• 한국유체기계학회 논문집
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• 제17권6호
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• pp.109-114
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• 2014

After the Fukushima accident in 2011, it was revealed that nuclear power plant has the vulnerability to SBO accident and its extension situation without sufficient cooling of reactor core resulting core meltdown and radioactive material release even after reactor shutdown. Many safety systems had been developed like PAFS, hybrid SIT, and relocation of RPV and IRWST as a part of steps for the Fukushima accident, however, their applications have limitation in the situation that supply of feedwater into reactor is impossible due to high pressure inside reactor pressure vessel. The concept of hybrid heat pipe with control rod is introduced for breaking through the limitation. Hybrid heat pipe with control rod is the passive decay heat removal system in core, which has the abilities of reactor shutdown as control rod as well as decay heat removal as heat pipe. For evaluating the cooling performance hybrid heat pipe, a commercial CFD code, ANSYS-CFX was used. First, for validating CFD results, numerical results and experimental results with same geometry and fluid conditions were compared to a tube type heat pipe resulting in a resonable agreement between them. After that, wall temperature and thermal resistances of 2 design concepts of hybrid heat pipe were analyzed about various heat inputs. For unit length, hybrid heat pipe with a tube type of $B_4C$ pellet has a decreasing tendency of thermal resistance, on the other hand, hybrid heat pipe with an annular type $B_4C$ pellet has an increasing tendency as heat input increases.

• 대한조선학회논문집
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• 제51권3호
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• pp.259-264
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• 2014

Tip vortex cavitation (TVC) is important for naval ships and research vessels that require raising the cavitation inception speed to maximum possible values. The concepts for alleviating the tip vortex are summarized by Platzer and Souders (1979), who carried out a thorough literature survey. Active control of TVC involves the injection of a polymer or water from the blade tip. The main effect of such mass injection (both water and polymer solutions) into the vortex core is an increase in the core radius, consequently delaying TVC inception. However, the location of the injection port needs to be selected with great care in order to ensure that the mass injection is effective in delaying TVC inception. In the present study, we propose a semi-active control scheme that is achieved by attaching a thread at the propeller tip. The main idea of a semi-active control is that because of its flexibility, the attached thread can be sucked into the low-pressure region closer to the vortex core center. An experimental study using a scale model was carried out in the cavitation tunnel at the Seoul National University. It was found that a flexible thread can effectively suppress the occurrence of TVC under the design condition for a model propeller.

• 한국가정과교육학회지
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• 제28권2호
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• pp.51-59
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• 2016

본 연구에서는 교육부 고시 교육부 고시 '2015 개정 실과(기술 가정) 교육과정' 내용체계 중 "자원관리와 자립" 영역의 핵심개념인 "관리"와 "생애설계"에 대한 이론적 기초를 살펴보았다. 먼저 "관리"영역과 관련해서는 전통적인 가정관리의 이론적 토대인 체계이론에 대한 내용을 살펴보았으며 이러한 체계이론이 2015년 개정교육과정 내에서는 어떻게 반영되고 있는지를 진단한 결과 현 교육과정의 중학교 내용요소들은 중학생들의 실생활에서 직면하고 있는 생활관련 문제들을 통합적으로 포괄하고 있지 않으며 선별된 내용 요소들 또한 여러 가지 문제 상황 중에서 어느 정도 우선순위를 가지고 있는지 확신하기 어려운 부분이 있다. 다음으로 생애설계의 경우 진로지도에 부합하여 생애설계의 중요성을 강조하고 있기 때문에 발달과업을 비롯하여 가치관, 직업, 건강 등 매우 포괄적인 영역을 망라하여 생애설계의 대한 내용을 언급하고 있지만 2015 개정 교육과정에서는 국제적인 트렌드인 재무설계에 대한 중요성을 간과하고 있다는 사실은 다소 아쉬운 부분이다.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.573-580
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• 2013

The combined effects of reactivity coefficients, along with other core nuclear characteristics, determine reactor core behavior in normal operation and accident conditions. The Power Coefficient of Reactivity (PCR) is an aggregate indicator representing the change in reactor core reactivity per unit change in reactor power. It is an integral quantity which captures the contributions of the fuel temperature, coolant void, and coolant temperature reactivity feedbacks. All nuclear reactor designs provide a balance between their inherent nuclear characteristics and the engineered reactivity control features, to ensure that changes in reactivity under all operating conditions are maintained within a safe range. The $CANDU^{(R)}$ reactor design takes advantage of its inherent nuclear characteristics, namely a small magnitude of reactivity coefficients, minimal excess reactivity, and very long prompt neutron lifetime, to mitigate the demand on the engineered systems for controlling reactivity and responding to accidents. In particular, CANDU reactors have always taken advantage of the small value of the PCR associated with their design characteristics, such that the overall design and safety characteristics of the reactor are not sensitive to the value of the PCR. For other reactor design concepts a PCR which is both large and negative is an important aspect in the design of their engineered systems for controlling reactivity. It will be demonstrated that during Loss of Regulation Control (LORC) and Large Break Loss of Coolant Accident (LBLOCA) events, the impact of variations in power coefficient, including a hypothesized larger than estimated PCR, has no safety-significance for CANDU reactor design. Since the CANDU 6 PCR is small, variations in the range of values for PCR on the performance or safety of the reactor are not significant.

