• 대한방사선기술학회지:방사선기술과학
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• 제43권3호
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• pp.169-176
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• 2020

Interventional radiology is performed under real-time fluoroscopy, and patients are exposed to a wide range of exposures for a long period of time depending on the examination and procedure. However, studies on radiation protection for patients during an intervention are insufficient. This study aims to evaluate the doses exposed during the intervention and the applicability of 3D printing materials. The organ dose for each intervention site was evaluated using a monte carlo simulatio. Also, the dose reduction effect of the critical organs was calculated when using a shielding device using 3D printing materials. As a result, the organ dose distribution for each intervention site showed a lower dose distribution for organs located far from the x-ray tube. It was analyzed that the influence of scattered rays was higher in the superficial organs of the back of the human body where x-rays were incident. The dose reduction effect on the critical organ using the 3D printing shield showed the highest testis among the gonads, and in the case of other organs, the dose reduction effect gradually decreased in the order of the eye, thyroid, breast, and ovary. Accordingly, it is judged that the 3D printed shield will be sufficiently usable as a shielding device for the radiation protection of critical organs.

• 대한전자공학회논문지TC
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• 제48권5호
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• pp.46-53
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• 2011

유한한 기판크기가 E-평면으로 배열된 선형 위상 배열 안테나의 방사 특성에 미치는 영향을 연구하였다. 여러 가지 기판 크기에 따른 active reflection coefficient 와 average active element pattern 으로부터 선형 배열안테나의 방사특성을 예측하였다. E-평면과 만나는 기판 가장자리까지의 거리 변화가 H-평면과 만나는 기판 가장자리까지의 거리 변화에 비해 위상 배열 안테나의 방사 패턴 특성에 미치는 영향이 큰 것을 알 수 있었다.

• 한국재료학회지
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• 제12권1호
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• pp.27-35
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• 2002

In laser materials processing, localized heating, melting and evaporation caused by focused laser radiation forms a vapor on the material surface. The plume is generally an unstable entity, fluctuating according to its own dynamics. The beam is refracted and absorbed as it traverses the plume, thus modifying its power density on the surface of the condensed phases. This modifies material evaporation and optical properties of the plume. A laser-produced plasma plume simulation is completed using axisymmetric, high-temperature gas dynamic model including the laser radiation power absorption, refraction, and reflection. The physical properties and velocity profiles are verified using the published experimental and numerical results. The simulation results provide the effect of plasma plume fluctuations on the laser power density and quantitative beam radius changes on the material surface. It is proved that beam absorption, reflection and defocusing effects through the plume are essential to obtain appropriate mathematical simulation results. It is also found that absorption of the beam in the plume has much less direct effect on the beam power density at the material surface than defocusing does and helium gas is more efficient in reducing the beam refraction and absorption effect compared to argon gas for common laser materials processing.

• Nuclear Engineering and Technology
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• 제31권5호
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• pp.522-528
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• 1999

The effect of a water-soluble extract from natural materials on radiation-induced mutations was studied by means of TSH assay in Tradescantia 4430 stamen hair cells. Inflorescence cuttings, with or without pretreatments of natural extracts for 3 hours, were exposed to 1 Gy of gamma ray. Comparisons were made on the basis of pooled data during the peak interval between the mean pink mutation frequencies of the experimental groups. Pretreatments of FB or FB-I resulted in about two-fold increases of the pink mutation frequencies, compared to those of the control group. Synergism between certain fractions and radiation was a possible cause of the increased DNA damage. FB and FB-I had a radiosensitizing effects on the pink mutations in Tradescantia 4430 stamen hair cells (p<0.001). On the other hand, the extract PP in a proper concentration significantly reduced the pink mutation frequencies (p<0.05). The result means that PP has a protective effect on the radiation-induced cell damage.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.21-27
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• 2014

In this paper, an approximate formula for radiation efficiency of the plate surround by an infinite rigid baffle is studied. The plate is simply supported and one side is in contact with air, while other side with water. By assuming an infinite plate, the fluid loading effect is derived in terms of an effective mass. Based on the observation that the fluid loading effect decreases as frequency increases, the radiation efficiency formula at high frequency, which was originally derived for a plate vibrating in the air, is modified as the approximate formula for a submerged plate. The fluid loading effect is taken into account in the wavenumber of the plate. Comparisons of the approximate formula with the numerical results shows that they match well except the mid-frequency range in which numerical results show many oscillations. In numerically solving the fully coupled equations of motion, fourfold integrals of the impedance coefficients are reduced to single nonsingular integrals, which results in substantial reduction in computing time.

