Development of Independent Target Approximation by Auto-computation of 3-D Distribution Units for Stereotactic Radiosurgery

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.

보조 도선과 Annular Gap을 추가한 PCS 대역 마이크로스트립 패치 안테나 설계

최경식,윤종섭,류미라,이원희,허정,Choi, Kyoung-Sik,Yoon, Jong-Soeb,Ryu, Mi-Ra,Lee, Won-Hui,Hur, Jung 한국전자파학회 2001 한국전자파학회논문지 Vol.12 No.3

In this paper, we designed microstrip patch antenna to enhance the weak point of general microstrip patch antenna that has narrow bandwidth and analyzed that. To reduce reactance in probe feed antenna, capacitive gap added to the patch. Using single patch and auxiliary wire, makes dual frequency resonant. So bandwidth is improved and gain also becomes higher. To verify with experiment, PCS band antenna is designed, fabricated. For PCS band antenna, bandwidth is 180 MHz in VSWR<1.5 and gain is 8.6 dBi. 본 논문에서는 마이크로스트립 패치안테나의 단점인 협대역을 개선하기위해 안테나를 설계, 분석하였다. Probe 급전 방식의 안테나에서 reactance 성분을 줄이기 위해 capacitive gap을 추가하였다. 단일 패치와 보조도선을 사용하여 이중공진모드를 형성하였다. 이로 인해 대역폭이 증가되었고, 이득도 향상되었다. 이를 실험적으로 검증하기위해 PCS 주파수 대역의 안테나를 설계, 제작하였다. 제작된 PCS 주파수 대역 안테나의 측정 결과 는 VSWR,1.5에서 대역폭이 190 MHz이고, 이득은 8.6dB이다.

폐형광등 수거체계 개선을 통한 이동연소 온실가스 저감량 산정연구

최경식 ( Kyoung-sik Choi ) 한국환경기술학회 2017 한국환경기술학회지 Vol.18 No.2

Waste fluorescent lamp, Collection monitoring system, Optimal path system, Greenhouse gas 폐형광등 수거유통구조를 무선 통신 기능(WCDMA)을 이용한 송신 모듈을 부착하여 운영한다는 가정과 폐형광등 적재율이 80%이상이 되면 수거한다는 가정으로 수거체계 경로 최적화시스템을 구축하였다. 본 연구에서는 개발된 최적화 시스템을 적용하였을 경우 차량 운행거리 및 시간을 단축할 수 있어 연료 사용에 따른 온실가스 배출량 저감을 산정하고자 하였다. 폐형광등 수거지점 380개소를 갖고 있는 경기도 지역의 한 도시를 선정하고 자료 조사를 통하여 대량 배출 12개 지점을 선정하였으며 그 중 10개 지점이 적재율 80%이상인 것으로 나타났다. 시스템을 적용시킨 결과 10개 지점을 송신모듈 없이 경유하는 경우 거리가 19.8 km이었던 것이 시스템을 적용시킨 결과 14.6 km로 5.2 km 단축되는 것으로 나타났다. 연료 사용량과 온실가스 배출량을 산정하기 위해 주 1회 운행하는 연비 3.0km/ℓ인 1톤 차량을 이용하여 연료 사용량을 산정한 결과 연료 사용량의 경우 개선 전 4191.2ℓ/년, 개선 후 3090.9ℓ/년으로 연간 1100.3ℓ의 연료를 절약할 수 있는 것으로 나타났다. 온실가스 배출량을 산정한 결과 개선 전 11.0tCO₂-eq/년, 개선 후 8.1tCO₂-eq/년으로 연료사용량의 경우 26%의 감축률을 보이는 것으로 나타났다. The collection system of optimal path for waste fluorescent lamps was constructed on the assumption that the waste fluorescent lamp collection structure was operated with a transmission module using wireless communication function (WCDMA) and that the collected fluorescent light collection rate was more than 80%. In this study, the reduction of greenhouse gas emission was estimated by fuel use of collection vehicle because it could shorten the distance and time of the vehicle driving when the developed optimization system was applied. The city of Gyeonggi Province, which has 380 collection points of waste fluorescent lamps, was selected, and 12 collection points were selected through data surveys. Of these, 10 were points found to have a collection rate of over 80%. As a result of applying the system, the distance of 19. 8km was shortened to 14.6km by 5.2 km. In order to estimate fuel consumption and greenhouse gas emissions, the fuel consumption was estimated using a one-ton vehicle with a fuel consumption of 3.0 km/L at once a week. As a result, fuel consumption was 4191.2 L/year before improvement and 3090.9 L/year after improvement. It resulted in saving 1100.3 liters of fuel per year. GHG emissions were estimated to be 8.1 tCO₂-eq/year from 11.0 tCO₂-eq/year after improvement. Ultimately, energy saving was 26% due to the application of waste fluorescent lamp collection system.

