• Journal of Electrical Engineering and information Science
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• 제3권1호
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• pp.103-109
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• 1998

A new flux-weakening scheme for an Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.

• Nuclear Engineering and Technology
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• 제41권3호
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• pp.237-246
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• 2009

Digitalization of not only non-safety but also safety-grade I &C systems with full computerized Main Control Room (MCR) is the recent trend of I&C systems of nuclear power plants (NPP) around the world, while plant maintenance has been shifting from traditional time based maintenance to condition based maintenance. In order to cope with the new trend of operation and maintenance in NPP, a concept of online distributed diagnostic system for both plant operation and maintenance has been proposed in order to further improve both the plant efficiency and the work environment of plant operation staff members by organizational learning. In this respect, the research subjects of human machine interface (HMI) for the online distributed diagnostic system are also discussed for supporting the plant personnel at both MCR and local working places in the plant by the application of advanced ICT (Information and Communication Technologies).

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1999년도 학술대회논문집-국제 전기방전 및 플라즈마 심포지엄 Proceedings of 1999 KIIEE Annual Conference-International Symposium of Electrical Discharge and Plasma
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• pp.228-233
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• 1999

In this paper we develop an electronic starter circuit that is suitable for Neon sign operation of switch-start fluorescent lamps. The developed starter enable single pulse ignition of fluorescent lamp at the peak point of preheating current, irrespective of the position of the Tum-On signal. This is possible due to the sequential operation of two transistors different in their operation characteristics and a diode operation characteristic. The switching endurance test using this starter has been carried for more than 3000 hours for a single switch-start on a severe blinking condition of preheating of 0.1s and of successive lighting interval of 0.1s.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.969-972
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• 2003

This paper deal with a necessary factors for design grid connected photovoltaic system with stand-alone operation, and show simulation results of individual functions and multi- operation according to utility condition. Generally, photovoltaic system have only one operation of either stand-alone or line interactive, and have a isolation transformer for electrical isolation from utility therefore it is bulky, weighty, and a high price system as compared with usefulness. In this paper, A topology and algorithm adequate for lightweight, high efficiency, low price, multi function is selected and inquired into the validity using simulation of variable conditions.

• 한국유체기계학회 논문집
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• 제14권6호
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• pp.68-75
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• 2011

This study simulated the effect of steam injection on the performance and operation of a gas turbine combined heat and power (CHP) system. A commercial simple cycle gas turbine was analyzed. A full off-design analysis was carried out to investigate the variations in not only engine performance but also the operating characteristics of the compressor caused by steam injection. Variation in engine performance and operation characteristics according to various operation modes were examined. First, the impact of full steam injection was investigated. Then, operations aiming to guarantee a minimum compressor surge margin, such as under-firing and partial steam injection, were investigated. The former and latter were turned out to be relatively superior to each other in terms of power and efficiency, respectively.

• 한국도로학회논문집
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• 제17권3호
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• pp.125-132
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• 2015

PURPOSES : The present study aims to evaluate the added $CO_2$ emissions incurred from accelerating operation when to increase the speed up to the allowed level. METHODS : The methodology used are basically the relationship between emission rates and vehicle speeds or acceleration rate. These rates together are used to calculate the added $CO_2$ emissions incurred from accelerating operation. RESULTS : It was resulted that the all the emission rates are increasing proportionally to vehicle speeds or acceleration rates. Additionally, it was also resulted that allowable speeds increasing, the added emission rates are increasing rapidly. CONCLUSIONS : It may be concluded that if the allowable speed ranges are managed, $CO_2$ emissions during vehicle operation are much reduced. From this reason, it was found that the allowable speed during highway design and operation would be much necessary

• Journal of Chest Surgery
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• 제24권10호
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• pp.979-986
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• 1991

