• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.37-38
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• 2017

This study identified the effects of flame on the upper by fire plume ejected. we implemented model experiment according to investigation of housing area effect, window aspect ratio and balcony availability. we confirmed that opening ratio was increased according to housing area larger. the square window confirmed that is progressing fire plume ejected of free space. According to the value of an opening aspect ratio 'n' getting higher, the horizontal widow is getting that increased the risk as the fire spread an external to the top of opening. it is determined to the fundamental solution about fire safety in the extended balcony of apartment.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.44-51
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• 2014

Considering the importance of the detailed resolution of the reacting flow field inside a gasifier, the objective of this study lies on to investigate the effect of important variables to influence on the reacting flow and thereby to clarify the physical feature occurring inside the gasifier using a comprehensive gasifier computer program. Thus, in this study the gasification process of a 1.0 ton/day gasifier are numerically modeled using the Fluent code. And parametric investigation has been made in terms of swirl intensity and aspect ratio of the gasifier. Doing this, special attention is given on the detailed change of the reacting flow field inside a gasifier especially with the change of this kind of design and operation parameters. Based on this study, a number of useful conclusions can be drawn in the view of flow pattern inside gasifier together with the consequence of the gasification process caused by the change of the flow pattern. Especially, swirl effect gives rise to a feature of a central delayed recirculation zone, which is different from the typical strong central recirculation appeared near the inlet nozzle. The delayed feature of central recirculation appearance could be explained by the increased axial momentum due to the substantial amount of the presence of the coal slurry occupying over the entire gasifier in gasification process. Further, the changes of flow pattern are explained in detail with the gasifier aspect ratio. In general, the results obtained are physically acceptable in parametric study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.662-669
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• 2012

The effect of aspect ratio (AR) on the aerodynamic characteristics of a flapping wing was examined to analyze the design parameters of an insect-based MAV. The experimental model constructed with 4-bar linkages was operated in a water tank with the condition of a low Reynolds number. A water-proof micro-force load cell was fabricated and installed at the root of the wing which is made of a plexiglas. The wing shapes were based on the planform of a fruit fly wing. The ARs selected were 1.87, 3.74 and 7.48 and the Reynolds number was fixed at $10^4$. For AR=1.87 and 3.74, distinct lift peaks which indicate unsteady effects such as 'wake-capture' were observed at the moment of the start of the wing-stroke. However, for AR=7.48, no unsteady effects were observed. These phenomena were also observed in the delayed rotation case. The results indicate that a larger AR provides better aerodynamic performance for the insect-based flapping wing which can be applied in MAV designs.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.39-49
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• 1998

In this work, fatigue tests by axial loading were carried out to investigate the effect of stress ratio on the growth behaviors of surface fatigue crack for SM45C steel and Al 2024-T4 alloy. The growth behaviors of surface crack have been monitored during fatigue process by measuring system attached CCTV and monitor. When the growth rates of surface crack were investigate by the concept of LEFM based on Newman-Raju's .DELTA.K, the dependence of stress ratio appears both SM45C steel and Al 2024-T4 alloy. Therefore, modified stress intensity factor range, .DELTA.K' [=(1+R)/sup n/.DELTA.K] are intorduced to eliminate the dependence of stress ratio. Using .DELTA.K', it is found that the dependence of stress ratio disappears both SM45C steel and Al 2024-T4 alloy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.281-289
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• 2004

The temperature hump is found to be most efficient in suppressing parasitic nucleation. With the temperature humps, there are found to be observed in undersaturations along the transport path for convective-diffusive processes ranging from $D_{AB}$ = 0.0584 $\textrm{cm}^2$/s to 0.584 $\textrm{cm}^2$/s, axial positions from 0 to 7.5 cm. With decreasing Ar = 5 to 3.5, the temperature difference is increased because of the imposed nonlinear temperature profile but the rate is decreased. For 2 $\leq$ Ar $\leq$ 3.5, the rate is increased with the aspect ratio as well as the temperature difference. Such an occurrence of a critical aspect ratio is likely to be due to the effect of sidewall and much small temperature difference. The rate is decreased exponentially with the aspect ratio for 2 $\leq$ Ar $\leq$ 10. Also, the rate is exponentially decreased with partial pressure of component B, P for 1 $\leq$ P $\leq$ 100 Torr.$ B/ $\leq$ 100 Torr.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.76-84
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane behavior of base metal (BM) and heat affected zone (HAZ) of SAPH45. The main results obtained are as follows: 1) The more aspect ratio (b/t) of corner crack decreases, the more aspect ratio (b/a) takes greatly effect by corrosion. 2) The correlation between the stress intensity factor range ($\Delta$k) and crack growth rate (da/dN) for weldment in seawater is given by Paris rule as follow: da/dN=C($\Delta$K) super(m). Where m is constant, and the value is 3.82-3.84. 3) The accelerative factor ($\alpha$) of BM and HAZ under seawater is about 1.1-1.9, and ($\alpha$) of HAZ increases more and more under the low $\Delta$K region. 4) HAZ is more susceptible to corrowion than BM because of potential of electrode (E sub(c)) of HAZ becomes more less noble potential than that of BM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.4
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• pp.149-156
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• 2006

