• Geomechanics and Engineering
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• v.39 no.1
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• pp.87-104
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• 2024

In practical engineering, the design process for most retaining walls necessitates careful consideration of seismic resistance. The prevention of retaining wall overturning is of paramount importance, especially in cases where the foundation's bearing capacity is limited. To research the seismic active earth pressure (ES) of a relieving retaining wall rotating around base (RB), the shear dissipation graphs across various operating conditions are analyzed by using Optum software, and the earth pressure in each region was derived by the inclined strip method combined with the limit equilibrium method. By observing shear dissipation graphs across various operating conditions, the distribution law of each sliding surface is summarized, and three typical failure modes are obtained. The corresponding calculation model was established. Then the resultant force and its action point were obtained. By comparing the theoretical and numerical solutions with the previous studies, the correctness of the derived formula is proved. The variation of earth pressure distribution and resultant force under seismic acceleration are studied. The unloading plate's position, the wall heel's length, and seismic acceleration will weaken the unloading effect. On the contrary, the length of the unloading plate and the friction angle of the filling will strengthen the unloading effect. The derived formula proposed in this study demonstrates a remarkable level of accuracy under both static and seismic loading conditions. Additionally, it serves as a valuable design reference for the prevention of overturning in relieving retaining walls.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.241-247
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• 2011

Marine casualties of vessel are said to be in most case caused by human error, but it would be valid for the assumption that the ship is built with high quality and then should be acceptable to the safety standards. It means that the inherent characteristics of a ship should be the first consideration on the safety of ship. Therefore it is basically necessary for navigator to grasp the inherent stability of his ship and ensure that the ship complies with the minimum statutory standards of stability. This study is to realize the stability of the Korean offshore large purseiner varying with loading conditions by the inclining data and some calculations. The author compared the stability of the ship with IMO criteria and domestic rule, and proposed some improvement for the safety of the ship. The results are summarized as follows ; The values of GM of the ship according to the loading condition in navigation satisfy both of the IMO criteria and the domestic rule, but in case of the area under the GZ curves between the heel angles of $30^{\circ}$ and $40^{\circ}$, and the heel angle occuring the maximum righting lever not satisfy the IMO rule at the fishing ground departure and arrival conditions in the haul in net situation. The initial metacentric height of the ship is very large, but the range of stability and the occurring angle of the maximum GZ are very small, so even small inclining can bring about the beam end. The best method of improvement for that is to increase the freeboard of the model among the variables.

• Korean Journal of Applied Biomechanics
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• v.30 no.1
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• pp.73-81
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• 2020

Objective: The purpose of this study is to analyze the effects of aquatic walking exercise on gait and balance parameters of elderly women. Method: 15 elderly people were recruited for this study (age: 73.20±5.19 yrs, height: 153.87±3.36 cm, mass: 60.33±5.73 kg). All variables were measured using Gaitview AFA-50. The variables were the heel contact time ratio, gait angle, and M/P change ratio for gait patterns and ENV, REC, RMS, Total Length, TLC, Sway velocity, and Length/ENV for balance abilities. A paired t-test and the Wilcoxon signed-rank test were carried out to verify the differences in the test scores after participating in the water walking program. The significance level for all statistical analyses was set to α=.05. Results: As for the changes in their walking function after the exercise, heel contact time ratio (p<.01) showed a statistical significance, while gait angle and M/P change ratio did not reveal statistically significant differences. In the test of balance ability on both feet and with eyes opened, statistical significance was found in ENV, REC, RMS, TLC (p<.01), and sway velocity (p<.05), while the test with eyes closed showed statistical significance in length/ENV as well as ENV, REC, RMS, sway velocity (p<.01) TLC, and total length (p<.05). As for the single-leg stance balance ability, ENV and REC revealed statistically significant differences. Conclusion: These results show that water walking is effective for improving the function of the ankle flexor muscles, providing stability to the ankle joint during walking and helping efficient walk. In addition, it is also expected to help prevent falls due to loss of balance by improving the stability of lower extremity muscles and trunk.

