• 한국자기학회지
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• 제12권6호
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• pp.212-217
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• 2002

비자성층을 사이에 둔 두 강자성층의 보자력 차이를 이용하여 거대자기저항특성을 나타내는 Ta/CoFe/Cu/NiFe/Ta 구조의 pseudo 스핀밸브를 DC 마그네트론 스퍼터링 방법으로 제조하였다. Ta/CoFe/Cu/NiFe/Ta 구조에서 CoFe층의 두께 변화에 따른 자화 특성 및 자기저항 특성을 조사하였으며, 이 구조에서 CoFe층의 두께가 60 $\AA$일 때 자기저항비는 3.82%이고 CoFe층과 NiFe층 사이의 보자력 차이는 27.4 Oe이다. Ta/CoFe/Cu/NiFe/Ta 구조를 갖는 pseudo 스핀밸브에서 CoFe층과 NiFe층의 보자력 차이는 CoFe층의 두께가 20 $\AA$에서 40 $\AA$까지 증가함에 따라 증가하였으며 40 $\AA$ 이상에서는 감소하였다. 이와 같은 결과는 박막의 결정성 및 포화 자기변형(λ$_{s}$)의 변화에 의한 것으로 판단된다. Cu층과 NiFe층 사이에 CoFe층을 삽입한 Ta/CoFe/Cu/NiFe/Ta 구조에서 삽입층인 CoFe층의 두께 변화에 따른 자화특성 및 자기저항 특성을 조사한 결과 CoFe두께가 10$\AA$시 자기저항비가 6.7 %이며. 삼층막 구조 보다 자기저항비가 약 1.5배 이상 증가함을 알 수 있었다.

• Journal of Mechanical Science and Technology
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• 제20권4호
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• pp.447-454
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• 2006

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.

• 조명전기설비학회논문지
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• 제28권10호
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• pp.16-26
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• 2014

This paper proposes new 13-level inverter topology and DC/DC converter buck-boost structure topology for multilevel, compounding uni-directional and bi-directional switches, and proposes high-efficient multilevel inverter system in which the proposed two PCS(Power Conditioning System) was connected in series. In proposed multilevel inverter of forming a output 13-level phase voltage by using total 18 switching parts, Then bi-directional switch has a characteristic of reducing conduction loss and controlling the reactive power effectively by separating electrically from the neutral point. DC/DC converter for supplying in dependent 3 DC voltage to the proposed multi-level inverter generates 180-degree phase shifted PWM by the symmetrically combined structure of 2 buck-boost converter and twice switching frequency efficiency can be obtained, meanwhile, the converter can step up/down the output voltage and 20% output can be generated comparing the input voltage. This proposed system is verified with the simulation and laboratory test.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.290-295
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• 2005

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.

• 한국자기학회지
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• 제14권1호
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• pp.25-28
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• 2004

Ta/NiFe/Cu/Co 구조의 Pseudo 스핀밸브 박막을 제작하여 NiFe, Cu, Co 각 층들의 두께변화에 따른 자기저항비(MR-ratio), 보자력, 자기 민감도(sensitivity), 반전자장(Switching Field)의 크기 등의 자기적 특성을 연구하였다. 각 층들의 두께를 변화시키면서 측정한 결과 Ta(4 nm)/NiFe(7.5 nm)/Cu(3 nm)/Co(5 nm)에서 최대 자기저항비 7.26 %를 얻을 수 있었다. 또한 각 층들의 독립적인 자화 과정을 통해 자기저항 특성을 조절할 수 있었다. 특히 Co의 두께를 변화시켜 자기저항비를 비교적 일정하게 유지하면서 보자력의 크기를 조절할 수 있음을 알게 되었다.

• 한국자기학회지
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• 제23권3호
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• pp.98-103
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• 2013

NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe 이중 거대자기저항-스핀밸브(GMR-SV) 박막의 진공 후열처리 온도의존성을 조사하여 강자성층 자화용이축을 유도하였다. 자유층과 고정층의 자화용이축에 의존하는 이중 스핀밸브 박막의 자기저항곡선은 외부자기장 각도를 다르게 하면서 측정하였다. 열처리온도가 $105^{\circ}C$일 때, $0^{\circ}$와 $90^{\circ}$ 사이 임의 측정 각도에서 약 2.0 %/Oe인 자장감응도 특성을 얻었다. 이러한 결과는 면상 강자성층과 자유층을 면상에서 서로 직교한 자화방향 유도를 통하여 이중구조 GMR-SV 박막이 고감도 바이오센서로 사용할 가능성을 제시하였다.

• Design & Manufacturing
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• 제2권5호
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• pp.30-33
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• 2008

Injection Molding is the most effective process for mass production of plastic parts. The injection molding process is composed with several steps such as Filling, Packing, Holding, Cooling, Ejecting. Among them, filling and packing process should be considered carefully to improve accuracy of dimension, surface quality of plastic parts. Usually the quality above-mentioned is managed with weight of part after molding on the field. In this paper, a series of experiment for molding automotive front bumper was conducted with cavitity temperature sensor to optimize switch-over time(V-P switching), hot runner vale gate sequence time during filling and packing step for the purpose of uniform quality, weight at every molding. As a result, it was found that it is effective method to use temperature sensor in injection molding for quality control of plastic molding.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.794-795
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• 2011

The DC side voltage and current of a HVDC transmission system are directly affected by non-linear switching devices such as the thyristor valve which causes real power losses, even under the superconducting conditions of a high temperature superconducting (HTS) power cable. This paper deals with the development of miniaturized superconducting DC cable system. The authors designed and fabricated two thyristor converters for DC transmission system. One is operated as a rectifier and the other is an inverter. The HTS model cable was connected between the DC side of the rectifier and inverter. Real DC transport current and voltage were applied to the miniaturized HTS DC cable. Experimental results are discussed in detail.

• 설비공학논문집
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• 제13권1호
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• pp.66-71
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• 2001

In the air-conditioning industry, the refrigerant charging amount is one of the most important parameters affecting the energy efficiency ratio of heat pumps. An experimental study was performed on the characteristics of an inverter driven air-to-air heat pump system with a variation of compressor frequency and charging amount of refrigerant. The frequency was altered from 40Hz to 70Hz and the charging amount was changed from 1.6kg to 2.8kg in tests. The variation of performance was measured with switching of the expansion valve on each frequency and charging amount. All the tests were performed at the Korean Standard and test conditions of the air conditioners. As results, it was found that there existed the charging amount and the level of the suction gas superheat which provided the highest energy efficiency ratio at all the frequency bands.

• 한국연소학회지
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• 제15권2호
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• pp.27-33
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• 2010

Recently, much attention has been paid to utilizing highly preheated air up to $1,000^{\circ}C$ through waste gas in industrial furnaces. The regenerative burner technology has shown to provide significant reduction in energy consumption (up to 60%), downsizing of the equipment (about 30%) and lower emissions (about 30%) while maintaining high thermal performance of the system since 2000. The object of this study is to develop the flameless regenerative burner for industrial furnaces based on the FLOX(Flameless Oxidation) principle and it has been designed and manufactured as pilot scale. Performance tests are experimentally done and their results are discussed. They showed 1) a very good uniformity in temperature distribution, 2) about 100 ppm in NOx at the temperature $1,300^{\circ}C$, 3) about 95% in temperature efficiency. Besides, the regenerative burner has advantage in easy maintenance and high usage rate of regenerator due to the separate and portable type of heat exchanger.