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광반응 재료가 코팅된 단주기 광섬유격자 기반 자외선센서의 광민감도 향상 연구
김우영,김찬영,김현경,안태정,Kim, Woo Young,Kim, Chan-Young,Kim, Hyun-Kyoung,Ahn, Tae-Jung 한국광학회 2015 한국광학회지 Vol.26 No.2
This study was focused on developing an optical sensor that monitors ultraviolet (UV) light. Recently, we proposed and demonstrated a novel, highly sensitive UV sensor based on a fiber Bragg grating (FBG). To ensure that the incident UV light is focused on the FBG surface, the sensor was coated with an azobenzene polymer material that acts as a UV-induced stretchable functional material, in combination with a cylindrical focal lens. In this study we have improved the sensitivity of the sensor by employing a cylindrical focal mirror as a curved reflector, to refocus the UV light passing through the FBG. We considered the performance of several different types of reflectors and chose the optimal radius of curvature for the reflector. Compared to the UV sensor without an auxiliary device, the sensitivity of the FBG sensor with a focal lens and a curved reflector was 15 times as high. 본 논문은 자외선 광학센서 개발에 관한 것이다. 기존에 반도체 기반 자외선 센서를 대체하기 위해 개발된 단주기 광섬유격자기반 자외선 센서에 대한 측정 민감도를 향상시키기 위한 다양한 장치들을 설계하고 실험을 통해 성능을 확인하였다. 최근 연구를 통해 자외선 흡수에 따라 인장력이 유도되는 아조벤젠 폴리머 재료와 장력에 따른 광섬유격자 특성 변화를 조합하여 새로운 자외선 센서의 개념이 제시되었다. 본 연구에서는 광섬유격자 기반 자외선 센서에서 흡수하지 못하고 통과되는 자외선 잔광을 반사판을 이용해서 다시 반사시켜 센서에서 재흡수되는 원리로 센서의 민감도를 향상시켰다. 본 논문에서는 반사판의 종류를 선정하고 반사판의 곡률반경을 최적화하였다. 또한 기존의 원통형 집광렌즈를 이용한 민감도 향상 기술을 접목 시켜 아무런 장치가 없을 때와 비교해서 약 15배의 성능을 향상시키는 결과를 얻었다. 또한 외부 환경 효과를 줄이기 위한 패키지 모듈을 제작하여 적용하고 그 특성을 분석하였다.
한의학적 치료법으로 호전된 요추 추간판 탈출증 환자의 영상의학적 변화
김우영,한상엽,김기역,공덕현,이현종,김창연,남항우,Kim, Wu-Young,Han, Sang-Yup,Kim, Ki-Yuk,Kong, Duck-Hyun,Lee, Hyun-Jong,Kim, Chang-Youn,Nam, Hang-Woo 척추신경추나의학회 2009 척추신경추나의학회지 Vol.4 No.1
Objectives: The aim of this study was to evaluate the evolution of lumbar disc herniation in patients treated with oriental medicine. Methods: 14patients(15 cases) with lumbar disc herniation proved at MRI(Magnetic resonance imaging) underwent a follow-up MRI study. Follow-up MRI was performed $4{\sim}14$months(mean 7 months) after initial MRI. Results & Conclusions: 1. 13 cases(87%) had reduction of disc herniation. 1 showed no change in amount of disc herniation. 1 had an increase in disc herniation. 2. Comparison initial MRI with follow-up MRI showed that 2 of the herniations decreased between 0% and 25%, 3 decreased between 25% and 50%, 5 decreased between 50% and 75%, 3 decreased between 75% and 100%. The size of the herniation decreased on average by 49% in 14patients(15 cases). 3. On axial images, the proportion of the cross-sectional area of the spinal canal occupied by the herniated disc was 54.41% on the average on the initial scan, 29.65% on the follow-up scan.
$Br{\aa}nemark\;Novum^{(R)}$ 즉시 임플랜트 보철 수복 방법에 관한 삼차원 유한요소 분석적 연구
김우영,김영수,장경수,김창회,Kim Woo-Young,Kim Yung-Soo,Jang Kyung-Soo,Kim Chang-Whe 대한치과보철학회 2001 대한치과보철학회지 Vol.39 No.5
Since the treatment of edentulous patients with osseointegrated implant was first introduced more than 30 years ago, implant therapy has become one of the most important dental treatment modalities today. Based on the previous experience and knowledge, $Br{\aa}nemark\;Novum^{(R)}$ protocol was introduced with the concept of simplifying surgical and prosthetic technique and reducing healing time recently. This protocol recommends the installation of three 5mm wide diameter futures in anterior mandible and the prefabricated titanium bars for superstructure fabrication. This study was designed to analyze the stress distribution at fixture and superstructure area according to changes of fixture number, diameter and superstructure materials. Four 3-dimensional finite element models were fabricated. Model 1 - 5 standard fixtures (13mm long and 3.75mm in diameter) & superstructure consisted of type IV gold alloy and resin Model 2- 3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of type IV gold alloy and resin Model 3-3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of titanium and resin Model 4-3 wide diameter fixtures (13mm long and 5.0mm in diameter) & superstructure consisted of titanium and porcelain A 150N occlusal force was applied on the 1st molar of each model in 3 directions - vertical($90^{\circ}$), horizontal($0^{\circ}$) and oblique($120^{\circ}$). After analyzing the stresses and displacements, following results were obtained. 1. There were no significant difference in stress distribution among experimental models. 2. Model 2, 3, 4 showed less amount of compressive stress than that of model 1. However, tensile stress was similar. 3. Veneer material with a high modulus of elasticity demonstrated less stress accumulation in the superstructure. Within the limites of this study, $Br{\aa}nemark\;Novum^{(R)}$ protocol demonstrated comparable biomechanical properties to conventional protocol.
