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하이퍼 큐브네트워크를 이용한 Radiance Estimation 프로세서의 설계
류현우,김영진,이현수 경희-다반 ASIC 설계교육센터 2005 경희-다반 ASIC센터 논문집 Vol.6 No.-
본 논문에서는 Radiance Estimation 연산에 존재하는 전역적인 병렬성을 처리할 수 있는 구조를 제안한다. 기존의 소프트웨어 처리는 계산에 필요한 많은 연산의 시간이 필요로 하기 메문에 하드웨어 적인 구현의 필요성이 증대하였다. Radiance Estimation 알고리즘의 병렬성을 이용하여 SIMD 처리 방식으로 설계를 하였으며 연산의 단위인 Cell의 통신은 4차인 하이퍼 큐브 네트워크를 이용하여 데이터간의 효율성은 높였다. 그리고 연산의 신호에 따라 다양한 기능을 하는 Cell로 구성을 하여 Radiance Estimation 연산의 Photon 검색과 밀도추정 연산을 하나의 시스템에서 적용이 가능하였다.
고밀도 평판형 유도결합 BCl<sub>3</sub>/SF<sub>6</sub> 플라즈마를 이용한 GaAs/AlGaAs와 InGaP 반도체의 선택적 식각에 관한 연구
유승열,류현우,임완태,이제원,조관식,전민현,송한정,이봉주,고종수,고정상,Yoo Seungryul,Ryu Hyunwoo,Lim Wantae,Lee Jewon,Cho Guan Sik,Jeon Minhyon,Song Hanjung,Lee BongJu,Ko Jong Soo,Go Jeung Sang,Pearton S. J. 한국재료학회 2005 한국재료학회지 Vol.15 No.3
We investigated selective dry etching of GaAs over AlGaAs and InGaP in high density planar inductively coupled $BCl_3/SF_6$ plasmas. The process parameters were ICP source power (0-500 W), RE chuck power (0-30W) and gas composition $(60-100\%\;BCl_3\;in\;BCl_3/SF_6)$. The process results were characterized in terms of etch rate, selectivities of GaAs over AlGaAs and InGaP, surface morphology, surface roughness and residues after etching. $BCl_3/SF_6$ selective etching of GaAs showed quite good results in this study. Selectivities of GaAs $(GaAs:AlGaAs\~36:1,\;GaAs:InGaP\~45:1)$ were superior at $18BCl_3/2SF_6$, 20 W RF chuck power, 300 W ICP source power and 7.5 mTorr. Addition of $(5-15\%)SF_6\;to\;BCl_3$ produced relatively high selectivities of GaAs over AlGaAs and InGaP during etching due to decrease of etch rates of AlGaAs and InGaP (boiling points of etch products: $AlF_3\~1300^{\circ}C,\;InF_3>1200^{\circ}C$ at atmosphere) at the condition. SEM and AFM data showed slightly sloped sidewall and somewhat rough surface$(RMS\~9nm)$. XPS study on the surface of processed GaAs proved a very clean surface after dry etching. It shows that planar inductively coupled $BCl_3/SF_6$ plasmas could be a good candidate for selective dry etching of GaAs over AlGaAs and InGaP.
경피적 관상동맥 중재술과 관상동맥 우회술 후의 심폐 운동능력 비교
김철,류현우,박윤경,방인걸,김영주 대한재활의학회 2008 Annals of Rehabilitation Medicine Vol.32 No.4
Objective: To compare the exercise capacity after cardiac rehabilitation (CR) in patients with percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery. Method: 27 patients who underwent PCI and 18 patients who underwent CABG surgery were included. All the subjects performed supervised exercise training for 6∼8 weeks at hospital and self-exercise at community for additional 16~18 weeks. Exercise capacity was measured by symptom limited graded exercise tests at study entry and 6 months later. Results: After 6 months of CR, maximal oxygen consumption (VO2max) was significantly increased, resting heart rate (HR) and submaximal rate pressure product (RPP) were significantly decreased in both groups (p<0.05). There were no significant change of maximal HR in both groups (p<0.05). Maximal RPP in CABG increased significantly (p<0.05) but did not change significantly in PCI group. Resting HR was significantly higher, VO2max was significantly lower in CABG group than PCI group at study entry (p<0.05). Resting HR was not significantly different in both groups but, VO2max was still lower in CABG group than PCI group even after 6 months of CR (p<0.05). Conclusion: The cardiac rehabilitation program was effective in both PCI and CABG group. Although VO2max in PCI group was higher than CABG group after 6 month CR, the range of improvement was greater in CABG group than PCI group. Objective: To compare the exercise capacity after cardiac rehabilitation (CR) in patients with percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery. Method: 27 patients who underwent PCI and 18 patients who underwent CABG surgery were included. All the subjects performed supervised exercise training for 6∼8 weeks at hospital and self-exercise at community for additional 16~18 weeks. Exercise capacity was measured by symptom limited graded exercise tests at study entry and 6 months later. Results: After 6 months of CR, maximal oxygen consumption (VO2max) was significantly increased, resting heart rate (HR) and submaximal rate pressure product (RPP) were significantly decreased in both groups (p<0.05). There were no significant change of maximal HR in both groups (p<0.05). Maximal RPP in CABG increased significantly (p<0.05) but did not change significantly in PCI group. Resting HR was significantly higher, VO2max was significantly lower in CABG group than PCI group at study entry (p<0.05). Resting HR was not significantly different in both groups but, VO2max was still lower in CABG group than PCI group even after 6 months of CR (p<0.05). Conclusion: The cardiac rehabilitation program was effective in both PCI and CABG group. Although VO2max in PCI group was higher than CABG group after 6 month CR, the range of improvement was greater in CABG group than PCI group.
