• Journal of the Society of Naval Architects of Korea
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• v.51 no.3
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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.

• Journal of Korean Home Economics Education Association
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• v.28 no.2
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• pp.51-59
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• 2016

In this study, we identified the theoretical basis of management and planning of life-cycle, the core concept of resource "Administration and Independence," of Home Economics curriculum according to "Notification of Education Ministry #2015-74." First in relation to "management", we identified the systematic theory, the theoretical basis of traditional home management, and diagnosed how this systematic theory is reflected on 2015' curriculum. As a result, the contents of actual curriculum's middle school contents does not include integrally the life related problems that middle students are facing in real life, and it is hard to be convinced what priority the element of selected contents have of several problems. Next, in case of planning of life-cycle that accentuates the importance of life plan corresponding to career orientation it mentions the contents including very comprehensive area such as value, profession, health as well as developmental task, but the fact leaves to be desired that 2015 curriculum is overlooking the importance of financial planning, the international trend.

• Nuclear Engineering and Technology
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• v.45 no.5
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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.

• Journal of The Korean Association of Information Education
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• v.23 no.6
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• pp.655-663
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• 2019

Recent interest in software education has naturally led to interest in computer science. Computer science is the study of theory and principle of computer and computational systems. This knowledge and concept of computer science is fundamental to software education. Recently, "Computer Science (CS) Unplugged", which is an educational method for introducing students to concepts of computer science without using a computer, has been widely used in classes around the world. CS Unplugged is a method for learning the basic principles of computer science through diverse playing activities. The problem, however, is that these CS unplugged activities take place in class without an analysis of how closely they relate to the core subjects learned in real computer science. Therefore, in this study, we will study on the comparison between the core contents of computer science and the core contents of computer science contained in the various activities of CS Unplugged.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.5
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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.

• Journal of the Korean School Mathematics Society
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• v.22 no.2
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• pp.95-113
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• 2019

In this paper, we analyzed the levels of cognitive demand of the tasks for developing t he mathematical core competencies presented in the "Mathematics" textbook of the first y ear of high school developed according to the 2015 revised mathematics curriculum. "Mathematics" textbook included 4999 mathematics tasks, of which 703 were tasks for developing the mathematical competency. Analysis of 703 mathematical tasks according to the analysis framework of Stein, Smith, Henningsen, and Silver (2000) showed that 61.5% of students required high cognitive levels, 38.5% required low cognitive levels, and the types of tasks were as follows: Low-M 1.0%, Low-P 37.5%, High-P 57.8%, High-D 3.7%. It w as found that most of the tasks for the purpose were tasks that led to understanding mathematical concepts, principles, and processes along procedural processes.

• Proceedings of the KSR Conference
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• 2011.10a
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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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• v.8 no.2
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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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• v.27 no.4
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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.

• The Journal of Society for e-Business Studies
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• v.1 no.1
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• pp.27-50
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• 1996

In this paper. we present a definition of the term virtual enterprise (VE) and discuss some related terms and concepts. The definition was given based on Porter's Value Chain Theory. Then we discuss some positioning strategies for entering or joining a virtual enterprise from an executive's viewpoint. which show a framework for making decisions on for what. when and how a (real) enterprise need to participate or form a virtual enterprise and whom the partners should be. The major pert of the paper is on underlying information technologies and architectures for building virtual enterprises. Requirements for modeling virtual enterprises and core technologies needed for implementation are discussed. A virtual enterprise reference architecture based on NIIIP's model is presented. Finally we discuss some points that should. addressed from a macroeconomic and public policies viewpoints. These are the issues of IT standardization and investments in IT infrastructure.