• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.29-44
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• 2005

The purpose of this study is to reveal the effects of two different kicks, the drop kick and the punt kick, into the kicking motion, through the kinetic comparative analysis of the kicking motion, which is conducted when one kicks a soccer goal. To grasp kinetic changing factors, which is performed by individual's each body segment, I connected kicking motions, which were analyzed by a two dimension co-ordination, into the personal computer to concrete the digits of it and smoothed by 10Hz. Using the smoothed data, I found a needed kinematical data by inputting an analytical program into the computer. The result of comparative analysis of two kicking motions can be summarized as below. 1. There was not a big difference between the time of the loading phase and the time of the swing phase, which can affect the exact impact and the angle of balls aviation direction. 2. The two kicks were not affected the timing and the velocity of the kicking leg's segment. 3. In the goal kick motion, the maximum velocity timing of the kicking leg's lower segment showed the following orders: the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.018sec) in the drop kick, and the thigh(-0.06sec), the lower leg(-0.05sec), the foot(-0.015sec) in the punt kick. It showed that whipping motion increases the velocity of the foot at the time of impact. 4. At the time of impact, there was not a significant difference in the supporting leg's knee and ankle. When one does the punt kick, the subject spreads out his hip joint more at the time of impact. 5. When the impact performed, kicking leg's every segment was similar. Because the height of the ball is higher in the punt kick than in the drop kick, the subject has to stretch the knees more when he kicks a ball, so there is a significant affect on the angle and the distance of the ball's flying. 6. When one performs the drop kick, the stride is 0.02m shorter than the punt kick, and the ratio of height of the drop kick is 0.05 smaller than the punt kick. This difference greatly affects the center of the ball, the supporting leg's location, and the location of the center of gravity with the center of the ball at the time of impact. 7. Right before the moment of the impact, the center of gravity was located from the center of the ball, the height of the drop kick was 0.67m ratio of height was 0.37, and the height of the punt kick was 0.65m ratio of height was 0.36. The drop kick was located more to the back 0.21m ratio of height was 0.12, the punt kick was located more to the back 0.28m ratio of height was 0.16. 8. There was not a significant difference in the absolute angle of incidence and the maximum distance, but the absolute velocity of incidence showed a significant difference. This difference is caused from that whether players have the time to perform of not; the drop kick is used when the players have time to perform, and punt kick is used when the players launch a shifting attack. 9. The surface reaction force of the supporting leg had some relation with the approaching angle. Vertical reaction force (Fz) showed some differences in the two movements(p<0.05). The maximum force of the right and left surface reaction force (Fx) didn't have much differences (p<0.05), but it showed the tendency that the maximum force occurs before the peak force of the front and back surface (Fy) occurs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.678-686
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• 1999

The purpose of this work is to Investigate the pressure drop and the heat transfer characteristics in the channel of plate heat exchanger with crossed-discrete ribs. The flow is assumed to be three-dimensional, laminar and periodically fully developed. Computations have been carried out for angles of attack from $0^{\circ}$ to $90^{\circ}$ and ratios of rib height from 0.15 to 0.46 for various values of Reynolds and Prandtl numbers. The heat transfer was improved by inclined ribs generating helical vortices and secondary flows. The results show that the pressure drop has a maximum value at $70^{\circ}$ and the heat transfer has a maximum value at $45^{\circ}$. As the rib height increases, the pressure drop and the heat transfer increase quadratically, and the increasing rate of pressure drop is higher than that of the heat transfer. As Reynolds number increases, the pressure drop increases in proportion to the square of Reynolds number and the heat transfer increases linearly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.873-881
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• 2006

The present study investigates the pressure drop characteristics in rotating two-pass ducts. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter $(D_h)$ of 26.67mm. Rib turbulators are attached crossly in the four different arrangements on the leading and trailing surfaces of the test ducts. The ribs have a rectangular cross section of $2mm(e){\times}3mm(w)$ and an attack angle of $70^{\circ}C$. The pitch-to-rib height ratio (pie) is 7.5, and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.075. The results show that the highest pressure drop among each region appears in the turning region for the stationary case, but appears in the upstream region of the second pass for the rotating case. Effects of cross rib arrangements are almost the same in the first pass for the stationary and rotating cases. In the second pass, however, heat transfer and pressure drop are high for the cases with cross NN or PP type ribs in the stationary ducts. In the rotating ducts, they are high for the cases with cross NP or PP type ribs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.882-890
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• 2006

