• Korean Journal of Food Science and Technology
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• v.33 no.1
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• pp.19-23
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• 2001

Physicochemical properties including viscosity, temperature and pH stability, color turbidity and moisture retention power of xylooligosaccharide(XO) as food material were investigated to apply to food process. The viscosity of 70 bx XO was 930 cP at $20^{\circ}C$ and 90 cP at $60^{\circ}C$, which was higher than that of sugar but lower than that of other oligosacchrides. XO remained stable after heat treatment for 1hr at $100^{\circ}C$ and pH 2.5 to 8.0 indicating excellent heat and pH stability. The pH of XO was measured $5.0{\pm}0.1$ and the color turbidvity of XO was very low at pH $2.5{\sim}4.0$. The color turbidity of XO increased as pH increased, but it was not high enough to affect food process. When heated with 1% glycine the color turbidity of XO was very low and changed little with pH changes. To measure moisture retention power XO was stored at $25^{\circ}C$ and 75% relative humidity for 71 day. XO retained more than 95% of the original weight; whereas sugar lost 28%. These results suggest that XO has useful physicochemical properties for various food process to improve the functionality of food.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.4
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• pp.166-171
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• 2015

In this study, using solid-state and flux, $Y_3Al_5O_{12}:Er^{3+}\;(YAG:Er^{3+})$ powders were successfully synthesized at low temperatures. To analyze the crystallinity of powders according to the synthesis or non-synthesis of powders and powder calcination temperatures, X-ray diffraction (XRD) was measured. In the case of pure YAG, when YAG was analyzed using the general solid-phase method, it was calcined for 12 hours at $1400^{\circ}C$ and pure YAG phase could be obtained. But when $BaF_2$ was added to YAG, YAG was synthesized at lower temperature (1000^{\circ}C$). It was thus found that the synthesis temperature could be lowered by about $400^{\circ}C$. Also, when BaF2 with an optimal concentration was added to $YAG:Er^{3+}$, the particle shape and size according to synthesis temperatures were surveyed, and corresponding luminous intensity was discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.2
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• pp.92-98
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• 2012

The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$, TEOS and $Mg(NO_3)_2{\cdot}6H_2O$ as the starting materials was used. After the heat treatment of powder crystalline phases HAp and ${\beta}$-TCP analysis showed a mixed phase. The overall spectra appear to have mainly two modes corresponding to characteristic $PO^{3-}_4$ and $OH^-$ groups. After immersion in Hanks' Balanced Salt Solution (HBSS) for 1 week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that ionic substituted BCP powders had no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.786-789
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• 2011

In order to estimate the possibility of applying electrolytes generally used in solid oxide fuel cells(SOFCs) to direct carbon fuel cells(DCFCs), properties of YSZ(yttria stabilized zirconia) electrolyte were evaluated. In this study, vacuum slurry coating method was adapted to coat thin layer on anode support substrate. After sintering the electrolyte at $1400^{\circ}C$ for 5hrs, microstructure was analyzed by using SEM image. Also, gas permeability and ionic conductivity were measured to find out the potential possibility of electrolyte for DCFCs. The YSZ electrolyte represented dense coating layer and low gas permeability value. The ionic conductivity of YSZ electrolyte was high over $800^{\circ}C$. After measurement of the electrolyte properties, direct carbon fuel cell was fabricated and its performance was measured at $800^{\circ}C$.

• KSBB Journal
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• v.24 no.2
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• pp.163-169
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• 2009

Lovastatin (also known as Mevinolin, Mevacor, and Monacolin K), an inhibitor of the HMG-CoA reductase produced by Aspergillus terreus and other fungi, is used to reduce serum cholesterol levels in human beings. It is derived biosynthetically from two polyketides. One of these is a nonaketide that undergoes cyclization at a hexahydronaphthalene ring system, and the other is a simple diketide, 2-methylbutyrate. Two primer pairs were designed based on the amino acid sequences of lovastatin polyketide synthase and lovastatin diketide synthase for the PCR screening of lovastatin-producing strains. Among the seven selected strains, SJ-2 evidenced the highest level of lovastatin production in both liquid and solid cultures. Soybeans with SJ-2 were treated via 1 hour of heat shock at $30^{\circ}C$ for the mass production of lovastatin. The heat-treated soybeans were inoculated on rice bran and the koji extract was obtained after 15 days of incubation. It yielded the highest level of lovastatin production among the strains, and also evidenced 75% inhibition activity against HMG-CoA reductase. We developed an efficient PCR screening method for lovastatin-producing strains, using lovastatin biosynthesis genes.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.328-334
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• 2007

