• Journal of the Korean Chemical Society
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• v.45 no.4
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• pp.312-317
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• 2001

7'-Aldehyde-nucleosides analogue (2a, 2c) were synthesized from 6-N-benzoyl-2',3'-O-isopropylideneadenosine and uridine. The condensation of 2 with ethoxycarbonylmethylene Wittig reagent produced the adenosine and uridine analogues containing extended conjugated diene and ethoxycarbonyl group, ethyl-1',5',6',7',8'-pentadeoxy-1'-(adenin-9-yl)-$\beta$-D-ribo-nona-5'(E),7'(E)-dienofuranuronate (4b) and ethyl-1'. 5',6',7',8'-pentadeoxy-1'-(uracil-1-yl)-$\beta$-D-ribo-nona-5'(E),7'-(E)-dienofuranuronate (4c). 9-[8',8'-dibromo-5',6',7',8' -tetradeoxy-$\beta$-D-ribo-octa-5'(E),7'(E)-diene]nucleosides (6b, 6c) were also prepared from 2 with similar method.

• School Mathematics
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• v.10 no.3
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• pp.339-355
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• 2008

This article tried to review the meaning and implication of six stages theory of learning mathematics suggested by Zoltan Dienes in "Building up Mathematics" in 1971. It was not much concretely known to Korean mathematics education society. In particular, there is no mathematical example which could cover all the stages to know what the theory tells. So this article focused on the example which Dienes developed for learning integers in 2000 to dig the theory. As a result, some critical aspects and problems of six stages theory were found. And finally educational implication was described.

• Elastomers and Composites
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• v.8 no.1
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• pp.33-51
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• 1973

We have studied the blending effects of Diene NF 35 R and Alfin 1530 at various blending ratios, 100/0, 70/30, 50/50, 30/70, 0/100, and of carbon black HAF-HS and ISAF-HS at various compounding ratios of 45 PHR, 55 PHR, 65 PHR, for tyre tread rubber. As the results, it was found that; 1. For tyre tread rubber, as the blending ratio, AR 1530/Diene NF 35R, indicated 70/30, the physical properties we examined were most excellent. 2. Excellent result was obtained in the case of carbon black compounding ratio of 55 PHR. The compounding of ISAF-HS made better result than that of HAF-HS for tensile strength, but the compounding of HAF-HS made better result than that of ISAF-HS for tearing strength and best result for abrasion quantity. 3. Heat buildup obtained from compounding carbon black HAF-HS indicated low temperature than that from compounding carbon black HAP-HS. As the compounding amount of carbon black increased, and as the blending amount of AR 1530 decreased, the heat buildup increased. 4. Carbon black was more efficient to AR 1630 than io Diene NF 35 R. 5. In the physical properties, mooney viscosity and mooney scorch time, as the compounding amount of carbon black increased, the values of mooney viscosity increased, but that of mooney scorch time had a max. point at the compoundiug amount of carbon black, 55 PHR.

• Elastomers and Composites
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• v.29 no.2
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• pp.121-130
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• 1994

The physical properties of rubber blend between natural rubber(NR) and ethylene propylene diene terpolymer(EPDM) were investigated as a study of EPDM composite materials. For EPDM/NR blends, the effects of ethylene and diene contents in EPDM, blend ratio, dicumyl peroxide(DCP) curing system on the physical properties, interfacial adhesion force and dynamic crack growth etc. were studied. EPDM/NR blends loaded with carbon black were prepared by mechanical mixing and cured by plate heating cure press. Crosslinking density was measured by swelling method with toluene. The physical properties of all blends were measured with Instron, fatigue to failure(FTF), Demattia flex cracking tester(DMFC), scanning electron microscopy (SEM), etc. As the ethylene and diene contents in EPDM increased, the physical properties, such as dynamic crack growth, adhesion to other component were increased too. Interfacial adhesion force of EPDM/NR blends to dissimilar layer was improved by the use of optimum peroxide curing system.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.829-837
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• 2002

Recently it was reported that cycloaddition of 6,6-disubstituted cyclohexa-2,4-dienone, 1 with cyclopentadiene gave solely the adduct of type 1.while its reaction with 1,3-cyclohexadiene gave both Ⅱ and Ⅲ. Semiempirical MO calculations were done to elucidate the origin of the selectivity difference between the two dienes. Cycloaddition of 1 with cyclopentadiene is controlled thermodynamically to give only 1-diene adduct by ΔGvalues of 10.6-20.3 kcal/mol, while its reaction with 1,3-cyclohexadiene does not show 1-diene/1-dienophile selectivity due to similar stabilities of the two adducts. Thermodynamic parameters also show that 두애 adducts are more fabourably fromed in the cycloadditions of 1 with both cyclopentadiene and 1,3-cyclohexadiene, which coincides with experimental observations. Cope rearrangements of endo adducts are another avenue to convert between 1-diene and 1-dienophile.

• Elastomers and Composites
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• v.58 no.3
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• pp.142-151
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• 2023

In this study, we investigate the thermal and mechanical properties of composites comprising ethylene propylene diene monomer (EPDM) and polybutadiene (PB) obtained using carbon black (CB) as a reinforcing and compatibilizing filler. Owing to the significance of elastomeric materials in various industrial applications, blending of EPDM and PB has emerged as a strategic method to optimize the material properties for specific applications. This study offers insights into the blend composition, its microstructure, and the resulting macroscopic behaviors, focusing on the synergetic effects of composite materials. Furthermore, this study delves into curing and rheological behaviors, crosslink densities, and mechanical, thermal, and elastic properties of the elastomeric composites. Through systematic exploration, we believe that this study will be beneficial to material scientists and engineers working on developing advanced elastomeric composites.

• Journal of the Korean Magnetic Resonance Society
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• v.10 no.1
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• pp.89-95
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• 2006

The methanolic extract of the marine sponge Raspilia hirsute collected from Keomun Island resulted in three types of sterols: a mixture of (24S)-Poriferasta-5, 25-diene-$3\beta$, 24-diol and (24R)-Stigmasta-5, 25-diene-$3\beta$, 24 -diol (1), 25,26,27-Trinorcholest-5-en-$3\beta$,24-diol (2), and Pregn-5-en-20-on-$3\beta$-ol (3). The isolation and structural determination of these sterols are reported here. Compound 1 showed moderate cytotoxicity against human Leukemia cell line K562.

• YAKHAK HOEJI
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• v.48 no.1
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• pp.65-69
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• 2004

The chromatographic separation of MeOH extract of the aerial parts of Aster glehni (Compositae) led to the isolation of three sesquiterpenes, two sterols and four terpenes. Their structures were determined to be $\beta$-amyrin acetate (1), phytol (2), alismol (3), $\alpha$-tocopheryl quinone (4), $\alpha$-spinasterol (5), 10-O-methyl alismoxide (6), alismoxide (7), and 3-O-(6'-O-palmitoyl-$\beta$-D-glucosyl)-spinasta 7,22-diene (8) by physicochemical and spectroscopic methods . These compounds (1-8) were first isolated from the Aster glehni.

• Elastomers and Composites
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• v.21 no.3
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• pp.255-271
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• 1986

• Elastomers and Composites
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• v.22 no.1
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• pp.29-43
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• 1987