• Computational Structural Engineering
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• v.8 no.1
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• pp.147-160
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• 1995

Based on the weighted residual concept[4], a three-dimensional plate theory is derived using a Fourier series expansion of a dependent variable and a weighted residual approximation of the basic elasticity equations. The weighted residual equilibrium equations of the plate are expressed in terms of weighted displaced quantities, and the results are then interpreted by means of a potential energy functional. The potential energy expression is used to develop a finite element implementation. For illustrative purposes, the application of the theory to a strip plate is considered and two numerical examples of a cantilever and a simply-supported strip plate are studied.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.2
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• pp.150-160
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• 2002

The free vibration characteristics of the triple cylindrical shells filled with fluid are investigated. The triple cylindrical shells are filled with compressible fluid. The boundary condition is clamped at both ends. Analytical method is developed to evaluate natural frequencies of triple cylindrical shells using Sanders' shell theory and courier series expansion by Stokes' transformation. Their results are compared with those of finite element method to verify the validation of the method developed. The modal characteristics of shells filled with fluid at region 1, 2 and 3 are evaluated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.5
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• pp.440-446
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• 1996

The multiple-ridged circular waveguides is analyzed using Fourier series and the mode matching technique. The enforcement of the boundary conditions yields the simultaneous equations for the field coefficient inside the waveguides. The simultaneous equations are solved to represent a dispersion relation in an analytic series form. The numerical computation is performed to illustrate the behavior of the cutoff wavenumbers in terms of number, length and angle of ridges. The presented series solution is exact and rapidly-convergent so that it is efficient for numerical computation. A simple dispersion relation based on the dominant mode analysis is obtained and is shown to be very accurate for most practical applications.

• Journal of Advanced Navigation Technology
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• v.16 no.4
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• pp.635-640
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• 2012

In this paper, The TE (Transverse Electric) scattering problems by a perfectly conducting strip grating over a grounded two dielectric layers are analyzed by applying the conductive boundary condition and the FGMM (Fourier-Galerkin Moment Method) known as a numerical procedure, then the induced surface current density is expanded in a series of the multiplication of the unknown coefficient and the exponential function as a simple function. Generally, the reflected power gets increased according as the relative permittivity ${\epsilon}_{r2}$ and the thickness of dielectric layer $t_2$ of the region-2 in the presented structure gets increased, respectively. The sharp variations of the reflected power are due to resonance effects were previously called wood's anomaly, the numerical results show in good agreement with those of the existing papers.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.315-322
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• 2010

The phase-screen and the split-step Fourier migrations, which are implemented in both the frequency-wavenumber and frequency-space domains by using one-way scalar wave equation, allow imaging in laterally heterogeneous media with less computing time and efficiency. The generalized-screen migration employs the series expansion of the exponential, unlike the phase-screen and the split-step Fourier migrations which assume the vertical propagation in frequency-wavenumber domain. In addition, since the generalized-screen migration generalizes the series expansion of the vertical slowness, it can utilize higher-order terms of that series expansion. As a result, the generalized-screen migration has higher accuracy in computing the propagation with wide angles than the phase-screen and split-step Fourier migrations for media with large and rapid lateral velocity variations. In this study, we developed a 2D prestack generalized-screen migration module for imaging a complex subsurface efficiently, which includes various dips and large lateral variations. We compared the generalized-screen propagator with the phase-screen propagator for a constant perturbation model and the SEG/EAGE salt dome model. The generalized-screen propagator was more accurate than the phase-screen propagator in computing the propagation with wide angles. Furthermore, the more the higher-order terms were added for the generalized-screen propagator, the more the accuracy was increased. Finally, we compared the results of the generalizedscreen migration with those of the phase-screen migration for a model which included various dips and large lateral velocity variations and the synthetic data of the SEG/EAGE salt dome model. In the generalized-screen migration section, reflectors were positioned more accurately than in the phase-screen migration section.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.883-890
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• 2003

In this paper, Electromagnetic scattering problems by a resistive strip grating with tapered resistivity on a grounded dielectric plane according as strip width and spacing, relative permittivity and thickness of dielectric layers, and incident angles of a electric wave are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) Known as a numerical procedure. The scattered electromagnetic fields are expanded in a series of floguet mode functions. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential electric field and the electric current density on the strip. The tapered resistivity of resistive strips varies zero resistivity at strip edges. Then the induced surface current density on the resistive strip is expanded in a series of Chebyshev polynomials of the second kind. The numerical results of the geometrically in this paper are compared with those for the existing uniform resistivity and perfectly conducting strip. The numerical results of the normalized reflected power for conductive strips case with zero resistivity in this paper show in good agreement with those of existing paper.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.152-158
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• 2006

