• Progress in Medical Physics
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• v.18 no.4
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• pp.226-232
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• 2007

We studied a Monte Carlo simulation of the proton beam delivery system at the National Cancer Center (NCC) using the Geant4 Monte Carlo toolkit and tested its feasibility as a dose verification framework. The Monte Carlo technique for dose calculation methodology has been recognized as the most accurate way for understanding the dose distribution in given materials. In order to take advantage of this methodology for application to external-beam radiotherapy, a precise modeling of the nozzle elements along with the beam delivery path and correct initial beam characteristics are mandatory. Among three different treatment modes, double/single-scattering, uniform scanning and pencil beam scanning, we have modeled and simulated the double-scattering mode for the nozzle elements, including all components and varying the time and space with the Geant4.8.2 Monte Carlo code. We have obtained simulation data that showed an excellent correlation to the measured dose distributions at a specific treatment depth. We successfully set up the Monte Carlo simulation platform for the NCC proton therapy facility. It can be adapted to the precise dosimetry for therapeutic proton beam use at the NCC. Additional Monte Carlo work for the full proton beam energy range can be performed.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.109-117
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• 2007

Uncertainty is pervasive in rock slope stability analysis due to various reasons and subsequently it may cause serious rock slope failures. Therefore, the importance of uncertainty has been recognized and subsequently the probability theory has been used to quantify the uncertainty since 1980's. However, some uncertainties, due to incomplete information, cannot be handled satisfactorily in the probability theory and the fuzzy set theory is more appropriate for those uncertainties. In this study the random variable is considered as fuzzy number and the fuzzy set theory is employed in rock slope stability analysis. However, the previous fuzzy analysis employed the approximate method, which is first order second moment method and point estimate method. Since previous studies used only the representative values from membership function to evaluate the stability of rock slope, the approximated analysis results have been obtained in previous studies. Therefore, the Monte Carlo simulation technique is utilized to evaluate the probability of failure for rock slope in the current study. This overcomes the shortcomings of previous studies, which are employed vertex method. With Monte Carlo simulation technique, more complete analysis results can be secured in the proposed method. The proposed method has been applied to the practical example. According to the analysis results, the probabilities of failure obtained from the fuzzy Monte Carlo simulation coincide with the probabilities of failure from the probabilistic analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2058-2062
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• 2009

1992년 한강수계법이 제정되면서 우리나라에 도입된 오염총량관리제는 현재 2차총량관리 시행계획수립 단계에 이르렀다. 오염총량제에서 수질모델은 수계구간별로 설정된 기준유량과 목표수질 조건을 달성하는 지를 판단할 수 있는 도구로 사용되며, 다양한 모델들이 사용되고 있다. 그 중 하천수질모형으로는 주로 QUAL2E, QUALKO, QUALKO2 모형으로 압축할 수 있다. QUAL2E 모형은 1980년대에 개발되어 국내외로 널리 이용하고 있으나 SOD를 0차나 일정량으로 처리하였고, 부착조류에 의한 용존산소 변화와 부유 조류 사멸시 발생하는 유기물이 고려되지 않았다. 또한 용존산소가 부족한 상태에서 반응이 활발한 탈질화과정이 포함되지 않아 이들 반응에 의해 수질이 영향을 받는 하천에 적용하기에는 한계가 있었다. 그리고 QUAL2E 모델은 여러 개의 지류를 가진 대형 하천에는 적용하기 어려운 단점이 있다. 국내에서는 1999년 QUAL2E 모델에 WASP5의 장점을 접목시켜 QUALKO 모델을 개발하였다. 이 모델은 QUAL2E에 부유성 조류의 사멸로 인한 유기물의 내부증가, 탈질화 반응 및 부착식물의 광합성 호흡 과정을 추가한 것이다. 또한 QUAL2E 모델에서 BOD는 CBOD로 입력되고 모의되므로 bottle BOD의 개념이 결여되어 있으므로 이러한 문제점을 보완하고, 조류의 생산 및 사멸에 의한 내부생산 유기물 증가와 탈질화 반응 과정을 추가한 것이다. 우리나라에서 진행되고 있는 총량관리 대상물질은 2010년까지는 $BOD_5$이며, 2011년부터는 일부 지역에 총인이 포함될 예정이다. 2007년에 실험실에서 측정하는 BOD5나 유기성 질소 또는 유기성 인을 그대로 입력하여 계산되고 출력할 수 있으며, 향후 오염총량제의 관리대상항목으로 논의되고 있는 TOC를 모의할 수 있는 QUALKO2가 개발되었다. 이에 본 연구에서는 향후 활용도가 클 것으로 기대되는 QUALKO2 모형에 기존 QUAL2E-UNCAS 모형에 서 수행할 수 있는 불확실성 해석 기법인 Monte Carlo 모의를 가능하도록 모형을 수정하고자 한다. 실제 하천에서의 수질해석에 대한 단순한 표현인 수학적 모형은 불확실성을 내포하고 있으며, Monte Carlo 해석을 사용하여 모형의 불확실도 정량화와 매개변수의 불확실성을 통계학적으로 기술할 수 있다. 또한 각 지점에 대한 계산결과치들에 대해 빈도 및 누가빈도분포 값을 제시함으로서 모형 예측치들의 전반적인 분포경향을 평가할 수 있으며, 하천수질에 대해서 환경기준치를 위배할 가능성을 산정하는데 활용할 수 있다. 우리나라 실정에 맞는 QUALKO2 모형에 Monte Carlo 모의를 통해 신뢰도 기반의 수질해석을 수행하게 된다면 수질정책의 기초자료 제공에 기여할 것으로 판단된다.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.503-510
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• 2020

