• Title/Summary/Keyword: 몬테카를로 모사

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Assessment of Viral Attenuation in Soil Using Probabilistic Quantitative Model (확률적 정량모델을 이용한 토양에서의 바이러스 저감 평가)

  • Park, Jeong-Ann;Kim, Jae-Hyun;Lee, In;Kim, Song-Bae
    • Journal of Korean Society of Environmental Engineers
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    • v.33 no.7
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    • pp.544-551
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    • 2011
  • The objective of this study was to analyze VIRULO model, a probabilistic quantitative model, which had been developed by US Environmental Protection Agency. The model could assess the viral attenuation capacity of soil as hydrogeologic barrier using Monte Carlo simulation. The governing equations used in the model were composed of unsaturated flow equations and viral transport equations. Among the model parameters, those related to water flow for 11 soil types were from UNDODA data, and those related to 5 virus species were from the literatures. The model compared the attenuation factor with threshold of attenuation to determine the probability of failure and presented the exceedances and Monte Carlo runs as output. The analysis indicated that among 11 USDA soil types, the viral attenuation capacity of loamy sand and sand were far lower than those of clay and silt soils. Also, there were differences in the attenuation in soil among 5 viruses with poliovirus showing the highest attenuation. The viral attenuation capacity of soil decreased sharply with increasing soil water content and increased nonlinearly with increasing soil barrier length. This study indicates that VIRULO model could be considered as a useful screening tool for viral risk assessment in subsurface environment.

Calculation of the Correction Factors related to the Diameter and Density of the Concrete Core Samples using a Monte Carlo Simulation (몬테카를로 전산해석을 이용한 콘크리트 코어시료의 직경과 밀도에 따른 보정인자 계산)

  • Lee, Kyu-Young;Kang, Bo Sun
    • 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.

A Appropriate Flux Generating Conditions for Semiconductor Etching Simulation (반도체 식각 전산모사에 적합한 플럭스 생성 조건)

  • Jeong, Seunghan;Gwun, Oubong;Shin, Seongsik
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.3
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    • pp.105-115
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    • 2015
  • In semiconductor etching simulation, The source modeling for generating plasma species is required. In this paper, we modeled the source of plasma etching process with probability distribution and the feature profile with simple geometry objects, then got the flux on the feature profile. The distance between the source and the cell on the modeling parameters of the source, there are a number of particles to be emitted from a source, there is a number (area of the cell) of the cell on the profile with additional parameters to give the calculation of flux. The flux error ratio on both gaussian(Incident Flux) and cosine probability distribution(Incident Neutral Flux) is much decreased as the number of ray is increased but the processing time is more increased than that. The increase of the number of cell and distance makes increase the flux error ratio and the processing time moderately. In view of the processing time through the experimental results in this paper, it is possible to analogize the calculation of appropriate fluxes.

Depth Dose Distribution of Proton Beams by Variation of Tumor Density using Geant4 (Geant4 전산모사를 이용한 종양의 밀도 변화에 따른 양성자의 선량 분포)

  • Kim, You-Me;Chon, Kwon-Su
    • Journal of the Korean Society of Radiology
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    • v.15 no.6
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    • pp.771-779
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    • 2021
  • It is necessary to overlap several peaks to form spread out Bragg peak (SOBP) in order to cover the tumor volume because a mono-energetic proton beam forms a narrow Bragg peak. The tumor density has been considered as a brain tissue and then the absorbed dose of the tumor is calculated using Monte Carlo simulations. However, densities of tumors were not a constant. In this study, the SOBP of proton beams was calculated according to changing density of tumors by using Geant4. Tumors were selected as 10 mm and 20 mm width which were the treatment range in the brain phantom. The energies and relative weights of the proton beams were calculated using mathematical formula to form the SOBP suitable for the location and size of the tumor. As the density of the tumor was increased, the 95% modulation range and the practical range were decreased, and average absorbed dose in the 95% modulation range was increased. The change of the tumor density affects the dose distribution of the proton beams, which results in short SOBP within the tumor volume. The consideration of the tumor density affects the determination of the range, so that the margin of the treatment volume can be minimized, and the advantages of proton therapy can be maximized.

