• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.641-646
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• 2001

Generally, when Fly-Ash was used as replacement material of cement in concrete, it might occur retardation of setting and hardening. So, it is unable to use a large amount of Fly-Ash as replacement for cement. However, if it is used as replacement material of fine aggregate in concrete, we can use a large amount of Fly-Ash and settle a problem of natural-aggregate exhaustion. Furthermore, engineering properties of High Volume Fly-Ash Concrete Is better than that of plain concrete But, the larger Fly-Ash is replaced, the more fluidity of High Volume Fly-Ash Concrete decrease, because porous organization of Fly-Ash adsorb water and Superplasticizer. In this study, after appending additional water to High Volume Fly-Ash Concrete in proportion to weight of Fly-Ash, we intend to find proper ratio which doesn't affect strength and satisfy fluidity As a result of this study, it was found that fluidity of mortar with 25~28 percentage of additional water was satisfied with fluidity of plain mortar, and compressive strength of that was similar to plain mortar's

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.921-926
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• 2001

In this paper the biaxial failure criteria and stress-strain response for plain concrete are studied under uniaxial and biaxial stress(compression-compression, compression-tension, and tension-tension combined stress). The concrete specimens of a square plate type are used for uniaxial and biaxial loading. The experimental data indicate that the strength of concrete under biaxial compression, f2/fl=-l/-1, is 17 percent larger than under uniaxial compression and the poisson's ratio of concrete is 0.1745. On the base of the results, a biaxial failure envelope for plain concrete that the uniaxial strength is 398kgf/$cm^{2}$ are developed. The biaxial failure behaviors for three biaxial loading areas are also plotted respectively. In addition, the characteristics of stress-strain response under biaxial compression are compared and verified with the experimental and analytical results.

• 콘크리트학회논문집
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• 제12권2호
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• pp.43-51
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• 2000

This study is to investigate for the frost resistance of high-flowing concrete using finely ground granulated blast-furnace slag with experimental parameters, such as type of binder, type of superplasticizer and method of curing. The resistance to freezing and thawing of high-flowing concrete by type of binder and superplasticizer is presented differently. Though the frost resistance of high-flowing concrete is satisfactory under standard condition, it is required that high-flowing concrete has entrained air like plain concrete. Because the critical spacing factor, being capacity of frost resistance, of high-flowing concrete is longer that of plain concrete, the frost resistance of high-flowing concrete, using finely ground granulated furnace blast slag, is superior to that of plain concrete.

• 한국유체기계학회 논문집
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• 제16권3호
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• pp.26-31
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• 2013

In present 3D CFD study, the method for determining leakage and rotordynamic coefficients of a plain-gas seal is suggested by using the relative coordinate system for steady-state simulation. In order to find the effect of pre-swirl speed at seal inlet, pre-swirl velocity is included as a parameter. Present analysis is verified by comparison with results acquired from Bulk-flow analysis code and published experimental results. The results of 3D CFD rotordynamic coefficients of direct stiffness(K) and cross-coupled stiffness(k) show improvements in prediction. As pre-swirl speed at seal inlet increases, k also increases to destabilize system. However, pre-swirl speed at seal inlet does not show sensitivity to the leakage and rotordynamic coefficients of K and damping(C).

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.134-136
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• 2005

Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.712-714
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• 2003

The modifications taking place within the alluvial plains impart a larger extent of disturbances to hydrologic systems. The objective of the present investigation is to detect the sensitivity of multi-temporal image data from Landsat TM (Thematic Mapper) for finding out the land-cover/land-use changes associated with alluvial low land. The eastern coast of Chiba Prefecture, Japan, forms a very important geographic unit owing to the existence of a unique alluvial landform. The alluvial plain occupied in the study area is widely known as 'Kujukuri Plain'. The TM images have been classified by means of maximum likelihood supervised classifier and the extent of changes has been estimated.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.125-129
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• 2005

Flow control has been performed using synthetic jet on NACA23012. In order to improve aerodynamic performance, synthetic jet is located near separation paint on airfoil with leading edge droop and plain flap. The flow control using synthetic jet shows that stall characteristics and control surface performance can be improved through resizing separation vortices. Stall is delayed and stall characteristics are improved when synthetic jet is applied from separation region of leading edge droop. Control surface effectiveness is increased and lift is increased when synthetic jet applied at the flap leading edge region. The results show that aerodynamic characteristics can be improved through leading edge droop with synthetic jet at near separation and plain flap with synthetic jet at the flap leading edge. The combination of synthetic jet and simple high lift device is as good as fowler flap system.

• Composites Research
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• 제13권2호
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• pp.8-21
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• 2000

본 논문에서는 평직복합재료에 있어서 섬유다발의 위상각 변화와 적층수에 따른 등가탄성계수의 저 균일도 문제를 연구하였다. 각 적층수에 따라 단순히 적층된 모델과 무한히 반복되어 적층된 모델에 대해 단위구조 해석을 수행하였다. 수치실험을 통해 탄성계수를 계산하였고, 이를 통계적으로 처리하였다. 계산 결과 평직복합재료의 등가탄성계수는 위상각과 적층수의 변화에 크게 의존하며 임의의 조합에 대하여 그 분포양상은 큰 차이를 보였으나, 전반적으로 적층수가 증가함에 따라 균일도가 높아지는 경향을 보였다.

• 한국대기환경학회지
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• 제17권4호
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• pp.299-312
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• 2001

The analysis of vent -emitted Hg concentrations and relevant environmental parameters was made from the inlet of 42 ventpipes in Nan-Ji-Do area of Seoul during September/october of 2000. Using these data, the fluxes of Hg from the ventpipes were also derived. The mean concentration of Hg, computed using the data sets collected from 42 ventpipes, was 420$\pm$619ng m$^{-3}$ with the range of 3.45~2,952ng m$^{-3}$ . Because of large differences in concentration levels between two sectors 1 and 2 and between plain and slope areas. evaluation of the data was made by dividing them into four different categories such as plain areas of sectors 1 and 2 (and/or slope areas of sectors 1 and 2). When this classification was applied, the computed fluxes were highly different among each group with the generally enhanced fluxes in plain area relative to slope area. The computed fluxes were then used to make comparative analysis of different source processes in the study area.

• Tribology and Lubricants
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• 제6권2호
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• pp.76-87
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• 1990

It is known that the effects of oil supply conditions on the characteristics of plain journal bearings are significant and especially the dynamic characteristics are affected by cavity region. For various shapes (axial groove, spiral groove, X-shape groove) and positions of oil grooves, the pressure distribution and the static performance of plain journal bearings are obtained with numerical methods. Elrods algorithm which implements JFO oil rupture/reformation boundary condition is used in order to take into account the effect of cavity region. It is shown that in the cases of axial groove or X-shape groove the load capacity and the attitude angle are affected by the groove position but the effect of spiral groove position is less significant.