• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.254-255
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• 2013

본 논문에서는 저항센서와 바이패스 스위치를 이용한 평균 전류 모드 제어의 부스트 컨버터 저손실을 측정하는 방법을 제안한다. 일반적으로 저항을 이용한 전류센싱 방법은 손실을 가지며 이는 전체 시스템의 효율을 감소시키게 된다. 제안된 전류 측정 기법은 저항센서에 병렬로 바이패스 스위치를 적용하여 전류센서에서 발생되는 손실을 바이패스 스위치를 통해 손실을 최소화 할 수 있다. 본 논문에서는 50W급 평균 전류 모드 부스트 컨버터를 제작하여 바이패스 스위치를 통한 효율 개선을 아날로그 회로로 구현하여 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2342-2344
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• 2000

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operation, of drum type steam generator. But, nowadays, almost all of them were of high efficiency, of supercritical pressure, of great capacity(about 500MW), of sliding pressure operation, of once through type steam generator. Presently built once through boiler introduces turbine bypass systems to variable pressure operation which eliminates unexpected materials in boiler tube during startup, minimizes fuel loss by short startup period, eventually improves total efficiency and power system stability

• 전력전자학회논문지
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• 제25권3호
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• pp.235-241
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• 2020

In this paper, we propose the bus/bypass synchronization phase lock loop (B-Sync PLL) method using each phase voltage controller of a parallel UPS inverter. The B-Sync PLL included in each phase voltage control system of parallel UPS inverters has the transient response and the phase synchronization error at grid normal or blackout. The validity of this method is verified by simulation and experiment. As a result, the parallel UPS inverters using the proposed method confirmed that the output phase was continuously synchronized when a grid blackout, improving the transient response characteristics for stable load power supply and equal load sharing.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2321-2329
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• 2005

One means of fulfilling $CO_2$ emission legislation is to downsize engines by boosting their power using turbochargers or mechanical superchargers. This reduces fuel consumption by decreasing the engine displacement. When a turbocharger, which is preferable to a mechanical supercharger in terms of fuel efficiency, is used, there is insufficient availability of exhaust gas energy at low engine speeds, resulting in an unfavorable engine response. Therefore, mechanically driven superchargers have increased in popularity due to their quick response to changing speeds in the transient phase. However, since a mechanical supercharger obtains its driving power from the engine, it is difficult to decrease its fuel consumption. This remains a large negative factor for superchargers, despite their excellent dynamic performance. This study aims to develop a power control concept to improve the fuel economy of a mechanical screw supercharger, which could then be used for engine downsizing.

• 전력전자학회논문지
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• 제20권2호
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• pp.130-136
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• 2015

This study describes the structure and operation modes of vertical stabilization (VS) converter for international thermonuclear experimental reactor (ITER) and proposes a protection method. ITER VS converter supplies voltage (${\pm}1000V$)/current (${\pm}22.5kA$) to superconducting magnets for plasma current vertical stabilization. A four-quadrant operation must be achieved without zero-current discontinuous section. The operation mode of the VS converter is separated in 12-pulse mode, 6-pulse mode and circulation current mode according to the magnitude of the load current. Protection measures, such as bypass and discharge, are proposed for abnormal conditions, such as over current, over voltage, short circuit, and voltage sag. VS converter output voltage is controlled to satisfy voltage response time within 20 msec. Bypass operation is completed within 60 msec and discharge operation is performed successfully. The feasibility of the proposed control algorithm and protection measure is verified by assembling a real controller and implementing a power system including the VS converter in RTDS for a hardware-in-loop (HIL) facility.

• 전력전자학회논문지
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• 제19권2호
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• pp.99-105
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• 2014

This paper proposes the reliability improvement of H-Bridge Multi-level (HBM) inverter. This reliability can be implemented through modularization of power circuit, distribution of controller, duplication of controller and communication, and continuous operation method in case of power cell failure for driving medium-voltage & high-power induction motor. It is shown that the modularization and expansion characteristics of the HBM inverter are improved since the individual inverter modules operate more independently when using the proposed concept. Also the fault tolerance is increased by using power cell bypass. The proposed design and control methods are described in detail and the validity of the proposed system is verified experimentally in various industrial fields.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.353-358
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• 2001

Turbo-charging or Super-charging has been used to boost engine power for Gasoline Engine and Diesel Engine came to the world at the beginning of $20^{th}$ century. So far Turbo-Charger has enjoyed a high reputation in the charging filed for its technical advantages such as no demand of operation power from engine and an excellent charging effect in the event of a static operation at mid- and high engine speed. A mechanically driven Super-Charger, however, is now emerging in order to meet demands of the age of speed such as high engine power for a quick change of the driving mode - high engine torque even at low engine speed. Since Super-Charger needs driving power from engine, it cannot improve its relatively higher fuel consumption against that of Turbo-Charger. This negative point is still an obstacle to the wide use of Super-Charger. Super-Charger using Screw-type compressor which has already had a considerable base in air compressor market will fulfill this purpose of improving fuel consumption by minimizing operation power owing to no charging at idling or partially loading driving. This study aims to develop power control concept to achieve this minimization of operation power.

• 동력기계공학회지
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• 제18권5호
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• pp.48-54
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• 2014

In this paper, three refrigeration systems bypassing hot-gas to compressor outlet, compressor and condenser outlet and evaporator inlet are theoretically compared to offer basic design data for performance depending on cooling load using a HYSYS program. The main results are summarized as follows : First, the COP of third system is the highest. Next, the COP of second system is higher than first one. And, the temperature of compressor inlet of third system is constant for all cooling load. Compared to first and second system, the compressor inlet temperature of the first system is higher than second one for all cooling loads. From the above results, third system, which is bypassing hot-gas to evaporator inlet, is more advantageous when considering the precise temperature control and excellent performance of oil and water cooler of industrial machine.

