• Wind and Structures
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• 제28권2호
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• pp.71-87
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• 2019

The yaw and interference effects of blades affect aerodynamic performance of large wind turbine system significantly, thus influencing wind-induced response and stability performance of the tower-blade system. In this study, the 5MW wind turbine which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was chosen as the research object. Large eddy simulation on flow field and aerodynamics of its wind turbine system with different yaw angles($0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $45^{\circ}$) under the most unfavorable blade position was carried out. Results were compared with codes and measurement results at home and abroad, which verified validity of large eddy simulation. On this basis, effects of yaw angle on average wind pressure, fluctuating wind pressure, lift coefficient, resistance coefficient,streaming and wake characteristics on different interference zone of tower of wind turbine were analyzed. Next, the blade-cabin-tower-foundation integrated coupling model of the large wind turbine was constructed based on finite element method. Dynamic characteristics, wind-induced response and stability performance of the wind turbine structural system under different yaw angle were analyzed systematically. Research results demonstrate that with the increase of yaw angle, the maximum negative pressure and extreme negative pressure of the significant interference zone of the tower present a V-shaped variation trend, whereas the layer resistance coefficient increases gradually. By contrast, the maximum negative pressure, extreme negative pressure and layer resistance coefficient of the non-interference zone remain basically same. Effects of streaming and wake weaken gradually. When the yaw angle increases to $45^{\circ}$, aerodynamic force of the tower is close with that when there's no blade yaw and interference. As the height of significant interference zone increases, layer resistance coefficient decreases firstly and then increases under different yaw angles. Maximum means and mean square error (MSE) of radial displacement under different yaw angles all occur at circumferential $0^{\circ}$ and $180^{\circ}$ of the tower. The maximum bending moment at tower bottom is at circumferential $20^{\circ}$. When the yaw angle is $0^{\circ}$, the maximum downwind displacement responses of different blades are higher than 2.7 m. With the increase of yaw angle, MSEs of radial displacement at tower top, downwind displacement of blades, internal force at blade roots all decrease gradually, while the critical wind speed decreases firstly and then increases and finally decreases. The comprehensive analysis shows that the worst aerodynamic performance and wind-induced response of the wind turbine system are achieved when the yaw angle is $0^{\circ}$, whereas the worst stability performance and ultimate bearing capacity are achieved when the yaw angle is $45^{\circ}$.

• 대한조선학회논문집
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• 제28권2호
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• pp.52-68
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• 1991

캐비테이션 특성이 우수하고 넓은 받음각에서 양력-향력비가 큰 새로운 날개단면(KH18 단면)을 사용하여 체계적인 방법으로 기하학적 형상을 변화시켜 설계된 새로운 계열 프로펠러의 개발을 시도하였다. 새로운 계열 프로펠러의 형상을 설계함에 있어 기존의 계열 프로펠러와는 달리 선택된 반류분포의 회전방향 평균 반류분포를 입력자료로 하여 반경방향 부하분포와 코오드 방향 부하분포를 동일하게 유지하면서 피치 및 캠버의 형상을 결정하였다. 또한 코오드 길이, 두께, 스큐 및 레이크 분포와 같은 형상은 최근 실적선 프로펠러의 형상 특성을 정형화하여 선택되었기 때문에 초기설계시 설계된 형상이 최종 설계 프로펠러의 형상과 크게 다르지 않을 것으로 생각되어 초기성능을 보다 정확하게 추정할 수 있게 하였다. 설계된 계열 프로펠러는 날개수 4개인 프로펠러를 대상으로 날개 전개면적비 4개($A_{E}/A_{O}$=0.3, 0.45, 0.6, 0.75)에 대하여 각 전개면적비에서 평균피치비를 5개(P/D=0.5, 0.65, 0.8, 0.95, 1.1)로 변화시켜 총 20개의 프로펠러로 구성되었으며 KD-프로펠러 씨리즈(KRISO-DAEWOO Propeller Series)라 명명하였다. 설계된 계열 프로펠러들에 대하여 단독특성시험, 캐비테이션 관찰시험, 변동압력 계측시험을 수행하였다. 프로펠러 단독특성 시험결과의 회귀해석결과로 부터 $B_{P}-\delta$ 곡선을 도출하여 초기설계 단계에서 최적 프로펠러 직경등을 쉽게 결정할 수 있게 하였다. 기준으로 선택된 반류분포(2700TEU 콘테이너선의 반류) 후류에서 프로펠러 추력계수 및 캐비테이션 수를 체계적으로 변화시킨 상태에서 캐비테이션 관찰시험 및 변동압력계측시험을 수행하였다. 양력면이론에 의한 비정상 프로펠러 성능해석에 의해 계산된 최대 국부양력계수 ($C^{max}_{l,0.8R}$)와 국부캐비테이션 수(${\sigma}_0=\frac{p-p_v}{\frac{1}{2}{\rho}V^2_{0.8R}}$)를 기준으로 캐비테이션 관찰시험 결과를 정리하여 KD-캐비테이션 챠트를 도출하였다. 기존의 캐비테이션 챠트는 균일류중의 시험 결과를 정리하여 작성되었으나 KD-캐비테이션 챠트는 반류분포중에서 시험된 프로펠러 관찰시험 결과로 부터 도출되었으므로 초기설계 단계에서 보다 정확한 캐비테이션 발생량 추정이 가능하리라 예상된다.

