• Nuclear Engineering and Technology
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• 제51권8호
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• pp.1916-1938
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• 2019

The objective of this paper is to discuss the modeling principles of phenomena governing core degradation/melting and in-vessel melt relocation during severe accidents in light water reactors. The proposed modeling approach has been applied in the development of a new accident simulation package, COMPASS (COre Meltdown Progression Accident Simulation Software). COMPASS can be used either as a stand-alone tool to simulate in-vessel meltdown progression up to and including RPV failure, or as a component of an integrated simulation package being developed in Korea for the APR1400 reactor. Interestingly, since the emphasis in the development of COMPASS modeling framework has been on capturing generic mechanistic aspects of accident progression in light water reactors, several parts of the overall model should be useful for future accident studies of other reactor designs, both PWRs and BWRs. The issues discussed in the paper include the overall structure of the model, the rationale behind the formulation of the governing equations and the associated simplifying assumptions, as well as the methodology used to verify both the physical and numerical consistencies of the overall solver. Furthermore, the results of COMPASS validation against two experimental data sets (CORA and PHEBUS) are shown, as well as of the predicted accident progression at TMI-2 reactor.

• 한국CDE학회논문집
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• 제19권4호
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• pp.316-323
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• 2014

This paper proposes the 3D modeling and simulation technique for predicting the integrated performance of combat vehicle. To consider the practical driving and firing condition of a combat vehicle, the full vehicle model, which can define the six degrees-of-freedom of vehicle motion and various firing angles, is developed. The critical design parameters such as the stiffness and damping coefficient of suspension system are applied to construct the analysis model of vehicle. A simple ballistic model, which incorporates the empirical interior ballistic model and the point mass trajectory model, is built to estimate the firing range and the firing recoil force. To predict the integrated performance and analyze the effect of system parameters, MATLAB/SIM-ULINK model of a combat vehicle for performing the real time simulation is also developed. Several simulation tests incorporating the road bump and the firing recoil force are presented to confirm the effectiveness of the proposed vehicle model.

• 한국콘텐츠학회논문지
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• 제17권9호
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• pp.331-340
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• 2017

본 연구의 목적은 간호 시뮬레이션 교육에 있어 심리적 안전 개념의 명확한 속성을 규명하고 파악하여 다양한 시뮬레이션 교육에서 간호학생의 심리적 안전을 향상시킬 수 있는 교육환경 조성에 기여하고자 함이다. Walker와 Avant (2010)의 개념분석 단계를 사용하여 15개의 심리적 안전과 관련된 문헌을 선정하여 분석하였다. 간호 시뮬레이션 교육에서 심리적 안전의 속성으로는 다음 4가지가 도출되었다: 1) 편안한 느낌이나 상태; 2) 두려움 없이 행동할 수 있는 상태; 3) 조직에 대하여 신뢰할 수 있는 느낌; 그리고 4) 자신에게 무해하다는 느낌. 본 연구를 통하여 밝혀진 선행요인, 속성, 결과 등을 고려하여 심리적 안전을 보장하도록 하는 학습환경을 조성한다면 시뮬레이션 교육의 학습효과를 극대화할 수 있을 것으로 기대된다.

• 한국간호교육학회지
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• 제27권1호
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• pp.68-79
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• 2021

Purpose: This study aimed to identify the educational needs of nurses and nursing students for the development of a simulation module of home visiting care for frail, elderly people. Methods: Focus group interviews were conducted with 15 home visiting nurses working in public health centers and 14 nursing students who experienced home visiting from September 10 to October 10, 2018. Results: Bloom's taxonomy of learning objectives, namely, cognitive, affective, and psychomotor domains was used as a framework for data analysis. The defined educational needs for each domain were as follows: "understanding frail, elderly people" for the cognitive domain; "intervention for mental health" and "building a therapeutic relationship" for the affective domain; and "nursing skills", "health education for healthy lifestyles", "referral to the community resource connection", "protection for visiting nurses" for the psychomotor domain. Conclusion: Based on the findings of this study, a simulation module of home visiting care for frail, elderly people can be developed and used for nursing students and nurses to strengthen the capacity for home visiting care.

• Advances in aircraft and spacecraft science
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• 제9권5호
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• pp.367-375
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• 2022

Modeling the properties of complex alloys such as nickel superalloys is an extremely challenging scientific and engineering task. The model should take into account a large number of uncorrelated factors, for many of which information may be missing or vague. The individual contribution of one or another chemical element out of a dozen possible ligants cannot be determined by traditional methods. Moreover, there are no general analytical models describing the influence of elements on the characteristics of alloys. Artificial neural networks are one of the few statistical modeling tools that can account for many implicit correlations and establish correspondences that cannot be identified by other more familiar mathematical methods. However, such networks require careful tuning to achieve high performance, which is time-consuming. Data preprocessing can make model training much easier and faster. This article focuses on combining physics-based deep network configuration and input data engineering to simulate the solvus temperature of nickel superalloys. The used deep artificial neural network shows good simulation results. Thus, this method of numerical simulation can be easily applied to such problems.

