• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1496-1500
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• 2008

Less than 1 % directional error in the range of 5 meters in the green could cause a stroke or more. Although there are several reasons offsetting the direction of the golf ball, lie angle and sidespin effect are the most crucial factors of the putting game. Simple equation is conformed to the experimental results of the deviation of the directional error in all distance. Also, the experimental results of the putting robot show that there are significant side spin effects.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.727-734
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• 2021

The purpose of this study was to analyze correlation between kinematic variables and ground slope perception ability during golf putting. 16 collegiate golfers were participated. To collect and analyze the kinematic data of putter head, SAMPutt lab was used(70 Hz). It was performed Pearson's correlation analysis using SPSS. The level of significance was at .05. As a results, right was correlated with backswing in flat. Toe-up was correlated with follow-through and left was correlated with aim, backswing, impact, follow-through, and loft in slice 1°. Toe-down was correlated with aim, backswing, impact in slice 2°. Toe-up was correlated with follow-through in hook 2°. In conclusion, it is important to improve the putting stroke through repetitive ground slope perception training.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.870-874
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• 2007

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1127-1132
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• 2007

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

• Korean Journal of Applied Biomechanics
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• v.31 no.1
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• pp.44-49
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• 2021

Objective: The purpose of this study was to analyze kinematic variables according to ground slope angle during golf putting. Method: 26 collegiate golfers (age: 22.54±2.15 kg, height: 174.64±6.07 cm, weight: 71.35±9.27 kg, handicap: 5.11±4.50) were participated, and 8 motion capture cameras (250 Hz), Nexus, and Kwon3DXP software were used to collect data. It was performed repeated measures ANOVA and Bonferroni adjustment. Alpha set at .05. Results: Body alignments were not significantly different at address. Putter head trajectory and loft angle were significantly different, and AP direction of acceleration of putter head was significantly different. However, ML and SI direction of acceleration of putter head were not significantly different. Conclusion: Therefore, it was identified that ground slope angle was affected the kinematic variables during putting, and it will be performed that correlation analysis between putting success rate and kinematic variables according to ground slope angle during golf putting.

• Journal of the Korean Applied Science and Technology
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• v.36 no.3
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• pp.789-796
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• 2019

The purpose of this study was to compare kinematic variables between elite golfer and novice during golf putting. 23 elite golfers and 19 novice were participated, and SAM Putt was used to collect kinematic variables. To identify main effect and interaction effect, it was performed Two-way Mixed ANOVA at a significant level of a .05. Elite and novice group, follow-through was significantly different and indicated main effect between distance and skill level. Impact, backswing, and loft angle were significantly different and showed main effect between skill level. Also, backswing rhythm and impact timing were significantly different and indicated main effect between skill level. Therefore, minimizing the movement of the wrist and keeping the putting strike rhythm may improve the putting ability.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1190-1199
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• 2020

The purpose of this study is to analyze the variables affecting the effective stroke in the swing performed through 12 weeks of training for golf beginners, and to provide basic data on the effective stroke factors for the golf beginners to settle on the fairway. Twenty subjects were participate in the study (age: 21.35±1.69 yrs, height: 176.75±7.99 cm, weight: 70.70±9.76 kg). All subjects were subjected to a 12-week golf training, and trackman 4 was used in the 12th week to calculate variables affecting the effective stroke during a golf swing. Trackman data was divided into club-variables and ball-variables, and a binary logistic regression analysis was performed to find out the variables affecting effective strokes. In club-variables, high dynamic loft and low face angles were found in effective stroke, and in ball-variables, fast ball speed, large smash factor, high launch angle, and many spin rates were also found in effective stroke. As a result of the binary logistic regression analysis of club-variables, the probability of an effective stroke increased as the club speed and dynamic loft increased, and the probability of an effective stroke decreased as the face angle increased. The influence of effective stroke in the club-variables was in the order of dynamic loft, face angle, and club speed. In the ball-variable, the probability of an effective stroke increased when the lunch angle increased, and the probability of an effective stroke decreased as the lunch direction increased. As a condition to increase the probability of effective stroke based on the results, it is necessary to increase the club speed through high dynamic loft and low face angle during swing through continuous practice. Through this, the probability of effective stroke through increasing the launch angle and decreasing the launch direction will increase.

• International Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.14-21
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• 2016

This paper presents research on predicting the possible intercept time for a Nodong missile based on its flight trajectory. North Korea possesses ballistic missiles of various ranges, and nuclear warhead miniaturization tests and ballistic missile launch tests conducted last year and in previous years have made these missiles into a serious security threat for the international community. With North Korea's current miniaturization skills, the range of the nuclear capable Nodong missiles can be adjusted according to their use goals and operating environment by using a variety of adjustment methods such as payload, fuel mass, Isp, loft angle, cut-off, etc., and therefore precise flight trajectory prediction is difficult. In this regards, this research performs model simulations of the flight trajectory of North Korea's domestically developed Nodong missiles and uses these as a basis for predicting the possible intercept times for major ballistic missile defense systems such as PAC-3, THAAD, and SM-3.

• Korean Journal of Applied Biomechanics
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• v.20 no.2
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• pp.231-237
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• 2010

The moving trajectory of a golf ball is mainly determined by the angles of the clubface and the trajectory of the club shaft. This paper presents a computer program for analyzing the position and angles of the club while the club moves in a circular motion. For this purpose, a mathematical algorithm was developed and implemented on the experimental data(5 m and 10 m carries) using VC++ and OpenGL. A skilled female golfer(174 cm, 65 kg, 0 handicap) was participated in data collection for the short approach shots. An iron club(Titleist 52 degree, 91.5 cm length, 450 g mass), attached with five reflective markers(12 mm), was used to collect experimental data. However, exact 3D coordinates and angles of the clubface are not directly calculated from measured data. A reverse engineering platform(Minolta Vivid910 hardware and Rapidform software) was thus employed to acquire the scanned data of the clubface. The scanned data and measured data were first aligned by applying appropriate coordinate transformations, and then exact coordinates and angles of clubface could be obtained at each position during circular motion. The program(Club Motion Analysis 1.0) exports the open, heel, loft angles of the club.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.9-16
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• 2015

This research focuses on analysis of the flight trajectory characteristics of SLBM (Submarine Launched Ballistic Missile) of North Korea. Recently, North Korea tested launching of SLBM which is threatening international security. Also it is known that North Korea had possessed the technologies about SLBM since they disassembled submarines out of commission of the former Soviet Union. If the development of the SLBM of North Korea is completed, it should be affected as asymmetric threat to South Korea. Therefore, for active respondence to these threat, it is essential to analyze the SLBM systematically. In this point of view, this work made a SLBM flight model and simulated. In addition, we controled flight trajectories according to adjusting loft angle and described their characteristics. The sea-based ballistic missile defense system is required for an effective response to the flight trajectory of the SLBM from mid-course to terminal phase.