• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.46-56
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• 2010

The present research works investigated into the low velocity impact characteristics of DP 780 high strength steel sheet with 1.7 mm in thickness subjected to free boundary condition using three-dimensional finite element analysis. Finite element analysis was carried out via ABAQUS explicit code. Hyper-elastic model and the damping factor were introduced to improve an accuracy of the FE analysis. An appropriate FE model was obtained via the comparison of the results of the FE analyses and those of the impact tests. The influence of the impact energy and nose diameter of the impact head on the force-deflection curves, impact time, absorption characteristics of the impact energy, deformation behaviours, and stress-strain distributions was quantitatively examined using the results of FE analysis. The results of the FE analysis showed that the absorption rate of impact energy lies in the range of the 70.7-77.5 %. In addition, it was noted that the absorption rate of impact energy decreases when the impact energy increases and the nose diameter of the impact head decreases. The local deformation of the impacted region was rapidly increased when the impact energy was larger than 76.2 J and the nose diameter was 20 mm. A critical impact energy, which occur the instability of the DP780, was estimated using the relationship between the plastic strain and the impact energy. Finally, characteristics of the plastic energy dissipation and the strain energy density were discussed.

• Journal of architectural history
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• v.13 no.3
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• pp.85-95
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• 2004

Through 16-17th century, Neo-Confucianism was accepted and extended to Chosun Dynasty. The architecture of the Taegae school made buildings of Yongnam area rich by adding the regional characteristics based on Taegae's thought of architecture. The following is the architectural characteristics of the academic clique around Sangju. Transformation such as separation and combination of the Jeongsa space by function, lifted floor type reflecting local feature or high platform was appeared, and the architectural characteristics of the Taegae school, that is, a small scale, a moderate figure, a type of side-attached floor, landscape, were still maintained at the same time. The characteristics of the Taegae school and regional figure of Sangju were well joined. The upper class houses, Seodang, Jeongsa and Seowon, built by Confucianist had shared common Confucian characteristics in spite of their different purposes. The world view of the Confucianism such as sacrifice for sages, cultivation, devoting for study, teaching disciples, and education for villagers was revealed through the Confucian architecture including dwelling houses during the 16-17th century. Buildings of Confucianist were focused on the space for men. Seoae and Kyumam built two different Jeongsa's inside and outside of the boundary of the nakdong river. While Seodang and Jeongsa located outside of the boundary of the river were built excluding spaces for living, the function of the Jeongsa located inside of the boundary of the river was assimilated by Sarangcahe. However, both buildings kept the function for cultivation, devoting for study and teaching.

• The Journal of the Korea Contents Association
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• v.16 no.11
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• pp.707-715
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• 2016

The most important role of actors is to transmit the thoughts and feelings to the audience or viewers. The expression methods of acting of each genre are clearly different. In order for the actors to act, crossing over the boundary of each genre such as movies, TV, dramas, musicals, they should understand the characteristics of each of the subdivided genres. If they understand the characteristics of the acting method different from one another and acquire the expression method to adapt to the spatial circumstances of each of the media, it becomes freer to act, crossing over the boundary of each of the genres. For the sake of this, actors must understand and acquire the characteristics of each of the genres. First of all, it is important to understand the difference between acting in the media and acting on the stage and to understand the characteristics of each of the genres.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.1
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• pp.69-84
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• 2020

Natural shoreline repeats its re-treatment and advance in response to the endlessly varying sea-conditions, and once severely eroded under stormy weather conditions, natural beaches are gradually recovered via a boundary layer streaming when swells are prevailing after storms cease. Our understanding of the boundary layer streaming over surf-zone often falls short despite its great engineering value, and here it should be noted that the most sediments available along the shore are supplied over the surf-zone. In this rationale, numerical simulation was implemented to investigate the hydraulic characteristics of boundary layer streaming over the surf zone in this study. In doing so, comprehensive numerical models made of Spatially filtered Navier-Stokes Eq., LES (Large Eddy Simulation), Dynamic Smagorinsky turbulence closure were used, and the effects of turbulence closure such as Dynamic Smagorinsky in LES and k-ε on the numerically simulated flow field were also investigated. Numerical results show that due to the intrinsic limits of k-ε turbulence model, numerically simulated flow velocity near the bottom based on k-ε model and wall function are over-predicted than the one using Dynamic Smagorinsky in LES. It is also shown that flow velocities near the bottom are faster than the one above the bottom which are relatively free from the presence of the bottom, complying the typical boundary layer streaming by Longuet-Higgins (1957), the spatial scope where boundary layer streaming are occurring is extended well into the surf zone as incoming waves are getting longer. These tendencies are plausible considering that it is the bottom friction that triggers a boundary layer streaming, and longer waves start to feel the bottom much faster than shorter waves.