• 정보교육학회논문지
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• 제23권6호
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• pp.655-663
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• 2019

소프트웨어 교육에 대한 관심이 늘어감에 따라 컴퓨터과학에 대한 관심도 높아지고 있다. 컴퓨터과학은 컴퓨터와 컴퓨터시스템의 이론과 원리를 학습하는 학문으로서 이러한 컴퓨터과학의 지식과 개념은 소프트웨어 교육의 근본이라고 할 수 있다. 최근에 컴퓨터를 사용하지 않고 컴퓨터 과학의 핵심 내용을 전달하는 방법으로 컴퓨터과학 언플러그드라는 학습 방법이 전 세계적으로 수업에 많이 활용되고 있다. CS 언플러그드는 다양한 놀이 활동을 중심으로 컴퓨터과학의 원리를 배우도록 하는 학습 방법이다. 그러나 문제는 이러한 CS 언플러그드 활동이 실제 컴퓨터과학에서 배우는 핵심교과와 얼마나 연관성이 있는지에 대한 분석 없이 단순한 놀이 수업으로만 이루어지는 것이다. 따라서 본 연구에서는 컴퓨터과학의 핵심 내용과 CS 언플러그드의 다양한 활동에 들어 있는 컴퓨터과학 핵심 내용을 분석하여 비교 연구를 하고자 한다.

• 한국환경복원기술학회지
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• 제13권5호
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• pp.154-171
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• 2010

This study was performed to show criteria of a National Ecological Network (NEN) for South Korea and it was a part of a study of ecological network for broad areas on national land showed by Ministry of Environment of Korea. After 1970s, many european countries presented methods and criteria not on individual protected area but on networking among many habitats. The PEEN (Pan European Ecological Network) and NATURA 2000 are results of those. In South Korea, concepts and mapping metheods of ecological network was studied but those were not applied to the whole national land because the equality and local specialities were not reflected. So, in this study, we presented the criteria composed of forest, river, wildlife and coastal evaluation items in conservation ecology and showed the mapping method which can applied to the national land. After the evaluation on land area which composed of forest, river and wildlife axis. Core areas were $30,616km^2$, buffer zone were $21,870km^2$ and each accounted for 31% and 22% of the national land. Except for Taebaeck-Gangwon region, whole region's core areas were accounted for 20~30% of it and buffer zone were accounted for 20~25% of it, so these can be applied to the national land with equality and local specialities. Forest axis and river axis were clearly linear and connected, but the wildlife axis was dispersed in point form. Therefore, to apply the NEN, a detailed habitat map is important and the interconnected implementation of forest, river, wildlife, and coastal axis is required.

• 한국학교수학회논문집
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• 제22권2호
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• pp.95-113
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• 2019

본 연구에서는 2015 개정 수학과 교육과정에 따른 고등학교 1학년 <수학>교과서에 제시된 교과 역량을 함양하기 위한 과제의 인지적 요구 수준을 분석하였다. 9종의 <수학>교과서는 4999개의 수학 과제를 포함하였고 그 중 수학 교과 역량을 함양하기 위한 과제는 703개였다. Stein, Smith, Henningsen, & Silver(2000)의 분석틀을 바탕으로 703개의 교과 역량 함양 과제를 분석한 결과, 학생들의 높은 인지적 수준을 요구하는 과제 비율은 61.5%, 학생들의 낮은 인지적 수준을 요구하는 과제 비율은 38.5%였고 그에 따른 과제유형의 비율은 Low-M 1.0%, Low-P 37.5%, High-P 57.8%, High-D 3.7%로 나타나 수학 교과 역량을 함양하기 위한 과제의 대부분이 절차적 과정을 따라 수학적 개념, 원리, 과정 등을 이해하도록 유도하는 과제임을 알 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1263-1268
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• 2011

Rail infrastructure manager and operators shall establish emergency response plans. Emergency Response Planning Activities expanded coincidence events should be modeled. Identify the emergency response organization for the purpose of knowledge is required. In other words, control concepts and skills needed core elements. Structured analysis & design technic methodology is Compared with other modeling techniques through a simple graphical model is visualized. The information contained in a model real problems that considering the state of the system activities, so that knowledge acquired in situations where the modeling becomes possible. In this paper, using structured analysis techniques, infrastructure deployment model of the proposed features. In addition to emergency response planning in the 1960s in Germany, Karl Petrie (Carl Petri) devised various means of modeling the situation presents a Petri net model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.540-546
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• 2014

Recently a new government has announced an action plan known as the government 3.0, which aims to provide customized services for individual people, generate more jobs and support creative economy. Leading on from previous similar initiatives, the new scheme seeks to focus on open, share, communicate, and collaborate. In promoting Government 3.0, the crucial factor might be how to align the core services and policies of Government 3.0 with correspoding technologies. The paper describes the concepts and features of Government 3.0, identifies emerging Internet-based technologies and services toward the initiative, and finally provides improvement plans for Government 3.0. As a result, 10 issues to be brought together include: Smart Phone Applications and Service, Mobile Internet Computing and Application, Wireless and Sensor Network, Security & Privacy in Internet, Energy-efficient Computing & Smart Grid, Multimedia & Image Processing, Data Mining and Big Data, Software Engineering, Internet Business related Policy, and Management of Internet Application.

• East Asian mathematical journal
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• 제27권4호
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• pp.381-389
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• 2011

The flexible mathematical thinking - the ability to generate and connect various representations of concepts - is useful in understanding mathematical structure and variation in problem solving. In particular, the flexible mathematical thinking with the inventive mathematical thinking, the original mathematical problem solving ability and the mathematical invention is a core concept, which must be emphasized in all branches of mathematical education. In this paper, the author considered a case of flexible mathematical thinking with an inventive problem solving ability shown by his student via real analysis courses. The case is on the proofs of the equivalences of three different definitions on the concept of limit superior shown in three different real analysis books. Proving the equivalences of the three definitions, the student tried to keep the flexible mathematical thinking steadily.