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최경식,오승종,이정우,김정기,서태석,최보영,김문찬,정현태,Choi Kyoung Sik,Oh Seung Jong,Lee Jeong Woo,Kim Jeung Kee,Suh Tae Suk,Choe Bo Young,Kim Moon Chan,Chung Hyun-Tai Korean Society of Medical Physics 2005 의학물리 Vol.16 No.1
정위적 방사선 수술은 한 번에 두 개내 병소에는 고선량의 방사선을 조사하면서, 주위 정상조직에는 최소한의 방사선이 조사되도록 시술하는 치료기법이다. 본 연구는 정위적 방사선 수술시 자동적 치료계획을 수행하기 위하여, 선형가속기와 감마나이프의 다수의 회전중심점을 이용하는 치료계획에 대한 물리적 격자구조에 기반한 새로운 방법을 개발하였다. 최적의 방사선 수술계획은 많은 빔관련 변수들의 조합으로서 만들어진다. 본 연구에서는 선형가속기와 감마나이프 수술시 빔 측면도의 50% 수준에서의 선량분포가 콜리메이터/헬멧의 구멍 크기와 일치하는 점을 이용하여 하나의 회전중심점을 중심으로 선량분포를 구형으로 모델화시켰다. 그리고, 다수의 회전중심점들은 병소내 위치와 크기를 고려한 정육면체 구조와 1×1×1 ㎣의 체적소 단위의 계산에 의해 자동적으로 배치시켰다. 이 기법에 의한 치료계획 방법은 선량체적히스토그램, 선량의 일치성, 선량의 균질성의 병소내 선량분포로서 평가되었다. 그 결과, 새로운 기법은 불규칙한 병소들에 대하여 프로그램 시스템에 의해 빠르게 다수의 회전중심점들을 배치시켰다. 또한, RTOG의 권고사항에 언급된 병소내 선량분포의 일치성, 균질성이 기준을 잘 만족하였고, 병소들은 50% 이상의 등선량 곡선 내에 포함되었다. 이와 같은 성과는 불규칙하게 형성된 병소와 선형가속기나 감마나이프와 같은 다른 치료 장치 기법들에서 특별한 제약없이 보편적으로 적용이 될 수 있을 것으로 생각된다. The stereotactic radiosurgery (SRS) describes a method of delivering a high dose of radiation to a small tar-get volume in the brain, generally in a single fraction, while the dose delivered to the surrounding normal tissue should be minimized. To perform automatic plan of the SRS, a new method of multi-isocenter/shot linear accelerator (linac) and gamma knife (GK) radiosurgery treatment plan was developed, based on a physical lattice structure in target. The optimal radiosurgical plan had been constructed by many beam parameters in a linear accelerator or gamma knife-based radiation therapy. In this work, an isocenter/shot was modeled as a sphere, which is equal to the circular collimator/helmet hole size because the dimension of the 50% isodose level in the dose profile is similar to its size. In a computer-aided system, it accomplished first an automatic arrangement of multi-isocenter/shot considering two parameters such as positions and collimator/helmet sizes for each isocenter/shot. Simultaneously, an irregularly shaped target was approximated by cubic structures through computation of voxel units. The treatment planning method by the technique was evaluated as a dose distribution by dose volume histograms, dose conformity, and dose homogeneity to targets. For irregularly shaped targets, the new method performed optimal multi-isocenter packing, and it only took a few seconds in a computer-aided system. The targets were included in a more than 50% isodose curve. The dose conformity was ordinarily acceptable levels and the dose homogeneity was always less than 2.0, satisfying for various targets referred to Radiation Therapy Oncology Group (RTOG) SRS criteria. In conclusion, this approach by physical lattice structure could be a useful radiosurgical plan without restrictions in the various tumor shapes and the different modality techniques such as linac and GK for SRS.
바이오매스 합성가스를 이용한 엔진 발전 시스템의 경제성 평가
문지홍(Ji Hong Moon),이정우(Jeung Woo Lee),방병열(Byung Ryeul Bang),김세원(Se Won Kim),이은도(Uen Do Lee) 한국열환경공학회 2010 한국열환경공학회 학술대회지 Vol.2010 No.추계
Biomass, a carbon neutral fuel, is one of the fastest growing renewable energy sources. In this study, economic feasibility of small scale power generation system using syngas from biomass has been investigated. Effects of important variables such as capital investment, cost of waste wood, renewable energy certificate(REC), system marginal price(SMP) on the benefit of business have been analyzed. Internal rate of return(IRR) was predicted as 16.90%, which implicates the business is promising based on the assumptions such as SMP of 137 Won/kWh, capital cost of 4.7 billion won, and waste wood price of 30 thousand won. Major factors affecting the benefit of business are as follows; system marginal price, operational rate, capital investment, expenditure of waste wood, certified emission reduction.
분체공학 , 유동층 , 고분자 , 재료 ( 무기 , 유기 ) : 예혼합화염 에어로졸 반응기에서 응집체의 형상 전개
장혁상(Hyuk Sang Chang),장한권(Han Kwon Chang),이정우(Jeung Woo Lee) 한국화학공학회 2001 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.39 No.5
Using a premixed flat flame aerosol reactor, the experimental study on the morphological evolution of the aggregates was done. With the objectives to understand the morphological process of SiO₂ and TiO₂ particle that matches to the cases of the reaction-limited aggregation process and the diffusion-limited aggregation process respectively, the difference in chemical reaction rate of SiCl₄ and TiCl₄ was utilized under given flame temperatures. To evaluate the morphological evolution of the aggregates, the light scattering measurement and electron microscopy coupled with thermophoretic sampling method were used. In the case of SiCl₄ oxidation that produces SiO₂particles, the microscopic observation obtained with respect to the axial position in the reactor showed that the diffusion-limited aggregation was the dominant mechanism in the aggregation process because that the very low reaction rates was maintained excepted the earlier reaction stage in the given reactor temperature profile. In the case of TiCl₄ that maintains the higher reaction rate during the later reaction stage, it was observed that the reaction-limited aggregation process is the main mechanism on the aggregation. According to the results of the light scattering measurements, the fractal dimension of SiO₂ and TiO₂ aggregates was 1.23-1.84 and 2.81-2.94 respectively, and those results are corresponds with the photometric measurement. To observe applicability of TiO₂ particles as photocatalyst, XRD analysis was conducted. TiO₂ particles were generated in our study consisted of anatase mainly that has high photochemical activity.