• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1634-1636
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• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta$-SiC-$TiB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_3$ and the annealing method. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_{5}Y_{3}O_{12}$). In pressureless annealing method, the relative density and the mechanical properties of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents because YAG of reaction between $Al_{2}O_3$ and $Y_{2}O_3$ was increased. But In pressured annealing method, reaction between $Al_{2}O_3$ and $Y_{2}O_3$ formed YAG but the relative density decreased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents. The electrical resistivity of the composites was all positive temperature coefficient resistance (PTCR) in the temperature range of 25$^{\circ}C$ to 700$^{\circ}C$.

• Fire Science and Engineering
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• v.16 no.4
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• pp.15-19
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• 2002

This dissertation is about the development of $BaTiO_3$-type PTC(Positive Temperature Coefficient) thermistor by composition method. A multilayer-type PTC samples were fabricated under optimal conditions after setting the experimental composition equation as ($Ba_{0.95-x}$S $r_{0.05}$$Ca_{x}$ )$TiO_3$-$0.01TiO_2$-$0.01SiO_2$-$\alpha$$MnCO_3$-$\beta$N $b_2$ $O_{5}$.) and their testing results were analyzed. The optimal sin-tering and cooling temperatures were 13$50^{\circ}C$ for two hours and $100^{\circ}C$/h for an hour, respectively; By composing Ca and Mn, dopants to lower the resistivity at room temperature, and Nb, a dopant to raise peak resistivity(Ca:5 mol%, Mn:0.08 mol%, Nb:0.18 mol%), appropriately, a PTC thermistor, having the characteristics of relatively low resistivity at room temperature and high peak resistivity and a good temperature coefficient, has been developed. And we find that it is possible of application for fire detection sensor.r.r.

• Herbal Formula Science
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• v.16 no.2
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• pp.101-114
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• 2008

Objective : The purpose of this study was to investigate the anti-inflammatory effects of Hwagae-san extract(HGSE) on the peritoneal macrophage. Methods : To evaluate anti-inflammatory effects of HGSE, We measured cytokines(interleukin-6; IL-6, interleukin-12; IL-12, tumor necrosis factor-${\alpha}$; TNF-${\alpha}$) and nitric oxide(NO) production in lipopolysaccharide(LPS)-induced macrophages. Furthermore, We examined molecular mechanism using western blot and also LPS-induced endotoxin shock. Results : 1. HGSE did not have any cytotoxic effect in the peritoneal macrophages. 2. HGSE reduced LPS-induced IL-6, TNF-${\alpha}$, IL-12 and NO production in peritoneal macrophages. 3. HGSE inhibited the activation of extracelluar signal-regulated kinase(ERK), C-Jun NH2-terminal kinase(JNK) but not of p38, degradation of IkB-${\alpha}$ in the LPS-stimulated peritoneal macrophages. 4. HGSE inhibited the production of TNF-$\alpha$, IL-6 and IL-12 in serum after LPS injection. Conclusion : These results suggest that HGSE may inhibit the production of TNF-${\alpha}$, IL-6, and IL-12 through inhibition of ERK and JNK activation, and that HGSE may be beneficial for inflammatory diseases.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.604-611
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• 2000

Glass-ceramics containing a cordierite (2MgO-2Al2O3-5SiO2) as a main crystal phase was prepared from MgO-Al2O3-SiO2 system glass through a controlled 2-step heat treatment for the application to magnetic memory disk substrate for higher storage capacity. Parent glasses prepared with addition of CeO2 as a fulx and TiO2 as a nucleating agent were crystallized by a 2-step heat treatment i.e. nucleation and crystal grwoth. Then the maximum nucleation and crystal growth rates were investigated and several properties such as bending strength, surface hardness and surface roughness were also studied for heat treated glass. As a result, only a $\alpha$-cordierite was precipitated as a main crystal phase for all heat treatment conditions and the maximum nucleation and crystal growth rates were 2.4$\times$109/㎣.hr at 80$0^{\circ}C$ and 0.3${\mu}{\textrm}{m}$/hr at 915$^{\circ}C$ respectively. After being nucleated at 80$0^{\circ}C$ for 5 hours and then crystallized at 915$^{\circ}C$ for 1 hour, the heat treated glass had a crystal volume fraction of 17.6% and crystal size fo 0.3${\mu}{\textrm}{m}$, and showed the optimum properties for the application to magnetic memory disk substrates as follows. ; Bending strength of 192 MPa, Vidkers hardness of 642.1kgf/$\textrm{mm}^2$, and surface roughness of 27$\AA$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.994-995
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• 2006

The microstructure of the extruded Al-20Si bars showed a homogeneous distribution of eutectic Si and primary Si particles embedded in the Al matrix. The grain size of ${\alpha}-Al$ varied from 150 to 600 nm and the size of the eutectic Si and primary Si in the extruded bars was about 100 - 200 nm. The room temperature tensile strength of the alloy with a powder size $<26{\mu}m$ was 322 MPa, while for the coarser powder ($45-106{\mu}m$) it was 230 MPa. With decreasing powder size from $45-106{\mu}m$ to $<26{\mu}m$, the specific wear of all the alloys decreased significantly at all sliding speeds due to the higher strength achieved by ultrafine-grained constituent phases. The fracture mechanism of failure in tension testing and wear testing was also studied.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.161-161
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• 2012

결정질 TiCrN과 AlSiN 나노층이 교대로 구성하는 나노 다층 TiAlCrSiN 박막은 음극 아크 플라즈마 증착법에 의해 증착되었다. 나노 다층 TiAlCrSiN 박막의 산화특성들은 $600{\sim}1000^{\circ}C$사이에서 대기 중 최대 70시간동안 연구 되었다. 형성된 산화물들은 주로 $Cr_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$ 그리고 rutile-$TiO_2$들로 구성되었다. 나노 다층 TiAlCrSiN 박막이 산화하는 동안, 가장 바깥쪽의 $TiO_2$층은 Ti 이온의 외부확산에 의해, 외부 $Al_2O_3$층은 Al이온의 외부확산에 의해 형성되었다. 동시에, 내부($Al_2O_3$, $Cr_2O_3$) 혼합층과 가장 안쪽의 $TiO_2$층은 산소이온의 내부확산에 의해 형성되었다.

