• 한국광학회지
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• 제21권4호
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• pp.133-138
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• 2010

모든 복사온도계는 복사원 크기효과(Size-of-Source Effect, SSE)와 자기복사효과를 가지고 있다. 복사원의 직경에 따른 복사온도계의 검출기 신호세기로 정의된 SSE의 주원인은 회절이기 때문에 파장에 크게 좌우된다. 본 논문에서는 중저온영역에서 복사온도의 전달표준기로 많이 사용되고 있는 TRT2(Transfer Radiation Thermometer 2, HEITRONICS)의 SSE와 자기복사 특성을 측정하였다. 측정한 TRT2의 SSE 값을 사용하여 계산한 결과 흑체의 온도가 $300^{\circ}C$ 일 때, 개구 직경이 60 mm인 흑체와 10 mm인 흑체의 복사온도 차이가 저온모드($8-14\;{\mu}m$)에서 $3.5^{\circ}C$, 중온모드($3.9\;{\mu}m$)에서 $0.5^{\circ}C$인 것을 알 수 있었다. 또한, 복사온도계 몸체 온도가 $2.6^{\circ}C$ 변화했을 때 자기복사효과 때문에 흑체의 복사온도는 110 mK 다르게 측정되었다.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.35-44
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• 2020

Background: Cadmium zinc telluride (CZT) is a promising material because of a high detection efficiency, good energy resolution, and operability at room temperature. However, the cost of CZT dramatically increases as its size increases. In this study, to achieve a large effective volume with relatively low cost, an array structure comprised of individual virtual Frisch-grid CZT detectors was proposed. Materials and Methods: The prototype consisted of 2 × 2 CZTs, a holder, anode and cathode printed circuit boards (PCBs), and an application-specific integrated circuit (ASIC). CZTs were used and the non-contacting shielding electrode method was applied for virtual Frisch-grid effect. An ASIC was used, and the holder and the PCBs were fabricated. In the current system, because the CZTs formed a common cathode, a total of 5 channels were assigned for data processing. Results and Discussion: An experiment using ¹³⁷Cs at room temperature was conducted for 10 minutes. Energy and timing information was acquired and the depth of interaction was calculated by the timing difference between the signals of both electrodes. Based on obtained three-dimensional position information, the energy correction was carried out, and as a result the energy spectra showed the improvements. In addition, a Compton image was reconstructed using the iterative method. Conclusion: The virtual Frisch-grid CZT detector based on the array structure was developed and the energy spectra and the Compton image were successfully acquired.

• 한국입자에어로졸학회지
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• 제8권1호
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• pp.29-35
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• 2012

The Faraday cup electrode of different size has been developed and evaluated to investigate the diffusion effect of particles by Brownian motion in a particle beam mass spectrometer(PBMS). Particles which focused and accelerated by aerodynamic lens are charged to saturation in an electron beam, and then deflected electrostatically into a Faraday cup detector for measurement of the particle current. The concentration of particles is converted from currents detected by Faraday cup. Measurements of particle current as a function of deflection voltage are combined with measured relationships between particle velocity and diameter, charge and diameter, and mass and diameter, to determine the particle size distribution. The particle currents were measured using 5, 10, 20, 40 mm sized Faraday cup that can be move to one direction by motion shaft. The current difference for each sizes as a function of position was compared to figure out diffusion effect during transport. Polystyrene latex(PSL) 100, 200 nm sized standard particles were used for evaluation. The measurement using 5 mm sized Faraday cup has the highest resolution in a diffusion distance and the smaller particles had widely diffused.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1824-1827
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• 2003

The sheet metal shearing process is normally used in the precision elements such as semi-conductor components. In precision elements, burrs usually reduce the quality of machined parts and cause interference, jamming and misalignment during assembly procedures and because of their sharpness, they can be safety hazard to personnel. Furthermore, not only burrs are hard to predict and avoid, but also deburring, the process of removing burrs, is time-consuming and costly. In order to get the burr-free parts, therefore, we developed the precise burr measuring system using the laser. The laser burr measuring system consists of the laser probe, the photo detector, the achromatic doublet lens, and the rotary ＆ the X-Y table. In previous reports, we used simple vertical measuring method. But, as we used relatively bigger laser spot diameter and had the limited reflection angle, it was difficult to obtain the precise measuring results. So called, the spot size effect makes the profile of burr measured distorted and the burr height measured smaller. By introducing the novel laser measuring method which employing the achromatic lens system and the tilting mechanism, we could make the spot size smaller and get the appropriate beam direction angle. Through the experiments, the accuracy of the developed system is proved. The burr height measured during the punching process can be used for automatic deburring and in-situ aligning.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4096-4101
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• 2023