For an aspect ratio (transport length-to-width) of 5, Pr = 2.89, Le = 0.018, Pe = 2.29, Cv = 1.11, $P_B$=40 Torr, solutally buoyancy-driven convection $(Gr_s=3.03{\times}10^5)$ due to the disparity in the molecular weights of the component A $(Hg_2Cl_2)$ and B (He) is stronger than thermally buoyancy-driven convection $(Cr_t=1.66{\times}10^4)$. The crystal growth rate is decreased exponentially for $2.5\;{\leq}\;Ar\;{\leq}\;5$, with (1) the linear temperature profile and a fixed temperature difference, (2) the imposed thermal profile, a fixed crystal region and varied temperature difference. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. But, with the imposed thermal profile, a fixed source region and varied temperature difference, the rate is increased far $2\;{\leq}\;Ar\;{\leq}\;3$, and remains nearly unchanged for $3\;{\leq}\;Ar\;{\leq}\;5$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.134.2-134.2
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• 2017

최근 고성능, 저 전력 반도체 소자를 위한 미세 공정 기술이 발전함에 따라, gate oxide의 두께 및 선폭이 감소하고, aspect ratio가 증가하고 있는 추세이다. 따라서 얇아진 gate oxide를 통한 채널 물질로의 boron 확산을 막기 위한 고농도 질화 막 증착의 필요성이 높아지고 있으며, high aspect ratio의 gate oxide에 적용 가능한 우수한 step coverage의 질화막 또한 요구되고 있다. 이러한 요구조건을 만족시키기 위해 일반적인 13.56MHz의 플라즈마 소스를 이용한 질화연구들이 선행되어져 왔으나, 높은 binding energy(~24 eV)를 가지고 있는 N2 molecule gas를 효과적으로 dissociation 하지 못해 충분한 질화공정이 수행되어질 수 없었을 뿐만 아니라 높은 공정온도($>200^{\circ}C$에서 진행되어 반도체소자에 손상을 줄 수 있다. 본 연구에서는 이러한 문제들을 해결하기 위해 VHF (162MHz)를 이용한 플라즈마를 통해 고밀도에서 낮은 전자온도와 높은 진동온도의 플라즈마를 구현하여 20%이상의 높은 질화율을 얻을 수 있었고, multi-tile push-pull 플라즈마 소스를 통해 VHF 사용 시 나타나는 standing wave effect를 제어하여 high aspect ratio의 gate sidewall spacer에 우수한 step coverage의 질화막을 형성시킬 수 있었다.

• Journal of Welding and Joining
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• v.25 no.5
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• pp.64-71
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• 2007

The aim of this paper is to investigate the effects of welding parameters on the weld shape in seal-welding of STS304L capsule for manufacturing a radioisotope source which is widely used in nondestructive testing of metal structures using gamma ray. Pulsed gas tungsten arc (Pulsed GTA) welding is performed for thin cross sectional area of the capsule. Seven welding parameters including current waveform parameters and arc length etc. are selected as main process parameters using design of experiment. The weld shape such as bead width, penetration depth, weld area, aspect ratio and area rate is investigated to assess the effects of welding parameters. As results, the combination of pulse duty/welding speed largely affects on bead width, penetration depth, area and aspect ratio. Finally, it is concluded that the key parameters are the combination of pulse duty/welding speed, base current and arc length, and their optimal conditions are 50%/1.77mm/s, 6.4A and 1 mm.

• Design & Manufacturing
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• v.11 no.3
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• pp.1-7
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• 2017

The fabrication process of micro pattern structure with high precision and high aspect ratio using powder injection molding (PIM) is developed. In the PIM process, the metal powder is mixed with the binder systems and the mixture is injected into the metal mold. The injection molded green parts are debinded and sintered to reach final shape and properties. In this method, the optimization of physical properties such as fluidity and strength of the binder system is essential for perfect filling the high aspect ratio micro-pattern. For this purpose, the correlation between the properties of the binder system and feedstock and ${\mu}-PIM$ process was investigated, and a binder system with low viscosity at low temperature(about $110^{\circ}C$) and high strength after cooling was investigated and applied. Employing this process, high precision parts with line type micro pattern structure which has pattern size $160{\mu}m$ and aspect ratio more than 2 can be manufactured.