• Transactions of Materials Processing
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• v.23 no.6
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• pp.386-391
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• 2014

In the current study, Al-Mn-Zn alloys are strip-cast and used as the base alloy for the core of aluminum clad sheets used in automotive condenser fins. Transition elements such as Cu and Cr are added to the base core alloy in order to improve the properties of the clad sheets. The AA4343/Al-Mn-Zn-X(X: Cu, Cr)/AA4343 clad sheets are fabricated by roll bonding and further cold-rolled to a thickness of 0.08 mm. Clad sheets were intermediately annealed during cold rolling at $450^{\circ}C$ in order to obtain 40% reduction at the final thickness. Tensile strength and sag resistance of the clad sheets are improved by Cu additions to the core alloy, while corrosion resistance is also increased. Cr-additions to the clad sheets enhance sag resistance and provide low enough corrosion, although tensile strength is not improved. The effect of Cu and Cr additions on the properties of the clad sheets is elucidated by microstructural analysis.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.91-97
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• 2012

The effects of Bi and Sb additions on the microstructures and casting properties in lead-free Cu-Zn-Sn broze were investigated. (1) When only Bi was added to the bronze, Bi was precipitated on the ${\delta}$ phase of ${\alpha}$ dendrite cell boundary. When Bi and Sb were added together, Bi was precipitated on the ${\delta}_A$ which was the Sb-rich area in the ${\delta}$ phase. (2) The addition of Sb accelerated the formation of ${\delta}$ phase, and when Sb, Bi and Pb were added, Bi and Pb were precipitated as mixed solution in the ${\delta}_A$ phase. (3) The combined addition of Sb and Bi resulted in the suppression of shrinkage due to the complementary effects of the mass feeding of ${\alpha}$-dendrite cluster covered with ${\delta}$ phase and sealing of micro-shrinkage in the ${\delta}$ phase by solidification expansion of Bi.

• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.27-32
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• 2009

The microstructure of Al-7Si-0.4Mg-1Fe alloy mainly consists of aluminum dendrites, Al-Si eutectics, and $Al_5FeSi$ needles. When Mn was added to the alloy, the substantial amount of $Al_5FeSi$ phase was changed into Al(Mn,Fe)Si, however the needle-like morphology was almost unchanged. Combined additions of Cr or Sr with Mn to the base alloy resulted in rod-like Al(Mn, Fe,Si)Si phase. The tensile properties of as-cast alloys were enhanced by the Mn addition, especially when it was added with Sr. The tensile properties after T6 heat treatment was a little improved with 0.7%Mn addition, but Cr or Sr additions with Mn didn't show any positive effect on the properties of heat-treated alloys.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.299-299
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• 2010

In this study, microwave properties with compositions and frequency of the $Ba_3Co_2Fe_{24}O_{41}$ ceramics with Zn substitution for Co were investigated. From the XRD patterns, hexagonal structure of Z-type phase was existed as main phase. Diffraction peaks of Z-type phase were shifted to lower angle by Zn substituted for Co site. The permittivity was increased with Zn additions. In all composition, loss tangent of permittivities were increased with frequency. Permeability and magnetic resonance frequency were increased with Zn additions. Permeability was increased and loss tangent of permeability was decreased rapidly over 600 MHz~800 MHz. The loss tangent of permeability did not changed with composition ratio. In the case of $Ba_3Co_{1.6}Zn_{0.4}Fe_{24}O_{41}$ ceramics sintered at $1250^{\circ}C$ for 3 hours, the permittivity, loss tangent of permittivity, permeability and loss tangent of permeability were 28.277, 0.193, 22.992 and 0.065 at 310 MHz, respectively.

• Korean journal of food and cookery science
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• v.20 no.5
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• pp.511-519
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• 2004

The optional ingredient, Maesil juice, was adopted to improve the quality of Yulmoo Mul-Kimchi during fermentation. The final weight of the Maesil juice as a percentage of the water content in the Yulmoo Mul-Kimchi was adjusted to 0, 1, 3, 5 and 7%. The physicochemical, microbiological and sensory characteristics were determined during fermentation at 10$^{\circ}C$ over a 30 days period. After fermentation, the additions of 3 and 5% Maesil juice gave the highest pH values and lowest total acidities. With regard to the reducing sugars, the 3 and 5% treatments gave the highest contents. The number of the total cell count and lactic acid bacteria increased to their maxima during fermentation, but began to decrease during the latter stages. Here, the additions of 3 and 5% Maesil juice showed distinctive lower and higher numbers of total cells and lactic acid bacteria, respectively, during the latter stages of fermentation. With regard to the sensory evaluation on the addition of Maesil juice, the results obtained with 3 and 5% additions to the fermented Yulmoo Mul-Kimchi were favored for color, smell, sour and carbonated tastes and overall acceptability of the products. Therefore, the optimum levels of Maesil juice addition to Yulmoo Mul-Kimchi were estimated to be between 3 and 5%.

