• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.273-274
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• 2012

This paper investigates control algorithms for a doubly fed induction generator(DFIG) with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power system under unbalanced grid conditions. Two different control algorithms to compensate for unbalanced conditions are proposed. Evaluation factors of control algorithm are fault ride-through(FRT) capability, efficiency, harmonic distortions and torque pulsation. Zero regulated negative sequence stator current control algorithm has the most effective performance concerning FRT capability and efficiency. Ripple-free control algorithm nullifies oscillation component of active power and reactive power. Ripple-free control algorithm shows the least harmonic distortions and torque pulsation. Combination of zero regulated negative sequence stator current and ripple-free control algorithm control algorithm depending on the operating requirements and depth of grid unbalance presents the most optimized performance factors under the generalized unbalanced operating conditions leading to high performance DFIG wind turbine system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.207-208
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• 2012

최근 분산발전시스템에서 계통의 보호를 위해 계통전압 이상이 발생하더라도 일정시간 계통과의 연결을 강제하는 FRT기능이 요구되고 있으며 계통전압 불평형 시에도 계통과의 연결을 유지하도록 요구하고 있다. 이때 독립부하가 존재하는 경우 계통의 이상전압이 독립부하에 그대로 걸리게 되어 독립부하의 전압품질이 저하되는 문제가 있다. 본 논문에서는 계통전압 불평형시 FRT를 수행함과 동시에 독립부하에도 일정한 품질의 전압을 공급할 수 있는 전압보상 기법을 제안한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.215-216
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• 2008

• Physical Therapy Rehabilitation Science
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• 제6권3호
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• pp.140-145
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• 2017

Objective: The purpose of this study was to investigate the effect of visual block with ankle joint fatigue on gait and dynamic balance ability. Design: Cross-sectional study. Methods: Thirty healthy young adults (men=15, women=15) between 22 to 25 years of age voluntarily participated in this study. All subjects performed the gait and dynamic balance test successively in two conditions: the visual block and the open eyes condition. Before the gait and dynamic balance test, muscle fatigue on the ankle joint was induced to all subjects by doing ankle dorsiflexion and plantarflexion alternately, and then gait parameters (step length, stride length, cadence, velocity, single limb support, and double limb support) were assessed by walking on the GAITRite system (CIR Systems Inc., USA). Subjects also performed the functional reach test (FRT) for assessment of dynamic balance. This study examined gait parameters and FRT scores in each visual block and open eyes condition. Results: The results showed that FRT scores with the visual block condition significantly decreased compared to without visual blocking (p<0.01). Step length, stride length, cadence, and velocity of gait parameters decreased significantly in the visual block condition (p<0.01) while there was no significant difference for single limb support. However, double limb support increased significantly in the visual block system (p<0.01). Conclusions: Therefore, blocking of visual information with muscle fatigue of the ankle joint can affect gait and balance ability of young adults and increase the risk of falls.

• 대한물리의학회지
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• 제7권1호
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• pp.49-58
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• 2012

Purpose : The purpose of this study was to investigate the effects of trunk stabilization exercise using swiss ball and core stabilization exercise on balance and gait in elderly women. Methods : Subjects 19 elderly women were randomly divided by the swiss ball exercise group (n=10) and the core stabilization exercise group (n=9). In a period of 4 weeks, they took trunk stabilization exercise using swiss ball and core stabilization exercise for 60 minutes 3 times a week. Balance and gait were measured by Functional Reach Test (FRT), One Leg Stand Test with Open Eye (OLSTOE), One Leg Stand Test with Closed Eye (OLSTCE), Timed Up and Go Test (TUG) and 6 m Walking Test (6MWT). These tests were measured at before exercise, 4 weeks after exercise and after the follow-up period of 2 weeks. Results : As a result, in all measurement values there was no significant difference in two groups (p>.05). In FRT, TUG, OLSTOE and 6MWT before exercise and 4 weeks after exercise, there was significant difference in both of two groups (p<.05). Moreover, according to results from 4 weeks after exercise and after the follow-up period of 2 weeks, without any particular exercise, in FRT and 6MWT there was no significant difference (p>.05). Conclusion : These finding indicate that trunk stabilization exercise using swiss ball could improve balance and gait in elderly women. Accordingly, In this study trunk stabilization exercise using swiss ball and core stabilization exercise is judged to be used for elderly people with gait and balance problems to prevent hurts from fall.

• Physical Therapy Rehabilitation Science
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• 제4권2호
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• pp.66-72
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• 2015

Objective: The aim of this study was to investigate the effect of balance training with plantar flexor stretching on ankle dorsi flexion range of motion (ROM), balance, and gait ability in stroke patients. Design: A randomized controlled pilot trial. Methods: Thirty stroke patients volunteered to participate in this study. The subjects were randomly allocated to two groups: the experimental group (n=15) received the neurodevelopment therapy plus balance training with plantar flexor stretching for 20 minutes in one session. The control group (n=15) received the same neurodevelopment therapy plus plantar flexor static stretching for 20 minutes in one session. Both groups underwent sessions four times a week, for a total of 4 weeks. Measurements included passive range of motion (PROM), active range of motion (AROM) of ankle dorsiflexion using a goniometer, timed up and go (TUG), the functional reaching test (FRT), and the 10 m walk test (10 MWT). Results: There were significant improvements in AROM and PROM of ankle dorsiflexion, TUG, and FRT scores after the intervention in the experimental group (p<0.05). However, the control group showed no statistically significant differences except for PROM of ankle dorsiflexion. The experimental group showed a significant improvement in PROM, TUG, and FRT scores compared to the control group (p<0.05). Conclusions: Balance training with plantar flexor stretching improves ankle dorsiflexion ROM and balance ability in patients with stroke. Therefore, this therapeutic intervention will be effective for rehabilitation of stroke patients in the clinical setting.

