• Journal of Power Electronics
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• v.18 no.6
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• pp.1634-1641
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• 2018

This study focuses on a high-performance direct active and reactive power controller design that is successfully applicable to three-phase pulse width modulation (PWM) AC/DC converters used in renewable distributed energy generation systems. The proposed controller can overcome the sluggish transient dynamic response of conventional controllers to rapid power command changes. Desired active and reactive powers can be thoroughly obtained at the end of each PWM period through a deadbeat solution. The proposed controller achieves an exact nonlinear cross-coupling decoupling of system power without using a predefined switching table or bang/bang hysteresis control. A graphical and analytical analysis that naturally leads to a control voltage vector selection is provided to confirm the finding. The proposed control strategy is evaluated on a 3 kW PWM AC/DC converter in the simulation and experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.398-402
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• 2008

Recently, the development of superconducting fault current limiters (SFCLs) has been required as power demands increase in the power system. A distribution-level prototype resistive SFCL using coated conductor (CC) has been developed by Hyundai Heavy Industries Co., Ltd. and Yonsei University for the first time in the world. The ratings of the SFCL are 13.2kV/630A at normal operating condition. A novel non-inductive winding method is used in fabricating coils so there is almost zero impedance during normal operation. The distribution SFCL is cooled by sub-cooled liquid nitrogen $(LN_2)$ of 65K and 3 bar to enhance cryo-dielectric performance, critical current density, and thermal conductivity. In order to make reliable operation of an SFCL in real power systems, we monitored and controled its operation conditions by using supervisory control and data acquisition (SCADA) method. Thus, a monitoring system for the SFCL employing information technology (IT) is proposed and developed to be on the lookout for the operation conditions such as inside temperature, inside pressure, $LN_2$ level, voltage and current. Since operation temperature should be kept constant, bang-bang control for temperature feedback with a heater attached to the cold head of cryo-cooler is applied to the system. Short-circuit tests with prospective fault current of 10kA and AC dielectric withstand voltage tests up to 143kV for 1 minute were successfully performed at Korea Electrotechnology Research Institute. This paper deals with the development of a distribution level SFCL and its monitoring system for reliable operation.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.2
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• pp.17-27
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• 2007

Minimum-time attitude maneuvers of three-axis stabilized spacecraft are presented to study the feasibility of using three magnetic torquers perform large angle maneuvers. Previous applications of magnetic torquers have been limited to spin-stabilized satellites or supplemental actuators of three axis stabilized satellites because of the capability of magnetic torquers to produce torques about a specific axes. The minimum-time attitude maneuver problem is solved by applying a parameter optimization method for orbital cases to verify that the magnetic torque system can perform as required. Direct collocation and a nonlinear programming method with a constraining method by Simpson's rule are used to convert the minimum-time maneuver problems into parameter optimization problems. An appropriate number of nodes is presented to find a bang-bang type solution to the minimum-time problem. Some modifications in the boundary conditions of final attitude are made to solve the problem more robustly and efficiently. The numerical studies illustrate that the presented method can provide a capable and robust attitude reorientation by using only magnetic torquers. However, the required maneuver times are relatively longer than when thrusters or wheels are used. Performance of the system in the presence of errors in the magnetometer as well as the geomagnetic field model still good.

• The Journal of Internal Korean Medicine
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• v.16 no.1
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• pp.181-196
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• 1995

The present experiments were designed to investigate the effects of BangPoongSan on the cardiovascular system in the experimental Animals. And thus the change of blood pressure, auricular blood flow, artery contraction, death rate, platelet aggregation repression, plasma coagulation factor activity, plasma antithrombin activity, whole blood viscosity and plasma viscosity were studied. The result were summarized as the followings: 1. BangPoongSan dropped the blood pressure in the spontaneous hypertensive rat. 2. The drug increased the auricular blood flow in rabbit. 3. The drug relaxed the artery contraction by pretreated norepinephrine in white rat. 4. The drug inhibited the death rate of mouse which was led to thromboembolism by serotonin and collagen. 5. The drug inhibited the platelet aggregation in rat. 6. The drug prolonged the prothrombin time and activated partial thromboplastin time on the test of plasma coagulation factor activity in rat, but was not valuable. 7. The drug presented the antithrombin activity in rat. 8. The drug reduced the whole blood viscosity and plasma viscosity in rat, but the latter was not valuable. According to the results, Bangpoongsan increased the blood flow and dropped the blood pressure by dilatation of blood vessel smooth muscle. And the drug presented the antithrombin acivity, inhibited the platelet aggregation and reduced blood viscosity. Therefore these effects are assumed to improve the cardiovascular circulation disorder and prevent thrombosis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3331-3339
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• 2009

This study analyzed relation with performance on the job by strategy of outsourcing as study about outsourcing and system operation performance of mid-size ERP systems. To summarize the results of this study, first, mid-size ERP outsourcing companies in stages, rather than the big bang approach to introducing more effective measures could get the conclusion. Second, ERP outsourcing, the business strategies of the big bang as significant were analyzed in terms of partnership. This section introduces the methodology and business partners, regardless of outsourcing could be distinguished from the very important variables. As a result, the standard for business enterprises mid-size mad to keep a systematic business analysis is very difficult. Therefore, a gradual introduction of a step by step implementation of such a methodology capable of performing reliable business methods are needed.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.3
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• pp.392-400
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• 2019

This paper provides a fin actuation system of missile based on electromagnetic-spring mechanism to miniaturize the system and lower the cost. Compared with proportional electro-mechanical actuators, the output of Electromagnetic-Spring Actuators(EMSA) has two or three discrete states, but the mechanical configuration of EMSA is simple since it does not need power trains like gears. The simple mechanism of EMSA makes it easy to build small size, low cost, and relatively high torque actuators. However, fast response time is required to improve the dynamic performance and accuracy of missiles since bang-off-bang operation of EMSA affects the flight performance of missile. In this paper the development of EMSA including parameter optimization and mathematical modeling is described. The simulation results using Simulink and experimental test results of prototype EMSAs are presented.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.87-92
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• 1998

It is needed that the small, cheap and low power dissipated image stabilizing system is used in a small camcorder. It is essential to detect the hand shake of human exactly for the good design of image stabilizing system. In this study, the hand shake is measured by the experiment on 17 peoples in peak-to- peak voltage and frequency. The shake of image by hand by hand is independent of human age or weight, and dependent of calmness of character or concentration of mind.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.671-672
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.165-170
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• 1991

최근의 컴퓨터, 자동화 기기, 로봇 등으로 대표되는 산업용기기나 정밀전자 부품제조 기기등의 진보는 눈부신 바가 있으며 그들의 구동 부분에 대한 정밀도가 높은 위치결정, 고속 응답성, 소형화 등의 요구가 점차 높아져 가고 있다. 그러므로 고속응답성을 이루기 위하여서는 플랜트의 상태 방정식을 구조조건으로 하고 주어진 성능지수를 최소화하는 최적제어이론에 기반을 둔 Rang-Bang control를 positioning servo system에 적용시켜야 한다.(중략)

• Journal of the Korean Society of Systems Engineering
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• v.2 no.1
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• pp.5-10
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• 2006

This paper describes an operational concept of ships with CEC system. An operational architecture is derived using systems engineering approach. From consideration of operational environments and stakeholders, the operational concept scenarios are established and its requirements are derived. The operational requirements based operational architecture is presented using a computer aided systems engineering tool.