• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.154-156
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• 2003

3상 4레그(leg) VSI(Voltage Source Inverter)는 독립된 3개의 출력전압을 합성할 수 있다. 따라서 전압 합성에 있어서 3개의 자유도를 갖는다. 본 논문에서는 3상 4레그 VSI를 위한 PWM방법에 대해서 설명한다. 3상 4레그 VSI를 위한 기존의 PWM기술은 3-D SVPWM으로 그 구현 방법에 있어서 많은 양의 계산과 테이블을 필요로 하였다. 하지만, 본 논문에서 제안 한 방법은 3상 3레그 VSI경우에 적용되었던 옵셋(offset) 전압의 개념을 사용한다. 또한 단일 반송파를 이용하여 폴(Pole)전압과 비교함으로써 PWM을 구현하기 때문에 그 적응이 매우 간단하다. 본 논문에서는 기존의 3-D SVPWM과 제안한 방법이 해석적으로 동일한 방법임을 증명하였으며, 3상 4레그 VSI에서 합성가능한 3자유도의 전압범위를 계산하였다. 마지막으로 이를 실험을 통하여 검증하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.7
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• pp.723-733
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• 1988

In this paper, A model of 4-legged walking robot is presented by investigating the gait of animals, which can walk with maintaining static stability on irregular terrain. Kinematices of the model robot was analyzed by geometric approach, and a gait control algorithm is proposed for the effective walking on irregular terrain. Terrains are classified into 4 types in order to study the terrain adaptability of the proposed algorithm and it is simulated for each type of terrain.

• Journal of Korean Orthopaedic Sports Medicine
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• v.4 no.2
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• pp.109-115
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• 2005

Purpose: The purpose of this study was to evaluate the effectiveness of three functional performance tests and one-legged hop test and to establish the reference data of the three functional performance tests of the active young Korean men. Materials and methods: We performed five tests on 40 normal subjects such as one-legged hop test (single hop, triple hop) and the three functional performance tests (carioca test, co-contraction test, shuttle run test). The mean age was 28.4 years. The mean score of Tegner activity scale was 6.2 and Lysholm score 98.2 Mean value and standard deviation were obtained. The correlation of age, height and weight with the results, the relationship between FPT and one-legged hop test and the mean difference between dominant and non-dominant limbs were statistically calculated. Results: All data obtained were normally distributed and there were no significant relationship between age, height and weight. The paired t-test of one legged hop test showed no statistical significance between dominant and non-dominant limbs. The results of one legged hop test had strong relationship with functional performance test. Conclusion; The three functional performance tests can be a useful functional test in ACL-insufficient athletes. Our results can be used as normal reference data of the normal active Korean men.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.175-182
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• 2015

Objective : The purpose of this study was to investigate difference in fascicle behavior of the medial gastrocnemius during the locomotion with varying intensities, such as gait and one-legged and two-legged vertical jumping. Methods : Six subjects (3 males and 3 females; age: $27.2{\pm}1.6yrs.$, body mass: $62.8{\pm}9.8kg$, height: $169.6{\pm}8.5cm$) performed normal gait (G) at preferred speed and maximum vertical jumping with one (OJ) and two (TJ) legs. While subjects were performing the given tasks, the hip, knee and ankle joint motion and ground reaction force was monitored using a 8-infrared camera motion analysis system with two forceplates. Simultaneously, electromyography of the triceps surae muscles, and the fascicle length of the medial gastrocnemius were recorded using a real-time ultrasound imaging machine. Results : Comparing to gait, the kinematic and kinetic parameters of TJ and OJ were found to be significantly different. Along with those parameters, change in the medial gastrocnemius (MG) muscle-tendon complex (MTC) length ($50.57{\pm}6.20mm$ for TJ and $44.14{\pm}5.39mm$ for OJ) and changes in the fascicle length of the MG ($18.97{\pm}3.58mm$ for TJ and $20.31{\pm}4.59mm$ for OJ) were observed. Although the total excursion of the MTC and the MG fascicle length during the two types of jump were not significantly different, however the pattern of length changes were found to be different. For TJ, the fascicle length maintained isometric longer during the propulsive phase than OJ. Conclusion : One-legged and two-legged vertical jumping use different muscle-tendon interaction strategies.

