• Nuclear Engineering and Technology
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• 제56권3호
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• pp.980-992
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• 2024

Steam line break accident (SLB) in the nuclear reactor is one of the representative Non-LOCA accidents in which thermal-hydraulics and neutron kinetics are strongly coupled each other. Thus, the multi-scale and multi-physics approach is applied in this study in order to examine a realistic safety margin. An entire reactor coolant system is modelled by system scale node, whereas sub-channel scale resolution is applied for the region of interest such as the reactor core. Fuel performance code is extended to consider full core pin-wise fuel behaviour. The MARU platform is developed for easy integration of the codes to be coupled. An initial stage of the steam line break accident is simulated on the MARU platform. As cold coolant is injected from the cold leg into the reactor pressure vessel, the power increases due to the moderator feedback. Three-dimensional coolant and fuel behaviour are qualitatively visualized for easy comprehension. Moreover, quantitative investigation is added by focusing on the enhancement of safety margin by means of comparing the minimum departure from nucleate boiling ratio (MDNBR). Three factors contributing to the increase of the MDNBR are proposed: Various geometric parameters, realistic power distribution by neutron kinetics code, Radial coolant mixing including sub-channel physics model.

• 방사성폐기물학회지
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• 제17권1호
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• pp.47-58
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• 2019

The paper presents the results of a multi-criteria comparative evaluation of 12 feasible Russian nuclear energy deployment scenarios with thermal and fast reactors in a closed nuclear fuel cycle. The comparative evaluation was performed based on 6 performance indicators and 5 different MCDA methods (Simple Scoring Model, MAVT / MAUT, AHP, TOPSIS, PROMETHEE) in accordance with the recommendations elaborated by the IAEA/INPRO section. It is shown that the use of different MCDA methods to compare the nuclear energy deployment scenarios, despite some differences in the rankings, leads to well-coordinated and similar results. Taking into account the uncertainties in the weights within a multi-attribute model, it was possible to rank the scenarios in the absence of information regarding the relative importance of performance indicators and determine the preference probability for a certain nuclear energy deployment scenario. Based on the results of the uncertainty/sensitivity analysis and additional analysis of alternatives as well as the whole set of graphical and attribute data, it was possible to identify the most promising nuclear energy deployment scenario under the assumptions made.

• 전기전자학회논문지
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• 제20권1호
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• pp.94-102
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• 2016

본 논문에서는 기계학습 알고리즘을 이용하여 다중물리(Multi-physics) 시뮬레이션의 반복 횟수를 획기적으로 줄일 수 있는 다중물리해석 예측 방법을 제안한다. 기존의 다중물리해석 시뮬레이션의 경우 소요되는 시간과 노력을 줄이기 위해 시뮬레이션 자체에 대한 방법과 환경 개선에 초점이 맞추어져 있으나 본 논문에서는 다중물리 시뮬레이션 결과를 기계학습 알고리즘으로 학습하여 추가적인 시뮬레이션을 수행하지 않고 학습된 기계학습 알고리즘을 사용하여 수십분에서 수시간에 걸리는 다중 물리 해석과 유사한 결과를 수초 내에 예측할 수 있음을 보였다. 기계학습 알고리즘 간의 성능을 비교하여 다중물리해석에 적합한 기계학습 알고리즘을 확인하였으며 가장 우수한 성능을 보인 가우시안 프로세스 회귀(Gaussian Process Regression)의 경우 100개 이하의 학습 샘플만으로도 우수한 예측 결과를 얻어낼 수 있음을 확인하였다. 제안하는 방식을 통해 시뮬레이션을 하고자 하는 모델의 형상이나 재질이 변경될 경우 기존의 시뮬레이션 결과로 학습된 알고리즘이 있다면 시뮬레이션을 반복 수행하기 전에 알고리즘을 이용하여 결과를 예측할 수 있어 시뮬레이션의 반복 횟수를 줄일 수 있을 것으로 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.889-906
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• 2020

Analysis of multi-physics systems and the visualization of simulation data are crucial and difficult in computational science and engineering. In Korea, Korea Institute of Science and Technology Information KISTI developed EDISON, a web-based computational science simulation platform, and it is now the ninth year since the service started. Hitherto, the EDISON platform has focused on providing a robust simulation environment and various computational science analysis tools. However, owing to the increasing issues in collaborative research, data format standardization has become more important. In addition, as the visualization of simulation data becomes more important for users to understand, the necessity of analyzing input / output data information for each software is increased. Therefore, it is necessary to organize the data format and metadata for the representative software provided by EDISON. In this paper, we analyzed computational fluid dynamics (CFD) and computational structural dynamics (CSD) simulation software in the field of mechanical engineering where several physical phenomena (fluids, solids, etc.) are complex. Additionally, in order to visualize various simulation result data, we used existing web visualization tools developed by third parties. In conclusion, based on the analysis of these data formats, it is possible to provide a foundation of multi-physics and a web-based visualization environment, which will enable users to focus on simulation more conveniently.

• Journal of Korean Vacuum Science & Technology
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• 제6권2호
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• pp.67-70
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• 2002

Multi-period low-emissivity (low-e) filters based on [TiO$_2$｜Ti｜Ag｜TiO$_2$] layer structure were designed and fabricated by a RF magnetron sputtering method. Optical, structural, chemical, and electrical properties were investigated with various analytical tools. Interface layers consisting of Ag, Ti, and O were observed next to Ag layers by Rutherford backscattering spectrometry (RBS) analysis. The results show that Ti layers of ~ 1.8 nm protect the Ag layers from oxidation better than those of ~ 1 nm and the optical spectra of the filter with thicker Ti layers are in agreement with the simulated one. The average transmittance of a low-e filter with thicker Ti layers is reduced and the sheet resistance is slightly increased due to the increased Ti thickness.