Dose Assessment of Orbital Adnexa in Electron Beam Therapy for Orbital Lymphoma (안와림프종의 전자선 치료 시 안구 부속기관에 대한 선량평가)

  • Dong Hwan Kim;Yong In Cho
    • Journal of the Korean Society of Radiology
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    • v.18 no.3
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    • pp.283-292
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    • 2024
  • Radiation side effects and complications on the ocular adnexa during electron beam therapy for orbital lymphoma can increase the incidence of posterior subcapsular cataracts. This study simulated a medical linear accelerator and a mathematical model of the eye using monte carlo simulations to evaluate the dose to the ocular adnexa and compare the shielding effectiveness on different parts of the ocular adnexa based on lens shield thickness. The dose assessment results of the ocular adnexa showed that the lens's sensitive area had the highest absorbed dose distribution when no shield was used, followed by the lens's non-sensitive area, the anterior chamber, vitreous humor, cornea, and eyelid in descending order. With the use of a shield, a 2 mm thick shield demonstrated a dose reduction effect of over 90% in the lens's sensitive area, over 83% in the non-sensitive area and anterior chamber, and a dose reduction effect of 30 to 62% in the vitreous body, cornea, and eyelid. For dose reduction in the lens's sensitive area during electron beam therapy for orbital lymphoma, it is necessary to use a shield of at least 2 mm thickness. Additionally, shielding strategies considering the thickness and area of the shield for other ocular adnexa besides the lens are required.

Development of DICOM Convert Program for the Geant4 Monte Carlo Simulation of the Radiotherapy (방사선치료의 Geant4 전산모사를 위한 DICOM 변환 프로그램 개발)

  • Kang, Jeongku;Lee, Dong Joon
    • Progress in Medical Physics
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    • v.24 no.4
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    • pp.259-264
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    • 2013
  • The DICOM converter program of the Geant4 Monte Carlo simulation code for the application of radiotherapy was developed. We analysis the header part of the DICOM file and find various parameters, such as matrix size, pixel size, stored data bits, high bit, and padding values. Especially we evaluate every pixel value of the DICOM files. To conform the exact convert of the pixel values, we developed the verify program. As a result, the DICOM formats generated from difference CT vendors can be converted and verified for Genat4 calculations.

Computer aided simulation of spark plasma sintering process (Part 1 : formulation) (스파크 플라즈마 소결공정의 전산모사(1부 : 수식화))

  • Keum Y.T.;Jean J.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.1
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    • pp.38-42
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    • 2006
  • Spark plasma sintering processes have been rapidly introduced recently to improve the quality and productivity of ceramic products and to solve the problem of environmental pollutions. Sintering temperatures and pressing pressures in the spark plasma sintering process are known to be the important factors highly affecting the quality of the ceramics. In this research, in order to see the effects of sintering temperatures and pressing pressures on the grain growth during the spark plasma sintering process of $Al_2O_3$ the grain growth processes associated with sintering temperatures and pressing pressures are simulated by the Monte Carlo method (MCM) and the finite element method (FEM). In this Part 1, the formulations for the simulation, which is the theoretical background of Part 2, are introduced.

The Comparative Analysis of External Dose Reconstruction in EPID and Internal Dose Measurement Using Monte Carlo Simulation (몬테 카를로 전산모사를 통한 EPID의 외부적 선량 재구성과 내부 선량 계측과의 비교 및 분석)

