• Title/Summary/Keyword: Conductive boundary condition

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Finite Element Analysis on the Improvement of Residual Deformation of the Part After Pulse Laser Welding of Circular Cover (원형 커버의 펄스 레이저 용접 후 부품 잔류변형 개선에 관한 유한요소해석)

  • Kim, Kwan-Woo;Cho, Hae-Yong
    • Journal of Welding and Joining
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    • v.33 no.6
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    • pp.60-66
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    • 2015
  • Molten zone shape of pulse laser welding is affected by welding conditions such as beam power, beam speed, irradiation time, pulse frequency, etc. and is divided into conduction type and keyhole type. It is necessary to design heat source model for irradiation of laser beam in the pulse laser welding. Shape variables and the maximum energy density value of the heat source model are different depending on the molten zone shape. In this paper, pulse laser welding simulation for joining of cylindrical part and circular cover was carried out. The heat source model for pulse laser beam with circular path was applied to the heat input boundary condition, radiative and conductive heat transfer were considered for the thermal boundary condition. For each phase, thermal and mechanical properties according to temperature were also applied to analysis. Analytical results were in good agreement with the molten zone size of specimen under the same welding conditions. So, the reliability of the welding simulation was verified. Finally, the improvements for reducing residual deformation after cover welding could be reviewed analytically.

The Braking Torque Analysis of Eddy Current Brake with the Use of Coulomb′s law and the Method of Image (쿨롬 법칙과 영상법을 이용한 와전류 브레이크의 제동토크 해석)

  • Lee, Gap-Jin;Park, Gi-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.50 no.9
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    • pp.431-437
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    • 2001
  • Since the eddy current problem usually depends on the geometry of the moving conductive sheet and the shape of the pole projection area, there is no general method to find out its analytical solution. The analysis of the eddy current in a rotating disk is performed in the case of time-invariant field to find its analytical solution. As a method to solve the eddy current problem, the concept of the Coulomb charge and image method are proposed with the consideration of the boundary condition. Firstly, the line charge is obtained from the volume charge generated in the rotating disk and Coulomb's law is applied. Secondly, the finite disk radius is considered by introducing an imaginary eddy current to satisfy the boundary condition that the radial component of the eddy current is zero at the edge of the relating disk. Thirdly, the braking torque is calculated by applying Lorentz force law. Finally, the computed braking torque is compared with the measured one As a result, it can be said that the proposed model presents fairly accurate results in a low angular velocity range although a large error is observed as the angular velocity of the disk increases.

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Conjugate Heat Transfer for Circular Absorber in Parabolic Trough Concentrator (PTC형 집열기의 원관형 흡수기에서의 복합열전달)

  • Chung, J.M.;Seo, T.B.;Kang, Y.H.
    • Solar Energy
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    • v.20 no.1
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    • pp.81-89
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    • 2000
  • In the present study, the characteristics of conductive and convective heat transfer occurred in a circular absorber of PTC (parabolic trough concentrator) for medium temperature solar energy utility were numerically investigated. A circular tube was considered as an absorber and the shape of PTC modeled in this study was based on the system that was installed in Korea Institute of Energy Research. Not only convection inside the tube but also conduction through the wall of the tube were analyzed, simultaneously. Circumferentially non-uniform heat flux that was simulated from the non-uniform solar disc model proposed by Jose was applied as thermal boundary condition on the tube surface. And, hydrodynamically fully developed laminar velocity profile was used as the inlet boundary condition and it was assumed that the working fluid was water. And, local heat fluxes at the interface of the tube and the working fluid were calculated for different wall thickness and thermal conductivity of the tube at various Reynolds number. Based on the results, the effects of thermal conduction of the tube on the local heat transfer were investigated.

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Analysis of the Electromagnetic Scattering by a Resistive Strip Grating Tapered Resistivity On a Grounded Dielectric Plane -from Zeores at One Edge to Infinite at the Other Edge- (접지된 유전체층 위에 변하는 저항율을 갖는 저항띠 격자구조에서의 전자파산란 해석 -한쪽 모서리에서 0이고 다른쪽 모서리로 가면서 무한대로 변하는 경우-)

  • Yoon, Uei-Joong
    • The Journal of Information Technology
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    • v.8 no.2
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    • pp.77-84
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    • 2005
  • In this paper, electromagnetic scattering problems by a resistive strip grating with tapered resistivity on a grounded dielectric plane according to strip width and spacing, relative permittivity and thickness of dielectric layers, and incident angles of a electric wave are analyzed by applying the Fourier-Galerkin Moment Method known as a numerical procedure. 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 resistivity of resistive strips in this paper varies from zeroes at one edge to infinite at the other edge, then the induced surface current density on the resistive strip is expanded in a series of Jacobi polynomials of the order ${\alpha}=0.2,\;{\beta}=-0.2$ as a orthogonal polynomials. The numerical results of the geometrically normalized reflected power in this paper are compared with those for the existing 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 papers.

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Heat Transfer with Linearly Anisotropic Scattering Medium in a Plane Layer (두 무한 평면 사이의 선형 이방성 산란 매질에서의 열전달)

  • Byun, K.H.;Smith, T.F.
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.17 no.4
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    • pp.435-441
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    • 1988
  • The purpose of this study is to apply the zone method expressions for a gray, absorbing, emitting, and linearly anisotropic scattering medium enclosed in an infinite plane layer to evaluate heat transfer applications. The medium is assumed to be homogeneous and has a refractive index of unity. The boundary surfaces are opaque and gray, diffusely emitting and reflecting at a constant temperature. Radiative equilibrium condition, combined conductive and radiative heat transfer, and thermal ignition are studied in terms of the governing parameters, and the results are compared with previous studies. Wall heat flux results agree well with those of others. Except for the minor discrepancies observed for some cases, temperature results also agree well with those of previous studies. Good agreement with results from other methods indicates the accuracy of the zone method as well as its compatibility with other modes of heat transfer.

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Analysis of the Electromagnetic Scattering by a Tapered Resistive Strip Grating with Zero Resistivity at the Strip-Edges On a Grounded Dielectric Plane (접지된 유전체층 위에 저항띠 양끝에서 0으로 변하는 저항율을 갖는 저항띠 격자구조에서의 전자파 산란 해석)

  • 정오현;윤의중;양승인
    • 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.

Solution of TE Scattering by a Resistive Strip Grating Over Grounded Dielectric Multilayers (접지된 다층 유전체위의 저항띠 격자구조에 의한 TE 산란의 해)

  • Yoon Uei-Joong
    • 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.

Analysis of the TE Scattering by a Resistive Strip Grating Over a Grounded Dielectric Plane (접지된 유전체 평면위의 저항띠 격자구조에 의한 TE 산란 해석)

  • Yoon, Uei-Joong
    • Journal of Advanced Navigation Technology
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    • v.10 no.3
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    • pp.198-204
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    • 2006
  • In this paper, TE(transverse electric) scattering problems by a resistive strip grating on a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of dielectric layer, 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. The reflected 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 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.

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