• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.83-90
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• 2004

A flywheel-driven rapid compression and expansion machine is developed and utilized for experimental study of homogeneous charge compression ignition combustion. Compression ignition of homogeneous charge in IC engines offers possibilities of realizing ultra-lean engine operation with greatly reduced NOx and particulate formation. Fundamental investigations are carried out in order to better understand this ideal engine combustion mechanism. Perfectly premixed propane-air mixtures of various equivalence ratio are compression-ignited in the rapid compression and expansion machine, and the characteristics of the auto-ignition and the following combustion process are analyzed.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.86-96
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• 2007

A direct-injection stratified-charge(DISC) engine has been considered as a promising alternative in spite of high unburned hydrocarbon emission levels during light load operation. In this paper investigation is made to characterize formation and combustion processes of stratified mixture charge in a simple constant volume combustion chamber. Both experimental and numerical analyses are performed for fluid and combustion characteristics with 3 different induction types for rich, homogeneous and lean mixture conditions. The commercial code FIRE is applied to the turbulent combustion process in terms of measured and calculated pressure traces and calculated distributions of mean temperature, OH radical and reaction rate. It turns out that the highest combustion rate occurs for the rich state condition at the spark ignition location due to existence of stoichiometric mixture and timing.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.98-103
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• 2007

The number of vehicles employing diesel engines is rapidly rising. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced exhaust regulations. The Diesel Particulate Filter (DPF) system is considered as the most efficient method to reduce particulate matter (PM), but the improvement of a regeneration performance at any engine operation point presents a considerable challenge by itself. Temperature, gas compostion and flow rate of exhaust gas are important parameters in DPF evaluation, especially regeneration process. Engine dynamometer and degment tester are generally used in DPF evaluation so far. But these test method couldn't reveal the effect of various parameters on real DPF, such as O2 concentration, amount of soot and exhaust gas temperature. This research has studied the possibility using dump combustor that used to take an approach lean premixed combustion in gas turbine for a DPF power and optimized. It is possible that utilize the system as DOC (Diesel Oxidation Catalyst) and SCR(Selective Catalytic Reduction) assessments test as well as DPF evaluation

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.288-298
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• 1999

In spark ignited engines, the electrical spark not only sets the time for the onset of combustion but also is able to greatly influence the character of the initial flame growth and the subsequent combustion, and thereby can influence engine performance. The relative importance of the ignition energy is particularly high under lean or high residual gas or exhaust gas recirculation (EGR). In this study, a modeling of flame Initiation and its development is proposed. Submodels consist in representing of cylinder pressure and temperature, heat transfer to cylinder wall, and flame kernel heat transfer to ambient air and to spark plug electrodes. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy, and laminar and turbulent flame velocity.

• Fashion & Textile Research Journal
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• v.10 no.5
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• pp.713-720
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• 2008

The purpose of this study was to propose the method reproducing three dimensional figure data to a reconstructed body by the styrofoam board. To make the reconstructed body, the 3D figure data were rotated to make symmetry and the surfaces were edited. The horizontal curves were gathered equally-spaced based on the waist horizontal plane. we proposed the process to cut the styrofoam board according to the horizontal curves, to assemble them to organize the shape of the body figure and to coat the surface with the knitted. The 3-dimensional figure data of straight type, swayback type, lean-back type and bend-forward type were selected and the reconstructed bodies were made as above. And the compatibility was verified by the measurement comparison and deviations between 3-dimensional figure data and reconstructed body.

• Journal of Korean Society for Quality Management
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• v.39 no.4
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• pp.500-506
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• 2011

Evolutionary operation (EVOP) proposed by Box(1957) is a method for continuous monitoring and improvement of a full-scale manufacturing process with the objective of moving the current operating conditions toward the better ones. EVOP in experiments with mixtures consists of screening vital few components and making small changes in the current operating condition by making small increments in the proportion of the screened component. In this paper, how to determine operating conditions in EVOP in experiments with mixtures around the current operating condition is proposed. The proposed methods are illustrated with the simulated data based on the well known flare experimental data described by McLean and Anderson(1966).

• Journal of Korean Elementary Science Education
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• v.19 no.1
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• pp.85-99
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• 2000

Researches have shown that learning science frequently requires the process of conceptual change. As a result, many of the constructivist teaching and loaming approaches focus on this kind of loaming. In approaches that focus on conceptual change, cognitive conflict strategies play a key role. Students, however, still have much difficulty in loaming science. Theoretically, it underlies Piaget's genetic epistemology in which disequilibration demands an interplay between assimilation and accommodation until equilibrium is restored. Also, radical constructivism has its roots in a variety of disciplines, but has been most profoundly influenced by the theories of lean Piaget as interpreted and extended by Glasersfeld. This study is intended to interpret the conceptual change from radical constructivist perspective and explain difficulties of conceptual change which students have in learning science.

• Asia pacific journal of information systems
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• v.15 no.1
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• pp.1-24
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• 2005

The purpose of this study is to identify the factors affecting the performance of knowledge management systems. To extend DeLone & MeLean's model, we included the user specialization in the information systems success model. The questionnaires are collected from 109 knowledge management system users. The major findings are summarized as followed. First, system characteristics such as ease of use, response time, and knowledge management process support affect the knowledge management systems usage. Second, knowledge characteristics such as relevancy, completeness, reliability, importance, and currency also affect the knowledge management systems usage. Third, the end-users are satisfied with the knowledge management systems because it is easy to use and relevant.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.156-167
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• 1996

The present work is a continuation of our previous study to investigate the effects of parameters such as equivalence ratio, hydrogen supplement rate and initial pressure on combustion characteristics in a disk-shaped constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The flames in near stoichiometric mixture of methane-air are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed to an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate. Also, flame is sluggishly propagated at increased initial pressure in combustion chamber. Volume fraction of burned gas and flame radius as the combustion characteristics are increased by increasing the hydrogen supplement rate, especially at the combustion middle period, but then are slowly increased by increasing the initial pressure.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.90-90
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• 2013

Since discovery, NdFeB permanent magnet has replaced application of the conventional magnets rapidly because of its superior physical and mechanical properties. With increasing consumption of power combined with energy resource depletion, energy efficiency is becoming more and more inportant. According to recent reports, almost almost half of the electric power is consumed by motor, and NdFeB magnets which are the core component of the motor play a key role on improving energy efficiency of the devices. In parallel with finding alternatives energy resources, research works improving energy efficiecy have been conducted world wide. Althogh NdFeB magnets usage have been expanded to various applications, key materials such as Nd and Dy, resouces lean heavily on specific area, China. Magnetic industry revently experienced skyrocketing price fluctuatioin of rare earth at around 2008. Chineses government's regulations worsened the situation and arose a necessity to develop methods to minimize rare earth use. In this presentation, POSCO's recent research works on rare earth reduction is presented including novel powder alloying method using nitrate precursors. Also, future R&D plans for rare earth free magnets is briefly introduced as well.