• 설비공학논문집
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• 제16권10호
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• pp.942-951
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• 2004

This paper presents the results of a theoretical study of the effect of radiation during free convective laminar film boiling for methanol/water binary mixtures on an isothermal vertical wall at atmospheric pressure. With the well-known boundary layer theory as a basis, a theoretical model has been formulated into consideration for mass diffusion at liquid phase. The equations are numerically solved by a similarity method to investigate the effects of radiation emissivity on the surface with various parameters such as wall superheat and composition of more volatile component at liquid phase far from the wall. From the results, the distributions of the physical quantifies are investigated in both phases. New correlations are proposed to predict the heat transfer coefficient of binary mixtures. It is shown that the proposed correlations are in good agreement with numerical results and with Bromley's correlation within maximum $11\%$ errors. It is also found that as the wall superheat is increased, radiation effect becomes more important.

• 한국의학물리학회지:의학물리
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• 제15권2호
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• pp.59-62
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• 2004

본 논문에서는 마이크로필름과 탄소막 전극을 이용하여 개발한 소형 방사선측정기의 특성을 평가하였다. 전극은 5 mm 직경의 고전압전극, 3.3 mm 직경의 수집전극, 그리고 넓이가 0.7 mm인 보호전극으로 구성되었으며, 이온수집 공동의 부피는 0.016 ㎤이었다. 6 MV X-선을 이용하여 제작된 측정기에 대한 전기적 특성을 조사하였는데, 누설전류는 0.1 pA, 재현 오차가 0.1% 이하, 선량률 효과는 1.5% 이하, 분극효과는 2.4% 이하로 나타났다. 개발된 측정기의 전기적 특성은 양호한 것으로 평가되며, 추후 깊이선량률, 빔측면도와 같은 선량분포에 대한 특성의 평가가 요구된다.

• 대한방사선치료학회지
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• 제8권1호
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• pp.75-81
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed . This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement, of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and $20.6\%$ for the CO-60, 4MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions the larger beam reductions occur. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.

• 대한전자공학회논문지SD
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• 제45권3호
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• pp.1-5
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• 2008

본 논문은 고에너지 전자빔을 이용하여 저궤도 인공위성의 실리콘 태양센서의 내방사선 특성 변화를 분석하였다. 일반적으로 저궤도를 선회하는 위성은 반알렌대를 통과하며, 이 안에서 주기적인 운동으로 남극과 북극을 이동하는 하전입자에 의해 전자부품이 쉽게 손상되고 수명이 단축되는 등 악 영향을 받고 있다. 특히 방사선에 의한 SEU (Single Event Upset) 등은 인공위성에 탑재된 반도체 소자의 오동작 유발의 원인이 되고 있다. 본 논문은 한국원자력 연구원의 고에너지 ($300keV{\sim}1MeV$) 전자빔 조사장치를 이용하여 태양전지에 전자빔을 조사하고 이 때 변화되는 각각의 파라미터들에 대한 값을 측정하고자 한다. 이러한 연구는 저궤도 인공위성에서 전력을 생산하기 위해서 사용하는 전력용 태양 전지의 방사능 영향을 이해하는 데도 많은 영향을 줄 수 있을 것으로 기대된다.

• 한국방사선학회논문지
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• 제15권2호
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• pp.191-199
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• 2021

본 연구의 목적은 경량 연자성 소재의 방사선 차폐 효과를 분석하여 군사시설에 대한 적용 가능성을 확인하는 것이다. 연자성 물질은 EMP 차폐에 효과적인 것으로 알려져 있다. 이 물질이 방사선 차폐에도 효과적이라면 군 방호에 효과적으로 적용이 가능할 것으로 예상된다. 이에 본 연구에서는 감마선 차폐 효과를 확인하기 위해 Cs-137 및 Co-60 선원을 사용하여 실험을 수행하였으며, 중성자 차폐 효과를 평가하기 위해 Monte Carlo N-Particle (MCNP) 모델링을 적용하였다. 그 결과 연자성 소재의 두께가 증가함에 따라 감마선과 중성자의 선형 감쇠 법칙에 의한 차폐성능이 향상됨을 확인할 수 있었다. 따라서 연자성 소재를 군사용 구조물 등에 적용할 경우에 방사선 차폐에 효과적이라는 것을 확인하였다.