• Title/Summary/Keyword: Ball speed

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Comparison of the basic Aerodynamics between the World Cup Official Ball and Korean Soccer Balls (월드컵 공인구와 한국 축구 공인구 사이의 기초 공력특성 비교)

  • Sungchan Hong
    • Korean Journal of Applied Biomechanics
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    • v.34 no.2
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    • pp.63-70
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    • 2024
  • Objective: This study aims to compare the basic aerodynamic characteristics of the official Qatar World Cup soccer ball with those of the official Korean soccer balls. Method: In this study, wind tunnel experiments were conducted to compare the fundamental aerodynamic properties of two commonly used domestic soccer balls, the Star and Nassau, with the Al Rihla, the official ball of the 2022 Qatar World Cup. Results: The findings revealed that the Nassau soccer ball exhibited changes in aerodynamic characteristics depending on its orientation, particularly at low speeds (below 15 m/s), while the Al Rihla showed variations in aerodynamic characteristics at medium to high speeds (15 m/s to 35 m/s) based on its orientation. Furthermore, the results of lift and side force variations indicated that the Star soccer ball exhibited larger changes compared to other soccer balls, suggesting that it may exhibit the most irregular flight path during strong shots (around 30 m/s or approximately 100 km/h). However, there were no differences in aerodynamics observed among the soccer balls in the medium-speed range (20~25 m/s). Conclusion: The comparison of aerodynamics between the Korean soccer balls and the most recently used World Cup official ball showed that, while the Korean balls exhibited slightly greater changes in lift and side forces compared to the World Cup ball, there were no significant differences in most of the aerodynamic characteristics.

Ball movements in various surface angles of uphill putting based on different ball positions (오르막 퍼팅 동작 시 볼의 위치가 퍼터와 볼의 움직임에 미치는 영향)

  • Ryu, Jong-Wook;Kim, Jai-Jeong
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.2
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    • pp.448-455
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    • 2019
  • This study aims to discover whether there are other factors, such as the ball position and address that will increase the percentage of holed putts from different angles of surface. In this study, we selected five male tour professional golfers that has been of 15 years or longer on the Korea Golf Association. As a research tool, after installing a video camera at an artificial site that's similar with the real green, and with the player's own putter, motion analysis was carried out using a Titleist V1x, which is commonly used by golfers. We use SPSS programs, significance level a=.05. According to the ball movement during the ball movement during the ball position putt by section, it is confirmed that the ball speed and angular velocity increase as the ball position changes from left to right. If the uphill putt, ball movement was found to be increased same change flat putt and There is no significance deviation. In this study, we investigate how the clubface and ball move during impact by varying the position of the address ball according to the slope during the ascent putt, which should increase the success rate among the various slopes. This study was conducted to present scientific data.

Thermal Analysis of a Motor-Separated Spindle System for High-Speed HMC (모터분리형 초고속 머시닝센터 주축계의 열특성 해석)

  • 김석일;권태균;나상준
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.10a
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    • pp.237-242
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    • 2001
  • This paper presents the thermal characteristics analysis of a high-speed HMC spindle system with angular contact ball bearings, built-in motor, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is composed of the main spindle and sub-spindle which are mechanically connected by a flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front and rear bearings of the sub-spindle. The thermal analysis model of spindle system is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution, heat flow and thermal deformation under the various testing conditions related to material of bearing ball, spindle speed and coolant temperature.

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Friction Analysis of Spindle Bearings

  • Chang, Hun-Keun;Young Sun;Han, Dong-Chul
    • International Journal of Precision Engineering and Manufacturing
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    • v.1 no.1
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    • pp.42-48
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    • 2000
  • Friction in bearing exerts an important effect upon power dissipation and heat generation of spindle system. This paper presents frictional moments derived from rotational axis coordinate system of spindle and frictional characteristics to spindle speed A frictional moment of spindle bearings is derived by work-energy method. Differential sliding moments in outer raceway has a major effect upon frictional resistance; spin sliding moments in inner raceway has a secondary effect. As spindle speed increases, also the frictional moments increase. In high-speed region, ceramic ball bearing 몬 smaller frictional moment than steel ball bearing.

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Thermal Characteristics Analysis of a High-Speed HMC Spindle System (초고속 HMC 주축계의 열특성 해석)

  • 김석일;김기상;김기태;나승표
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.04a
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    • pp.441-446
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    • 2001
  • This paper presents the thermal characteristics analysis of a high-speed HMC spindle system with angular contact ball bearings, built-in motor, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is composed of the main spindle and sub-spindle which are mechanically connected by a flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front and rear bearings of the sub-spindle. The thermal analysis model of spindle system is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution and heat flow under the various testing conditions related to material of bearing ball, spindle speed and coolant temperature.

