• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.59-68
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• 2010

The aim of this work is to analyze high temperature flows around an axisymmetric blunt body taking into account chemical and vibrational non-equilibrium state for air mixture species. For this purpose, a finite volume methodology is employed to determine the supersonic flow parameters around the axisymmetric blunt body. This allows the capture of a shock wave before a blunt body placed in supersonic free stream. The numerical technique uses the flux vector splitting method of Van Leer. Here, adequate time stepping parameters, along with Courant, Friedrich, Lewis coefficient and mesh size level are selected to ensure numerical convergence, sought with an order of $10^{-8}$.

• 대한전자공학회논문지
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• 제24권1호
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• pp.133-139
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• 1987

A phase-locked Channel-Substrate-Planar(CSP) laser arrays is described. Arrays of emitters with weak coupling are operated in a set of discrete modes determined by the number and spacing of the emitters. The interactions between emitters lead to a splitting of the wave-length and gain which are calculated from the coupling strength. Phase-locked arrays has exhibited to CW output-power as high as 80 m W and the highest order mode will have preferred oscillation. A strong hole burning is occurred at p=30m W. The most stable lasing mode is occurred at element spacing S=3.5\ulcornerm and there is no coupling at S>7 \ulcornerm.

• 한국전산유체공학회지
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• 제2권1호
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• pp.21-28
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• 1997

This paper presents a two-dimensional horizontal implicit model to general circulation in estuaries and coastal seas. The model is developed in non-orthogonal curvilinear coordinates system, using the Interpolating Matrix Method (IMM), in combination with a technique of multi-domain. In the propose model, the Saint-Venant equations are solved by a splitting-up technique, in the successive steps; convection, diffusion and wave propagation. The ability of the proposed model to deal with full scale nature is illustrated by the interpretation of a dye-tracing experiment in the Gironde estuary.

• 한국해안해양공학회지
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• 제1권1호
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• pp.1-7
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• 1989

파랑이 완경사해역을 전파해 갈 때 흐름 및 수량변화에 의한 파의 굴절, 회절 등의 파랑변형현상을 나타낼 수 있는 완경사 파동방정식을 변분원리를 이용하여 유도하였다. 이 식은 쌍곡형방정식으로 Kirby(1984)의 식과 같다. 정상상태의 단순 규칙파에 대한 수치모형을 유한채분법을 이용하여 수립하였으며 이 모형은 개방해역에서 계산의 효율 및 정착도가 타모형에 비해 우수하다. 이암류와 규칙파의 상호작용 현상을 수치모형실험을 통해 상세하게 분석하였다.

• Journal of Magnetics
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• 제2권2호
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• pp.38-41
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• 1997

Spinel ferrite thin films Fe3-x MnxO4 (x=0.000, 0.006, 0.0010, 0.015, 0.023) were prepared on the coverglass by ferrite plating technique. To investigate the uniaxial anisotrpy of the samples, the saturation and effective magnetization of the thin films were measured by VSM(vibrating sample magnetometer) and FMR(ferromagnetic resonance) measurements respectively. The spectroscopic splitting g factor were estimated from the ferromagnetic resonance curves. For x=0.000, 0.006, the effective magnetization was measured of temperatures form T=77 K to T=300 K. The results were analyzed in terms of Bloch's law Ms(T) = Ms(0) (1-BT3/2-CT5/2). The Bloch coefficient B, C were determined by fitting. Ms(0) was obtained by extrapolating Meff to 0 K. From this result, the spin wave stiffness constants D was also determined.

• 대한조선학회논문집
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• 제41권4호
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• pp.17-29
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• 2004

Internal waves are computed using a ghost fluid method on an unstructured grid. Discontinuities in density and dynamic pressure are captured in one cell without smearing or oscillations along a multimaterial interface. A time-accurate incompressible Navier-Stokes/Euler solver is developed based on a three-point backward difference formula for the physical time marching. Artificial compressibility is introduced with respect to pseudotime and an implicit method is used for the pseudotime iteration. To track evolution of an interface, a level set function is coupled with the governing equations. Roe's flux difference splitting method is used to calculate numerical fluxes of the coupled equations. To get higher order accuracy, dependent variables are reconstructed based on gradients which are calculated using Gauss theorem. For each edge crossing an interface, dynamic pressure is assigned for a ghost node to enforce the continuity of total pressure along the interface. Solitary internal waves are computed and the results are compared with other computational and experimental results.

• 대한전자공학회논문지
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• 제20권6호
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• pp.52-57
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• 1983

자성체 박막을 갖는 광도파판에서 전자파의 전파를 이론적으로 조사하였다. 광도파관이 갖는 혼합모드의 전계 및 자계의 분포, 또한 그들의 위상속도를 광도파관의 기본 모드의 위상차와 자성박막의 파라데이 회전각으로 나타냈으며 파라데이 효자에 의한 위상 특성곡선의 분할에 대하여 논하였다. 그리고 흔합모드의 이론으로 모드변환 행열을 도출한 결과, 전자파의 진행거리에 따른 모드변환이 광도파관에서는 bulk 매질과는 다름을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.297-300
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• 2005

The bond characteristics of GFRP(glass fiber reinforced polymer) rods with various surface deformation produced by RTM(resin transfer molding) process were analyzes experimentally. Two types of GFRP rods with different surface deformation manufactured by RTM process in domestic area and two types of GFRP rebars imported were considered in this study. All testing procedures including specimens preparation, set-up of test equipments and measuring devices were made according to the CSA S806-02 recommendations. From the test results, it was found that deformed-type GFRP rod manufactured by RTM process showed the highest bond strength among test specimen. But, wave-type GFRP rod made by RTM process show the lowest value due to the splitting failure of concrete caused by the wedge action of waved surfaces on GFRP rods.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.83-105
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• 2013

In this paper, a multi-scale meshfree-enriched finite element formulation is presented for the analysis of acoustic wave propagation problem. The scale splitting in this formulation is based on the Variational Multi-scale (VMS) method. While the standard finite element polynomials are used to represent the coarse scales, the approximation of fine-scale solution is defined globally using the meshfree enrichments generated from the Generalized Meshfree (GMF) approximation. The resultant fine-scale approximations satisfy the homogenous Dirichlet boundary conditions and behave as the "global residual-free" bubbles for the enrichments in the oscillatory type of Helmholtz solutions. Numerical examples in one dimension and two dimensional cases are analyzed to demonstrate the accuracy of the present formulation and comparison is made to the analytical and two finite element solutions.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권4호
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• pp.320-329
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• 2016

An implicit method of solving the six degree-of-freedom rigid body motion equations based on the second order Adams-Bashforth-Moulten method was utilised as an improvement over the leapfrog scheme by making modifications to the rigid body motion solver libraries directly. The implementation will depend on predictor-corrector steps still residing within the hybrid Pressure Implicit with Splitting of Operators - Semi-Implicit Method for Pressure Linked Equations (PIMPLE) outer corrector loops to ensure strong coupling between fluid and motion. Aitken's under-relaxation is also introduced in this study to optimise the convergence rate and stability of the coupled solver. The resulting coupled solver ran on a free floating object tutorial test case when converged matches the original solver. It further allows a varying 70%-80% reduction in simulation times compared using a fixed under-relaxation to achieve the required stability.