• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.353-360
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• 1999

The global balance model is applied to investigate the transient behavior of the electron density and temperature in helicon plasmas. The power absorption calculated from the solutions of the Maxwell equations is used in solving the power balance equation. A balance model for the neutral gas is also considered to fins its density self-consistently. It is turned out that the numerical results reasonably explain consequences of the ion pumping effect including the occurrence of two distinct modes of pulsed helicon discharge which have been observed experimentally. The behavior of the discharge parameters are fond to be primarily dependent on the power absorption and the gas flow rate, but the pressure controls the electron density and temperature of the final steady state as well as the transient state even with the same flow rate. Finally, it is shown that the electron density virtually the linear relationship between the density and the magnetic field is retained for a higher pressure when the effect of the ion pumping is negligible.

• Journal of electromagnetic engineering and science
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• v.13 no.3
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• pp.192-194
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• 2013

This paper proposes a validation model using a reverberation chamber for verification of the effectiveness and accuracy of the statistical power balance (PWB) method. The PWB method treats electromagnetic (EM) field distributions in certain environments as a representative value of an "ensemble" average, so a reverberation chamber is utilized as a testing apparatus to experimentally simulate the sets of measurement field "ensemble" inside a complex environment. Measurements are performed with various test conditions for environmental loss using flat absorbers, and front and side doors of the chamber. Comparison between the PWB analysis and the measurement results shows good agreement, indicating the usefulness of this statistical analysis method for stating the electromagnetic field inside the EM zone as a representative value to general structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.451-460
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• 2001

An analysis program for the thermal performance prediction of steam turbine cogeneration systems with multi-extraction, reheat and regeneration has been developed on the basis of the thermodynamic heat balance method. Heat balance analyses were performed for a commercial cogeneration power plant using the program. Its appropriateness was verified by comparing its heat balance results with those of other commercial programs and those provided by the original system designer. Further parametric analyses were carried out and performance improvement measures in designing the plant were suggested.

• Nuclear Engineering and Technology
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• v.37 no.2
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• pp.167-176
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• 2005

We developed the PERUPS system to aid the on-line performance analysis for the turbine cycle of the YongGwang 3 and 4 nuclear power plants. Procedure of measurement validation is included in the performance calculation to obtain heat balance. Precision of on-line performance calculation is increased via practical modifications of standard calculation algorithms based on the PTC (Performance Test Code). The proposed system also provides useful Web-based aids for performance analysis, including performance data management, a graphic viewer for heat balance and turbine expansion lines, and synthesized reports of performance.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.652-655
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• 2004

In gear-train design, power-flow analysis is a very important process. The method for power-flow analysis apply the power balance equation and torque balance equation to each fundamental circuit. Then, the equation are solved simultaneously to determine the power-flow in planetary gear train. In this paper we perform power-flow analysis of a 6-speed automatic transmission. With this results are used to represent block diagram. In addition, the efficiencies of epicyclic inversion of the 6-speed automatic transmission is obtained.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.515-517
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• 2014

엔진 부조(engine hesitation)의 원인을 추적함에 있어 가장 효과적인 점검방법 중의 하나가 엔진파워 밸런스(engine power balance)를 점검하는 것이다. 본 연구에서는 공회전 상태에서 4개의 실린더 폭발의 압력 편차로 인한 엔진 부조를 점검하기 위해 엔진 파워 밸런스를 점검하는 방법을 사용한다. 엔진의 부조는 네 개의 실린더의 회전 밸런스가 틀어졌기 때문이므로 실린더의 회전 밸런스 정보를 수집 분석하는 방법이 필요하다. 본 연구에서는 실린더의 엔진 회전수를 계산하기 위해 OBD-II와 무선 시스템인 블루투스 모듈을 이용하여 실시간으로 CKP 센서 정보를 수집하는 방법과 밸런스가 틀어진 실린더를 찾는 알고리즘을 제시하여 엔진 파워 밸런스를 조절 관리하는 시스템을 스마트 폰에 구현하고자한다.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1659-1669
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• 2018

An improved circulating current suppression control method is proposed in this paper. In the proposed controller, an outer loop of the average capacitor voltage control model is used to balance the sub-module capacitor voltage. Meanwhile, an individual voltage balance controller and an arm voltage balance controller are also used. The DC and harmonic components of the circulating current are separated using a low pass filter. Therefore, a multiple quasi-proportional-resonant (multi-quasi-PR) controller is introduced in the inner loop to eliminate the circulating harmonic current, which mainly contains second-order harmonic but also contains other high-order harmonics. In addition, the parameters of the multi-quasi-PR controller are designed in the discrete domain and an analysis of the stability characteristic is given in this paper. In addition, a simulation model of a three-phase MMC system is built in order to confirm the correctness and superiority of the proposed controller. Finally, experiment results are presented and compared. These results illustrate that the improved control method has good performance in suppressing circulating harmonic current and in balancing the capacitor voltage.

• The Journal of Korean Physical Therapy
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• v.23 no.3
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• pp.57-63
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• 2011

Purpose: The purposes of this study were to investigate the effectiveness of Pilates exercise on Fitness Factors related to motor performance including flexibility, agility, power, balance, and muscle endurance. Methods: Forty subjects were randomly allocated to one of two groups. The Pilates group did Pilates exercises 3 times a week for 8weeks, 60 minutes each time, and submitted to evaluation of protocols to assess sitting and reaching tests, a standing broad jump test, a side step test, a balance test using a Biodex Stability System, and muscle endurance using CSMI. Results: The Pilates group (n=20) participated in Pilates exercises three times in a week for eight weeks. The results show significant post-test differences in the Pilates group in the following areas: flexibility, agility, power, balance and muscle endurance. There was no significant increase in the control group. Post-exercise, there was no significant difference between the Pilates and control group. Conclusion: The Pilates method can offer significant improvement in personal flexibility, agility, power, balance, and muscle endurance. This study suggests that individuals can improve their Fitness Factors related to motor performance using Pilates exercises that do not require equipment or a high degree of skill. Further study is required to quantify the benefits of Pilates exercise.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1683-1696
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• 2018

Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1263-1271
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• 2014

A novel hysteresis PWM control strategy for synchronous buck converter is proposed. The proposed control strategy is based on ampere-second balance of the modulate capacitor, which not only offers faster transient response to meet the challenges of the power supply requirements of fast dynamic load changes, but also provides better stability and solves the compensation problem of error amplifier in the conversional voltage PWM control. Finally, the steady-state and dynamic operation of the control method is analyzed and verified by simulation and experimental results.