• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.890-893
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• 2002

This study is focused to predict the behavior of Al foam with closed-cell structure during the 3 point bending test and the upsetting test according to aspect ratio. We calculated characters of aluminum foams with closed-cell structure and took the simulation. The effects on the aspect ratio of the cell was investigated parametrically. The analysis was carried out on two models, First, the bending test in elasticity of the rectangular beam, and Second, the upsetting test in plasticity of the circular cylinder. In the analysis, the deformation of the beam and the cylinder was influenced by the aspect ratio of the cell. Further, We assumed that the geometry of feared aluminum cell change the stress and strain in the test.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.324-331
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• 2002

The characteristics of moisture ventilation in a dry room are studied numerically The behaviors of moisture ventilation are analyzed by varying the aspect ratio of the horizontal plane and for various positions of the outlets in the room. Three different ventilation efficiencies have been used to examine the effect of the longitudinal arrangement of outlets and transverse arrangement of outlets for each aspect ratio on ventilation inside the room. It is shown that the ventilation efficiency in the dry room can be improved by arranging the outlets transversely in the cases that the aspect ratio is less than three and longitudinally in the cases that it is greater than four.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.199-204
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• 2001

This paper showed the study on the heat transfer into space by the aspect ratio of solar concentration absorber, and the purpose of this study is to obtain the optimum aspect ratio and tilt angle. The boundary conditions of a numerical model were assumed as follows : (1) The heat source is located at the center of absorber. (2) The bottom was is opened and adiabatic. (3) The top, right and left walls are cooled wall. The parameters for the study are the tilt angles and the aspect ratio. The velocity vectors and isotherms were dense at wall side and the heat source. The mean Nusselt number had a maximum value at Ar=1:1 and $\theta=0^{\circ}$ and showed a low value as the tilt angles were increased.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.4
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• pp.302-310
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• 2008

This paper puts forward an advanced consideration on the design of scaled multiple-gate FET (MuGFET); the aspect ratio ($R_{h/w}$) of the fin height (h) to fin width (w) of MuGFET is considered with the aid of 3-D device simulations. Since any change in the aspect ratio must consider the trade-off between drivability and short-channel effects, it is shown that optimization of the aspect ratio is essential in designing MuGFET's. It is clearly seen that the triple-gate (TG) FET is superior to the conventional FinFET from the viewpoints of drivability and short-channel effects as was to be expected. It can be concluded that the guideline of w < L/3, where L is the channel length, is essential to suppress the short-channel effects of TG-FET.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.47-53
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• 2005

Microholes with high aspect ratio are required in microstructures. Among various methods for producing the microhole, micro electrical discharge machining (MEDM) is very effective and useful process. But, it is difficult to machine the high aspect ratio holes below $100\;{\mu}m$ in diameter because machining condition becomes unstable due to bad removal of debris at deep hole. In this paper, ultrasonic vibration is applied to MEDM work fluid to make a high aspect ratio micro hole. It is shown that the vibration is effective in circulating the debris and increasing the machining rate. As a result, produced was a micro hole with $92\;{\mu}m$ entrance diameter, $81\;{\mu}m$ exit diameter and aspect ratio 23.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.84-87
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• 2009

This paper describes a novel method for fabricating large area metallic stamp with high aspect ratio micro intaglio features. Micro machined brass master with pillar and larger width groove patterns were electroformed to form inverse structures on the large area metallic stamp. This enabled large area metallic stamp with fine micro high aspect ratio micro intaglio features which were small width groove patterns and quadrilateral hole patterns that cannot be fabricated by direct micro machining process. Fabricated large area metallic stamp with high aspect ratio micro intaglio features was measured and analyzed.

• Journal of Power System Engineering
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• v.6 no.1
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• pp.43-49
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• 2002

This paper showed the study on the heat transfer into space by the aspect ratio of solar concentration absorber, and the purpose of this study was to obtain the optimum aspect ratio and tilt angle. The boundary conditions of a numerical model are assumed as follows : (1) The heat source is located at the center of absorber. (2) The bottom wall is opened and adiabatic. (3) The top, right and left walls are cooled wall. The parameters for the study are the tilt angles and the aspect ratio. The velocity vectors and isotherms were dense at wall side and the heat source. The mean Nusselt number had a maximum value at Ar=1:1 and ${\theta}=0^{\circ}$ and showed a low value as the tilt angles were increased.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.1
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• pp.44-53
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• 2004

This paper is to investigate the combustion characteristics with a three dimensional chemical reacting flow on the aspect ratio of an exit configuration of the slit type nozzle for the fuel injection and to device the methods of combustion／mixing enhancement. The results show that both inside inflow and slit side vertices should be considered from a viewpoint of the mixing. The combustion efficiency becomes the smallest at aspect ratio, where the aspect ratio is less and more than unity, respectively. The total pressure loss becomes the largest at aspect ratio of unity due to the high penetration. All results imply that a streamwise very long slit is desirable with respect to the combustion and the pressure loss.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.594-603
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• 2002

The characteristics of moisture ventilation in a dry room were studied numerically The effect of three important parameters: position of outlets, aspect ratio($\beta$) of horizontal plane and air exchange rate(N), was analyzed by using the scales of ventilation efficiency. The ventilation performance was evaluated by varying the aspect ratio and air exchange rate in the four types of outlet position. It was shown that the ventilation performance was improved by decreasing the aspect ratio in the longitudinal arrangement of outlet. The highest ventilation performance was determined when $\beta$ was 4 in the transverse arrangement of outlet. Regardless of the aspect ratio, the ceiling arrangement of outlet played more dominant effect on the ventilation efficiency than the floor arrangement. In every type and aspect ratio, the increase of air exchange rate to improve ventilation performance was appropriate up to N=60 /h.

• Journal of Welding and Joining
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• v.26 no.6
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• pp.42-47
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• 2008

TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on A-TIG welding, which use active flux. In this study, the effect of arc length and shield gas on penetration aspect ratio with melt-run welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Aspect ratio was the highest with Ar-2.5% $H_2$ mixed gas.