• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.85-91
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• 1998

This paper describes an study electric injection system for diesel engines. It is needed effective fuel injection which controls the solenoid valve of fuel pump. To solve this, this paper proposes DCC-PWM method which can realize fast reply and low holding current for solenoid valve on/off. For the proposed design method, simulation tools of ACSL are used to analyze the system. And the single-chip microcomputer is used to reduce the size of controller and to improve flexibility. And the systems validity can be verified through the experimental results.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.375-376
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• 2001

건축 기술의 발달과 도시토지 이용의 효율성을 강화하기 위하여 최근에는 초고층 건물이 많이 건설되고 있다. 이러한 초고층 건물은 에너지 절약적인 설계로 높은 기밀성을 가질 뿐 아니라, 외주부 또한 개폐할 수 없는 유리벽에 의하여 구획되므로 자연 환기에 열악한 특성을 지니고 있다. 초고층 건물의 경우 배기시스템으로 중앙집중배기방식을 채택하고 있으며, 중앙배기시스템은 배기입상덕트의 형상 및 규격, 흡출기의 성능, 그리고 기상조건 등 여러 변수들에 의해 영향을 받는다. (중략)

• 전기의세계
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• v.25 no.4
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• pp.28-31
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• 1976

Thyristor는 많은 전력기기와 결합되어 전기기기 전반의 양상을 크게 변화시키고 있다. 예를 들면 변압기의 불꽃없는 탭이나 회전기의 정류자에 대치되는 무정류자전동기와 그리고 개폐기, 차단기의 대용등을 생각할 수 있다. 전력변환장치로서는 (1)직류전력을 조정하는 목적으로 Thyristor를 일종의 스위치로써 직류전압을 단속시켜 직류평균전력을 제어하는 DC Chopper (2)교류전원에 두개의 Thyristor를 역병렬접속하여 교류전류의 통전기간을 위상제어에 의하여 교류를 제어하는 AC Chopper (3)직류를 교류로 변환하는 자여식 inverter등이 있다. 본 해설에서는 지면관계상 D.C Chopper방식에 대한 기본회로와 그의 이용만을 취급한다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.104-108
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• 1999

1998년말 현재 우리나라의 시설원예 면적은 48,612ha이고 전체의 90.2%인 43,852ha가 단동비닐온실을 비롯한 관행온실이고, 9.8%인 4,760ha만이 자동화 온실이다. 관행의 단동비닐온실은 태양광에 의존하여 무가온으로 재배하고 있으며, 대부분 2중 하우스로 하거나 내부에 터널을 설치하여 보온덮개를 개폐하는 방식의 보온을 위주로 하여 온실의 온도를 관리한다. (중략)

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.89-95
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• 2016

In this paper, we propose a locker system that can remotely control and manage locker. The main features of the proposed system are follows. First, connect the locker with server and then open the locker after passing through the certification process in server. Second, locker manager can more systematically manage a locker by using locker management system based on smart phone. Third, provide an instant locker for temporary using lockers to increase the ease of use. Fourth, unlike traditional analog locker, can support better security by using authentication process and log data. Performance evaluation is performed via simulation by making the dummy model. The results of performance evaluation show the proposed system can support efficiently the locker management.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.4
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• pp.1-9
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• 2010

Fuel shutoff valve of a gas generator controls propellant mass flowrate of a rocket engine, by using pilot pressure and spring force. The developing fuel shutoff valve can be self sustained even though pilot pressure is removed in an actuator. Therefore, it is necessary to analyze the characteristics of the forces with respect to the opening and closing of the valve in order to evaluate its performance. In light of this, the valve has been designed to adjust the control pressure for the opening of the poppet and to determine the working fluid pressure at which the valve starts to close. This paper also has been designed dynamic model using the AMESim and predicted flow coefficient of the valve by Fluent CFD analysis. Various results from the prediction and the analysis have been compared with experiments. Finally, dynamic characteristics of the valve have been verified with experimental results.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.160-166
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• 2014

The shutoff valve of a Liquid Rocket Engines (LRE) controls the flow of propellant between turbo-pump and combustion devices of LRE using pilot pressure and spring force. The shutoff valve is closed when the pilot pressure is removed from the diaphragm type actuator. During designing process of life cycle is when should be analyzed according to the characteristics of forces with respect to the opening and closing of diaphragm actuator. A valve has been designed to adjust the control pressure which is required to open a poppet and to determine the working fluid pressure at which a valve starts to close. During flow capacity test under room temperature as a part of life cycle tests, the leakage in diaphragm was occurred due to the leakage of sheet welding sections. The operating cycle of the diaphragm type actuator is about 61 times with 22 MPa of pilot pressure.

• KIEAE Journal
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• v.7 no.4
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• pp.57-62
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• 2007

At the moment, the reduction of building energy consumption is a unavoidable task of mankind for conserving global environment. Decreasing overall U-value of building envelope and air infiltration, especially in Korean climate condition with clear four seasons, are the obvious solutions for the objective. Thus low glazing ratio with small window openings are required for heating and cooling load reduction in buildings. Using larger window openings could provide better natural ventilation but it also increases the direct solar radiation penetration into indoor space, heat gain in summer and heat loss in winter. On the other hand, the ventilation rates decreasing problem with smaller window openings could be occurred. As a solution for it, the use of casement window can cause increasing natural ventilation rates by wing wall effect. This paper focuses on deduce the most efficient opening type of casement window in Korean climate. To estimate ventilation performance of each opening types, CFD simulation was used. The best performance of opening type in every wind direction is opening both windows to the center and the most appropriate opening type for Korean climate is also opening both windows to center.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.493-496
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• 2000

This study is about the design and fabrication of optical voltage sensor modules improved in the insulation reliability, where we adopted the space-division voltage system using the auxiliary electrodes to apply the uniform electric fields to the BSO, the device of which the polarization state varies with the variation of refractive index in the electric fields. We measured the output of fiber-Optic Voltage Sensors with the temperature changes in the thermostatic oven. And we measured the output of Fiber-Optic Voltage Sensors after setting its up in the disttibuion automated switch being apply 60Hz alternating voltage from 6.6kV to 17.BkV. In result, measured error characteristic is good, so we can judge it is applicable to the practical case

• Journal of Energy Engineering
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• v.24 no.4
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• pp.63-70
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• 2015

Crevices between window and window frame cause not only heat losses but also serve path to sound transmission and infiltration of fine dusts that are harmful to humans. There were many efforts in the past to eliminate these crevices but because of the windows' indispensable function of opening and closing, it was an unsolvable problem. In this study, a new type sliding window is developed by applying horizontally rolling wheels to implement a surface sealing which is excellent for enhancing air tightness. To evaluate the feasibility of the newly developed window, forces for opening and closing, durability and air tightness were testet according to Korean Testing Standards. Force for opening a 2000 N window is 30 N. It endured 100,000 cycles of opening and closing. Infiltration was $0.00m^3/(m^2h)$ for a pressure difference of 10 Pa. Since this window has few moving parts, it has favorable features of low cost and few breakdown.