• Journal of the Korean Society of Visualization
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• v.13 no.1
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• pp.15-20
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• 2015

Sensitivity studies of blade angle and twisted angle are numerically investigated to optimize the Savonius blade. As blade angle increases, the contact area between blade and wind decreases, showing the suppression of the vortex generation near blade. Compared to the blade angle of 0 degree, the blade angle of 20 degree shows about 2.6% increment of power efficiency. Based on the blade angle of 20 degree, sensitivity studies of the twisted angle are performed. The result indicates that the adjustment of the twisted angle causes the torque of blade to increase. Optimized blade can suppress the formation of the vortex structure in rear region. Also, wind flows without disturbance of vortex when passing through the optimized blade. The 1kw vertical wind turbine system with optimized blade can generate 4442.2kWh per year and have 53% capacity factor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.123-129
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• 2015

In general, recent critical studies of five-axis machine have tended to center on the question of effective machining to realize complex shape parts. However, the hydrostatic bearing and journal bearing, both of which are involved in the complex process of dividing the processing of internal precision-shape machining, must be optimized. Although the angle head is designed to machine the internal shape as it approaches the inner diameter of the work piece, research on the angle head in five-axis machining has received only minimal attention in domestic industries. In this study, an angle head which is optimized for effective internal shape machining is developed. In pursuit of this purpose, 3D and 2D designs of the angle head for five-axis machining are devised. Reliability is secured through static performance tests and machining accuracy evaluations of the angle head in keeping with the machining accuracy standard of 0.2mm for hydrostatic bearings.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1929-1930
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• 2006

Human like robot arm posture for grasping by considering the shape of the target object is quite a challenge in the field of robotics. In this paper, an optimized grasp posture with respect to the shape of the object considering the wrist joint angle and elbow elevation angle, in order to verify that the grasp posture is human like has been proposed. Given a target object, the candidates for grasp are computed by the method described in this paper. For each candidate, the closed loop inverse kinematics has been solved for the corresponding hand position and orientation. From the obtained joint angles through inverse kinematics, the elbow elevation angle has been computed and compared with the elbow elevation angle obtained through human movement data by the characteristic equation. After considering all the candidates, the hand position and orientation with minimum wrist joint and difference in elbow elevation angles has been utilized as the optimized grasp posture. Simulation results are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.120-128
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• 2000

At the initial design stage of a new vehicle, the chassis layout has the most important influence on the overall vehicle performance. Most chassis designers have achieved the target performances by trial and error method as well as individual knowhow. Accordingly, a general procedure for determining the optimum location of suspension hard points with respect to the kinematic characteristics needs to be developed. In this paper, a method to optimize the toe angle in the double wishbone type front suspension of the four-wheel-drive vehicle is presented using the design of experiment, multibody dynamic simulation, and optimum design program. The handling performances of two full vehicle models having the initial and optimized toe angle are compared through the single lane change simulation. The sensitive design variables with respect to the kinematic characteristics are selected through the experimental design sensitivity analysis using the perturbation method. An object function is defined in terms of the toe angle among those kinematic characteristics. By the design of experiment and regression analysis, the regression model function of toe angle is obtained. The design variables which make the toe angle optimized ae extracted using the optimum design program DOT. The single lane change simulation and test of the full vehicle model are carried out to survey the handling performances of vehicle with toe angle optimized. The results of the single lane change simulation show that the optimized vehicle has the more improved understeer tendency than the initial vehicle.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.16 no.3
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• pp.41-48
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• 2012

Objectives: The aims of this study are to design a optimized mechanical structure of digital tongue imaging system (DTIS) equipped with LEDs in aspects of object distance and camera angle of coverage. Methods and Results: We tried to find optimized object distance while recording a rectangular object of common tongue size. In case object distance is 22 cm or less, edge of the rectangle was not taken beyond the shooting range. In contrast, if object distance is 40 cm or more, the rectangle image was too small. Therefore when considering the variation of subjects, we selected distance of 35-40 cm as appropriate object distance for the DTIS. We also tried to find optimized angle between camera view axis and horizontal line. We photographed from the side of the face of 7 adults with exposed tongue. We drew an exposed tongue lines to connect the tongue tip points and the tongue root points by using the photos acquired from the side faces. And then we calculated the tongue exposure angles between the vertical line and the exposed tongue lines. Mean tongue exposure angle was $28.3^{\circ}$ when tongue was lightly exposed and $13.3^{\circ}$ when maximally. So we determined $73^{\circ}$ as appropriate slope angle of part in contact with face of the DTIS and by considering that the standard variation was great, we designed control gears to adjust the slope of the camera view axis and to regulate the object distance. Conclusions: We designed a optimized mechanical structure in object distance and slope angle of part in contact with face of the DTIS.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.227-228
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• 2008

In the present paper, fowler flap was optimized to maximize the lift with response surface method. Leading edge shape and the gap between main airfoil and flap, were optimized and the aerodynamic characteristics was improved considerably. The optimized flap has more rounded leading edge and bigger gap. Before angle of attack, $10^{\circ}$, lift and drag are improved and the optimized flap shows similar aerodynamic characteristics to the original flap. The flow condition for optimization was angle of attack, $10^{\circ}$, Mach number, 0.2, flap deflection, $40^{\circ}$.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.227-228
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• 2008

In the present paper, fowler flap was optimized to maximize the lift with response surface method. Leading edge shape and the gap between main airfoil and flap, were optimized and the aerodynamic characteristics was improved considerably. The optimized flap has more rounded leading edge and bigger gap. Before angle of attack, $10^{\circ}$, lift and drag are improved and the optimized flap shows similar aerodynamic characteristics to the original flap. The flow condition for optimization was angle of attack, $10^{\circ}$, Mach number, 0.2, flap deflection, $40^{\circ}$.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.414-419
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• 2011

Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

• Journal of computational fluids engineering
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• v.18 no.1
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• pp.1-6
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• 2013

Missile and fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 50 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure, entropy distribution, etc. are analyzed according to the angle of attack. The results of average lift coefficients are compared with other results according to the angle of attack. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. The primary and secondary oscillating frequencies are analyzed by the effects of these unsteady aerodynamic characteristics.

• Journal of the Korean Society of Visualization
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• v.19 no.3
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• pp.123-129
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• 2021

Many plants and animals in nature have superhydrophobic surfaces. This superhydrophobic surface has various properties such as self-cleaning, moisture collection, and anti-icing. In this study, the superhydrophobic properties of PTFE surface were treated by plasma etching. There were four important factors that changed the surface properties. Micro-sized protrusions were formed by plasma etching. The most influential parameter was RF Power. The contact angle of the pristine PTFE surface was about 113.8°. The maximum contact angle of the surface after plasma treatment with optimized parameters was about 168.1°. In this case, the sliding angle was quite small about 1°. These properties made it possible to remove droplets easily from the surface. To verify the self-cleaning effect of the surface, graphite was used to contaminate the surface and remove it with water droplets. Graphite particles were easily removed from the optimized surface compared to the pristine surface. As a result, a surface having water repellency and self-cleaning effects could be produced with optimized plasma etching parameters.