• 한국분말재료학회지
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• 제12권4호
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• pp.296-302
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• 2005

In order to improve mechanical properties, the hypereutectic Al-20 wt%Si based prealloy powder was prepared by gas atomization process. Microstructure and compressibility of the atomized Al-Si powder were investigated. The average powder size was decreased with increasing the atomization gas pressure. Size of primary Si particles of the as-atomized powder was about $5-8\;\mu{m}$. The as-atomized Al-Si powder such as AMB 2712 and AMB 7775 to increase compressibility and sinterability. Relative density of the mixed powder samples sintered at $600^{\circ}C$ was reached about 96% of a theoretical density.

• 한국소음진동공학회논문집
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• 제14권5호
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• pp.439-448
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• 2004

Magnetic bearing is an attractive device in precision engineering field because of its non-contacting nature and controllability of its dynamic characteristics. This paper provides a method of designing a sliding mode control for an active magnetic hearing(AMB) system which is used to support the elevation axis of a target tracking sight instead of mechanical bearings to eliminate the effect of mechanical friction. In such system, the axis should be levitated and supported within a predetermined air gap while AMB is excited by base motion. Experimental results showed that the sliding mode control is effective in disturbance rejection than conventional PID-control without any additive measurements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.548-553
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• 2000

A new design of cylindrical capacitive sensor(CCS) for the displacement measurement of precision active magnetic bearing(AMB) spindle is presented in this paper. This research is motivated by the problem that existing 4-segment CCS is still sensitive to the $3^{rd}$ harmonic component of the geometric errors of a rotor. The procedure of designing new CCS starts from the modeling and error analysis of CCS. The angular size of CCS is set up as a design parameter, and new 8-segment CCS is introduced to possess an arbitrary angular size. The optimum geometry of CCS to minimize the effect of geometric errors is determined through minimum norm approach. Experimental results with test rotors have confirmed the improvement in geometric error suppression.

• 한국분말재료학회지
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• 제9권2호
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• pp.116-123
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• 2002

The characteristics of two commercial 2xxx series Al alloy powders, AMB2712 and 201AB, were evaluated and their compacting and sintering characteristics were discussed in tems of compacting pressure. The particle shapes of both two powder mixtures were irregular and their particle size distributions were broad. The compactibility of AMB2712 was superior to that of 201AB because of better fluidity. The sintered density was higher than the green density at low compacting pressure, however, it was lower than the green density when the samples were compacted at higher pressure due to the selling during sintering. The sintered density was alomost the same as the green density at the "homogeneous deformation" stage. It was observed that pores were created at the triple points due to the rapid diffusion of Cu in Al. Cu in Al.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권2호
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• pp.82-89
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• 2004

In this paper, an active magnetic bearing(AMB) system is designed and controlled using a digital Proportional-Integral-Derivative(PID) control concept. The plant dynamics consisting of actuator and rigid rotor dynamics are described. A digital PID controller with a global control and a local control concept is designed and implemented using digital signal processor. Some experiments are conducted with each global control and local control concept. These include start-up test, impulse test, whirl response, and generator load test. The experimental results and comparison between those of a global control and a local control indicate that the global control of concept has impressive static and dynamic control performance for the prototype considered. From the whirl test, the developed system set can be controlled within about $\pm10\mu\textrm{m}$ gap variation at the rotational speed of 6000rpm and generate the AC power of frequency of $60\textrm{Hz}$, voltage of 100V and current of 0.8$\textit{A}$.

• 한국응용과학기술학회지
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• 제38권5호
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• pp.1265-1272
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• 2021

본 연구는 황기 에탄올 추출물과 황기 생물전환 추출물의 기능성 화장품 소재로서 가능성 여부를 규명하고자 하였다. 항산화 효과를 확인하기 위해 폴리페놀과 플라보노이드 함량을 측정하였고, 세포실험을 통해 피부 세포에 대한 독성과 피부 세포 노화에 대한 연구를 수행하였다. 항산화 실험 결과, 폴리페놀, 플라보노이드 효과에서는 폴리페놀과 플라보노이드의 함량이 농도 의존적으로 증가하였고, 생물전환 추출물에 비해 에탄올 추출물에서 높은 것으로 확인되었다. 황기 추출물과 생물전환된 황기추출물이 HDF 세포에서 농도 의존적으로 MMP1 발현 억제 효과가 증가되는 것을 확인하였다. 따라서 본 연구는 황기 추출물과 황기 생물전환 추출물의 기능성 화장품 소재로 사용 시 항산화와 피부 노화 예방 관점에서의 기능성 화장품 소재로 매우 유용하게 활용될 수 있을 것으로 사료된다.

• 한국식품영양과학회지
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• 제40권12호
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• pp.1793-1796
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• 2011

기원식물별, 재배연수별 황기 에탄올 추출물의 항산화활성 및 NO 생성능을 측정한 결과, 총 폴리페놀 함량은 몽고황기 2년근, 4년근 및 6년근이 각각 45.3 mg/g, 71.3 mg/g 및 78.0 mg/g으로 황기에 비해 더 많은 양이 함유되어 있었으며, 총 플라보노이드 함량 또한 총 폴리페놀 함량과 마찬가지로 몽고황기가 더 많은 양의 총 플라보노이드를 함유하고 있었다. 기원식물별 추출물의 항산화활성 측정 결과, 황기에 비해 몽고황기의 DPPH radical 소거활성이 높았으며, 재배 연수별로는 몽고황기 4년근이 가장 활성이 높았고($IC_{50}$=3.54 mg/mL), 기원식물별 $ABTS^+$ radical 소거활성은 2년근을 제외한 4년근 및 6년근에서는 몽고황기의 $ABTS^+$ radical 소거활성이 높았다. 기원식물에 따른 NO 생성능은 재배기간이 동일한 경우 황기에 비해 몽고황기에서 NO 생성능이 더 높았다. 몽고황기는 모든 연근에서 무처리구에 비해 NO 생성량이 많았으며 특히, 6년근 에탄올 추출물의 NO 생성능이 2년근 및 4년근에 비해 높았으나, 황기는 재배연수에 따른 유의적인 차이는 나타나지 않았다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2509-2512
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• 2003

The active magnetic bearing(AMB) has statey-state error of the displacement by the external force. This paper presents a PID controller design using LQR method in the active magnetic bearing to compensate for the displacement by the external force.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.771-772
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• 2010

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.701-702
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• 2010