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A Revolute Robot Manipulator with a New Structure (새로운 구조의 다관절 로봇 매니퓰레이터)

  • Choi, Hyung-Sik;Kim, Young-Sik;Baek, Chang-Yul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.5
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    • pp.539-546
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    • 2004
  • Conventional robot manipulators actuated by motors with the speed reducer such as the harmonic drive have weakness in the load capacity, since the speed reducer does not have enough strength. To overcome this, a new type of the robot actuator based on the four-bar-link mechanism driven by the ball screw was proposed and constructed. Also, a new type of a revolute-jointed robot manipulator composed of the developed actuators was developed. The base axis is actuated by the motor with the conventional speed reducer, but the other axes are actuated by the proposed actuators. The kinematics and dynamics of the robot were analyzed, and the performance test of the robot was made. Through the test results, the performance of superior load capacity versus the robot weight is shown.

The Measurement of Flight Data of Golfball with High-Speed Multi-Exposure Image (고속 다중 노출 영상을 이용한 골프공의 비행 요소 측정)

  • Kim, Ki-Hyun;Park, Hyun-Woo;Ju, Woo-Suk;Lee, Dong-Hoon;Yun, Tae-Soo
    • Journal of Korea Multimedia Society
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    • v.12 no.5
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    • pp.699-707
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    • 2009
  • Recently, while 3D sports game increases, the research that it recognizes the operation of the real user actively progresses. Most of all, the research about the golf is active. In this paper, the camera acquiring in a high-speed multi-exposure image measures the flight data of the golf ball through the image processing. While photographing, the high-speed camera, using this system, exposes an image at regular intervals. And line scan camera checks whether the golf ball passed or not. After the location information of the calculated golf ball calculates a speed and a direction by using the physical formula, it applies the golf simulation. After, this system is possible the measurement of the physical element of the spherical object.

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Study on Fuel Lubrication Performance of a High Speed Rolling Element Bearing (소형 고속 구름베어링의 연료윤활 특성 연구)

  • Kim, Ki-Tae;Kim, Sung-Kyun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.424-426
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    • 2008
  • A parametric study was carried out to find the fuel lubrication performance of high speed small rolling element bearings. Both MIL-PRF-7808 turbine oil and JP-8 aircraft fuel were used as the lubricant to compare the operational characteristics. 17 mm inner diameter deep groove ball bearing and 20 mm cylindrical roller bearing were used. A high speed bearing test rig was developed and the testing was done with varying applied load, cooling air temperature, lubricant flow rate, and speed. Fuel caused more cage wear than oil for ball bearing with increasing axial load and rotational speed. The bearing temperature using fuel was lower than that using oil, and this seems to be the result of the high cooling capacity of fuel. According to various tests, the fuel lubrication is applicable for the lubrication on the main shaft bearings of expendable small gas turbines.

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Analysis of Relationship between Biomechanical Factors and Driver's Distance during Golf Driver Swing (골프 드라이버 스윙 시 운동역학 요인들과 비거리 관련성 분석)

  • Lim, Young-Tae;Park, Jun-Sung;Lee, Jae-Woo;Kwon, Moon-Seok
    • Journal of the Korean Applied Science and Technology
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    • v.38 no.1
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    • pp.1-8
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    • 2021
  • The purpose of this study was to analyze relationship between biomechancal factors and diver's distance during golf driver swing. Fifteen professional golfers were participated in as subject. Eight motion capture cameras(250 Hz), 2 force plates(1000 Hz), and Trackman were used to collect kinematic and kinetic datas. It was performed Pearson's correlation analysis using SPSS 24.0. The level of significance was at .05. Ball speed, club head speed, X-Factor, and ground reaction force were correlated on driving distance, However, smash factor and knee moment were not correlated on driving distnace. Ball speed, club head speed, X-Factor, and ground reaction force were effected to driving distance, but smash factor and knee moment were not effected to driving distance.

Wet Fine Grinding of Rice Husk Ash using a Stirred Ball Mill (교반 볼밀을 이용한 왕겨재의 습식 미세분쇄에 관한 연구)

  • Park, S.J.;Kim, M.H.;Choi, Y.K.
    • Journal of Biosystems Engineering
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    • v.31 no.1 s.114
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    • pp.33-38
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    • 2006
  • This work was conducted to find the operating characteristics of an efficient wet grinding system designed to obtain fine rice husk ash powder. Once the rice husk was combusted and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement. Grinding time (15, 30, 45 min), impeller speed (250, 500, 750 rpm), and mixed ratio (6.7, 8.4, 11.l, 20.9) were three operating factors examined for the performance of a wet-type stirred ball mill grinding system. For the operating conditions employed, mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of $2.83{\sim}9.58{\mu}m,\;0.5{\sim}6.73kWh/kg,\;and\;0.51{\sim}3.27m^2/Wh$, respectively. With the wet-type stirred ball mill grinding system used in this study, the grinding energy efficiency decreased with the increase in total grinding time, impeller speed, and mixed ratio. The difference in specific surface area of powder linearly increased with logarithm in total number of impeller revolution and the grinding energy efficiency linearly decreased. Grinding time of 45 min, impeller speed of 500 rpm, and mixed ratio of 6.7 were chosen as the best operating condition. At this condition, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughput, and specific energy input were $2.84{\mu}m,\;2.28m^2/Wh,\;0.17kg/h$, and 2.03kWh/kg, respectively. Wet fine grinding which generates no fly dust causing pollution and makes continuous operation easy, is appeared to be a promising solution to the automatization of rice husk ash grinding process.