• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.449-450
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• 2010

• 디지털융복합연구
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• 제14권12호
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• pp.525-535
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• 2016

본 연구는 고등학교 야구선수를 대상으로 운동 전 탄력밴드를 이용한 1회성 동체 PNF 스트레칭 운동을 통해 동체의 관절가동범위 및 구속변화에 어떠한 영향을 주는지를 알아봄에 연구의 목적이 있다. 이를 위하여 현재 I 광역시 소재 고등학교 소속 야구선수 11명을 대상으로 동체 PNF 스트레칭을 던지는 팔을 중심으로 전방 및 후방향으로 각 30회 실시한 후 동체 관절가동범위와 구속을 측정하였으며, 결과는 다음과 같다. 첫째, 동체 PNF 스트레칭 운동 후 동체 관절가동범위는 유의한 증가를 보였다. 둘째, PNF 스트레칭 운동 후 최고, 최저 및 평균구속은 유의하게 증가하였다. 셋째, PNF 동체스트레칭 운동 후 선수들의 투구시 힘듦 정도는 유의하게 감소하였다. 이러한 결과는 야구선수들의 탄력밴드를 이용한 1회성 동체 PNF 스트레칭 운동을 통해 ROM 증가 및 구속증가를 기대할 수 있음을 나타낸다.

• 한국정밀공학회지
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• 제15권8호
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• pp.81-87
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• 1998

High-speed machining is one of the most effective technologies to improve productivity. Because of the high speed and high feedrate, high-speed machining can give great advantages for the machining of dies and molds. In this paper, high-speed machining for HP-4 die material was carried out with a coated tungsten carbide ball endmill. In the high-speed machining, the cutting force and surface roughness of workpiece show various characteristics in different cutting conditions. Especially, the surface roughness of the workpiece depends largely on pick feed and feed-per-revolution of the ball endmill. In the condition where pick feed and feed-per-revolution are equal, better surface roughness is measured. By obtaining good surface roughness at high speed, efficiency of machining can be increased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.36-40
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• 1996

The high-speed machining is one of the most effective technology to improve productivity. Because of the high speed and high feedrate, high-speed machining can give great advantages for the machining of dies and moulds. In this paper, high-speed milling for HP-4 die material was carried out with coated tungsten carbide ball endmill. In the high-speed machining, the cutting force and surface roughness of workpiece show very various characteristics at different cutting conditions. Especially surface roughness of workpiece depends largely on pick feed and feed per revolution of ball endmill. In the condition that pick feed and feed per revolution are equal, better surface roughness is measured. By obtaining good surface roughness at high speed, efficiency of machining can be increased.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.168-172
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• 2009

최근 체감형 스포츠 게임이 늘어나면서 실제 사용자의 동작을 인식하는 연구가 활발히 진행 중이다. 그 중에서도 골프에 관한 연구가 활발하다. 본 논문에서는 고속CCD카메라를 이용하여 골프공의 비행데이터를 측정한다. 고속CCD카메라는 촬영 시, 한 장의 이미지에 여러 번의 노출을 이용하여 고속으로 촬영하여 획득한 영상은 영상처리과정을 통하여 촬영된 공의 위치를 측정한다. 계산된 골프공의 위치는 물리공식을 이용하여 골프공의 비행데이터인 속도, 날아가는 방향을 계산한다. 본 시스템은 향후 비행하는 골프공뿐만 아니라, 야구, 테니스 등과 같은 타격 스포츠에서 체감형 게임 형태로 적용이 가능하다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.86-93
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• 1996

The lubrication characteristics of high-speed ball bearings has been investigated empirically using 45mm bore split inner ring ball bearings employed in small industrial gas turbine engines with oil-jet lubrication method. For the close structural simulation, experiments carried out with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be directly applied to the design and the development of gas turbine engines. Testing was done by varying operating speeds, axial load on bearings, and lubricant flowrates. During testing, the temperature of bearing at outer-ring face, the power consumption of the driving motor, and the rotating resistance of the bearing were measured. From this study, the representative factors for lubrication characteristics at high speed was found, and the most important one was not operating speed but axial load up to 1.95 million dmN speed and 303 kgf axial load. Furthermore, the detailed variation of the rotational resistance of the bearing could be visualized by measuring the change of the radial load under the bearing supports. The rotational resistance consists of the frictional resistance and the bearing-cavity oil resistance.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.239-244
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• 1997

