• Journal of Applied Biological Chemistry
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• 제48권3호
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• pp.133-137
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• 2005

In vitro antimutagenicity of Bacillus natto islolated from Natto, Japanese traditional fermented food, was investigated using umu-test. Mutagenicity of S9-activated metabolites of Trp-P-2 and IQ for Salmonella typhimurium TA 1535/pSK1002 was remarkably inhibited by addition of bacterial cells and their cytoplasmic fraction. Desmutagenicity by cytoplasmic fraction increased with increasing concentration of the fraction. Bioantimutagenic effect of cytoplasm on Salmonella typhimurium SD-100 did not show bioantimutagenic activity against mutated bacterial cells induced by Trp-P-2. Cytoplasmic fraction exhibited 17% bioantimutagenicity due to desmutation caused by IQ.

• East Asian mathematical journal
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• 제34권2호
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• pp.203-217
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• 2018

This study examined preservice elementary teachers' patterns and tendencies in thinking of drawn models of multiplication with fractions. In particular, it investigated preservice elementary teachers' work in a context where they were asked to select among drawn models for symbolic expressions illustrating multiplication with non-whole number fractions including a mixed number. Preservice teachers' interpretations of fraction multiplication used in interpreting different types of drawn models were analysed-both quantitatively and qualitatively. Findings and implications are discussed and further research is suggested.

• Korean Chemical Engineering Research
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• 제51권5호
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• pp.622-627
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• 2013

콜로이달 실리카는 실리콘과 사파이어 웨이퍼의 정밀연마슬러리, 유-무기 하이브리드 코팅제, 정밀주조의 바인더 등 다양한 제품으로 사용되는 물질이다. 이러한 실리카 졸의 입자크기 및 분산 안정성은 웨이퍼의 표면, 코팅 막 혹은 벌크의 기계적, 화학적, 광학적 특성에 영향을 주기 때문에 정확한 측정값이 요구된다. 본 연구에서는 제조사에서 제시한 입자 크기 및 표면 특성이 다른 8종류 실리카 졸의 부피 분율에 따라 입자 크기, 졸 점도 및 입자 전기영동이동도의 측정결과에 미치는 영향을 논의하였다. 높은 표면활성을 지닌 실리카 입자의 특성 및 실리카 졸의 희석에 의한 안정화 이온 농도의 변화로 인해 실리카의 측정 입자 크기와 이동도는 졸의 부피 분율 혹은 입자 크기에 따라 변한다. 60 nm 보다 작은 입자는 부피 분율이 증가함에 따라 측정된 입자 크기가 증가한 반면에, 그 보다 큰 입자에서는 측정된 입자 크기가 감소하였다. 12 nm와 같이 작은 입자는 부피 분율이 증가함에 따라 점도가 상승하면서 측정 입자의 이동도가 감소한 반면에 100 nm의 큰 입자는 0.048의 낮은 부피 분율까지 이동도가 증가하다가 그보다 높은 부피 분율부터 감소하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제52권2호
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• pp.217-230
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• 2013

This study attempts to propose the construction of textbook contents of fraction division and to suggest a method to strengthen the connection among problem context, manipulation activities and symbols by proposing an algorithm of dividing fractions based on problem contexts. As showing the suitable algorithm to problem context, it is able to understand meaningfully that the algorithm of fractions division is that of multiplication of a reciprocal. It also shows how to deal with remainder in the division of fractions. The results of this study are expected to make a meaningful contribution to textbook development for primary students.

• 한국식품과학회지
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• 제46권4호
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• pp.483-488
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• 2014

브로콜리(Brassica oleracea var. italica) 잎의 n-hexane, chloroform, ethyl acetate, butanol 및 distilled water 분획물의 total phenolic 화합물 함량은 chloroform 분획물이 206.8 mg GAE/g으로 가장 높게 나타났으며, ABTS radical 소거활성 및 지질 과산화(MDA) 생성 억제효과 실험 결과에서 chloroform 분획물에서 가장 높은 활성을 나타내었다. in vitro 항산화 실험들에서 우수한 효과를 보인 chloroform 분획물을 이용하여 $H_2O_2$으로 유도한 산화적 스트레스에 대한 신경세포(PC12 cell)에서의 산화적 스트레스 생성 억제효과, 세포 생존율 그리고 세포막 손상 억제효과 역시 농도 의존적 경향을 나타내며 positive control 로 사용된 Vit.C와 유의적인 결과를 나타냈다. 마지막으로, HPLC 분석 결과 브로콜리 잎 chloroform 분획물에 존재하는 주요 phenolic 화합물은 feulic acid인 것으로 확인되었다. 본 연구 결과를 종합해볼 때, 생리활성 물질로서의 ferulic acid 등을 함유한 브로콜리 잎 chloroform 분획물은 in vitro 항산화 활성과 함께 신경세포 보호효과를 나타내는 고부가가치 기능성 소재로의 활용이 기대된다.

