• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.31-39
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• 2005

The Purpose of this study was to reveal the biomechanical difference of two soccer footwear(soft ground footwear and hard ground footwear). Secondly, the purpose of this study was to clarify how each type of soccer footwear effects soccer players, which will provide scientific data to coaches and players, to further prevent injuries and to improve each players capacity. The result of comparative analysis of two soccer footwear can be summarized as below. The comparison of the very first braking force at walking found distinctive factors in the statistical data(t=3.092, p<.05). Braking impulse of two difference footwear showed distinctive factors in the statistical data(t=2.542, p<.05). In comparing GRFz max(N), the result showed a statistically significant difference in the two soccer footwear at running(t=2.784, p<.05). In the maximum braking impulse(t=2.774, p<.05) and propulsive impulse for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. In the maximum braking force(t=3.270, p<.05) and propulsive force(t=4.956, p<.05) for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. Significant differences were not found in moment(rotational friction) with two difference soccer footwear(moment max; t=2.231, moment min; t=1.784).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.506-512
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• 2004

We analytically estimated the propulsive performance of pulse detonation engines (PDEs) in three cases, which were (1) a fully-fueled simplified PDE, (2) a partially-fueled simplified PDE, and (3) a PDE optimized as a system. The results of the model analyses in the cases of (1) and (2) were in good agreement with published experimental data which were obtained by using simplified PDEs. The comparison between the results of the analyses of simplified PDEs and those of optimized PDE systems showed that specific impulse would become higher by about 10-20% due to PDE-system optimization.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.27-36
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• 2007

The purpose of this study was to investigate the effect of the upper body in order to increase a propulsive force in the old's walking. The subjects were each 10 males, the latter term of the aged and former term of the aged. There were three walking speeds of slow(about 5km/h), medium(about 6km/h), and maximum speed(about 7km/h). The subjects walking 11m were filmed the 5m section (from 3m to 8m) by 2-video cameras using three dimensional cinematography. And we computed different mechanical quantities and especially computed the relative momentum in order to achieve this study's aim. In this study, we was able to acquire some knowledge. The step length and step frequency increased in proportion to the walking speed, and the faster walking speed, the shorter ratio of supporting time( both legs supporting time/one step length time). When it was one leg support phase, the torso was indicated to generate the momentum in order to produce the propulsive force of walking. The upper and lower body had a cooperative relation for walking such as keeping step rate with the arms to legs and maintaining the body balance. The opposition phase for upward-and-downward direction of the torso and arms in walking was functioned to prevent the increase rapidly toward vertical direction of the center of gravity. The arms had contributed to coordinate the tempo of legs and the posture maintenance of the upper body. And by absorbing the relative momentum from the upper torso with arms to the lower torso, it had the rhythmical movement on upward-and-downward direction reducing the vertical reaction force. On account of the relations of absorption and generation of the propulsive force and the production of vertical impulse in the lower torso when walking by maximum speed, it was showed that the function of lower torso was come up as important problem for the mechanical posture stability and propulsive force coordination.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.105-119
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• 2004

To enhance our understanding of the loads on the foot during treadmill running, we have used a pressure-sensitive insole system to determine pressure, rate of loading and impulse distributions on the plantar surface during treadmill running, both in minimally cushioned footwear and in cushioned shoes. This report includes pressure, rate of loading, impulse and contact time data from a study of ten subjects running on a treadmill at 4.0m/s. Among heel-toe runners, the highest peak pressures and highest rates of loading were observed under the centre of the heel and in the medial forefoot. The arch regions were only lightly loaded. Contact time was greater in the forefoot than in the heel. Two-thirds of the impulse recorded during the step was the result of forces applied through the forefoot, mostly in the region of the metatarsal heads. The distribution of loads in the shoe suggests that the load distributing properties of the cushioning system are most important in the centre of the heel, under the metatarsal heads and great toe. Shock attenuation is primarily required under the centre of the heel and to lesser extent under the metatarsal heads. Some energy dissipation may be desirable in the heel region because it causes shock to be absorbed with less force. All the 'propulsive' effort is applied through the forefoot. Therefore, this region should as resilient as possible.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.325-326
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• 2004

Experiment of laser propulsion in free flight has never been conducted. At Institute of Fluid Science (IFS), Tohoku University, propulsive impulse generation by focusing on a rest projectile was demonstrated. Based on the ideas obtained from this experiment, experiment of laser propulsion of a projectile in flight by focusing $CO_2$ laser beam is being prepared for. The objective velocity increment in experiment is about 50 m/s.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.539-547
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• 2009

The purpose of this study was to investigate the changes of kinetic and kinematic parameters in obstacle gaits after 12 weeks of an aquatic exercise program. Eight female elders walked in four different heights of obstacles(0, 2.5, 5.1, & 15.2cm) on their self-selected speed. The ROM of hip was significantly increased after the aquatic exercise program. Swing and Stance duration were decreased. The step length was significantly increased and the step width was decreased. After the exercise program the clearance between the right foot and the top of obstacle(except 15.2cm) increased and the crossing speed was increased. The braking force, propulsive force, braking impulse, and propulsive impulse were significantly changed after the aquatic exercise program. The 12 weeks of the aquatic exercise program resulted in lower body strength and balance gains in female elders. The improvements were associated with changes in kinetic and kinematic parameters leading to an obstacle-crossing speed and a safer lower-limb control. The aquatic exercise program is suggested as an effective intervention to promote gait ability and prevent fall-related to the injuries.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.75-83
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• 2006