Recently, the high speed rotation and accuracy is needed in the field of electro-optic devices. But it is difficult for ball bearing to satisfy such conditions. So, we have developed the hemispherical type aerodynamic bearing for LSU(Laser Scanning Unit) motor. The hemispherical type aerodynamic bearing is able to support radial and axial load simultaneously. In this research, We have developed mass production method and tested the perromance of aerodynamic bearing in comparision with ball bearing at the speed of 23,000rpm. In the result, we proved that the properties of aerodynamic bearing is better than ball bearing's.

• 한국정밀공학회지
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• 제27권7호
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• pp.49-54
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• 2010

The cryogenic ball milling was performed on carbon nanotubes (CNTs) at an extremely low temperature to increase the dispersion of CNTs. The effects of milling speed and time on the deagglomeration and structural changes of CNTs were studied. FESEM was used to analyze the dispersion and the change of particle size before and after milling process. Transmission electron microscopic (TEM) analysis was also investigated the effect of cryogenic ball milling on the morphological characteristics of CNTs. The structural changes by the cryogenic ball milling process were further confirmed by x-ray diffraction (XRD) and Raman spectroscopic analysis. The results showed that the agglomeration of CNTs was significantly reduced and amorphous structure was observed at high milling speed. However, the milling time has no great effect on the dispersion property and structural change of CNTs compared with milling speed.

• 한국재료학회지
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• 제26권11호
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• pp.611-622
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• 2016

Particle morphology change and different experimental condition analysis during composite fabrication process by traditional ball milling with discrete element method (DEM) simulation were investigated. A simulation of the three dimensional motion of balls in a traditional ball mill for research on the grinding mechanism was carried out by DEM simulation. We studied the motion of the balls, the ball behavior energy and velocity; the forces acting on the balls were calculated using traditional ball milling as simulated by DEM. The effect of the operational variables such as the rotational speed, ball material and size on the flow velocity, collision force and total impact energy were analyzed. The results showed that increased rotation speed with interaction impact energy between balls and balls, balls and pots and walls and balls. The rotation speed increases with an increase of the impact energy. Experiments were conducted to quantify the grinding performance under the same conditions. Furthermore, the results showed that ball motion affects the particle morphology, which changed from irregular type to plate type with increasing rotation speed. The evolution was also found to depend on the impact energy increase of the grinding media. These findings are useful to understand and optimize the particle motion and grinding behavior of traditional ball mills.

• PNF and Movement
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• 제18권3호
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• pp.343-350
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• 2020

Purpose: The purpose of this study was to determine how a shoulder complex stabilization exercise affects ball control and ball speed in elementary school baseball players with an instable scapula. Methods: The subjects of the study were 16 baseball players attending S elementary school in Kwangju Metropolitan City. A shoulder complex stabilization exercise was conducted three times per week for one hour for four weeks. Then, the participants were divided into a scapular instability group or stability group based on their lateral scapular slide test scores. The measurement tool was measured using the target, the ball speed tester (PR1000-BC). All inspections were measured before and after the mediation period to examine the change in the subjects according to the mediation period. Results: As a result of measuring ball control, there was a statistically significant difference in the variation over time (p < 0.05), and there was no statistically significant difference in the interaction between time and group (p > 0.05). As a result of the test of effectiveness between subjects, there was no statistically significant difference found among the groups (p > 0.05). In terms of ball speed, there was no statistically significant difference found in the variation over time (p > 0.05) as well as in the interaction between time and group (p > 0.05). In terms of the effectiveness between subjects, there was no statistically significant difference found among the groups (p > 0.05). Conclusion: It was found that the shoulder complex stabilization exercise could improve ball control for elementary school baseball players. It is believed that this will help prevent and solve possible sport damages experienced during training or competitions, thereby helping athletes use training methods to improve their exercise capacity and continue their careers.