• 한국의학물리학회지:의학물리
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• 제4권1호
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• pp.55-71
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• 1993

Measured and calculated the TMR and SMR factors from percent depth dose underpartial attenuators which cover the whole part of the radiation beam with variousfilter thickness from 0 to 50 mm. This study was performed for x-ray beams generated with a 6 MV linear acceleratorat source to surface distance of 100cm in a water phantom for Lipowitz metal. TMR(0,d,t) was derived from non-linear polynomial regression with field sizedifferencies and a given filter thickness. In this experiments, the TMR(0,10,50) of 50mm of filter thickness was showed13.6 % higher than that of open field and SMR(5,10,50) was 38.5% smaller than thatof open field in same depth.

• 한국방사선학회논문지
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• 제16권6호
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• pp.741-749
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• 2022

산업체에서 용접구조물을 파괴 없이 품질을 검증하는 방사선투과검사는 압도적으로 많이 이용되지만, 방사선을 이용함에 따라 많은 안전사항이 요구된다. 방사선투과검사 작업종사자는 검사부재의 이동유무에 따라 감마선조사기인 운반용기에 내장된 Iridium-192 방사선원을 사용시설 내 혹은 사용시설 외의 장소에서 이동시켜 작업을 수행 한다. 일반적인 사용시설은 두꺼운 콘크리트로 외부와 방사선을 전면 차단한 시설이지만, 검사부재의 취급이 용이하지 않은 등의 사유로 천장이 개방된 사용시설이 있다. 일반적인 사용시설은 외부가 모두 차단되어 이론적인 선량 평가 방법을 통하여 건설하여도 무방하지만, 천장이 개방된 경우 스카이샤인효과로 인하여 단순 이론적인 계산 방법으로 방사선 안전성을 평가하는 것은 적합하지 않다. 따라서 본 연구에서는 실제 현장에서 해당 시설의 방사선 안전성을 이온챔버형 방사선측정기와 누적선량계형인 OSLD를 통하여 평가하고, 실제 평가 환경을 몬테카를로 시뮬레이션 코드인 플루카를 이용하여 모델링 및 평가를 하였다. 해당 시설에서 조사방향에 따라 시설 경계의 방사선량은 규제기관에서 정하는 기준을 만족하기 어려웠고, 추가의 방법을 통하여 방사선 안전성을 확보할 수 있었다. 또한, Iridium-192 선원을 이용한 시뮬레이션 결과가 실제 측정값과 유효한 결과임을 확인할 수 있었다.

• Journal of Radiation Protection and Research
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• 제48권2호
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• pp.90-99
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• 2023

Background: Quantitative risk assessments should be accompanied by uncertainty analyses of the risk models employed in the calculations. In this study, we aim to develop a computational code named SUMRAY for use in cancer risk projections from radiation exposure taking into account uncertainties. We also aim to make SUMRAY publicly available as a resource for further improvement of risk projection. Materials and Methods: SUMRAY has two versions of code written in R and Python. The risk models used in SUMRAY for all-solid-cancer mortality and incidence were those published in the Life Span Study of a cohort of the atomic bomb survivors in Hiroshima and Nagasaki. The confidence intervals associated with the evaluated risks were derived by propagating the statistical uncertainties in the risk model parameter estimates by the Monte Carlo method. Results and Discussion: SUMRAY was used to calculate the lifetime or time-integrated attributable risks of cancer under an exposure scenario (baseline rates, dose[s], age[s] at exposure, age at the end of follow-up, sex) specified by the user. The results were compared with those calculated using another well-known web-based tool, Radiation Risk Assessment Tool (RadRAT; National Institutes of Health), and showed a reasonable agreement within the estimated confidential interval. Compared with RadRAT, SUMRAY can be used for a wide range of applications, as it allows the risk projection with arbitrarily specified risk models and/or population reference data. Conclusion: The reliabilities of SUMRAY with the present risk-model parameters and their variance-covariance matrices were verified by comparing them with those of the other codes. The SUMRAY code is distributed to the public as an open-source code under the Massachusetts Institute of Technology license.