• Journal of the Ergonomics Society of Korea
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• v.35 no.5
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• pp.319-341
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• 2016

Objective:This research analyzed the lower-limb motion in kinetic and kinematic way while walking on various terrains to develop Foot-Ground Contact Detection (FGCD) algorithm using the Inertial Measurement Unit (IMU). Background: To estimate the location of human in GPS-denied environments, it is well known that the lower-limb kinematics based on IMU sensors, and pressure insoles are very useful. IMU is mainly used to solve the lower-limb kinematics, and pressure insole are mainly used to detect the foot-ground contacts in stance phase. However, the use of multiple sensors are not desirable in most cases. Therefore, only IMU based FGCD can be an efficient method. Method: Orientation and acceleration of lower-limb of 10 participants were measured using IMU while walking on flat ground, ascending and descending slope and stairs. And the inertial information showing significant changes at the Heel strike (HS), Full contact (FC), Heel off (HO) and Toe off (TO) was analyzed. Results: The results confirm that pitch angle, rate of pitch angle of foot and shank, and acceleration in x, z directions of the foot are useful in detecting the four different contacts in five different walking terrain. Conclusion: IMU based FGCD Algorithm considering all walking terrain possible in daily life was successfully developed based on all IMU output signals showing significant changes at the four steps of stance phase. Application: The information of the contact between foot and ground can be used for solving lower-limb kinematics to estimating an individual's location and walking speed.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.1
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• pp.127-137
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• 2022

PURPOSE: This study sought to evaluate muscle activity and foot pressure during gait, and balance in female college students with genu valgum. METHOD: Participants were assigned based on their Q-angle to genu valgum group greater than 20° (GVG, n = 12), unilateral genu valgum group greater than 20° (UVG, n = 11), and control group (CON, n = 13). All subjects were evaluated for balance (Trace length, C90 area, C90 angle, and the Romberg test), muscle activity (gluteus medius; GM, tensor fasciae latae; TFL, vastus medialis; VM, vastus lateralis; VL, biceps femoris; BF, gastrocnemius; GCM and tibialis anterior; TA) and foot pressure (F/F ratio, R/F ratio, Hallux, 2~5 toe, 1st MT, 2~4 MT, 5th MT, Midfoot, M/heel, and L/heel) during gait. RESULTS: Romberg test showed significantly increased loss of balance in the UVG group compared with the CON. In the forward position, the imbalance was significantly increased in the UVG and GVG groups compared to the CON. Muscle activity of VL, GCM, and TA significantly increased in the GVG group compared with the CON. Static foot pressure, 1st MT significantly increased in the GVG compared to the CON group. The 5th MT significantly decreased in the CON compared with the GVG group. The R/F ratio significantly decreased in the GVG compared to the CON group. In dynamic foot pressure, the 2~5 toe significantly increased in the GVG compared with the UVG group. The left 5th MT significantly decreased in the UVG compared with the CON and GVG groups. CONCLUSION: These results indicate that genu valgum has a negative effect on balance, muscle activity, and foot pressure during gait in female college students.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.2
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• pp.209-217
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• 2016

Unlike conventional airplane, a WIG craft experiences righting moment and adverse yaw moment in banked turning in ground effect. Numerical simulations are carried out to study the aerodynamics of banked wing in ground effect. Configurations of rectangular wing and delta wing are considered, and performance of endplates and ailerons during banking are also studied. The study shows that righting moment increase nonlinearly with heeling angle, and endplates enhance the righting. The asymmetric aerodynamic distribution along span of wing with heeling angle introduces adverse yaw moment. Heeling in ground effect with small ground clearance increases the vertical aerodynamic force and makes WIG craft climb. Deflections of ailerons introduce lift decrease and a light pitching motion. Delta wing shows advantage in banked turning for smaller righting moment and adverse yaw moment during banking.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.205-213
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• 2021

