• KIEAE Journal
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• 제7권1호
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• pp.23-31
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• 2007

This study aims to evaluate the illuminance performance of sloped light guide with automated venetian blind systems. For the purpose, a mock-up model was constructed as a prototype of Korean office building with $12.0m{\times}7.3m{\times}3.7m$ ($w{\times}d{\times}h$) and south facing side-window mounted between the clerestory window($2.0m^2$) and the view window($5.6m^2$). The light guide of 1.28m deepth and $29^{\circ}$ tilted angle, is covered with 0.6mm galvanized steel sheet and 97% reflective film. To protect the room from low solar angle, a blind systems, 0.15m deepth and $30^{\circ}$ automated slat angle was installed. To assess illuminance performance, the totally 37 measuring points for illuminance were monitored. For the detailed analysis, photometric sensors were installed at work-plane (8 points), wall (7 points), ceiling (3points), and exterior horizontal illuminance (1 point) respectively. The performance was measured under clear sky and is monitored by Agilent data logger, photometric sensor Li-cor and the Radiant Imaging ProMetric 1400. Comparisons of light factor and uniformity are discussed.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.45-57
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• 2002

In this paper, the results gained by applying many impingement models to the cylinder and flat plate were analyzed in comparison with the experimental data to study a spray/wall interaction phenomena. To begin with, the behavior of spray injected normal to the wall was analysed using three different impingement models ; Naber and Reitz model(NR model), Watkins and Wang model(WW model) and Park and Watkins model(PW model) in the present calculation. The results obtained from these models were compared with experimental data of Katsura et. al. The results indicated that PW model was in better agreement with experimental data than the NR and WW model. Also f3r spray injected at 30DEG , the result of three models were compared with experimental data of Fujimoto et. al. The results showed that m model overpredicted the penetration in the radial direction because this model was based on the inviscid jet analogy. WW model did not predicted the radius and height of the wall spray effectively. It might be thought that this discrepancy was due to the lack of consideration of spray film velocity occurred at impingement site. The result of PW model agrees with the experimental data as time goes on. In particular, a height of the spray droplets was predicted more closely to the experimental data than the other two models. The results of PW model in which the spray droplets were distributed densely around the edge of droplet distribution shaped in a circle had an agreement with the experimental data of Fujimoto et. al. Therefore, it was concluded that PW model performed better than M and WW model for prediction of spray behavior. The numerical calculation using PW model performed to the cylinder similar to the real shape of DI engine. The results showed that vortex strength near the wall in the cylinder was stronger than that in the case of flat plate. Contrary to the flat plat, an existence of the side wall in the cylinder caused the tangential velocity component to be reduced and the normal velocity component to be increased. The flow tends to rotate to the inside of cylinder going upward to the right side wall of cylinder gradually as time passes. Also, the results showed that as the spray angle increases, the gas velocity distribution and the tumble flow seemed to be formed widely.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.280-287
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside the rib-roughened cooling passage of the gas turbine blades. A square duct with rectangular ribs is used and $\wedge-$ and V-shape ribs with $60^{\circ}$ attack angle are installed on the test plate surfaces. Naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vortices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. A square duct with $\wedge$ and V-shape ribs has two pairs of secondary flow because of the rib arrangement. So, the duct has complex heat/mass transfer distribution. The average heat/mass transfer coefficient and pressure drop of $\wedge-$ and V-shape ribs are higher than those with $90^{\circ}$ and $60^{\circ}$ attack angles. The average heat/mass transfer coefficient on the $\wedge-shape$ ribs is higher than that on the V-shape ribs. Also, the uniformity of heat/mass transfer coefficient on discrete ribs is higher than that on continuous rib.

