• 한국세라믹학회지
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• 제44권1호
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• pp.6-11
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• 2007

The rheological properties of slag cement pastes by effect of particle size distribution of binder were investigated using a Rheostress 1 rheometer (Haake) with a cylindrical spindle and the relationship between fluidity particle size distribution using the Rosin-Rammler equation. Samples are combined the two types of slag powder and OPC, fine slag particles sized Elaine specific surface area $8,000cm^2/g$, coarse slag particles sized Elaine specific surface area $2,000cm^2/g$, intermediate OPC particles $3,450cm^2/g$, used to search for the combination that would yield the best quality product. The all flow curves which were measured by rheometer showed hysterisis and could be classified into 4 types. When the combination was based on a ratio of 15-20 vol% fine particles, 40-50 vol% intermediate particles, 30-40 vol% coarse particles of the total volume, a high fluidity and low yield-strength was achieved. The Rosin-Rammler function can explain aboved correlation flow curve types. On type 1, the n-value had a correlation with plastic viscosity however the blend of type 2 and 3 showed consistent n-value regardless of plastic viscosity. In addition, the blend in type 4 tended to a rise in fluidity according to the increase of the n-value.

• 대한토목학회논문집
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• 제13권2호
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• pp.61-71
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• 1993

충돌이나 폭파시 발생하는 기계적 에너지나 화학적 에너지는 응력파의 형태로 매체를 통과하게 되며, 매체의 자유면과 절리면을 따라 반사와 굴절을 거듭하는 매우 복잡한 과정을 거치게 된다. 본 연구에서는 재료특성을 달리하는 층을 통과하는 소성응력파의 전파과정을 압력 부종속 모델인 Von-Mises 모델을 사용하여 연구하였다. 응력파의 전파과정을 연구하기 위한 지배 방정식(governing equation)으로서는 물체에 종속되어 있는 라그란지안 좌표계(lagrangian coordinate system)로 표현된 운동량과 질량보존(conservation of momentum and mass)법칙식을 사용하였으며 또한 충격전면(shock front)에 연속성을 부여하기 위해 인공점성(artificial viscosity)을 운동량 보존식에 첨가하였다. 주요 방정식을 풀기 위한 수치해석법으로는 시간과 공간 좌표계로 구성된 유한차분법(finite difference method)을 사용하였으며 소성변형률을 구하기 위한 소성이론으로서는 associated normality flow rule을 사용하였다.

• 한국식품조리과학회지
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• 제30권2호
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• pp.129-138
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• 2014

This research aimed to develope squash sikhye containing retrograded rice flour using response surface methodology. For this, nonlinear regression equation was calculated with the setting of independent variables as retrograded rice flour containing resistant starch and squash, and dependent variables as viscosity, sugar content, pH, color, and sensory attributes. Under the experimental condition, the quality characteristics of squash sikhye were found as 6.20~6.25 for pH, $14.00{\sim}17.33^{\circ}Brix$ for sweetness, 2.64~4.45 cP for viscosity, 57.51~60.18 for lightness, 4.94~7.52 for redness, and 50.98~60.29 for yellowness. It also was revealed overall acceptability in sensory evaluation rated as 9.67~10.83 out of 15 point. These results showed statistically significant differences in quality attributes with the increase of retrograded rice flour and squash(p<0.05). Thus, optimal mixing quantity of squash and retrograded rice flour for squash sikhye was identified as 114 g and 65 g, respectively. Comparison of sensory qualities of four samples, namely squash sikhye with and without retrograded rice, and two commercial products, showed that squash sikhye including retrograded rice flour had the best quality in terms of color, taste, mouth feeling, flavor and overall acceptability (p<0.05). Thus the squash sikhye with retrograded rice flour can be the potential products as a health benefit beverage for the old adult and the young generation.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2523-2528
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• 2014