• 대한수학교육학회지:학교수학
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• 제14권1호
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• pp.45-64
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• 2012

본 정성 연구에서는 교사들의 등분제 분수 나눗셈에 대한 지식을 분석하였다. 자료 수집은 13명의 교사들이 참여한 분수, 소수, 비례 등에 대한 주제를 다룬 40시간의 교사교육 프로그램으로부터 수집되어 일부분이 활용되었으며, 교사들의 등분제 분수 나눗셈 지식을 세밀하게 분석하기 위해 두 가지 지식 요소들 (단위에 대한 지식, 분할 조작)을 분석틀로 사용하였다. 그 결과, 제수와 피제수가 서로소인 등분제 나눗셈 문제 상황을 다루는 능력이 두 지식 요소의 사용여부와 수준에 따라 다르게 나타났다. 두 단계의 단위 구조만을 가지고 추론한 교사의 경우 한 사람의 몫을 주어진 단위로 정확하게 나타낼 수 없었다는 점에서 제한점을 보였으며, 세 단계의 단위 구조를 가지고 추론한 교사는 다양한 분할 조작과 참조 단위의 활용으로 보다 유연하게 문제 상황에 대처할 수 있음을 보여주었다.

• Preventive Nutrition and Food Science
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• 제4권2호
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• pp.145-151
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• 1999

Apolipoprotein B-100 (apo B-100) is an important component in plasma low density lipoproteins (LDL). It function as the ligand for the LDL receptor in peripheral cells. The LDLs are removed from the circulation by both high-affinity receptor-mediated and receptor-independant pathways. LDLs are heterogeneous in their lipid content, size and density and certain LDL subspecies increase risk of atherosclerosis due to differences in the conformation of apo B in the particle. In the present study , surface and core peptide fraction of Apo B-100 have been characterized by comparing peptide-mapping and fluorescence spectroscopy. Surface fragments of apo B-100 were generated by digestion of LDL with either trypsin , pronase, or pancreatin elastase. Surface fractions were fractionated on a Sephadex G-50 column. The remaining core fragments were delipidated and redigested with the above enzymes, and the resulting core peptides were compared with surface peptides. Results from peptide-mapping by HPLC showed pronase-digestion was more extensive than trypsin -digestion to remove surface peptide fraction from LDL. Fluorescence spectra showed that core fractions contained higher amount of tryptophan than surface fractions, and it indicated that core fraction wa smore hydrophobic than surface fractions. A comparison of the behavior of the core and surface provided informations about the regions of apo B-100 involved in LDL metabolism and also about the structural features concerning the formation of atherosclerosis.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.459-465
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• 2017

The goal of this study is to evaluate the effective thermal conductivity and diffusivity of containment walls as heat sinks or passive cooling systems during nuclear power plant (NPP) accidents. Containment walls consist of steel reinforced concrete, steel liners, and tendons, and provide the main thermal resistance of the heat sinks, which varies with the volume fraction and geometric alignment of the rebar and tendons, as well as the temperature and chemical composition. The target geometry for the containment walls of this work is the standard Korean NPP OPR1000. Sample tests and numerical simulations are conducted to verify the correlations for models with different densities of concrete, volume fractions, and alignments of steel. Estimation of the effective thermal conductivity and diffusivity of the containment wall models is proposed. The Maxwell model and modified Rayleigh volume fraction model employed in the present work predict the experiment and finite volume method (FVM) results well. The effective thermal conductivity and diffusivity of the containment walls are summarized as functions of density, temperature, and the volume fraction of steel for the analysis of the NPP accidents.

• 한국토양비료학회지
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• 제44권6호
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• pp.1314-1319
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• 2011

This study was carried out to investigate the surface soil organic carbon fractions affecting by different land use types, including needle-leaf forest (FN), broad-leaf forest (FB), pasture, annual upland cropping land (upland), and paddy rice land (paddy). We chose seven regions across Korean inland, considering sea level altitude, and measured soil organic carbon content and physico-chemical properties such as bulk density at a depth of 0~15 cm using core samples in April for the each land use type. In addition, labile organic carbon fractions in soil including light fraction and hot water extractable carbon were investigated. From this study, organic carbon storage (Mg C per ha) in the upper 15-cm soils was highest in FB (37.8), and decreased in the order of pasture (29.1), FN (28.8), paddy (21.9), and upland crop (19.9). In forest, more than 20% of soil organic carbon existed as light fraction, the free organic matter. Hot-water extractable carbon contents of soils in five land use types were lower than 7% of their soil organic carbon content.

• 열처리공학회지
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• 제37권3호
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• pp.103-113
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• 2024

Martensite volume fraction significantly affects the mechanical properties of alloy steels. Martensite start temperature (M_s), transformation temperature for martensite 50 vol.% (M₅₀), and transformation temperature for martensite 90 vol.% (M₉₀) are important transformation temperatures to control the martensite phase fraction. Several researchers proposed empirical equations and machine learning models to predict the Ms temperature. These numerical approaches can easily predict the Ms temperature without additional experiment and cost. However, to control martensite phase fraction more precisely, we need to reduce prediction error of the Ms model and propose prediction models for other martensite transformation temperatures (M₅₀, M₉₀). In the present study, machine learning model was applied to suggest the predictive model for the Ms, M50, M90 temperatures. To explain prediction mechanisms and suggest feature importance on martensite transformation temperature of machine learning models, the explainable artificial intelligence (XAI) is employed. Random forest regression (RFR) showed the best performance for predicting the Ms, M50, M90 temperatures using different machine learning models. The feature importance was proposed and the prediction mechanisms were discussed by XAI.