Objective: The aim of this study was to analyze body stability Joint coordination pattern though as bending stiffness of shoes during stance phase of running. Method: 47 male subjects (Age: 26.33 ± 2.11 years, Height: 177.32 ± 4.31 cm, Weight: 65.8 ± 3.87 kg) participated in this study. All subjects tested wearing the same type of running shoes by classifying bending stiffness (A shoes: 3.2~4.1 N, B shoes: 9.25~10.53 N, C shoes: 20.22~21.59 N). They ran 10 m at 3.3 m/s (SD ±3%) speed, and the speed was monitored by installing a speedometer at 3 m intervals between force plate, and the measured data were analyzed five times. During running, ankle joint, MTP joint, coupling angle, inclination angle (anterior-posterior, medial-lateral) was collected and analyzed. Vector coding methods were used to calculate vector angle of 2 joint couples during running: MTP-Ankle joint frontal plane. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was Bonferroni. Results: Results indicated that there was an interaction between three shoes and phases for MTP (Metatarsalphalangeal) joint angle (p = .045), the phases in the three shoes showed difference with heel strike~impact peak (p1) (p = .000), impact peak~active peak (p2) (p = .002), from active peak to half the distance to take-off until take-off (p4) (p = .032) except for active peak~from active peak to half the distance to take-off (p3) (p = .155). ML IA (medial-lateral inclination angle) for C shoes was increased than other shoes. The coupling angle of ankle angle and MTP joint showed that there was significantly difference of p2 (p = .005), p4 (p = .045), and the characteristics of C shoes were that single-joint pattern (ankle-phase, MTP-phase) was shown in each phase. Conclusion: In conclusion, by wearing high bending stiffness shoes, their body instability was increased during running.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.223-229
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• 2011

When negative electron in x-ray tube is accelerated in to a high speed and then the currency of the electron is blocked by the target, x-ray happens by the conversion of the energy. The real area where the fast accelerated electron collides to a target area is called actual focal spot. When the string focused size is observed at the central ray side, where the direction x-ray comes out, the size seems to be reduced. This focus is called effective focal spot. According to radiation angle of x-rays tube, the degree of the negative pole side presents higher value than inclination, the amount of exposed radiation that patient receives differs by the angle of positive pole, which means effective focal spot is the variable. This paper presents the correlation between size of effective focal spot and amount of exposed radiation to the patient by it, and effective research for homogenized dose dispersion by the size of effective focal spot. In conclusion, following the focal size, effective range which was -8cm ~ 0 cm on average, was found and average dose rate was 0.019 R/min. Through this range, for patients with small radiation exposure, image with good density and resolution in aspect of diagnosing will be able to be obtained.

• Journal of the Ergonomics Society of Korea
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• v.34 no.4
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• pp.303-312
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• 2015

Objective: The aim of this study is to investigate the effect of insole height change in the lumbosacral angle and physical functions in healthy males. Background: In order to release male's dissatisfaction with his height and to increase satisfaction with his body, using insole is generalized. There have been researches on female's body change in accordance with function of insole and heel height, whereas there are few researches on males. Method: Participants were divided into three groups. A control group had 10 participants who wore 0cm insole. Experimental group I had 10 participants who wore 2cm insole. Experimental group II had 10 participants who wore 4cm insole. All participants wore insoles during their daily lives for a trial period of 8 weeks. The results were evaluated before and after comparison, and we measured lumbosacral angle, balance (dynamic balance, agility, quickness) and lumbar pain (LBP). Results: This study showed that insole height affected lumbosacral angle and dynamic balance and pain. In particular, there were significant differences in the 4cm group among the three groups (p<.05). The 2cm group did show a significant difference in lumbosacral angle and pain (p<.05). Furthermore, no significant difference was observed within the control group. Conclusion: The 4cm insole height suggests that the increase of lumbosacral angle contributes to some changes in LBP, balance, pain and physical functions, probably leading to negative effects on variety of activities of daily life. Application: The results of wearing insoles with proper height will help to prevent musculoskeletal disorders.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.654-659
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• 2016

Recently, the passenger ship 'Sewol' capsized with an abrupt inclination while she was making a small angle alteration. It is very important to fully understand the concepts, causes and relevant corrections for a ship's transverse inclination, which is classified into heel, list and loll. In this study, the concept, development and calculation of loll were well considered and the actual magnitude of the angle of loll was simulated in a box-shaped model-ship experiment. The experimental values and its development according to different values of negative stability were compared with calculated values. In the results, experimental values for the angle of loll coincided closely with calculated values and the model inclined symmetrically on both port and starboard sides indicating an outstanding feature of loll. This study is expected to expand the concept of loll and help in the analysis of capsize incidents with unknown causes. Further experimental research or case studies concerning the risk of inappropriate correction for loll arising from misunderstandings will be needed.