• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.348-356
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• 2009

The purpose of this study was to examine the effect of bridging using Swiss ball, whole body vibration (WBV), and mat on trunk and lower extremity muscle activity and postural stability. The results were as follows: 1) EMG activity of internal oblique increased significantly in WBV condition compared with mat condition (p<.05). 2) EMG activity of rectus femoris and medial gastrocnemius increased significantly in Swiss ball condition and WBV condition compared with mat condition (p<.05). 3) The muscle activity of medial hamstrings increased significantly in Swiss ball condition compared with mat condition (p<.05). 4) The limit of stability in three groups increased significantly in all directions after 4-week intervention (p<.05). 5). There were no significant differences in the limit of stability among three groups after 4-week intervention (p>.05). Therefore the trunk and lower extremity muscle activity increased in Swiss ball and WBV conditions, and postural stability was improved in three groups after intervention period.

• The Journal of Korean Physical Therapy
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• v.27 no.2
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• pp.112-117
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• 2015

Purpose: The purpose of this study was to examine the effects of a task-specific obstacle crossing rehabilitation program on functional gait ability in patients with cerebellar ataxia. Overall, we sought to provide ataxia-specific locomotor rehabilitation guidelines for use in clinical practice based on quantitative evidence using relevant analysis of gait kinematics including valid clinical tests. Methods: Patients with cerebellar disease (n=13) participated in obstacle crossing training focusing on maintenance of dynamic balance and posture, stable transferring of body weight, and production of coordinated limb movements for 8 weeks, 2 times per week, 90 minutes per session. Throughout the training of body weight transfer, the instructions emphasized conscious perception and control of the center of body stability, trunk and limb alignment, and stepping kinematics during the practice of each walking phase. Results: According to the results, compared with pre-training data, foot clearance, pre-&post-obstacle distance, delay time, and total obstacle crossing time were increased after intervention. In addition, body COM measures indicated that body sway and movement variability, therefore posture stability during obstacle crossing, showed improvement after training. Based on these results, body sway was reduced and stepping pattern became more consistent during obstacle crossing gait after participation in patients with cerebellar ataxia. Conclusion: Findings of this study suggest that task-relevant obstacle crossing training may have a beneficial effect on recovery of functional gait ability in patients with cerebellar disease.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.1
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• pp.111-121
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• 2021

PURPOSE: This study examined the effects of core stability exercise on the strength, activation of the trunk muscle, and pulmonary function in a Guillain-Barre syndrome (GBS) patient. METHODS: A 38-year-old male with GBS was enrolled in the study. A core stability exercise program was implemented for four weeks with a duration of 30 min/day and a frequency of three days/week. The program consisted of abdominal crunch, Swiss ball crunch, bicycle crunch, medicine ball sit-up with a toss, medicine ball rotational chest pass, raised upper body and lower body, and dead bug. Measurements of the strength of the trunk muscle (trunk flexion and hip flexion), activation of trunk muscles (rectus femoris; RA, external oblique abdominal; EOA, internal oblique abdominal; IOA, erector spinae; ES), and pulmonary function (forced expiratory capacity; FVC, forced expiratory volume at one second; FEV1) were taken before and after four weeks of core stability exercise. RESULTS: The strength of trunk muscles increased in the trunk and hip flexion after four weeks of core stability exercise, respectively, compared to the baseline levels. Activation of the trunk muscles increased in RA, EOA, and IOA after four weeks of core stability exercise compared to baseline levels, but decreased in ES after four weeks of core stability exercise compared to the baseline levels. The pulmonary function increased in FVC and FEV1 after four weeks of core stability exercise compared to the baseline levels. CONCLUSION: These results suggest that core stability exercise improves strength, Activation of the trunk muscle, And pulmonary function in patients with GBS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.385-394
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• 2012

A computer program that can estimate static, dynamic stability and control derivatives using a subsonic-supersonic panel method is developed. The panel method uses subsonic-supersonic source and elementary horse shoe vortex distributions, and their strengths are determined by solving the boundary condition approximated with a thin body assumption. In addition, quasi-steady analysis on the body fixed coordinate system allows the estimation of damping coefficients of aircraft 3 axes. The code is validated by comparing the neutral point, roll and pitch damping of delta wings with published analysis results. Finally, the static, dynamic stability and control derivatives of F-18 are compared with experimental data as well as other numerical results to show the accuracy and the usefulness of the code.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_1
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• pp.881-888
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• 2020

