• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.1-7
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• 2005

Incompressible Reynolds-averaged Navier-Stokes equations with $\varepsilon{-SST}$ turbulence model are adopted for the investigation of the flow fields between the square cylinder and the ground. When the grounds moves, the diminish of the shear layer intensity on the ground promotes the interaction between the lower and the upper separated shear layer of the cylinder. Hence vortex shedding occurs at the lower gap height than stationary ground. In the moving ground, the secondary shedding frequency disappears due to the absence of the separation bubble on the ground which exists in the stationary ground. In addition, the shedding frequency and aerodynamic coefficients in the moving ground become higher than those of the stationary ground.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.9
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• pp.1383-1389
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• 2013

This research was conducted to see the correlation between changes of ankle Joint Position Sense and Sway Area through Unstable Surface training. For the study, 48 healthy males and females were randomly divided into an unstable surface group(n=24) and a stable surface group(n=24). Then, they were asked to carry out the same exercise program three times a week for six weeks. The unstable surface group and stable surface group performed the exercise program on the balance exercise pad and on the hard ground, respectively. As a result, the unstable surface group displayed significantly reduced error of ankle joint position sense and sway area(p<.05). Moreover, a significant correlation between variances of ankle joint position sense and sway area was only found in the unstable surface group. In conclusion, this study demonstrated that there was a significant correlation between changes of ankle joint position sense and sway area through proprioceptive sense training on the unstable surface.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.49-57
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• 2008

The purpose of this study was to determine the effects of 12-week elastic resistance exercise for the elderly on the magnitude of frequency and variability of ground reaction force signals. To this aim, total 12 elderly women aged in their 70 were participated in this study and asked to do a 12-week elastic resistance exercise program. FFT(fast Fourier Transform) was used to analyze the frequency domain analysis of the ground reaction forces's signals and an accumulative PSD (power spectrum density) normalized by support phase of walking was calculated to reconstruct the certain signals. To estimate the gait stability between the before and after exercise, values of variability were determined in a coefficient of variance. The magnitude of frequency and variability analysis for media-lateral signal revealed significantly less after exercise (p<.05). In contrast, variability of this signal's frequency that have used to evaluate the local stability during walking exhibited significantly greater after exercise(p<.05). In summary, magnitude frequency and variability of media-lateral ground reaction force's signal were significantly changed after a 12-week elastic resistance exercise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4598-4603
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• 2012

The purpose of this study is to compare and evaluate the balance and muscle activity after having performed balance exercise at different ground conditions. The subjects were divided into 3 groups; Sand Group(SG)(N=30) and Balance Form group(BFG)(N=30), Hard Ground Group(HGG)(N=30). The period of intervention was for six weeks. EMG for Tibialis anterior(TA), Soleus(So), Biceps femoris(BF) muscle activity, Air-balance system 3D were used as evaluation tools for this study. the change of balance ability and TA, So muscle activity was greater in the SG, BFG than HGG which may imply that sand can be used for the balance exercise like any other ground.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.431-437
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• 2010

The purpose of this study is to compute the ground reaction forces during gait in the absence of force plates. The difficulties in using force plates for hemiparetic patients inspired us to initiate this study. Level-walking experiments were performed using a three-dimensional motion analysis system with synchronized force plates. Kinematic data were obtained from the three-dimensional trajectories of reflective markers. Gait events were also detected from the kinematic data. The human body was modeled as 13 rigid segments. The mass and the center of mass of each segment were determined from anthropometric data. Vertical ground-reaction forces obtained from the kinematic data were in good agreement with those obtained using the force plate. The computed and measured values of anterior and lateral ground reaction showed similar tendencies. The computation results can be used as the basic data for inverse dynamic analysis.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.355-366
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• 2003

