• Journal of the Korean Society for Heat Treatment
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• v.16 no.4
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• pp.197-204
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• 2003

Honeycomb structure has been fabricated by brazing method using 0.1 wt%C and 1.0wt%C carbon steel core and STS304 stainless steel face sheet. Core shear strength ratio in W and L directions was 1:1.03 in 7 mm cell size, whereas 1:1.45 in 4 mm cell size. Flexural strength on face sheet was 166.4 MPa (0.1 wt%C, W direction), 171.1 MPa (0.1 wt%C, L direction), and 120.2 MPa (1.0 wt%C, W direction) in 7 mm cell size. And in 4mm cell size specimen, it was 169.2 MPa (0.1 wt%C, W direction), 224.2 MPa (0.1 wt%C, L direction). This means that flexural strength of 0.1 wt%C core material was higher than that of 1.0wt%C core material, which was contrary to expectation. SEM and EDS analysis represented that grain boundary diffusion had occurred in0.1 wt%C core, but no grain boundary diffusion in 1.0 wt%C core. And corrugated surface of 0.1 wt%C core was flat, whereas that of 1.0 wt%C core was not flat. As a result, contact area between two 1.0 wt%C cores was much less than that of 0.1 wt% cores, It is thought to be main reason for lower flexural strength of 1.0 wt%C core.

• Journal of Powder Materials
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• v.16 no.4
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• pp.275-279
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• 2009

The aging characteristics of gas atomized Mg-6 wt.% Al-1 wt.% Zn alloy were investigated and compared to those of cast Mg-6 wt.% Al alloy. The gas atomized Mg-6 wt.% Al-1wt.% Zn alloy powders had spherical morphology between 1 and 100 $\mu m$ in diameter. After compaction under the pressure of 700 MPa at $320^{\circ}C$ for 10 min, the Mg-6 wt.% Al-1 wt.% Zn alloy showed a grain size of approximately 40 $\mu m$ which is smaller than that of the cast Mg-6 wt.% Al alloy, and a relative compact density of approximately 93%. After ageing, the Mg-6 wt.% Al-1 wt.% Zn alloy showed much faster peak hardness than cast Mg-6 wt.% Al alloy. The Mg-6 wt.% Al-1 wt.% Zn alloy showed the new fine precipitations with ageing time, while the cast Mg-6 wt.% Al alloy was almost similar morphology.

• Journal of Korea Foundry Society
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• v.33 no.2
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• pp.55-62
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• 2013

Effect of Fe and Mn contents on the castability of Al-4wt%Mg-0.9wt%Si system alloy has been studied. According to the analysis of cooling curve for Al-4wt%Mg-0.9wt%Si-0.3wt%Fe-0.3/0.5wt%Mn alloy, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ and ${\beta}-Al_5FeSi$ phases crystallized above eutectic temperature of $Mg_2Si$. Therefore, these phases affected both the fluidity and shrinkage behaviors of the alloy during solidification. As Fe and Mn contents of Al-4wt%Mg-0.9wt%Si system alloy increased from 0.1 wt% to 0.4 wt% and from 0.3 wt% to 0.5 wt% respectively, the fluidity of the alloy decreased by 26% and 33%. When Fe content of the alloy increased from 0.1 wt% to 0.4 wt%, 23% decrease of macro shrinkage and 19% increase of micro shrinkage appeared. Similarly, Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, 11% decrease of macro shrinkage and 14% increase of micro shrinkage appeared. Judging from the castability of the alloy, Al-4wt%Mg-0.9wt%Si alloy with low content of Fe and Mn, 0.1 wt% Fe and 0.3 wt% Mn, is recommendable.

• Journal of the Korean earth science society
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• v.32 no.7
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• pp.707-718
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• 2011

