• Journal of the Korean Chemical Society
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• v.44 no.6
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• pp.592-599
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• 2000

The fine particles of binary ceramic composite of titania-partially-stabilized zirconia(TPSZ) were synthesized by ultrasonic spray pyrolysis at the various temperatures, compositions and concentrations and the effects of process factors for synthesis on the characteristics of fine particles were discussed. The starting salt solutions were prepared to have the ionic concentrations of 0.025~0.1 M aqueous solutions. The fine particles were prepared to have the compositions of 90~97.5 wt% of $ZrO_2$ and 2.5~10 wt% of $TiO_2$. The temperatures for particle synthesis were regulated to be 400~550$^{\circ}C$ as a drying zone, 800~1100$^{\circ}C$ as a pyrolysis zone. The produced fine particles were collected by a wet process and analyzed to investigate characteristic properties after being dried. The compositions of ceramic fine particles were determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy(ICP-AES) technique and phases, morphologies and particle sizes of those were investigated by Raman Spectroscopy, X-ray diffraction(XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy(TEM) and Particle Size Analyzer(PSA) techniques.

• Journal of Microbiology and Biotechnology
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• v.19 no.4
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• pp.372-377
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• 2009

The chemical compositions and antibacterial and antifungal activities of essential oils extracted from Abies holophylla and A. koreana were investigated. GC-MS analysis revealed that 38 compounds comprised 95.88% of the A. holophylla essential oil, with the main components being bicyclo[2.2.1]heptan-2-ol(28.05%), ${\delta}3$-carene(13.85%), $\alpha$-pinene(11.68%), camphene(10.41%), dl-limonene(7.61%), $\beta$-myrcene(7.11%), trans-caryophyllene(5.36%), and $\alpha$-bisabolol(3.67%). In the essential oil from A. koreana, 36 compounds comprised 98.67% of the oil, and the main compounds were bornyl ester(41.79%), camphene(15.31%), $\alpha$-pinene(11.19%), dl-limonene(8.58%), fenchyl acetate(5.55%), and $\alpha$-terpinene(2.29%). Both essential oils showed great potential of antibacterial activity against several bacteria tested, in the range of 2.2-$8.8{\mu}g$ per disc by the agar disc diffusion method, and minimal inhibitory concentration(MIC) values of 5.5-21.8 mg/ml by the microdilution method. Both oils showed very effective antifungal activities toward all pathogenic strains tested, including Candida glabrata, with MIC values in the range of 0.5-2.2 mg/ml. As a whole, A. koreana oil showed better antibacterial and antifungal properties than A. holophylla oil.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.24-29
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• 2000

Yoqurt products are known to be effective for enhancing health and preventing diseases such as cancers. Such effects are generally believed to be due to actions of polysacchmides in yoqurt products. In this study we have determined compositions of monosaccharides in hydrolysates of commercial yoqrtrt products as the first step of understanding structures of polysaccharides. The yoqtrrt products were ttltracentrifuged, filtered, hydrolyzed in 1M sulfuric acid and neutralized. A portion of the solution was taken and evaporated to dryness, denvatized with TMSI (trimethly- silylimidazole) and analyzed by GC/MS. We found that the monosaccharides were fructose, glucose, and galactose. Their compositions were variant among several yoqtrrt products.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.115-140
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• 2010

Great concerns about atmospheric aerosols are attributed to their multiple roles to atmospheric processes. For example, atmospheric aerosols influence global climate, directly by scattering or absorbing solar radiations and indirectly by serving as cloud condensation nuclei. They also have a significant impact on human health and visibility. Many of these effects depend on the size and composition of atmospheric aerosols, and thus detailed information on the physicochemical properties and the distribution of airborne particles is critical to accurately predict their impact on the Earth's climate as well as human health. A single particle analysis technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) that can determine the concentration of low-Z elements such as carbon, nitrogen and oxygen in a microscopic volume has been developed. The capability of quantitative analysis of low-Z elements in individual particle allows the characterization of especially important atmospheric particles such as sulfates, nitrates, ammonium, and carbonaceous particles. Furthermore, the diversity and the complicated heterogeneity of atmospheric particles in chemical compositions can be investigated in detail. In this review, the development and methodology of low-Z particle EPMA for the analysis of atmospheric aerosols are introduced. Also, its typical applications for the characterization of various atmospheric particles, i.e., on the chemical compositions, morphologies, the size segregated distributions, and the origins of Asian dust, urban aerosols, indoor aerosols in underground subway station, and Arctic aerosols, are illustrated.

• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.28-33
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• 1994

The chemical compositions of pine bark from mechanical pulp industry were determined, and effect of Ca base acid sulfite on bark cooking was investigated under various conditions. The pine bark was composed of 39.5 % alkali extractives, 50.3 % lignin, and a small amount of carbohydrate. The contents of alkali extractives and lignin were remarkably higher than those of pine wood. The bark was composed of high content of arabinose and xylose, while the wood was composed of high content of mannose. When pine bark was cooked with 75 % free acid at 145 $^{\circ}C$, the rate of cooking and delignification was improved with the increase of total acid, but it was very difficult to delignify the bark by 50 % and over under these conditions. In the presence of 60~65 % free acid and at 155~165 $^{\circ}C$, initial cooking rate, delignification, and delignification selectivity were considerably increased, but condensation reaction of lignin was considerable at the end of cooking. Therefore, it was shown that pine bark was very difficult to delignify by the Ca-base acid sulfite cooking.

