• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.456-463
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• 2007

It is important to improve the initial launch conditions of golf ball at impact between golf club and ball to get a long flight distance. The flight distance is greatly influenced by the initial launch conditions such as ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. Back spin rate is created by the contact time and force. 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 ball, and the tangential force creates the spin. Especially, the tangential force is known to take 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 in the literature. In this paper, 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 time at impact between golf club head and ball are computed using FEM and compared with previous results. In addition, we investigate the impact phenomenon between golf club head and ball by FEM and clarify the mechanism of ball spin creation accurately, particularly focusing on the effect of negative tangential force on ball spin rate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1017-1022
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• 2007

It is important to improve the initial launch conditions of golf ball at impact between golf club and ball to get a long flight distance. The flight distance is greatly influenced by the initial launch conditions such as ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. Back spin rate is created by the contact time and force. 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 ball, and the tangential force creates the spin. Especially, the tangential force is known to take 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 in the literature. In this paper, 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 time at impact between golf club head and ball are computed using FEM and compared with previous results. In addition, we investigate the impact phenomenon between golf club head and ball by FEM and clarify the mechanism of ball spin creation accurately, particularly focusing on the effect of negative tangential force on ball spin rate.

• 한국체육학회지인문사회과학편
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• v.54 no.5
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• pp.829-840
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• 2015

The purpose of this study was to investigated into the kinematics and ground reaction force for gait on induced stereoacuity in normal subjects with normal sight. Eighteen subjects who passed the stereoacuity testing were participated in the experiment(age: 22.1±2.7 years, height: 176.8±4.4 cm, weight: 67.6±5.8 kg). The study method adopted 3D analysis with six cameras and ground reaction force with two force-plates. The results were as follows; In gait velocity, obstacle crossing gait was slower than flat gait. In angular displacement of hip joint, mostly obstacle crossing gait was more flexed than flat gait. In angular displacement of knee joint, obstacle crossing gait was more flexed than flat gait, and stereoacuity reduction gait in TO and FC2 were more flexed than normal vision gait. In angular displacement of ankle joint, obstacle crossing gait in FC2 was more flexed than flat gait. In trunk tilt, obstacle crossing gait in MSt, TO and MSw were more extended than flat gait. In GRF, there was no significant in Fx, obstacle crossing gait in right and left foot were bigger propulsion force than flat gait, obstacle crossing gait in right and left foot were bigger braking force than normal vision gait in Fy, and obstacle crossing gait in right and left foot were bigger than flat gait in peak F1 and peak F2 of Fz, and stereoacuity reduction gait in right foot was lower than normal vision gait in valley force of Fz.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.64-71
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for different jet flow conditions including jet pressure and jet Mach number. The results show different behavior of normal force and moment variation according to jet pressure variation and jet Mach number variation. From the detailed flow field analyses, it is verified that most of the normal force loss and the pitching moment generation are taken place at the low-pressure region behind the jet nozzle. Furthermore, it is shown that the pitching moment can be efficiently reduced by obtaining the lateral thrust through higher jet Mach number rather than through high jet pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.27-34
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for several parameters such as angles of attack, circumferential jet positions, and spouting jet angles. Missile surface is divided into four regions with respect to the center of gravity, and the normal force and moment distribution at each region are compared. The results show different behavior of the normal force and moment variation according to each parameter. Furthermore, it is shown that the pitching moment can be minimized through proper combination of each parameter.

• Tribology and Lubricants
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• v.29 no.2
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• pp.91-97
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• 2013

Quantifying the nanoscale force between the atomic force microscopy (AFM) probe of a force-sensing cantilever and the sample is one of the challenges faced by AFM researchers. The normal force calibration is straightforward; however, the lateral force is complicated due to the twisting motion of the cantilever. Force measurement in a liquid environment is often needed for biological applications; however, calibrating the force of the AFM probes for those applications is more difficult owing to the limitations of conventional calibration methods. In this work, an accurate nondestructive lateral force calibration method using multiple pivot loading was proposed for liquid environment. The torque sensitivity at the location of the integrated probe was extrapolated based on accurately measured torque sensitivities across the cantilever width along a few cantilever lengths. The uncertainty of the torque sensitivity at the location of the integrated tip was about 13%, which is significantly smaller than those for other calibration methods in a liquid environment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.141-148
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• 2003

