• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.57-65
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• 2015

PURPOSE: The purpose of this study was to investigate the effect of balance training on different support surface (affected and non-affected sides) on the balance and gait function of chronic stroke patients. METHODS: The patients were randomly assigned to 1 of 4 groups. Group 1 received balance training on the stable surface, group 2 received balance training on the unstable surface, group 3 received balance training on different support surface (affected side: stable surface, non-affected side: unstable surface), and group 4 received balance training on different support surface (affected side: unstable, non-affected side: stable). Twelve sessions (30 min/d, 3 times/wk for 4 wk) were applied. There were assessed before and after the intervention with Balancia, functional reach test (FRT), lateral reach test (LRT), timed up-and-go (TUG), and 10-meter walking test (10MWT). RESULTS: After the training, all of the groups improved significantly than before training in Balancia, FRT, LRT, TUG, and 10MWT. There were significantly variable in sway distance, FRT, LRT, TUG, and 10MWT among the 4 groups. Post hoc analysis revealed that the group 3 had significantly higher results than other 3 groups in sway distance, and FRT, LRT, TUG, and 10MWT. CONCLUSION: Balance training on different support surface (affected side: stable surface, non-affected side: unstable surface) could facilitate a stronger beneficial effect on balance and walking ability than other balance trainings on different support surface in patients with stroke.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.15 no.1
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• pp.58-63
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• 2009

Purpose: The purpose of this study is to figure out that the scapular stability exercise on unstable position can effect on the pain relief of the patient with lateral epicondylitis. Methods: The subject was 35 year old male, diagnosed as lateral epicondylitis. This patient was controled to do scapular stability exercise with crawling position on unstable surface, changing elbow movement from flexion to extension for 4 weeks, 5 times a week, 20 times in total. We used VAS to find the degree of pain and Cozen's test, Mill's test and Resisted middle finger test were determined for the measurement of epicondylitis changed. Results: The following is the result of this study. 1. Pain on lateral epicondylitis was relived from VAS 7 to VAS 0. 2. There were improvements that the results of tests for epicondylitis, Cozen's test, Mill's test and Resisted middle finger test, changed positive into negative signs. Conclusion: The result of this study indicates that the application scapular stability exercise on the unstable surface to the patient with lateral epicondylitis can relief the pain degree on the lateral epicondylitis and be used as one of lateral epicondylitis treatments.

• Tribology and Lubricants
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• v.31 no.6
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• pp.302-307
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• 2015

The use of turbocharger in internal combustion engines has increased as it is a key components for improving system efficiency without increasing engine size. Because of increasing demand, many studies have evaluated rotordynamic performance so as to increase rotation speed. This paper presents a linear and nonlinear analysis model for a turbocharger rotor supported by a floating ring bearing. We constructed rotor model by using the finite element method and approximated bearings as being infinitely short. In the linear model, we considered fluid film force as stiffness and damping element. In nonlinear analysis, calculation of the fluid film force involved solving the time dependent Reynolds equation. We verified the developed model by comparing the results to those of previous research. The analysis results show that there are four unstable modes, which are rigid body modes combining ring and rotor motion. As the rotating speed increases, the logarithmic decrement shows that certain unstable modes goes into the stable area or the stable mode goes into the unstable area. These unstable modes appear as sub-synchronous vibrations in nonlinear analysis. In nonlinear analysis frequency jump phenomenon demonstrated in several experimental studies appears. The analysis results also showed that frequency jump phenomenon occurs when the vibration mode changes and the sequence of unstable mode matches the linear analysis result. However, the natural frequency predicted using linear analysis differs from those obtained using nonlinear analysis.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.1
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• pp.85-92
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• 2022

PURPOSE: This study aimed to analyze the effects of task exercise on an unstable surface on the involuntary arm and leg movement and balance in stroke patients. METHODS: 20 stroke patients were clinically sampled and randomly assigned to two groups of 10 patients each. Experimental group I received task exercise intervention on an unstable surface and experimental group II received task exercise intervention. The interventions were carried out 3 times a week for 4 weeks (30 minutes per session). The global synkinesis (GS) and Berg Balance Scale (BBS) of the patients were evaluated as pre-tests prior to intervention, and then the post-tests were re-measured in the same manner as the pre-tests after a 4-week intervention period. RESULTS: In the experimental group I, there were statistically significant differences in the changes in the arm and leg GS (p < .01) and in the BBS (p < .05). On the other hand, in the experimental group II, there were statistically significant differences in the changes only in the arm GS (p < .01) and in the BBS (p < .05). Also, in the comparison of the changes between the two groups, there was a statistically significant difference in the changes in the leg GS only (p < .05). CONCLUSION: In the experimental group I, the arm and leg GS were statistically significantly reduced, but the balance ability was statistically significantly improved. The reason was that in the experimental group I, similar movements of the paralyzed arm were promoted due to the double-task exercise on the unstable surface, and sensory feedback and posture strategies were well utilized in the legs, which was found to be effective in reducing the GS and improving the balance ability. Therefore, based on these results, the double-task exercise on an unstable surface should be fully utilized for the rapid rehabilitation of stroke patients.