We study the natural background and geochemical characteristics on geological groups of stream sediment in the Boseong-Hwasun area. We collected 186ea stream sediment samples along the primary channels and dried them naturally in laboratory. The contents of major, trace and rare earth elements were determined by XRF, ICP-AES and NAA analysis methods. In order to know the natural background and geochemical characteristics of geological groups, we classified the studied area into granitic gneiss (GGn) area and porphyroblastic gneiss (PGn) area. The contents range of major elements for GGn area is $SiO_2$ 45.5-73.09 wt.%, $Al_2O_3$ 12-20.76 wt.%, $Fe_2O_3$(T) 3.72-8.85 wt.%, $K_2O$ 2.38-4.2 wt.%, MgO 0.75-2.77 wt.%, $Na_2O$ 0.78-1.88 wt.%, CaO 0.27-2.1 wt.%, $TiO_2$ 0.56-1.72 wt.%, $P_2O_5$ 0.06-0.73 wt.% and MnO 0.03-0.95 wt.%, and for PGn area it is $SiO_2$ 43.74-70.71 wt.%, $Al_2O_3$ 11.54-25.05 wt.%, $Fe_2O_3$(T) 3.44-13.46 wt.%, $K_2O$ 2.08-3.86 wt.%, MgO 0.65-2.99 wt.%, $Na_2O$ 0.63-1.7 wt.%, CaO 0.35-2.07 wt.%, $TiO_2$ 0.68-4.17 wt.%, $P_2O_5$ 0.1-0.31 wt.% and MnO 0.07-0.33 wt.%. The contents range of hazard elements for GGn area is Cr 41.7-242 ppm, Co 7.6-25.1 ppm, Ni 12-61 ppm, Cu 10-47 ppm, Zn 48.5-412 ppm, Pb 17-215 ppm, and for PGn area, it is Cr 29.6-454 ppm, Co 5.9-53.7 ppm, Ni 8.7-287 ppm, Cu 6.4-134 ppm, Zn 43.6-370 ppm, Pb 15-37 ppm area. There is a good correlation between Cr and MgO and Co among $Al_2O_3$, $Fe_2O_3$(T), MgO and Ni among $Fe_2O_3$(T), CaO, MgO whereas Cu, Zn and Pb have a low correlation for major elements in GGn area. Generally Cr, Co, Ni, and Cu have a good correlation with major elements, but a low correlation with Zn and Pb in PGn area.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.10b
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• pp.31-31
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• 1994

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.26-26
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• 1994

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.45-50
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• 2002

Effect of sintering additives on the densification behavior of reaction-bonded silicon nitride prepared by using coarse Si powders is discussed. Sintering additives such as 6 wt% $Y_2O_3$+1wt% $A1_2O_3$ (6YlA) did not give rise to full densification, while full densification was obtained by using the sintering additives such as 6wt% $Y_2O_3$+3 wt% $A1_2O_3$+ 2wt% $SiO_2$ (6Y3A2S) and 9wt% $Y_2O_3$+ 1.5wt% $A1_2O_3$+ 3wt% $SiO_2$ (9Yl.5A3S). In the case of 6Y3A2S addition, high fracture strength of 960 MPa and the fracture toughness of $6.5 MPa.m^{1/2}$ were obtained.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.154-154
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• 1994

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.37-39
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• 1991

This paper is studies the effects of additives on the magnetic properties of Sr-ferrite. The specimens have been composed of SrO and Fe$_2$O$_3$with ratio of 1:5.9. As 1st additives, it is mixed to 0.2wt%, 0.7wt% and 1wt% of CaCo$_3$with 0.3wt% SiO$_2$. As 2nd addition, it is mixed to 0.5wt%, 1wt% of Na$_2$SiO$_3$, 0.5wt%, 1wt% of Cr$_2$O$_3$and 0.5wt%, 1wt% of Al$_2$O$_3$and sintering conditions was carried out at 1210$^{\circ}C$, 1230$^{\circ}C$ and 1250$^{\circ}C$. From experiments on the magnetic properties of specimen, the results were shown follows; (1) In case of additive SiO$_2$and CaO, it is stable magnetoplumbite structure for liquid phase grown, enhances mignetic propertics. (2) In case of basic compositions + 0.5wt% Al$_2$O$_3$, it is confirmed better properties by increasing of the coercivity than 0.5wt% Cr$_2$O$_3$additives. (3) In case of mixed additives of Cr$_2$O$_3$and Al$_2$O$_3$, magnetic propeties decrease with sintering density.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.240-244
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• 2018

There is growing concern about cross infection among the patients to patients, patients to staffs, and tools to patients in healthcare facilities, especially in dentistry. In this study, the most widely used dental impression materials were prepared and the synergy effect of Chlorhexidine and essential oil on antimicrobial activity was examined in the impression materials. Chlorhexidine concentration of 0.1 wt% and 0.5 wt% showed no antimicrobial activity on Escherichia coli (E. coli) and Candida albicans. At 1.0 wt% Chlorhexidine, 0% of E. coli and 34.7% of Candida albicans were survived. Bergamot (Essential oil) concentration of 0.5 wt% and 1.0 wt% showed no antimicrobial activity on E. coli. At 2.0 wt% Bergamot oil, 71.9% of E. coli were survived. Tea tree oil (Essential oil) of 0.5 wt% showed no antimicrobial activity on E. coli. At 1.0 wt% Tea tree oil, 11.2% of E. coli was survived. At 2.0 wt% Tea tree oil, no E. coli was survived. However, no E. coli was survived at the concentration of 0.8 wt% Bergamot with 0.3 wt% Chlorhexidine. At the concentration of 0.8 wt% Tea Tree oil with 0.3 wt% Chlorhexidine, 1.3% of E. coli were survived. The experimental results showed that the synergy effects between Chlorhexidine and essential oils on antimicrobial activity were prominent.