• Journal of applied mathematics & informatics
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• v.25 no.1_2
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• pp.67-83
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• 2007

The characteristics of steady two-dimensional laminar boundary layer flow of a viscous and incompressible fluid past a moving wedge with suction or injection are theoretically investigated. The transformed boundary layer equations are solved numerically using an implicit finite-difference scheme known as the Keller-box method. The effects of Falkner-Skan power-law parameter (m), suction/injection parameter ($f_0$) and the ratio of free stream velocity to boundary velocity parameter (${\lambda}$) are discussed in detail. The numerical results for velocity distribution and skin friction coefficient are given for several values of these parameters. Comparisons with the existing results obtained by other researchers under certain conditions are made. The critical values of $f_0$, m and ${\lambda}$ are obtained numerically and their significance on the skin friction and velocity profiles is discussed. The numerical evidence would seem to indicate the onset of reverse flow as it has been found by Riley and Weidman in 1989 for the Falkner-Skan equation for flow past an impermeable stretching boundary.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.1-8
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• 2011

A coupled thermal/structural analysis of mechanical ablation is performed based on domain/boundary decomposition and finite element method. The ablative material non-linearity and boundary non-linearity can be easily localized within a few subdomains and/or on the boundary interfaces. An enthalpy method is applied to simplify the effect of heat of pyrolysis in the ablative subdomains. In addition, maximum in-plane shear stress is considered as a surface recession criterion for the mechanical ablation simulation. The basic characteristics of the proposed method are examined carefully through numerical experiments.

• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.878-888
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• 2016

This paper proposes an efficient method to remove the boundary artifacts of rendered views caused by damaged depth maps in the 3D video system. First, characteristics of boundary artifacts with the compression noise in depth maps are carefully studied. Then, the artifacts suppression method is proposed by the iterative projection onto convex sets (POCS) algorithm with setting the convex set in pixel and frequency domain. The proposed method is applied to both texture and depth maps separately during view rendering. The simulation results show the boundary artifacts are greatly reduced with improving the quality of synthesized views.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.99-103
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• 2003

An analysis of the flow within supersonic turbine cascades is necessary to design and manufacture turbo-pump system. Because of the differences between the specified inlet boundary value and the computed inlet value caused by the far field inlet boundary condition, the computations at desired inlet conditions can not be achieved. So, this paper studied the problem occurred when far field inlet conditions were specified as inlet boundary conditions. And the numerical analyses using Fine Turbo, CFD Program, has been performed and compared with those of experiments when a converging-diverging nozzle or a linear nozzle was located in front of cascades instead of the far field inlet condition.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.32-36
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• 2012

This paper presents a comparison of potential and viscous computational codes for the water entry problem. A po-tential code was developed which adopted the boundary element method to solve the problem. A nonlinear free surface boundary condition was integrated to find new locations of free surface. The dynamic boundary condition was simplified by taking constant potential values for every time steps. The simplified dynamic boundary condition was applied in the new position of the free surface not at the mean level, which is the usual practice for linearized theory. The commercial code FLUENT was used to solve the water entry problem from the viscosity point of view. The movement of the air-liquid interface is traced by distribution of the volume fraction of water in a computational cell. The pressure coefficients were compared with each other, while experimental results published by other researchers were also examined. The characteristics of each method were discussed to clarify merits and limitations when they were applied to the water entry problems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.267-277
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• 1993

A finite element method(FEM) is presented and applied to the two-dimensional bottom turbulent boundary layer. The time-dependent incompressible motion of a viscous fluid is formulated by using the well-known Navier-Stokes equations and vorticity equation in terms of the velocity and pressure fields. The general numerical formulation is based on Galerkin method and solved by introducing the mixing length theory of Prandtl for eddy kinematic viscosity of a turbulent flow field. Numerical computations of the transport of sediment on an arbitrary sea-bed due to wave motion in the turbulent boundary layer are carried out. The results obtained by the FEM made clear the difference in characteristic features between the boundary layer due to oscillatory flow and the boundary layer due to wave motion.