Concrete is one of the most widely used materials as the shielding structures of a nuclear facilities. It is also the most generated radioactive waste in quantity while dismantling facilities. Since the concrete captures neutrons and generates various radionuclides, radiation measurement and analysis of the sample was fulfilled prior to dismantle facilities. An HPGe detector is used in general for the radiation measurement, and effective correction factors such as geometrical correction factor, self-absorption correction, and absolute detector efficiency have to be applied to the measured data to decide exact radioactivity of the sample. Correction factors are obtained by measuring data using a standard source with the same geometry and chemical states as the sample under the same measurement conditions. However, it is very difficult to prepare standard concrete sources because concrete is limited in pretreatment due to various constituent materials and high density. In addition, the concrete sample obtained by core drill is a volumetric source, which requires geometric correction for sample diameter and self absorption correction for sample density. Therefore in recent years, many researchers are working on the calculation of effective correction factors using Monte carlo simulation instead of measuring them using a standard source. In this study we calculated, using Geant4, one of the Monte carlo codes, the correction factors for the various diameter and density of the concrete core sample at the gamma ray energy emitted from the nuclides ¹⁵²Eu and ⁶⁰Co, which are the most generated in radioactive concrete.

• Progress in Medical Physics
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• v.14 no.4
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• pp.234-239
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• 2003

We examined the variation of percent depth dose (PDD) curves for 10 MV X-rays in the presence of magnetic fields. The EGS4 Monte Carlo code was applied and modified to take account of the effect of electron deflection under magnetic field was used. We defined and tested DI (dose improvement) and DR (dose reduction) to describe variation of PDD curves under various magnetic fields. For a magnetic field of 3 T applied at the depth region of 5-10 cm and field size of 10${\times}$10 $\textrm{cm}^2$, the DI is 1.56 (56% improvement) and DR is 0.68 (32% reduction). We explained the results from the Lorentz law and the concept of electron equilibrium. We suggested that the dose optimization in radiotherapy can be achieved from using the characteristics of dose distributions under magnetic fields.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.187-195
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• 2009

In a fault tree analysis, an uncertainty importance measure is often used to assess how much uncertainty of the top event probability (Q) is attributable to the uncertainty of a basic event probability ($q_i$), and thus, to identify those basic events whose uncertainties need to be reduced to effectively reduce the uncertainty of Q. For evaluating the measures suggested by many authors which assess a percentage change in the variance V of Q with respect to unit percentage change in the variance $\upsilon_i$ of $q_i$, V and ${\partial}V/{\partial}{\upsilon}_i$ need to be estimated analytically or by Monte Carlo simulation. However, it is very complicated to analytically compute V and ${\partial}V/{\partial}{\upsilon}_i$ for large-sized fault trees, and difficult to estimate them in a robust manner by Monte Carlo simulation. In this paper, we propose a method for experimentally evaluating the measure using a Taguchi orthogonal array. The proposed method is very computationally efficient compared to the method based on Monte Carlo simulation, and provides a stable uncertainty importance of each basic event.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2004.11a
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• pp.210-215
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• 2004

In can occur to many problems on progressing step without close scope definition, interrelation definition between activities, resource plan, and schedule plan on planning step. But it have not closely defined performance system on planning step because of many constraints of domestic construction industry. Therefore this paper intends to discuss a method of calculating optimal cost and duration using Linear Programming that solves maximing or minimizing problems among decision making methodology and Monte Carlo Simulation that decreases to probability errors. With outcoms applying Linear programming and Monte Carlo Simulation for calculating optimal cost and duration, follow as : With outcomes applying Monte Carlo Simulation, it could calculate reliable estimator about project duration through removing various constraints. With outcomes applying Linear programming, it could calculate optimal value about project cost through defining various variables and constraints on many activities.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.405-408
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• 2016

Games like Go, Chess, Janggi have helped to brain development of the people. These games are developed by computer program. And many algorithms have been developed to allow myself to play. The person winning chess program was developed in the 1990s. But game of go is too large number of cases. So it was considered impossible to win professional go player. However, with the use of MCTS(Monte Carlo Tree Search) and CNN(Convolutional Neural Network), the performance of the go algorithm is greatly improved. In this paper, using CNN and MCTS were proceeding development of go algorithm. Using the manual of go learning CNN look for the best position, MCTS calculates the win probability in the game to proceed with simulation. In addition, extract pattern information of go using existing manual of go, plans to improve speed and performance by using it. This method is showed a better performance than general go algorithm. Also if it is receiving sufficient computing power, it seems to be even more improved performance.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.54-62
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• 1998

In a plasma etching system, ions become an important parameter in determining the wafer topography which depends on both the physical sputtering mechanism and the chemically enhanced reaction. this paper reports the energy and angular distributions of ions across the plasma sheath using a monte carlo method. The ion distribution is mainly affected by the magnitude of the sheath voltage and by the collision in the sheath. Furthemore, the local potential distribution in a plamsa sheath has been determined by solving the poisson's equation. In th is work, ionic collisions were cosidered in terms of both charge exchange and momentum transfer. The three-dimensional distributions of ions were calculated with varying the input process conditions in the plasma reactor.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.55-62
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• 1999

Monte Carlo ion scattering program is improved with the single scattering methods where the total cross section and the mean free path are calculated as a function of atomic density during ion scattering in matter. The relations among the parameters of incident ions and substrate materials are investigated to the sputtering phenomena. The sputtering yield has been analyzed with the dependence on the incident ion species and energy, incident angle, and surface binding energy. The energy distribution of sputtered particles is discussed.