• 한국초지조사료학회지
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• 제6권1호
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• pp.38-43
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• 1986

본(本) 연구(硏究)는 임간초지개량(林間草地改良)과 관리(管理) 및 이용(利用)의 기초자료(基礎資料)를 얻고자 차광정도(遮光程度)를 0%구(區)(自然光狀態), 25%, 50%, 75%차광구(遮光區)를 설치(設置)하고 Orchardgrass, Timothy, Perennial ryegrass를 '84년(年) 8월(月) 25일(日)에 파종(播種)하여 목초(牧草)의 동사(凍死) 및 월동전(越冬前) 초기생육특성(初期生育特性)을 조사(調査)하였던바 그 결과(結果)를 요약(要約)하면 다음과 같다. 1. 차광정도(遮光程度)에 따른 근장(根長), 분얼수(分蘖數), 발근수(發根數) 및 발근장(發根長)의 생육정도(生育程度)는 자연광상태(自然光狀態)${\geqq}$25%차광구(遮光區)>50% 차광구(遮光區) >75% 차광구순(遮光區順)이었으며(P<0.05), 초장(草長) 및 엽신장(葉身長)의 생육(生育)은 자연광상태(自然光狀態)<25%차광구(遮光區)<50%차광구(遮光區)${\geqq}$75%차광구순(遮光區順)이었다(P<0.05). 2. 차광정도(遮光程度)에 따른 동사율(凍死率)은 자연광상태(自然光狀態)가 4.7%, 25%차광구(遮光區)는 6.2%, 50%차광구(遮光區)는 11.8%, 75%(遮光區)는 22.2%를 보여 차광정도(遮光程度)가 많을수록 동사율(凍死率)은 증가(增加)하였다(P>0.05). 초종별(草種別)로는 Orchardgrass가 10.1%, Timothy가 9.5%, Perennial ryegrass가 14.2%를 나타내었다. 3. 차광정도(遮光程度)에 따른 초종별(草種別) 동사율(凍死率)과 월동전(越冬前) 초기(初期) 생육형질(生育形質)과의 관계(關係)는 분얼수(分蘖數), 발근수(發根數), 발근장(發根長)과는 고도(高度)의 부(負)의 상관관계(相關關係)를 보였으나, 초장(草長) 및 엽신장(葉身長)과는 정(正)의 상관관계(相關關係)를 나타내었다. 4. 차광정도(遮光程度)에 따른 월동전(越冬前) 순동화율(純同化率)은 자연광상태(自然光狀態)가 10.98, 25%차광구(遮光區)가 11.52, 50%차광구(遮光區)가 9.81, 75%차광구(遮光區)가 $6.12g/m^2/day$을 보여 차광(遮光)이 많을수록 감소(減少)하는 경향(傾向)이며, 초종별(草種別)로는 Orchardgrass가 8.58, Timothy가 8.53, Perennial ryegrass가 $11.71g/m^2/day$을 나타내었다. 동사율(凍死率)과 월동전(越冬前) 순동화율(純同化率)과는 부(負)의 상관관계(相關關係)(r=-0.5943*)를 나타내었다.