• Proceedings of the KOR-KST Conference
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• 2007.05a
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• pp.247-256
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• 2007

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.498-500
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• 2016

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.645-650
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• 2003

Legged robots can avoid an obstacle by crawling-over or striding, according to the obstacle’s nature and the current state of the robot. Thus, it can be observed that the mobility efficiency to reach a destination is improved by such action. Moreover, if robots have many legs like 4-legged or 6-legged types, then the robot movement range is affected by the order of swing leg. In this paper, the avoidance action of a quadruped robot is generated by a neural network (NN) whose inputs are information on the position of the destination, the obstacle configuration and the robot's self-state. To realize a free gait in static walking, the order of swing leg is determined using an another NN whose inputs are the amount of movements and the robot’s self-state. The design parameter of the latter NN is adjusted by using genetic algorithm (GA).

• Journal of the Korean Society of Physical Medicine
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• v.12 no.3
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• pp.67-71
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• 2017

PURPOSE: Muscle fatigue is a cause to change proprioception. The purpose of this study was to investigate the effects of calf muscle fatigue and visual control on postural balance during single-legged standing in healthy adults. METHODS: Nineteen healthy adults (male) were participated in this study (mean age: 24.36 years; mean height: 171.32 cm; mean weight: 64.58 kg). The postural balance (sway length, sway area, sway velocity of COG displacement) was measured by Balance Trainer System (BT4) in before and after calf muscle fatigue feeling in single legged stance. In this study, repetitive single-legged heel rise test was used to induce fatigue of the calf muscle. Paired t- test was used to compare the postural balance between before and after calf muscle fatigue. Data of subjects were analyzed using SPSS 22.0 (SPSS Inc., Chicago, IL, USA). Level of significance was set to .05. RESULTS: The sway length, sway area, sway velocity of COG (center of gravity) displacement after calf muscle fatigue feeling was significantly increased compared to before calf muscle fatigue feeling during single leg standing both eye open and close conditions (p<.05). CONCLUSION: This study suggested that calf muscle fatigue feeling has affected on postural balance when standing one leg both eye open and close conditions and postural control was disturbed by muscle fatigue and visual feedback in single leg standing.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.121-131
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• 2014

PURPOSES : The goal of this study is to analyze the travel cost according to transferring from rotary to roundabout in Korea. METHODS : This study gives particular attentions to investigating the existing 48 rotaries in Korea and building the networks of before and after improvements using VISSIM, and analyzing their travel costs. RESULTS : The main results are as follows. First, from the field survey, the domestic rotaries were analyzed to need many improvements of geometric structure for the effective operation. Second, the difference of travel cost at 3-legged rotaries were evaluated to be less than other types of rotaries due to low traffic volume. Finally, the travel cost of 4-legged and multi-legged rotaries were analyzed to rapidly increase by increasing volume. CONCLUSIONS : This study analyzes the effects using both real and simulation data unlike the existing studies. Also, this study suggests the future research topics which compare and evaluate the relations between real data and simulation outputs.

• Physical Therapy Rehabilitation Science
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• v.5 no.2
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• pp.70-77
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• 2016

Objective: The purpose of this study was to compare the activation of trunk and gluteal muscles during bridge exercises with a sling (BS), single-legged bridge exercise with a sling (SBS), single-legged bridge exercise (SB), and general bridge exercise (GB). Design: Cross-sectional study. Methods: Twenty-five healthy participants (19 males and 6 females, aged 27.8 [4.78]) voluntarily participated in this study. In the bridging exercise, each subject lifted their pelvis with their legs and feet in contact with the sling or normal surface. The electrical activities of the erector spinae (ES), gluteus maximus (GM), external oblique (EO), and internal oblique (IO) muscles during the bridging exercises on the 2 surfaces were measured using surface electromyography. Subjects practiced each of the four bridge condition three times in random order and average values were obtained. Results: On the ipsilateral side, activities of the IO, EO, and ES during SBS was significantly higher than those during BS, SB, and GB (p<0.05). Activities of the IO and EO during SB was significantly higher than those during BS and GB (p<0.05). On the contralateral side, activities of the GM and EO during SB and SBS was significantly higher than that during BS and GB (p<0.05). These results verify the theory that the use of sling and single leg lift increases the activation trunk and gluteal muscles during bridging exercises. Conclusions: The single-legged bridge exercise with a sling can be recommended as an effective method to facilitate trunk and gluteal muscle activities.