• Korean Journal of Applied Biomechanics
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• v.24 no.2
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• pp.95-101
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• 2014

The purpose of this study was to investigate the training and detraining effects of a 8-week water exercise on lower extremities coordination during obstacle gait in the female elderly. Eight elderly participants (age: $76.58{\pm}4.97$ yrs, height: $148.88{\pm}7.19$ cm, body mass: $56.62{\pm}6.82$ kg, and leg length: $82.36{\pm}2.98$ cm), who stayed at the Seoul K welfare center, were recruited for this study. All participants had no history of orthopedic abnormality within the past 1 year and completed the aquatic exercise program which lasted for 8 weeks. To identify the training and detraining effect of 8 weeks of water exercise, a 3-D motion analysis with 7 infrared cameras and one force plate sampling frequency set at 100 Hz and 1,000 Hz, respectively, was performed. A two-way ANOVA was performed to find training and detraining effects among diferent obstacle heights. In this study significant level was set at .05. Significant training effects of LTS (lead foot thigh and shank) coordination in all obstacle height were found (p<.05). It is also found that the training effect of LTS remained 37%, 58%, and 25% in obstacle height of 30%, 40%, and 50%, respectively. Lead foot showed the greater detraining effect of coordination compared with trail foot, and SF (shank and foot) coordination revealed better detraining effects of coordination compare with TS (thigh and shank) in both feet. Based on the findings, a 8 week water exercise give an positive effects to the elderly in terms of segment cooperation which potentially helps reducing their accident falls. The magnitude of detraining may also help the elderly to find the retraining moment.

• The Journal of Korean Physical Therapy
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• v.28 no.1
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• pp.14-21
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• 2016

Purpose: The purpose of this study was to investigate examine how the kinematics and kinetics of lower limb joints were changed depending on the unstable shoes (US) during sit-to-stand task (SitTS). Methods: Nineteen healthy females were participated in this study. The subjects performed sit-to-stand task with US and barefoot. The experiment was repeated three times for each tasks with conditions. The kinematics and kinetics of lower limb joint were measured and analyzed using a 3-D motion analysis system. A paired t-test was utilised performed for to identificationy of changes in mean of angle, force, and moment between both the two conditions. Results: The results of this study showed kinematic differences in lower limb joints during SitTS based on the US. The hip, knee, and ankle angle showed statistically significant differences during SitTS. At the initial of SitTS, Tthe force and moment of the hip flexor, hip extensor, knee flexor, knee extensor, ankle flexor, and ankle extensor showed statistically significant differences. At the terminal of SitTS, Tthe force and moment of the hip flexor, hip extensor, knee flexor, knee extensor, ankle flexor, and ankle extensor showed statistically significant differences. At the maximum of SitTS, Tthe moment of the hip extensor showed statistically significant differences. The force and moment of the ankle flexor, extensor moment showed statistically significant differences. Conclusion: Therefore, Wwearing US is considered to influence on the lower limb joints kinematics and kinetics during SitTS movements, and thus suggests the possibility that of reducing the risks of pain, and osteoarthritis caused by changes in the loading of lower limb joints.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.227-237
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• 2002

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1019-1022
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• 2015

사회적 약자인 청각장애인들의 수화통역 서비스가 대체로 만족스럽게 제공되고 있지 않다. 또한 청각 장애인수 대비 수화통역가의 부족과 일반인과의 즉각적인 소통이 어려워 일상생활에 불편함을 느끼는 청각장애인들이 많다. 이의 문제점을 착안하여 본 연구에서는 청각장애인들이 휴대할 수 있는 수화 통역기를 개발하고자 한다. 청각장애인들의 손동작을 인식할 수 있는 3D센서 립모션(Leap-Motion)을 통해 수화를 인식한다. 립모션 센서와 안드로이드 스마트폰 및 태블릿과 연결하여 손 데이터 값을 분석했다. 분석한 손 데이터 값과 특정 지화(자음, 모음)와 간단한 인사말의 수화동작을 취할 때, 트래킹되는 데이터 값을 비교하여 수화를 인식하고 수화와 인식된 지화의 자음과 모음을 글자로 완성시켜, 텍스트와 음성으로 출력한다. 또한 립모션이 부착된 하드케이스 안에 스마트기기 탈착이 가능한 실용성 있는 수화통역기 제품 개발에 대한 연구를 목표로 하고 있다.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.169-180
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• 2019

