• Biotechnology and Bioprocess Engineering:BBE
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• 제3권2호
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• pp.103-108
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• 1998

A hydrophobic substrate triolein was hydrolyzed by lipase in a mono-phase reaction system containing cyclodextrin(CD) as emulsifier. The triolein was transformation to an emulsion-like state in the CD containing reaction system in contrast to the oil-droplet like state without CD due to the formation of an inclusion complex between the lipids and CDs. The hydyrolysis reaction increased substantially in the CD containing reaction system, and the optimum reaction conditions including the amount of lipase, ${\beta}$-CD concentration, and mixing ratio of triolein and ${\beta}$-CD, were determined. The performance of the enzyme reaction in a mono-phase reaction system was compared with that of a two-phase reaction system which used water immiscible hexane as the organic solvent. The role of a CD in the mono-phase reaction system was elucidated by comparing the degree of the inclusion complex formation with triolein and oleic acid, Km and Vmax values, and product inhibition by oleic aicd in aqueous and CD containing reaction systems. The resulting enhanced reaction seems to be caused by two phenomena; the increased accessibility of lipase to triolein and reduced product inhibition by oleic acid through the formation of an inclusion complex.

• 한국재료학회지
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• 제23권4호
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• pp.246-249
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• 2013

Nano-sized ${\beta}$-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. $SiO_2$ nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. $SiO_2$ and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at $80^{\circ}C$ in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at $1400{\sim}1500^{\circ}C$ for 4 h with a heating rate of $10^{\circ}C$/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.

• 한국재료학회지
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• 제27권4호
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• pp.179-183
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• 2017

$2ZrO_2{\cdot}P_2O_5$ powder, which is not synthesized by solid reaction method, was successfully synthesized through PVA solution method. In this process, the firing temperature and the PVA content strongly affected the crystallization behavior and final particle size. A stable ${\alpha}$-phase $2ZrO_2{\cdot}P_2O_5$ was synthesized at a firing temperature of $1200^{\circ}C$ and holding time of 4 h. ${\beta}$-phase $2ZrO_2{\cdot}P_2O_5$ was observed, with un-reacted $ZrO_2$ phases, for firing temperatures lower than $1200^{\circ}C$. In terms of the PVA content effect, the powder prepared with a PVA mixing ratio of 12:1 showed stable ${\alpha}$-phase $2ZrO_2{\cdot}P_2O_5$; however, the ${\beta}$-phase was found to co-exist at relatively higher PVA content. The synthesized ${\alpha}$-phase $2ZrO_2{\cdot}P_2O_5$ powder showed an average particle size of 100~250 nm and an average thermal expansion coefficient of $-2.5{\times}10^{-6}/^{\circ}C$ in the range of room temp. ${\sim}800^{\circ}C$.

• 한국잠사곤충학회지
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• 제46권1호
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• pp.28-31
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• 2004

견피브로인의 응용가능성을 높이기 위하여 대표적인 생체고분자인 히아론산을 이용하여 견피브로인/히아론산 브렌드 필름을 제조하였으며 구조 및 열 특성을 살펴보았다. 1. 적외선 분광분석 결과 견피브로인과 히아론산 두 고분자 사이에는 수소결합 등의 상호작용이 존재하지 않는 것으로 나타났다. 또한 브렌드 필름내에 존재하는 실크피브로인은 EDC 에탄올 용액처리에 의하여 $\beta$-sheet 구조로 전이되었다. 2. 견피브로인/히아론산 브렌드 필름에서 견피브로인과 히아론산 각각의 열분해 흡열피크와 발열피크 온도에는 큰 변화가 없었으나, 열분해 피크의 폭이 넓어지는 것으로 봐서 실크 피브로인과의 브렌드 또는 EDC 처리에 의하여 열분해 반응이 매우 복잡한 환경하에서 진행되고 있음을 알 수 있었다. 3 견피브로인/히아로산 브렌드 필름은 자기 중량 대비 평균 70배의 수분을 흡수하였다.

• 한국식품저장유통학회지
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• 제24권8호
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• pp.1158-1167
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• 2017

