• Title, Summary, Keyword: 방향 의존도

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말단팬텀에서 X-선 빔의 방향의존성에 관한 이론적 계산

  • 김광표;윤석철;윤여창;김종수;홍종숙
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.57-62
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    • 1996
  • ANSI N13.32는 손목팬텀과 손가락팬텀에서 말단선량계의 특성조사를 위하여 방향의존성인자를 선량계의 성능평가에 적용하도록 권고하고 있다. 본 연구에서는 말단선량의 정확한 선량평가를 위하여 ANSI N13.32에 제안된 팬텀과 동일하게 모사하고 그 팬텀내의 7mg/$\textrm{cm}^2$ 깊이에서 단일에너지를 가진 광자의 선량당량환산인자 및 방향의존성인자를 MCNP 전산코드를 사용함으로써 계산하였다. 또한 본 연구의 최종목적인 ISO Narrow X-선 빔에 의해 조사된 손가락팬텀에서 선량당량환산인자 및 방향의존성인자를 도출하였다. 전산 수행한 결과 낮은 전압에서 발생된 X-선 빔인 경우, 팬텀의 주축을 따라 수평회전각이 증가할수록 방향의존성인자가 크게 감소하며, 한편 높은 전압에서 생성된 X-선 빔인 경우, 수평회전각이 증가할수록 방향의존성인자간 처음에는 근소하게 감소하지만 90。까지는 증가하고 있음을 알 수 있었다.

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Determining Direction of Conditional Probabilistic Dependencies between Clusters (클러스터간 조건부 확률적 의존의 방향성 결정에 대한 연구)

  • Jung, Sung-Won;Lee, Do-Heon;Lee, Kwang-H.
    • Journal of Korean Institute of Intelligent Systems
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    • v.17 no.5
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    • pp.684-690
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    • 2007
  • We describe our method to predict the direction of conditional probabilistic dependencies between clusters of random variables. Selected variables called 'gateway variables' are used to predict the conditional probabilistic dependency relations between clusters. The direction of conditional probabilistic dependencies between clusters are predicted by finding directed acyclic graph (DAG)-shaped dependency structure between the gateway variables. We show that our method shows meaningful prediction results in determining directions of conditional probabilistic dependencies between clusters.

Determination of Dose Correction Factor for Energy and Directional Dependence of the MOSFET Dosimeter in an Anthropomorphic Phantom (인형 모의피폭체내 MOSFET 선량계의 에너지 및 방향 의존도를 고려하기 위한 선량보정인자 결정)

  • Cho, Sung-Koo;Choi, Sang-Hyoun;Na, Seong-Ho;Kim, Chan-Hyeong
    • Journal of Radiation Protection and Research
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    • v.31 no.2
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    • pp.97-104
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    • 2006
  • In recent years, the MOSFET dosimeter has been widely used in various medical applications such as dose verification in radiation therapeutic and diagnostic applications. The MOSFET dosimeter is, however, mainly made of silicon and shows some energy dependence for low energy Photons. Therefore, the MOSFET dosimeter tends to overestimate the dose for low energy scattered photons in a phantom. This study determines the correction factors to compensate these dependences of the MOSFET dosimeter in ATOM phantom. For this, we first constructed a computational model of the ATOM phantom based on the 3D CT image data of the phantom. The voxel phantom was then implemented in a Monte Carlo simulation code and used to calculate the energy spectrum of the photon field at each of the MOSFET dosimeter locations in the phantom. Finally, the correction factors were calculated based on the energy spectrum of the photon field at the dosimeter locations and the pre-determined energy and directional dependence of the MOSFET dosimeter. Our result for $^{60}Co$ and $^{137}Cs$ photon fields shows that the correction factors are distributed within the range of 0.89 and 0.97 considering all the MOSFET dosimeter locations in the phantom.

ANSI 13.32 말단부 팬템에 의한 열형광말단선량계의 방향의존성 연구

  • 김종수;윤석철;윤여창
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.889-894
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    • 1995
  • 본 연구에서는 ANSI N13.32(1995)에서 제시한 손가락, 손목/발목 기준 팬텀(1)을 설계 제작하여 Teledye사의 말단선량계(finger와 wrist dosimeter)에 대한 방향의존성 실험을 수행하였다. 방사선원으로는 PTB 2차 베타표준선원 $^{204}$Tl(0.24 MeV), $^{90}$ sr/Y(0.8 MeV) 그리고 $^{l37}$ Cs(0.66 MeV) 표준 감마선원을 사용하였으며, 말단선량계로는 LiF Teflon(D-LiF-7-0.13)을 사용하였다. 90$^{\circ}$ 에서 $10^{\circ}$ 까지 20$^{\circ}$ 씩 수직과 수평으로 팬텀을 회전하여 정상각과 비정상각에 대한 상대응답을 제시하였다. 실험결과 90$^{\circ}$에서 모든 선량계는 잘 일치하였다. $^{90}$ Sr/Y은 50$^{\circ}$ 정도에서 다소 방향의존성이 적은 결과를 보였으며, $^{204}$ TI는 20$^{\circ}$에서 최소 13% 정도의 심한 방향의존성이 나타났다. 또한 $^{137}$Cs은 $10^{\circ}$에서도 최대 10.6% 정도의 적은 방향의존성을 나타냈다. 본 실험의 결과로부터 말단선량계는 저에너지와 낮은 투과 방사선[2]에서 심하게 방향의존성이 나타남을 알 수 있었다.