강정훈,한용,류현우 대한근전도전기진단의학회 2013 대한근전도 전기진단의학회지 Vol.15 No.1
계류척수 증후군(Tethered cord syndrome)은 척수의 신장과 척수 종말끈의 비후 등으로 척수가 견인되면서 신경학적 이상을 일으키는 질환으로 대부분의 증상은 청소년기 이전에 발생한다. 본 증례는 마르팡 증후군을 가진 49세의 여성에서 요추부 자기공명영상 검사 상 마르팡 증후군에 의한 경막낭의 팽창과 함께 계류척수 증후군이 동반되어 관찰되었으나 40대 후반까지 특별한 신경학적 증상이 나타나지 않았던 경우이다.
전계방출원으로의 적용을 위한 다양한 탄소나노튜브의 이온조사 효과 분석
김창득,강준태,김대준,김홍정,류현우,박선미,송윤호,이의완,이창섭,이형락,정진우 한국물리학회 2007 새물리 Vol.55 No.5
The effect of argon-ion irradiation on the field emission and the luminescent properties of various types of screen-printed carbon nanotubes (SWNT, DWNT, MWNT, CNF) with square pixels was investigated to further improve field-emission-display (FED) applications of CNTs. Persistent problems associated with screen-printed CNTs, such as bent and/or buried CNTs and degradation in the binder-residue-induced emission, were improved as a result of the permanent straightening of CNTs and of protruding CNTs from binders caused by the irradiation treatment and the resulting surface cleaning effect. These findings in suggest that ion irradiation treatment is an effective method for achieving uniform field emission and reducing the aging effect of screen-printed CNTs using SWNTs and DWNTs. 다양한 탄소나노튜브 및 탄소나노섬유의 전계방출원 응용을 위한 이온조사 효과를 확인하였다. 전계방출원으로 사용된 탄소나노튜브는 단중벽 탄소나노튜브, 이중벽 탄소나노튜브, 다중벽 탄소나노튜브 및 탄소나노섬유로 제작 된 바인더를 이용하여 스크린 프린팅법으로 제작하였다. 이온조사는 DC 전원을 이용한 Ar 플라즈마를 사용하였다. 각각의 바인더로 제작된 전계방출원을 일정한 시간 동안 이온조사 후 SEM (scanning electron microscope) 이미지를 통하여 그 상태들을 확인하고 전계방출 특성 및 발광 특성을 확인하였다. Ar 이온조사가 대부분의 전계방출원에 큰 효과를 미침을 확인하였다.
김창득,이형락,강준태,김영진,김종욱,류현우,이성엽,허재원 한국물리학회 2007 새물리 Vol.54 No.2
Large arrays of self-oriented, multi-wall carbon nanotubes (MWNTs) have been obtained using chemical vapor deposition. We controlled the size of the catalytic Fe nanoparticles to control the wall number of the carbon nanotubes (CNTs). The sizes and the special distribution of the Fe nanoparticles varied with the growth temperature, the heat exposure time, and the thickness of the catalytic metal layer, resulting in a change in the wall number of the grown CNTs. With decreasing in heat exposure time from 10 to 0 sec, the average wall number of the CNTs decreased. A combination of atomic force microscop (AFM), scanning electron microscop (SEM), and transmission electron microscop (TEM) provided evidence for the crucial role of the surface distribution of the metallic catalyst particles on the substrate during the growth of the CNT. The CNT growth was performed at 800 ${^\circ}$C for 10 min by using thermal chemical vapor deposition (T-CVD). We succeeded in growing vertically aligned small-wall CNTs. For use with the X-ray gun, the CNTs were synthesized on a 5 mm-diameter sus plate. 열화학 기상합성법을 이용하여 수직배향된 MWNT를 합성하였다. 우리는 탄소나노튜브 (CNT : carbon nanotube)의 벽수조절을 위하여 Fe촉매를 나노사이즈로 조절하였다. Fe 나노 촉매의 사이즈와 분포는 합성 온도, 열 노출 시간과 촉매 금속의 두께에 따라 다양하게 존재하고 이것은 합성된 CNT의 벽수를 바꾸어 준다. 열 노출 시간이 10 sec에서 0 sec로 줄어들수록 CNT의 평균 벽수는 줄어든다. AFM (atomic force microscope), SEM (scanning electron microscope), TEM (transmission electron microscope) 측정에 의한 결과는 기판 위 CNT 합성과정에서 금속촉매 입자의 표면분포의 결정적인 증거가 된다. CNT합성은 열화학기상합성 장치 내에서 800 $^\circ$C로 10분 동안 이루어 졌다. 우리는 벽수가 적은 CNT들을 합성하는데 성공했다. 합성 되어진 CNT를 X-선 총으로 사용하기 위하여 지름이 5 mm인 스테인레스 기판 위에 합성하였다.