The present study investigates the pressure drop characteristics in rotating two-pass ducts. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter $(D_h)$ of 26.67mm. Rib turbulators are attached parallel in the four different arrangements on the leading and trailing surfaces of the test ducts. The ribs have a rectangular cross section of $2m(e){\times}3mm(w)$ and an attack angle of $70^{\circ}C$. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.075. The results show that the highest pressure drop among each region appears in the turning region for the stationary case, but appears in the upstream region of the second pass for the rotating case. Effects of parallel rib arrangements are almost the same in the first pass for the stationary and rotating cases. In the second pass, however, heat transfer and pressure drop are high for the cases with parallel NN or PP type ribs in the stationary ducts. In the rotating ducts, they are high for the cases with parallel NN or PN type ribs.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.315-324
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• 2012

The purpose of current study was to investigate the effects of the heights on the lower extremities, torso and neck segments for energy dissipation during single-leg drop landing from different heights. Twenty eight young healthy male subjects(age: $23.21{\pm}1.66yr$, height: $176.03{\pm}4.22cm$, weight: $68.93{\pm}5.36kg$) were participated in this study. The subjects performed the single-leg drop landing from the various height(30, 45 & 60 cm). Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. The results were as follows. First, the ROM at the ankle, knee, hip and trunk was increased with the increased heights but the ROM at the neck was increased in the 60cm. Second, the angular velocity, moment and eccentric work at the ankle, knee, hip, trunk, and neck was increased with the increased heights. Third, the contribution to total work at the knee joint was not significantly different, while the ankle joint rate was decreased and hip and neck rate was increased in the 60cm, and trunk rate was increased with the increased heights. Lastly, the increase in landing height was able to augment the level of energy dissipation not only at the lower extremities but also at the trunk and neck. The findings showed that drop landing affect trunk and neck with lower extremity joints. Therefore, we need to consider that trunk and neck strengthening including stability should be added to reduce sports injury during prevention training.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.3_4
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• pp.377-386
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• 2004

This report is the second study to develop the standard tables of body measurements to be used for improving the fit of garments and patterns for women aged 60 and older. The purpose of this study is to suggest the new sizing system proper to the women aged 60 and older by classifying their somatotype and developing the standard tables of body measurements for each somatotype. The data are the anthropometric measurements of 329 women aged 60 and older measured in 2001 and the 1997 National Somatometry Survey data. The major contents of this study are as follows. The applicability of KS K 0051 and ISO 3637 sizing systems to the women aged 60 and older was investigated by analyzing the distribution of height and drop index the difference of hipgirth and bustgirth. In this result, we certified the two sizing systems were not so proper to elderly women and the new sizing system proper to them was required. So, we classified the somatotype of the women aged 60 and older to 3 groups, 135cm$\leq$H(height)＜145cm, 145cm$\leq$H＜155cm, 155cm$\leq$H＜165cm by height and classified to 3 groups, -4cm$\leq$D(drop)＜16cm, -4cm$\leq$D＜4cm, -l6cm$\leq$D＜-4cm by drop index, and we suggested more proper sizing system for women aged 60 and older by compounding height and drop groups. We also developed the standard tables of body measurements every bustgirth groups of 9 somatotypes. We expect the standard tables of body measurements to applicate to manufacture clothing for elderly women.

• PNF and Movement
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• v.19 no.2
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• pp.279-285
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• 2021

