• Journal of Powder Materials
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• v.11 no.1
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• pp.69-73
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• 2004

The sintering characteristics of commercial 7xxx series Al-Zn-Mg-Cu alloy have been investigated. Sintering system of this blended elemental powder has aspects of both transient and supersolidus liquid phase sintering. Transient liquids occur when the constitution point during sintering lies in a solid phase region but where the sintering temperature is greater than either the melting point of one of the constituent or a eutectic temperature. Supersolidus liquid phase sintering occurs when a preblended powder is heated to a temperature between the solidus and liquids. However, these reaction were restrained their inter diffusion due to the appearance of the oxide film. Thus, 7xxx series Al alloy is extremely sensitive to process variables, including particle size, holding time and sintering temperature. Therefore, above phenomenons were observed formation and behaviour of the liquid by using SEM and DSC.

• YAKHAK HOEJI
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• v.26 no.3
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• pp.185-188
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• 1982

In order to investigate the antitumor components of Korean wild higher fungi, the carpo-phores of Pholiota squarrosa collected in Kaung Nung area were extracted with water by refluxing for eight hours at 80-90.deg. C. The extracts were dialized for six days against distilled water and lyophilized to produce crude polysaccharide powders. They were found to have the antitumor activity against sarcoma 180 implanted in mice. Especially, the inhibition ratio of the extract of Pholiota squarrosa was 78.7% in the dose of 20mg/kg/day for the period of ten days. The tumor in two of the ten mice was completely regressed. The components of these aqueous extracts were found to be polysaccharide and protein. The total polysaccharide was 42% by Anthrone method and the protein was 55% by Lowry-Folin method in the antitumor component of Pholiota squarrosa.

• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.171-175
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• 1999

Novel process for high power catalyst electrode for PEM fuel cell has been developed. MEA having this catalyst electrode showed $0.5W/cm^2\;with\;0.2mg/cm^2$ of Pt loading at aunospheric humid hydrogen and oxygen condition. In this process, platinized carbon and plain carbon powders were coated with ionomer (Nafion) and hydrophobic polymer (PTFE), respectively and it could maximize two roles of catalyst electrode, l.e., reaction and gas supplying component. Those polarization characteristics proved the improved performance by reducing potential drop especially in the concentration polarization region.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.35-42
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• 1985

$eta$-Sialon powders were prepared by reduction-nitridation from mixture of Wando pyrophyllite and graphite as a reducing agent at 135$0^{\circ}C$ in 80% $N_2$-20% $H_2$ atmosphere. As the reaction products $Si_2ON_2$, $\beta$-$Si_3N_4$ a--$Si_3N_4$ and $\beta$-SiC were observed. Additive agents of MgO, CaO, $Y_2O_3$ were used for promoting the reduction and nitridiation aeaction. The present study was conducted to investigate the effects of silica-carbon ratio ($SiO_2$/C=weight ratio), raction time gas flow rate pellet size and powder packing on synthesis of $\beta$-Sialon from Wando pyropyllite.

• Journal of Powder Materials
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• v.11 no.3
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• pp.193-201
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• 2004

1960년 Au-Si계 합금에서 처음으로 비정질상이 급속 응고법에 의해 보고된 이래/sup 1)/ 지난 40년 간 많은 합금계에서 비정질상이 보고되어졌다. 대표적으로 Fe-, Ni-, Co기 합금 등 많은 합금계에서 비정질상이 보고되었으나, 비정질상의 형성을 위해서는 약 105 K/s이상의 높은 냉각속도를 필요로 하였다. 1980년대 수백 K/s의 낮은 냉각속도 하에서도 비정질상이 형성될 수 있는 다원계 합금(multi-component alloy)이 Mg-Ln-(Ni, Cu, Zn), Ln-Al-TM 합금에서 보고되어 졌으나 많은 관심을 받지 못하다가 1993년 Zr-Ti-Ni-Cu-Be 합금에서 수 ㎝ 크기의 비정질합금 제조가 보고되면서 전 세계적으로 많은 관심을 받게 되었다. Zr-Ti-Ni-Cu-Be계 벌크 비정질 합금이 보고된 후 Zr-(Nb,Pd)-Al-TM, Pd-Cu-Ni-P, Fe-Co-Zr-Mo-W-B, Ti-Zr-Ni-Cu-Sn등 여러 합금계에서 벌크 비정질 합금이 보고되었다. (중략)

• Food Science and Preservation
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• v.4 no.1
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• pp.45-51
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• 1997

In our studies on the role of $\beta$-galactosidase in fruit softening, significant difficulty, was encountered in our attempts to extract RNA from persimmon(Diospyros kaki L. cv. Fuyu) fruit due to astringency and tannin content. Initial, unsuccessful RNA extractions involved methods using guanidinium isothiocyanate/CsCl with and without polyvinylpyrrolidone(PVP), phenol/sodium lauryl sulfate(SDS), guanidinium hydrochloride, as well as polysomal RNA purification method that used 0.2 M Tris-HCI (pH 9.0) containing KCI, Mg-acetate, EDTA, $\beta$-mercaptoethanol, and sucrose. A method was devised which employed treatment of fruit with CO2 gas to diminish astringency prior to RNA extraction, followed by extraction of tissue powders with Proteinase K extraction buffer containing PVP and ascorbate at an alkaline pH. This procedure resulted in the removal of tannins and other polyphenolics and extraction of relatively large amount of high-quality RNA suitable for cDNA library construction and polymerase chain reaction(PCR). Futhermore, the procedure does not use the toxic and corrosive chemical guanidinium isothiocyanate or require ultracentrifugation.

