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뉴로내비게이션 시스템 표면정합에 대한 병변 정합 오차의 회전적 특성 분석: 팬텀 연구
박현준,문정환,유학제,신기영,심태용,Park, Hyun-Joon,Mun, Joung Hwan,Yoo, Hakje,Shin, Ki-Young,Sim, Taeyong 대한의용생체공학회 2016 의공학회지 Vol.37 No.2
In this study, we investigated the rotational characteristics which were comprised of directionality and linearity of target registration error (TRE) as a study in advance to enhance the accuracy of contour-based registration in neuronavigation. For the experiment, two rigid head phantoms that have different faces with specially designed target frame fixed inside of the phantoms were used. Three-dimensional coordinates of facial surface point cloud and target point of the phantoms were acquired using computed tomography (CT) and 3D scanner. Iterative closest point (ICP) method was used for registration of two different point cloud and the directionality and linearity of TRE in overall head were calculated by using 3D position of targets after registration. As a result, it was represented that TRE had consistent direction in overall head region and was increased in linear fashion as distance from facial surface, but did not show high linearity. These results indicated that it is possible for decrease TRE by controlling orientation of facial surface point cloud acquired from scanner, and the prediction of TRE from surface registration error can decrease the registration accuracy in lesion. In the further studies, we have to develop the contour-based registration method for improvement of accuracy by considering rotational characteristics of TRE.
뜬 마이크로 디바이스를 이용한 Ge-Si<SUB>x</SUB>Ge<SUB>1-x</SUB> Core-Shell Nanowires 의 열전도율 측정
박현준(Hyun Joon Park),나정효(Jung hyo Nah),Emanuel Tutuc,설재훈(Jae Hun Seol) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.10
나노선에서 코어-셸 헤테로 구조를 도입함으로써 열 전도율을 낮출 수 있으며, 이로 인해 열전 효율(ZT)을 향상시킬 수 있다는 것이 이론 연구를 통해 제안되었다. 본 논문에서는 코어-셸 나노선의 열전도율 감소를 실험적인 방법을 통해 확인하였다. 화학증기 증착법을 통해 만든 게르마늄-규소 x 게르마늄 1-x(Ge?SixGe1-x) 코어-셸 나노선의 열전도율을 마이크로 크기의 뜬 디바이스를 이용하여 측정하였다. 셸에서 측정된 실리콘의 함유율(x)는 0.65 로 확인하였으며, 게르마늄은 코어와 셸 사이에서, 격자 불일치(lattice mismatch)에서 비롯된 결점(defect)와 같은 역할을 한다. 또한, 4-point I-V 측정실험에, 휘트스톤 브릿지 실험을 추가 진행함으로써 측정 민감도를 강화하였다. 측정된 열전도율은 상온에서 9~13 W/mK 으로써, 비슷한 지름을 가지는 게르마늄 나노선과 비교하였을 때, 열전도율이 약 30 % 낮아졌음을 확인하였다. Theoretical calculations suggest that the thermoelectric figure of merit (ZT) can be improved by introducing a core-shell heterostructure to a semiconductor nanowire because of the reduced thermal conductivity of the nanowire. To experimentally verify the decrease in thermal conductivity in core-shell nanowires, the thermal conductivity of Ge?SixGe1-x core-shell nanowires grown by chemical vapor deposition (CVD) was measured using suspended microdevices. The silicon composition (Xsi) in the shells was measured to be about 0.65, and the remainder of the germanium in the shells was shown to play a role in decreasing defects originating from the lattice mismatch between the cores and shells. In addition to the standard four-point current? voltage (I-V) measurement, the measurement configuration based on the Wheatstone bridge was attempted to enhance the measurement sensitivity. The measured thermal conductivity values are in the range of 9? 13 W/mK at room temperature and are lower by approximately 30 than that of a germanium nanowire with a comparable diameter.
결정화 CeO2-Na2O-SiO2 유리의 소수성 거동에 대한 연구
박현준 ( Hyun Joon Park ),김영석 ( Young Seok Kim ),김종환 ( Jong Hwan Kim ),김일구 ( Il Gu Kim ),정재엽 ( Jae Yeop Jung ),최수연 ( Su Yeon Choi ),류봉기 ( Bong Ki Ryu ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.4
Metal atoms in rare-earth oxides (REOs) have a different electronic structure, where the unfilled 4f orbitals are shielded from interactions with the surrounding environment by the full octet of electrons in the 5 s2 p6 outer shell. Thus, these metal atoms would have a lower tendency to exchange electrons and form a hydrogen bond with interfacial water molecules. In this study, we have prepared (10+x)CeO2-30Na2O- (60-x)SiO2 (in mol%, x=0,5,10) glass system and examined the characterization of hydrophobicity behavior of crystallized Na2O-SiO2 glass containing CeO2. In addition, we confirmed the change in the wettability of the glass surface due to change the heat treatment time for crystallization and a change amount of CeO2. It was found that the contact angles of crystallized specimens (CNS glasses) got higher by about 40~50° by the addition of CeO2 and 0~18 hr-heating, compared with the specimens without CeO2 and 0~8 hr heat treatment. In order to explain the hydrophobicity behavior of CNS glasses, surface structure through FT-IR ATR ranging from 3000 cm-1 to 4000 cm-1 was examined. The band characteristic of -OH bridges at about 3200 cm-1, 3400 cm-1 and 3600 cm-1 are attributed to the existence of hydrogen bond. At 3700 cm-1, as the intensity of peaks (0.006~0.036) gets higher, the contact angles increase by 51° to 73°. (Received July 1, 2013)