• The Journal of Korean Physical Therapy
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• v.35 no.6
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• pp.213-219
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• 2023

Purpose: In this study, based on the error augmentation, we performed walking training with increased rhythmic auditory stimulation speed on the affected side (IRAS) and walking training with decreased rhythmic auditory stimulation speed on the unaffected side (DRAS). The purpose of this study was to verify whether motor learning was effective in improving balance ability. Methods: Twenty-eight subjects with chronic stroke were recruited from a rehabilitation center. The subjects were divided into three groups: an IRAS group (10 subjects), a DRAS group (9 subjects), and control group (9 subjects). They received 30minutes of neuro-developmental therapy and walking training for 30minutes, five times a week for three weeks. Static and functional balance ability were measured before and after the training period. Static balance was measured by balancia software. Functional balance was measured by the timed up and go test (TUG) and the berg balance scale (BBS). Results: After the training periods, the IRAS group showed a significant improvement in TUG, BBS, area 95% COP, and weight distribution on the affected side when compared to both the DRAS group and control group (p<0.05). Conclusion: Based on the results of this study, it is possible to consider error augmentation methods of motor learning if rhythmic auditory stimulation is applied to stroke patients in clinical practice. If the affected side is shorter than the unaffected side, the affected side should be adjusted to the increased rhythmic auditory stimulation speed, which is considered to be an effective intervention to improve balance ability.

• The Journal of Korean Physical Therapy
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• v.20 no.4
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• pp.7-13
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• 2008

Purpose: We compared T-type and I-type canes on postural balance in 28 hemiplegic patients. Methods: Subjects were allocated randomly into two groups: a T-shape cane group (n=14) and an I-shape cane group (n=14). Before the test, subjects were trained by a physical therapist to walk with a cane for 6 weeks. The Main Outcome Measures were measured as maximal sway velocity, sway path, sway area, and partial weight bearing using a Balance Performance Monitor (BPM) and ambulation velocity using a 'Timed up and go test'. We also measured the maximal ambulation velocity. Results: The distribution of weight bearing on the affected side without the cane was 35% in the I-shape cane group and 36% in the T-shape cane group. After training, weight bearing on the affected side increased by 45% in the I-shape cane group and 40% in the T-shape cane group. With the cane held in the hand, weight bearing on the affected side in the T-shape cane group decreased by 3%. Conclusion: The I-shaped cane increased static standing balance, including hemiplegic side weight bearing. Therefore, I-shape canes can improve the balance of hemiplegic patients.

• Composites Research
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• v.13 no.2
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• pp.61-71
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• 2000

Today, the use of composite materials become an essential part in the design and manufacturing process of the flight vehicles to reduce the structural weight. Since the structural properties can be varied largely due to the stacking sequence of ply angles, it is very important problem to determine the optimized ply angles under a design objective. Thus, in this study, the analysis of static aeroelastic optimization of a composite wing has been performed. An analytical system to calculate and optimize tile aero-structural equilibrium position has been developed and incorporated with the genetic algorithm. The effects of stacking sequence on the structural deformation and aerodynamic distribution have been studied and calculated with the condition of minimum structural deformation for a swept-back composite wing. For the set of practical stacking angles, the design results to maximize the performance of static aeroelasticity are also presented.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.2
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• pp.235-246
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• 2011

Purpose: The aim of this study is to compare and assess the effects of lumbar stabilization exercise on the balance ability of young college studets with low back pain after having performed spinal stabilization exercise by using 3-dimensional air-balance system and gym ball. Methods: The subjects of this study were 34 low back patients in their early twenties. They were divided into two groups: 3-dimensional lumbar stabilization exercise group(N=17) and gym ball lumbar stabilization exercise group(N=17). The period of the intervention was for five weeks. VAS(Visual Analogue Scale) for pain test, ODI(Oswestry Disability Index) for ADL limitation test, Tetrax system for static balance test, and Air-balance system 3D for dynamic balance test were used as evaluation tools for this study. Results: Pain showed significant decrease in both groups after having performed the experiment, but ADL limitation of the groups did not show any remarkable difference between before and after the experiment. Dynamic balance ability in the 8-directional angle comparison test significantly increased in all directions except for the backward, left-backward, and right-backward directions. As for dynamic balance ability in the 8-directional postural test, 3D exercise group showed statistically significant reduction in every direction while gym ball exercise group did not(p<.05). However, when it comes to static balance ability in the weight distribution and stability test, there was not significantly change between pre and post test in both groups. Conclusion: This study shows 3-dimensional lumbar stabilization exercise is more effective in the lumbar stabilization of coordinated movement than gym ball exercise, which may imply that 3D air-balance system can be used for the therapeutic treatment of body imbalance for patients with low back pain.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.243-246
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• 2005

The weight reduction of carbody stl1lctures is of great concern in developing high speed tilting train for the normal operation of tilting system. The use of composite materials for the carbody structures has many advantages due to their excellent material propel1ies. In this paper, finite element analysis was conducted to verify the safety of the composite structures of Tilting Train eXpress(TTX). A train prototype with carbon/epoxy composite carbody was manufactured to perform static loading tests according to JIS E 7105. The loading tests were simulated by FE analysis to compare with the test results. To obtain more accurate and detailed result of stress distribution in local region of carbody, the submodeling approach was used. The submodeling analysis results showed the high levels of stress concentration occured on window frame part of TTX as the loading test results did.

