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Spin Hall Effect Induced by a Pd/CoFe Multilayer in a Semiconductor Channel
구현철,Jin-Seock Ma,장준연,김형준,한석희,엄종화,김철우 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
The spin Hall effect is observed for an InAs-based two-dimensional electron gas. Due to the spin Hall effect, the motion of the spin-polarized electrons deviates and causes a charge accumulation at the edge of the InAs channel. A spin imbalance between spin up and down is induced by spin injection from the Pd/CoFe multilayer, which is perpendicularly magnetized. This charge accumulation induces a transverse voltage in the absence of an external magnetic field. The observed spin Hall voltage decreases with increasing temperature and shows the same tendency as the spin diffusion length.
폐탄소나노튜브를 혼입한 전기전도성 발열 모르타르에 관한 기초 연구
구현철,김영환,정순식,장명수,문지훈,김운학 한국재난정보학회 2020 한국재난정보학회 학술대회 Vol.2020 No.11
본 논문에서는 폐기되는 탄소나노튜브에 탄소섬유를 추가로 시멘트 모르타르에 혼입하여, 전기전도성 갖는 발열 시멘트복 합체를 300×300×50mm3로 제작하여 저전압 DC24V이하에서 60분 동안 작동시 20℃이상의 온도발열이 되어 기존 다중벽 탄 소나노튜브와 혼입된 시멘트 복합체와 같은 발열 상태를 확인 하였다.
Gate Field Effect on Spin Transport Signals in a Lateral Spin-Valve Device
구현철,권재현,장준연,한석희,엄종화 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
The gate field effect on spin transport signals was detected in lateral ferromagnet-semiconductor hybrid devices. In the diffusive model, the change in the channel resistance induces a spin transport signal difference, but a non-local measurement shows that ΔR is almost constant with varying the gate voltage. The reason is that the spin diffusion length is slightly decreased with decreasing gate voltage due to the stronger spin-orbit interaction. At T = 20 K, the spin diffusion length can be decreased by 2.5 % by applying a gate voltage of -3 V. The gate field effect on spin transport signals was detected in lateral ferromagnet-semiconductor hybrid devices. In the diffusive model, the change in the channel resistance induces a spin transport signal difference, but a non-local measurement shows that ΔR is almost constant with varying the gate voltage. The reason is that the spin diffusion length is slightly decreased with decreasing gate voltage due to the stronger spin-orbit interaction. At T = 20 K, the spin diffusion length can be decreased by 2.5 % by applying a gate voltage of -3 V.
구현철,한재필,김익근,박인일,이주용,손경민,백광호,김진봉,김동준 대한소화기내시경학회 2006 Clinical Endoscopy Vol.33 No.2
이물질을 삼켜 내원하는 것은 흔하게 볼 수 있으며, 대부분에서 특별한 문제없이 배설된다. 그러나 일단 천공이 발생하게 되면, 심각한 상태나 사망까지 유발할 수 있는 합병증을 일으킬 수 있다. 더구나 이물질을 섭취한 것을 인지하지 못하는 경우가 있고 임상적 양상이 다양하여, 수술을 하기 전에는 진단 및 치료가 어려운 경우가 많다. 저자들은 본인도 모르게 섭취한 이쑤시개가 위벽과 간실질을 관통하여 이차적으로 발생한 간농양을, 내시경을 이용하여 간-위 누공을 통해 간농양 내로 돼지꼬리 카테터를 삽입하여 위 내 배농을 시행하였으며, 간농양이 호전되면서 자발적으로 위로 밀려나온 이쑤시개를 내시경적 방법으로 제거함으로써, 외과적 수술 없이 성공적으로 치료한 1예를 경험하였기에 문헌 고찰과 함께 보고하는 바이다. The ingestion of foreign bodies into the gastrointestinal tract is common, and most are passed out spontaneously without causing any problems. However, a perforation can cause a variety of complications involving considerable morbidity and mortality. Moreover, clinical presentation of a perforation can vary and patients are often unaware of the episode. Hence, a pre-operative diagnosis is difficult under these circumstances. We report an unusual case of a liver abscess that developed secondary to a toothpick that had penetrated the gastric wall and migrated to the liver. The liver abscess was treated successfully with internal drainage by inserting an endoscopic pigtail catheter through the hepato-gastric fistula. The toothpick was removed using an endoscopic snare. (Korean J Gastrointest Endosc 2006;33:94-99)
능동인덕터 사용에 따른 MMIC 주파수 변환기의 성능향상과 면적축소에 관한 연구
구현철,박정호 한국통신학회 1994 韓國通信學會論文誌 Vol.19 No.7
이 논문에서는 TV 튜너로 사용될 수 있는 MMIC 주파수 변환기를 설계하였다. MMIC를 설계한 때에 수동인덕터는 다른 수동소자나 능동소자에 비해서 그차지하는 면적이 매우 크고 원하지 않는 상호 간섭이 일어나 동작특성이 나빠지고 신뢰성과 재현성도 의심하지 않을 수 없다. 그러나 주파수 변환기에 사용되는 증폭기에 능동인덕터를 적용시키면 높은 안정성과 넓은 대역폭을 유지하게 된다. 믹서나 필터 등에도 능동정합을 이용하면 원하는 부분에서 높은 출력을 얻을 수 있다. 이 연구에서는 능동인덕터를 주파수 변환기에 적용하여 기존의 인덕터를 사용한 것과 비교하였다. 능동인덕터와 능동정합을 이용한 주파수 변환기가 기존의 것보다 면적에서 28.6% 줄이면서도 원하는 주파수 대역에서 더 큰 출력 신호를 얻을 수 있다. In this paper, a design of active inductors and their application in a frequency converter are proposed. In MMIC design, passive spiral inductor takes larger area than any other passive and active elements. A conventional spiral inductor generates undesired crosstalk, and its performance cannot have certainty and reproducibility. Meanwhile the active inductor eliminates these drawbacks, and operates for much wider bandwidth. Furthermore, its size is smaller and nearly independent of inductance. the performance of MMIC frequency converter with active inductors is directly compared with that of the frequency converters with spiral inductors. The size is 28.6% smaller with better performance in MMIC frequency converter.
1P-189 Preparation of thermo-sensitive hydrogel for drug delivery
구현철,한가득,손태일 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Stimuli-sensitive hydrogel has various types of pH-sensitive, thermosensitive, electric-sensitive and light-sensitive etc. The hydrogel which happen to physical or chemical change due to each external stimulus can be applied to a medical and cosmetic fields such as sustained release drug delivery, wound dressing, and skin care. Many studies have been carried out on application of drug delivery due to the characteristics of sensitive polymers to temperature. Some polymers such as Methoxypoly(ethylene glycol)-Poly(caprolactone)(mPEG-PCL), poly(lactic acid-co-glycolic acid)(PLGA-PEG-PLGA), and poly(ethylene oxide-propylene oxide-ethylene oxide) (PEO-PPO-PEO) have a reversible sol-gel phase transition at a specific temperature. For in vivo application, the phase transition temperature of the thermo-sensitive polymer was prepared to be 37°C, body temperature, and had fast gel formation time. The drug release time of prepared hydrogel was evaluated to suit the purpose of the drug.