The underlying mechanism of the wind-induced vibration of the hangers of the suspension bridges is still not fully understood at present and hence is comprehensively examined in this study. More specifically, a series of field measurements on the No. 2 hanger of the Xihoumen Bridge was first carefully conducted. Large amplitude vibrations of the hanger were found and the oscillation amplitude of the leeward cable was obviously larger than that of the windward cables. Furthermore, the trajectory of the leeward cable was close to an ellipse, which agreed well with the major characteristics of wake-induced vibration. Then, a theoretical model for the wake-induced vibration based on a 3-D continuous cable was established. To obtain the responses of the leeward cable, the finite difference method (FDM) was adopted to numerically solve the established motion equation. Finally, numerical simulations by using the structural parameters of the No. 2 hanger of the Xihoumen Bridge were carried out within the spatial range of $4{\leq}X{\leq}10$ and $0{\leq}Y{\leq}4$ with a uniform interval of ${\Delta}X={\Delta}Y=0.25$. The results obtained from numerical simulations agreed well with the main features obtained from the field observations on the Xihoumen Bridge. This observation indicates that the wake-induced vibration might be one of the reasons for the hanger oscillation of the suspension bridge. In addition, the effects of damping ratio and windward cable movement on the wake-induced vibration of the leeward cable were numerically investigated.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.4
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• pp.139-148
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• 2018

PURPOSE: This study compared the effects of indoor and outdoor environmental changes on the activity of the major lower limb muscles and walking factors in people 40-50 years and those aged older than 70 years. METHODS: Ten middle-aged people in their forties (age:$44.2{\pm}2.7$, BMI:$21.8{\pm}1.8$) and 10 elderly aged more than 70 years (age:$76.4{\pm}5.9$, BMI:$22.2{\pm}1.9$) with a normal walking ability were included. The participants walked 100 m both indoors and outdoors at their own speed. Using a 3D motion analyzer and EMG, the walking speed, angle of the ankle and activity changes of the lower limb muscles were compared. RESULTS: Significant differences in walking speed and peak-plantar flexion angle were observed between the two groups (p<.05). The muscular activity of the gastrocnemius muscle (GCM) was significantly different outdoors in the swing phase between the two groups (p<.05). In the people aged in their forties, the muscular activity of the rectus femoris (RF) was significantly higher outdoors than indoors (p<.05). In the elderly, however, the muscular activity of the RF was lower outdoors than indoors (p<.05). When compared to those in there forties, the muscular activity of the outdoor RF significantly decreased in the elderly group (P<.05). The muscular activity of the biceps femoris (BF) in the elderly decreased significantly outdoors compared to indoors (p<.05). CONCLUSION: For the elderly, increasing the exposure to the new environments or focusing on the performance of repeated movements for gradual speed control and precise movements is required to maintain normal gaits and movements that are less affected by environmental changes.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.400-410
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• 2019

In this study, the numerical code for the 3D nonlinear dynamic analysis of an SLWR (Steel Lazy Wave Riser) was developed using the lumped mass line model in a FORTRAN environment. Because the lumped mass line model is an explicit method, there is no matrix operation. Thus, the numerical algorithm is simple and fast. In the lumped mass line model, the equations of motion for the riser were derived by applying the various forces acting on each node of the line. The applied forces at the node of the riser consisted of the tension, shear force due to the bending moment, gravitational force, buoyancy force, riser/ground contact force, and hydrodynamic force based on the Morison equation. Time integration was carried out using a Runge-Kutta fourth-order method, which is known to be stable and accurate. To validate the accuracy of the developed numerical code, simulations using the commercial software OrcaFlex were carried out simultaneously and compared with the results of the developed numerical code. To understand the nonlinear dynamic characteristics of an SLWR, dynamic simulations of SLWRs excited at the hang-off point and of SLWRs in regular waves were carried out. From the results of these dynamic simulations, the displacements at the maximum bending moments at important points of the design, like the hang-off point, sagging point, hogging points, and touch-down point, were observed and analyzed.

