• Nuclear Engineering and Technology
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• 제42권1호
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• pp.97-108
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• 2010

Fluid-elastic instability and turbulence-induced vibration of steam generator U-tubes of a nuclear power plant are studied numerically to investigate the effect of design changes of support structures in the upper region of the tubes. Two steam generator models, Model A and Model B, are considered in this study. The main design features of both models are identical except for the conditions of vertical and horizontal support bars. The location and number of vertical and horizontal support bars at the middle of the U-bend region in Model A differs from that of Model B. The stability ratio and the amplitude of turbulence-induced vibration are calculated by a computer program based on the ASME code. The mode shape with a large modal displacement at the upper region of the U-tube is the key parameter related to the fretting wear between the tube and its support structures, such as vertical, horizontal, and diagonal support bars. Therefore, the location and the number of vertical and horizontal support bars have a great influence on the fretting wear mechanism. The variation in the stability ratios for each vibrational mode is compared with respect to Model A and Model B. Even though both models satisfy the design criteria, Model A shows substantial improvements over Model B, particularly in terms of having greater amplitude margins in the turbulence-excited vibration (especially at the inner region of the tube bundle) and better stability ratios for the fluid-elastic instability.

• 대한기계학회논문집B
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• 제32권11호
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• pp.849-855
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• 2008

The paper addresses modeling and analysis of the part load performance of a hybrid fuel cell system integrating a polymer electrolyte membrane fuel cell(PEMFC) and a gas turbine(GT). The system is a pressurized one where the working pressure of the PEMFC is higher than the ambient pressure. In addition to the two major components, the system also includes auxiliary parts such as a steam reformer, a humidifier, and afterburner and so on. Based on design analysis, component off-design models are incorporated in the analysis program and part load operation is simulated. The mode for the part load operation of the PEMFC/GT hybrid system is a variable rotational speed operation. The operating characteristics and variations in the system efficiency and component performance parameters at part load are analyzed.

• 대한공업교육학회지
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• 제44권1호
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• pp.162-189
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• 2019

이 연구의 목적은 아두이노를 활용한 디자인씽킹 기반의 중학생 메이커 교육 프로그램을 개발하고 적용하여 효과를 확인하는 것이다. 메이커 교육 프로그램의 개발은 PDIE모형에 따라 준비, 개발, 실행, 평가의 4단계로 이루어졌다. 이 연구에서는 문헌 고찰을 바탕으로 개발된 메이커 교육 프로그램을 전문가 타당도 검증과 학생 대상 예비 적용을 통해 개선하여 중학교 동아리 수업에 적용하였으며, 양적 및 질적자료의 분석을 바탕으로 효과를 확인하였다. 또한 수업 과정에서 발견된 개선점을 보완하여 프로그램의 개발을 완료하였다. 위와 같은 과정으로 수행된 이 연구의 결과는 다음과 같다. 첫째, 중학교에서 활용할 수 있도록 2015개정 교육과정 분석 내용을 토대로 아두이노 활용 방안과 사회적 관심도를 고려하여 메이커 교육 프로그램의 주제를 선정하였다. 둘째, 선정된 주제를 토대로 개발한 메이커 교육 프로그램은 메이커 기초 학습 4차시와 디자인씽킹 기반의 메이킹 체험 16차시로 구성되어있다. 셋째, 개발된 메이커 교육 프로그램을 중학생 20명을 대상으로 적용한 결과, 중학생의 융합인재소양 향상에 유의미한 효과가 있었지만 기술에 대한 흥미와 기술 분야 진로 지향에는 유의미한 변화가 나타나지 않았다. 하지만 적용 대상학생이 20명이므로 결과를 일반화하기에는 한계가 있다. 넷째, 학습자들은 직접 설계하고 만들어가는 활동에 큰 흥미를 느꼈으며 아두이노를 통해 피지컬 컴퓨팅을 구현했던 경험에 긍정적 가치를 부여했다. 또, 메이커로 활동한 학습자들은 자발적 참여와 공유를 핵심으로 한 메이커 정신을 실천하였다.

• 소음진동
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• 제9권6호
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• pp.1116-1122
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• 1999

HRSG, which is one of main components of the combined cycle power plant,is composed of an inlet duct, a main body and casing, an outlet duct and a stack. It is important to design HRSG wihtin the allowable noise limit. For this purpose, it is necessary to analyze and predict the noise reduction and radiation at HRSG. In this paper, the technology for the noise prediction at each part of HRSG has been based on the empirical and field data, and also the HRSG noise prediction program has been developed. In order to verify the developed technology and program a field test is conducted. The results of noise prediction show good agreement with the measured.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.24-35
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• 2004

In order to analyze the hydrogen distribution during a severe accident in the APR1400 containment, GASFLOW II was used. For the APR1400 NPP, a hydrogen mitigation system is considered from the design stage, but a fully time-dependent, three-dimensional analysis has not been performed yet. In this study GASFLOW code II is used for the three-dimensional analysis. The first step to analysis involving hydrogen behavior in a full containment with the GASLOW code is to generate a realistic geometry model, which includes nodalization and modeling of the internal structures such as walls, ceilings and equipment. Geometry modeling of the APR1400 is conducted using GUI program by overlapping the containment cut drawings in a graphical file format on the mesh view. The total number of mesh cells generated is 49,476. And the calculated free volume of the APR1400 containment by GASFLOW is almost the same as the value from the GOTHIC modeling. A hypothetical SB-LOCA scenario beyond design base accident was selected to analyze the hydrogen behavior with the hydrogen mitigation system. The source of hydrogen and steam for the GASFLOW II analysis is obtained from a MAAP calculation. Combustion pressure and temperature load possibilities within the compartments used in the GOTHIC analysis are studied based on the Sigma-Lambda criteria. Finally the effectiveness of HMS installed in the APR1400 containment is evaluated from the point of severe accident management