From October 1988 to November 1989, seven patients underwent valve replacement during the active phase of native valve endocarditis. There were 4 males and 3 females whose mean age was 41 years[range, 16 to 68 years]. Preoperative two-dimensional and Doppler echocardiography showed vegetations and severe valvular regurgitation in all patients. Blood cultures were positive in 4, and negative in 3 patients Organisms were alpha-hemolytic Streptococcus in 2, Staphylococcus epidermidis in 1, Erysipelothrix rhusiopathiae in 1 patient Valve tissue cultures were negative in all patients. Intravenous antibiotic therapy had been done for 3 to 18 days in 5 patients pre-operatively and was not done in 2 patients, Indications for operation were heart failure in h, and systemic emboli in 1 patient. The aortic valve was involved in 3, mitral in 1, and both aortic and mitral in 3 patients, One operative death[14.4%] occurred in patient with cardiogenic shock before operation. Late death occurred in one on 14 months after operation. The remaining 5 patients were followed up over a two year period in good condition. In conclusion, native valve endocarditis with severe heart failure must be considered for early operation.

• Journal of Chest Surgery
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• 제51권6호
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• pp.395-398
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• 2018

Neo-aortic insufficiency associated with root enlargement following an arterial switch operation is a serious late complication. To achieve successful surgical correction of this condition, multiple factors should be considered, including the individual patient's anatomy, the challenging nature of the redo procedure, and the patient's young age. However, limited publications have described the use of valve-sparing techniques for the treatment of neo-aortic insufficiency associated with root enlargement following an arterial switch operation. Herein, we report our recent experience of a valve-sparing aortic root procedure with ascending aorta and hemiarch replacement despite the presence of a discrepancy in leaflet size and nearby severe adhesions.

• 한국항공우주학회지
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• 제43권6호
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• pp.526-532
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• 2015

국내개발 헬기인 수리온의 악기상 시 운용능력을 입증하고 결빙하 운용 제한 사항을 해제하기 위하여 결빙 감항인증이 요구되고 있다. 군용헬기인 수리온의 결빙 감항인증 절차는 유사 무기체계인 UH-60과 AH-64의 사례와 S/W 기술의 성숙도를 보았을 때, 전산해석${\rightarrow}$모의결빙형상 비행시험${\rightarrow}$인공 결빙 비행시험${\rightarrow}$자연 결빙 비행시험의 4가지 방법에 의한 단계화된 추진이 고려되고 있다. 수리온의 최적 비행시험 소티와 비행시간은 인공 결빙 비행시험 20~30소티 및 20~23시간과 자연 결빙 비행시험 20~30소티 및 20~22시간이 요구되며, 효율적인 결빙 감항인증 비행시험을 위해서는 LWC $0.5{\sim}1.0g/m^3$범위의 대기온도 조건은 인공 결빙 비행시험을 추진하고, LWC $0.5g/m^3$이하의 대기온도 조건에서는 자연 결빙 비행시험이 필요하다.

• 에너지공학
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• 제25권1호
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• pp.122-130
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• 2016

본 연구에서는 1.5MW급의 발전용 디젤 엔진을 대상으로 상용 프로그램인 GT-Power를 이용하여 천연가스와 디젤 혼합연소 엔진 모델을 구축하였으며 이를 통해 기존의 디젤 연소를 하는 경우와 천연가스-디젤 혼합연소를 하는 경우의 엔진 성능 변화를 부하율(50%, 75%, 100%)에 따라 비교하였다. 또한 도서지역에서 실제로 사용되고 있는 부생유를 적용하는 경우의 영향에 대한 연구를 진행하였다. 그 결과 엔진의 운전 조건 변화 없이 천연가스를 디젤과 60% 혼합비로 연소하는 경우 최대 32%의 BSFC 증가를 보였으며 천연가스와 부생유를 혼합연소 하는 경우에도 디젤을 혼합 연소하는 경우와 크게 다르지 않은 결과를 보였다. 이러한 BSFC 증가의 원인을 연료의 불완전 연소율 증가로 제시하고 이에 대한 최적화를 진행했으며 그 결과 60% 혼소율 조건에서 약 2%의 개선효과를 보였다.