• Journal of Power Electronics
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• 제16권5호
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• pp.1928-1938
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• 2016

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.

• The Journal of Korean Physical Therapy
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• 제27권2호
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• pp.124-127
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• 2015

Purpose: The emphasis on gait rehabilitation after stroke depends on training support through the lower limbs, balance of body mass over the changing base of support. However, muscle weakness, lack of control of lower limb, and poor balance can interfere with training after stroke. For this case study report, a wearable robot orthosis was applied to stroke patients in order to verify its actual applicability on balance and gait ability in the clinical field. Methods: Two stroke patients participated in the training using the wearable robot orthosis. Wearable robot orthosis provides patient-initiated active assistance contraction during training. Training includes weight shift training, standing up and sitting down, ground walking, and stair up and down Training was applied a total of 20 times, five times a week for 4 weeks, for 30 minutes a day. Gait ability was determined by Stance phase symmetry profile, Swing phase symmetry profile, and velocity using the GAITRite system. Balance ability was measured using the Biodex balance system. Results: Subjects 1, 2 showed improved gait and balance ability with mean individual improvement of 72.4% for velocity, 19.4% for stance phase symmetry profile, 9.6% for swing phase symmetry profile, and 13.6% for balance ability. Conclusion: Training utilizing a wearable robot orthosis can be useful for improvement of the gait and balance ability of stroke patients.

• The Journal of Korean Physical Therapy
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• 제23권3호
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• pp.1-5
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• 2011

Purpose: This study examined the relationship between the center of pressure (COP) displacement time during the stance phase and dynamic balance ability when older adults cross a 10 cm obstacle. Methods: Fifteen older adults were enrolled in this study (all ${\geq}65$ years of age). The F-scan was used to measure the COP displacement time when subjects cross a 10 cm obstacle, and the Dynamic gait index. Berg's balance scale and the Four square step test were used to measure dynamic balance ability. Results: The Dynamic gait index, Berg's balance scale and the Four square step test were correlated with each other. Dynamic balance ability was correlated with COP displacement time during the stance phase at an obstacle crossing in older adults. Conclusion: People with higher dynamic balance ability show a smaller COP displacement time during the stance phase at an obstacle crossing. Therefore, dynamic balance ability can be predicted by measuring the center of pressure displacement time.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.175-178
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• 2006

We present a ring hybrid balun with additional two ${\lambda}/4$ short stubs that offers excellent amplitude and phase balance performance. The phase difference which is essentially occurred in $180^{\circ}$ ring hybrid is compensated by a ${\lambda}/4$ short stub in one output port. To compensate the amplitude imbalance inherent in the ring hybrid, the series resistance will be added to the second stub which is connected to another output port. The measured balun shows that phase imbalance is less than $2.5^{\circ}$ and magnitude imbalance is less than 0.2dB over a 1.75-2.25 GHz.

• 성인간호학회지
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• 제16권3호
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• pp.493-501
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• 2004

Purpose: The purpose of this study was 1) to classify the stage of adoption 2) to compare the decisional balance and confidence by stage of adoption 3) to identify factors influenced the stage of adoption for breast self exam. Method: A comparative study using a survey method with convenience sample of 143 women was used. Decisional balance and confidence was measured using the CHBMS-K. Stage of adoption for BSE was measured by a single item modified by the researchers based on the Rakowski et al (1992). Result: 1) The number of women in each stage of adoption for BSE was as follows; maintenance phase, 7.7% (n=11), action phase, 49.0% (n=70), contemplation phase, 35.0% (n=50) and pre- contemplation phase, 8.4%(n=12). 2) The mean difference in the decisional balance (F=4.32, p=.006) and confidence (F=13.85, p=.000) according to the stage of BSE adoption was statistically significant. 3) Prevention education and confidence accounted for 32% of variance in BSE. Conclusion: Assessment of decisional balance and stage of adoption for BSE can guide planning for cancer prevention education. We must educate women to have confidence in BSE. Further, it is important to urge women to continually practice BSE.

• PNF and Movement
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• 제21권1호
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• pp.11-18
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• 2023

Purpose: This study aims to compare the effects of obstacle walking training combined with cognitive tasks on balance, gait, and activities of daily living in patients with stroke. Methods: A single-subject design was used, where one stroke patient participated. Obstacle walking training combined with cognitive tasks was performed for 1 hour per day for a total of 10 times during the intervention phase. The subjects were measured five times in the baseline phase, 10 times in the intervention phase, and five times in the follow-up phase. The outcome measurements included the Berg balance scale (BBS), the 10-meter walk test (10 MWT), and the Korean modified Barthel index (K-MBI). Results: In this study, the results showed that the 10 MWT scores during the intervention period improved and that this improvement remained, even during the post-period. In addition, BBS and K-MBI values for stroke patients increased significantly after training. Conclusion: The results of this study revealed that obstacle walking training combined with cognitive task training may be helpful to improve balance, gait, and activities of daily living in stroke patients. Therefore, obstacle walking training combined with cognitive tasks is recommended for stroke patients.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.217-222
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• 2006

A distributed balun such as Marchand balun typically shows good phase and amplitude balances, but its size is somewhat large especially in lower frequency band. In contrast, a lumped balun has compact size but its performance is not good compared with that of a distributed one. In this paper the distributed-coupled line can be reduced effectively by using the lumped-distributed implementation. Designed balun has two coupled line of each ${\lambda}/72$ and shows magnitude balance of 0.05 dB, phase balance of $0.7^{\circ}$ in passband. Balanced-type filter is designed using balun and it has insertion loss of 8 dB, return loss of 7 dB, magnitude balance of 0.2 dB, and phase balance of $1.2^{\circ}$ in passband.

