• Journal of the Korean Applied Science and Technology
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• v.38 no.2
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• pp.532-542
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• 2021

The purpose of this study was to investigate the body's strategy through kinematic variables of the lower extremities and ground reaction forces to maintain the club-head speed and ball accuracy despite the three stances during the golf swing. Ten male golfers who official handicap two were participate in the experiment. All subjects performed swing after maintaining the address posture according to stance conditions(square; SS, open: OS, closed: CS). Using a 3D motion analysis system and force plateform, the results were calculated with the 7-iron full swing each stance. In result, there was no difference in center of displacement, and left and right hip and knee joint angle displacement. Left ankle joint was largely plantar-flexed in OS, and right ankle joint was largely performed in CS from the address to the downswing. From address to take-back, right foot had a large left direction and the left foot had a right direction were greater in OS than in CS. Therefore, despite various stances, maintaining the same posture at impact is thought to have a positive effect on club head speed and ball direction.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.135-142
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• 2008

The primary innovation in the new footwear is a heel lift of $20^{\circ}$ which is proposed to improve posture and balance as well as increase shock absorption. The purpose of this research was to compare the movement, forces and muscle activity between the new shoes and standard athletic footwear during standing and walking. Nine healthy subjects participated in this study. Data were collected at two times: 1) when the subjects first wore the new walking shoes and 2) after the subjects wore the shoes for 6 hours a day for two weeks. 1. During standing. the movement of the center of pressure is increased approximately 60% when wearing the new walking shoes compared to a control shoe. 2. During walking. the ankle is approximately $14^{\circ}$ more dorsiflexed during landing due to the 200heel lift in the new walking shoes. The knee compensates slightly by flexing approximately $2^{\circ}$ more. 3. As a result of the changes in the walking movement, the ground reaction forces are applied more quickly, although the peak magnitudes do rut change. 4. The resultant joint moments at the ankle and knee joints decrease from 21-60% with the largest reductions occurring during landing. In conclusion, the new footwear change the movement, showing a more upright stance. Also, the new footwear reduce joint loading at the joint during the landing and weight acceptance phase of walking. However, the influence of the new footwear is immediate and does rut change after wearing the shoes for two weeks.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.167-174
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• 2022

This study investigates the behavior of a jointless bridge that integrates superstructure and abutment without an expansion joint. Based on the sensitivity analyses conducted in previous studies, a shell-based model was determined to be the most suitable numerical analysis model for jointless bridges due to the similarity of the model's results compared with the obtained displacement shape, which was influenced by relative errors, precision, and practical aspects. Accordingly, the behavior of a jointless bridge was analyzed at various wall depths using shell element-based and solid element models. In addition, the results of MIDAS Civil and ABAQUS analysis programs were compared. In the case of semi-integrated bridges (A and B), the displacement decreased as the wall depth increased due to the ground reaction force in Case 1 under a linear spring condition and +30℃. In the case where temperature was -30℃, the change in displacement was small because the ground reaction did not occur. As for bridge C (a fully integrated alternating bridge) and bridge D (an integrated chest wall alternating bridge), the displacement decreased as the wall depth increased at both +30 and -30℃ due to pile resistance. As for the comparison between the analysis programs used, the relative error in Case 1 was small, whereas a significant difference in Case 2 was observed. The foregoing variation is possibly due to the difference in the application of the nonlinear spring in the programs.

• Journal of Life Science
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• v.20 no.4
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• pp.543-548
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• 2010

The purpose of this study was to examine the differences in kinetics between 6 months of rehabilitation training and 12 months of rehabilitation training after total hip arthroplasty. 10 unilateral THA participants performed kinetic tests. Three dimensional kinematics and hip flexors and abductors electromyography (EMG) were collected during each trial. T-test was used for statistical analysis (p<0.05). There was no significant difference in EMG data between the two groups, but the mean comparison EMG data was higher in the 12 months rehabilitation training group than the 6 months rehabilitation training group. The moment value was found with motion-dependent interaction analyzing method which was used by Feltner and Dapena. There was no significant difference between moment values of the two groups. There was no significant difference between ground reaction forces of the two groups; however, there were some differences shown in Fz (vertical reaction force) between the two groups ($892{\pm}104\;N$, $820{\pm}87\;N$). The first peak impact force was about 9% lower in the 12 months group compared to the 6 months group. The second peak active force was nearly equal between the two groups. More research is necessary to determine exactly what constitutes optimal rehabilitation training biomechanics for patients with total hip arthroplasty.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.457-466
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• 2009

This study puts the purpose in providing the scientific basis of dance motion as an artistic expression by analyzing the kinematic variable and the distribution factor of power affecting the motion, which is connected to the turn, right after the arabesque motion according to the existence and non existence of using the arm in the arabesque motion of modern dance. As a result of this study, arabesque turn motion, not using the upper limbs, used more turning force of head and body than the arabesque turn motion, using the upper limbs, and arabesque turn using the upper limbs obtained the turning force, using the right shoulder. The range of the hip joint on the left and the position change of left tiptoe in the Arabesque turn motion using the upper limbs is largely ascended to the vertical axis, while, the position of tiptoe in the Arabesque turn motion, not using the upper limbs is dropped to the lower part of each event. In the replacement of body center, Arabesque turn motion using the upper limbs is moved more to the turning axis than arabesque turn motion not using the upper limbs. As a result of maximum vertical ground reaction force, Arabesque turn motion using the upper limbs appeared to be a lower value than the Arabesque turn motion not using the upper limbs.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06a
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• pp.65-81
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• 2003