• 한국의학물리학회지:의학물리
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• 제29권1호
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• pp.8-15
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• 2018

This work reports the acceptance testing and commissioning experience of the Robotic Intensity-Modulated Radiation Therapy (IMRT) M6 system with a newly released $InCise^{TM}2$ Multileaf Collimator (MLC) installed at the Yonsei Cancer Center. Acceptance testing included a mechanical interdigitation test, leaf positional accuracy, leakage check, and End-to-End (E2E) tests. Beam data measurements included tissue-phantom ratios (TPRs), off-center ratios (OCRs), output factors collected at 11 field sizes (the smallest field size was $7.6mm{\times}7.7mm$ and largest field size was $115.0mm{\times}100.1mm$ at 800 mm source-to-axis distance), and open beam profiles. The beam model was verified by checking patient-specific quality assurance (QA) in four fiducial-inserted phantoms, using 10 intracranial and extracranial patient plans. All measurements for acceptance testing satisfied manufacturing specifications. Mean leaf position offsets using the Garden Fence test were found to be $0.01{\pm}0.06mm$ and $0.07{\pm}0.05mm$ for X1 and X2 leaf banks, respectively. Maximum and average leaf leakages were 0.20% and 0.18%, respectively. E2E tests for five tracking modes showed 0.26 mm (6D Skull), 0.3 mm (Fiducial), 0.26 mm (Xsight Spine), 0.62 mm (Xsight Lung), and 0.6 mm (Synchrony). TPRs, OCRs, output factors, and open beams measured under various conditions agreed with composite data provided from the manufacturer to within 2%. Patient-specific QA results were evaluated in two ways. Point dose measurements with an ion chamber were all within the 5% absolute-dose agreement, and relative-dose measurements using an array ion chamber detector all satisfied the 3%/3 mm gamma criterion for more than 90% of the measurement points. The Robotic IMRT M6 system equipped with the $InCise^{TM}2$ MLC was proven to be accurate and reliable.

• Imaging Science in Dentistry
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• 제54권2호
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• pp.129-137
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• 2024

Purpose: Patients with head and neck cancer (HNC) who undergo dental procedures during radiotherapy (RT) face an increased risk of developing osteoradionecrosis (ORN). Accordingly, new tools must be developed to extract critical information regarding the dose delivered to the teeth and mandible. This article proposes a novel approach for visualizing 3-dimensional planned dose distributions on panoramic reconstruction computed tomography (pCT) images. Materials and Methods: Four patients with HNC who underwent volumetric modulated arc therapy were included. One patient experienced ORN and required the extraction of teeth after RT. In the study approach, the dental arch curve (DAC) was defined using an open-source platform. Subsequently, pCT images and dose distributions were generated based on the new coordinate system. All teeth and mandibles were delineated on both the original CT and pCT images. To evaluate the consistency of dose metrics, the Mann-Whitney U test and Student t-test were employed. Results: A total of 61 teeth and 4 mandibles were evaluated. The correlation coefficient between the 2 methods was 0.999, and no statistically significant difference was observed (P>0.05). This method facilitated a straightforward and intuitive understanding of the delivered dose. In 1 patient, ORN corresponded to the region of the root and the gum receiving a high dosage (approximately 70 Gy). Conclusion: The proposed method particularly benefits dentists involved in the management of patients with HNC. It enables the visualization of a 3-dimensional dose distribution in the teeth and mandible on pCT, enhancing the understanding of the dose delivered during RT.

• 대한기계학회논문집B
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• 제29권1호
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• pp.151-158
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• 2005

A characteristic of discharge for a foam spray nozzle with various parameters was investigated. The discharge patterns from a fire foam spray nozzle are important to evenly spray over a maximum possible floor area. Two parameters of a foam spray nozzle were chosen, and compared with those from the standard one. Also, in order to evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-protection foams were experimentally investigated. A simple repeatable test for fire-protection foams subjected to fire radiation was developed. This test involves foam generation equipment, a fire source for heat generation, and data acquisition techniques. Results show that the bubble size of foam is increased by large inside diameter of orifice or closed air hole, but phenomenon of discharge angle and expansion ratio is opposite. For the case of the open air hole, liquid film of a circular cone discharges with formation, growth, split and fine grain. In case of the closed air hole, a pillar of foam solution discharges with that. Though the temperature gradient in the foam increases with increased foam expansion ratio. it is not change with increased intensity of heat flux.

• 태양에너지
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• 제12권3호
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• pp.70-83
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• 1992