• Advances in concrete construction
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• v.15 no.2
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• pp.97-114
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• 2023

The nonlocal strain gradient theory for the static bending analysis of graphene nanoplatelets (GPLs) reinforced the nanoplate is developed in this paper. The nanoplatelet is exposed to thermo-mechanical loads and is also supposed to stand on an elastic foundation. For computing impressive composite material characteristics, the Halpin-Tsai model is selected for various sectors. The various distributions are propounded including UD, FG-O, and FG-X. The represented equations are acquired based on the virtual work and sinusoidal shear and normal deformation theory (SSNDT). Navier's solution as the analytical method is applied to solve these equations. Furthermore, the effects of GPL weight fraction, temperature parameters, distribution pattern and parameters of the foundation are presented and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.304-311
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• 2001

This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.115-126
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• 2016

Objective: The purpose of this study was to investigate plantar foot pressure and static balance according to the type of insole in the elderly. Methods: Thirteen elderly (mean age: $67.08{\pm}2.25years$, mean height: $159.63{\pm}9.64cm$, mean body weight: $61.48{\pm}9.06kg$) who had no previous injury experience in the lower limbs and a normal gait pattern participated in this study. Three models of insoles of the normal, 3D, and triangle types were selected for the test. The Pedar-X system and Pedar-X insoles, 3.3 km/h of walking speed, and a compilation of 20 steps walking stages were used to analyze foot-pressure distribution. Static balance test was conducted using Gaitview AFA-50, and balance (opening eyes, closing eyes) was inspected for 20 s. One-way ANOVA was conducted to test the significance of the results with the three insoles. p-value of less than .05 was considered statistically significant. Results: The mean foot pressure under the forefoot regions was the lowest with the 3D insole during treadmill walking (p<.05). The mean value under the midfoot was the highest with the 3D insole (left: p<.05, right: p<.01). The mean value under the rearfoot was the lowest with the 3D insole (p<.001). The maximum foot pressure value under the foot regions was the lowest on both sides of the forefoot with the 3D insole. A statistically significant difference was seen only in the left foot (p<.01). The maximum value under the midfoot was the highest with the 3D insole (p<.001). No statistically significant difference was detected on the values under the rearfoot. In the case of vertical ground reaction force (GRF), statistically significant difference was seen only in the left side rearfoot (p<.01). However, static balance values (ENV, REC, RMS, Total Length, Sway velocity, and Length/ENV) did not show significant differences by the type of insole. Conclusion: These results show that functional insoles can decrease plantar pressure and GRF under the forefoot and rearfoot. Moreover, functional insoles can dislodge the overload of the rearfoot and forefoot to the midfoot. However, functional insoles do not affect the static balance in the elderly.

• Structural Engineering and Mechanics
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• v.24 no.6
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• pp.709-725
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• 2006

In this paper the buckling and post-buckling behavior of slender bars under self-weight are studied. In order to study the post-buckling behavior of the bar, a geometrically exact formulation for the non-linear analysis of uni-directional structural elements is presented, considering arbitrary load distribution and boundary conditions. From this formulation one obtains a set of first-order coupled nonlinear equations which, together with the boundary conditions at the bar ends, form a two-point boundary value problem. This problem is solved by the simultaneous use of the Runge-Kutta integration scheme and the Newton-Raphson method. By virtue of a continuation algorithm, accurate solutions can be obtained for a variety of stability problems exhibiting either limit point or bifurcational-type buckling. Using this formulation, a detailed parametric analysis is conducted in order to study the buckling and post-buckling behavior of slender bars under self-weight, including the influence of boundary conditions on the stability and large deflection behavior of the bar. In order to evaluate the quality and accuracy of the results, an experimental analysis was conducted considering a clamped-free thin-walled metal bar. As this kind of structure presents a high index of slenderness, its answers could be affected by the introduction of conventional sensors. In this paper, an experimental methodology was developed, allowing the measurement of static or dynamic displacements without making contact with the structure, using digital image processing techniques. The proposed experimental procedure can be used to a wide class of problems involving large deflections and deformations. The experimental buckling and post-buckling behavior compared favorably with the theoretical and numerical results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.353-358
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• 2018

In this study, it is describe to an optimization analysis process for the weight reduction of the voltage converter in the electric vehicle charging systems. The optimization design is a technique that finds the optimal material distribution under a given material quantity constraint by combining the design sensitivity with the material properties and the mathematical optimization. Among the topology optimization, a lightweight design is performed by a solid isotropic material with penalization with simple formula and well-convergence. The lightweight design consists of three steps. As a first step, a finite element model for the basic design of the on-board voltage converter was constructed and static analysis was performed on the load. In the second step, the optimum shape is obtained for the lightweight by performing the topology optimization using the solid isotropic material with penalization applying the stiffness coefficient of the isotropic material to the static analysis result. As a final step, impact analysis was performed by applying a half-sinusoidal pulse shape impact load which satisfies the impact test standard of the vehicle-mounted part with respect to the optimum shape. In the topology optimization, the design domain was defined as the mounting bracket area, and the design technology was finally achieved by optimizing the mounting bracket to achieve a weight reduction of 20% over the basic design.