• 방사성폐기물학회지
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• 제21권1호
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• pp.175-182
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• 2023

APro, a modularized process-based total system performance assessment framework, was developed at the Korea Atomic Energy Research Institute (KAERI) to simulate radionuclide transport considering coupled thermal-hydraulic-mechanical-chemical processes occurring in a geological disposal system. For reactive transport simulation considering geochemical reactions, COMSOL and PHREEQC are coupled with MATLAB in APro using an operator splitting scheme. Conventionally, coupling is performed within a MATLAB interface so that COMSOL stops the calculation to deliver the solution to PHREEQC and restarts to continue the simulation after receiving the solution from PHREEQC at every time step. This is inefficient when the solution is frequently interchanged because restarting the simulation in COMSOL requires an unnecessary setup process. To overcome this issue, a coupling scheme that calls PHREEQC inside COMSOL was developed. In this technique, PHREEQC is called through the "MATLAB function" feature, and PHREEQC results are updated using the COMSOL "Pointwise Constraint" feature. For the one-dimensional advection-reaction-dispersion problem, the proposed coupling technique was verified by comparison with the conventional coupling technique, and it improved the computation time for all test cases. Specifically, the more frequent the link between COMSOL and PHREEQC, the more pronounced was the performance improvement using the proposed technique.

• Structural Engineering and Mechanics
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• 제89권2호
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• pp.199-211
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• 2024

The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C⁰ continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C¹ continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

• 한국멀티미디어학회논문지
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• 제23권7호
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• pp.830-839
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• 2020

As a popular mathematical framework for modeling decision making, Markov decision process (MDP) has been widely used to solve problem in many engineering fields. MDP consists of a set of discrete states, a finite set of actions, and rewards received after reaching a new state by taking action from the previous state. The objective of MDP is to find an optimal policy, that is, to find the best action to be taken in each state to maximize the expected discounted reward of policy (EDR). In practice, MDP is typically unknown, so simulation-based policy improvement (SBPI), which improves a given base policy sequentially by selecting the best action in each state depending on rewards observed via simulation, can be a practical way to find the optimal policy. However, the efficiency of SBPI is still a concern since many simulation samples are required to precisely estimate EDR for each action in each state. In this paper, we propose a method to select the best action accurately in each state using a small number of simulation samples, thereby improving the efficiency of SBPI. The proposed method accumulates the simulation samples observed in the previous states, so it is possible to precisely estimate EDR even with a small number of samples in the current state. The results of comparative experiments on the existing method demonstrate that the proposed method can improve the efficiency of SBPI.

• 한국항공우주학회지
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• 제36권11호
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• pp.1112-1120
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• 2008

현대 실시간 분산 시뮬레이션은 실기동-가상-구성급을 연동한 합성전장 환경 구축과 무기체계 전 수명주기를 지원하는 시뮬레이션 기반 획득 실현을 위한 개발환경 구축에 노력을 경주하고 있다. 이에 본 논문에서는 정찰용 무인기 개념연구 단계에서 적용된 체계 분석 및 설계를 통합한 UML 모델링 및 시뮬레이션 개발 환경에 대해서 서술한다. 또한, 체계 분석 및 설계를 효율적으로 수행하기 위해서 UML 시뮬레이션과 X-Plane 가시화를 연동한 통합 프레임워크를 제안하고, 구현 내용, 실험 결과 분석 및 결론에 대해서 기술한다.

• 한국시뮬레이션학회논문지
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• 제15권1호
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• pp.87-95
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• 2006

사이버 공격에 대한 새로운 보안시스템의 성능을 검증하기 위해서는 실 네트워크상에서의 검증이 필요하다. 하지만 현실적으로 대규모 분산 네트워크 환경에서의 검증은 어렵다. 이에 성능 검증을 위해 대규모 가상 네트워크 시뮬레이션 시스템이 필요하다. 본 논문에서는 대규모 네트워크를 표현할 수 있고, 프로세스 기반 사건 중심 시뮬레이션 시스템인 SSFNet을 사용하였다. 하지만 대규모 분산 네트워크상에서 보안시스템의 시뮬레이션을 SSFNet에서 수행할 수가 없다. 확장된 SSFNet내에는 IDS(Intrusion Detection System)의 보안모듈이 구성요소로 추가되었다. 추가적으로 IDS는 Snort의 기능을 모델링하여 구현하였다. 네트워크 시뮬레이션의 패킷을 쉽게 조작할 수 있도록 자바언어를 사용하여 패킷조작기를 개발하였다. 최종적으로 개발된 IDS와 패킷 조작기를 기능 검증을 위해 시뮬레이션을 수행하였다. 확장된 SSFNet은 향후 대규모 네트워크의 보안 시스템 시뮬레이터로 사용할 수 있다.