http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Compton Imaging Simulator를 이용한 다층 구조 컴프턴 카메라 성능평가 예비 연구
이세형,박성호,서희,박진형,김찬형,이주한,이춘식,이재성,Lee, Se-Hyung,Park, Sung-Ho,Seo, Hee,Park, Jin-Hyung,Kim, Chan-Hyeong,Lee, Ju-Hahn,Lee, Chun-Sik,Lee, Jae-Sung 한국의학물리학회 2009 의학물리 Vol.20 No.2
컴프턴 카메라는 컴프턴 산란현상의 기하학적 해석을 통해 감마선원의 3차원적 위치분포를 고정된 위치에서 찾아내는 신개념의 감마선 영상장치이다. 기존의 감마선 영상장치에서는 필수적으로 사용되는 기계적 집속기를 사용하지 않기 때문에 높은 영상 감도를 제공할 수 있으며, 다중 추적자 기능을 제공한다는 장점이 있어 차세대 감마선 영상장치로서 주목을 받고 있다. 본 연구에서는 Geant4 몬테칼로 전산모사 툴키트를 이용하여 사용자 친화형의 컴프턴 카메라 시뮬레이터를 개발하였다. 시뮬레이터의 정확성을 검증하기 위하여 한양대학교에서 개발 중인 이중 산란형 컴프턴 카메라의 실험 결과와 비교하였다. 영상 해상도의 경우 선원의 에너지가 높아짐에 따라 해상도가 향상되는 동일한 경향을 보였으나, 시뮬레이터 결과에서 약 1 mm 정도 우수하게 평가되었다. 영상 감도의 경우 실험에서 2~3배 정도 높게 평가되었다. 이러한 결과들은 우연 동시반응에 기인한 것으로, 실험에서 획득한 유효반응들은 전산모사와는 달리 우연한 동시계수에의한 데이터가 상당수 포함되어 있기 때문에 영상 해상도는 상대적으로 저조하고, 영상 감도는 높게 나타난 것으로 판단된다. 개발된 시뮬레이터를 이용하여 새로운 구조의 컴프턴 카메라에 대한 성능을 평가하였다. 단일 산란형 컴프턴 카메라의 경우 산란부를 다층 구조로 개발할 때 4대의 산란부 검출기를 사용하는 것이 최상의 성능을 보이는 것으로 평가되었고, 그 이상 사용할 경우 성능이 오히려 저하됨을 확인하였다. A Compton camera, which is based on the geometrical interpretation of Compton scattering, is a very promising gamma-ray imaging device considering its several advantages over the conventional gamma-ray imaging devices: high imaging sensitivity, 3-D imaging capability from a fixed position, multi-tracing functionality, and almost no limitation in photon energy. In the present study, a Monte Carlo-based, user-friendly Compton imaging simulator was developed in the form of a graphical user interface (GUI) based on Geant4 and $MATLAB^{TM}$. The simulator was tested against the experimental result of the double-scattering Compton camera, which is under development at Hanyang University in Korea. The imaging resolution of the simulated Compton image well agreed with that of the measured image. The imaging sensitivity of the measured data was 2~3 times higher than that of the simulated data, which is due to the fact that the measured data contains the random coincidence events. The performance of a stacking-structure type Compton camera was evaluated by using the simulator. The result shows that the Compton camera shows its highest performance when it uses 4 layers of scatterer detectors.
용액공정 ZnO/SnO₂ 박막 트랜지스터에 대한 몰비 및 열처리 조건의 영향
이세형(Se-Hyeong Lee),이정석(Jeongseok Lee),김유종(Yoojong Kim),우경완(Kyoung-Wan Woo),박소영(So-Young Bak),이상현(Sang-Hyun Lee),이문석(Moonsuk Yi) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
Conventional solution-processed ZTO thin film transistors(TFTs) had a thermal limitation that a high process temperature was required for deposition of a channel layer. To overcome these thermal limitations, we deposited a channel layer with a ZnO/SnO₂ structure and obtained optimal values by adjusting the molar ratio of ZnO and SnO₂ layers and annealing conditions. In conclusion, we fabricated ZnO/SnO₂ TFTs with similar performance to ZTO TFTs at a low process temperature. The optimized ZnO/SnO₂ TFTs exhibited the on/off ratio, saturation mobility, threshold voltage and subthreshold swing(S.S) of 1.26×105, 1.44cm2/V·s, +4.00V, 2.93V/dec, respectively.
이정석(Jeongseok Lee),이세형(Se-Hyeong Lee),김유종(Yoojong Kim),우경완(Kyoung Wan Woo),박소영(So-Young Bak),이상현(Sang-Hyun Lee),이문석(Moonsuk Yi) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
Zinc and Tin composite nanostructures were fabricated as gas sensors on the interdigitated ITO (Indium Tin Oxide) electrodes. Zinc oxide (ZnO) and Tin dioxide (SnO₂) nanostructures were grown at 900℃ in the Vapor-Liquid-Solid(VLS) growth mechanism in a furnace. FE-SEM images in Figure 1 illustrated the composite nanostructures of ZnO-SnO₂, called “Nano-vine”. The normal metal catalysts such as Au and Cu were replaced with the Tin in the ITO electrodes. The Nano-vine was partially more sensitive in the detection sensitivity of noxious gases such as NO₂, CO and NH3 than that produced by nanostructures using Zn or Sn single material powders.
Sol-Gel 방법으로 제작된 SnO<sub>2</sub> seed layer를 적용한 고반응성 ZnO 가스 센서
김상우 ( Sangwoo Kim ),박소영 ( So-young Bak ),한태희 ( Tae Hee Han ),이세형 ( Se-hyeong Lee ),한예지 ( Ye-ji Han ),이문석 ( Moonsuk Yi ) 한국센서학회 2020 센서학회지 Vol.29 No.6
A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO<sub>2</sub> nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO<sub>2</sub> seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO<sub>2</sub> seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.
SnO<sub>2</sub> 나노와이어를 이용한 저온동작 고감도 고선택성 NO<sub>2</sub> 가스센서
김유종 ( Yoojong Kim ),박소영 ( So-young Bak ),이정석 ( Jeongseok Lee ),이세형 ( Se-hyeong Lee ),우경완 ( Kyoungwan Woo ),이상현 ( Sanghyun Lee ),이문석 ( Moonsuk Yi ) 한국센서학회 2021 센서학회지 Vol.30 No.3
In this paper, methods for improving the sensitivity of gas sensors to NO<sub>2</sub> gas are presented. A gas sensor was fabricated based on an SnO<sub>2</sub> nanowire network using the vapor-phase-growth method. In the gas sensor, the Au electrode was replaced with a fluorinedoped tin oxide (FTO) electrode, to achieve high sensitivity at low temperatures and concentrations. The gas sensor with the FTO electrode was more sensitive to NO<sub>2</sub> gas than the sensor with the Au electrode: notably, both sensors were based on typical SnO<sub>2</sub> nanowire network. When the Au electrode was replaced by the FTO electrode, the sensitivity improved, as the contact resistance decreased and the surface-to-volume ratio increased. The morphological features of the fabricated gas sensor were characterized in detail via field-emission scanning electron microscopy and X-ray diffraction analysis.