• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.89-92
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• 2004

This paper is concerned with the drawing process of Al-Si wire. In this study, the finite-element model established in previous work was used to analyze the effects of various forming parameters, which included the reduction in area, the semi-die angle, the aspect ratio and the inter-particle spacing of the Si in drawing processes. The finite-element results gave the consolidation condition. From the results of analysis, the effects of each forming parameter were determined. It is possible to obtain the important basic data which can be guaranteed in the fracture prevention of Al-Si wire by using FEM simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.312-317
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• 2005

Fluid-elastic instability and turbulence excitation for an under developing steam generator are investigated numerically. The stability ratio and the amplitude of turbulence excitation are obtained by using the PIAT (Program for Integrity Assessment of Steam Generator Tube) code from the information on the thermal-hydraulic data of the steam generator. The aspect ratio, the ratio between the height of U-tube from the upper most tube support plate (h) and the width of two vertical portion of U-tube (w), is defined for geometric parameter study. Several aspect ratios with relocation of tube support plates are adopted to study the effects on the mode shapes and characteristics of flow-induced vibration. When the aspect ratio exceeds value of 1, most of the mode shapes at low frequency are generated at the top of U-tube. It makes very high value of the stability ratio and the amplitude of turbulent excitation as well. We can consider that the local mode shape at the upper side of U-tube will develop the wear phenomena between the tube and the anti-vibration bars such as vertical, horizontal, and diagonal strips. It turns out that the aspect ratio reveals very important parameter for the design stage of the steam generator. The appropriate value of the aspect ratio should be specified and applied.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1009-1015
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• 2005

Fluid-elastic instability and turbulence excitation for an under developing steam generator are investigated numerically. The stability ratio and the amplitude of turbulence excitation are obtained by using the $PIAT^{(R)}$ (program for integrity assessment of steam generator tube) code from the information on the thermal-hydraulic data of the steam generator. The aspect ratio, the ratio between the height of U-tube from the upper most tube support Plate (h) and the width of two vertical portion of U-tube (w), is defined for geometric parameter study. Several aspect ratios with relocation of tube support plates are adopted to study the effects on the mode shapes and characteristics of flow-induced vibration. When the aspect ratio exceeds value of 1, most of the mode shapes at low frequency are generated at the top of U-tube. It makes very high value of the stability ratio and the amplitude of turbulent excitation as well. We can consider that the local mode shape at the upper side of U-tube will develop the wear phenomena between the tube and the anti-nitration bars such as vortical, horizontal, and diagonal strips. It turns out that the aspect ratio reveals very important parameter for the design stage of the steam generator. The appropriate value of the aspect ratio should be specified and applied.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.727-728
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• 2008

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.37-38
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• 2006

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.266-269
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• 2009

Iron-based soft magnetic materials are widely used as cores, such as transformer transformers, motors, and generators. Reducing losses generated from soft magnetic materials of these applications results in improving energy conversion efficiency. Recently, the new P/M soft magnetic material realized an energy loss of 68 W/kg with a drive magnetic flux of 1 T, at a frequency of 1 kHz, rivaling general-purpose electromagnetic steel sheet in the low frequency range of 200 Hz to 1 kHz. In this research, the effect of rolling parameters on soft magnetic properties of Fe-based powder cores was investigated. The Fe-based soft magnetic plates were produced by the hot powder rolling process after both pure Fe and Fe-4%Si powders were canned, evacuated, and sealed in Cu can. The soft magnetic properties such as energy loss and coercive power were measured by B-H curve analyzer. The soft magnetic properties of rolled sheets were measured under conditions of a magnetic flux density of 1 T at a frequency of 200 kHz. It was found that rolling reduction ratio is the most effective parameter on reducing both energy loss and coercivity because of increasing aspect ratio with reduction ratio. By increasing aspect ratio from 1 to 9 through hot rolling of pure Fe powder, a significant loss reduction of one-third that of SPS sample was achieved.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.444-447
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• 2005

In recent industry, according to pursuit the miniaturization and high-precision of machine part with development of new technology as If, BT the development of mold manufacturing technology for mass production is accompanied. In this study, after executing the injection molding process of micro structure on the plate which the aspect ratio is 10, the characteristic of each molding condition is investigated by observing the filling height.

• Journal of Korean Vacuum Science & Technology
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• 제6권2호
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• pp.79-83
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• 2002

As Ag does not form my silicide on Si surfaces, Ag wire is a candidate for self-assembled nanowire on the reconstructed and single-domain Si(5 5 12)-2 $\times$ 1. In the present study, various Ag coverages and post-annealing temperatures had been tested to fabricate a Ag nanowire with high aspect ratio. When Ag coverage was less than 0.03 ML and the post-annealing temperature was 500(C, Ag atoms preferentially adsorbed on the tetramer sites resulting in Ag wires with an inter-row spacing of ~5 nm. However, its aspect ratio is relatively small and its height is also not even. On the other hand, the Ag-posited surface completely loses its reconstruction even with the same annealing at 500 $\^{C}$ if the initial coverage exceeds 0.05 ML. But the additional subsequent annealing at 700$\^{C}$ and slow-cooling process recovers the well-ordered Ag chain with relatively high aspect ratio on the same tetramer sites. It can be understood that, in the double step annealing process, the lower temperature annealing is required for cohesion of adsorbed Ag atoms and the higher temperature annealing is for providing Ag atoms to the tetramer sites.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.666-670
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• 2004

VLSI 소자에서 design rule(D/R)이 작아져 각 단위 Pattern의 size가 작아짐에 따라 aspect ratio가 커지게 되었다. 산화막 contact etch를 하는데 있어 산화막 측벽을 보호하는데, 이러한 보호막은 주로 fluoro-carbon 계열의 polymer precursor들이 사용된다. Aspect ratio(A/R)가 5 이하일 때에는 측벽의 보호막에 의한 바닥 변형이 문제가 되지 않으나, 10 이상의 A/R를 가진 contact에서는 크기가 줄고, 모양이 불균형하게 변하는 바닥 변형을 쉴게 관찰할 수 있다. 이러한 바닥 변형이 커지면 contact 저항이 높아지는 것은 물론이고, 심하게는 하부 pattern과 overlap 불량을 유발할 수 있다. 본 논문에서는 바닥변형을 일으키는 원인을 분석하고 fluoro-carbon 계열의 polymer precursor의 종류$(C_4_F6\;vs.\;C_3F_8)$에 따른 polymer증착 상태 확인 및 pattern비대칭에 따른 바닥 변형의 고찰과 plasma etching 시 H/W 변형을 통해 바닥 변형이 거의 없는 조건을 찾아낼 수 있었다.

• 대한기계학회논문집B
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• 제30권9호
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• pp.873-881
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• 2006

The present study investigates the pressure drop characteristics in rotating two-pass ducts. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter $(D_h)$ of 26.67mm. Rib turbulators are attached crossly in the four different arrangements on the leading and trailing surfaces of the test ducts. The ribs have a rectangular cross section of $2mm(e){\times}3mm(w)$ and an attack angle of $70^{\circ}C$. The pitch-to-rib height ratio (pie) is 7.5, and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.075. The results show that the highest pressure drop among each region appears in the turning region for the stationary case, but appears in the upstream region of the second pass for the rotating case. Effects of cross rib arrangements are almost the same in the first pass for the stationary and rotating cases. In the second pass, however, heat transfer and pressure drop are high for the cases with cross NN or PP type ribs in the stationary ducts. In the rotating ducts, they are high for the cases with cross NP or PP type ribs.