Purpose: This study aimed to develop new digital navicular drop test (ND-NDT) equipment and to determine its validity and reliability. Methods: A total of 24 healthy male and female adults, who fully understood the purpose of the study and gave consent to participate in the study, were selected as participants. The NDT and ND-NDT were conducted in the dominant foot of the participants in a random order. For the NDT, the position of the navicular bone was marked with a pen first; then, the height of the navicular bone from the ground was measured in both sitting and standing positions. For the ND-NDT, after the sticker-type reflection markers were attached to the position of the navicular bone, the height of the navicular bone from the ground was measured in both sitting and standing positions. To assess the validity of the diagnostic tests, the same examiner measured the height of the medial longitudinal arch (MLA) three times in both the sitting and standing positions. To assess the inter-rater reliability of the ND-NDT, three examiners, in a random order, attached the sticker-type reflection markers to the position of the navicular bone and then measured the height of the MLA in both positions. Results: In the sitting position, the Pearson correlation coefficient (r) between the two diagnostic tests was very high (r = 0.97) and statistically significant. In the standing position, the Pearson correlation coefficient (r) between the two tests was 0.95, which was also statistically significant. The ICC_2,1 values in the sitting and standing positions were 0.93 and 0.95, respectively, indicating significantly high inter-rater reliability. Conclusion: The ND-NDT equipment showed very high diagnostic validity, as well as excellent inter-rater reliability, indicating the clinical usefulness of the equipment as a diagnostic system for confirming pes planus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.505-513
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• 2006

The pressure drop characteristics in a rotating two-pass duct with rib turbulators are investigated in the present study. Three ducts of different aspect ratios (W/H=0.5, 1.0 and 2.0) are employed with a fixed hydraulic diameter ($D_h$) of 26.7 mm. $90^{\circ}$-rib turbulators with $1.5mm{\times}1.5mm$ cross-section are attached on the leading and trailing surfaces. The pitch-to-rib height ratio (p/e) is 1.0. The distance between the tip of the divider and the outer wall of the duct is 1.0 W. The thickness of divider wall is 6.0 mm o. 0.225 $D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000 and the .elation number (Ro) is varied from 0.0 to 0.2. As duct aspect ratio increases, high friction factor ratios show in overall regions. The reason is that the rib height-to-duct height ratio (e/H) increases, but the divider wall thickness-to-duct width ($t_d/W$) decreases. The rotation of duct produces pressure drop discrepancy between the leading and trailing surfaces. However, the pressure drop discrepancy of the high duct aspect ratio (AR=2.0) is smaller than that of the low duct aspect ratio (AR=0.5) due to the decrement of duct hight (H).

• Journal of Biosystems Engineering
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• v.41 no.3
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• pp.221-231
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• 2016

Purpose: The objective of this study was to develop cushion curves models and analyze the cushioning performance of multi-layered corrugated structures (MLCS) using a method based on dynamic stress-energy relationship. Methods: Cushion tests were performed for developing cushion curve models under 12 combinations of test conditions: three different combinations of drop height, material thickness, and static stress for each of four levels of energy densities between 15 and $60kJ/m^3$. Results: Dynamic stress and energy density for MLCS followed an exponential relationship. Cushion curve models were developed as a function of drop height, material thickness, and static stress for different paperboards and flute types. Generally, the differences between the shock pulse (transmitted peak acceleration) and cushion curve (position and width of belly portion) for the first drop and the averaged second to fifth drop were greater than those for polymer-based cushioning materials. Accordingly, the loss of cushioning performance of MLCS was estimated to be greater than that of polymer-based cushioning materials with the increasing number of drops. The position of the belly of the cushion curve of MLCS tends to shift upward to the left with increasing drop height, and the belly portion became narrower. However, depending on material thickness, under identical conditions, the cushion curve of MLCS showed an opposite tendency. Conclusions: The results of this study can be useful for environment-friendly and optimal packaging design as shock and vibrations are the key factors in cushioning packaging design.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.360-368
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• 2010

The paper presents a case study from a surface mine where the controlled augmentation of throw and drop of the blasted muck piles was warranted to spread the muck piles on the lower berm of the bench. While the augmentation of throw increased the lateral spread and the looseness of the broken muck, the augmentation of drop significantly lowered the muck pile height for easy excavation by the excavators. In this light, the present paper highlights and discusses some pertinent changes in the blast design parameters for such specialized application of cast blasting in a surface mine, where a sandstone bench, with average height of 22-24 m was to be made amenable for excavation by 10 m3 rope shovels, which possessed maximum digging capability of up to 14 m. The results of tailoring the blast design parameters for augmentation of throw and drop are compared with the baseline blasts which were earlier practiced on the same bench by dividing the full height of the bench in 2-slices; upper slice (10-14 m high) and lower slice (12-15 m high). Results of fragment size, its distribution and total cycle time of excavator (shovel) are presented, and discussed.