• 대한전자공학회논문지TC
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• 제40권1호
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• pp.24-36
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• 2003

IMT-2000 서비스의 전송제한은 3GPP에 규정하고 있다. IS-95A 서비스보다 IMT-2000 서비스는 3배의 대역폭을 가짐으로 해서 Peak to Average가 높아졌고, 이 때문에 인접채널에 대한 영향을 줄이는 쪽으로 더 주위 깊게 설계하여야 하는 어려움이 발생하였다. 이러한 요소에 가장 민감하게 동작하는 모듈이 이동통신 시스템에 최종단에 위치하여 멀리까지 서비스를 가능케 하는 HPA(High Power Amplifier)이다. HPA는 Pl㏈ 근처에 동작시킴으로 인해 3차 5차 신호로 인해 인접채널에 영향을 미치며, 신호가 포화됨으로 인해 왜곡이 발생한다. 이에 HPA를 어떻게 선형화 시킬 수 있을 것이냐가 중요한 요소로써 작용하는데, 본 논문에서는 가장 복잡한 구조로 이루어져 있지만 선형화 방법에 있어 탁월한 개선 능력을 갖는 Feed-forward 방식을 설계 제작하였다. 본 논문은 Feed-forward의 1차 궤환부인 신호 제거 궤환부에서 얻어진 전류를 검출하여 알고리즘을 수행케 함으로써 환경변화에서도 무리 없이 동작하는 적응형 40Watt Feed-forward 선형화 증폭기가 되도록 하였다. 일반적인 RF 출력 신호를 검출하는 방식은 회로가 복잡하며, 합성기 출력에서 검출을 하기 때문에 신호검출의 정확성에서도 떨어지는 단점이 있다. 또한 선형화 증폭기의 최종 출력에서의 에러 신호를 감지하여 최적화시키는 알고리즘 역시 기존 방식인 Pilot 신호를 이용하지 않고 에러량 검출 방식을 적용하셔 W-CDMA용 선형화 증폭기가 되도록 하였다. 결과적으로 54㏈의 이득특성을 얻으면서 IW에서 40W 출력시까지 어느 동작에서도 30㎑ 대역폭 내에서 -26㏈m Max@3.515㎒ ACPR(Adjacent Channel Power Ratio) 특성, 48㏈c Max@±5㎒ ACLR (Adjacent Channel Leakage Power Ratio) 특성을 모두 만족하여 3GPP의 국제규격을 만족하는 선형화 증폭기가 되도록 하였다.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.3169-3175
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• 2011

본 논문에서는 가유전체 기판구조의 증가하는 유효 유전율 효과를 이용하여 방향성결합기를 소형화하여 설계하는 것에 대하여 기술한다. 방향성결합기는 RF 신호의 크기를 간접적으로 측정하거나 신호전력을 결합하는데 널리 사용되는 회로이다. 가유전체 기판구조는 다수의 도금된 비어홀에 의하여 표준형 기판보다 유효 유전율이 증가하는 특성을 지니는데, 이 특성이 바로 회로 소형화에 이용된다. 한 예로써 2GHz대에서 15dB의 결합계수를 갖는 방향성결합기가 표준형 기판과 가유전체 기판구조에 대하여 각각 설계되고 그 크기가 비교된다. 표준형 회로와 비교할 때, 가유전체 기판구조로 소형화된 방향성결합기는 동일한 성능을 유지하면서도 1/3로 줄어든 회로의 크기를 갖는다. 또한 소형화된 방향성결합기를 제작하여 측정한 성능은 예측 결과와도 매우 유사함을 보여준다. 측정한 성능 결과는 2GHz대에서 -14.62B의 결합도, -24.1dB의 정합도, -0.38dB의 삽입손실 특성을 보여준다.