In this paper, electromagnetic scattering problems by a resistive strip grating with zero resistivity at the strip-edges on a grounded 2 dielectric layers according as strip width and spacing, relative permittivity, thickness of dielectric layers, and incident angles of a electric wave are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) known as a numerical procedure. The scattered electromagnetic fields are expanded in a series of floguet mode functions. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential electric field and the electric current density on the strip. The tapered resistivity of resistive strips varies zero resistivity at strip edges. Then the induced surface current density on the resistive strip is expanded in a series of Chebyshev polynomials of the second kind. The normalized reflected power with zero resistivity in this paper show in good agreement with those of existing paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.656-663
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• 2007

In this paper, when a E-polarized plane wave is incident on the grating consisting of tapered resistive strips, electromagnetic scattering is analyzed using the method of moments(MoM). The induced current density of each resistive strip in a grounded double dielectric layer is expected to blow up at both edges. To satisfy this, the induced surface current density is expanded in a series of Chebyshev polynomials of the second kind. The scattered electromagnetic fields are expanded in a series of Floquet mode functions. The boundary conditions are applied to obtain the unknown current coefficients. According to the variation of the involving parameters such as strip width and spacing and angle of the incident field, numerical simulations are performed by applying the Fourier-Galerkin moment method. The numerical results of the normalized reflected power for resistive strips case for several resistivities are obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.913-919
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• 2006

In this paper, TE(transverse electric) scattering problems by a resistive strip grating over grounded dielectric multilayers according to the strip width and grating period, the relative permittivity and thickness of dielectric multilayers, and incident angles of a TE plane wave are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) known as a numerical procedure. The induced surface current density is simply expanded in a Fourier series by using the exponential function as a simple function. Generally, the relected power gets increased according as the relative permittivity and thickness of dielectric multilayers gets increased, the sharp variations of the reflected power are due to resonance effects that take place and were previously called wood's anomallies$^{[7]}$. To verify the validity of the proposed method, the numerical results of normalized reflected power for the uniform resistivity R = 0 as a conductive strip case show in good agreement with those in the existing paper.

• The Korean Journal of Rheology
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• v.10 no.3
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• pp.173-183
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• 1998

본 연구에서는 Advanced Rheometric Expansion System(ARES)를 사용하여 대진폭 진동 전단 변형하에서 발생하는 폴리이소부틸렌(PIB) 농후 용액의 비선형 점탄성 거동을 저 장탄성율과 동적점도의 변형량 의존성 및 응력파형의 fast Fourier transform(FFT) 해석을 통해 고찰하였다. 스트레인 진촉을 단계적으로 증가시키면서 측정한 동적 점탄성으로 부터 저장탄성율 및 동적점도의 선형응답한계를 결정하고 이들에 미치는 각주파수의 영향을 조사 하였다. 그리고 응력파형의 Fourier 전개로부터 유도되는 비선형 점탄성함수를 사용하여 비 선형 거동을 설명하였다. 끝으로 비선형 점탄성 거동의 정도를 나타내는 비선형 거동 지수 를 정의하고 이들에 미치는 각주파수의 영향에 대해 검토하였다. 이상의 연구를 통해 얻어 진 결과를 요약하면 다음과 같다.(1) 선형 응답한계는 고분자 용액의 특성시간의 역수보다 높은 각주파수 범위에서는 일정한 값을 유지하지만 특성시간의 역수보다 낮은 각주파수 영 역에서는 각주파수가 감소할수록 증가한다. (2)선형응답한계 이상의 대변형하에서는 3차비선 형 점탄성 함수 이상의 고차항의 영향이 크게 작용하며 이로인해 비선형 거동이 발생된다. (3) 스트레인 진폭을 단계적으로 증가시키면서 측정한 저장탄성율 및 동적점도의 변형량 의 존성은 응력파형의 Fourier transform으로부터 유도된 1차 비선형 점탄성 함수의 변형량 의 존성을 나타낸다 (4) 저장탄성율 및 동적점도의 변형량 의존성으로부터 유도된 비선형 거동 지수는 탄성적 서질과 점성적 성질에 대한 비선형 특성을 평가하기 위한 유요한 방법으로 인정된다. (5) 비선형 점탄성 거동의 정도를 나탄는 비선형 거동지수는 특정한 각주파수에서 최대치를 가지며 또한 탄성적 거동이 점성적 거동에 비해 더욱 큰 각주파수 의존성을 나타낸다.