• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.136-150
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• 2022

In this study, a comparative review was conducted on how to use RGB images to obtain river topographic information, which is one of the most essential data for eco-friendly river management and flood level analysis. In terms of the topographic information of river zone, to obtain the topographic information of flow section is one of the difficult topic, therefore, this study focused on estimating the river topographic information of flow section through RGB images. For this study, the river topography surveying was directly conducted using ADCP and RTK-GPS, and at the same time, and orthomosiac image were created using high-resolution images obtained by drone photography. And then, the existing developed regression equations were applied to the result of channel topography surveying by ADCP and the band values of the RGB images, and the channel bathymetry in the study area was estimated using the regression equation that showed the best predictability. In addition, CCHE2D flow modeling was simulated to perform comparative verification of the topographical informations. The modeling result with the image-based topographical information provided better water depth and current velocity simulation results, when it compared to the directly measured topographical information for which measurement of the sub-section was not performed. It is concluded that river topographic information could be obtained from RGB images, and if additional research was conducted, it could be used as a method of obtaining efficient river topographic information for river management.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.159-173
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• 1991

This paper describes a potential-based panel method formulated for the analysis of a super-cavitating two-dimensional hydrofoil. The method employs normal dipoles and sources distributed on the foil and cavity surfaces to represent the potential flow around the cavitating hydrofoil. The kinematic boundary condition on the wetted portion of the foil surface is satisfied by requiring that the total potential vanish in the fictitious inner flow region of the foil, and the dynamic boundary condition on the cavity surface is satisfied by requiring thats the potential vary linearly, i.e., the tangential velocity be constant. Green's theorem then results in a potential-based integral equation rather than the usual velocity-based formulation of Hess & Smith type. With the singularities distributed on the exact hydrofoil surface, the pressure distributions are predicted with improved accuracy compared to those of the linearized lilting surface theory, especially near the leading edge. The theory then predicts the cavity shape and cavitation number for an assumed cavity length. To improve the accuracy, the sources and dipoles on the cavity surface are moved to the newly computed cavity surface, where the boundary conditions are satisfied again. This iteration process is repeated until the results are converged. Characteristics of iteration and discretization of the present numerical method are much faster and more stable than the existing nonlinear theories. The theory shows good correlations with the existing theories and experimental results for the super-cavitating flow. In the region of small angles of attack, the present prediction shows and excellent comparison with the Geurst's linear theory. For the long cavity, the method recovers the trends of the Wu's nonlinear theory. In the intermediate regions of the short super-cavitation, the method compares very well with the experimental results of Parkin and also those of Silberman.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2012-2019
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• 2015

This study examined the changes in the center of pressure (COP) and cadence according to three types of bags carried and three different bag weights. The experimental period was from June 3, 2013 to January 20, 2014, and thirty eight healthy adults (mean age: $26.10{\pm}5.32$ years, age range: 22-30 years) volunteered under three conditions. In the first condition, the subjects wore a bag over one shoulder and they walked. In the second condition, they carried a bag across the shoulder and walked. With the third condition, they carried a backpack using both shoulders and walked. 3-Dimentional motion analysis system and a force plate were used to measure the kinematic parameters of gait and COP displacement during gait. Each subject walked 6 meters carrying a 3kg, 5kg and 7kg bag under all three conditions. The COP of the antero-posterior and medio-lateral, and cadence variable were significantly different according to the bag weight of 3kg, 5kg and 7kg. These findings suggest that walking while carrying a backpack using both shoulders is more effective on the changes in COP and gait of adults than the other conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3513-3520
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• 2012

This study aimed to investigate the difference of the body orientation ability in sitting position to adapt to dynamically changing angle of the base of support in stroke patients and Healthy adults. The angle between vertical and head and trunk in 12 stroke patients (6 male and 6 female) and 12 healthy adults (6 male and 6 female) were measured by video motion analysis system. The head and trunk angle between stroke patients and healthy adults in sitting position were significantly different when increase the angle of dominant side(p<.05). The head and trunk angle between stroke patients and healthy adults in sitting position were significantly different when increase the angle of non-dominant side(p<.05). The head and trunk angle between stroke patients and healthy adults in sitting position were significantly different when decrease the angle of non-dominant side(p<.05). The head angle between stroke patients and healthy adults in sitting position was significantly different(p<.05), but the trunk angle was not significantly different when decrease the angle of dominant side(p>.05), Stroke patients compared to healthy adults had more deficits in their body orientation ability in sitting position to adapt to dynamically changing angle of the base of support. This finding may help to understand postural control deficits more clearly in stroke patients in sitting position.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.235-257
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• 2004