• 한국잡초학회지
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• 제14권3호
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• pp.212-222
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• 1994

다양(多樣)한 재배양식(栽培樣式), 건답직파(乾畓直播), 담수직파(湛水直播) 및 이앙재배조건하(移秧栽培條件下)에서 제초제(除草劑) butachlor 및 thiobencarb에 대한 벼와 피의 해부형태학적(解剖形態學的) 반응차이(反應差異)가 검토되었다. 파종(播種) 및 이앙(移秧)후 5일(日)째에 Thiobencarb를 추천량(推薦量)의 배양(倍量)인 4,200g ai/ha를 토양처리(土壤處理)한 후(後) 10일 및 20일째에 외부형태(外部形態) 및 해부학적(解剖學的) 반응(反應)을 조사(調査)하였다. 1. 건답(乾畓)에서는 피만 제(第) 1엽(葉) 전개후(展開後) 출엽정지현상(出葉停止現狀)이 있었고 담수(湛水)에서는 표면(表面)벼의 지상부(地上部)가 억제되었고 피의 전반적인 생육억제(生育抑制)가 나타났다. 2. 건답(乾畓)에서의 초장(草長)은 무처리(無處理)에 대비(對比)하여 벼가 11~26%, 피는 83%, 담수(湛水)에서는 벼가 46~56%, 피는 82% 억제되었다. 건답(乾畓)에서의 근장(根에長서)은 벼 3%이내, 피는 21%였고 담수(湛水)벼는 78~85%, 피는 83% 억제(抑制)되었고 이앙(移秧)된 8일묘는 10% 내외의 경미한 정도였다. 3. 피, 표면(表面)벼 및 토중(土中)벼의 징상부 생체중(生體重)은 건답직파(乾畓直播)에서 각각 무처리(無處理)에 대비(對比)하여 68, 50, 25% 순(順)이었고, 지하부(地下部) 생체중(生體重)은 각각(各各) 54, 27, 50% 억제되었으나 담수조건(湛水條件)에서 지상부(地上部)가 각각(各各) 62, 60, 38%, 지하부(地下部)가 60, 67, 60% 억제되었으며 이앙(移秧)벼는 지상부(地上部) 및 지하부(地下部)가 각각(各各) 10, 30%로 경미(輕微)하게 억제(抑制)되었다. 4. 건답조건(乾畓條件)에서 토중(土中)벼의 엽령(棄齡)과 제2엽신장(第2葉身長)이 각각(各各) 무처리(無處理)에 대비(對比)하여 25, 34% 억제되었고 피는 엽령(葉齡)이 40%, 제(第) 2엽신장(葉身長)이 100% 각각(各各) 억제되었다. 그러나 담수(湛水)에선 침엽시기(針葉時期)에 있어서 생장(生長)이 정지(停止)된 상태(狀態)로 100% 억제(抑制)됨을 보였다. 한편 이앙묘(移秧苗)는 엽초장만이 약(約) 25% 억제(抑制)되었을 뿐이다. 5. 중경장(中莖長)은 20일째 건답(乾畓)에선 무처리(無處理)에 대비(對比)하여 64%, 담수(湛水)에선 32% 억제율(抑制率)을 보였다. 6 줄기횡단부(橫斷部)의 조직반응(組織反應)은 건답조건(乾畓條件)에서 토중(土中)벼의 엽시원체(葉始原體) 위축(萎縮)과 피의 Twist 현상(現狀)과 간엽발생(間葉發生)이 있었으며 담수조건(湛水條件)에서 표면(表面)벼의 조직(組織)이 심하게 위축(萎縮)되었고 피는 통엽(筒葉)이 발생되었다. 7. 줄기종단부(縱斷部)의 반응(反應)은 건답(乾畓)의 세포(細胞)가 액포화(液胞化)되고 규칙성(規則性)을 잃었고, 담수표면(湛水表面)벼와 분제조직(分製組織)이 위축(萎縮)되고 피의 분제조직(分製組織) 신장(身長)이 억제되고 세포(細胞)의 액포화(液胞化) 현상(現狀)이 나타났다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• Nuclear Engineering and Technology
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• 제47권4호
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• pp.479-487
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• 2015

The thallium-doped sodium iodide [NaI(Tl)] scintillation detector is preferred as a gamma spectrometer in many fields because of its general advantages. A silicon photomultiplier (SiPM) has recently been developed and its application area has been expanded as an alternative to photomultiplier tubes (PMTs). It has merits such as a low operating voltage, compact size, cheap production cost, and magnetic resonance compatibility. In this study, an array of SiPMs is used to develop an NaI(Tl) gamma spectrometer. To maintain detection efficiency, a commercial NaI(Tl) $2^{\prime}{\times}2^{\prime}$ scintillator is used, and a light guide is used for the transport and collection of generated photons from the scintillator to the SiPMs without loss. The test light guides were fabricated with polymethyl methacrylate and reflective materials. The gamma spectrometer systems were set up and included light guides. Through a series of measurements, the characteristics of the light guides and the proposed gamma spectrometer were evaluated. Simulation of the light collection was accomplished using the DETECT 97 code (A. Levin, E. Hoskinson, and C. Moison, University of Michigan, USA) to analyze the measurement results. The system, which included SiPMs and the light guide, achieved 14.11% full width at half maximum energy resolution at 662 keV.