In the present study, at first, azo Schiff base ligand of (N,N'-bis(5-phenylazosalicylaldehyde)-ethylenediamine) ($H_2L$) has been synthesized by condensation reaction of 5-phenylazosalicylaldehyde and ethylenediamine in 2:1 molar ratio, respectively. Then, its cobalt complex (CoL) was synthesized by reaction of $Co(OAc)_2{\cdot}4H_2O$ with ligand ($H_2L$) in 1:1 molar ratio in ethanol solvent. This ligand and its cobalt complex containing azo functional groups were characterized using elemental analysis, $^1H$-NMR, UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and CoL complex was investigated in 10 mM Tris/HCl buffer solution, pH = 7 using UV-vis absorption, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of CoL complex with ct-DNA was found to be $(2.4{\pm}0.2){\times}10^4M^{-1}$. The thermodynamic parameters were calculated by van't Hoff equation.The enthalpy and entropy changes were $5753.94{\pm}172.66kcal/mol$ and $43.93{\pm}1.18cal/mol{\cdot}K$ at $25^{\circ}C$, respectively. Thermal denaturation experiments represent the increasing of melting temperature of ct-DNA (about $0.93^{\circ}C$) due to binding of CoL complex. The results indicate that the process is entropy-driven and suggest that hydrophobic interactions are the main driving force for the complex formation.

• 대한토목학회논문집
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• 제12권2호
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• pp.21-33
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• 1992

충격하중을 받는 구조물은 초고압에서 부터 저압까지 다양한 압력을 짧은 시간에 경험하게 된다. 따라서 이들 구조물을 해석하기 위해서는 실제 물체의 재료특성을 표현할 수 있는 구성 법칙(constitutive law)이 필요하게 된다. 본 연구에서는 압력 부종속모델(pressure independent model)인 Von-Mises 모델과 압력 종속모델(pressure dependent model)인 Drucker-Prager 모델을 사용하여 충격과 폭발 현상시 발생하는 응력파의 전파과정(propagation process)을 재료특성에 따라 비교 분석하였다. 응력파의 전파과정을 연구하기 위한 지배 방정식(governing equation)으로서는 물체에 종속되어 있는 라그란지안 좌표계(lagrangian coordinate system)로 표현된 운동량과 질량보존(conservation of momentum and mass)법칙을 사용하였으며 또한 충격전면(shock front)에 연속성을 부여하기 위해 인공점성(artificial viscosity)을 운동량 보존식에 첨가하였다. 주요 방정식을 풀기 위한 수치해석법으로는 시간과 공간 좌표계로 구성된 유한차분법(finite difference method)을 사용하였으며 소성변형률을 구하기 위한 소성이론으로서는 Associated normality flow rule을 사용하였다.

• 한국수산과학회지
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• 제48권1호
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• pp.58-63
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• 2015

The chemical and rheological properties of natural and enzymatically hydrolyzed porphyran isolated from Pyropia yezoensis were investigated. The enzymatic hydrolysate was prepared by hydrolysis of porphyran using ${\beta}$-agarase followed by fractionation based on molecular weight (>300 kDa (Fr-1), 100-300 kDa (Fr-2), 10-100 kDa (Fr-3) and 1-10 kDa (Fr-4) using an ultrafiltration membrane. Each hydrolysate fraction consisted mainly of galactose (42.7-57.5%), 3,6-anhydro galactose (6.5-15.1%) and ester sulfate (8.6-14.1%). The sulfate content of the enzymatically hydrolyzed fractions decreased with an increase in molecular weight, whereas the 3,6-anhydro galactose content increased significantly. The rheological behavior of porphyran and enzymatically hydrolyzed porphyran solutions demonstrated a pseudoplastic behavior, which agrees with the Herschel-Bulkley model. The effect of temperature on the viscosity of the porphyrans and hydolysate fractions were measured and modeled using the Arrhenius equation. The activation energy of the porphyrans and enzymatically hydrolyzed porphyran (Fr-1) increased from 12.30 to 20.29 kJ/mol and 9.06 to 23.84 kJ/mol, respectively with increasing concentrations from 3% to 7%. These data indicate that the extent of the apparent viscosity of porphyran and enzymatically hydrolyzed porphyran are influenced by both temperature and concentration.

• 한국염색가공학회지
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• 제22권3호
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• pp.187-193
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• 2010

