 때의 평면파의 구성은 TF/SF법을 사용했다. 그리고 흡수경계조건으로는 7개의 흡수층을 사용한 완전정합층법을 이용했다. 실내 채널 모델링의 시뮬레이션을 위한 거실은 벽돌, 도체, 유리, 콘크리트로 이루어졌다. 거실에 가구가 있는 경우와 없을 때에 대하여 각각 시뮬레이션 하였다. 시뮬레이션 결과로 실내 전파 환경에서의 다중경로에 의한 페이딩 현상을 확인할 수 있었으며, 수신기 설계에 도움이 되는 초과지연 평균과 실효 지연 확산을 계산할 수 있었다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.440-444
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• 2006

In this paper an analytical study is carried out to improve the capacity of absorbing boundary using dashpot, one of the most widely used absorbing boundaries in FEM. Using harmonic plane wave equation, absorbing boundary condition is modified to maximize its capacity according to the incident angle. Validity of the modified absorbing boundary conditions is investigated by adopting the solution of Miller-Pursey which is the solution for the wave propagation in semi-infinite elastic media, and the absorption ratio is calculated according to various Poisson's ratios.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.743-748
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• 2010

The stability forecasting of rock slope is more difficult than soil slope because catching the sign of failure in monitoring is not easy and deformation of the rock is small in failure process. But in the rock slope, there is small deformation like crack propagation in rock itself and it accumulates gradually in failure process. If it is possible to detect the small change in the rock slope, we can know the failure time exactly. Because the individual signal is gathered in the acoustic emission monitoring, it is possible to monitoring the slope if many sound signal is accumulated. Detection test of acoustic emission was performed. Uniaxial, two types of bending test, and two plane shear test were done with various cement paste sample. Wave propagation velocity of uniaxial test sample was increased with curing time. Wave Analysis give us the result that there is a AE sign signal before the failure, the AE count is suddenly increased. And frequency level 125kHz before failure is changed to level 200-250kHz after failure. In two plane shear test we can catch the AE signal and can know the failure type from wave shape. Monitoring test site is tunnel slope in Hongcheon but special signal is not collected.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.258-263
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• 1999

In this study, the numerical and experimental investigations were conducted to understand ultrasonic wave propagation and to evaluate the degree of fiber waviness in thick composites nondestructively. The path, energy and traveling time of insonified wave were predicted by adopting the ray and plane wave theories. In the analysis, the composites were assumed to have continuous fiber with sinusoidal waviness in a matrix and were modeled as stacks of infinitesimally short length off-axis elements with varying fiber orientation along the length direction. From the experiments on the specially fabricated thick composite specimens with various degrees of uniform fiber waviness, the energy distributions of received wave were obtain for the various positions of transmitter. It was observed that the energy of wave was converged to the adjacent peaks of fiber waviness. The location where maximum energy of wave was detected from the experiments showed good agreement with the location obtained from theoretical predictions. Finally, the test procedure was Proposed to evaluate fiber waviness in thick composites by considering the energy of wave and relative distance between transmitter and receiver.

• Journal of Advanced Marine Engineering and Technology
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• 제20권1호
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• pp.56-66
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• 1996

In this study, the characteristics of generation and propagarion of transient wave induced in the assembly of four collecting plate upon the propagation of waves are analyzed. Also double exposure holographic inteferometry using ruby pulse laser is built in order to investigate the propagation of transient waves generated by impact load. When impact load was applied at edge of connecting band, the vibration of collecting plates was generated from the contact points between collecting plate and band which connects four collecting plates. Waves generated from the lower part and those reflected from the upper part were mixed as time went on and then formed very complex shapes. Also, when impact load was aplied at center of collecting plate, the waves propagating across the convexo-concave plane were reflected partly at curved section. Therefore the vibration amplitude was decreased as the transiet waves were propagated through the convexo-concave plane.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.18-22
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• 2003

In this thesis, Middle frequency wave propagation modeling is studied for the varies mountain geography the experimented middle frequency propagation model is researched in a shot time to analyze the broad area that consists of mountains. Due to the Sommerfeld - Norton model which is used broadly the middle frequency propagation model to analyze the broad area in a short time is proposed introducing the newly attenuation parameter of the experimental results on the basis of actual experiments at the mountain configuration regardless of the area of mountain, plane, sea etc.

• 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.

• 비파괴검사학회지
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• 제28권3호
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• pp.245-253
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• 2008

A precise description of the material is a key point to obtain reliable results when using wave propagation codes. In the case of multipass welds, the material is very difficult to describe due to its anisotropic and heterogeneous properties. Two main advances are presented in the following. The first advance is a model which describes the anisotropy resulting from the metal solidification and thus the model reproduces an anisotropy that is correlated with the grain orientation. The model is called MINA for modelling anisotropy from Notebook of Arc welding. With this kind of material model1ing a good description of the behaviour of the wave propagation is obtained, such as beam deviation or even beam division. But another advance is also necessary to have a good amplitude prediction: a good quantification of the attenuation, particularly due to grain scattering, is also required as far as attenuation exhibits a strong anisotropic behaviour too. Measurement of attenuation is difficult to achieve in anisotropic materials. An experimental approach has been based both on the decomposition of experimental beams into plane waves angular spectra and on the propagation modelling through the anisotropic material via transmission coefficients computed in generally triclinic case. Various examples of results are showed and also some prospects to continue refining numerical simulation of wave propagation.

• 한국해안·해양공학회논문집
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• 제21권2호
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• pp.117-126
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• 2009

억류파를 제외한 수정 완경사파랑식과 고유함수 전개법의 평면파 근사식에 대한 정밀도를 검토하기 위해 다수의 수치실험 결과를 제시하였다. 본 연구에서 두 해석해가 사용되었으며 하나는 수정 완경사파랑식에 대한 Porter(2003)의 해이고 다른 하나는 평면파 근사식에 산란체법을 적용한 서(2008a)의 해이다. 급변 지형에서의 파랑변형에 대한 기존 결과와의 직접 비교를 통해 평면파 근사식 모형이 수정 완경사파랑식 보다 잘 기술하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.455-468
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• 2019

The present article is aimed at studying the reflection phenomena of plane waves in a homogeneous, orthotropic, initially stressed magneto-thermoelastic rotating medium with diffusion. The enuciation is applied to generalized thermoelasticity based on Lord-Shulman theory. There exist four coupled waves, namely, quasi-longitudinal P-wave (qP), quasi-longitudinal thermal wave (qT), quasi-longitudinal mass diffusive wave (qMD) and quasi-transverse wave (qSV) in the medium. The amplitude and energy ratios for these reflected waves are derived and the numerical computations have been carried out with the help of MATLAB programming. The effects of rotation, initial stress, magnetic and diffusion parameters on the amplitude ratios are depicted graphically. The expressions of energy ratios have also been obtained in explicit form and are shown graphically as functions of angle of incidence. It has been verified that during reflection phenomena, the sum of energy ratios is equal to unity at each angle of incidence. Effect of anisotropy is also depicted on velocities of various reflected waves.