Chemical heat pump system of 2-propanol/acetone/hydrogen is most suitable to the recovery of waste heat of power plant. various types of 5 wt% Pt-alumina catalysts were prepared for 2-propanol dehydrogenation using sol-gel method. The characteristics and the dehydrogenation reaction rate of each catalyst were investigated. Pt-alumina xerogel catalyst has excellent reaction rate and good durability in comparison with the existing alumina supported Pt catalysts. Pt-alumina aerogel catalyst had the highest reaction rate in all prepared catalysts, but sufficient aging time was necessary to maintain its reaction rate. A potential advantage of the aerogel catalyst is the fact that the high temperature heat treatment is not required. Without heat treatment or with low temperature heat treatment, the Pt-alumina aerogel catalyst has excellent reaction rate as well as durability and this gives us the economic advantage. Alumina xerogel supported Pt catalyst prepared by incipient wetness method showed good reaction rate, and had good mechanical strength. Blank alumina xerogel prepared by sol-gel method can be used for the support of metal catalysts.

• Journal of Life Science
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• v.27 no.9
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• pp.1003-1010
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• 2017

An open reading frame coding for mannanase predicted from the partial genomic sequence of Paenibacillus woosongensis was cloned into Escherichia coli by polymerase chain reaction amplification, and completely sequenced. This mannanase gene, designated man26AT, consisted of 3,162 nucleotides encoding a polypeptide of 1,053 amino acid residues. Based on the deduced amino acid sequence, Man26AT was identified as a modular enzyme, which included a catalytic domain belonging to the glycosyl hydrolase family 26 and two carbohydrate-binding modules, CBM27 and CBM11. The amino acid sequence of Man26AT was homologous to that of several putative mannanases, with identity of 81% for P. ihumii and identity of less than 57% for other strains of Paenibacillus. A cell-free extract of recombinant E. coli carrying the man26AT gene showed maximal mannanase activity at $55^{\circ}C$ and pH 5.5. The enzyme retained above 80% of maximal activity after preincubation for 1 h at $50^{\circ}C$. Man26AT was comparably active on locust bean gum (LBG), galactomanan, and kojac glucomannan, whereas it did not exhibit activity on carboxymethylcellulose, xylan, or para-nitrophenyl-${\beta}$-mannopyranoside. The common end products liberated from mannooligosaccharides, including mannotriose, mannotetraose, mannopentaose, and mannohexaose, or LBG by Man26AT were mannose, mannobiose, and mannotriose. Mannooligosacchrides larger than mannotriose were found in enzymatic hydrolyzates of LBG and guar gum, respectively. However, Man26AT was unable to hydrolyze mannobiose. Man26AT was intracellularly degraded into at least three active proteins with different molecular masses by zymogram.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.890-897
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• 1998

The direct wafer bonding between n-InP(001) wafer and the ${Si}_3N_4$(200 nm) film grown on the InP wafer by PECVD method was investigated. The surface states of InP wafer and ${Si}_3N_4$/InP which strongly depend upon the direct wafer bonding strength between them when they are brought into contact, were characterized by the contact angle measurement technique and atomic force microscopy. When InP wafer was etched by $50{\%}$ HF, contact angle was $5^{\circ}$ and RMS roughness was $1.54{\AA}$. When ${Si}_3N_4$ was etched by ammonia solution, RMS roughness was $3.11{\AA}$. The considerable amount of initial bonding strength between InP wafer and ${Si}_3N_4$/InP was observed when the two wafer was contacted after the etching process by $50{\%}$ HF and ammonia solution respectively. The bonded specimen was heat treated in $H^2$ or $N^2$, ambient at the temperature of $580^{\circ}C$-$680^{\circ}C$ for lhr. The bonding state was confirmed by SAT(Scannig Acoustic Tomography). The bonding strength was measured by shear force measurement of ${Si}_3N_4$/InP to InP wafer increased up to the same level of PECVD interface. The direct wafer bonding interface and ${Si}_3N_4$/InP PECVD interface were chracterized by TEM and AES.

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.27-32
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• 2011

The electorchemical properties of $Li_4Ti_5O_{12}$ added with Cr was tested. The addition or substitution of atoms to $Li_4Ti_5O_{12}$ are expected to modify the crystal structure, and therefore to change the electrochemical performances of $Li_4Ti_5O_{12}$. After the spinel structure $Li_4Ti_{5-x}Cr_xO_{12}$ (x = 0~0.2) were obtained via sol-gel method, the gel was heated in a muffle furnace at $800{\sim}850^{\circ}C$ for 12 h in air. The physical properties of the samples were characterized by TG-DTA, XRD, SEM, FT-IR, and the electrochemical properties were tested with battery cycler at 0.01~2.0 V range. The $Li_4Ti_5O_{12}$ exhibited 169.9 mAh/g at 1C and capacity recovery was 97.5% of the initial capacity at 0.1C. $Li_4Ti_{4.9}Cr_{0.1}O_{12}$ (Cr 1% added) showed best performance of 193.8 mAh/g at 1C and the capacity recovery was increased to 98.8% of the initial capacity at 0.1C.