• 한국운동역학회지
• /
• 제17권1호
• /
• pp.91-97
• /
• 2007

The purpose of this study was to investigate the changes of various balls velocity under the different surface conditions after impact. For this study, four different balls were used which are golf ball, tang-tang ball, table tennis ball, and iron ball. And two different types of ground conditions were used which are artificial grass green and glass green. Movements of putter head and ball were recorded with 2 HD video cameras(60 Hz, 1/500s shutter speed). Small size control object($18.5cm{\times}18.5cm{\times}78.5cm$) was used in this study. To transfer the same amount of kinetic energy to the ball, pendulum putting machine was used. Analyzing the process of impact and the ball movement, a putter was digitized the whole movement but the ball was digizited within the 50cm movement. Velocities were calculated by the first central difference method(Hamill & Knutzen, 1995). Putter head velocities were about 112.2cm/s-116.2cm/s at impact. Maximum ball velocities were appeared 0.08s-0.10s after impact no matter what the ground conditions are. Table tennis ball recorded higher ball velocities than the other ball velocities and iron ball recorded the lowest ball velocity in this group. But Table tennis ball was influenced with the frictional force and immediately was decreased at the artificial grass green condition. If an object is received the kinetic energy under the static condition(v=0cm/s), the object recorded the maximum velocity shortly after the impact and then decreased the velocity because of the frictional force. The ball distance from the start position to the peak velocity position is about 6cm-10cm under the 112.2cm/s-116.2cm/s putting velocity with putter. 0.25 seconds later after impact balls were placed 40cm distance from the original position except iron ball. In this study, ball moving distances were too short therefore it was not possible to investigate the reactions after the translational force is disappeared. Rotational force would play a major role at the end of the ball movement. Future study must accept two things. One is long distance movement of ball and the other is balanced ground. Three-piece ball is a good item to investigate the golf ball movement on the different surface conditions.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.993-993
• /
• 2014

Increasing the density magnetic recording of a hard disk drive needs to improve position control of a slider. We have troubles analyzing position of a slider by nonlinear property of pivot ball bearing. Many researches analyze a hard disk drive to change pivot ball bearing part from balls to springs. Pivot ball bearing operates by rotation and movement of balls. This study considers Hertzian contact force when balls contact with outer race to analyze nonlinear movement of a ball bearing. Experiment of this study measures movement of a circular center of a pivot ball bearing. We also verify the simulation results and the experiment results.

• 한국운동역학회지
• /
• 제14권3호
• /
• pp.191-202
• /
• 2004

The batting performance in baseball is a repetitive movement. In order to make the stabilization of posture and the efficient shift of body weight, both the range of stance and stride are important. The previous studies explained that the consistent stride which included the amount of time, stance, and direction were needed. However, the batting performance is frequently changed according to the several speed of ball. Therefore, this study was to analyze the reaction time, the range of stance, the change of stride, and the change of GRF during the batting movement in three kinds of ball speed (120km/h, 130km/h, & 140km/h). Seven elite players are participated in this study. 1. The reaction time of the stride phase was short whereas the time of the swing phase was long according to the increasing ball speed. 2. The range of the stance was wide and the mediolateral direction of the stride was decreased according to the increasing ball speed. 3. In the three kinds of ball speed, the change of body weight was transferred to the center, the rear foot, and the front foot directions. The ball speed of 130km/h showed the high frequency of the suitable batting. At this ball speed, the movement of the body weight was shifted smoothly and the value of the Ground Reaction Force was large enough.

• International journal of advanced smart convergence
• /
• 제10권1호
• /
• pp.134-141
• /
• 2021

The purpose of this study is to investigate the effect of the elderly's motivation to participate in ball games on social support and subjective feelings of happiness. The subjects of this study were elderly people aged 65 or older who lived in Gwangju in 2020 and participated in the ball game movement. Besides, 150 males, 150 females, and 300 total subjects were selected using the convenient sampling method. The survey tool focuses on the motivation for participation in ball game movement, social support, and subjective happiness, and the data collected using this are used for the SPSS 20.0 version, and use statistics are processed according to the purpose of analysis. The results obtained through this research process are as follows. First, it was found that the elderly's motivation to participate in ball game exercise partially affected social support. Second, it was found that the elderly's motivation to participate in ball game exercises had a partial effect on subjective happiness. Third, it was found that the elderly's social support partially affected the subjective feelings of happiness.

• 한국응용과학기술학회지
• /
• 제36권2호
• /
• pp.448-455
• /
• 2019

본 연구는 오르막 퍼팅 시 좌, 우 경사에 따른 볼의 움직임이 어떻게 변화되는지에 대해 알아보는 것을 목적으로 한다. 본 연구를 위해 한국프로골프협회에서 15년 이상의 골프경기 경험이 있는 피험자들이 참여하였고, 본인들의 퍼터를 이용하여 실제 그린과 유사한 환경에서 퍼팅 동작을 수행하였다. 비디오 카메라를 이용하여 피험자들의 오르막 그린 경사에 따른 퍼팅 동작을 수집 후 동작분석을 실시하였으며, 통계적 유의수준을 a=.05로 설정하였다. 연구결과로 좌, 우 경사별 오르막 퍼팅에서 볼의 위치가 왼쪽에서 오른쪽으로 위치 할 때 볼 움직임의 속도와 각속도가 증가하는 것이 확인되었으며, 여러 경사도 중 성공률을 높여야 하는 오르막 퍼팅에서 경사에 따른 어드레스 볼 위치를 변화할 때, 임팩트 시 클럽 페이스와 볼 움직임이 어떻게 변화하는지를 검증하고, 현장적용 측면에 도움을 주는 과학적 자료를 제시하고자 본 연구를 진행하였다.

