• Journal of Power Electronics
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• 제4권3호
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• pp.161-168
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• 2004

This paper presents a new circuit topology of high-frequency soft switching commutation boost type PWM chopper-fed DC-DC power converter with a loadside auxiliary passive resonant snubber. In the proposed boost type chopper-fed DC-DC power converter circuit operating under a principle of ZCS turn-on and ZVS turn-off commutation, the capacitor and inductor in the auxiliary passive resonant circuit works as the lossless resonant snubber. In addition to this, the voltage and current peak stresses of the power semiconductor devices as well as their di/dt or dv/dt dynamic stress can be effectively reduced by the single passive resonant snubber treated here. Moreover, it is proved that chopper-fed DC-DC power converter circuit topology with an auxiliary passive resonant snubber could solve some problems on the conventional boost type hard switching PWM chopper-fed DC-DC power converter. The simulation results of this converter are illustrated and discussed as compared with the experimental ones. The feasible effectiveness of this soft witching DC-DC power converter with a single passive resonant snubber is verified by the 5kW, 20kHz experimental breadboard set up to be built and tested for new energy utilization such as solar photovoltaic generators and fuel sell generators.

• Journal of Power Electronics
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• 제3권4호
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• pp.239-248
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• 2003

This paper presents a novel prototype of three-phase voltage source type zero voltage soft-switching inverter with the auxiliary resonant snubbers suitable for high-power applications with IGBT power module packages in order to reduce their switching power losses as well as electromagnetic conductive and radiative noises. A proposed single inductor-assisted resonant AC link snubber circuit topology as one of some auxiliary resonant commutation snubbers developed previously to achieve the zero voltage soft-switching (ZVS) for the three-phase voltage source type sinewave PWM inverter operating under the instantaneous space voltage vector modulation is originally demonstrated as compared with the other types of resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper. Furthermore, the practical basic operating performances of the new conceptual instantaneous space voltage vector modulation resonant AC link snubber-assisted three-phase voltage source type soft-switching PWM inverter using IGBT power module packages are evaluated and discussed on the basis of switching voltage and current waveforms, output line to line voltage quality, power loss analysis, actual power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, comparing with those of conventional three-phase voltage source hard-switching PWM inverter using IGBT power modules.

• Journal of Public Diplomacy
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• 제2권2호
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• pp.1-26
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• 2022

배경: 조셉 나이(Joseph Nye)의 선구적 저서, 연성권력(Soft Power)이 출간된 이후 소프트파워는 공공외교 연구의 중심 개념이 되었다. 그러나 이 개념은 아직 논쟁 중이라 이를 과도하게 강조하는 정치학자들로 인해 현장 실무에 적용할 수 있는 유용한 지식의 생산은 지체되어 왔다. 나이는 연성권력을 성공적인 공공외교의 수단이자 결과로 정의함으로써 체계적인 분석을 어렵게 했다. 목적: 본 연구의 목적은 효과적인 공공외교에 영향을 미치는 요인 분석을 위한 이론적 모형을 제공함으로써 연성권력과 공공외교의 관계를 나이와는 다른 각도에서 접근하고자 한다. 방법: 본 연구에서 제시하는 이론적 모형은 각국에 신공공외교가 언제 어떻게 도입되었는지 비교적 시각에서 분석하고, 연성권력과 경성권력 자원을 검토하였다. 결과: 다섯개의 차원으로 구성된 본 연구의 이론적 모형은 효과적인 공공외교에 영향을 미치는 요인을 밝히는데 사용될 수 있다. 이 모형을 통해 연성권력 그 자체보다는 공공외교 효과성에 영향을 미칠 것으로 예상되는 사상과 가치, 제도, 거버넌스, 리더십, 의사소통 체계와 같은 정치체제 내의 변수와 홍보학에서 사용하는 평가모형을 결합함으로써 현장에서 적용가능한 지식을 창출할 수 있다. 결론: 본 연구를 통해 공공외교에 관한 정성 분석은 물론 정량분석에 필요한 수많은 가설의 도출을 가능하게 함으로써 공공외교의 이론적, 분석적 발전에 기여할 것으로 예상된다.

