• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2003년도 하계학술대회
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• pp.269-271
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• 2003

초고주파/밀리미터파 대역에서 전력증폭기의 효율을 향상시키기 위해 MEMS 튜닝회로를 설계하였다. MEMS 튜닝회로의 효과를 확인하기 위해 2차 및 3차 고조파를 억제할 수 있도록 3-stub Class-E 증폭기를 설계하였으며 또한 설계된 증폭기에 대해 시뮬레이션을 실시하였다. 시뮬레이션의 결과로서 8GHz에서 14dBm입력에 대해 MEMS가 적용된 증폭기의 성능은 PAE=66 9%, drain efficiency=75.89%, 그리고 출력 P=23.37 dBm을 얻었다. 또한 FET의 기생리액턴스의 변화에 대해서 MEMS 튜닝회로의 효율증대효과를 확인하였다. 결론적으로 이 연구에서 제안된 새로운 방법을 통해 증폭기의 효율향상을 위한 효과적인 방법이 될 수 있음 보여 주었다.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1697-1704
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• 2001

A finite element model for polarization switching in electro-mechanically coupled materials is proposed and applied to predict the switching behavior of a two-dimensional ferroelectric ceramic. A complicated micro-structure existing in the material is modeled as il continuum body and a simple 3 node triangle finite element with nodal displacement and voltage degrees of freedom is used for a finite element analysis. The elements use nonlinear constitutive equations, switching criterion and kinetic relation, fur representation of material response at strong electric and stress fields. The polarization state of the material is represented by internal variables in each element, which are updated at each simulation step based on the proposed constitutive equations. The model reproduces strain and electric displacement hysteresis loops observed in the material.

• Journal of Plant Biotechnology
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• 제30권2호
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• pp.185-188
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• 2003

In order to enhance shoot elongation and rooting of Anthurium andreanum 'Atlanta' in vitro, 15mL of liquid media containing various concentrations of activated charcoal, sucrose and MS salts were added in same vessels after small shoots were induced from the calli on mudium supplemented with 10.0mg/L BA and 0.1mg/L 2.4-D. The post-supplying of 15mL liquid medium containing MS macro and micro elements, 30g/L sucrose and 5.0∼10.0g/L activated charcoal was significantly stimulated the shoot elongation and rooting of regenerated shoots from calli. The medium addition was also resulted in the enhanced soil survival, elongation and rooting of plantlets in cultural soil mixed with perlite and vermiculite(1 : 1)

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 동계학술발표회 논문집
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• pp.199-200
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• 2007

UV 처리 광학 접착제를 가지고 단일 포토리소그라피 공정을 사용하여 마이크로 렌즈를 제작하였다. 먼저 유리판 위에 자외선 처리 광학 접착제를 코팅 한 후 UV 노광하고 아세톤에서 현상 후 핫플레이트에서 유리전이 온도 이상에서 열적 재흐름이 일어나도록 하여 마이크로 렌즈를 만드는데 성공하였다 이를 실제 LED 소자 위에서 마이크로 렌즈를 만들어 보고 LED의 외부 추출 효율이 높아지는지를 실험하였다. 또한 기존의 UV 처리 광학 접착제에 나노 입자을 첨가하여 굴절률을 더 높여 마이크로 렌즈를 만드는 실험을 하였다.

• 한국정밀공학회지
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• 제18권3호
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• pp.115-121
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• 2001

In micro automation technology, the concurrent realization of a high resolution and a large operating rage has been achieved by a dual actuator, usually called by piggy-back system, conventionally. But, because of its manufacturing cost, the complexity of control, and the limit of overall bandwidth, the contract-free and single servo actuators have been suggested with specific applications. In this paper, we suggest a novel non-contact surface actuator suing combination of the Lorentz force and the magnetized force, and discuss the actuating principles including an analytical approach. Differently from the existing planar system, an operating range of the suggested system can be expanded by an additional attachment of active elements. Therefore, it is estimated to be suitable for the next-generation moving system.

• 대한치과기공학회지
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• 제24권1호
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• pp.65-71
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• 2002

This study was performed to observe the microhardness change of the surface and the bonding strength between the porcelain and alloy specimens in order to investigate the effects of appended indium, tin and copper on interfacial properties of Au-Pd-Ag alloys. The hardness of castings was measured with a micro-Vicker's hardness tester. The interfacial shear bonding strength between alloy specimen and fused porcelain was measured with a mechanical testing system(MTS 858.20). The microhardness of Au-Pd-Ag alloy was increased by adding indium and tin, but not increased by adding copper. The shear bonding strength of Au-Pd-Ag-Sn alloy and Au-Pd-Ag-Cu alloy showed 87MPa, 57MPa. The higher concentration of adding elements showed the higher shear bonding strength.

• Asian-Australasian Journal of Animal Sciences
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• 제14권4호
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• pp.564-566
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• 2001

A study was undertaken to record the utilization of some micro-elements during inflammation of the mammary gland. Two groups of twenty five animals each suffering from subclinical and clinical mastitis were selected for the study. All the animals were maintained on identical diets. Blood zinc level in cows with subclinical mastitis ($5.66{\pm}0.52$) was significantly (p<0.05) lower than that of healthy cows ($8.46{\pm}1.10ppm$). No significant difference was, however, recorded in blood copper and cobalt levels between healthy and mastitic cows.

• 한국주조공학회지
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• 제16권2호
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• pp.149-157
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• 1996

Several aluminum based alloys were fabricated by a twin roll strip casting mill. As-cast microstructures and microsegregations of these aluminum alloys were investigated by means of optical microscope, scanning electron microscope and electron probe micro analysis. Clear distinction on microsegregation among the alloy systems was observed, that is, A1235 and A8011 alloys showed diffused segregation in the middle of the strip, while A3003 and A5086 alloys revealed a centerline segregation consisted of lamellar structure. Above center line segregation was resulted from enrichment of the alloying elements such as Mn, Fe, Cu, Si and eutictic reaction in central region of the alloy strip.

• 전력전자학회논문지
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• 제6권2호
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• pp.217-221
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• 2001

본 논문에서는 통신기기와 같은 저용량 부하를 위한 APLC를 설계하였다. APLC는 부하와 병렬로 위치하여 부하에 필요한 무효전력 성분만을 공급함으로 운전 효율을 향상시켰으며 히스테리스 제어기를 마이크로 프로세서와 아날로그 회로를 이용하여 구현하여 저가형 제어기를 구현하였다. 컴퓨터 시뮬레이션을 통해서 보상 시스템의 특성을 해석하였으며 또한 실험에 의해 제안된 APLC제어기가 고조파 저감 및 역률 개선을 수행하고 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1953-1955
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• 2002

An efficient automatic mesh generator suitable for the harsh model, which contains abrupt regions and thin layers, is implemented. It adopts two kinds of node placement scheme. In the beginning, the initial nodes on the boundary are generated automatically by an efficient boundary node generation scheme. And then the inner nodes are placed using nodal spacing value technique repeatedly from the initial mesh to final mesh. The effectiveness of the proposed technique is verified by a thin film micro-strip line modeling, where the final mesh contains no sliver elements.