• 한국전산구조공학회논문집
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• 제23권6호
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• pp.675-682
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• 2010

The flood impact pressure acting on a vertical wall resulting from a dam-breaking problem is simulated using a navier-Stokes(N-S) solver. The N-S solver uses Eulerian Finite Volume Method(FVM) along with Volume Of Fluid(VOF) method for 2-D incompressible free surface flows. A Split Lagrangian Advection(SLA) scheme for VOF method is implemented in this paper. The SLA scheme is developed based on an algorithm of Piecewise Linear Interface Calculation(PLIC). The coupling between the continuity and momentum equations is affected by using a well-known Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. Several two-dimensional numerical simulations of the dam-breaking problem are presented to validate the accuracy and demonstrate the capability of the present algorithm. The significance of the time step and grid resolution are also discussed. The computational results are compared with experimental data and with computations by other numerical methods. The results showed a favorable agreement of water impact pressure as well as the global fluid motion.

• 한국공간구조학회논문집
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• 제4권4호
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• pp.65-76
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• 2004

Walking loads are usually considered as nodal loads in the finite element vibration analysis of structures subjected to walking loads. Since most of the walking loads act on elements not nodes, the walking loads applied on the elements should be converted to the equivalent nodal walking loads. This paper begins with measuring walking loads by using a force plate equipped with load cells and investigates the characteristics of the walking loads with various walking rates. It is found that the walking loads are more affected by walking rates than other parameters such as pedestrian weight, type of footwear, surface condition of floor etc. The measured walking loads are used as input loads for a finite element model of walking induced vibration. Finally, this paper proposes the equivalent nodal walking loads that are converted from the walking loads acting on elements based on finite element shape functions. And the proposed equivalent walking loads are proved to be applicable for efficient analysis of floor vibration induced by walking loads.

• 대한기계학회논문집
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• 제13권4호
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• pp.764-770
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• 1989

This paper analyze the steady state performance of a self-acting air lubricated slider bearing in hard disk/head system. Modified Reynolds' equation is derived from the steady state compressible Navier-Stokes equation, under slip-flow conditions. Finite difference technique and numerical procedure are described by using Newton-Raphson iteration method to slove the non-linear equations. These techniques are applied to conventional slider bearings and the effects of molecular mean free path(MMFP) for a recording surface of hard disk are shown. The calculation procedure developed here, wide applicabilities in practical head design procedures, and converges rapidly.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
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• pp.168-172
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• 2001

The subsurface stress field beneath the roller due to the lubricant film pressure acting on the roller surface has been calculated. Main purpose of this study in view of engineering is to prove the validity of the numerical profile roller presented by Koo et al who obtained the lubricant film pressure by elastohydrodynamic lubrication analysis on the cam-roller mechanism. The stress field for the numerical profile roller was compared with the one for the existing dub-off profile roller.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.334-334
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• 2015

The results of flow feature around two circular cylinders in various arrangements are carried out using two-dimensional simulation at Reynolds number of 200. In this work, time-averaged fluid force acting on the upstream and downstream cylinders were calculated for staggered angle ${\alpha}=0{\sim}90^{\circ}$ in the range of L/D = 1.1~5, where ${\alpha}$ is the angle between the free-stream flow and the line connecting the centers of the cylinders, L is centre-to-centre distance and D is cylinder diameter. The dependence of magnitudes and trends of fluid force coefficient on the spacing ratio L/D and ${\alpha}$ are discussed. In all arrangements of two cylinders, tandem arrangement (${\alpha}=0^{\circ}$) is the case produced a minimum drag coefficient for downstream cylinder. Moreover, the locations of separation and stagnation points or pressure coefficient on surface of the cylinder were examined. Acknowledgement: "This research was a part of the project titled 'Development of integrated estuarine management system', funded by the Ministry of Oceans and Fisheries, Korea."