The purpose of this study was to analyze the kinematical traits variables when performing Uchimata(inner thigh reaping throw) by Voluntary Resistance Levels(VRL) and two postures of Uke in Judo. The subjects, who were one male judoka(YH) for 1992 Barcelona Olympic Games, and one male trainee Y. I. University representative member(SDK) and were filmed on two S-VHS 16 mm video cameras(60fields/sec.), that posture of Uke were Shizenhontai(straight defensive posture) and Jigohontai(straight natural posture), VRL of Uke were 0% and 100%. The kinematical variables were temporal(total time-required: TR), potures and COG variables etc., The data of this study collection were digitized by SIMI Motion Program computed the mean values and the standard deviation calculated for each variables. When performing according to each posture and VRL, from the data analysis and discussion, the conclusions were as follows : 1. Temporal variables total time-required(TR) when performing Uchimata was shown the shortest time YH than SDK by each posture and VRL. TR of each posture were shown the shorten trends or equal in DP by lower than NP, In existence and / or nonexistence of VRL was shown the shorten trends in VRL 0% than 100% of Uke. 2. Posture variables : In attacking right knee angle, YH was performing flexion($147{\rightarrow}103degree$) from Tsukuri(set-up) to Kake(execution) in regardless of postures and VRLs, SDK was performing not exchange extension and flexion in VRL 100%, and extension($120{\rightarrow}142degree$) in VRL 0%, respectively. In supporting left hee angle, YH was performing extension($119{\rightarrow}163degree$) from Tsukuri(set-up) to Kake(at(execution) in regardless of postures and VRLs, SDK extension($93{\rightarrow}139degree$), respectively. In attacking right hip angle, from Tsukuri to Kake, YH was performing extension($133{\rightarrow}169degree$), except in VRL 0%($156{\rightarrow}137degree$) NP, SDK was performing flexion($159{\rightarrow}126degree$) accept in VRL 100%($149{\rightarrow}152degree$) NP, In left hip angle, from Tsukuri to Kake, YH was performing flexion NP(70, 50degree) more than DP(27, 57degree), SDK was performing flexion DP(73, 52degree) more than NP(34, 20degree). 3. COG variables : When performing Uchimata, vertical COG variables was shown YH(:$2{\sim}8cm$), SDK(:$15{\sim}24cm$) lower than Uke's COG level position, in existence and / or nonexistence of postures and VRL, during Kake as maximum force point of throwing techniques in Judo.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.4
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• pp.321-329
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• 2013

Despite the advantage of unlimited access, there are insufficient studies for the accuracy and stability of FKP that blocks the spread of the system for various applications. Therefore, we performed a long-term analysis from continuous real-time positioning, and investigated the error characteristics dependent on the size and the surrounding environment. The FKP shows significant changes in the positioning accuracy at different times of day, where the accuracy during daytime is worse than that of nighttime. In addition, the size and deviation of FKP correction may change with the ionospheric conditions, and high correlation between ambiguity resolution rate and the deviation of correction was observed. The receivers continuously request the correction information in order to cope with sudden variability of ionosphere. On the other hand, the correction information was not received up to an hour in case of stable ionospheric condition. It is noteworthy that the outliers of FKP are clustered in their position with some biases. Since several meters of errors can be occurred for kinematic positioning with FKP, therefore, it is necessary to make appropriate preparation for real-time applications.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.73-83
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• 2008

The purpose of this study was to investigate kinematic variables of three types of volleyball jump blocking motions through 3D video analysis. The subjects participated in this study were 7 male university volleyball players and 7 male physical education majors. 1. Regardless of blocking types, peak vertical velocity and jump height in the skilled group were faster and higher than the unskilled group. 2. The skilled group was flexed lower than the unskilled group at E2 of the hip, knee, and ankle joint during the cross over step blocking. 3. In all types of step, the peak angular velocity of the hip, knee, and ankle joint was showed at E2. 4. The skilled group was slower than the unskilled group at E2 of the angular velocity of the hip, knee, and ankle joint during cross over step blocking. In conclusion, the cross over step blocking in which the use of the upper extremities was relatively more available was effective to improve a defence skill for the jump height.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.171-177
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• 2008