• Journal of the Korean Wood Science and Technology
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• 제24권4호
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• pp.87-92
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• 1996

When cutting 2.0cm-thick red oak and hard maple with an air-jet-assisted carbon-dioxide laser of 2kW output power, maximum feed speed at the point of full penetration of the beam decreased with increasing the angle between grain and cutting direction. Feed speed averaged 3.75 and 3.38 meters per minute for red oak and hard maple, respectively. Gray-level of laser-cut surfaces were analyzed by image analysis system. The highest gray level of laser-cut surface was obtained when red oak was cut parallel to grain by laser. Surface profiler was used to scan the sawn and laser-cut surfaces. Center line average roughnesses of laser-cut surfaces were higher than those of sawn surfaces. Scanning electron micrographs showed the cell walls which were melted by laser.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.226-235
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• 1999

Applying digital network technology for advanced nuclear plant requires deterministic communication for tight safety requirements, timely and reliable data delivery for operation-critical and mission-critical characteristics of nuclear plant. Communication protocols, such as IEEE 802/4 Token Bus, IEEE 802/5 Token Ring, FDDI, and ARCnet, which have deterministic communication capability are partially applied to several nuclear power plants. Although digital communication technologies have many advantages, it is necessary to consider the noise immunity from electromagnetic interference (EMI), electrical interference, impulse noise, and heat noise before selecting specific digital network technology for nuclear plant. In this paper, we consider the token frame loss and data frame loss rate due to the link error event, frame size, and link data rate in different protocols, and evaluate the possibility of failure to meet the hard real-time requirement in nuclear plant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.262-265
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• 2003

In this paper, a new active snubber circuit that overcomes most of the drawbacks of the normal "zero voltage transition pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT- PWM converter. A converter with the proposed snubber circuit can also operate at light load conditions. A design procedure of the proposed active snubber circuit is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27[%] and the total circuit loss is about 36[%] of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91[%] in the hard switching case, increases to about 97[%].

• 경영과학
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• 제29권2호
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• pp.143-155
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• 2012

The purpose of this study is to formulate and solve the scheduling problem to heat-treatment process in forging process and apply it to industries. Heat-treatment is a common process in manufacturing heavy forged products in ship engines and wind power generators. Total complete time of the schedule depends on how to group parts and assign them into heat furnace. Efficient operation of heat-treatment process increases the productivity of whole production system while scheduling the parts into heat-treatment furnace is a combinatorial problem which is known as an NP-hard problem. So the scheduling, on manufacturing site, relies on engineers' experience. To improve heat-treatment process schedule, this study formulated it into an MIP mathematical model which minimizes total complete time. Three methods were applied to example problems and the results were compared to each other. In case of small problems, optimal solutions were easily found. In case of big problems, feasible solutions were found and that feasible solutions were very close to lower bound of the solutions. ILOG OPL Studio 5.5 was used in this study.

• 한국안광학회지
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• 제6권1호
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• pp.87-91
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• 2001

PECVD 방법으로 60 Hz 상용전원을 사용하여 발생한 아세틸렌 플라스마로부터 다이아몬드성 탄소박막을 제작하고 Raman 분광에 의하여 D($sp^3$)와 G($sp^2$) 피크를 관측하여 박막의 다이아몬드성 정도를 확인하였고 $sp^3$와 $sp^2$의 비율과 FTIR 결과로부터 박막내의 수소함량의 측정을 통하여 아세틸렌 분압비와의 연관성을 확인하였다.

• 연구논문집
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• 통권28호
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• pp.59-71
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• 1998

The ELID(electrolytic in-process dressing) grinding method is a new precision grinding technique with the special electrolytic in-process dressing by metal bonded grinding wheel, fluid, and power supply. It is possible to make a efficient precision machining of hard and brittle materials such as ceramics, hard metals, and quenched steels by using this method, In this study, a new efficient precision grinding method with ELID was attempted for application to the machining and finishing processes of cylindrical structural components. And, we try to develop the cylindrical grinding technique for mirror surface of ceramics, tungsten carbide and SCM steel, and for the high efficiency grinding of machined parts, for example, ball screw shaft. Electrical characteristics of three different wheel grit sizes of #325, #2000 and #4000 were investigated experimentally. ELID grinding method is proved to be useful for mirror surface generation and efficient machining.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.413-418
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• 2004

Recently, the development of mobile devices demands information storage systems to use micro drive devices. 1-inch micro drive hard disk uses the load/unload(L/UL) technology to increase area recording density and reduce power consumption. Because micro drive has light actuator, effects of the flexible cable that is ignored in 3.5-inch hard disk drive is important to load/unload performances. In this paper, effects of flexible cable on load/unload performances are studied.