• Journal of Korean Physical Therapy Science
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• v.28 no.3
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• pp.88-97
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• 2021

Purpose: Patients with total knee arthroplasty (TKA) have impaired balance and movement control. Exercise interventions have not targeted these impairments in this population. This study aimed to investigate the effect of complex balance exercises on unstable ground, on the gait, balance, and daily living ability of patients with total knee arthroplasty. Design: Randomized controlled trial. Methods: The participants consisted of 30 patients placed into two groups of 15 each: a experimental group (complex balance exercise) and a control group (physical therapy exercise). Both group exercise was applied for 3 times a week for 30 minutes for four weeks. Force plate for balance ability and Timed up and go (TUG) test were the primary outcome measures. The secondary outcome measures included 10-m walk test (10MWT) and the daily living ability using the Knee Outcome Survey Activities of Daily Living scale (KOS-ADL). Results: The result of this study showed that the experimental group had a significant difference in TUG and 10MWT than the control group, and balance was significantly different in CEA, CPL, and CAV. There was a significant difference in daily living ability between the experimental and control groups. This study confirms that the physical therapy with complex balance exercise on unstable surfaces has positive effects on balance, gait and daily living ability in patients with total knee arthroplasty. Conclusion: As a result of this study, complex balance exercise on unstable surface was more effective in improvement gait, balance and daily living ability in total knee arthroplasty. From this study, physical therapy with complex balance exercises on unstable ground may be proposed as and effective intervention method for improving gait, balance, and daily living ability in patients with early total knee arthroplasty.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.2
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• pp.75-82
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• 2022

PURPOSE: This study examined the correlation between the pulmonary function and respiratory muscle strengthening training on an unstable support surface and a stable support surface in stroke patients. METHODS: The study subjects were 22 stroke patients undergoing central nervous system developmental rehabilitation treatment. After excluding six dropouts, eight people in the experimental group and eight people in the control groups were classified by random sampling. Both groups performed central nervous system developmental rehabilitation therapy and were provided a 10-minute break. The experimental group was provided with an unstable support surface using Togu, and the control group was trained to strengthen the respiratory muscle in a stable support surface. Respiratory muscle strengthening training was conducted three times per week for 20 minutes. Before and after each group of experiments, a nonparametric test Wilcoxon signed rank test, and a Mann Whitney U-test analysis were used to analyze the variations between the two groups. All statistical significance levels (α) were set at 0.05. RESULTS: Both groups showed increases in the pulmonary function but showed significant differences only in the experimental group. There was a significant difference in the peak expiratory flow between the two groups. CONCLUSION: Central nervous system development rehabilitation treatment for patients with an impaired nervous system and respiratory muscle strengthening training on unstable support surfaces are effective in improving the pulmonary function of stroke patients. Therefore, they are expected to be applied to physical therapy programs to help various functional activities.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.97-106
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• 2004

Stability of laminar premixed planar flames inclined in gravitational field which generate vorticity is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results show that as the flame is more inclined from the horizontal plane it becomes more unstable due to not only the decrease of stabilizing effect of gravity but also the increase of destabilizing effect of rotational flow. The obtained dispersion relation involves the Prandtl number and shows the destabilizing effect of viscosity. The analysis predicts that the phase velocity of unstable flame wave depends on not only the flame angle but also the Lewis number. For relatively short wave disturbances, still much larger than flame thickness, the most unstable wavelength is nearly independent on the flame angle and the flame can be stabilized by gravity and diffusion mechanism.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1864-1866
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• 1997

Uncertainties in the aerodynamic coefficients or time delay effects in implementing an autopilot algorithm can make a Flight Control System(FCS) unstable. When a FCS enters unstable state, the actuator or sensor limiters in FCS make the unstable system not diverge but be in the state of stable limit cycle. If an autopilot recognize the FCS to be in the stable limit cycle phenomenon, it woudl be better to adjust autopilot gains to stabilize the FCS. A novel method to stabilize a FCS using parameter estimation and maintenance of given phase margin is proposed. The method is applied to roll control loop and verified its performance.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.72-78
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• 2012

In this research an equilibrium point of a Wheeled Inverted Pendulum (WIP) running on an inclined road is derived and validated by some experiments. Generally, The WIP has stable and unstable equilibrium point. Only unstable equilibrium point is interested in the research. To keep the WIP on the unstable equilibrium point, the WIP is consistently controlled. A controller for the WIP needs a reference state for the equilibrium point. The reference state can be obtained by studying an equilibrium point of the WIP. This research is deriving dynamic equations of the WIP running on the inclined road and equilibrium of it based on statics. Several experiments are carried out to show the validation of the equilibrium point.

• Journal of the Korean Society of Combustion
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• v.9 no.4
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• pp.9-21
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• 2004

Stability of laminar premixed planar flames inclined in the gravitational field is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results show that as the flame is more inclined from the horizontal plane it becomes more unstable due to not only the decrease of stabilizing effect of gravity but also the increase of destabilizing effect of rotational flow. The obtained dispersion relation involves the Prandtl number and shows the destabilizing effect of viscosity. The analysis predicts that the phase velocity of unstable flame wave depends on not only the flame angle but also the Lewis number. For relatively short wave disturbances, still much larger than flame thickness, the most unstable wavelength is nearly independent on the flame angle and the flame can be stabilized by gravity and diffusion mechanism.