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The comparison of angular dependence for optical stimulated luminescence dosimeter(OSLD) and electronic personal dosimeter(EPD) used in Diagnostic Radiology (영상의학과에서 사용되는 광자극 형광선량계와 전자식 개인선량계의 방향 의존성 비교)

  • Kwon, Soon-mu;Park, Jeong-kyu;Kim, Boo-soon
    • Journal of Digital Contents Society
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    • v.16 no.3
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    • pp.463-470
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    • 2015
  • The angular dependence of active dosimeters, EPD, is analysed and compared with that of passive dosimeters, OSLD, after evaluating their relative response and uncertainty of measurement, where it is known that the personal use of them has been increased recently. There appeared a minor variation for average relative response of OSLD in the horizontal and vertical directions within the range $0^{\circ}{\sim}{\pm}90^{\circ}$, which are 0.97 and 0.95 respectively. The variations of angular dependence in the same situations with OSLD are 0.65 and 0.62, respectively, which also reveals a negligible effect on the overall uncertainty. EPDs within the interval $0^{\circ}{\sim}{\pm}60^{\circ}$ for horizontal and vertical directions are 0.94 and 0.97, respectively. These satisfy the requirements of IEC 61526. Uncertainties about the dependence of direction from horizontal and vertical directions are 0.44, 0.40, respectively. The impact of these uncertainties on the overall uncertainty was negligible. However, we observed a significant change in reactivity: the relative reactivities for $+90^{\circ}$ and $-90^{\circ}$ from the horizontal direction are 0.60, 0.37, while that form vertical direction is 0.06. The direction dependence of OSLD was superior to EPD in the range of $0^{\circ}{\sim}{\pm}90^{\circ}$. There appeared a rapidly changing structural features in EPD response for a certain direction. Therefore, we conclude that concurrent use of passive dosimeters and auxiliary dosimeter provides accurate data for personal dose measurements.

A Study on the Angular Dependence of the PB-3 Dosimeter Using Teledyne 9150 TLD Reader System (열형광선량계(도시메터타입 : PB-3)의 방향의존성에 관한 연구)

  • Son, Jung-Kwon;Kim, Jong-Kyung;Yoon, Suk-Chul
    • Journal of Radiation Protection and Research
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    • v.19 no.3
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    • pp.189-198
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    • 1994
  • An angular dependence experiment was made and a performance test of the Teledyne dosimetry system was done in accordance with the ANSI N13.11-1992. The angular dependence experiment was performed with $^{137}Cs$ and low energy X-ray beam. Teledyne dosimetry system performed well at the $0^{\circ}$ angle of incidence for all dosimeters in both vertical and horizontal irradiations. It would have easily passed the 0.5 tolerance limit. But the dosimetry system was not performed well at the ${\pm}60^{\circ}$ angle of incidence for low energy X-ray beam. The accuracy for $^{137}Cs$ beam at all angles of incidence was within the 0.5 tolerance limit. Therefore performance of the dosimetry system could be considered acceptable in case that the dosimeter is irradiated to $^{137}Cs$ beam. However, it could not be acceptable for the dosimeter irradiated to low energy X-ray, especially at more than ${\pm}40^{\circ}$

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Ultracompact Polarization-Insensitive Directional Coupler based on Double Sandwiched Rib-Type Waveguide (이중 샌드위치 Rib-형 도파로에 기초한 초소형 편광 무의존성 방향성 결합기)

  • Ho, Kwang-Chun
    • The Journal of The Institute of Internet, Broadcasting and Communication
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    • v.14 no.3
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    • pp.171-176
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    • 2014
  • The polarization characteristics of ultracompact polarization-insensitive directional coupler (PIDC) based on double sandwiched rib-type waveguide are explored in detail by using longitudinal modal transmission-line theory (L-MTLT). To obtain the polarization-insensitive condition of ultracompact directional coupler, the coupling length and coupling efficiency as functions of the refractive index and thickness of sandwiched rib-type waveguide are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the ultracompact polarization-insensitive coupler with hundreds of micrometer scales is realized by properly choosing structural and material parameters of double sandwiched layers. Furthermore, the influence of fundamental mode profile, which is distributed in lateral waveguide of coupler, on the coupler performance has been investigated.

Implementation of Polarization-Insensitive Directional Coupler using Curved Waveguides (곡면형 도파로를 사용한 편광 무의존성 방향성 결합기의 구현)

  • Ho, Kwang-Chun
    • The Journal of The Institute of Internet, Broadcasting and Communication
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    • v.16 no.1
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    • pp.239-244
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    • 2016
  • The polarization characteristics of polarization-insensitive directional coupler based on double sandwiched rib-type and curved waveguides are explored in detail by using conformal transformation method (CTM) and longitudinal modal transmission-line theory(L-MTLT). To obtain the polarization-insensitive condition of polarization-insensitive curved directional coupler(PI-CDC), the coupling length and coupling efficiency according to the inner radius of PI-CDC are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the PI-CDC with a few micrometer scales can be realized by properly choosing the curvature and structural and material parameters of double sandwiched layers. Furthermore, the mode profiles propagating through PI-CDC are evaluated, and the influence on coupler performance has been investigated.

The Light Sensitivity and Angular Dependence of the $Mg_2SiO_4$:Tb(MSO-S) TLD ($Mg_2SiO_4$:Tb(MSO-S) TLD의 광감수성과 방향의존성)

  • Kim, Do-Sung;Park, Myeong-Hwan
    • Journal of Radiation Protection and Research
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    • v.23 no.1
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    • pp.59-63
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    • 1998
  • The light sensitivity and angular dependence of the $Mg_2SiO_4$:Tb(MSO-5) TLD which affect the accuracy of the radiation dose measurement are investigated. Light-induced thermoluminescence of MSO-S TLD under the 200 lux fluorescent and the incandescent lamp for 8 hours are corresponding to 11 and 3 mR exposure, respectively. TL intensity ratio of the incident angle of ${\pm}80^{\circ}$ to normal incidence for MSO-S and badge type MSO-L are about 0.8 and 0.15, respectively.

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