본 연구의 목적은 뛰어 내리기 동작 시 신발과 뛰어 내리는 높이가 지면반력과 충격감소에 미치는 영향을 연구하였다. 10명의 건강한 피험자가 신발 또는 맨발로 네 가지 다른 높이에서 (30, 45, 60 &75 cm) 다섯 번의 뛰어 내리기를 시도하였다. 수직지면반력(VGRF), 영상분석, 경골과 앞이마의 가속도가 함께 측정되었다. 첫 번째 정점의 수직지면반력 (VGRF1)은 75cm의 높이에서 맨발보다는 신발을 신은 상황에서 더 큰 값을 보여 주었다. 두 번째 정점의 수직지면반력 (VGRF2)은 신발을 신은 것보다는 맨발의 조건에 더 큰 값을 보여 주었다. 앞 이마의 가속도 (AccHead)는 높이와 지면에 거의 변화를 보이지 않았다. 첫 번째 정점의 경골 가속도 (AccHead)는 높이와 지면에 거의 변화를 보이지 않았다. 첫 번째 정점의 경골 가속도 (AccTibia1)는 맨발의 조건보다 신발을 신은 조건에서 더 크게 나타났다. 반면에 두 번째 정점의 경골 가속도 (AccTibia2)는 특히 60 그리고 75cm조건에서 신발을 신었을 때 보다 맨발일 때 더 큰 값을 보여 주었다. 충격감소지수 (AtteIndex)는 모든 높이에서 맨발의 조건이 신발을 신은 조건 보다 통계적으로 유의하게 높게 나타났다. 결론적으로 뛰어 내리기 동작 시 신발이 지면반력을 최소화시키고 충격을 감소시키는데 부가적인 완충물로 제공되었음을 뒷받침 해준다.

• Advanced Industrial SCIence
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• v.3 no.2
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• pp.23-30
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• 2024

This study aimed to examine the changes in dynamic balance exercises after performing lunge exercises on unstable surfaces and on the ground. Participants were divided into a BOSU training group, a balance pad training group, and a ground training group, and performed lunge exercises. As a result, the functional reach test significantly increased in both the BOSU training group and the ground training group, while the Y-balance test significantly increased only in the balance pad training group. No significant differences were found between the groups. Through this study, it was confirmed that although differences between lunge exercises on the ground and on unstable surfaces were not identified, lunge exercises do influence balance ability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.8-14
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• 2005

Understanding of the flow past a bluff body close to a moving ground is very important in automobile and aeronautical fields because of aerodynamic characteristic and instability induced by unsteady vortex shedding. The passive control method that mounted the vertical and horizontal plates at the lower surface of the cylinder is studied to suppress the unsteady oscillation motion. When the grounds moves, the diminish of the shear layer on the ground promotes the interaction between the lower and the upper separated shear layers of the cylinder, hence vortex shedding occurs at the lower gap height than the stationary ground.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.129-135
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• 2008

This research was examined the effect of Backward Walk on ground reaction force and we achieved it by using ground reaction force machine during the Backward Walk activity with Latin and Rumba dance. We find that it was significant difference of vertical(Fz) ground reaction force of right foot in touchdown and toe-off and vertical(Fz), horizontal(Fx), front-rear(Fy) ground reaction force of left foot. There was not significant differences in vertical ground reaction force between superior athlete and unskilled athlete, but there was a significant difference in left foot. Through this, we know that the sports capability of left foot which has been developed through the training is better in superior athlete group. Therefore understanding of difference in ground reaction force and repeated training can help the unskilled athlete and beginner to accomplish the accurate movement.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.449-455
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• 2009

The purpose of this study was to analyze the kinetics variables of GRF by dtance type during forehand stroke. Eight high school tennis players, who have never been injured for last six months, in Busan were chosen for the study. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, semi-open and open stance. It was filmed by 6 video camera and used with 3-dimensional motion analyzer system and GRF system. The following kinetic variables were analyzed in relation to left leg and right leg GRF. The conclusion were as follow: 1. In square and semi-open stances, the horizontal ground reaction force was decreased at impact in left leg regardless of swing type, whereas open stance was increased at impact to the tiptoe in both legs. 2. In square and semi-open stances, the vertical ground reaction force was increased at impact in left leg regardless of swing types, whereas open stance was decreased at impact to vertical direction in both legs.