• 한국지반공학회논문집
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• 제15권4호
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• pp.235-246
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• 1999

지하철 터널 등의 지하구조물을 개착식으로 시공할 때에는 먼저 지반을 굴착하고 구조물을 설치한 후에 굴착공간을 되메움한다. 이때 굴착면과 구조물사이의 되메움 공간이 협소하여 되메움지반의 자중에 의하여 지하구조물에 작용하는 토압은 고전적인 방법으로 구한 토압과 상이하다. 개착식으로 시공한 구조물의 상부슬래브와 측벽에 작용하는 연직 및 수평토압은 되메움공간의 형상에 따라 영향을 받을수 있으며 이를 규명하기 위하여 되메움공간의 형상과 벽마찰각을 변화시키면서 실내모형시험을 실시하여 그 결과를 기존의 토압이론과 비교분석하였다. 그 결과 되메움공간의 형상 즉 되메움폭과 원지반 굴착면 경사 및 구조물의 벽마찰각에 의한 영향이 관찰되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2648-2653
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• 2007

Recently, increasing demand on not only lighter but also extremely mobile battery make micro fuel cell device very attractive alternative. By reducing the size of fuel cell, surface tension becomes dominant factor with minor gravitational effect. Therefore, it is very difficult to detach the $CO_2$ bubble generating on a cathode side in ${\mu}DMFC$ (micro direct methanol fuel cell). The degassing of a $CO_2$ bubble has drawn quite attention especially for ${\mu}DMFC$ due to its considerable effect on overall machine performance. Our attention has been paid to the dynamic behavior of immiscible bubble attached to the one side of the wall on 2D rectangular channel subject to external shear flow. We use Level Contour Reconstruction Method (LCRM) which is simplified version of front tracking method to track the bubble interface motion. Effects of Reynolds number, Weber number, advancing/receding contact angle and property ratio on bubble detachment characteristic has been numerically identified.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.102-106
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• 1996

In the ball end-milling process of a 3-dimensional mold, it is important to select cutting conditions and tool path considering the geometrical shape of a workpiece to reduce machining time. In this study, experiments were performed to decide allowable feed rate not breaking stability of system for different geometrical shapes. It was found that downcut is more stable than upcutting in machining side wall and downward is preferable to upward in inclined part depending on the angle of the inclination and depth of cut.

• 한국유체기계학회 논문집
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• 제14권6호
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• pp.54-60
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• 2011

This paper presents the steady-state performance analysis of the first stage of a multistage centrifugal pump, composed of a shrouded-impeller, a vaned-diffuser and a return-channel, using the commercially available computational fluid dynamics (CFD) code, ANSYS CFX. The detailed flow fields in the vaned-diffuser with outlet in its side wall and the return-channel are investigated by the CFD code adopted in the present study. The effect of the vaned-diffuser with a downstream crossover bend and the corresponding return-channel on the overall hydrodynamic performance of the first stage pump has also been demonstrated over the normal operating conditions. The predicted hydrodynamics for the diffusing components herein could provide useful information to match the inlet blade angle of the next stage impeller for improving the multistage pump performances.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.465-468
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• 2008

In this paper, ABAQUS, one of the implicit finite element codes, is used to analyze the U-channel Draw benchmark problem of NUMISHEET 2005. Forming and springback stages have been done consecutively to compare their results with the experimental ones. The main measures for comparing are the side wall curl and angle. The result by numerical analysis are shown generally to be correspondent with the experimental results that the max. error is confined under about 10%.

• 지질공학
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• 제18권3호
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• pp.277-285
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• 2008

쏘일네일링은 최근 들어 그 적용성이 확대되고 있으나 아직까지 공인된 설계방법이 없다. 또한 쏘일네일링은 설계변수가 많고 설계변수 상호간의 민감도에 대한 연구가 되지 않은 상황에서 명확한 근거 없이 사용되고 있다. 특히, 본 연구의 주요 과제인 네일의 설치각도에 대한 민감성은 다루어지지 않고 있다. 따라서 본 연구는 이론적 계산식을 바탕으로 파괴면에 대한 네일의 각도와 벽체의 높이, 단위중량, 점착력, 내부 마찰각, 네일에 작용하는 인장력 등을 고려하여 안전율을 분석하였다. 그 결과, 배면지반이 수평이고 수직벽체인 경우 네일의 설치 각도는 하향보다 상향이 모두 안전율이 증가하는 것을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.42-42
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• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.