• Journal of Life Science
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• v.20 no.2
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• pp.237-244
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• 2010

Five mold strains - Mucor racemousus, Rhizopus oryzae, Aspergillus oryzae, Aspergillus kawachii, and Monascus purpureus - were used for the fermentation of both freeze-dried and air-dried silkworm powders. The concentrations of proteins and minerals, electrophoretical protein patterns, fatty acid composition and the activities of fibrinolytic and antioxidation with freeze-dried silkworm (FDSW) or air-dried silkworm powders (ADSW) fermented by the five molds were investigated. The concentrations of major minerals in fermented FDSW and ADSW powders were K by 72.0-76.3 and 77.1-78.9 ppm, Mg by 29.6-49.7 and 44.3-58.7 ppm, Ca by 1.9-14.9 and 9.8-21.6 ppm and Zn by 0.64-0.70 and 4.17-4.52 ppm, respectively. Major fatty acids in fermented FDSW and ADSW powders were linolenic acid, oleic acid, and palmitic acid. There were slightly varietal differences in electrophoretical protein patterns when total protein patterns of fermented FDSW and ADSW powders were analyzed by native-and SDS-polyacrylamide gel electrophoresis (PAGE). DPPH radical scavenging activity was slightly stronger in fermented ADSW powders than that in fermented FDSW. Fibriolytic activity was only detected in the FDSW fermented by Aspergillus kawachi and Monascus purpureus. These results may provide the basic data to understand the biological activities and chemical characteristics of silkworm fermented by mold, which can be used for the development of functional foods.

• Korean Journal of Materials Research
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• v.17 no.6
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• pp.318-322
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• 2007

Porous ${\beta}-tricalcium$ phosphate $({\beta}-TCP)$ bioceramic was fabricated by pressureless sintering using commercial HAp and different volume percentages of PMMA powders (30-60 vol.%). The range of spherical pore size was about $200-250\;{\mu}m$ in diameter. By increasing the PMMA content, the number of pores and their morphology were dramatically changed as well as decreased the material properties. In case of using 60 vol.% PMMA content, network-type pores were found, due to the necking of the PMMA powders. The values of relative density, elastic modulus, bending strength and hardness of the 60 vol.% PMMA content sample, sintered at $1500^{\circ}C$, were about 46%, 22.2 GPa, 5MPa and 182 Hv respectively. Human osteoblast-like MG-63 cells and osteoclast-like Raw 264.7 cells were well grown and fully covered all of the porous ${\beta}-TCP$ bodies sintered at $1500^{\circ}C$.

• Korean Journal of Materials Research
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• v.5 no.1
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• pp.55-62
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• 1995

Cordierite powders were prepared by a controlled hydrolysis of metal alkoxides with ethanol and distilled water. HC1 was used as a catalyst. The amount of HCI catalyst used was in range of 0.1-0. 5mol per lmol of TEOS. Effects of HC1 catalyst on the characteristics of cordierite powder were examined. $\alpha$-Cordierite powder prepared with HCI/TEOS mol ratio of O.lmol/mol was crystallized at $1050^{\circ}C$. On the other hand, $\alpha$-cordierite powders prepared with HCI/TEOS rnol ratio of 0.3 and 0.5rnol/mol were crystallized at $950^{\circ}C$. Spinel( mA120a) phase remained up to $1300^{\circ}C$ in the cordierite powder prepared with HCI/TEOS rnol ratio of 0.lrnolirnol. On the contrary, spinel phase was absent, and mordierite was the only phase remalned at $1300^{\circ}C$ in the cordierite powder prepared with HCI/TEOS mol ratio of 0.3 and O:5mol/mol.

• Korean Journal of Materials Research
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• v.25 no.4
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• pp.165-170
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• 2015

Ceramics biomaterials are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/${\beta}$-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/${\beta}$-TCP powders with 10-30 wt% $NH_4HCO_3$ as a space holder(SH) and $TiH_2$ as a foaming agent, and MgO powder as a binder. The HA/${\beta}$-TCP powders were consolidated by spark plasma sintering(SPS) process at $1000^{\circ}C$ under 20 MPa conditions. The effect of SH content on the pore size and distribution of the HA/${\beta}$-TCP composite was observed by scanning electron microscopy(SEM) and a microfocus X-ray computer tomography system(SMX-225CT). These microstructure observations revealed that the volume fraction of the pores increased with increasing SH content. The pore size of the HA/${\beta}$-TCP composites is about $400-500{\mu}m$. The relative density of the porous HA/${\beta}$-TCP composite increased with decreasing SH content. The porous HA/${\beta}$-TCP composite fabricated with 30%SH exhibited an elastic modulus similar to that of cortical bone; however, the compression strength of this composite is higher than that of cortical bone.