이온빔 몬테 카를로 시물레이션 프로그램 개발 및 집속 이온빔 공정 해석

김흥배(Heung-Bae Kim) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.4

Two of fundamental approaches that can be used to understand ion-solid interaction are Monte Carlo (MC) and Molecular Dynamic (MD) simulations. For the simplicity of simulation Monte Carlo simulation method is widely preferred. In this paper, basic consideration and algorithm of Monte Carlo simulation will be presented as well as simulation results. Sputtering caused by incident ion beam will be discussed with distribution of sputtered particles and their energy distributions. Redeposition of sputtered particles that are experienced refraction at the substrate-vacuum interface additionally presented. In addition, reflection of incident ions with reflection coefficient will be presented together with spatial and energy distributions. This Monte Carlo simulation will be useful in simulating and describing ion beam related processes such as Ion beam induced deposition/etching process, local nano-scale distribution of focused ion beam implanted ions, and ion microscope imaging process etc.

수상함에서 발사된 수직 발사 유도탄 초기 거동의 통계적 해석

김경태(Kim, Kyung-Tae) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.9

A vertical launching system(VLS) is a system for holding and firing missiles on surface ships. When a missile is launched in VLS, relative motion between canister and missile and drag force induced by wind can cause initial unstability of a missile. Thus dynamic analysis of initial behavior of vertically launched missile should be performed to prevent collision with any structure of a ship. In this study, dynamic analyses of initial behavior of vertically launched missile are performed using Monte-Carlo simulation, which relys on random sampling and probabilistic distribution of variables. Each parameter related with dynamic behavior of a missile is modeled with probability variables and Recurdyn, a commercial software for multi body dynamic analysis, is used to perform Monte-Carlo simulation. As a result, initial behavior of a missile is evaluated with respect to various performance indexes in a probabilistic sense and sensitivity of the each parameters is calculated.

FORM과 Monte Carlo Simulation을 이용한 솔더조인트의 신뢰성 평가

이억섭(Ouk Sub Lee),허만재(Man Jae Hur),명노훈(No Hoon Myoung),김동혁(Dong Hyeok Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8

The chip and FR-4 board in electronic goods are generally connected by solder joint. In this case, the difference in coefficients of thermal expansion (CTE) in the chip and FR-4 board generates the shear strains in the solder joint and finally makes the solder joint fail when the chip and FR-4 are heated. The magnitude of shear strain and the final failure are influenced by boundary conditions such as the difference of CTE, the height of solder and the distance of the solder joint from the neutral point (DNP). In this paper, the effects of boundary conditions on the failure probability of solder joint are studied by using the failure probability model with the help of the first order reliability method (FORM) and the Monte Carlo Simulation (MCS).

전자빔 몬테 카를로 시물레이션 프로그램 개발 및 전자현미경 이미징 특성 분석

김흥배(Heung-Bae Kim) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.5

Processing of Scanning electron microscope imaging has been analyzed in both secondary electron (SE) imaging and backscattered electron (BSE) image. Because of unique characteristics of both secondary electron and backscattered electron image, mechanism of imaging process and image quality are quite different each other. For the sake of characterize imaging process, Monte Carlo simulation code have been developed. It simulates electron penetration and depth profile in certain material. In addition, secondary electron and backscattered electron generation process as well as their spatial distribution and energy characteristics can be simulated. Geometries that has fundamental feature have been imaged using the developed Monte Carlo code. Two, SE and BSE images generation process will be discussed. BSE imaging process can be readily used to discriminate in both material and geometry by simply changing position and direction of BSE detector. The developed MC code could be useful to design BSE detector and their position. Furthermore, surface reconstruction technique is possibly developed at the further research efforts. Basics of Monte Carlo simulation method will be discussed as well as characteristics of SE and BSE images.