Gas Cells for 3He Hyperpolarized via Spin-exchange Optical Pumping
김우영,S. S. Stepanyan,A. Kim,J. A. TAN,S. Woo 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.2
We present a device for the production of hyperpolarized 3He, which is widely used in spinrelated nuclear physics research. Spin-exchange optical pumping (SEOP) is employed to polarize 3He enclosed in a circular borosilicate glass cell suitable not only for the production of polarized gas but also for its storage. The portable glass cell can, thus, be transported to any other research facility. The glass cell can be refilled several times. Special attention is given to the preparation and the filling of the cell to minimize the impurities on its walls and in the gas. We employ glass tubes with shorter lengths and larger diameters in the gas-filling system to achieve the improvement in the air flow necessary to obtain purer polarized 3He samples. The cell is prepared, and after it has been filled with rubidium (Rb) and 3He-N2 mixture, it is sealed under high vacuum conditions. The cell containing the mixture is exposed to circularly-polarized laser light with a wavelength of 795 nm at temperatures of 180 − 220 C for SEOP. The polarization of 3He is measured via nuclear magnetic resonance (NMR). We obtained 40% polarized 3He in less than 15 hours and 50% in about 25 hours. The longitudinal relaxation time T1 of the polarized 3He we measured was about 58 hours.
김우영,A. Gladkov,V. Kavtanyuk,선용근,C. C. Yun,J. W. Kim 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.3
Polarized rare isotope (RI) beams have been designed at the Rare Isotope Science Project (RISP)for the study of the nuclear-structure, nuclear-reaction and astrophysics experiments. A powerfulmethod has been adopted for this work − the production of polarized RI beams via projectilefragmentation. The in-flight system line was designed for this purpose at the RISP by using theprojectile fragmentation method. The working principle, schematic design and experiments to beperformed at the RISP will be presented.
전극 표면의 거칠기가 펜터신/전극 경계면의 전류-전압 특성에 주는 영향
김우영,전동렬,Kim, Woo-Young,Jeon, D. 한국진공학회 2011 Applied Science and Convergence Technology Vol.20 No.2
금속 전극 위에 유기물 채널을 증착하여 만드는 바닥 전극 구조의 유기물 박막 트랜지스터에서 전극 표면이 거친 정도에 따라 전하 주입이 어떻게 달라지는지 조사했다. 금 전극을 실리콘 기판에 증착하고, 가열하여 금 전극 표면을 거칠게 만들었다. 그리고 펜터신과 상부 전극으로 사용할 금 전극을 차례대로 증착하여 금 전극/펜터신/금 전극 구조를 만들었다. 펜터신 증착 초기에는 거친 금 전극 위에서 펜터신 증착핵이 더 많이 보였지만, 막이 두꺼워지면 가열되지 않은 전극과 가열로 거칠어진 전극에서 펜터신 표면 모양에 차이가 거의 없었다. 온도를 바꾸면서 측정한 전류-전압 곡선은 바닥 전극의 표면이 거칠수록 바닥계면의 전위장벽이 높음을 보여주었다. 이 현상은 금속 표면이 거칠수록 일함수가 낮아지며 펜터신과 거친 전극 표면의 경계에 전하 트랩이 더 많기 때문으로 생각된다. We investigated how the surface roughness of electrode affects the charge injection at the pentacene/Au interface. After depositing Au film on the Si substrate by sputtering, we annealed the sample to control the Au surface roughness. Pentacene and Au top electrode were subsequently deposited to complete the sample. The nucleation density of pentacene was slightly higher on the rougher Au electrode, but surface morphologies of thick pentacene films were similar on both the as-prepared and the roughened Au electrodes. The current-voltage curves obtained from the Au/pentacene/Au structure measured as a function of temperature indicated that the interface barrier was higher for the rougher Au bottom-electrode. We propose that the higher barrier was caused by the lower work function of rougher electrode surface and the higher trap density at the interface.