• Steel and Composite Structures
• /
• 제46권5호
• /
• pp.669-672
• /
• 2023

In this research, the researcher has examined the factors affecting the movement of the soccer ball and will show that the effects such as air resistance, altitude above sea level, wind, air pressure, air temperature, air humidity, rotation of the earth, changes in the earth's gravitational acceleration in different areas. It, the geographical length and latitude of the launch point, the change of gravitational acceleration with height, the change of pressure with height, the change of temperature with height and also the initial spin (Magnus effect) affect the movement of projectiles (especially soccer ball). We modelled th ball based on shell element and derive the motion equations by energy method. Finally, using numerical solution, the wave of the ball is studied. The influences of various parameters are investigated on wave propagation of the ball. Therefore, in short, it can be said that the main factors that play a major role in the lateral deviation of the hit ball are the initial spin of the ball and the wind.

• 한국공작기계학회논문집
• /
• 제10권4호
• /
• pp.97-103
• /
• 2001

The study on the high-speed machine tool is very important for the improvement of productivity since it can shortens cutting and non-cutting time. Especially, high speed of feed drive system is the major research field. In the industries of the advanced countries, the feed drive systems at the speed of 60 m/min have been already developed based on the high lead ball screws. In this study, a high speed feed drive system at the speed of 60 m/ min has been developed, and its movements characteris-tics are investigated. As the movement characteristics, positioning accuracy, angular accuracy, straightness and micro step-response are measured. Thermal characteristics of the system is also discussed. For measuring the movement characteris-tics, a laser interferometer, a memory-based Hi-coder and a cooling device are used. The experimental results confirm that the movement characteristics and the thermal behavior of the system are satisfactory in the aspect of accuracy and stability.

• Advances in nano research
• /
• 제14권4호
• /
• pp.329-334
• /
• 2023

Organic ferroelectric material found vast application in a verity of engineering and health technology fields. In the present study, we investigated the application of the deformable organic ferroelectric in motion measurement and improving performance in tennis players. Flexible ferroelectric material P(VDF-TrFE) could be used in wearable motion sensors in tennis player transferring velocity and acceleration data to collecting devises for analyzing the best pose and movements in tennis players to achieve best performances in terms of hitting ball and movement across the tennis court. In doing so, ferroelectric-based wearable sensors are used in four different locations on the player body to analyze the movement and also a sensor on the tennis ball to record the velocity and acceleration. In addition, poses of tennis players were analyzed to find out the best pose to achieve best acceleration and movement. The results indicated that organic ferroelectric-based sensors could be used effectively in sensing motion of tennis player which could be utilized in the optimization of posing and ball hitting in the real games.

• 한국운동역학회지
• /
• 제16권3호
• /
• pp.183-188
• /
• 2006

This research is to know differentiation of CP(center of pressure) pattern among four pitching sort(straight ball, raise ball, change up ball, drop ball). Subject are three national or junior athletes. We use the one camera, Novel Win pressure measurement system. Conclusions are as follows : 1. When we throw the straight ball, CP of left foot is effective to end movement at middle of foot in body balance on arm angular motion and enhanced speed. 2. When we throw the raise ball, to change CP from middle to post is more effective in order to raise the ball. 3.In drop ball pitching, in order to fall down the ball in front of hitter, CP of left foot move from post foot to interior part of forefoot 4. In change up ball pitching, if CP of left foot move into forefoot, it is a cause of high ball and hitter can recognize the change up ball because of late arm rotation motion.

• 대한임상전기생리학회지
• /
• 제5권2호
• /
• pp.35-45
• /
• 2007

The purpose of this study was to examine spiral way movement of a trunk exerts on the movement ability. The details established to achieve for this article. This examination confirmed the weight, weight/height2 index, ratio of lumbar to pelvic, musculoskeletal quantity, push up for 2 minute, pitch a ball and voluntary isometric contraction with flexion and extension of knee joint of the subjects with spiral direct movement. Healthy eighteen subjects who understand fully the significance of procedure, consented to a plan, without neuromuscular disease were participated in two groups of experiment. The group were a spiral movement(9), rectilinear movement(9). Trunk movement tested 2 sessions of a spiral movement and rectilinear movement with a push up for 2 minute, 5days per a week, for the 4 weeks. This experiment tested 3 times with a sufficient rest for fatigue limitation. An analysis of the results used a paired samples t-test for difference from before and after experiment. The following results were obtained; At an internal change of the body, the musculoskeletal quantity was increased significantly to spiral movement group, but the weight was increased significantly, the musculoskeletal quantity was not significant to rectilinear movement. The movement ability evaluation for a external change was increased significantly in a push up for 2 minute, pitch a ball, isometric contraction with extension of knee joint of a spiral movement group, but a push up for 2 minute was increased significantly in a push up for 2 minute on the abdominal muscle training of a rectilinear movement group. As compared with a rectilinear movement, a spiral movement was more effect by cooperation with nerve and musculoskeletal system and an increase in movement ability was caused by learning acknowledgment, muscular reeducation. These results lead us to the conclusion that a spiral movement of trunk was more effect than a rectilinear movement, the coordination of nerve and musculoskeletal system was of importance of Multi-direction movement. Therefore, A further studies concerning the therapeutic exercise intervention and active-dynamic analysis could enhance the development of the most effect on the trunk.