This work intends to investigate the effects of pedaling directions on the muscle actions during the bicycle's uphill propulsion. A test rig was developed that consists of a bicyle with a special planetary geartrain, a height-adjustable treadmill, a rear-wheel support and a magnetic brake. A three-dimensional motion analysis was performed for measuring kinematic characteristics of the forward backward pedaling and the electromygraphy(EMG) measurements were simultaneously performed for estimating the muscle actions of the leg. In this work, four muscles are considered including Gastrocnemius muscle(GM), Vastus lateralis(VL), Tibialis anterior(TA) and Soleus(SOL) while the uphill slope is varied from $0^{\circ}$ to $6^{\circ}$. Raw EMG signals were first processed through the root-mean-square(RMS) averaging and then ensemble curves were derived by averaging the EMG RMS envelopes over 50 consecutive cycles. Results show that both the kinemactic characteristics and the muscle actions are significantly affected by the pedaling direction. The crank speed of the forward pedaling is higher but the difference in speed is reduced as the slope is increased. The ensemble curves of the :ac signals clearly exhibit some differences in their patterns, peak values and the corresponding locations with respect to the crank angle. The peak values of most EMG signals are higher for the forward pedaling regardless of the slope magnitude. However, the averages of the EMG signals are not observed to have a similar relationship with the pedaling direction, which seems to be affected by several factors such as less experience of the participants' backward pedaling. inappropriate bicycle design for the backward pedaling. These limitations will be further considered in future work.

• Korean Journal of Applied Biomechanics
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• v.33 no.3
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• pp.110-117
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• 2023

Objective: The purpose of this study was to find out kinematic and kinetic differences the lower extremity joint according to the landing type during vertical jump movement after jump landing, and to present an efficient landing method to reduce the incidence of injury in youth players. Method: Total of 24 Youth players under Korean Sport and Olympic Committee, who used either heel contact landing (HCG) or toe contact landing (TCG) participated in this study (HCG (12): CG height: 168.7 ± 9.7 cm, weight: 60.9 ± 11.6 kg, age: 14.1 ± 0.9 yrs., career: 4.3 ± 2.9 yrs., TCG height: 174.8 ± 4.9 cm, weight: 66.9 ± 9.9 kg, age 13.9 ± 0.8 yrs., career: 4.7 ± 2.0 yrs.). Participants were asked to perform jump landing consecutively followed by vertical jump. A 3-dimensional motion analysis with 19 infrared cameras and 2 force plates was performed in this study. To find out the significance between two landing styles independent t-test was performed and significance level was set at .05. Results: HCG showed a significantly higher dorsi flexion, extension and flexion angle at ankle, knee and hip joints, respectively compared with those of TCG (p<.05). Also, HCG revealed reduced RoM at ankle joint while it showed increased RoM at knee joint compared to TCG (p<.05). In addition, HGC showed greater peak force, a loading rate, and impulse than those of TCG (p<.05). Finally, greater planta flexion moment was revealed in TCG compared to HCG at ankle joint. For the knee joint HCG showed extension and flexion moment in E1 and E2, respectively, while TCG showed opposite results. Conclusion: Compared to toe contact landing, the heel contact landing is not expected to have an advantage in terms of absorbing and dispersing the impact of contact with the ground to the joint. If these movements continuously used, performance may deteriorate, including injuries, so it is believed that education on safe landing methods is needed for young athletes whose musculoskeletal growth is not fully mature.

• Korean Journal of Applied Biomechanics
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• v.18 no.2
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• pp.85-94
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• 2008

The purpose of this study is to provide basic materials for amateur golf players or golf maniacs to learn desirable iron swing motions. This study compared and analyzed the swing motions of iron clubs(3, 6, 9) by using 3-D in three elite golf players. 1. There was no a great difference in the total of swing time by club and the time by phase was nearly similar. 2. There was no a difference in the change in a head location at address and impact by club. 3. The angle change in a right knee joint was similar by club except the difference according to the length of the club. 4. There was a subtle difference in hip rotation angle by club. 5. In each club, the same rotation angle of shoulder joint at address and impact motions contributed to accurate swing, and the maintenance of more than $90^{\circ}$ of shoulder rotation angle in top swing increased swing rotation. 6. Although subtle, the forward angle of upper body was increased with a shorter club. $30-36^{\circ}$ of forward angle of upper body was maintained at address, top swing, and impact motions.