• 한국엔터테인먼트산업학회논문지
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• 제14권6호
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• pp.221-230
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• 2020

본 연구는 진동자극 저항운동이 허리통증 경험자의 균형 및 보행에 미치는 영향을 연구하였다. 30명의 히리통증 경험이 있는 성인 대학생을 대상으로 8 Hz 진동자극 저항운동(n=10), 30 Hz 진동자극 저항운동(n=10), 허리 안정화운동(n=10)으로 무작위로 나누었다. 각 그룹의 중재는 6주동안 주 3회, 1회에 30분을 적용하였다. 실험 전에 정적균형과 보행패턴을 측정하였고, 6주 후에 실험전과 동일한 방법으로 측정하였다. 연구결과 세 그룹 모두에서 운동전과 후의 시간에 따른 정적균형, 디딤기율, 흔듦기율, 한걸음 길이, 한발짝률의 변화는 통계적으로 유의한 차이가 있었다(p<.05). 허리 안정화운동이 정적균형과 디딤기율에서는 그룹 간의 유의한 차이가 있었고(p<.05), 흔듦기율 및 한걸음 길이와 한발짝률은 그룹 간의 차이가 없었다. 결론적으로 진동자극 저항운동이 근수축 유발 기전에 의해 다리근육의 근력을 강화하였고, 강화된 다리 근력은 균형능력에 긍정적인 영향을 미쳤으며, 향상된 균형능력은 신체가 움직이는 동안 안정적으로 자세를 조절할 수 있게 하여 보행능력의 긍정적 측면에 영향을 미친 것으로 판단된다.

• 한국운동역학회지
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• 제32권1호
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• pp.24-30
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• 2022

Objective: The purpose of this study was to determine the factors of successful and unsuccessful movements through the analysis of kinematics and muscle activity of the Free Aerial Cartwheel on the balance beam. Method: Subjects (Age: 22.8 ± 2.4 yrs., Height: 158.7 ± 5.0 cm, Body mass: 54.1 ± 6.4 kg, Career: 13 ± 2.4 yrs.) who were currently active as female gymnasts participated in the study. They had no history of surgical treatment within 3 months. Subject criteria included more than 10 years of professional experience in college and professional level of gymnastics and the ability to conduct the Free Aerial Cartwheel on the Balance Beam. Each subject performed 10 times of Free Aerial Cartwheel on the balance beam. One successful trial and one unsuccessful trial (failure) among 10 trials were selected for the comparison. Results: It was found that longer time required in case of unsuccessful trial when performing the Free Aerial Cartwheel on the balance beam compared with successful trial. It is expected to be the result of movement in the last landing section (i.e. phase 5). In addition, it was found that the center of gravity of the body descends at a high speed to perform the jump (i.e. phase 2) in order to obtain a sufficient jumping height when the movement is successful while the knee joint is rapidly extended to perform a jump when movement fails. In the single landing section after the jump (i.e. phase 4), if the ankle joint rapidly dorsiflexed after take-off and the hip joint rapidly flexed, so landing was not successful. Conversely, in a successful landing movement, muscle activity of the biceps femoris was greatly activated resulting no shaking in the last landing section (i.e. phase 5). Conclusion: In order to succeed in this movement, it is necessary to perform a strong jump after rapidly descending the center of gravity of the body using the force of the biceps femoris muscle. Further improvement of the skills on the balance beam requires the analysis of the game-like situation with continuous research on kinematic and kinematic analysis of various techniques, jumps, turns, etc.

• 한국전문물리치료학회지
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• 제8권1호
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• pp.9-19
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• 2001

During therapy sessions, feedback is often provided concurrently by the physical therapist as the patient attempts to perform a movement and after the movement attempt. This feedback is provided to enhance the patient's balance abilities. However, recent studies in nondisabled populations have suggested that frequent feedback may be detrimental to retention or learning of motor skills. This study compared the effects of 100% relative frequency of knowledge of performance (KP) with 66% relative frequency of KP for motor learning on balance retraining in patients with hemiplegia. Twenty patients with hemiplegic were randomly assigned to one of two experimental groups. The acquisition phase consisted of 16 blocks of 5 trials for 2 days (80 total practice trials). The retention phase consisted of 2 blocks of a short-term retention test, one day after the end of the acquisition phase and a long-term retention test, one week after the end of the short-term retention test. In the 100% feedback condition, participants received feedback after every practice trial. A faded KP schedule was used in the 66% condition. No significant differences were found between the two groups during all experimental phases (acquisition and retention phases), (p>.05). However, there were significant decreases in balance index for both groups of acquisition phase (p<.05). These results suggest that 66% relative frequency of KP is not more effective than 100% relative frequency of KP with respect to retention over time when hemiparetic patients attempt to learn balance.