During the last few decades in Korea, the development of hillside or mountain areas has rapidly increased for infrastructure construction such as railroads, highways and housing. Many landslides have occurred during these constructions. Also, the amount and scale of damage caused by landslides have increased every year. In the case of Far East Asia including Korea, the damage of landslides is consequently reported during the wet season. In this paper, the effect of stabilizing piles on slope stability is checked and the behavior of slope soil and piles are observed throughout the year by field measurements in the large-scale cut slopes. In particular a large-scale cut slope situated on the construction site for the express highway in Donghae, Korea. First of all, The behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil gradually increased and rapidly decreased at depth of sliding surface indicating that the depth of sliding surface below the ground surface can be predicted. On the basis of being able to predict the depth of the sliding surface, stabilizing piles were designed and constructed in this slope. To ensure the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. The maximum deflection of piles is measured at the pile head and it is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.29-37
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• 2015

Objective : The purpose of this study was to investigate the biomechanical properties of shock absorption strategy and postural stability during the drop landing for each types. Methods : The motions were captured with Vicon Motion Capture System, with the fourteen infra-red cameras (100Hz) and synchronized with GRF(ground reaction force) data(1000Hz). Ten male soccer players performed a drop landing with single-leg and bi-legs on the 30cm height box. Dependent variables were the CoM trajectory and the Joint Moment. Statistical computations were performed using the paired t-test and ANOVA with Turkey HSD as post-hoc. Results : The dominant leg was confirmed to show a significant difference between the left leg and right leg as the inverted pendulum model during Drop Landing(Phase 1 & Phase 2). One-leg drop landing type had the higher CoM displacement, the peak of joint moment with the shock absorption than Bi-leg landing type. As a lower extremity joint kinetics analysis, the knee joint showed a function of shock absorption in the anterior-posterior, and the hip joint showed a function of the stability and shock absorption in the medial-lateral directions. Conclusion : These findings indicate that the instant equilibrium of posture balance(phase 1) was assessed by the passive phase as Class 1 leverage on the effect of the stability of shock absorption(phase 2) assessed by the active phase on the effect of Class 2 leverage. Application : This study shows that the cause of musculo-skeletal injuries estimated to be focused on the passive phase of landing and this findings could help the prevention of lower damage from loads involving landing related to the game of sports.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.187-194
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• 2007

The purpose of this study is to determine the characteristics of ground reaction force(GRF) in golf swing for various slopes of flat lie and uphill lies of 5 and 10 degrees. Five right-handed professional golfers were selected for the experiment and the 7 iron club was used. We used four forceplates to measure GRF and synchronized with the three-dimensional motion analysis system. Results showed that slope did not affect the total time for golf swing, but the time until the impact had a tendency to slightly increase for the uphill lie(p<0.05). The medial-lateral GRF of the right foot increased toward the medial direction during back swing, but less increases were found with the angle of uphill lie(p<0.05). The GRF of the left foot increased rapidly toward the medial direction at the uncocking and the impact during down swing, but decreased with the increase in the angle of uphill lie(p<0.05). The anterior-posterior GRF of both feet showed almost the same for different slopes. With the slopes, the vertical GRF of the right foot increased, but the vertical GRF of left foot decreased(p<0.05). Uphill lies would have negative effect to provide the angular momentum during back swing, restricting pelvic and trunk rotations, and to provide the precise timing and strong power during down swing, limiting movements of body's center of mass. The present study could provide valuable information to quantitatively analyze the dynamics of golf swing. Further study would be required to understand detailed mechanism in golf swing under different conditions.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.301-309
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• 2018

The aim of this study was to investigate the relationship between the neurocognitive ability and the risk factors of non-contact anterior cruciate ligament injuries during landing in female recreational athletes. Thirty-two female athletes participated in computerized neurocognition test and motion analysis for drop vertical jump. Pearson's linear correlation analysis was performed to analyze the relationship between the raw scores of neurocognition test and biomechanical variables including 3D joint angle, moment, power, vertical ground reaction force, loading rate, and support time. There were correlations between the scores of neurocognition test and biomechanical variables as high the neurocognition score, it also increase landing strategies were used to maintain posture of the lower extremity. Therefore, the neurocognitive test might be used as a good screening method to detect the risk factors before injury.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.285-293
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• 2012

The aim of this study is to identify the appropriate movement for maintaining postural balance during Front Kick and Turning Side Kick motions. To do so, ten Taekwondo athletes: five skilled players(S, body mass: $65.0{\pm}5.8kg$, height: $172.3{\pm}3.7cm$, age: $20.0{\pm}1.2yrs$, career: $9.0{\pm}1.9yrs$) and five less-skilled players(LS, body mass: $67.1{\pm}5.5kg$, height: $173.2{\pm}5.1cm$, age: $19.4{\pm}1.7yrs$, career: $9.6{\pm}1.7yrs$) participated in this study. A three-dimensional motion analysis was performed on the participants using eight infrared cameras and two force plate(sampling frequency of 200 Hz and 2000 Hz for S and LS players, respectively). The participants' motions were divided into: a front-kick phase(P1) and a turning-side-kick phase(P2). For P2(p<.05), the range and root mean square(RMS) of the ground reaction torque and the M-L mean velocity of COP were greater for LS than for S; similarly, for P2(p<.05), the M-L range, A-P range, and velocity of the COP were greater for LS than for S. Further, the M-L range and maximum velocity of the COP was greater for failure than for success(p<.05). The femoral biceps muscle for bending the knee joint was significantly stronger in S than in LS(p<.05). It is expected that these results will be useful in developing a training program for improving the balance and stability of Taekwondo poomsae athletes and improve their front-kick and turning-side-kick motions.