• Physical Therapy Korea
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• v.26 no.2
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• pp.1-7
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• 2019

Background: In previous studies, changes in postural alignment were found when the slope was changed during walking. Downhill walking straightens the trunk by shifting the line of gravity backward. Objects: This study investigated the effect of the downhill treadmill walking exercise (DTWE) on thoracic angle and thoracic erector spinae (TES) activation in subjects with thoracic kyphosis. Methods: A total of 20 subjects with thoracic kyphosis were recruited for this study. All the subjects performed the DTWE for 30 minutes. A surface EMG and 3D motion capture system were used to measure TES activation and thoracic angle before and after the DTWE. Paired t-tests were used to confirm the effect of the DTWE (p<.05). Results: Both the thoracic angle and TES activation had significantly increased after the DTWE compared to the baseline (p<.05). An increase in the thoracic angle indicates a decrease in kyphosis. Conclusion: The DTWE is effective for thoracic kyphosis patients as it decreases their kyphotic posture and increases the TES activation. Future longitudinal studies are required to investigate the long-term effects of the DTWE.

• PNF and Movement
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• v.17 no.1
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• pp.41-46
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• 2019

Purpose: Continuous use of a smartphone increases the angle of forward bending of the user's cervical vertebrae, causing pain in the shoulders and back, including the thorax, lumbar region, and vertebrae. Although there are many studies on changes in the cervical spine due to smartphone usage, the changes in the shoulders, thoracolumbar spine, and pelvic have rarely been compared. The purpose of this study is to investigate the change in the spinal segments, shoulders, and pelvic when using a smartphone with both hands while in the standing position. Methods: This study was conducted on 35 adults in their twenties. The selection criteria for the subjects were limited to those in a similar age group, thus excluding posture differences according to age, and to those who did not have specific diseases or pain in the spinal and musculoskeletal system for 12 months prior to the study. In this study, we used a 3D spinal diagnostic imaging system (Back Mapper, Frickenhausen) to compare the changing conditions in each vertebral segment before and during smartphone usage with both hands while in the standing position. Posture differences according to smartphone usage were compared using the paired t-test for the motion of each spinal segment. Results: This study showed that the thoracic and lumbar angle increased posteriorly during smartphone usage (p<0.05). In addition, the anterior rotation angle of the shoulder bone significantly increased, but no significant difference occurred in the pelvic region. Conclusion: Based on the results of this study, smartphone usage with both hands while in the standing position showed that the spine, as a whole, forms a kyphotic curve. Therefore, we propose to present a postural guideline for correct smartphone usage, considering the change in each vertebral segment.

• Korean Journal of Acupuncture
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• v.38 no.3
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• pp.175-181
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• 2021

A 57-year-old female diagnosed with L5-S1 lumbar intervertebral disc herniation, suffering from severe pain despite taking tapentadol received combined Korean medicine treatment, including acupotomy, acupuncture, pharmacopuncture, and herbal therapies for 53 days. To assess pain, Numeric Rating Scale (NRS) and lumbar range of motion (ROM) were checked daily from the day of admission. Moreover, the Oswestry Disability Index (ODI) and European Quality of Life-5 Dimensions (EQ-5D) were used to evaluate function and quality of life. After combined Korean medicine treatment, reabsorptioin of intervertebral disc was confirmed by radiological examination; pain reduced from NRS 5~7 to NRS 1~2; lumbar ROM in extention increased from 20° to 30°; and function and quality of life improved. The results suggest the possibility that a combined Korean medical treatment, including acupotomy, can be used as an alternative to opioids for pain management of lumbar vertebral disc herniation.