• Asian-Australasian Journal of Animal Sciences
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• 제25권11호
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• pp.1595-1604
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• 2012

Two studies were conducted to investigate the effects of anti-diarrhoeal herbs on growth performance, nutrient digestibility, and meat quality in pigs. In Exp 1, 150 weanling-growing piglets (average BW = $7.5{\pm}0.24$ kg, average age = $27{\pm}1$ d) were allotted into one of the five dietary treatments, including: i) CON, basal diet, ii) DP, basal diet+1 g/kg date pits, iii) JH, basal diet+0.5 g/kg Japanese-honeysuckle, iv) HCT, basal diet+1 g/kg houttuynia cordata thunb, and v) LE, basal diet+1 g/kg laquer tree extract. From wk 0 to 5, the JH, HCT and LE groups presented higher (p<0.05) ADFI, ADG and gain/feed ratio (G/F) than CON and DP groups. During wk 5 to 10, Pigs fed JH, HCT and LE diets indicated higher (p<0.05) ADG and ADFI than the pigs fed CON and DP diets. During the entire experimental period, a significant increase of ADG appeared in JH, HCT and LE (p<0.05). Pigs fed JH, HCT and LE diets got a higher (p<0.05) ADFI than the pigs fed CON and DP diets. Pigs fed diets with supplementations of herb additives revealled lower (p<0.05) score of diarrhea pigs during d 2 to d 6 compared with pigs fed CON diet. In Exp 2, 60 growing-finishing barrows and gilts (average BW = $54.10{\pm}1.20$ kg, average age = $54{\pm}3$ d) were allotted to three treatments: i) CON, basal diet; ii) YG, basal diet+1 g/kg yellow ginger and iii) HR, basal dietary+1 g/kg hoantchy root, respectively. From wk 0 to 5, Dietary supplementation of YG and HR enhanced (p<0.05) ADG. No difference was found between YG and HR treatments. During, wk 5 to 10, ADG also was observed higher in YG and HR treatments than CON group (p<0.05). Additional, YG had the highest ADG (p<0.05) among treatments. There was always an increase of ADG in YG and HR (p<0.05) through all periods. HR treatment showed a lower (p<0.05) score of diarrhoeal pigs on d 1and d 2 compared with CON treatment. Pigs fed YG and HR diets had a higher (p<0.05) longissimus muscle area (LMA) than pigs fed CON diet. In conclusion, anti-diarrhoeal herbs can improve growth performance, and prevent diarrhea incidence in pigs, it can also increase LMA in finishing pigs.

• 한국습지학회지
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• 제22권2호
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• pp.153-160
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• 2020

미세플라스틱 관련 대부분의 연구에서는 미세플라스틱(MP)을 5mm 미만의 플라스틱 입자로 정의하고 있다. 미세플라스틱은 자연계에 광범위하게 분포함으로써 인간과 환경에 잠재적 위험성이 높아지고 있는 물질이다. 특히 미세플라스틱은 인간을 포함하여 살아있는 생명체에게 물리적 영향을 줄 뿐만 아니라 신진대사와 호르몬 등과 같은 생태적 기능에 심각한 영향을 줄 수 있다. 따라서 본 연구는 환경에서 미세플라스틱의 근원, 경로 및 영향에 대한 이해를 돕기 위해 수행되었다. 미세플라스틱은 본질적으로 1 차 및 2 차 미세플라스틱으로 분류되며, 물리적 및 화학적 특성에 따라 분류되기도 한다. 미세플라스틱의 주요 경로는 강우유출수와 폐수를 통한 배출이며, 하천과 하구역을 거쳐 해양과 같은 대규모 수역으로 이동한다. 미세플라스틱은 폐수 처리 과정에서 크게 제거되기 때문에 폐수처리장 유출수의 미세플라스틱 농도는 강우유출수 내 농도보다 상대적으로 낮게 나타난다. 그러나 폴리머의 분포 측면에서는 폐수가 강우유출수보다 다양한 폴리머 종류를 포함하고 있는 것으로 나타났다. 폐수와 강우유출수에서 발견되는 일반적인 폴리머 유형은 폴리프로필렌(PP), 폴리염화비닐(PVC), 폴리스티렌(PS), 폴리에틸렌(PE) 및 폴리에틸렌테레프탈레이트(PET) 등으로 나타났다. 환경에서 지속적으로 배출이 증가하고 있는 미세플라스틱의 수는 인간과 다른 생명체에게 미래 위험을 줄 수 있다. 그 동안 미세플라스틱에 대한 연구 결과물의 수가 증가함에도 불구하고 환경에 미치는 영향을 완화하기 위한 구체적 규제 및 관리 전략을 수립하기에는 많은 추가 연구가 필요한 것으로 나타났다.