  • Jung, Joo-Young;Yoon, Do-Kun;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.24 no.4
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    • pp.253-258
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    • 2013
  • The purpose of this study is to evaluate and analyze the relationship between the external radiation dose reconstruction which is transmitted from the patient who receives radiation treatment through electronic portal imaging device (EPID) and the internal dose derived from the Monte Carlo simulation. As a comparative analysis of the two cases, it is performed to provide a basic indicator for similar studies. The geometric information of the experiment and that of the radiation source were entered into Monte Carlo n-particle (MCNPX) which is the computer simulation tool and to derive the EPID images, a tally card in MCNPX was used for visualizing and the imaging of the dose information. We set to source to surface distance (SSD) 100 cm for internal measurement and EPID. And the water phantom was set to be 100 cm of the source to surface distance (SSD) for the internal measurement and EPID was set to 90 cm of SSD which is 10 cm below. The internal dose was collected from the water phantom by using mesh tally function in MCNPX, accumulated dose data was acquired by four-portal beam exposures. At the same time, after getting the dose which had been passed through water phantom, dose reconstruction was performed using back-projection method. In order to analyze about two cases, we compared the penetrated dose by calibration of itself with the absorbed one. We also evaluated the reconstructed dose using EPID and partially accumulated (overlapped) dose in water phantom by four-portal beam exposures. The sum dose data of two cases were calculated as each 3.4580 MeV/g (absorbed dose in water) and 3.4354 MeV/g (EPID reconstruction). The result of sum dose match from two cases shows good agreement with 0.6536% dose error.

Study of Radiation dose Evaluation using Monte Carlo Simulation while Treating Extrahepatic Bile Duct Cancer with High Dose Rate Intraluminal Brachytherapy (간외 담도암 고선량률 관내근접방사선치료 시 몬테카를로 시뮬레이션을 통한 주변장기의 선량평가 연구)

  • Park, Ju-Kyeong;Lee, Seung-Hoon;Cha, Seok-Yong;Lee, Sun-Young
    • The Journal of the Korea Contents Association
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    • v.14 no.2
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    • pp.467-474
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    • 2014
  • The relative dose calculated by MCNPX and the relative dose measured by ionization chamber and solid phantoms evaluated the accuracy comparing with Monte Carlo simulation. In order to apply Monte Carlo simulation the intraluminal brachytherapy of extrahepatic bile duct cancer, 192Ir sealed radioactive source replicate, Bile duct and surrounding organs were made using KMIRD phantom based on a South Korea standard man. To check the absorbed dose of normal organs around bile duct, we set the specific effective energy and initial radioactivity to 1 Ci using MCNPX. Evaluation of the accuracy of the Monte Carlo simulation, the difference of the relative dose is the most 1.96% that satisfy the criteria that is the relative error less than 2% suggested by MCNPX code. In addition, The specific effective energy and absorbed dose of normal organs that were relatively adjacent to bile duct such as right side of kidney, liver, pancreas, transverse colon, spinal cord, stomach and small intestine were relatively high. on the contrary, the organs that were relatively distant to bile duct such as left side of kidney, spleen, ascending colon, descending colon and sigmoid colon were relatively low.

Calculation of Dose Distribution for SBRT Patient Using Geant4 Simulation Code (Geant4 전산모사 코드를 이용한 SBRT 환자의 선량분포 계산)

  • Kang, Jeongku;Lee, Jeongok;Lee, Dong Joon
    • Progress in Medical Physics
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    • v.26 no.1
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    • pp.36-41
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    • 2015
  • The Monte Carlo based dose calculation program for stereotactic body radiotherapy was developed in this study. The Geant4 toolkit widely used in the radiotherapy was used for this study. The photon energy spectrum of the medical linac studied in the previous research was applied for the patient dose calculations. The geometry of the radiation fields defined by multi-leaf collimators were taken into account in the PrimaryGeneratorAction class of the Geant4 code. The total of 8 fields were demonstrated in the patient dose calculations, where rotation matrix as a function of gantry angle was used for the determination of the source positions. The DicomHandler class converted the binary file format of the DICOM data containing the matrix number, pixel size, endian type, HU number, bit size, padding value and high bits order to the ASCII file format. The patient phantom was constructed using the converted ASCII file. The EGSnrc code was used to compare the calculation efficiency of the material data.