• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.158-169
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• 2006

The present article is concerned with the overview of the chemically/surface modified cubic spinel $LiMn_2O_4$ as a cathode electrode far lithium ion secondary batteries. Firstly, this article presented a comprehensive survey of the cubic spinel structure and its correlated electrochemical behaviour of $LiMn_2O_4$. Subsequently, the various kinds of the chemically/surface modified $LiMn_2O_4$ and their electrochemical characteristics were discussed in detail. Finally, this article reviewed our recent research works published on the mechanism of lithium transport through the chemically/surface modified $Li_{1-\delta}Mn_2O_4$ electrode from the kinetic view point by the analyses of the experimental potentiostatic current transients and ac-impedance spectra.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• Journal for History of Mathematics
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• v.29 no.2
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• pp.73-88
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• 2016

To introduce materials related to our traditional mathematics and to reinterpret modernly them could be a good tool to find the cultural values of them. We analyzed the degree for utilization of the history of mathematics in the middle school textbooks developed depending on the 2009 revised mathematics curriculum. Through this, we suggest the need for research on concrete and practical teaching and learning materials development utilizing the history of mathematics. We reinterpret, in modern style based on the curriculum, two subjects dealt with in 'GakDeungByeonHyeongSeupYu', the first theme of 'SanSulGwanGyeon' written by Lee Sang Hyuk. We expansively reconstruct the original samples up to regular decagon so that students might figure out the situation of all regular polygon using a kind of mathematics software GeoGebra. Also this process is constructed on the basis of the curriculum for an implementation the secondary school classes.

• Journal of Korea Foundry Society
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• v.11 no.5
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• pp.398-405
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• 1991

Al-Li alloy has a high strength with low density. Practically this alloy should use by the material which made from the rapid solidification. Therefore we examine the solidification structures of alloy with cooling rate. According to cooling rate increased, grain size and secondary dendrite arm spacing were smaller. Also grain size was further smaller by Zr added. To obtain more fine solidification structure, rapid solidification by single roll melt spinning was performed. According to higher wheel speed, cooling rate increased and cell size was smaller. Because of locally different cooling rate, different cell size was obtained in same specimen. More than cooling rate $10^6^{\circ}C$ /sec, zone A(insensible zone to corrosion)was obtained.

• Journal of The Korean Association For Science Education
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• v.20 no.4
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• pp.510-518
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• 2000

The purpose of this study was to develop learning materials for the discussion and examine the effects of the discussion learning over the students' conceptual change on force and motion. The subjects consisted of 360 middle school students, comprising of 5 discussion groups of 185 students and 5 traditional learning groups of 175 students. The results indicated that students in the discussion groups showed higher achievement than those in the traditional learning groups. Therefore this study supported the importance of discussion in conceptual change. However further research should be conducted to examine other educational effects of discussion.

• Journal of The Korean Association For Science Education
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• v.14 no.1
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• pp.12-23
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• 1994

This study was conducted to investigate the status and the problem of environmental education in schools. For this investigation, sub-goals to the general goal for environmental education such as knowledge, awareness, attitude, skill, participation, and evaluation were classified. The contents and objects of the environment-related chapters in elementary and secondary school science texts and of the materials for environmental education were analyzed. Resultingly, the content and objects focused on the cognitive domain such as knowledge and skill category in science texts($85{\sim}92\;%$) and in the materials for environmental education($70{\sim}84\;%$). The result indicated that the objects of the cognitive domain were heavily emphasized in the present environmental education.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.373-377
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• 1996

Carbon materials have become a major interestings of research directed toward the development for anode of lithium batteries of enhanced cell capacity. The purpose of this study is to research and develop poly(p-phenylene)(PPP)-based carbon as a anode of lithium secondary batteries. We have synthesized PPP from benzen by chemical reaction. And then disordered carbon materials were obtained by heat-treating PPP in a nitrogen atmosphere at 40$0^{\circ}C$ to 100$0^{\circ}C$ for 1 hour. The carbon prepared by heat treatment showed a broad x-ray diffraction peak around 2$\theta$=23$^{\circ}$. Electrodes were charged and discharged at a current density of 0.1㎃/$\textrm{cm}^2$. Excellent reversible capacity of 275㎃h/g and 97% of charge/discharge efficiency were observed heat treated PPP-based carbon a $700^{\circ}C$.

• Proceedings of the Korean Environmental Health Society Conference
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• 2004.06a
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• pp.165-168
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• 2004

An anti-fungal material producing actinomycete was isolated from domestic soil. This strain was identified as Streptomyces albogriseus by 16S rDNA sequence. YEME (yeast extract 4g, malt extract 10g, glucose 4g, D.W 1l , pH $7.0{\pm}0.2$) medium was used for production of anti-fungal materials. S. albogriseus was cultured in a shaking incubator for 2 weeks at 150 rpm and $25{\pm}1^{\circ}C$. An anti-fungal material produced by S. albogriseus was identified at 340nm by uv/vis- spectrometer and it showed powerful anti-fungal activity. This is the first report that secondary metabolite produced by S. albogriseus showed an activity against phytopathogenic fungi such as Collectrichum coccodes, Botrytis cinerea, Cladosporium cucumerinum, Didymella bryoniae.

• Hwankyungkyoyuk
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• v.15 no.2
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• pp.14-29
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• 2002

The environment of the world becomes deteriorated rapidly as the result of the development of technology, the increase of the standard of living, and the growth of population. These circumstances called for environmental education in Korea, creating an environment course in the middle and high school in 1995. Despite the increasing importance of environmental education, however, the situation has not developed in its favor because of the current system of the university entrance examination. The school has failed to develop the curriculum of environmental education in the secondary education. This paper solves this problem internally in terms of the improvement of the contents, organization, teaching method (role-playing game), and teaching materials of environmental education, with a case study of the “noise” unit in 10th grade. This case study expects to change the attitude toward noise, increase the interest and knowledge in environment, and lead to responsible environmental behavior.

• Interaction and multiscale mechanics
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• v.1 no.3
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• pp.317-328
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• 2008

When carbon-filled rubber specimens are subjected to cyclic loading, they do not return to their initial state after loading and subsequent unloading, but exhibit a residual strain or permanent deformation. We propose a specific form of the pseudo-elastic energy function to represent cyclic loading for incompressible, isotropic materials with stress softening and residual strain. The essence of the pseudo-elasticity theory is that material behaviour in the primary loading path is described by a common elastic strain energy function, and in unloading, reloading or secondary unloading paths by a different strain energy function. The switch between strain energy functions is controlled by the incorporation of a damage variable into the strain energy function. An extra term is added to describe the permanent deformation. The finite element implementation of the proposed model is presented in this paper. All parameters in the proposed model and elastic law can be easily estimated based on experimental data. The numerical analyses show that the results are in good agreement with experimental data.