• 국제초고층학회논문집
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• 제8권4호
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• pp.283-290
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• 2019

Corner cut, corner chamfered or a building shape change are adopted in the design of tall buildings to achieve aerodynamic superiority as well as response reduction. Kikuchi et.al pointed out that large negative peak external pressures can appear near the inside corner of set-back low rise buildings. It is therefore necessary to pay attention to facade design around steps in building surfaces. Peak wind pressures for corner cut or corner chamfered configurations are given in the AIJ code. However, they cannot be applied where there are many variations of vertical and horizontal steps. There has been no previous systematic research on peak wind pressures around steps in building surfaces. In this study, detailed phenomenon of peak wind pressures around steps in buildings are investigated focusing on vertical and horizontal distances from the building's corner.

• 대한화장품학회지
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• 제26권2호
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• pp.9-12
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• 2000

Certain types of anti-inflammatory components and whitening components were in practical use as the active ingredients of quasi drugs expected to display their pharmacological actions. However, only twenty years at most have past since the introduction of cosmetics that not only physically change the condition of the surface of the skin, but also promote skin homeostasis from by acting on the physiological mechanisms of the skin. Since then, much effort hasa been made to find new active ingredients suitable for full-scale development, and the term "cosmeceutical" has often been coined to describe cosmetics containing pharmacologically active components. In this report, the prospects of cosmeceuticals will be discussed on the basis of a review of the history of the development of current skin-care products.

• 지구물리
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• 제9권3호
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• pp.249-262
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• 2006

The 29 May 2004 offshore Uljin, Korea earthquake was predominantly thrust-faulting at a depth of approximately 12 (±2) km. The mainshock attained the seismic moment of M0 =5.41 (±1.87)  1016 N m (Mw = 5.1). The focal mechanism indicates a subhorizontal P-axis trending 264° and plunging 2°. The orientation of P- and T-axis is consistent with the direction of absolute plate motion generally observed within the plates, hence the cause of the May 29 shock is the broad-scale stress pattern from the forces acting on the downgoing slab along the Japan trench and inhibiting forces balancing it. The 29 May 2004 earthquake occurred along a deep seated (~12 km), pre-existing feature that is expressed on the surface as the basement escarpment along the western and southern slopes of the Ulleung basin. The concentrated seismicity along this basement escarpment suggests that this feature may qualify as a seismic zone - the Ulleung basement escarpment seismic zone (UBESZ).

• Wind and Structures
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• 제29권1호
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• pp.55-64
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• 2019

The effect of vortex impingement on the fluid dynamics around a cylinder submerged in the wake of another of different diameters is numerically investigated at a Reynolds number Re = 200. While the diameter (D) of the downstream cylinder is fixed, impinging vortices are produced from the upstream cylinder diameter (d) varied as d/D = 0.24, 0.4, 0.6, 0.8 and 1.0, with a spacing ratio L=5.5d, where L is the distance between the center of the upstream cylinder to the front stagnation point of the downstream cylinder. Two-dimensional simulations are carried out using the finite volume method. Fluid forces acting on the two cylinders are correlated with impinging vortices, vortex shedding, and wake structure. Different facets of wake formation, wake structure, and flow separation and their connections to fluid forces are discussed.

• 한국초전도ㆍ저온공학회논문지
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• 제23권3호
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• pp.26-31
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• 2021

Advanced classification of Cs contaminated soil by using a magnetic force-assisted selection pipe was investigated. A selection pipe is a device that sort particles depending on their particle size, based on the relationship between buoyancy, drag, and gravity force acting on the particles. Radioactive cesium is concentrated in small-particle size soil components with a large specific surface area. Hence, the volume of the Cs contaminated soil can be reduced by recycling the large-particle size soil components with low radioactive concentration. One of the problems of the selection pipe was that the radioactive concentration of the stayed soil in the selection pipe exceeds 8000 Bq/kg, which is the standard value of recycling of Cs contaminated soil, due to low classification accuracy. In this study, magnetic fields were applied to the lab-scale selection pipe from upper side to improve the classification accuracy and to reduce the radioactive concentration of the stayed soil.