• Journal of Korean Elementary Science Education
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• v.33 no.4
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• pp.736-750
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• 2014

The purposes of this study were to investigate concepts of Korean and American elementary school pre-service teachers on combustion, and to compare the concepts of Korean pre-service teachers with those of American pre-service teachers. For this study, concept test on combustion was administered to 23 Korean and 18 American elementary school pre-service teachers. The test composed of 6 items: 'Definition of combustion', 'The reason why a candle in a glass bottle is blown out when the bottle was closed', 'The change of gases in the bottle when a candle burns in it', 'The combustion products of a candle', 'The combustion products of steel wool', and 'The combustion products of a substance'. The results showed that the rates of elementary school pre-service teachers who had scientific concepts on combustion were very low in both Korean and American pre-service teachers' groups, although they were a little different from items. However the rates of pre-service teachers who had partial concepts and misconceptions on combustion were high in two groups. The levels of Korean elementary school pre-service teachers' concepts were a little higher than those of American elementary school pre-service teachers' concepts. The contents and activities on combustion which are in Korean and American science textbooks seem to affect building up their concepts on combustion.

• Journal of the Korean Chemical Society
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• v.59 no.4
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• pp.296-307
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• 2015

The purposes of this study were to develop the experiment for gas concentration measure during combustion of a candle and to investigate the application effect of the experiment. For this study, 15 elementary school teachers were selected by considering their gender, career, 6th grade science teaching experience, and 6th grade science teaching experience according to 2007 revised s cience curriculum. The experiment using MBL is designed to confirm gas concentrations visually during the combustion of a candle which burns in an acrylic container. The experiment method is as follows. 1) Make two sets of holes in the container and then insert oxygen sensors and carbon dioxide sensors in the holes. 2) Burn a candle in the container and observe the changes in the burning of the candle. The experiment has checked oxygen concentration and carbon dioxide concentration in real-time and displays gas concentration changes by graphs. The results of the application effect of the experiment are as follows. Most elementary school teachers who had not had scientific concepts on combustion got acquainted with scientific concepts about ‘the reason why a candle is blown out when it is covered with a bottle’, and ‘the concentrations of oxygen and carbon dioxide before and after combustion’. In addition, about half of elementary school teachers got acquainted with scientific concepts about ‘the definition of combustion’, and ‘distribution of carbon dioxide during combustion’. Thus, the experiment to measure gas concentrations during combustion is helpful to improve elementary school teachers’ concepts on combustion.

• Journal of Korean Elementary Science Education
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• v.19 no.2
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• pp.75-82
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• 2000

The purpose of this study was to investigate the effectiveness of teaching strategies for scientific conceptions in the units of oxygen and combustion in elementary school science textbook. 70 elementary school 6th grade students in Seoul participated. They were divided into experimental group and controlled group. Five scientific concepts were adopted from the units of oxygen and combustion in the 6th grade science textbook. Subjects' preconceptions were investigated by pre-questionnaires. A series of 6 instructional sessions based on the teaching strategy of cognitive confliction theory were given to the experimental group. By the end of the instructional session, a post-test was administered to both experimental and controlled groups. There was a statistically significant difference between post-test gains of the experimental and controlled groups. These results support the notion that the teaching strategy was effective for changing from preconceptions to scientific concerts.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.301-302
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• 2012

During a last decade, detonative combustion is promising combustion mechanism of high-speed propulsion systems, but is more rigorously considered in these days as a game-changer for the improvement of thermodynamic efficiency of propulsion and power generation systems. Regardless of the skepticism about the pressure loss associated with the strong shock waves, it is shown that the additional compression by the strong shock wave exhibits increased thermodynamics efficiency that is not achievable by conventional compression systems. Present talk will give an introduction to the concepts and the recent activities on the pressure gain combustors (PGC) researches based on detonation phenomena.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.941-952
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• 2012

In the present contribution the Encounter Theory (ET) (the prototype of the classical Collision Theory in rarefied gases) concepts for widely occurring diffusion assisted irreversible bulk reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in liquid solutions examined by the authors in the literature are analyzed and compared with each other for these different types of reactions. It is shown that for a particular case of equal initial concentrations $[A]_0=[B]_0$ in the reaction A + B ${\rightarrow}$ C, when the kinetics of both reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in the framework of formal chemical kinetics and ET are the same, the accumulation of macroscopic correlations breaking the concepts of independent encounters and leading to the Generalized Encounter Theory (GET) are drastically different. The influence of the force interaction and the decay of nonstable reactants on the time behavior the macroscopic correlations is also briefly discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• Journal of ILASS-Korea
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• v.10 no.2
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• pp.41-47
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And. it is extremely difficult to increase gasoline engine efficiency and to reduce NOx and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper. internal EGR(exhaust gas recirculation) effect is suggested to realize CAI combustion. An experimental study was carried out to achieve CAI combustion using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). A flame trap was used to simulate internal EGR effect and to increase flame propagation speed in the CVCC. Flame propagation photos and pressure signals were acquired to verify internal EGR effect. Flame trap creates high speed burned gas jet. It achieves higher flame propagation speed due to the effect of geometry and burned gas jet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1756-1762
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• 2002

To effectively meet current regulations on the exhaust emissions of diesel engine required to control the deterioration of air pollution in the whole world, this study is to investigate the effects of water induction through the air intake system on the characteristics of combustion and exhaust emissions in IDI diesel engine. A method fur supplying water through the air intake system to reduce the exhaust emissions has been considered with other methods such as water introduction in the form of water-in-fuel emulsion or water injection directly into the combustion chamber, but it has not been studied about the effects of water on the combustion concepts and the characteristics of exhaust emissions in detail until now. In this study, the formation of NOx was significantly suppressed by decreasing the gas peak temperature during the initial combustion process because the water play a role as a heat sink during evaporating in the combustion chamber, but the smoke was slightly increased by increasing water amount.

• Journal of ILASS-Korea
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• v.16 no.1
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• pp.51-57
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• 2011

An experimental study was performed to explore characteristics of combustion and exhaust emissions in the compression ignition engine of RCCI (reactivity controlled compression ignition) using diesel-gasoline dual fuel. A dual-fuel reactivity controlled compression ignition concepts is demonstrated as a promising method to achieve high thermal efficiency and low emissions. For investigating combustion characteristics, engine experiments were performed in a light-duty diesel engine over a range of SOIs (start of injection) and gasoline percents. The experimental results showed that cases of diesel-gasoline dual fuel combustion is capable of operating over a middle range of engine loads with lower levels of NOx and soot, acceptable pressure rise rate, low ISFC (indicated specific fuel consumption), and high indicated thermal efficiency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.400-401
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• 2009

Present paper introduces the concepts and R&D activities on the hypersonic vehicles, X-51A by USAF using Dual-Mode Ramjet (DMR) and HyFly by US Navy using Dual-Combustion Ramjet (DCR) both sponsored by DARPA.