The effects of molecular weight (MW) and concentration on the rheological properties of poly(vinyl alcohol) (PVA) solutions in dimethyl sulfoxide (DMSO) were investigated at $30^{\circ}C$. Ubbelohde viscometer and rotational rheometer were employed for dilute and concentrated regime, respectively. In the dilute regime, the Mark-Houwink exponent ($\alpha$) of the solutions determined from three different MWs proved 0.73. The critical concentration (C*), in which the entanglement and overlap of polymer molecules began to take place, decreased with increasing the MW of PVA. Huggins constant ($K_H$) values ranged from 0.33 to 0.45 over the MW examined. In the log-log plot of $\eta_{sp}$ versus [$\eta$]C, the PVA with higher degree of polymerization (DP) gave a greater slope exhibiting the inflection point in the vicinity of C*. In the dynamic viscosity ($\eta'$) curve, the PVA solutions of DP 1700 presented Newtonian fluid behavior over most of the frequency range examined. However, the lower Newtonian flow region reduced with increasing the DP. As the PVA concentration increased, $\eta'$ was increased and the onset shear rate for pseudoplasticity was decreased. In the Cole-Cole plot, PVA solutions showed almost a single master curve in a slope of ca. 1.65 regardless of the DP. However, the increase of the concentration from 8 to 12 wt% for PVA solutions of DP 5000 decreased the slope from 1.73 to 1.57. In the tan $\delta$ curve, the onset frequency for sol-gel transition was shifted from 154 to 92 rad/s with increasing the DP from 3300 to 5000 and from 192 to 46 rad/s with increasing the concentration from 8 to 12 wt%. In addition, longer relaxation time ($\lambda$) was observed with increasing the DP and concentration.

• 한국식품과학회지
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• 제22권6호
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• pp.646-650
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• 1990

마늘의 장기저장 및 새로운 향신료 개발의 일환으로 마늘을 착즙한 후 농축시켜 저장 및 중간 향신 소재화 하고자 하였으며, 그 연구의 일환으로 마늘 착즙 및 그 농축액의 rheological properties에 대해 연구하였다. 마늘 착즙 및 농축액의 흐름거동은 고형물 농도$50^{\circ}Brix$까지는 power-law model에 대체로 잘 적용되었으나 $60^{\circ}Brix$ 이상의 농도에서는 항복응력을 고려한 Herschel-Bulkley model이 더 적절한 것으로 여겨졌으며, 의가소성 유체(pseudoplastic fluid)의 특성을 나타내었다. 고형물 농도 $32{\sim}60^{\circ}Brix$, 온도 $15{\sim}65^{\circ}C$의 범위에서 유동지수는 $0.6130{\sim}0.9937$로 온도가 상승할 수록 증가하였으며, 이 때 점조도지수는 $3.1886{\sim}0.0041Pa\;s^n$였다. 마늘 착즙의 겉보기점도는 전단속도의 증가에 따라 직선적으로 감소하였으며 유동에 따른 활성화에너지는 $11,216{\sim}23,195\;kJ/kg\;mol$이었다.

• Carbon letters
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• 제11권1호
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• pp.22-27
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• 2010

The precipitation polymerization of acrylonitrile (AN) was carried out in a mixture solution of dimethyl sulfoxide (DMSO) and water at $50{\sim}65^{\circ}C$ using ${\alpha},{\alpha}'$-azobisisobutyronitrile (AIBN) as an initiator. The increased molecular weight polyacrylonitrile (PAN) was prepared with increasing the $H_2O$/DMSO ratio from 10/90 to 80/20. The viscosity average molecular weight of $H_2O$/DMSO solvent was 4.4 times larger than that of $H_2O$/DMF solvent, and precipitation polymerization was accelerlated due to the far decreased chain transfer effect of DMSO. Based on the experimental results, the increased PAN molecular weight was regarded as the summation of two mechanisms: i) particle-particle aggregation and ii) particle-radical attachment. The theoretical equation derived from the mechanisms was well coincided with the experimental results showing the linear relationship between the viscosity average molecular weight and the H2O/DMSO ratio.

• 한국식품과학회지
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• 제33권2호
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• pp.221-225
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• 2001

꽃양배추색소추출액의 농도를 1-65%로 조절하여 그 유동 특성을 원뿔형 회전점도계를 사용하여 $20-50^{\circ}C$의 온도범위에서 조사하였다. 꽃양배추색소추출액의 유동특성은 단순 power law model을 사용하여 설명할 수 있었다. 실험범위 내에서 꽃양배추색소추출액의 유동거동지수(n)와 점조도지수(K)는 각각 0.841-0.998 및 $0.008-31.525\;Pa{\cdot}s^n$의 값을 나타냈다. 겉보기점도의 온도의존성은 Arrhenius식에 의해 결정할 수 있었으며, 활성화에너지는 용액의 농도와 전단속도에 따라 9.36-52.48 kJ/mol의 값을 나타냈다. 전단속도 $100\;s^{-1}$에서 측정한 보기점도에 대한 용액의 농도와 온도의 영향을 다음과 같은 단일지수모델식으로 표시할 수 있었다; ${\ln}\;{\eta}_a\;=\;6.11\;-\;3103.94(1/T)\;-\;0.03C$.