• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.42-47
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• 2014

The role of Electrical Power Subsystem (EPS) is to generate a power and distribute it to the electrical devices for the system operation. For on-orbit operation of cube satellite, it is also necessary to supply power to on-board mission devices as commercial satellite does. Recently, commercial EPS products dedicated for the cube satellite application has been developed and widely used for the power subsystem design. In this paper, a permanent magnet attitude stabilization method without external power has been introduced because it has advantage from power consumption point of view and the EPS design of cube satellite by applying the commercial EPS products has been introduced and investigated. This paper also deals with the specification of the commercial EPS products for the beginner of the cube satellite design.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.287-289
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• 2009

This paper deals with a parallel processing uninterruptible power supply (UPS) for sudden voltage fluctuation in computer applications to integrate power quality improvement, load voltage stabilization and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, only one voltage-controlled voltage source inverter (VCVSI) is used. The system provides sinusoidal voltage at the fundamental value of 220V/60Hz for the load during abnormal utility power conditions or grid failure. Also, the system can be operated to mitigate the harmonic current and voltage demand from nonlinear loads and provide voltage stabilization for loads when sudden voltage fluctuation occur, such as sag and swell. System operation simulation demonstrates that the system protects against outages caused by abnormal utility power conditions and sudden voltage fluctuations and changes.

• Journal of Power Electronics
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• v.18 no.2
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• pp.547-557
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• 2018

This work proposes a control method of frequency stabilization for grid integration of large-scale wind farms via the voltage source converter-based high-voltage direct current (VSC-HVDC) technology. First, the topology of grid integration of a large-scale wind farm via the VSC-HVDC link is provided, and simple control strategies for wind turbines, wind farm side VSC (WFVSC), and grid side VSC are presented. Second, a mathematical model between the phase angle of WFVSC and the frequency of the wind farm is established. The control principle of the large-scale wind power integrated system is analyzed in theory in accordance with the mathematical model. Third, frequency and AC voltage controllers of WFVSC are designed based on the mathematical model of the relationships between the phase angle of WFVSC and the frequency of the wind farm, and between the modulation index of WFVSC and the voltage of the wind farm. Corresponding controller structures are established by deriving a transfer function, and an optimization method for selecting the parameters of the frequency controller is presented. Finally, a case study is performed under different operating conditions by using the DIgSILENT/PowerFactory software. Results show that the proposed control method has good performance in the frequency stabilization of the large-scale wind power integrated system via the VSC-HVDC technology.

• The Journal of Korean Physical Therapy
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• v.32 no.1
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• pp.14-20
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• 2020

Purpose: This study examined the effects of early stabilization exercise focused on the scapulothoracic joint on the recovery of surgical patients due to rotator cuff tear. Methods: The subjects were 30 patients divided randomly into two groups. Group I consisted of 15 patients who practiced shoulder joint stabilization exercises, including glenohumeral joint movement. Group II consisted of 15 patients who practiced scapulothoracic joint stabilization exercises, excluding glenohumeral joint movement. The duration of stabilization exercise was 30 minutes for one day, five days a week, and five weeks. To measure the dependent variables, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, range of motion (ROM), dynamometer of measured grip were used. Results: The DASH, ROM, and grip power were compared. A significant difference was observed before the intervention in each group (p<.05), and there was no significant difference between group I and group II (p>.05). Conclusion: Both shoulder joint and scapulothoracic joint stabilization exercises were effective after the intervention compared to preintervention, but there was no difference between the two groups. Unlike many recent studies on the initiation of stabilization exercises, this study allays the concerns between the advantages of 'early exercise' and oppositions of previous studies about 'early exercise'. Nevertheless, further research regarding these subjects is needed.