• The Journal of Korean Physical Therapy
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• 제25권2호
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• pp.96-102
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• 2013

Purpose: The purpose of the study was to investigate the effect of a training program using virtual reality on the balance and lower muscular strength of Parkinson's disease patients. Methods: The study included 22 patients with Parkinson's disease who were arbitrarily classified into 2 groups: 11 patients in the experimental group and 11 patients in the control group. Balance was measured with the Berg balance scale (BBS), the functional reach test (FRT), one-leg stance test (OLST), and the timed up and go test (TUG); whereas, lower muscular strength was measured with the sit-to-stand test (STS). Ping-Pong, bowling, and tennis were selected for virtual reality training for the experimental group, and were performed for 30 minutes 3 times a week for 8 weeks. The control group did not undergo any of the virtual reality training programs. Results: A significant difference was observed in the BBS, FRT, OLST, TUG, and STS results within the experimental group that underwent the virtual reality training program. On the other hand, no significant difference was observed in the BBS, FRT, OLST, TUG, and STS values within the control groups. Conclusion: In conclusion, the virtual reality training program positively affects the balance and lower muscular strength in Parkinson's disease patients. This result indicates the possibility of application of the virtual reality training program to the management for Parkinson's disease patients, and highlights the need for the development and application of more efficient virtual reality training programs in the future.

• The Journal of Korean Physical Therapy
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• 제21권4호
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• pp.23-30
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• 2009

Purpose: This study investigated the efficacy of task-related circuit training aimed at improving balance in individuals discharged from rehabilitation facilities following a stroke. Methods: We recruited 12 stroke patients (34-66 years of age) to participate in a task-related circuit training program. Baseline assessment included a history of stroke and an assessment using the Mini-Mental State Examination Korea (MMSE-K). After a baseline assessment, follow-up assessments were administered pre- and post-training. These included Berg Balance Scale (BBS), Functional Reach Test (FRT), and the Time Up & Go Test (TUG). Physiotherapists trained study subjects under the one-to-one supervision of students from the department of physical therapy. Circuit class study participants attended 90-minute treatment sessions, one day a week for 12 weeks (from September to December 2008). The program consisted of a light warm-up period (10 min), physical exercises for improving balance (20 min), tasks focused on improving balance (50 min) and a cool-down period (10 min). Results: Scores for the BBS assessment increased significantly (from 43.2 to 49.7) after the training (p<0.05). Reach distance on the FRT increased substantially (from 27.7 cm to 47.0 cm), although the improvement was not significant (p>0.05). The average time on the TUG test decreased significantly (from 23.7 sec to 19.5 sec) after the training (p<0.05). Conclusion: The task-related circuit training program improved the balance and mobility of subjects, indicating that such a group program is useful for stroke patients who are discharged from the hospital. More such task-related programs set in a community environment should be developed.

• 대한물리의학회지
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• 제10권3호
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• pp.19-27
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• 2015

PURPOSE: This study aimed to investigate the effects of pressure sense perception training (PSPT) on various surfaces on the somatosensory system, balance, and walking ability in chronic stroke patients. METHODS: Thirty patients with stroke participated in this study and were randomly assigned to one of three groups; group 1 received the general physical therapy and the PSPT on a stable surface, group 2 received the general physical therapy and the PSPT on an unstable surface, and group 3 received the general physical therapy alone. Participants in group 1 and group 2 underwent 30 min/session, 3 days per week, for 4 weeks. Pressure error (PE) was used to evaluate changes of proprioception. The Balancia, Functional reach test (FRT), and Timed Up and Go (TUG) were used to assess the balance ability, and the 10m Walking Test (10-MWT) was used to assess walking ability. RESULTS: Experimental groups (group 1 and group 2) showed significant differences in PE, FRT, TUG, and 10-MWT compared to the control group (p <0.05). Group 2 (PSPT on an unstable surface) was significantly different in PE, FRT, and 10-MWT from group 1 (p <0.05). No significant differences were observed for other measures. CONCLUSION: Pressure sense perception training on an unstable surface might be a significantly more effective method for improving somatosensory function, balance, and walking ability, than PSPT on a stable surface.

• The Journal of Korean Physical Therapy
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• 제21권2호
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• pp.39-45
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• 2009

Purpose: The purpose of this study was to determine correlations between the Berg Balance Scale (BBS), Functional Reach Test (FRT), Timed Up & Go (TUG), Motor-Free Visual Perception Reach Test Vertical format (MVPT-V), Functional Independence Measure (FIM). Methods: The subjects used in this study were 35 stroke patients from Cheongju ST. Mary's hospital. Balance was measured by BBS, FRT. Functional mobility was measured by TUG. Visual perception was measured by MVPT-V. FIM was used to evaluate the activities of daily living. Data was analyzed using pearson product correlation. The TUG and MVPT-V index were analyzed by linear regression. Results: There was a statistically significant difference between FRT and BBS (r=0.89, p<0.01), FIM (r=0.74, p<0.05), MVPT-V (r=0.40, p<0.05), and TUG (r=-0.36, p<0.05). There was significant statistical differences between TUG and MVPT-V (r=-0.64, p<.01). However, statistically significant differences were observed between BBS and FIM (r=0.79, p<0.01). The visual close item of the MVPT-V showed the strongest variance in predicting TUG. Conclusion: The use of both quantitative and qualitive scales was shown to be a good measuring instrument for the classification of general clinical performances of stroke patients. In particular, the results suggest that the visual perception test may be able to predict functional locomotion in stroke patients.