In the recently, the necessity of the hybrid type linear stepping motor(HLSM) of linear motion digital actuator has been increased in the various fields of the automatic control system. The HLSM is directly performed without any converting mechanism. Therefore, the HLSM is better advantaged in the efficiency and economical view than a rotary stepping motor. In this paper, we have designed an optimum tooth shape by the 2D finite element method(FEM) to develop the HLSM with longitudinal flux machine(LFM) type, and calculated the thrust force and normal force. And we have manufactured the prototype of it, and have experimented the thrust force characteristics of it.

• Journal of Oral Medicine and Pain
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• v.18 no.1
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• pp.21-29
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• 1993

The purpose of this study was to evaluation of temporomandibulr joint space according to increasing the occlusal force on working and non-working side during unilateral bite. For the study, 22 normal adults, age ranged from 23 to 25, who had no symptoms on TMJ area and masticatory muscles and had normal or class I molar relationship were selected. Transcranial TMJ radiograph was taken during unilateral biting with sensor of Bite force checker (Nihon Kohden Kygyo Co.Ltd., Japan) on each 1st molar teeth of right and left side which were forced each 0Kg, 10Kg, 20Kg and 30Kg by use of Accurad-200 (Denar Corperation's product). The radiographs were traced on the screen, which was magnified by 5. The size of temporomandibular joint space at anterior, superior and posterior compartment were measured with Dumas's method (reference line of between squamotympanic fissure and the most inferior point of articular eminence). On the basis of this study, the following results were obtained. 1. Size of anterior TMJ space was tend to decrease on the working side and increase on the non-working side according to increasing the occlusal force, but not significant statistically (p>0.05). 2. Size of superior TMJ space was tend to increase on the working side and decrease on the non-working side according to increasing the occlusal force (p<0.05). 3. Size of posterior TMJ space was tend to decrease on both working ad nonworking side, but non significant statistically.

• Geotechnical Engineering
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• v.3 no.4
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• pp.21-30
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• 1987

The purpose of this paper is to develop a method of slope stability analysis, using slice method The direction of interstice forces was assumed in two ways: 1) inclined interslice force parallel to the base of slice, 2) normal interslice force normal to the boundary surface of slice being used in the existing slice method. The deviation from the value of interstice force caused by assumption was removed in the Processing of analysis, and the factor of safety was obtained more accurately by deciding the location of interstice force acting on each slice. More rational validity of the method with inclined interslice force was proved by performing slope stability analyses with both methods. The factor of safety obtained by the proposed method was compared with that by the existing methods, and the influence of seismic coefficient was also analyzed.

• Journal of Biomedical Engineering Research
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• v.34 no.4
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• pp.197-203
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• 2013

The purpose of this study was to analyze the asymmetry of the reaction forces on lower limbs between dominant and nondominant sides during sit-to-stand movement in normal subjects. Fourteen normal subjects ($22.6{\pm}2.3yrs$, all men) participated in this study. To measure the reaction forces during sit-to-stand movement, two force plates were mounted on the ground and one dual top force plate was mounted on a chair. Five events(movement onset, max thigh reaction force, transition, max hip angle, seat off) were determined from the reaction force and joint angle trajectories. For each of thigh, foot, and total reaction forces, two-way ANOVA was performed with the events and sides as factors. Also investigated was the leg asymmetry expressed as the ratio of the reaction forces of dominant and nondominant sides. The significance of asymmetry was investigated and two-way ANOVA was performed with the events and body parts(foot, thigh and total) as factors. Thigh reaction force and total reaction force showed interaction of events and leg sides(p < 0.01). Post-hoc comparisons showed they were different between sides at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Asymmetry was also significant at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Interaction of events and body parts on asymmetry was significant(p < 0.01) and asymmetry was greater in thigh reaction forces than total and foot reaction forces at the events of the latter stage(p < 0.01). The results suggest that asymmetry exist in normal subject and should be fully considered when investigating sit-to-stand strategy of patients.