• 한국지구과학회지
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• 제27권4호
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• pp.374-389
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• 2006

이 연구는 예비 중등 교사들을 대상으로 Lakatos의 방법론에 따라서 "계절 변화의 설명"에 대한 대안 모형을 조사하였다. 조사대상은 사범대학 과학교육학부 74명이다. 조사 결과 계절 변화에 대한 예비 중등 교사들의 설명은 과학적 모형과 불일치하는 대안 모형들을 가지고 있었다. 이러한 명백한 불일치의 대안 개념은 어떤 일관성 있는 방향으로, 자신들이 가지고 있는 대안 모형의 핵심 신념을 사용한다고 가정함으로서 설명되어 진다고 우리는 주장한다. 따라서 이 연구에서는 예비 교사들의 대안 모형을 극복하기 위해서 먼저 그들이 가지고 있다고 가정할 수 있는 핵심 신념들과 가능한 근원들을 알아보는 것이다. 그러한 근원들 중에서 교과서가 예비 교사의 대안 모형의 근원을 제공할 가능성을 배제할 수는 없다.

• 한국대기환경학회지
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• 제24권4호
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• pp.439-454
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• 2008

The purpose of this study was to extensively identify $PM_{10}$ sources and to estimate their contributions to the study area, based on the analysis of the $PM_{10}$ mass concentration and the associated inorganic elements, ions, and total carbon. The contribution of $PM_{10}$ sources was estimated by applying a receptor method because identifying air emission sources were effective way to control the ambient air quality. $PM_{10}$ particles were collected from May to November 2007 in the Yongin-Suwon bordering area. $PM_{10}$ samples were collected on quartz filters by a $PM_{10}$ high-volume air sampler. The inorganic elements (Al, Mn, V, Cr, Fe, Ni, Cu, Zn, Cd, Pb, Si, Ba, Ti and Ag) were analyzed by an ICP-AES after proper pre-treatments of each sample. The ionic components of these $PM_{10}$ samples ($Cl^_$, $NO_3^-$, $SO_4^{2-}$, $Na^+$, $NH_4^+$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$) were analyzed by an IC. The carbon components (OC1, OC2, OC3, OC4, OP, EC1, EC2 and EC3) were also analyzed by DRI/OGC analyzer. Source apportionment of $PM_{10}$ was performed using a positive matrix factorization (PMF) model. After performing PMF modeling, a total of 8 sources were identified and their contribution were estimated. Contributions from each emission source were as follows: 13.8% from oil combustion and industrial related source, 25.4% from soil source, 22.1% from secondary sulfate, 12.3% from secondary nitrate, 17.7% from auto emission including diesel (12.1%) and gasoline (5.6%), 3.1% from waste incineration and 5.6% from Na-rich source. This study provides information on the major sources affecting air quality in the receptor site, and therefore it will help us maintain and manage the ambient air quality in the Yongin-Suwon bordering area by establishing reliable control strategies for the related sources.

• 전기화학회지
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• 제11권3호
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• pp.211-222
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• 2008

휴대용 전자기기의 전원으로 채용되어 상업적으로도 성공을 거두고 있는 리튬이차전지는 HEV(Hybrid Electric Vehicle)와 같은 비IT용 전원으로서도 중요성을 더하고 있다. 리튬이차전지는 리튬금속을 사용함에 따라서 초래되는 안전성을 문제를 탄소계음극을 채용하고 이에 따른 안전기구를 확보함에 의해 상용화 되었다고 할 수 있다. 이와 같이 전지에 있어 전극소재의 개발은 핵심기술이라 할 수 있으며, 점차 그 응용처가 확대되어 가고 있는 리튬이차전지의 전극소재 개발은 전지 산업뿐만 아니라 타 산업에 미치는 영향은 크다고 할 수 있다. 여기서는 리튬이차전지가 상용화되어 온 이후 채용되어온 음극과 개발중인 음극 후보에 대해 그 장단점을 분석해 보고자 한다.

• 한국미생물·생명공학회지
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• 제16권5호
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• pp.427-431
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• 1988

Pseudomonas testosteroni 6F1의 아닐린 분해에 미치는 이차기질의 첨가효과를 보기 위하여 균생장에 필요한 유도기간과 효소활성유도 정도를 조사하였다. 아닐린만 존재하는 배지에서 P. testosteroni 6Fl은 7시간의 유도기간을 필요로 한데 비하여 쉽게 이용가능한 이차기질을 첨가해준 경우 아닐린 분해에 필요한 유도기간이 1-3시간으로 줄어들었다. 이러한 아닐린 분해 촉진효과는 이차기질과 아닐린이 서로 발리 이용되면서 균체의 생장과 분해효소의 활성유도시기를 앞당겼기 때문이었으며, 이때 아닐린 분해효소의 최종활성 정도는 첨가해준 이차기질에 따라 다르게 나타났다.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.457-463
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• 2012

Cascaded H-bridge multilevel inverters shows a useful circuit configuration to increase the number of output voltage levels to obtain high quality output voltage. By applying the concept of the power of three to dc voltage sources, it can increase the number of output voltage levels effectively. To realize this concept, two approaches may be considered. One is to use independent dc voltage sources pre-scaled in the power of three, and the other is to use instantaneous dc voltage sources generated from a cascaded transformer, which has the secondary turn-ratios scaled in the power of three in sequence. A common feature in both approaches is to use the concept of the power of three for dc voltage sources, and a point of difference is whether it adopts a low frequency transformer or not, and where the transformer is located. According to the difference, application areas are limited and show different characteristics on THD of output voltages. We compare and analyze both approaches for their circuit configurations, voltage level generating method, THD characteristics of output voltage, efficiency, application areas, limitations, and other characteristics by experiments using 500 [W] prototypes when they generate a 27-level output voltage.

