• 한국세라믹학회지
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• 제32권10호
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• pp.1147-1161
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• 1995

When ceramic membrance was made from metal salt solution in place of metal akoxide solution, crack free and good adhesion to supporter was optimized for sol stability and good adhesion force. A starting sol was prepared from aluminum oxychloride aqueous solutjion in order to inhibit the grain growthof Al2O3 during heat treatment. The crack free dip coating can't be achieved in 1mol/ι zirconium oxychloride solution because of the high viscosity which interferes with the hydration copolymerization between Al3+ ion and Zr4+ ion. Thus Al2O3-ZrO2 sol stability and viscosity for dip coating was effective when 0.01 mol/ι zirconium oxychloride was added. The minimizing of crack and achieving better adhesion to the supporter wa obtained by microwave drying, surfactant addition and ultrasonic dip coating in wet atmosphere. The result seems to minimize the capillary force and improve the adhesive ability to supporter during the process. Where the average pore size of Al2O3-ZrO2 ultrafilter ceramic membrane measured 17 Å by the BET method and observed γ-Al2O3 phase with tetragonal zirconia after firing at 700℃.

• Membrane and Water Treatment
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• 제4권4호
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• pp.277-291
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• 2013

The transport and recovery of Levafix brilliant red E-4BA and Levafix brilliant red E-6BA were investigated using polytetrafluoroethylene (PTFE) fiber based supported liquid membrane containing tetra butyl ammonium bromide (TBAB) in coconut oil as a carrier. The influencing parameters studied are: pH of the feed solution, concentration of dye in the feed solution, extractant concentration, and various kind of stripping agent, rate of stirring, time of transport, reusability of membrane and stability of membrane. Increase in TBAB concentration inside the membrane enhances the flux with its maximum value at $1.553{\times}10^{-4}$ M TBAB. Further increase in the concentration of TBAB leads to decreased rate of transport due to increase in viscosity of membrane liquid. The optimum conditions for dye transport are: pH of feed ($7{\pm}0.1$), $1.553{\times}10^{-4}$ M extractant concentration, 350 rpm for stirring, $4.9{\times}10^{-1}$ M potassium hydrogen phthalate as a stripping solution, the time of transport 6 h. It was noticed that flux values were increased with increasing dye concentration in the feed phase. Applying this study to textile wastewater, dyes were transported up to 98% in 6 h. This recovery technique is rewarding to environment and economic.

• 한국초전도ㆍ저온공학회논문지
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• 제13권4호
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• pp.22-25
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• 2011

A single-coat $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) film of high critical currents ($I_c$) could be successfully fabricated by optimizing the viscosity of the coating solution in the metal-organic deposition (MOD) process. From a Ba-deficient coating solution (Y: Ba: Cu = 1: 1.5: 3) having the viscosity of 212 $mPa{\cdot}sec$, 0.9 ${\mu}m$-thick single coat YBCO film with the $I_c$ value of 289 A/cm-width ($J_c$ = 3.2 MA/$cm^2$) at 77 K was achievable on the $SrTiO_3$ (STO) substrate, which was superior to that of our previous report for 0.8 ${\mu}m$-thick single coat YBCO film from a stoichiometric coating solution (Y: Ba: Cu = 1: 2: 3) on the $LaAlO_3$ (LAO) substrate. This result might be attributed to denser and more homogeneous microstrcuture in the case of the YBCO film from the Ba-deficient coating solution.

• 한국도로학회논문집
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• 제19권4호
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• pp.19-25
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• 2017

PURPOSES : In this paper, the flow of construction material was simulated using computational fluid dynamics in a 2D axisymmetric condition to evaluate the effect of initial or varying material properties on the final shape of a specimen. METHODS : The CFD model was verified by using a well-known analytical solution for a given test condition followed by performing a sensitivity analysis to evaluate the effect of material properties on the final shape of material. Varying dynamic viscosity and yield stress were also considered. RESULTS : The CFD model in a 2D axisymmetric condition agreed with the analytical solution for most yield stress conditions. Minor disagreements observed at high yield stress conditions indicate improper application of the pure shear assumption for the given material behavior. It was also observed that the variation of yield stress and dynamic viscosity during curing had a meaningful effect on the final shape of the specimen. CONCLUSIONS : It is concluded that CFD modeling in a 2D axisymmetric condition is good enough to evaluate fluidal characteristics of material. The model is able to consider varying yield stress and viscosity during curing. The 3D CFD-DEM coupled model may be required to consider the interaction of aggregates in fluid.

• 한국식품저장유통학회지
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• 제8권1호
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• pp.102-108
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• 2001

자색고구마 색소 농축액의 유동특성을 원뿔형 회전점도계를 사용하여 가용성 고형분의 농도 25-65% 및 온도 20-6$0^{\circ}C$의 범위에서 조사하였다. 자색고구마 색소 농축액은 뉴톤성유체의 특성을 나타냈다. 자색고구마 색소 농축액의 점도의 온도에 대한 영향은 Arrhenius 식을 따랐으며, 활성화에너지는 14.23-43.00 kJ/mol로서 농도가 증가함에 따라 직선적으로 증가하였다. 자색고구마 색소 농축액의 점도와 온도 및 농도에 대한 관계를 조사한 바, 일정한 온도에서 용액의 점도는 농도가 증가함에 따라 지수함수적으로 증가하였으며, 그 증가 정도는 온도가 낮을수록 증가하였다.