토지이용도에 따른 수질변화 예측을 위한 비점오염원 모델 적용

최경식(Kyoung Sik Choi),나은혜(Eun Hye Na),박석순(Seok Soon Park) 한국물환경학회 2000 한국물환경학회지 Vol.16 No.5

This paper describes the application of a distributed non-point source model called AGNPS(Agricultural Non-Point Sources) to Bulno Cheon watershed. Deagu, Korea. All the required databases (soils, land use and topography) were assembled at 1: 250.000 scale. The study watershed was discretized into 85 grids, of which size is 500m x 500m. The model was calibrated and verified with the measured data. including the runoff flow, chemical oxygen demand, and total nitrogen. The model results displayed a good agreement with the field measurements for both calibration and verification. The validated model was utilized to predict an impact of urbanization on the runoff flow and pollution loads. The predicted results indicated that an urbanization would cause the runoff flow to increase significantly, but the pollution loads to somewhat decrease if all the livestock feedlots are eliminated from the study watershed with urbanization.

자발적 탄소시장형성에 따른 정책지원방안에 관한 연구

최경식 ( Kyoung Sik Choi ),하상안 ( Sang An Ha ) 한국환경과학회 2011 한국환경과학회지 Vol.20 No.2

Non-Annex I parties announced the voluntary emission reduction targets including the U.S. in the conference of party. NAMAs would be focused to solve the negotiation clue for the post-kyoto regime. Since the country would not be involved in Annex I parties, the voluntary carbon market would be created for the greenhouse gas reduction targets. According to Bali Roadmap, voluntary carbon market should be constructed by the MRV manners since this country does not belong to Annex I parties. Carbon point system would be proposed by the ways of the international voluntary emission reduction credit. The voluntary carbon market should involve the potential GHG reduction credit and link with the ETS in the country. This study proposed the way of linkage between ETS and voluntary carbon market including the carbon-point system.

