• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.146-153
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• 2013

CNG buses has contributed to improve air quality in cities. But it is difficult to meet the next emission regulations such as EURO-VI without the help of additional post-processing device. Hydorgen has higher flame speed and lower combustion temperature that make it thermal efficiency increase with leaner operation. Using hydrogen natural gas blend (HCNG) fuel is promising technology which can reduce $NO_x$ and $CO_2$ emissions for a natural gas vehicle. However, fuel flow rate of HCNG should be increased since hydrogen's energy density per volume is much smaller than natural gas. In the present study, the characteristics of fuel supply system and its applicability were evaluated in a heavy duty natural gas engine. The results showed that the potential of fuel pressure regulator and fuel metering valve had enough capacity with HCNG. Employed mixer did not affect the distribution characteristics of mixture.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.79-84
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• 2004

For the non-premixed interacting jet flames, it has been reported that if eight small nozzles are arranged along the circle of 40 $^{\sim}$ 72 times the diameter of single jet, the flames are not extinguished over 2oom/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, ${\Phi}$, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying Sand ${\Phi}$ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with ${\Phi}$ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of fuel through the centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was different from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.

• Journal of the Korea Society of Computer and Information
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• v.25 no.9
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• pp.159-166
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• 2020

The purpose of this research is to suggest some practical and policy implications for improving adolescent's self-esteem through analyzing longitudinally the effects of parental attitude, peer relationship, student-teacher relationship, school learning activity, life-goal on adolescent's self-esteem by using latent growth curve model. Analytical data was obtained from the KYCPS. The analytical results showed that the change model of adolescent's self_esteem turned out to be a leaner model in which the change rate and intercept were significant. Second, time dependent variables influence on adolescent's self_ esteem meaningfully. Third, time dependent variables influence on adolescent's self_ esteem changes significantly. This study proposed some policy implications basing on these findings.

• Journal of The Korean Association of Information Education
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• v.24 no.1
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• pp.59-69
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• 2020

The purpose of this study is to design the framework of evaluation on learner's cognitive skill for artificial intelligence(AI) education through computational thinking. To design the rubric and framework for evaluating the change of leaner's intrinsic thinking, the evaluation process was consisted of a sequential stage with a) agency that cognitive learning assistance for data collection, b) abstraction that recognizes the pattern of data and performs the categorization process by decomposing the characteristics of collected data, and c) modeling that constructing algorithms based on refined data through abstraction. The evaluating framework was designed for not only the cognitive domain of learners' perceptions, learning, behaviors, and outcomes but also the areas of knowledge, competencies, and attitudes about the problem-solving process and results of learners to evaluate the changes of inherent cognitive learning about AI education. The results of the research are meaningful in that the evaluating framework for AI education was developed for the development of individualized evaluation tools according to the context of teaching and learning, and it could be used as a standard in various areas of AI education in the future.

• Education of Primary School Mathematics
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• v.17 no.3
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• pp.205-230
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• 2014

New teaching and learning theory on various aspects about class is needed to implement education which reflects constructivism, ideally. For an ideal learner-centered mathematics class, tangible and intangible elements related to education(view of knowledge, view of leaner, teacher's role, evaluation, the form of class, learning, teaching material, etc.) should be integrated from a constructive perspective and especially, teaching material has to be premised on that learners have intellectual abilities to construct knowledge themselves, and reflect integrity of knowledge, diversity and others, and contain open attributes. In addition to this, teaching material should have characteristics different from those when objective epistemology applies, so there is a need to analyze whether teaching material has those characteristics. For this, this study compared and analyzed <1. Three-Digit Numbers> which belongs to the domain of numbers and operations out of the units of mathematics(3) textbook of the 2009 revised curriculum for the first and second grade that first introduced story-telling, and <3. Understanding of Place Values> for the second grade of constructive math class used in the U.S.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.883-886
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• 2007

This study examined contents of interaction that played an important role in learners' accomplishment of educational goals at web-based educational system. The purpose of the study was to find out design strategies of web-based education website that could give learners more satisfactory interaction. The study firstly investigated concept and values of web-based education as well as interaction by literature study to analyze web-based educational design principles at actual web-based education websites from point of view of interaction and to examine what factors should be used and reinforced at existing teaching. The findings were as follow: Web-based education websites made use of interaction with 'each design factor', such as colors, texts and images, etc that were based on communication designs to give 'information' by systematic interaction more than by social interaction.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.3
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• pp.226-230
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• 2009

Intelligent Tutoring System (ITS) is a procedure of analyzing collected data for teaming, making a strategy and performing adequate service for learners. To perform suitable service for learners, modeling is the first step to collect data from the process of their learning. The model, however, cannot be authentic if collected data can contain learners' inconsistent behaviors or unpredictable learning inclination. This study focused on how to sort normal and abnormal data by analyzing collected data from learners through visualization. A model has been set up to assort unusual data from collected learner's data by using DOLLS-HI which makes possible to diagnose learner's learning propensity based on housing interior learning contents in the experiment. The created model has been confirmed its improved reliability comparing to previous one.

• Communications of Mathematical Education
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• v.22 no.1
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• pp.41-52
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• 2008

In this paper, some factors such as the perspective of children, instructional materials(especially activities in textbooks for elementary school mathematics), and teacher's questioning styles are discussed as ones influenced on students' immersion in leaner-centered instruction. This discussion is based on the author's two implementations of the kind of two instructions. About the first theme, constructivists assert that even children who are in elementary school can have reflective abstracting ability. Teachers' asking questions with the belief differ from ones with traditional perspective of children, which is relevant the third factor. They value and respect learners' thinking outcomes, even though they are not sometimes wrong and have errors. Also, they have them opportunities to think different from others and to ask how they get their answers. To do these, they frequently ask open-ended questions, not closed. All of them is possible through the activities provided in textbooks. Some characteristics which can prompt such teacher's questions using activities in elementary mathematics textbooks are discussed.

• Journal of Engineering Education Research
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• v.9 no.1
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• pp.43-60
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• 2006

This study was examining and analyzing the perception and significance for engineering teaching objectives and strategies designed for students. The optional sampled method with various levels was applied to all the junior students at college of engineering in Jeola North Province. The five applied universities were again divided into three divisions. The result of this study was as follows ; First, according to the analysis of students' conception about the significance degree of good education suitable for engineer and a number of a community, leaner's attitude and opinion learning were more important than any other instruction objectives. Second, according to the other analysis regarding to the significance degree of instruction objectives and methods, the teaching of technical operation was thought more important than any other instruction objectives. Overall, this study showed that the significance degree of instruction objectives and teaching strategies of engineering education had a little difference according to a various factor but they were arranged from three points (importance) and four points (very importance).

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.95-105
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• 2013

The music education improves the creative talent, social skills and academic achievement of the students. For the efficient music education, it is requested to develop the collaborative educational learning tools, especially electronic collaborators suitable to the leaner's study patterns and speed. In this paper, we propose a new method to develop a PC-based self learning software for the flute performance using templates and descriptors to make the contents form and substance. Our proposed method can allow user to modify the descriptors to match the contents to his level. We implemented a PC-based self learning software for the flute performance compactly and a feasibility test showed the efficiency of our proposed method to construct a self learning tool to play the flute and the tool can be utilized for the beginner to learn playing flute.