본 연구에서는 LP-BM5 murine AIDS virus에 감염된 면역 결핍동물 모델을 이용하여 실험기간 10주 동안 ${\beta}$-1,3/1,6-glucan, 유산균 및 ${\beta}$-1,3/1,6-glucan+유산균의 식이가 면역활성에 미치는 영향을 조사하였다. 그 결과 LP-BM5 murine AIDS virus에 감염으로 면역능이 떨어진 T세포 증식능은 홍삼대조군과 비교하여도 유의적으로 감소된 T 세포증식능을 증가시키는 것으로 나타났고, B 세포 증식능은 감염 대조군에 비하여 유의적으로 증가된 B 세포 증식능을 감소되었다. cytokine 생성능에서는 Th1 type cytokine중에서 IL-2, IL-12, IL-15는 감염대조군에 비하여 분비량을 증가시키는 것을 확인할 수 있었고, IFN-${\gamma}$는 유산균과 ${\beta}$-1,3/1,6-glucan을 각각 처리군이 혼합처리군보다 증식능이 증가하였다. TNF-${\alpha}$는 감염대조군에 비하여 유의적으로 감소하였다. Th2 cytokine 들의 분비량 측정에서 IL-4, IL-6, IL-10 측정 결과 감염대조군에서 유의적으로 억제되어 Th1/Th2 type cytokine 발현을 조절하여 면역항상성을 유지하는 것으로 보였다. 면역글로블린 분비량측정에서 IgE, IgA, IgG 모두 감염대조군에 비하여 유의적으로 떨어지는 것으로 나타났다. 이로서LP-BM5 murine AIDS virus에 감염된 면역 결핍동물 모델에 ${\beta}$-1,3/1,6-glucan+유산균군을 혼합처리로 면역조절의 효능이 있음을 확인할 수 있었다.

• 한국식품조리과학회지
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• 제9권3호
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• pp.181-186
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• 1993

Potato and carrot are the main sourses of vitamin C and vitamin A each. As a folk ramedy, potato-carrot mixtures have been used to cure a stomach ulcer in Korea. To investigate the effects of carrot juice on the browning of potato juice, we examined the brewing in various ratio of two juices. We also investigated the role of potato juice in the carotene oxidation of carrot juice. Delta "L" values of potato juice were abruptly decreased after 5 min. reaction and they were very different from the juice mixture of potato and carrot. Those containing higher ratio of potato were decreased greatly. In blanching treatment to eliminate the effect of the enzymes in potato and carrot, delta "L" values of cooked potato were decreased a little but those of cooked carrot were decreased greatly. To investigate the fact that the inhibitory effect of carrot juice in potato browning was due to the dilution of polyphenolics of potato juices by carrot juice mixing, we added H20 equivalent to carrot water content to potato juice. The diluted sample showed less decreasing pattern than nondiluted sample. We also added appropriate amount of ${\beta}$-carotene to the same samples. Delta "L" values of with added B-carotene were more slowly decreased than those of without added B-carotene.

• Tribology and Lubricants
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• 제15권1호
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• pp.8-16
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size : 18$\pm$1 ${\mu}{\textrm}{m}$) was investigated on the elevated temperature up to 10$0^{\circ}C$. For development of anhydrous ER fluids using at wide temperature range, it should be researched to how the effect of temperature on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were made from the phosphoric ester reaction of cellulose were measured. As increasing the temperature, not only the analysis of electrical properties such as dielectric constant current density and electrical conductivity but also the rheological properties of ER fluids were studied. From the experimental results, the temperature had a large influence to the ER properties of anhydrous ER fluids. The current density, conductivity and elecoorheological effect ($\tau$$_{A}$$\tau$$_{0}$) of phosphoric ester cellulose ER fluids were proportional to the temperature with power law. And the shear stress of them was closely related with the square of dielectric constant mismatch parameter ($\beta$$^2$) under constant shear rate and electric field.d.

• 한국분말재료학회지
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• 제14권1호
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• pp.38-43
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• 2007

Cu-Zn alloy nano powders were fabricated by the electrical explosion of Zn-electroplated Cu wire along with commercial brass wire. The powders exploded from brass wire were composed mainly of ${\alpha},{\beta},\;and\;{\gamma}$ phases while those from electroplated wires contained additional Zn-rich phases as ${\varepsilon}$, and Zn. In case of Zn-elec-troplated Cu wire, the mixing time of the two components during explosion might not be long enough to solidify as the phases of lower Zn content. This along with the high vapor pressure of Zn appears to be the reason for the observed shift of explosion products towards the high-Zn phases in electroplated wire system.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.61-68
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• 1999

The variety of crystalline structure and mechanical properties of PP filament treated with dry heat treatment at different draw ratio has been studied. Crystalline structure and mechanical properties of annealed PP filament at different draw ratio has been examined by XRD, UTM, and density method. Heat treatment has been carried out $100^{\circ}C$, $120^{\circ}C$ $140^{\circ}C$ for 30min. in dry oven. From the results of this study, it found the following facts. It was found that the crystallinity and crystallite size of (110) plane of sample were increased with increasing of annealed temperature and draw ratio. The crystalline form of annealed sample which was undrawn showed ${\alpha}$, ${\beta}$ mixing form below $120^{\circ}C$ and showed ${\alpha}$ form at $140^{\circ}C$. But the crystalline form of annealed sample which was drawn showed ${\alpha}$ form at $120^{\circ}C$. Initial modulus and tensile strength were increased with increasing of annealing temperature, and the degree of orientation was decreased with decreasing of annealing temperature.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.