• Journal of Ginseng Research
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• 제24권3호
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• pp.138-142
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• 2000

흰쥐 대뇌겉질로부터 별아교세포를 배양하여 흥분성아미노산인 L-glutamate에 의하여 유발되는 세포종창(astrocytic swelling)에 대한 ginsenosides의 억제효과를 검토하였다. Glutamate(0.5 mM)를 세포에 가하고 1시간동안 배양하면 swelling을 일으켜, 세포내의 물의 용적([$^3$H]OMG의 uptake량으로 측정)은 대조세포에 비하여 약 2배의 증가를 나타냈다. Glutamate와 함께 ginsenosides Rb$_2$와 Rc를 가하고 배양하면 glutamate에 의한 astrocytic swelling이 용량의존적으로 감소하였다. 세포는 Rb$_2$와 Rc(0.5 mg/ml)에 24시간까지 노출시켜도 MTT reduction이 감소하지 않는 것으로 보아 이 ginsenosides에 의한 swelling의 억제효과는 세포막의 손상에 의한 것이 아님을 알 수 있었다. Rb$_2$와 Rc는 glutamate에 의한 세포내 $Ca^{2+}$농도의 상승을 억제하였다. 따라서 Rb$_2$와 Rc는Ca$^{2+}$의 유입을 억제하므로서 glutamate에 의한 astrocytic swelling을 억제하는 것으로 생각된다.

• 동의생리병리학회지
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• 제21권1호
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• pp.62-69
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• 2007

To evaluate effect of CYTG on inhibiting the occurrence of arthritis, we performed the experiments including production of inflammatory cytokine and immunoglobulin in collagen arthritis model. The results were obtained as fellows. CYTG group showed inhibitory effect on arthritis incidence than control group for four weeks. Arthritis index of CYTG group reduced compared with control group. In CYTG group, production of cytokines which show suppressive effect on inflammation(IL-2, COX-2) was increased and which promotes inflammation(IL-10) was decreases in spleen. In CYTG group, production of immunoglobulin (IgG-RF) was reduced compared with control, and rate of CD3+CD69+T cell is lower in lymph node and CD4+CD25+ T cell is higher in lymph node and spleen. And synovial infiltration in the knee were observed in the controls (PBS-treated mice), whereas CYTG-treated mice exhibited significantly reduced histologic evidence of destruction and inflammation. So, the histopathological scoring average of CYTG group was 2.5 compared with control group(CIA mice) 4.5. It was thought that our data express high effect via immune system specially through the controling the inflammatory cytokines and immunoglobulins. CYTG could be usefully applied for the prevention and treatment of RA, and also is expected to be clinically helpful on the treatment of RA through modification.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.478-480
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• 2001

Fe-base amorphous films exhibit large saturation magnetostriction and soft magnetic Properties, which make them suitable for strain sensor applications. Most important material properties for the performance of these elements are the superior soft magnetic properties, such as high permeability and small coercive force, as well as magnetoelastic properties. It is well known that the strain generated in film deposition and/or post-heat treatment processes is one of important material properties, which effects on the soft magnetic properties of the film via magnetoelastic coupling. In this study, the effect of an isotropic strain in plane of magnetic films have been performed experimently. Amorphous films with the composition of (F $e_{90}$ $Co_{10}$)$_{78}$S $i_{l2}$ $B_{10}$ were employed in this study. The film with 5${\mu}{\textrm}{m}$ thick was deposed onto the polyimide substrate with 50${\mu}{\textrm}{m}$ thick by virtue of RF sputtering. The film was subject to post annealing with a static magnetic field with 500Oe magnetic field intensity at 35$0^{\circ}C$ for 1 hour. The polyimide substrate with the film was bonded with an adhesive on PZT piezoelectric substrate with 600${\mu}{\textrm}{m}$ thick in applying voltage of 500V. The change in MH loops of films due to the isotropic strain was measured by using VSM. The coercive force was evaluated from MH loops. It has shown in the results that M-H loops of films are subject to change considerably with a dc voltage, resulting of the magnetization rotation from normal to plane direction as the applied voltage is changed from 500V to 250V.50V.V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.326-326
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• 2010