• Journal of Chest Surgery
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• 제22권3호
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• pp.402-415
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• 1989

Extracorporeal circulation leads to functional disorder and structural damage of organs, especially hematologic and pulmonary system, mainly by sequestration of neutrophils and deposition of macrophages at lung. Then, proteases are secreted, which insult vascular basement membrane of pulmonary capillary and alveolar septa of the lung. Among these, the most important protease at lung is elastase, because major component of lung is elastin. For prevention of lung injury, inactivators or antidotes to elastase should be necessary and Alpha 1-Proteinase Inhibitor is the elastase inactivator. Clinical experimental study was carried out to investigate the immediate postoperative change of serum Alpha 1-PI level following cardiopulmonary bypass for 20 heart cases [congenital 16 cases, acquired 4 cases] and 10 control [subtotal gastrectomy] cases. Also preliminary study was performed for 31 cases of open heart patients. The results were as follows: l. Immediate postoperative serum levels of Alpha 1-PI was significantly decreased at open heart surgery group [P< 0.005], but not decreased at control group. 2. There were no significant difference in change of serum Alpha 1-PI level between and membrane and bubble oxygenator group.Z 3. There were no significant difference in changes of serum Alpha 1-PI level between CHD and AHD. Alpha 1-PI is consumed at lung during cardiopulmonary bypass and increase after operation compensatedly and protect multiple organic damage especially lung. Therefore, Alpha 1-PI can be indicator for evaluation of prevention and treatment of pump-lung syndrome.

• Journal of Chest Surgery
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• 제31권5호
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• pp.502-508
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• 1998

인공 심폐기를 이용한 체외순환은 우리 몸에 전신적인 염증반응을 일으키므로 수술후에 여러장기의 기능부전을 초래할수 있다. 이러한 염증반응은 체외순환후 체액성, 세포성 및 보체계등의 면역계가 활성화 되어 전체적인 염증반응을 일으키는 것으로 일부연구에서 보고하고 있으며, 이러한 염증반응에는 Tumor Necrosis Factor-$\alpha$(TNF-$\alpha$)를 비롯한, Interleukin-1, Interleukin-6, Interleukin-8 등의 cytokine등 이 전구물질로써 중요한역할을 하는 것으로 알려져 있다. 본 교실에서는 이러한 cytokine의 유리를 억제함으로 체외순환후 염증반응을 줄일수 있다는 가정하에 항염증작용이 있는 부신피질 호르몬을 체외순환전에 투여함으로서 염증반응이 현저히 감소하는지를 혈청내 TNF-$\alpha$를 측정하여 비교 연구하였다. 1996년 6월부터 1996년 8월까지 심장수술환자 20명에서 전향적 연구를 했다. 10명의 비교군은 수술 하루전, 마취전, 체외순환 시작 5분후, 대동맥 차단시작 5분후, 대동맥 차단 끝나기 5분전, 체외순환 끝나기 5분전, 재관류후 2시간, 4시간, 6시간, 12시간, 24시간 별로 10cc씩 채혈하여 TNF-$\alpha$의 수치를 ELISA 방법으로 측정하였고 10명의 스테로이드군은 마취 1시간전에 부신피질 호르몬(Dexamethasone 1mg/Kg)을 정맥주사하고 채혈은 비교군과 같게 했다. 그리고 양군에서 수술전 심전도 및 혈청내 LDH, CPK 효소치와 백혈구 수치를 측정하고 수술후 1일째, 3일째 재측정하였으며, 수술후 3일째내에 환자의 혈압동태 ,폐기능 상태 및 회복상태를 관찰하여 비교하였다. 환자군 간에 LDH 및 백혈구 수치간에 의미있는 차이는 없었으나 CPK 수치가 수술후 첫째날/세째날 비교군이 1122$\pm$456/864 $\pm$42 이고 스테로이드군은 567$\pm$471/325$\pm$87로 큰 차이를 보였고(P=0.002), CPK-MB 효소는 술후 1일째 비교군이 106.4, 스테로이드군이 29.5로 이의있는 차이를 보여주었으나(P=0.02) 수술후 3일째에는 두 군간의 차이가 없었다. 수술후 72시간 관찰기간중 비교군에서 4명의 환자가 3번 이상의 저혈압으로 처치가 필요했고 38$^{\circ}C$ 이상의 발열은 3명의 환자에서 있었다. 환자군 간에 대동맥 차단시간과 체외순환 시간간에 의미있는 차이는 없었고, 인공호흡기 부착시간과 중환자실 체류기간, 입원기간 비교에 있어 스테로이드군이 적은 수치를 보였으나 통계학적 의미는 없었다. TNF-$\alpha$는 대동맥 차단 5분후부터 체외순환 끝나기 5분전까지 양군에서 현저히 증가하였는데 비교군은 체외순환 끝나기 5분 전에 측정한 수치의 평균은 22.3$\pm$6.8 pg/ml였고, 스테로이드군은 대동맥 차단 끝나기 5분 전에 측정한 수치의 평균은 11.9$\pm$4.7 pg/ml였다. 이상의 연구결과에서 수술전 부신피질 호르몬을 정주함으로 체외순환시 Cytokine의 분비를 억제하여, cytokine으로 인한 심장수술후 발생할수있는 전신적 염증반응을 감소시킬것으로 기대되므로 수술후 환자의 중환자실 체류기간, 입원기간 및 합병증률을 줄일 수 있으리라 생각된다.