• Journal of Animal Science and Technology
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• v.54 no.2
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• pp.133-139
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• 2012

A bacterium, identified as $Bacillus$ $amyloliquefacies$, CNL-90 using 16S rDNA analysis, was isolated from malt grain. The optimal activities of its ${\alpha}$-amylase and protease were observed at pH 6 and $60^{\circ}C$, and at pH 6 and $50^{\circ}C$, respectively although their activities remained stable at pH 7 and $40^{\circ}C$for ${\alpha}$-amylase and at pH 7 and $50^{\circ}C$ for protease. After solid-state fermentation of $B.$ $amyloliquefacies$, CNL-90 on wheat bran for 72hr or 144hr, the ${\alpha}$-amylase and protease activities were 170,000 and 290,000 units/kg, and 290,000 and 310,000 units/kg, respectively. The viable bacterial cell counts were $1.5{\times}10^9$ CFU/g and $2.2{\times}10^9$ CFU/g at 72hr and 144hr of the solid-state fermentation, respectively. A feeding trial with a total of 127 piglets was also conducted. The animals were divided into two groups: an experimental group fed with the fermented product (63 piglets) and a control group (64 piglets). The growth rate of the experimental group was 6.66% higher than that of the control group (P<0.05). The results of this study indicate that the ${\alpha}$-amylase and protease from $B.$ $amyloliquefacies$, CNL-90 can be used for industrial applications due to their activity in production of carbohydrate hydrolysates.

• Nuclear Engineering and Technology
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• v.29 no.5
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• pp.361-367
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• 1997

The phase separation in ferrite phase of duplex stainless steel is the primary cause of thermal aging embrittlement of the LWR primary pressure boundary components. In this study the phase separation of simulated duplex stainless steel was detected by Mossbauer spectroscopy and magnetic property analysis by VSM(Vibrating Specimen Magnetometer). The simulated duplex stainless steels, Fe-Cr binary, Fe-Cr-Ni ternary, and Fe-Cr-Ni-Si quarternary allots, were aged at 370 and 40$0^{\circ}C$ up to 5,340 hours. It was observed from Mossbauer spectra analysis that internal magnetic field increases with aging time and from VSM that the specific saturation magnetization and Curie temperature increase with aging time. These result are indicative that phase separation into Fe-rich region and Cr-rich region is caused by thermal aging in the temperature range of 370~40$0^{\circ}C$ In cases of specimens containing Ni, the increase of specific saturation magnetization is much higher. This implies that Ni seems to promote Fe-Cr interdiffusion, which accelerates the phase separation into Fe-rich $\alpha$ phase and Cr-rich $\alpha$' phase.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.644-651
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• 1999

In this experiment the Iron phthalocyanine (FePc) films on Si-wafer and alumina pallet were prepared using vacuum sublimation with conditions of changing reaction time, temperature, and deposition rate. Then, some samples were annealed following annealing. Techniques such as XRD, SEM, and resistance measurement method, were dedicated to characterize the changes of surface structure, phase transformation and electric resistance sensitivity in accordance with change of film thickness. In proportion to the decrease of deposition temperature from $370^{\circ}C$ to $350^{\circ}C$, intensities of (200), (011), (211) and (114) planes of $\alpha$-phase were decreased and (100) plane of $\beta$-phase were appeared. The film thickness were controlled by regulating the volume of precursor material during rapid deposition. As a result, it was observed that crystalline particle size had been increased according to the increase of film thickness and $\alpha$-phase transformed to $\beta$-phase. In consequence of measuring the crystallinity of films annealed between $150^{\circ}C$ and $350^{\circ}C$, $\alpha$- to $\beta$-phase transformation was appeared to begin at $150^{\circ}C$ and completely transformed to $\beta$-phase at $350^{\circ}C$. Electric resistance sensitivity of FePc film to $NO_x$ gas along temperature change of FePc films was observed to be more stable with the decrease of the film thickness.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.981-989
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• 1992

This is a study on the effects of cristobalite transition of quartz in semi-vitrious whiteware body, as addition of alkali and alkali earth oxides, prepared by pottery stone, feldspar, kaolin and clay minerals. The amounts of ${\alpha}$-quartz to ${\alpha}$-cristobalite transition, F.O.C. (fraction of cristobalite), were increased with firing temperature. In MgO added body, ${\alpha}$-quartz was decreased and the formation of cristobalite was increased. Effects of K2O addition was remarkably decreased the formation of cristobalite. Additive effects of MgO and K2O were confirmed that it was very different to variation of transition temperature of metakaolinite to Si-Al spinel structure in thermal reaction of kaolinite minerals. Result CaO addition was ineffective to transition temperature, and the transition temperature in Na2O added body was decreased, but relative intensity of quartz and cristobalite crystal in XRD results was decreased. This was characterized by the effects on the formation of liquid phase much more.