• 한국대기환경학회지
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• 제18권4호
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• pp.275-284
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• 2002

Atmospheric concentrations of organochlorine pesticides (OCPs) in Seoul, South Korea between July 1999 and May 2000 were determined to investigate concentration distribution in air, relationship between concentrations and meteorological conditions, and apportionment of sources e.g. local sources (air- surface exchange) and long range transport. Endosulfan and $\alpha$-HCH were the highest concentrations in atmosphere with values typcally ranging from 10s to l00s of pg/㎥. These high concentrations may be attributed to their usage, period and chemical property (Koa). All OCPs also showed elevated levels during the summer and were positively correlated with temperature. This would suggest that a seasonal enhancement was due to (re)volatilization from secondary sources and application during the warmer months. The temperature dependence of atmospheric concentrations of OCPs were investigated using plots of the natural logarithm of partial pressure (In P) vs reciprocal mean temperatures (1/T), and environmental phase-transition energies were calculated for each of the pesticides. For OCPs, temperature dependence was statistically significant (at the 99.99% confidence level) and temperature accounted for 35~95% of the variability in concentrations. The relatively higher slopes and phase-transition energies for $\alpha$-, ${\gamma}$-chlordane, endosulfan and endosulfan sulfate suggested that volatilization from local sources influenced their concentrations. The relatively lower those for $\alpha$-, ${\gamma}$-HCH, p, p'-DDE and heptachlor epoxide also suggested that volatilization from local sources and long range transport influenced their concentrations.

• 한국과학교육학회지
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• 제21권5호
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• pp.773-794
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• 2001

Many studies on the professional development of science teachers demonstrated that induction teachers' conceptions of teaching science are important factors in developing their professionalism. The present study was conducted to describe in detail the progress of two science induction teachers, June and Mike, towards conceptual change teaching, and to investigate secondary induction science teachers' conceptions of teaching science by analysing their conceptual ecologies. The study was interpretive, using multiple data sources to achieve a triangulation of data. Both June and Mike held strongly positive learning in their views of knowledge and science. Holding positivist views of knowledge and of science is likely to be a major obstacle for anyone coming to understand constructivism and its implications in teaching for conceptual change. This argument resonates in several key ways with the teachers' cases, even though I recognize differences between scenario and teachers, and between teachers themselves.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.42-45
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• 1997

Weldline movement of tailored blanks originates from two sources, primary and secondary. Primary movement occurs by geometrical reason, that is, just scratched lines on the no-weld blanks move during drawing to be fitted to geometrical change. Secondary movement is induced by the characteristics of tailored blanks itself. The primary movement was mainly dependent on the weldline location and not affected by the type of material. The secondary movement caused by laser welding and/or small strength difference in this study was not dominant compared with primary movement. The formability of tailored blanks always inferior to those of original blanks. This is due to the existence of hardened weld bead. The closer a weldline is to punch corner where drawing is most active, the worse its formability becomes. This is because the weldline prohibits the drawing process. It was confirmed by measuring diagonal length at the blank corner. The mode of fracture was changed form wall break to draw break when the weldling was close to the punch corner.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 춘계학술대회
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• pp.34-34
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• 2019

About 60% of the present drugs were developed from natural products with unique chemical diversity and biological activities. Hence, discovery of new bioactive compounds from natural products is still important for the drug development. On the other hand, breakthrough made in synthetic biology has also begun to supply us with many useful compounds through manipulation of biosynthetic gene for secondary metabolites. Theoretically, this approach can also be exploited to generate new unnatural compounds by intermixing genes from different biosynthetic pathway. Considering the potential, we are studying about bioactive compounds in natural sources, as well as the biosynthesis of natural products including engineering of the secondary metabolite enzymes to make new compounds in order to construct the methodological basis of the synthetic biology. In this symposium, engineering of secondary metabolite enzymes that are involved in the biosynthesis of plant polyketides to generate new compounds in our laboratory will be mainly introduced.

• Journal of Microbiology and Biotechnology
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• 제32권5호
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• pp.541-550
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• 2022

Filamentous marine fungi have proven to be a plentiful source of new natural products. Chaetomium, a widely distributed fungal genus in the marine environment, has gained much interest within the scientific community. In the last 20 years, many potential secondary metabolites have been detected from marine-derived Chaetomium. In this review, we attempt to provide a comprehensive summary of the natural products produced by marine-derived Chaetomium species. A total of 122 secondary metabolites that were described from 2001 to 2021 are covered. The structural diversity of the compounds, along with details of the sources and relevant biological properties are also provided, while the relationships between structures and their bioactivities are discussed. It is our expectation that this review will be of benefit to drug development and innovation.