• 대한기계학회논문집A
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• 제30권8호
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• pp.949-956
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• 2006

The method of Greenwood and Williamson is extended to obtain a solution to the coupled non-linear problem of steady-state electrical and thermal conduction across a crack in a conductive layer, for which the electrical resistivity and thermal conductivity are functions of temperature. The problem can be decomposed into the solution of a pair of non-linear algebraic equations involving boundary values and material properties. The new mixed-boundary value problem given from the thermal and electrical boundary conditions for the crack in the conductive layer is reduced in order to solve a singular integral equation of the first kind, the solution of which can be expressed in terms of the product of a series of the Chebyshev polynomials and their weight function. The non-existence of the solution for an infinite conductor in electrical and thermal conduction is shown. Numerical results are given showing the temperature field around the crack.

• 한국광학회지
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• 제14권2호
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• pp.142-145
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• 2003

광 아이솔레이터의 제작을 위해 비가역적 위상변위 효과를 갖는 자기 광학물질을 클래딩 충으로 활용한 무한 평면 광도파로의 비가역적 위상변위 특성을 1.55 $\mu\textrm{m}$ 파장에서 계산하였다. 본 연구에서 사용된 무한 평면 광 도파로의 구조는 클래딩 충으로 자기 광학 물질인 Ce:YIG와 LNB(LuNdBi)$_3$(FeAl)$_{5}$)$_{l2}$)가 사용되었고, 각 각의 고유 패러데이 회전 Θ$_{F}$는 1.55 $\mu\textrm{m}$ 파장에서 4500$^{\circ}$/cm, 500$^{\circ}$/cm이다 가이딩 층은 1.3Q와 InGaAs로 이루어진 다중 양자 우물 구조를 사용하였다. 클래딩 층을 지나는 감쇄 전계에 따른 영향을 조사하기 위하여 기판의 굴절률이 InP와 공기의 굴절률을 갖는 경우에 대하여 도파 모드를 계산하였다. 여러 광 도파로 구조에서 비가역적 위상변위가 90$^{\circ}$가 되는 위상 변위기의 크기가 최소가 되는 길이와 최적화된 가이딩 충의 두께를 구하였다.다.다.다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.35-35
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• 2002

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.106-110
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• 2004

Generally, flow around a bluff body such as a circular cylinder is complicated compared with that around a streamlined body because of the existence of separated shear layers. Long bluff body such as a flat blunt plate is more complicated than short bluff body, because of separated-and-reattaching flow on the after bodies.(omitted)

• 대한기계학회논문집B
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• 제24권10호
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• pp.1326-1334
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• 2000

The oscillatory excitation with a Strouhal number of 2.65 ncar the stagnation zone of hemispherical nose model was employed to control the laminar separation bubble and the transition to turbulence. The effects of oscillatory excitation upon the separation bubble and the transition were addressed in terms of kurtosis/skewness and time-frequency analyses. The measured noise spectrum of radiated sound from the turbulent boundary layer on the axi-symmetric infinite cylinder is compared with that by Sevik's wave-number white approximations. The noise sources in TBL on axi-symmetric cylinder and the caling of their far-field sound are also discussed.

• 한국음향학회지
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• 제15권2호
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• pp.101-104
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• 1996

40~100cm 수심에 평탄한 모래층으로 구성된 천해를 1/1,000 모형으로 축소시킨 무향 수조를 제작하여 Pekeris 모델에 의한 normal mode 관측 실험을 수행하였다. Continuous mode의 공진이 임계각 가까이에서 일어나지 않도록 수심과 진동수를 조절하였으며, 이 때의 실험자료들은 음원으로부터 거리가 대략 수심의 10배 이상일 때 discrete modes의 합으로만 구성된 이론식과 잘 일치하고 있음을 보여주고 있다.

• Advances in nano research
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• 제7권6호
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• pp.391-403
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• 2019

In this article the frequency response analysis of curved magneto-electro-viscoelastic functionally graded (CMEV-FG) nanobeams resting on viscoelastic foundation has been carried out. To this end, the study incorporates the Euler-Bernoulli beam model in association with Eringen's nonlocal theory to incorporate the size effects. The viscoelastic foundation in the current investigation is assumed to be the combination of Winkler-Pasternak layer and viscous layer of infinite parallel dashpots. The equations of motion are derived with the aid of Hamilton's principle and the solution to vibration problem of CMEV-FG nanobeams are obtained analytically. The material gradation is considered to follow Power-law rule. This study thoroughly investigates the influence of prominent parameters such as linear, shear and viscous layers of foundation, structural damping coefficient, opening angle, magneto-electrical field, nonlocal parameter, power-law exponent and slenderness ratio on the frequencies of FG nanobeams.

• 대한설비공학회지:설비저널
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• 제17권4호
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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.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.384-391
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• 2005

Three dimensional finite difference elastic wave model was developed to estimate the feasibility of surface wave applications in geotechnical problems. The wave motions calculated by the developed program in this study shows good agreement with well known analytic solutions. The surface wave motions calculated from layered dam type structure can be interpreted as a infinite layer structure using dispersion curve but it is need a special source of which high energy in frequency band lower than 10 Hz to get information of physical properties in few tens meter deep. The source which has high energy in the low frequency band, however, can give defect on dam and this will make some limitation in real field applications. The dispersion curves calculated from the surface wave motion of homogeneous and center core type dam models will give rise to fatal errors if the conventional infinite layer structure used in their interpretation because the surrounding materials and boundaries of dam make some distortion in dispersion curve of surface wave. So it is strongly recommended to use three dimensional inversion model for correct interpretation and estimation of physical properties of dam materials.

• 터널과지하공간
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• 제4권1호
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• pp.17-23
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• 1994

This study consists of two procedures on back analysis and forward analysis which is a basic tool of the former. For a safe and economical construction of underground structures, it is required to identify the structural parameters and analyze the structural behavior as exactly as possible. In this paper, a boundary element method to analyze the behavior of multi-alyered underground structures is studied, in which body forces and initial stresses are considered. That is, each layer is discritized into subregions using infinite fundamental solutions, and terms of body forces and initial stresses are transformed into boundary integral where the applied direct integral method is used. And the system of equations containing body forces and initial stresses are considered. That is, each layer is discritized into subregions using infinite fundamental solutions, and terms of body forces and initial stresses are transformed into boundary integral where the applied direct integral method is used. And the system of equations containing body forces and initial stresses are composed, then the method to solve unknowns is used with applying compatibility and equilibrium conditions between interfaces. As well, the direct search method is applied in back analysis problems. By Powell's method as a technique to search unknown parameters, assuming displacements calculated from boundary element analysis as in-situ displacements, elastic moduli and initial stresses are presumed. As consequences of this study, the results of boundary element analysis of the behavior of multilayered structure considering body forces and initial stresses are agreed with those of finite element analysis. And results of back analysis of elastic moduli and initial stresses in each layers are agreed with exact values with a little difference. Therefore, it is known that this study can be efficiently applied for analyzing the behavior of underground structures including back analysis problems.