The dielectric properties of continuous composition spreaded (CCS) $BaTiO_3-SrTiO_3$ (BST) thin filmsgrown at room temperature and annealed at different temperature ($350^{\circ}C$ and $550^{\circ}C$) were investigated. Moreover, electrical properties (leakage current and breakdown voltage) of CCS BST thin films were also investigated. The aluminum top-electrode, sized by $200{\times}200\;{\mu}m2$ and apart from each other by $300\;{\mu}m$, were deposited on the CCS BST thin films by the DC sputtering system. The dielectric properties of the CCS BST thin films were significantly influenced depending on the distance from $BaTiO_3$ and $SrTiO_3$ targets which was attributed to the $BaTiO_3-SrTiO_3$ composition ratio. The maps of dielectric constants and loss tangents were plotted via $1500\;{\mu}m$ - step measuring. The specific points showing the dielectric constant (k: ~300) and loss tangent (tand: ~0.008) at 1 MHz were found.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.300-300
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• 2008

In this study, the advanced DuoPIGatron-type ion beam (IB) system was applied to inorganic thin film for aligning liquid crystal (LC). LC alignment on $Ta_2O_5$ via IB irradiation was embodied. As a result of IB irradiation, the homogeneously aligned liquid crystal display (LCD) on $Ta_2O_5$ was observed with low pretilt angles. The $Ta_2O_5$ were deposited on indium-tin-oxide coated Coming 1737 glass substrates by rf magnetron sputtering at $200^{\circ}C$. The deposition process resulted in forming very uniform thin film on glass substrates without any defects. To confirm the application of the inorganic alignment on modem display optical devices, we fabricated twisted nematic LCD and measured optical property and response time. As a result of the experiment, the electro optical characteristics of the LCD fabricated by using IB irradiation on $Ta_2O_5$ alignment layer were similar with the other LCD fabricated by using rubbing process.

• 마이크로전자및패키징학회지
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• 제17권2호
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• pp.35-40
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• 2010

CCS방법이 적용된 off-axis RF 마그네트론 스퍼터를 이용하여 증착된 $Ta_2O_5-SiO_2$의 유전체 박막에 관하여 연구를 하였다. 1500 ${\mu}m$ 의 간격으로 비유전율 및 유전손실을 측정하여 $Ta_2O_5-SiO_2$에 조성의 변화에 따른 유전특성의 변화를 나타내었다. 1MHz 에서 높은 유전상수(k~19.5) 와 낮은 유전손실(tan${\delta}$<0.05)을 보이는 영역들을 찾았는데, 이는 증착된 기판($75{\times}25mm^2$ sized Pt/Ti/$SiO_2$(100))에서 $SiO_2$/Si 타겟 영역으로부터 각각 16 mm, 22 mm 떨어진 영역에서 찾을 수 있었다.

• 반도체디스플레이기술학회지
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• 제9권1호
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• pp.41-47
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• 2010

The effects of thermal treatment on CNTs, which were coated with a-$CN_x$ thin film, were investigated and related to variations of chemical bonding and morphologies of CNTs and also properties of field emission induced by thermal treatment. CNTs were directly grown on nano-sized conical-type tungsten tips via the inductively coupled plasma-chemical vapor deposition (ICP-CVD) system, and a-$CN_x$ films were coated on the CNTs using an RF magnetron sputtering system. Thermal treatment on a-$CN_x$ coated CNT-emitters was performed using a rapid thermal annealing (RTA) system by varying temperature ($300-700^{\circ}C$). Morphologies and microstructures of a-$CN_x$/CNTs hetero-structured emitters were analyzed by FESEM and HRTEM. Chemical composition and atomic bonding structures were analyzed by EDX, Raman spectroscopy, and XPS. The field emission properties of the a-$CN_x$/CNTs hetero-structured emitters were measured using a high vacuum (below $10^{-7}$ Torr) field-emission measurement system. For characterization of emission stability, the fluctuation and degradation of the emission current were monitored in terms of operation time. The results were compared with a-$CN_x$ coated CNT-emitters that were not thermally heated as well as with the conventional non-coated CNT-emitters.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.41-45
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• 2016

The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.