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양성자 치료에서 Moving Phantom을 이용한 Single Scan PBS와 Layered Rescanning PBS의 선량비교
김경태,김선영,김대웅,김재원,박지연,전상민,Kim, Kyeong Tae,Kim, Seon Yeong,Kim, Dae Woong,Kim, Jae Won,Park, Ji Yeon,Jeon, Sang Min 대한방사선치료학회 2019 대한방사선치료학회지 Vol.31 No.1
목 적: 움직이는 장기에 취약한 Pencil Beam Scanning(PBS)을 보완하기 위해 고안된 Layered Rescanning PBS 기법을 Moving Phantom에 적용하여 Single Scan PBS와 선량비교를 통해 Homogeneity를 비교해 본다. 대상 및 방법: Matrix X(IBA, Belgium)와 Moving Phantom(standard imaging, USA)을 이용하였다. 가상의 tumor $10{\times}10{\times}5cm$에 AP 방향에서 200 cGy의 선량을 조사하였다. 치료계획은 single scan PBS, rescan 4, 8, 12회 총 4가지로 하였고 각 치료계획별로 3번씩 반복 측정하였다. 측정 시 Moving Phantom의 호흡주기는 한 cycle당 4초로 설정 후 S-I 방향 움직임 2 cm으로 설정하였다. 추가로 beam on time을 측정하였다. 결 과: PTV 내에서 $D_{max}$의 평균값은 single scan, 4, 8, 12회 rescan 순서로 각각 $246.47{\pm}18.8cGy$, $223.43{\pm}8.92cGy$, $222.47{\pm}7.7cGy$, $213.9{\pm}6.11cGy$ $D_{min}$의 평균값은 각각 $165.53{\pm}4.32cGy$, $173.13{\pm}11.94cGy$, $184.13{\pm}8.04cGy$, $182.67{\pm}4.38cGy$으로 $D_{mean}$ $192.77{\pm}6.98cGy$, $196.7{\pm}4.01cGy$, $198.17{\pm}4.96cGy$, $195.77{\pm}3.15cGy$으로 측정되었다. 그리고 rescan 횟수가 늘어날수록 Homogeneity Index가 1에 가까워졌으며, beam on time은 평균 2분 15초, 3분 15초, 4분 30초, 5분 37초로 rescan 횟수가 증가할수록 치료시간이 증가되었다. 측정하는 과정에서 MU가 낮은 선량 layer에서는 설정한 rescan 횟수만큼 실제로 rescan하지 못하는 문제점이 발견되었다. 결 론: 장기 움직임이 있는 종양 치료 시 Layered Rescanning PBS을 적용했을 때 single scan PBS보다 균일한 선량분포를 확인할 수 있었다. 그리고 rescan 횟수가 증가할수록 균일한 선량분포를 보였다. single scan PBS와 12회 Layered rescanning 비교 시 HI 수치가 0.32 향상되었다. 추후 연구를 통하여 호흡동조 방사선치료가 불가능환자에게 적용이 가능할 것으로 사료된다. Purpose : We apply the Layered Rescanning PBS designed to complement the Pencil Beam Scanning(PBS), which is vulnerable to moving organs with the Moving Phantom, and compare the homogeneity with the single scan PBS. Methods and materials: Matrix X (IBA, Belgium) and Moving Phantom (standard imaging, USA) were used. A dose of 200 cGy was measured in the AP direction on a hypothetical tumor $10{\times}10{\times}5cm$. The plan type was planned as 4 kinds of sinlge scan PBS, rescan number 4, 8, 12 times. Were measured three times for each types. During the measurement, the respiratory cycle of the Moving Phantom was generally set to 4 seconds per cycle, and the movement radius in the S-I direction was set to 2 cm. In addition, beam on time was measured. Results : The mean values of $D_{max}$ in the PTV were $246.47{\pm}18.8cGy$, $223.43{\pm}8.92cGy$, and $222.47{\pm}7.7cGy$, $213.9{\pm}6.11cGy$ and the mean values of $D_{min}$ were $165.53{\pm}4.32cGy$, $173.13{\pm}11.94cGy$, $184.13{\pm}8.04cGy$, $182.67{\pm}4.38cGy$ and the mean values of $D_{mean}$ $192.77{\pm}6.98cGy$, $196.7{\pm}4.01cGy$, $198.17{\pm}4.96cGy$, $195.77{\pm}3.15cGy$ respectively. As the number of rescanning increased, the Homogeneity Index converged to 1. The beam on time was measured as 2:15, 3:15, 4:30, 5:37 on average. In the measurement process, in the low dose layer of the MU, the problem was found that it was not rescanned as many times as the set number of rescan. Conclusions : In the treatment of tumors with long-term movements, the application of layered rescanning PBS showed a more uniform dose distribution than single scan PBS. And as the number of rescan increase, the distribution of homogeneity is uniform. Compared with single scan plan and 12 rescan plan, HI value was improved by 0.32. Further studies are expected to be applicable to patients who can not be treated with respiratory synchronous radiation therapy.