Radon is a radioactive gas produced from the uranium-238 series. Radon gas affects public health and is the second cause of lung cancer. The study samples were collected from one area of the city of Jazan, southwest of the Kingdom of Saudi Arabia. The influence of engineering and physical parameters on the emanation coefficient of gas and other gas parameters was studied. Parameters for radon were measured using a CR-39 Solid-State Nuclear Track Detector (SSNTD) through a sealed emission container. The results showed that the emanation coefficient was affected directly by the change in the grain size of the soil. All parameters of measured radon gas have the same behavior as the emanation coefficient. The relationship between particle size and emanation coefficient showed a good correlation. The values of the emanation coefficient were inversely affected by the mass of the sample, and the rest of the parameters showed an inverse behavior. The results showed that increasing the volume of the container increases the accumulation of radon sons on the wall of the container, which increases the emission factor. The rest of the parameters of radon gas showed an inverse behavior with increasing container size. The results concluded that changing the engineering and physical parameters has a significant impact on both the emanation coefficient and all radon parameters. The emanation coefficient affects the values of the radiation dose of an alpha particle.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4167-4172
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• 2023

Miniaturized tissue equivalent proportional counters (mini-TEPCs) are proper for radiation dosimetry in medical application because the small size of the dosimeter could prevent pile-up effect under the high intensity of therapeutic beam. However, traditional methods of calibrating mini-TEPCs using internal alpha sources are not feasible due to their small size. In this study, we investigated the use of electron and proton edges on Monte Carlo-generated lineal energy spectra as markers for calibrating a 0.9 mm diameter and length mini-TEPC. Three possible markers for each spectrum were calculated and compared using different simulation tools. Our simulations showed that the electron edge markers were more consistent across different simulation tools than the proton edge markers, which showed greater variation due to differences in the microdosimetric spectra. In most cases, the second marker, y_δδ, had the smallest uncertainty. Our findings suggest that the lineal energy spectra from mini-TEPCs can be calibrated using Monte Carlo simulations that closely resemble real-world detector and source geometries.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1723-1726
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• 2008

In recent years, there has been a remarkable progress in the development of the fiber optic sensors for the detection of various chemicals. Fiber optic sensors have the advantages of very small size, flexibility and low cost. The fiber optic sensors employing different optical or spectroscopic phenomena have been reported such as bulk absorption, optical reflectance, fluoresces and energy transfer. In this study, the effect of nanoparticle concentration in liquid upon light absorption and scattering was studied using extrinsic fiber optic method. For the evaluation, we used Red (650 nm) and Blue (430 nm) light sources which are coupled through the standard cuvette using optical fiber to detector. The experiments are carried out with Polystyrene latex (400 - 800 nm), and Silicon (35 - 110 nm) nanoparticles suspended in Isopropanol. Differences in light absorption and scattering depending on nanoparticle concentration and type are discussed. This method may be useful to study nanoparticles properties for various application and research.

• 한국의학물리학회지:의학물리
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• 제21권2호
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• pp.137-144
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• 2010

64 multi-detector computed tomography (MDCT)에서 두개부의 과도한 선량이 문제가 되어 고정관류기법과 관전류 자동노출조절(automatic exposure control, AEC) 기법을 이용하여 선량 감소 정도를 비교 평가하고자 한다. 연구에 사용한 장비는 Siemens사의 SOMATOM Definition 64 multi-detector CT를 이용했으며, Whole body phantom (KUPBU-50, Kyoto Kagaku CO. Ltd)의 두개부를 사용했다. 실험 protocol은 helical scan 방식을 적용하여 120 kVp, rotation time은 1 sec, slice thickness와 increment는 각각 5 mm, FOV는 250 mm, matrix size는 $512{\times}512$, collimation은 $64{\times}0.625\;mm$, pitch는 1로 조사하였다. 선량감소효과의 측정방법은 관전류를 350 mAs로 고정한 방법과 AEC 기법을 적용한 방법으로 나누어 평가하였으며, 영상품질은 CT number의 표준편차를 이용하여 영상의 잡음을 측정하였다. 이 때 두개부(craniofacial bone)는 머리덮개뼈(calvaria) 끝부분에서 눈썹활(superciliary ridge)까지를 1구역, 논썹활 아래부터 코가시점(acanthion)까지를 2구역, 그리고 코가시점 아래부터 턱(mentum)끝까지를 3구역으로 정의하여 측정하였다. 고정관류기법에서 구역별로 CTDIvol은 57.7 mGy였으며, DLP는 $640.2\;mGy{\cdot}cm$로 동일하였다. AEC 기법을 적용한 1구역은 CTDIvol: 30.7 mGy, DLP: $340.7\;mGy{\cdot}cm$, 2구역은 CTDIvol: 46.5 mGy, DLP: $515.0\;mGy{\cdot}cm$, 그리고 3구역은 CTDIvol: 30.3 mGy, DLP: $337.0\;mGy{\cdot}cm$으로 나타났다. 영상품질을 나타내는 CT number의 표준편차는 1구역에서 고정 관류기법은 2.6, AEC 기법은 3.0, 2구역에서 고정 관류기법은 3.1, AEC 기법은 3.4, 3구역에서 고정 관류기법은 2.7, AEC 기법은 3.2으로 측정되었다. 64 MDCT에서의 AEC 기법은 기존의 고정관류법에 비해 안구, 이하선 그리고 갑상선 부위에 대해 큰 선량 감소효과가 나타났으며, 두개부의 방사선량을 감소시키는데 매우 유용한 기법으로 사료된다.