군집분포의 형태와 표본의 크기가 성장혼합모형 분석 결과에 미치는 영향 분석

신택수(Tacksoo Shin) 한국교육평가학회 2011 교육평가연구 Vol.24 No.1

성장혼합모형(Growth Mixture Modeling, GMM)은 모집단 내 성장 형태가 다른 하위집단을 규명하는 기법으로 다양한 연구 문제를 효과적으로 분석할 수 있어 많은 사회과학연구에 적용되고 있다. 이러한 혼합모형(Mixture Modeling)의 효율성에도 불구하고 기술적 측면에서 명확히 검증되어야 할 부분이 있는 것도 사실이다. 특히, 군집분포의 형태가 성장 혼합모형 분석 결과에 지대한 영향을 미칠 수 있음에도 불구하고 이와 관련된 연구는 거의 없다. 이에 본 연구는 혼합모형이론에 근거하여 두 연구조건(군집분포의 형태와 표본의 크기)이 GMM 결과(잠재집단의 수, 성장모수와 소속집단 확률 추정치)에 미치는 영향을 몬테-카를로 시뮬레이션 기법을 이용하여 분석하였다. 연구 결과, 군집분포가 다변량 정규분포를 이루는 경우 잠재집단의 수는 과소추정 되었으며 다변량 비정규분포 조건 하에서는 BIC(Bayesian Information Criterion)와 BLRT (Bootstrap Likelihood Ratio Test)가 정확하게 하위집단의 수를 추정하였다. 하지만, 성장 모수와 집단 소속 확률 추정치는 다변량 비정규분포가 존재할 경우 편향될 가능성이 높은 것으로 나타났다. 표본의 크기가 클수록 안정적인 통계 결과를 얻었으나 그 영향은 상대적으로 작았다. Growth mixture modeling(GMM) is used to find the existence of subgroups, which have distinct growth trajectories. Despite usefulness of mixture modeling, there are some unresolved issues in application of this latent class analysis(LCA). Especially, there has been little study to examine the effects of aggregated distribution shapes on GMM analysis. At this point, this Monte-Carlo simulation study investigated how statistical inferences of GMM including the number of class, latent growth parameter estimates, as well as class probability parameter estimates were influenced by distribution shapes and sample sizes. The results showed that the number of class tended to be underestimated when aggregated distribution was followed by multivariate normality. With the conditions of multivariate nonnormality, BIC(Bayesian Information Criterion) and BLRT(Bootstrap Likelihood Ratio Test) precisely detected the number of subgroups. However, biases of growth and class probability parameter estimates increased under nonnormal aggregated distribution. The larger sample sizes were favorable, while the effects were relatively small.

CNTs 기하학적 파라미터에 따른 폴리머 나노복합재의 퍼콜레이션 임계치 예측 및 전기 전도도 특성 연구

도재혁,나가라잔 라그하반,이종수 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.4

In this study, we investigated the changes in percolation threshold and electrical conductivity for polymer nanocomposites in accordance with geometric parameters of carbon nanotubes(CNTs). CNTs were randomly modeled as line segments, and periodic boundary conditions were applied to the two-dimensional representative volume element (RVE). The entire resistance network of the inner RVE was generated based on the connectivity of intersection points between line segments. The shortest path with the direction of the current between electrodes was used to determine whether percolation occurred. Based on this, the percolation threshold was predicted by conducting a Monte Carlo simulation. The electrical conductivity was predicted using Kirchhoff's current law and the finite element method. We verified the adequacy by comparing our results with other references, and the effects of percolation threshold and electrical conductivity were captured according to geometric parameters. 본 연구에서는 폴리머 나노복합소재에 첨가되는 탄소나노튜브(CNTs)의 기하학적 파라미터에 따른 퍼콜레이션 임계치 예측 및 전기전도도 특성 변화를 관찰하였다. 이를 위해 2차원 대표적 체적 요소(RVE) 내부에 CNTs를 선분으로 난수 모델링을 수행하고 주기경계조건을 적용하였다. CNTs 간의 접촉하는 선분들의 교점과 연결성 정보를 이용하여 RVE 내부의 전체 저항 네트워크를 생성하였다. 두 전극 사이에 흐르는 전류 방향으로 전체 네트워크의 최단 경로를 이용하여 퍼콜레이션 발생 여부를 결정하였다. 이를 기반으로 몬테 카를로 시뮬레이션을 수행해 퍼콜레이션 확률을 예측하고, 키르히호프 전류 법칙과 유한요소법을 이용하여 전기전도도를 예측하였다. 이를 타 참고문헌과 비교하여 그 타당성을 검증하고 CNTs의 기하학적 파라미터가 전기적 특성과 퍼콜레이션 확률에 미치는 영향을 확인하였다.