• Preventive Nutrition and Food Science
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• 제2권1호
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• pp.1-5
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• 1997

Solution Properties of polyelectrolytic biopolymers such as chitosen, pectin, alginate and etc. are significantly influenced by molecular weight and salt concentrations. The effect of NaCI concentration on the hydrodynamic properties of chitosan in dilute region was investigated for chitosans of varying molecular weight. Intrinsic vicosity([η]) of citosans with 5 different molecular weight was determined by glass capillary viscometer, and the viscosity average molecular weight was calculated using Mark-Houwink equation. Intrinsic viscosity decreased with increasing NaCI concentration for all chitosan samples, and it was proportional to the logarithmic NaCI concentration, i.e.,[η]∝log{TEX}$(C_{NaCl})^{$\alpha$}${/TEX}. Decreasing trend of[η] with NaCI concentration became more pronounced with increasing molecular weight. It was also found that the a values, indicating {TEX}$C_{NaCl}${/TEX} dependence of[η], were linearly correlated with the logarithmic molecular weight({TEX}$R^{2}${/TEX}=0.980). The chain stiffness parameters(B) were calculated by B=S./{TEX}$([η]_{0.1})^{1.32}${/TEX}, in which S was obtained from slope of [η] va {TEX}$I^{-1/2}${/TEX}. The B values of chitosan samples were determined to be 0.113~0071 with a average of 0.09.

• 한국식품과학회지
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• 제21권3호
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• pp.453-459
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• 1989

산업용 다당류의 개발을 목적으로 고점도의 다당류생산 미생물을 토양으로부터 분리하였다. 본 세균은 동정한 결과 Pseudomonas mendocina로 생각되었다. 본 세균이 생산하는 다당류는 o-acetyl기를 함유한 ${\beta}-glucan$으로 추정되며 구성당으로서는 포도당과 람노오스가 몰비로 2.2 : 1.0 구성으로 되어 있고 수용액은 의가소성 유체이다. 1% 용액은 428mPa.s의 점도를 나타내며 항복치는 8.89Pa이다. 이 용액은 열안정성은 없으며 pH 안정성과 염안정성은 있었다. 유동활성화에너지는 6.57 Kcal 이다.

• 한국식품조리과학회지
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• 제27권6호
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• pp.671-680
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• 2011

In this study, frying mix was prepared containing 0.5, 1.0, 1.5 or 2.0% brown rice fiber(BRF). The samples along with a control were then compared regarding their quality characteristics, including pasting properties, spreadability, pick-up ratio, color, textural characteristics, moisture and oil contents, and sensory qualities, all to determine the optimal ratio of BRF. For the pasting properties of frying mix, the control group was evidenced by a significantly higher peak viscosity, through viscosity, and final viscosity than that observed in the BRF samples. Breakdown was the highest at the 1.0% addition level, and time to peak viscosity and pasting temperature were maximal with the 0.5% addition. There was no significant difference in setback among the experiments. Spreadability and pick-up ratio of frying batter were not significantly different among the samples. As the BRF content increased, the lightness, greenness decreased, whereas yellowness increased. The BRF samples presented significantly higher hardness of fried batter than the control group and there was no significant difference in crispiness among the samples. Moisture content of fried sweet potato decreased with increasing BRF and oil content was the maximum on the control group. In the sensory evaluation, appearance, color, flavor, savory taste, yellowishness, coating thickness, off-flavor, and oiliness were not significantly different among the fried sweet potato samples. Bindingness, crispiness, and chewiness were highest in the control samples but minimal at a addition level of 2.0%. The control group evidenced significantly higher overall acceptability than were observed in the BRF samples. In conclusion, the results demonstrated that 0.5~1.0% BRF may prove quite useful as a additive for frying mix in the preparation of fried sweet potato and may provide favorable textural and functional properties.

• International Journal of Industrial Entomology and Biomaterials
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• 제27권1호
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• pp.180-184
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• 2013

Recently, silk sericin has attracted the attention of researchers owing to its useful properties as a biomaterial including 1) good wound healing and cell activities, 2) fast gelation character, and 3) high water retention property. In the present study, silk sericin was prepared using different extraction times in hot water and the effect of extraction time on the rheological properties of sericin solutions and gels was examined. It was found that the production yield of sericin increased with extraction time. The shear viscosity of sericin solutions and gels decreased with increasing extraction time due to a decrease in sericin molecular weight. When the sericin solution transformed to a gel, the viscosity increased and the shear thinning behavior was more evident. In addition, the shear stress measurements indicated that the slip between the sericin samples and the measuring plate of the rheometer was increased by the gelation of sericin. The compression strength of sericin gel could be increased remarkably (by more than 100 fold) by preparation using the freezing and thawing method.

• Membrane and Water Treatment
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• 제9권1호
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• pp.1-7
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• 2018

The principal objective of this study is to investigate the effect of Polyethylene Glycol (PEG) crosslinking in Polyvinylidene Fluoride (PVDF) in immobilization of Fe and bimetallic Fe/Cu and Cu/Fe zero valent particles on the membrane and its efficiency on removal of nitrate in wastewater. PVDF/PEG polymer solution of three weight compositions was prepared to manipulate the viscosity of the polymer. PEG crosslinking was indirectly controlled by the viscosity of the polymer solution. In this study, PEG was used as a modifier of PVDF membrane as well as a cross-linker for the immobilization of the zero valent particles. The result demonstrates improvement in immobilization of metallic particles with the increase in crosslinking of PEG. Nitrate removal efficiency increases too.