본 연구에서는 개방된 정사각형 공간안에 일정한 열유속을 방출하는 발열체가 존재할 때, 부력과 표면복사를 고려한 혼합대류특성을 수치적으로 연구하였다. 본 연구의 대상인 유입구를 통해 유체가 흘러들어와서 다시 유출구로 나가는 정사각형공간은 공냉식 전자장비를 모사한 것이다. 이러한 공간안에 존재하는 발연체는 전자칩과 같은 발열성 전자부품을 나타낸다. 본 연구에서 채택한 모델의 크기는 높이 X 넓이가 $0.1[m]{\times}0.1[m]$이며 공간내부는 2차원 층류유동으로 간주하였다. 공기의 유입속도는 0.07[m/s]이고, 유입온도는 $27^{\circ}C$이며, 유입구의 위치는 일정한 위치에 고정되어 있다. 주요 변수로는 발열체의 열유속, 유출구의 위치, 발열체의 위치, 그리고 벽면이 방사율을 선택하였다. 본 연구에서는 외부로부터 유입되어지는 찬공기와 발열체에 의해서 부력의 상승하는 뜨거운 공기의 혼합에 의한 유동특성 및 열전달특성을 복사를 고려하여 고찰하였다. 결과로써 가장 열전달이 활발한 발열체의 위치는 바닥의 좌측벽으로부터 0.075[m]일때이다. 이러한 연구는 실제적으로 전자부품 같은 것의 효율적인 냉각목적에 적용되어질 수 있다.

• 한국전자파학회논문지
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• 제9권5호
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• pp.567-577
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• 1998

유한차분 시간영역 방법을 이용하여 연속 및 불연속 마이크로스트립올 해석할 때 홉수 경계조건은 Berenger의 완전 접합충(Perfectly Matched Layer:PML)올 3차원으로 적용하고, 전원의 인가는 기존의 마이크로스트립 전면(front face)에 인가하는 방법 대신 내부전원(Inner Source Technique:IST)을 이용하였다. 이 방법을 이용하면 de성분의 왜곡이 개선되고, 에베네센트(evanescent) 및 복사 전자계가 존재하는 측면과 윗면의 계산 영역올 줄이더라도 해석된 특성은 신뢰할 수 있는 결과를 얻올 수 있었다. 또한 내부전원의 위치를 조정함으로서 불완전한 경계조건에 의해서 발생되는 반사파의 영향올 효과적으로 제거할 수 있었다. 본 연구에서는 이러한 방법을 이용하여 마이크로스트립의 분산특성 및 특성임피던스를 계산하였다. 그리고 종단개방 마이크로스트립의 산란계수의 크기와 위상올 구하고 그 동가회로를 계산하였다.

• 전기전자학회논문지
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• 제24권1호
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• pp.368-371
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• 2020

본 논문에서는 휴대용 UHF대역 RFID 시스템을 위한 선형 테이퍼드 슬롯 정류 안테나를 제안하였다. 제안한 정류 안테나는 별도의 유전체 기판을 사용하지 않기 때문에, 얇은 금속 두께로 평판형 안테나를 구현하였다. 정류 안테나는 입력 RF전력을 출력 DC전압으로 전환하는 정류회로는 2개의 쇼트기 다이오드를 이용한 배전압회로를 이용하였으며, 선형 테이퍼드 슬롯 안테나에 집적하여 정류 안테나를 설계하였다. 배전압 정류회로와 선형 테이퍼드 슬롯 안테나의 임피던스 공액정합을 위하여, 테이퍼드 슬롯의 각도와 안테나 급전선의 길이의 조절을 통해 source-pull 방법을 이용하였다. 제안한 안테나 시제품은 자유공간 무선환경실험 환경에서 RF-DC전환 실험과 원거리장 안테나 방사패턴 측정실험을 통해 회로 및 방사 특성을 검증하였다. 최종 제안한 안테나는 중심주파수 915 MHz 기준으로 0.23-파장(75 mm)와 0.18-파장(60 mm) 크기로 소형화하였다.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.434-441
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• 2010

The activation products of aluminum and argon are key radionuclides for operational and environmental radiological safety during the normal operation of open-tank-in-pool type research reactors using aluminum-clad fuels. Their activities measured in the primary coolant and pool surface water of HANARO have been consistent. We estimated their sources from the measured activities and then compared these values with their production rates obtained by a core calculation. For each aluminum activation product, an equivalent aluminum thickness (EAT) in which its production rate is identical to its release rate into the coolant is determined. For the argon activation calculation, the saturated argon concentration in the water at the temperature of the pool surface is assumed. The EATs are 5680, 266 and 1.2 nm, respectively, for Na-24, Mg-27 and Al-28, which are much larger than the flight lengths of the respective recoil nuclides. These values coincide with the water solubility levels and with the half-lives. The EAT for Na-24 is similar to the average oxide layer thickness (OLT) of fuel cladding as well; hence, the majority of them in the oxide layer may be released to the coolant. However, while the average OLT clearly increases with the fuel burn-up during an operation cycle, its effect on the pool-top radiation is not distinguishable. The source of Ar-41 is in good agreement with the calculated reaction rate of Ar-40 dissolved in the coolant.