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1436-1445
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• 2021

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

• 한국정보교육학회:학술대회논문집
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• 한국정보교육학회 2021년도 학술논문집
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• pp.213-221
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• 2021

4차 산업혁명을 맞이하여 인공지능 교육의 필요성이 증대되었고 코로나19로 인한 온라인 학습 환경은 다양한 인공지능 플랫폼 체험형 수업을 가능하게 하였다. 이 연구에서는 인공지능 플랫폼을 활용하여 인공지능 교육 목표를 달성할 수 있도록 수업안을 개발하여 제안하였다. 활용한 인공지능 플랫폼은 AI for Oceans이며 환경을 위한 프로그램 만들기라는 주제로 6차시 분량의 노벨엔지니어링 기반 STEAM 수업을 설계하였다. 이 모델은 수업의 전체 상황을 아우르며 문제해결의 맥락을 제공한다. 학생들은 AI for Oceans를 체험하며 지도 학습에 대한 충분한 탐색 과정을 거친 후 지도 학습에 대한 이해를 바탕으로 엔트리의 인공지능 블록을 사용하여 환경을 위한 나만의 프로그램을 설계한다. 본 연구에서는 인공지능융합교육을 위하여 인공지능의 원리를 토대로 문제 해결에 활용하여 창의적인 문제해결역량 및 융합적 사고력을 강화하는 것을 목표로 수업안을 개발하여 제시하였다.

• 사물인터넷융복합논문지
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• 제4권1호
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• pp.23-29
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• 2018

본 연구는 국내 융합기술 관련 연구물의 네트워크 분석을 통해 연구동향을 파악하고, 연구특성과 구조, 현황을 분석하는데 목적이 있다. 이를 위해 지난 13년(2005년~2018년)동안 연구명에 '융합기술' 단어를 사용한 학술지 177편의 저자키워드 653개에 대한 네트워크 분석을 실시하였다. 연구결과는 다음과 같다. 첫째, 국내 융합기술 연구는 지난 13년 동안 꾸준히 수행되어 왔으며 주로 융합, 디지털, 기술, 예술디자인 분야에서 활발히 이루어졌다. 둘째, 검색어 빈도분석 결과, '융합기술', '기술융합', '융합', '디자인', '융합교육', 'STEAM', '융합연구', '4차 산업혁명', '특허분석' 등이 융합기술의 주요 키워드로 사용되었다. 셋째, 커뮤니티 분석결과, 5개의 커뮤니티가 분류되었고, 검색어의 특성을 반영해 '나홀로 IT', '융합콘텐츠를 활용한 문화산업', '기술혁신과 연구분석', '융합교육', '기술융합과 특허개발'의 주제가 도출되었다. 이러한 연구결과를 통해 미래사회 융합기술교육 연구의 과제와 방향을 제안하였다.

• Steel and Composite Structures
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• 제42권6호
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• pp.765-777
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• 2022

Ultra high performance concrete (UHPC) can be used in the UHPC-steel composite structures especially for bridge structures to achieve high stiffness and high fatigue resistance with low self-weight. The structural performances of UHPC-steel composite slabs subjected to hogging moment have a significant influence on the global stiffness and durability of UHPC-steel composite structures. In order to study the structural behaviors of non-steam-cured UHPC-steel composite slabs subjected to negative moment, five composite slabs combined the thin UHPC layers to steel plates via shear stud connecters with the diameter of 16mm were fabricated and tested under negative moment. The test program aimed to investigate the effect of stud spacing and longitudinal reinforcement ratios on the failure mode, load-deflection behaviors, cracking patterns, bond-slips, and carrying capacities of composite slabs subjected to negative moment. In addition, direct tensile tests for the dog-bone UHPC specimens with longitudinal reinforcement bars were carried out to study the effect of reinforcement bars on the tensile strength of UHPC in the thin structure members. Based on the experimental results, analytical models were also developed to predict the cracking load and ultimate load of UHPC-steel composite slabs subjected to negative moment.

• 한국안전학회지
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• 제36권3호
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• pp.74-80
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• 2021

Korea Atomic Energy Research Institute (KAERI) has been operating an integral effects test facility, the Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS), according to APR1400 for transient experimental and design basis accident simulation. Moreover, based on the experimental data, the domestic standard problem (DSP) program has been conducted in Korea to validate system codes. Recently, through DSP-05, the performance of the passive auxiliary feedwater system (PAFS) in the event of multiple steam generator tube rupture (MSGTR) has been analyzed. However, some errors exist in the reference input model distributed for DSP-05. Furthermore, the calculation results of the heat loss correlation for the secondary system presented in the technical report of the reference indicate that a large difference is present in heat loss from the target value. Thus, in this study, the reference model is corrected using the geometric information from the design report and drawings of ATLAS. Additionally, a new heat loss correlation is suggested by fitting the results of the heat loss tests. Herein, MSGTR-PAFS accident analysis is performed using MARS-KS 1.5 with the improved model. The steady-state calculation results do not significantly differ from the experimental values, and the overall physical behavior of the transient state is properly predicted. Particularly, the predicted operating time of PAFS is similar to the experimental results obtained by the modified model. Furthermore, the operating time of PAFS varies according to the heat loss of the secondary system, and the sensitivity analysis results for the heat loss of the secondary system are presented.