• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1459-1466
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• 2004

The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

• Journal of ILASS-Korea
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• v.8 no.4
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• pp.39-45
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• 2003

The Objective of this study is to investigate the effect of internal swiller angle and swirl chamber aspect ratio of nozzle on spray characteristics for application of spray system in micro fabrication process. The macro-spray characterictics such as the spray angle and breakup process were obtained by photographs illustrating atomization. The micro-spray characteristics such as droplet size and axial velocity were measured by using PDA with swirler angle and swirl chamber aspect ratio. The swiller angles were $13.5^{\circ},\;27^{\circ},\;and\;40.5^{\circ}$. The swirl chamber aspect ratios were 1.2, 1.6, and 2.0. It was found that the smaller swirl chamber aspect ratio was, the larger axial velocity and drop size were.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.1-7
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• 2005

The purpose of this study is to investigate the effect of swirler vane angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single spray. The characteristics of sprat's have been investigated by measuring the spray angle, droplet size and velocity Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler vane angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber The effect of vane angle un the spray characteristics was greater than the aspect ratio of swirl chamber for single spray.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.217-220
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• 2006

The lift and drag forces produced by a wing of a given cross-sectional profile are dependent on the wing planform and the angle of attack. Aspect ratio is the ratio of the wing span to the average chord. For conventional fixed wing aircrafts, high aspect ratio wings produce a higher lift to drag ratio than low ones for flight at subsonic speeds. Therefore, high aspect ratio wings are used on aircraft intended for long endurance. However, birds and insects flap their wings to fly in the air and they can change their wing motions. Their wing motions are made up of translation and rotation. Therefore, we tested flapping motions with parameters which affect rotational motion such as the angle of attack and the wing beat frequency. The half elliptic shaped wings were designed with the variation of aspect ratio from 4 to 11. The flapping device was operated in the water to reduce the wing beat frequency according to Reynolds similarity. In this study, the aerodynamic forces, the time-averaged force coefficients and the lift to drag ratio were measured at Reynolds number 15,000 to explore the aerodynamic characteristics with the variation of aspect ratio. The maximum lift coefficient was turned up at AR=8. The mean drag coefficients were almost same values at angle of attack from $10^{\circ}$ to $40^{\circ}$ regardless of aspect ratio, and the mean drag coefficients above angle of attack $50^{\circ}$ were decreased according to the increase of aspect ratio. For flapping motion the maximum mean lift to drag ratio appeared at AR=8.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.330-336
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• 2021

In bistatic sonar operation, the scattering strength of a sonar target is characterized by the probe signal frequency, the aspect angle and the bistatic angle. Therefore, the target detection and identification performance of the bistatic sonar may vary depending on how the positions of the target, sound source, and receiver are changed during sonar operation. In this study, it was evaluated which variable is advantageous to change by comparing the target identification performance between the case of changing the aspect angle and the case of changing the bistatic angle during the operation. A scenario of identifying a hollow sphere and a cylinder was assumed, and performance was compared by classifying two targets with a support vector machine and comparing their accuracy using a finite element method-based acoustic scattering simulation. As a result of comparison, using the scattering strength defined by the frequency and the bistatic angle with the aspect angle fixed showed superior average classification accuracy. It means that moving the receiver to change the bistatic angle is more effective than moving the sound source to change the aspect angle for target identification.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1522-1527
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• 2004

The purpose of this study is to investigate the effect of swirler angle and swirl chamber aspect ration of nozzle on the characteristics of single and twin spray. The performances of nozzle has been investigated by measurements of spray angle, droplet size, velocity and Weber number at a water pressure 0.4MHz. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the smaller swirler angle, the larger axial velocity became. It was also shown that the larger aspect ratio, the smaller droplet diameter became.

• 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.

• 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 for Precision Engineering
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• v.15 no.12
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• pp.97-105
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• 1998

The fiber oriented condition inside fiber reinforced composite material is a basic factor of mechanical properties of composite materials. It is very important to meausure the fiber orientation angle for the determination of molding conditions, mechanical characteristics, and the design of composite materials. In the work, the fiber orientation distribution of simulation figure plotted by PC is measured using image processing in order to examine the accuracy of intersection counting method. The fiber orientation function measured by intersection counting method using image processing is compared with the calculated fiber orientation function. The results show that the measured value of fiber orientation function using intersection counting method is lower than the calculated value, because the number of intersection between the scanning line and the fiber with smaller fiber aspect ratio is counted less than with larger fiber aspect ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.842-849
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• 2004

The objective of this work is to study the improvement of etching characteristics in wet etching process. The etching characteristics such as etching factor were investigated under different etching conditions and compared with the spray characteristics. The spray characteristics of nozzle with different geometries such as swirler angle and swirl chamber aspect ratio were analyzed by using PDA system to predict the effect of the spray characteristics on the etching factor. The swirler angles were 49,5$^{\circ}$, 63$^{\circ}$ and 76.5$^{\circ}$. The swirl chamber aspect ratios were 1.2, 1.6 and 2.0. It was found that the etching factor was correlated with the spray characteristics and also the smaller swiller angle, the larger etching factor became.