• 대한방사선치료학회지
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• 제17권2호
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• pp.141-145
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• 2005

목 적 : 일반적으로 10 MV이상의 광자선에서 산란 중성자를 발생시키는 것으로 알려져 있다. 세관에 설치된 컨테이너 검색장치는 9 MV 이하였음에도 중성자가 누출되었다. 본 연구에서 의료기관에 설치된 방사선 치료기에서 산란 방출되는 중성자의 공간적인 측정을 통해 결과를 분석하고 평가하고자 한다. 대상 및 방법 : 본 연구의 방사선 발생장치는 의료용 선형가속기(linear accelerator, linac: Varian, Clinac 1800, USA)를 사용하였다. 중성자 측정용 검출기는 중성자가 발생하면 기포(bubble)이 생기는 Bubble 검출기(Bubble detector, BDPND type, BTI, Canada)를 사용하였다. 의료용 선형가속기 주변에 Bubble 검출기를 isocenter로부터 30 cm, 50 cm, 120 cm의 각각 3가지 거리별로 isocenter 상하 방향 네 곳에 위치시켜 측정하였다. 주변 구조물의 영향을 살펴보기 위해 Wedge와 Mount를 장착 후 50 cm 거리에서 각각 8방향에서 측정하였다. 광자선원부터 isocenter 까지의 거리(SAD: source-axis-distance)를 100 cm로 기준을 정하고 조사면의 크기(field size)는 $15{\times}15cm^2$로 정하였다. 방사선은 20 MU를 조사하여 Bubble 검출기에 발생한 기포수를 측정하며 mrem값으로 계산하였다. 결 과 : Isocenter부터 거리가 30 cm와 50 cm 떨어진 곳의 각각 8개 측정 지점 중에서는 모두 5번 위치(Gantry 우측 아래지점)에서 측정된 산란중성자의 양이 같은 거리라도 가장 높게 측정되었다. Bubble 검출기가 Isocenter부터 120 cm 떨어진 경우와 wedge를 장착한 경우는 7번 위치(Couch 우측 아래지점), mount 탈착한 경우는 2번 위치(Gantry 왼쪽 윗지점)에서 산란 중성자가 가장 높게 측정되었다. 결 론 : 산란중성자의 측정에서 직선상 같은 거리에 있는 곳이라도, 실제 측정한 결과 값에 따르면 서로 상이한 값을 보였다. 주변 구조물도 산란 중성자에 영향을 미치며, 직선상은 같은 거리라도 각각의 지점에서 다른 값을 보였다. 따라서, 산란중성자의 거리에 따른 영향은 단순히 직선으로의 거리뿐 아니라 방향과 주변 구조물에 대한 영향까지 고려하며 공간적인 측정과 평가가 필요하다.

• 천문학회보
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• 제43권1호
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• pp.72.2-72.2
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• 2018

The Opposition Effect (OE) is an enhancement of the brightness of a reflecting light as the phase angle (the Sun-target-observer angle) approaches zero. The mechanisms have been studied both theoretically and experimentally and nowadays recognized that there are two major mechanisms, namely, coherent backscattering OE (CBOE) and shadow hiding OE (SHOE). From data analyses of an S-type asteroid Itokawa taken with the Hayabusa spacecraft onboard camera, it is suggested that the CBOE would be dominant at phase angle smaller than ~ 1.4 deg, while SHOE dominates at larger phase angles (M. Lee & M. Ishiguro, under review). The study on the physical parameters which affect the OE, such as size and composition, will lead us to find a way to disentangle each of them from observation. The experiments in lab, however, faces two major difficulties: (a) the detector blocks the incident light if phase angle is nearly zero and (b) incident and emission angles must be controlled with high angular resolution to prevent blurring of OEs at different phase angles in one measurement. In this presentation, we introduce a new apparatus which has been installed at Seoul National University to investigate the OE in our lab, and summarize the initial results. It will be a valuable starting point to establish infrastructure in Korea, and will shed light on the investigation of OE physics using laboratory simulants.