원통형 조사창에서의 양끝내포선 길이분포를 이용한 절리크기분포 추정 연구

서가현(Ga Hyun Suh),송재준(Jae-Joon Song) 한국암반공학회 2016 터널과지하공간 Vol.26 No.3

본 연구에서는 3차원 원통형 조사창에서의 양끝내포선 길이 분포를 이용하여 절리 직경 분포 추정을 수행하였다. 추정 결과의 수치적인 오차를 줄이기 위하여, 보조변수를 도입한 개선된 방안을 제시하였다. 몬테-카를로 시뮬레이션으로 검증한 결과, 보조변수의 변화에 따라 추정 분포의 진동이 줄어들어 오차가 크게 감소한 것을 확인하였다. 또한 절리 직경의 최적 분포 및 적정한 보조변수 값을 찾기 위한 알고리즘을 제안하였다. A method for estimating rock joint size distribution using contained traces length distribution from 3D cylindrical window survey was suggested. To reduce the numerical error, an improved technique was applied. The accuracy was verified by referring to Monte-Carlo simulation and it was found that the error can be decreased with suitable gamma values.

웨이블릿-몬테 카를로법을 이용한 가상 직물이미지의 모사

김주용 ( Joo Yong Kim ) 한국감성과학회 2004 감성과학 Vol.7 No.3

대칭형 강 사장교의 폐합해석과 시공오차의 예측

이민권(Lee Min Kwon),이해성(Lee Hae Sung) 대한토목학회 2006 대한토목학회논문집 A Vol.26 No.1A

이 논문에서는 캔틸레버 공법으로 시공되는 대칭형 강 사장교의 폐합해석법을 제안한다. 폐합시공 전에는 폐합단면 양쪽에서 두개의 독립적인 구조계가 성립되기 때문에 폐합단면에 적절한 단면력을 가해 주어야만 폐합단면에서 수직 처짐과 회전각에 대한 적합조건을 만족시킬 수 있다. 그러나 실제 시공에서는 폐합단면에 단면력을 재하하는 것이 거의 불가능하기 때문에 시공 중에 실제로 교량에 재하할 수 있는 외력에 의하여 적합조건을 만족시켜야 한다. 이 논문에서는 몇 개 케이블의 무응력 길이와 데릭 크레인의 인양력을 조정하여 적합조건을 만족시킬 수 있는 해석 방법을 제안한다. 적합조건식은 케이블의 무응력 길이와 크레인 인양력에 대하여 비선형이므로 Newton-Raphson 방법에 의하여 반복적으로 푼다. 케이블 부재는 탄성현수선 요소를 사용하여 모델링하였고, 주탑과 거더는 일반적인 3차원 뼈대요소를 사용하여 이산화하였다. 교량의 케이블 무응력 길이와 인양력에 대한 변위 민감도는 평형방정식을 직접 미분하여 계산하였다. 주어진 신뢰도 구간에서 시공 오차를 예측하기 위한 몬테-카를로 모사법을 제안하였다. 제안된 방법을 제 2 진도대교의 폐합시공에 적용하여 그 타당성과 효율성을 검증하였다. This paper presents the closing analysis of a symmetric steel cable-stayed bridge erected by a free cantilever method. Two independent structural systems are formed before the closing procedure of a bridge is performed, and thus the compatibility conditions for vertical displacement and rotational angle are not satisfied at the closing section without the application of proper sectional forces. Since, however, it is usually impossible to apply sectional forces at the closing section, the compatibility conditions should be satisfied by proper external forces that can be actually applicable to a bridge. Unstrained lengths of selected cables and the pull-up force of a derrick crane are adjusted to satisfy nonlinear compatibility conditions, which are solved iteratively by the Newton-Raphson method. Cable members are modeled by the elastic catenary cable elements, and towers and main girders are discretized by linear 3-D frame elements. The sensitivities of displacement with respect to the unstrained lengths of selected cables and the pull-up force of the derrick crane are evaluated by the direct differentiation of the equilibrium equation. A Monte-Carlo simulation approach is proposed to estimate expected construction errors for a given confidence level. The proposed method is applied to the second Jindo Grand Bridge to demonstrate its validity and effectiveness.

베이지언 추론에 기반한 확률론적 피로수명 평가

박명진,김유일 대한조선학회 2019 大韓造船學會 論文集 Vol.56 No.2

In general, fatigue analysis is performed by using deterministic model to estimate the optimal parameters. However, the deterministic model is difficult to clearly describe the physical phenomena of fatigue failure that contains many uncertainty factors. With regard to this, efforts have been made in this research to compare with the deterministic model and the stochastic models. Firstly, One deterministic S-N curve was derived from ordinary least squares technique and two P-S-N curves were estimated through Bayesian-linear regression model and Markov-Chain Monte Carlo simulation. Secondly, the distribution of Long-term fatigue damage and fatigue life were predicted by using the parameters obtained from the three methodologies and the long-term stress distribution.