• Earthquakes and Structures
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• 제23권6호
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• pp.535-547
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• 2022

Handball sport, as its name postulates, is a team sport which highly physical workout. During a handball play, several ball impacts are applied on the hands resulting vibration in the forearm, upper arm, shoulders and in general in whole body. Hand has important role in the handball's game. So, understanding about the dynamics and some issues that improve the stability of the hand is important in the sport engineering field. Ulna and radius are two parallel bones in lower arm of human hand which their ends are located in elbow and wrist joint. The type of the joint provides the capability of rotation of the lower arm. These two bones with their ends conditions in the joints constructs a 4-link frame. The ulna is slightly thinner than radius. So, understanding about hand kinematics in handball's game is an important thing in the engineering field. So, in the current work with the aid of a multi-physics simulation, dynamic stability analysis of the ulna and radius bones will be presented in detail.

• Progress in Superconductivity
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• 제13권1호
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• pp.28-33
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• 2011

Distribution of the local critical temperature and current density in YBCO coated conductors were analyzed using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of the critical temperature and the current density in single and multi bridges. LTSLHPM system was modified for detailed linescan or two-dimensional scan both scanning laser and scanning Hall probe method simultaneously. We analyzed the local critical temperature of single and multi bridges from series of several linescans of scanning laser microscopy. We also investigated local current density and hysteresis curve of single bridge from experimental results of scanning Hall probe microscopy.

• 한국방재학회 논문집
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• 제9권2호
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• pp.1-9
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• 2009

물-결합재비 0.4이하의 고성능 콘크리트 수축 변형을 파악하기 위해 전체 수축을 수분의 외부이동에 의한 건조수축과 수분의 내부소모에 의한 자기수축으로 분리한 후, 자기건조에 의한 상대습도 변화와 변형률의 관계를 묘사하기 위하여 계면역학적 접근법에 의한 습도-변형률 관계를 설정하였다. 이에 대한 검증을 위해 자기수축 시험체에서의 습도-수축 측정을 수행하였으며, 기존 연구 모델인 Tazawa, CEB-FIP 모델에 비하여 측정값과 가장 유사한 결과를 나타내어 본 연구에서의 자기수축모델은 자기건조에 따른 자기수축은 선형성을 나타내는 수분의 외부이동에 의한 수축과는 달리 지수적 관계를 갖는 특성과 초기재령에서의 급속한 자기수축 발현 특성을 적절히 묘사하고 있음을 알 수 있었다. 이 후 본 연구의 수분이동-수축 모델을 반영하여 온도, 수분이동, 변형률 해석의 다중물리 모델 해석과 모형시험체 측정을 수행한 결과 매우 유사한 값을 나타내어 본 연구를 통해 측정된 수분의 내부소모에 의한 습도와 수축변형률을 고려한 다중물리모델은 타당할 것으로 판단된다.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.146-152
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• 2016

본 논문에서는 고정밀 각도 센싱을 요구하는 응용분야에 이용되는 권선형 레졸버의 변압부와 레졸버 파트의 유한요소법 (Finite Element Method, FEM)을 이용한 연동해석을 통해 권선형 레졸버 시스템의 성능을 도출하는 과정을 연구하였다. 외부 인가 전원을 증폭시키는 회전형 변압기부와 증폭된 변압기 출력을 이용하는 레졸버의 회전자 입력부의 연동해석을 통하여 전자기적인 정밀도를 향상시킬 수 있는 권선형 레졸버의 연동해석 모델을 제시하고 출력 신호의 특성을 분석하였다. 회전형 변압기에서 승압된 전압이 레졸버 회전자 권선에 인가될 때 회전자 권선의 임피던스를 고려하여 레졸버 입력 전류를 계산하여야 한다. 따라서 레졸버 회전자 권선부 인터페이스 부분은 회로 모델로 구성하여 변압기의 유한요소 모델, 인터페이스 회로 모델, 레졸버 유한요소 모델을 한 번에 연성해석을 수행하였다. 고정밀 각도 도출을 위해 레졸버 고정자 권선은 32x와 1x의 혼합 권선이 설치되어 있으며 서로간의 자기적인 간섭은 없다. 본 논문에서는 슬롯에 적절한 분포적인 권선법이 제시되어 정현적인 SIN, COS 파형과 이들간의 위상각 $90^{\circ}$를 만족시킬 수 있음을 확인하였다.

• Structural Engineering and Mechanics
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• 제85권6호
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• pp.809-823
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• 2023

In this work, dynamic stability analysis of the ball after contacting with the earth in the volleyball game is presented. Via spherical shell coordinate, the governing equations and general boundary conditions of the ball after contacting with the earth in the volleyball game is studied. Via Comsol multi-physics simulation, some results are presented and a verification between the outcomes is studied. Harmonic differential quadrature method (HDQM) is utilized to solve the dynamic equations with the aid of boundary nodes of the current spherical shell structure. Finally, the results demonstrated that thickness, mass of the ball and internal pressure of the ball alters the frequency response of the structure. One important results of this study is influence of the internal pressure. Higher internal pressure causes lower frequency and hence reduces the stability of the ball.