A butterfly valve is a valve that adjusts flow rate by rotating a disc for about 90° with respect to the axis that is perpendicular to the flow path from the center of its body. This valve can be manufactured for low-temperature, high-temperature and high-pressure conditions because there are few restrictions on the used materials. However, the development of valves that can be used in a 600℃ environment is subject to many constraints. In this study, the butterfly valve's stability was evaluated by a fluid-structured interaction analysis, thermal-structure interaction analysis, and seismic analysis for the development of valves that can be used in high-temperature environments. When the reverse-pressure was applied to the valve in the structural analysis, the stress was low in the body and seat compared to the normal pressure. Compared with the allowable strength of the material for the parts of the valve system, the minimum safety factor was approximately 1.4, so the valve was stable. As a result of applying the design pressures of 0.5 MPa and 600℃ under the load conditions in the thermal-structural analysis, the safety factor in the valve body was about 3.4 when the normal pressure was applied and about 2.7 when the reverse pressure was applied. The stability of the fluid-structure interaction analysis was determined to be stable compared to the 600℃ yield strength of the material, and about 2.2 for the 40° open-angle disc for the valve body. In seismic analysis, the maximum value of the valve's stress value was about 9% to 11% when the seismic load was applied compared to the general structural analysis. Based on the results of this study, the structural stability and design feasibility of high-temperature valves that can be used in cogeneration plants and other power plants are presented.

• Bulletin of the Society of Naval Architects of Korea
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• v.15 no.1
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• pp.7-9
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• 1978

In this calculation of statical stability of a ship, mechanical integrator was used most popularly and the direct calculation method such as a Barn's wedge method was also adopted in some cases. Both of the above method was developed for manual calculation which include mechanical integration or drafting procedure on body plan. Therefore, the computerization of stability calculation by the above method is very difficult. In this paper a simplified method for stability calculation is suggested, with based on hydrostatic data and immerged wedged characteristics.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.510-516
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• 1998

Dynamic stability of a high speed train is very important. This paper presents a dynamic stability analysis of K-TGV using Vampire Program. The analysis of stability on this paper is performed in condition of track irregularity, curved track and strong gust. The critical speed of K-TGV is 140m1s, and it is stable when runs on 7000R(cant 150mm) curved track and on linear track with the body exerted 101kN lateral impulse force.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.523-529
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• 2008

The course stability performance for tankers is evaluated by computational fluid dynamics. In the present work, a Reynolds averaged Navier-Stokes (RANS) code is applied to a maneuvering problem covering the pure drift and yaw motions. The purposes of this study are to evaluate the hydrodynamic force in the bare hull (AFRAMAX) in pure drift and yaw motion and to provide information about the trends in the forces and moments when the rudder angles are varied. The flow simulation is performed by FLUENT. The CFD code is examined to find the optimistic computational condition such as size of grid, turbulence model and initial condition. The hydrodynamic derivatives in drift and pure yaw motion are estimated by the numerical simulation, and then the stability levers are calculated. It is confirmed that the computations show the superiority and inferiority of course stability performance according to the hull forms. Finally, the CFD code is applied to the estimation of the rudder forces when the rudder angles are varied. The propeller effect expressed by the body force distribution is also included.

• Journal of Biomedical Engineering Research
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• v.30 no.6
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• pp.521-528
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• 2009

This study is about to evaluation of postural stability according to characteristics of electrical stimulation on the ankle muscles. We measured body sway(center of pressure, COP) when various parameters of electrical stimulation was applied to ankle muscles in stable and unstable posture. Subjects consisted of 10 young adults, and electrical stimulation was delivered on right and left of tibialis anterior and Achilles tendon. The body sway was measured during electrical stimulation of three duty cycle and frequencies in stable posture and three amplitudes of sensory threshold in unstable posture. Consequently, the COP Shift is higher during electrical stimulation of 1/30(duty ratio) and 100Hz(frequency) in stable posture. In unstable posture, 100% amplitude of sensory threshold induced postural stability. These findings are important for the rehabilitation system of postural stability and the use of electrical stimulation as somatosensory information.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4142-4148
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• 2013

Because of effective fruit growing and management in the slope land, the use of orchard vehicle with lifting utilities has been increased. For this reason the study on the stability of that vehicle for worker's safety is needed. This study is investigated on the stability estimation of orchard vehicle with four wheels and dual rectangular-type lifting utilities which can be moved on the dirt sloping load. Through the multi-body dynamics analysis on the vehicle mechanism, overturning angles of 19.2 and $34.6^{\circ}$ in the right-left and front-rear direction can be calculated. It is determined tractive resistances and required powers of the wheels. And through the finite element analysis on the frame of lifting utility its maximum von-Mises stress is 146 MPa and it is structural stable. Therefore it is known that the orchard vehicle with wheels and lifting utilities has static and dynamic stability.