• International Journal of Automotive Technology
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• 제4권2호
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• pp.77-86
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• 2003

How to compare the environmental damage caused by vehicles with different foe]s and drive trains\ulcorner This paper describes a methodology to assess the environmental impact of vehicles, using different approaches, and evaluating their benefits and limitations. Rating systems are analysed as tools to compare the environmental impact of vehicles, allowing decision makers to dedicate their financial and non-financial policies and support measures in function of the ecological damage. The paper is based on the "Clean Vehicles" research project, commissioned by the Brussels Capital Region via the BIM-IBGE (Brussels Institute for the Conservation of the Environment) (Van Mierlo et at., 2001). The VriJe Universiteit Brussel (ETEC) and the universite Libre do Bruxelles (CEESE) have jointly carried out the workprogramme. The most important results of this project are illustrated in this paper. First an overview of environmental, economical and technical characteristics of the different alternative fuels and drive trains is given. Afterward the basic principles to identify the environmental impact of cars are described. An outline of the considered emissions and their environmental impact leads to the definition of the calculation method, named Ecoscore. A rather simple and pragmatic approach would be stating that all alternative fuelled vehicles (LPG, CNG, EV, HEV, etc.) can be considered as ′clean′. Another basic approach is considering as ′clean′ all vehicles satisfying a stringent omission regulation like EURO IV or EEV. Such approaches however don′t tell anything about the real environmental damage of the vehicles. In the paper we describe "how should the environmental impact of vehicles be defined\ulcorner", including parameters affecting the emissions of vehicles and their influence on human beings and on the environment and "how could it be defined \ulcorner", taking into account the availability of accurate and reliable data. We take into account different damages (acid rain, photochemical air pollution, global warming. noise, etc.) and their impacts on several receptors like human beings (e.g., cancer, respiratory diseases, etc), ecosystems, or buildings. The presented methodology is based on a kind of Life Cycle Assessment (LCA) in which the contribution of all emissions to a certain damage are considered (e.g. using Exposure-Response damage function). The emissions will include oil extraction, transportation refinery, electricity production, distribution, (Well-to-Wheel approach), as well as the emission due to the production, use and dismantling of the vehicle (Cradle-to-Grave approach). The different damages will be normalized to be able to make a comparison. Hence a reference value (determined by the reference vehicle chosen) will be defined as a target value (the normalized value will thus measure a kind of Distance to Target). The contribution of the different normalized damages to a single value "Ecoscore" will be based on a panel weighting method. Some examples of the calculation of the Ecoscore for different alternative fuels and drive trains will be calculated as an illustration of the methodology.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.479-485
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• 2022

At the Korea Institute of Radiological and Medical Sciences, physical human phantoms were developed to evaluate various radiation protection quantities, based on the mesh-type reference computational phantoms of the International Commission on Radiological Protection. The physical human phantoms were fabricated such that a radiophotoluminescent glass dosimeter (RPLGD) with a Tin filter, namely GD-352M, could be inserted into them. A Tin filter is used to eliminate the overestimated signals in low-energy photons below 100 keV. The measurement uncertainty of the RPLGD reader system based on GD-352M should be analyzed for obtaining reliable protection quantities before using it for practical applications. Generally, the measurement uncertainty of RPLGD systems without Tin filters is analyzed for quality assurance of radiotherapy units using a high-energy photon beam. However, in this study, the measurement uncertainty of GD-352M was analyzed for evaluating the protection quantities. The measurement uncertainty factors in the RPLGD include the reference irradiation, regression curve, reproducibility, uniformity, energy dependence, and angular dependence, as described by the International Organization for Standardization (ISO). These factors were calculated using the Guide to the Expression of Uncertainty in Measurement method, applying ISO/ASTM standards 51261(2013), 51707(2015), and SS-ISO 22127(2019). The measurement uncertainties of the RPLGD reader system with a coverage factor of k = 2 were calculated to be 9.26% from 0.005 to 1 Gy and 8.16% from 1 to 10 Gy. A blind test was conducted to validate the RPLGD reader system, which demonstrated that the readout doses included blind doses of 0.1, 1, 2, and 5 Gy. Overall, the E_n values were considered satisfactory.