• The Journal of Korean Physical Therapy
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• v.18 no.5
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• pp.25-34
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• 2006

Purpose: This study is intended to evaluate the effects of lumbar stability after 3-dimensional exercises of lumbar stabilization. Methods: Total subjects with chronic low back pain(age ranged from 20 to 60) were recruited. All subjects received 3-dimensional exercise of trunk stabilization during 4 weeks in 00 orthopedic clinic, from May 15 to October 15 in 2006. All measurements of each patients were measured before and after lumbar stabilization exercise. Results: After lumbar stabilization exercise by CENTAUR(R), the muscle power was increased from 57.99kNm to 72.01kNm, there were statistically remarkable differences(p<0.05). VAS was lessened from 6.35 to 3.26, there were statistically remarkable differences(p<0.05). After lumbar stabilization exercise by CENTAUR(R), the temperature was increased from $27.68^{\circ}C$ to $28.26^{\circ}C$, there were remarkable differences statistically(p<0.05). Conclusions: It has been turned out that lumbar stabilization exercise has positive effect on the muscle strengthening, pain index and thermal change.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.2
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• pp.63-71
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• 2015

PURPOSE: The purpose of this study to investigate the effects of exercise on lumbar stabilization in muscle activity and isokinetic muscle strength of female with chronic low back pain. METHODS: The candidates was chose to twenty women in their 30s and 40s complaining back pain for over 12 weeks and consist of 10 people for lumbar stabilization and general physical therapy group(PL group), another 10 people for general physical therapy group(GP group). Lumbar stabilization exercise was conducted for 8 weeks and was comprised of 60 minutes for two times a week. In order to examine the effects of lumbar stabilization, results in the present study were analyzed maximal voluntary isometric contraction (MVIC) using electromyogram to measure muscle activity and isokinetic performance including peak torque and average power at the pre to post. RESULTS: The following are results in this study. The MVIC and isokinetic muscle strength were gradually increased in all group. As the result of the test of the MVIC and isokinetic muscle strength, the difference of lumbar stabilization and general physical therapy group is statistically more significant than that of general physical therapy group. CONCLUSION: In the present study, results indicate that lumbar stabilization helps to improve the muscle activity and isokinetic muscle strength.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.66-73
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• 2005

Hydrogen linear power system is estimated as the next generation power system which can obtain a performance as same as fuel cell. In order to develop Hydrogen combustion power system with high thermal efficiency, it is very important to understand the basic characteristics of hydrogen combustion and establish combustion stabilization technique of its system. In this study, RICEM(Rapid Intake Compression Expansion Machine) for researching of hydrogen combustion linear power system was manufactured and evaluated, and the basic characteristics of linear RICEM were analyzed.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.672-674
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• 2004

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.224-226
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• 2000

In this paper, a robust $H_{\infty}$ controller, based on the Riccati equation approach, is proposed for HVDC power system with parametric uncertainties. Bounds of power system parametric uncertainties are included in Riccati equation to improve the robustness of controller. The proposed $H_{\infty}$ controller for the stabilization of HVDC power system can ensure that the overall system is asymptotically stable for all admissible uncertainties. Simulation results show that the proposed $H_{\infty}$ controller can achieve good performance in presence of uncertainties of power system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.254-259
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• 2014

In this paper, we describe construction of a wind stabilization demo-site and effects of output power control of wind turbines for suppression of ramp rate using ESS (Energy Storage System). It is difficult to control the output power of distributed generator such as wind turbine which of variation is very large. If the large capacity wind farm be interconnected into power system may cause blackout due to Power Quality. For these reasons, the international standards such as Grid-Code is limited to less than 10 [%/min] of renewable energy ramp rate. The case of Korea, government actively conducts propagating large-scale renewable energy for green growth policy, to interconnecting more renewable energy into power system is necessary for stabilization technology. For these reasons, the POSCO consortium has constructed a wind stabilization demo-site that is configured as 500 [kWh] battery energy storage systems can output up to 3 [C-Rate] and two wind turbines rated 750 [kW]. In POSCO consortium, which implements various methods stabilizing output power of wind turbine such as smoothing, section firming and ramp control, we derive the results of long-term demonstration that can be controlled to satisfy to the international standard about ramp rate [%/kW] of wind turbine output power.