The Purpose of this study was to compare the biomechanical difference of two soccer footwear. which will provide scientific data to coaches and players, to further prevent injuries and to improve each players skills. The result of this study can be summarized after testing the two types of soccer footwear with comparative transforming heel angles and also with a pressure distribution in running. When a player's foot first touched the ground, the average difference of in/eversion was between 1.2 and 3.1 degrees for the two soccer shoes. In regards to maximum inversion and eversion of foot, maximum tibial rotation, and maximum and total movement of foot, the condition of barefoot and the two soccer shoes showed a small difference from 1.5 to 3.5 degrees and the difference among the subjects of study wasn't constant. In regards to maximum velocity of inversion and eversion running in one's bare feet showed much lower inversion velocity in comparison to putting on two types of soccer shoes and comparison of the average. Among some of the subjects, after putting on the two types of soccer shoes exceeded $97^{\circ}/s$ in maximum velocity of eversion. In the maximum braking impulse(t=2774, p<.05) and propulsive impulse for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running. In the maximum braking force(t=3.270, p<.05) and propulsive force(t=4.956, p<.05) for antero-posterior direction, there was a statistically significant difference between the two soccer footwear at running.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.101-108
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• 2018

Objective: The aim of this study was to investigate gender differences in ground reaction force (GRF) components among different speeds of running. Method: Twenty men ($age=22.4{\pm}1.6years$, $mass=73.4{\pm}8.4kg$, $height=176.2{\pm}5.6cm$) and twenty women ($age=20.7{\pm}1.2years$, $mass=55.0{\pm}8.2kg$, $height=163.9{\pm}5.3cm$) participated in this study. All participants were asked to run on an instrumented dual belt treadmill (Bertec, USA) at 8, 12, and 16 km/h for 3 min, after warming up. GRF data were collected from 30 strides while they were running. Hypotheses were tested using one-way ANOVA, and level of significance was set at p-value <.05. Results: The time to passive peaks was significantly earlier in women than in men at three different running speeds (p<.05). Further, the impact loading rates were significantly greater in women than in men at three different running speeds (p<.05). Moreover, the propulsive peak at 8 km/h, which is the slowest running speed, was significantly greater in women than in men (p<.05), and the vertical impulse at 16 km/h, which is the fastest running speed, was significantly greater in men than in women (p<.05). The absolute anteroposterior impulse at 8 km/h was significantly greater in women than in men (p<.05). In addition, as the running speed increased, impact peak, active peak, impact loading rate, breaking peak, propulsive peak, and anteroposterior impulse were significantly increased, but vertical impulse was significantly decreased (p<.05). Conclusion: The impact loading rate is greater in women than in men regardless of different running speeds. Therefore, female runners might be exposed to the risk of potential injuries related to the bone and ligament. Moreover, increased running speeds could lead to higher possibility of running injuries.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.34-37
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• 2009

The present study presents a numerical methodology for early conceptual trade-off study between propulsive performance, cooling efficiency, weight and size, in which combustion and cooling precesses in regeneratively cooled rocket thrust chamber are interactively simulated. To address the capabilities and reliability of the design tool, some application results are given involving contour design, performance analysis, and wall cooling prediction as well as a systematic design evaluation.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.67-82
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• 2004

The purpose of this study was to evaluate the function and the safety of an additional weight shoe developed for the improvement of aerobic capacity, and to improve some problems found by subject's test for an additional weight shoe. The subjects employed for this study were 10 college students. 4 video cameras, AMTI force platform and Pedar insole pressure distribution measurement device were used to analyze foot motions. The results of the study were as follows: 1 The initial achilles tendon angle and initial rearfoot pronation angle of an additional weight shoe during walking were 183.7 deg and 2.33 deg, respectively, and smaller than a barefoot condition. Maximum achilles tendon angle and the angular displacement of achilles tendon angle were 185.35 deg and 4.21 deg respectively, and smaller than barefoot condition. Thus rearfoot stability variables were within the permission value for safety. 2. Maximal anterior posterior ground reaction force of additional weight shoe was appeared to be 1.01-1.2 B.W., and was bigger than a barefoot condition. The time to MAPGRF of an additional weight shoe was longer than a barefoot condition. Maximal vertical ground reaction force of additional weight shoe was appeared to be 2.3-2.7 B.W., and was bigger than a barefoot condition in propulsive force region. But A barefoot condition was bigger in braking force region. The time to MVGRF of an additional weight shoe was longer than a barefoot condition. 3. Regional peak pressure was bigger in medial region than in lateral region in contrast to conventional running shoes. The instant of regional peak pressure was M1-M2-M7-M4-M6-M5 -M3, and differed form conventional running shoes. Regional Impulse was shown to be abnormal patterns. There were no evidences that an additional weight shoe would have function and safety problems through the analysis of rearfoot control and ground reaction force during walking. However, There appeared to have small problem in pressure distribution. It was considered that it would be possible to redesign the inner geometry. This study could not find out safety on human body and exercise effects because of short term research period. Therefore long term study on subject's test would be necessary in the future study.