기후변화 대응을 위한 지방자치단체의 교토 메커니즘 활용방안

최경식(Kyoung-Sik Choi) 경기연구원 2007 경기논단 Vol.9 No.4

Climate change in fact is observed in diverse range of areas of our lives, and the analysis that its influence will become even more severe is dominant. Although Korea is not burdened with the obligation for reduction of greenhouse gas based on Kyoto Protocol, we are confronted with dire situation of establishing countermeasures in advance in whatever format possible as the possibility of our participation is continually increasing. Climate change and United Nations Framework Convention on Climate Change not only affect Korea nationally but also impart direct influence on local government including daunting of industrial growth of autonomous regions and reduction in yield in the agricultural and fisheries industries. Given the situation that we need to face up to the inevitability of having to participate in the obligation to reduce greenhouse gas of the international society, it must be emphasized that efforts to cope with such by local government must commence today rather than tomorrow. The efforts of the local government in coping with climate change include elicitation of areas affected by climate change and extent of the influence, establishment of source of emission of greenhouse gas and emission inventory, preparation of means of mitigation through identification of internal and external reduction options and establishment of utilization strategy, preparation of adaptation method with considerations for such mitigation, and execution of risk management and continuous management. Area of Kyoto Mechanism that can be utilized for such purposes is the Clean Development Mechanism(CDM). Already, A lot of local governments are participating in the CDM market and are focusing on project development. Although it is true that CDM projects bring about affirmative effects including profit, reduction of greenhouse gases and nurturing of advanced environmental industry to the regional autonomous organizations, there is need for strategic pursuit and management with considerations for diverse range of issues in pursuing such projects. The Government is executing support activities for coping with climate change by local government through the 4th National Comprehensive Countermeasures against Climate Change, under the administration of Ministry of Environment. This program includes support projects with diverse range of formats including computation of emission quantity, consultation on means of adaptation and mitigation, establishment of means of utilizing Kyoto Mechanism such as System of Trading of Emission Rights, and execution of model project. Conversion into low carbon society has already begun. People claim that climate change is serious crisis for us. However crisis may also be an opportunity. Accordingly, regional autonomous organizations must endeavor to put their efforts to cope with the United Nations Framework Convention on Climate Change or for conversion into low carbon society. It is anticipated that CDM projects will function as outstanding lever in the midst of the current events.

다종 센서간 위상 차이를 이용한 충격 위치추정 기법

최경식(Kyoung-Sik Choi),최영철(Young-Chul Choi),박진호(Jin-Ho Park),김환우(Whan-Woo Kim) 한국소음진동공학회 2008 한국소음진동공학회 학술대회논문집 Vol.2008 No.11

하수방류에 따른 하천의 용존산소변화 예측

최경식(Kyoung Sik Choi),성동권(Dong Gwon Sung),김태근(Tae Keun Kim) 한국하천호수학회 2001 생태와 환경 Vol.34 No.2

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연구논문 : 신재생에너지 적용에 따른 화력발전 경제성분석

최경식 ( Kyoung Sik Choi ) 한국환경영향평가학회 2014 환경영향평가 Vol.23 No.1

Since the Renewable Portfolio Standard (RPS) would be started in 2012, the use of renewable energy should be 11% of total energy use including bio-fuel in 2030. The economic efficiency for renewable energy in B power plant was considered with the bio-diesel, wind power and solar power. The Net Present Value (NPV) and Benefit/Cost Ratio (BC) were used for the economic efficiency with the cost and benefit analysis. In case of bio-diesel, the cost resulted from the fuel conversion and the benefit would be created with trade and environmental improvement. With regard to wind power and solar power, the construction cost would be required and benefit factors would be same as the bio-diesel. The wind power was the best of economic efficiency of renewable energy as the results of NPV and BC ratio. Whereas, the market of wind power was very popular and the techniques of wind power has been developing rapidly.

다종 센서간 위상 차이를 이용한 충격 위치추정 기법

최경식(Choi, Kyoung-Sik),최영철(Choi, Young-Chul),박진호(Park, Jin-Ho),김환우(Kim, Whan-Woo) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.11

In a nuclear power plant, loose part monitoring and its diagnostic technique is one of the major issues for ensuring the structural integrity of the reactor system. Typically, accelerometers are mounted on the surface of a reactor vessel to localize impact location cavsed by the impact of metallic substances on the reactor system. However, in some cases, the number of the accelerometers is not enough to estimate the impact location precisely. In such a case, one of alternative plan is to utilize another type sensors that can measure the vibration of the reactor structure even though the measuring frequency ranges are different from each others. The AE sensors installed on the reactor structure can be utilized as additional sensors for loose part monitoring. In this paper, we proposed a new method to estimate impact location by using both accelerometer signal and AE signal, simultaneously. The feasibility of the proposed method is verified by an experiment. The experimental results demonstrate that we can enhance the reliability and precision of the loose part monitoring.