• Fibers and Polymers
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• v.5 no.1
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• pp.31-38
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• 2004

In the present paper, a variety of fiber reinforcements, for instance, stabilized OXI-PAN fibers, quasi-carbon fibers, commercial carbon fibers, and their woven fabric forms, have been utilized to fabricate pseudo-unidirectional (pseudo-UD) and 2-directional (2D) phenolic matrix composites using a compression molding method. Prior to fabricating quasi-carbon fiber/phenolic (QC/P) composites, stabilized OXI-PAN fibers and fabrics were heat-treated under low temperature carbonization processes to prepare quasi-carbon fibers and fabrics. The thermal conductivity and thermal expansion/contraction behavior of QC/P composites have been investigated and compared with those of carbon fiber/phenolic (C/P) and stabilized fiber/phenolic composites. Also, the chemical compositions of the fibers used have been characterized. The results suggest that use of proper quasi-carbonization process may control effectively not only the chemical compositions of resulting quasi-carbon fibers but also the thermal conductivity and thermal expansion behavior of quasi-carbon fibers/phenolic composites in the intermediate range between stabilized PAN fiber- and carbon fiber-reinforced phenolic composites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.213-221
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• 1987

To use fly ash as an additive for concrete, authors collected 15 kinds of domestic fly ashes and tested the chemical compositions and physical properties of the fly ashes. Fluidity of the fly ash paste was also investigated. The result shows that the chemical compositions of the fly ashes were in the range of regulation of Korean Industrial Standards except ignition loss and the following relationships in fly ash were studied; specific surface and residue in standard sieve, specific surface and unit weight, residue in standard sieve and ignition loss. For the given flow properties, fly ash paste required higher water-binder ratio than cement paste.

• Economic and Environmental Geology
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• v.18 no.3
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• pp.253-261
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• 1985

Detailed chemical compositions of thirteen montmorillonites and their thermal behaviour by differential thermal and thermogravimetric analysis have been studied. Comparison of structural formulae with experimental results by thermal analysis gave evidence of that both substitutions of Fe for Al in octahedral and Al for Si in tetrahedral positions appear to affect dehydroxylation temperature, which is valid for the present samples. Further detailed study of this topic using well-known samples which have various degree of substitution will be justified.

• Economic and Environmental Geology
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• v.31 no.5
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• pp.447-458
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• 1998

The spinel Ihelzolite of ultramafic xenoliths are found in the alkali basalt from eastern part of the Cheju island, Korea. The xenolith is are mainly composed of olivine, orthopyroxene, clinopyroxene and spinel. Based on the chemical compositions of the constituent minerals, the ultramafic xenolith belong to upper mantle peridotite. Each minerals have a protogranular texture. Olivine with kink band texture partly shows undulatory extinction. Some clinopyroxenes have spongy textured rims. Brown spinels occur in the interstices between olivine and pyroxene grains. Olivine is mostly forsterite $(Fo_{89-90})$. Orthopyroxene is enstatite $(Wo_{1.3}En_{88.4}Fs_{10.3})$ with 3.87~5.25 wt% $Al_{2}O_{3}$. Clinopyroxene is diopside $(Wo_{48.0}En_{46.2}Fs_{5.8})$ with 6.75~5.03 wt% $Al_{2}O_{3}$. Spinel has the Mg value of 75.9 and its Cr-number is 10.2. According to the PoT estimations for the mantle xenoliths, equilibrium temperatures of the xenoliths range from 1023 to $1038^{\circ}C$ and pressure is 18 kbar. Spinellhelzolite from this area, which is characterized by lower Cr-number (10.2) and homogeneous chemical compositions, supports that these ultramafic xenoliths are derived from the upper mantle.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.141-144
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• 2011

We report the synthesis of $SrTiO_3$, $BaTiO_3$ and $Ba_xSr_{1-x}TiO_3$ (BST) nanoparticles (NPs) in various compositions (x = 0.25, 0.5 and 0.75) by an inorganic sol-gel method under a basic condition. Highly crystalline nanoparticles were formed at the reaction temperature of 25 - $100^{\circ}C$ from a stabilized titanium alkoxide in tetramethylammonium hydroxide (TMAH) and barium or strontium acetate in aqueous solution. Morphology and particle structure of the synthesized BST NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BST nanoparticles in various compositions were monodispersed without mutual aggregation, and their average sizes were in the range of 70 - 80 nm. Furthermore, they showed highly crystallized perovskite phase over the whole composition range from $SrTiO_3$ to $BaTiO_3$. We also proposed a mechanism for the low-temperature formation of BST NPs.