탄소나노튜브가 분산된 비스무스 텔루라이드 기지 복합재료의 제조 및 열전특성
김경태,장경미,김경주,하국현,Kim, Kyung-Tae,Jang, Kyeong-Mi,Kim, Kyong-Ju,Ha, Gook-Hyun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
Carbon-nanotube-embedded bismuth telluride (CNT/$Bi_2Te_3$) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with $Bi_2Te_3$ alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/$Bi_2Te_3$ composites by spark plasma sintering process at $350^{\circ}C$ for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the $Bi_2Te_3$ matrix. Seebeck coefficient of CNT/$Bi_2Te_3$ composites reveals that the composite has n-type semiconducting characteristics with values ranging $-55\;{\mu}V/K$ to $-95\;{\mu}V/K$ with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.
P형 열전분말의 수소환원처리가 상온열전특성에 미치는 영향
김경태,장경미,하국현,Kim, Kyung-Tae,Jang, Kyeong-Mi,Ha, Gook-Hyun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
Bismuth-telluride based $(Bi_{0.2}Sb_{0.8})_2Te_3$ thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging $400\;nm\;{\sim}\;2\;{\mu}m$. The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at $350^{\circ}C$ for 10 min at the heating rate of $100^{\circ}C/min$ and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity ($0.8\;m{\Omega}{\cdot}cm$) than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.
계통연계인버터와 2단 DC-DC 컨버터로 구성한 전기자동차용 10㎾급 충전기
김경태(Kyeong-Tae Kim),정종규(Jong-Kyou Jeong),추경호(Kyeong-Ho Chu),박승희(Seung-Hui Park),서안식(An-Sik Seo),이슬기(Seul-Gi Lee),이준영(Jun-Young Lee) 전력전자학회 2011 전력전자학술대회 논문집 Vol.2011 No.7
환경오염의 의한 지구온난화가 세계적 이슈가 되고 있으며 화석연료의 고갈 등으로 기존의 자동차들이 점점 설 자리를 잃어 가는 게 현재 상황이다. 따라서 화석연료 자동차를 대체해야하는 많은 새로운 형태의 자동차가 제시 되고 있는데 그중에 현재 가장 경쟁력과 경제성을 가진 전기자동차가 대두되고 있는 시점에 이를 충전하기 위한 여러 장치들이 나오고 있다. 그중에 우리는 3상계통 인버터와 고효율 DC-DC 컨버터로 구성된 충전기를 소개하고자한다.
알파반수석고 치환 고로슬래그 시멘트 모르타르의 경화특성 및 미세구조 분석
김경태 ( Kim Gyeong-tae ),김규용 ( Kim Gyu-yong ),이보경 ( Lee Bo-kyeong ),윤민호 ( Yoon Min-ho ),이상규 ( Lee Sang-kyu ),서원우 ( Seo Won-woo ) 한국건축시공학회 2017 한국건축시공학회 학술발표대회 논문집 Vol.17 No.1
In this study, hardening characteristics and microstructure of blast furnace slag-cement mortar replaced alpha-calcium sulfate hemihydrate were analyzed. As a result of replacing alpha-calcium sulfate hemihydrate with 0, 10, 20, 30%, it was confirmed that the initial and final setting times are faster than that of blast furnace slag-cement mortar. The compressive strength of the specimens containing alpha-calcium sulfate hemihydrate decreased in the range of 42 ~ 76% at age 28 days compared with blast furnace slag-cement mortar. In the case of replacing the alpha-calcium sulfate hemihydrate, the shrinkage did not occur more rapidly than the cement mortar, but the slope of the strain curve showed a linear behavior. The results of scanning electron microscopy images analysis showed that the formation of ettringite was increased at alpha-calcium sulfate hemihydrate replaced mortar.