• Korean journal of food and cookery science
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• v.23 no.3 s.99
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• pp.337-345
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• 2007

The physiological and sensory properties of breads made from waxy black rice flour (WBRF) and wheat flour were investigated. The waxy black rice bread was manufactured with 10, 20, 30, or 40% waxy black rice flour(w/w). The bread volume decreased from 2,096.7 mL to 1,703.4 mL as the WBRF content increased from 0% to 40%. The lightness(L-values) decreased with increasing WBRF concentrations, and the redness value(a-values) increased. The yellowness(b-values) slightly decreased with increasing WBRF content. The textural characteristics of the bread c겨mb were influenced by additions of WBRF. The breads containing WBRF had decreases in hardness for the 10% and 20% WBRF groups, whereas increases in hardness were shown with the 40% addition of WBRF. The springiness decreased with increasing WBRF content. The gumminess and chewiness of the waxy black rice bread decreased at the 10% and 20% additions. In the sensory evaluation, sensory scores decreased with increasing WBRF content for the appearance, external color, crumb color and grain of the waxy black rice bread. Overall acceptability for the 10% and 20% WBRF additions did not differ significantly from the score of the control group.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.632-635
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• 2011

Additions (ZnO, CuO) doped $0.98(Na_{0.5}K_{0.5})NbO_3-0.02Li(Sb_{0.17}Ta_{0.83})O_3$ (0.98NKN-0.02LST-x) lead free piezoelectric ceramics have been fabricated by ordinary sintering technique. The effects of additions doping on the dielectric, piezoelectric, and ferroelectric properties of the ceramics were mainly investigated. X-ray diffraction of the sample appeared orthorhombic phase. The specimen doped with additions exhibits enhanced electrical properties ($d_{33}$= 153 pC/N). These results indicate that the 0.98NKN-0.02LST-x ceramics is a promising candidate for lead-free piezoelectric ceramics for applications such as piezoelectric actuators, harmonic oscillator and so on.

• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.234-238
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• 1996

Second-order rate constants have been measured spectrophotometrically for the reaction of p-nitrophenyl acetate (PNPA) with morpholine, piperazine and piperidine in MeCN-H2O mixtures of varying compositions. The rate of the present aminolysis decreases upon additions of MeCN into H2O up to near 30-40 mole % MeCN and remains nearly constant upon further additions of MeCN. The reaction of PNPA with anionic nucleophiles, such as HO-, p-chlorophenoxide and butane-2,3-dione monoximate, has also exhibited two distinguishable reactivity zones. However, the reactivity trend for the anionic nucleophiles is quite different from the one obtained for the amine system, e.g. an initial rate decrease in the H2O-rich region followed by an increasing rate trend upon further additions of MeCN in the MeCN-rich region. The rate behaviors shown by the amine system in the MeCN-rich and by the anionic system in the H2O-rich region are unexpected based on the Hughes-Ingold rules. The present unusual rate trends have been attributed to changes in the solvent structure and pKa of the nucleophiles upon the addition of MeCN into H2O. The effect of solvent appears to be more significant for the TS than the GS, and the TS structure is considered to become tighter in the higher MeCN concentration.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.121-131
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• 2006

The strength standard of shotcrete in Korea is relatively lower than that in Europe where high-strength shotcrete has been developed and actively applied to the common practice, so it is hard to test a quality of high-strength shotcrete. In this study, field test was performed to find a solution improving the strength and a long-term durability on domestic shotcrete. In field test, a high-strength shotcrete was produced using high-quality additions and accelerators, and an effect of additions and accelerators was observed. In addition, quality test based on EFNARC was also performed. As a result of field test, a promotion ratio of early strength is 90~97% in case of using alkali-free accelerators, therefore, alkali-free accelerators had an effect on an increase of early strength on shotcrete. A compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. It was showed that increment effect of strength by the silica fume replacement of 7.5~10% for cement mass was remarkable. As a result of test, it was possible to apply high-strength shotcrete to the domestic practice using high-quality additions such as Micro-silica fume and accelerators such as alkali-free.

• 수도
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• s.18
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• pp.4-11
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• 1979