• Fisheries and Aquatic Sciences
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• 제2권2호
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• pp.149-154
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• 1999

Response Surface Methodology was applied for optimizing the processing parameters of ultrasound treatment in order to produce low-molecular alginate. The use of ultrasound significantly reduced viscosity of alginate solutions. Suggested parameters of ultrasound treatment for maximum reduction of alginate molecular weight were: specific intensity, 115.81 $W/cm^2$ at 20kHz frequency; treatment time, 35.55 min; temperature, $20.08^{\circ}C$; alginate concentration, $2.5\%$. Low-molecular alginate obtained by ultrasound had two peaks on Sepharose CL-6B gel filtration. The viscosities of control, fraction I, and fraction II at $0.1\%$ concentration and $25^{\circ}C$ were 3.07, 1.23, and 0.82cps, respectively. Molecular weights of control, fraction I, and fraction II alginates were 336,500, 70,400, and 52,800 daltons, and their solubilities were 3, 6, and $14\%$, respectively. The lower molecular weight of alginate, the lower the alcohol precipitation and the higher $Ca^{2+}$ ion binding capacities. Heavy metal ion binding capacities of alginates were high in the following order of Pb, Cd, Zn, and Co.

• International Journal of Automotive Technology
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• 제4권2호
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• pp.95-100
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• 2003

Automobile industry has been developed rapidly as a key manufacturing industry in Korea. Meanwhile, air pollution is getting worse noticeably than ever. In the diesel emission, PM (Particulate Matter) and NOx (Nitrogen Oxides) have been exhausted with a great amount and the corresponding emission regulations are getting stringent. In order to develop low emission engines, it is necessary to research on better qualified fuels. Sulfur contained in fuel is transformed to sulfur compound by DOC (Diesel Oxidation Catalyst) and then it causes to the increase of sulfate-laden PM on the surface of catalyst. In this research, ULSD (Ultra Low Sulfur Diesel) is used as a fuel and some experimental results are investigated. ULSD can reduce not only PM but also gas materials because cetane value, flash point, distillation 90%, pour point and viscosity are improved in the process of desulfurization. However, excessively reduced sulfur may cause to decease lubricity of fuel and engine performance in fuel injection system. Therefore, it requires only modest adjusted amount of sulfur can improve engine performance and DOC, as well as decrease of emission.

• Journal of the Korean Wood Science and Technology
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• 제49권2호
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• pp.169-180
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• 2021

Inherent crystalline domains present in low formaldehyde to urea (F/U) molar ratio urea-formaldehyde (UF) resins are responsible for their poor adhesion in wood-based composite panels. To modify the crystallinity of low molar ratio (LMR) UF resins, this study investigates the additional effect of cellulose nanomaterials (CNMs), such as cellulose microfibrils (CMFs), cellulose nanofibrils (CNFs), and TEMPO-oxidized CNFs (TEMPO-CNFs) on the crystallinity of modified LMR UF resins. First, two modification methods (post-mixing and in situ) were compared for modified LMR UF resins with TEMPO-CNFs. The modified UF resins with TEMPO-CNFs decreased the nonvolatile solid contents, while increasing the viscosity and gel time. However, the in situ modification of UF resins with TEMPO-CNFs showed lower crystallinity than that of post-mixing. Then, the in situ method was compared for all CNMs to modify LMR UF resins. The modified UF resins with CMFs using the in situ method increased nonvolatile solid contents and viscosity but decreased the gel time. The crystallinity of UF resins modified with TEMPO-CNFs was the lowest even though the crystalline domains were not significantly changed for all modified UF resins. These results suggest that these CNMs should be modified to prevent the formation of crystalline domains in LMR UF resins.

• 한국식품조리과학회지
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• 제1권1호
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• pp.45-52
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• 1985

감자의 품종별 조리특성을 알아보기 위하여 춘작 4 종(남작, 대지, 도원 및 수미)과 하작 4종(남작, 수미빈체 및 라도사)을 선택하여 전분의 특성과 수우프의 점도와 식미를 측정하였다. 감자전분의 아밀로그람 특성을 품종에 따라 큰 차이를 보여 주었다. 춘작은 breakdown이나 setback 이나타나지 않고 연차적으로 점도가 상승하였으며, 호화개시 온도가 높았다. 하작의 빈체와 작은 호화가 쉽게 일어나며, breakdown 이 나타났다. 하작은 호화개시온도가 춘작에 비해 낮으므로, 전분입자가 치밀하지 못함을 유추할 수 있다. 수우프의 점도를 비교하면, 춘작의 수미, 대지 및 도원은 수우프의 온도가 내려감에 따라 점도상승이 뚜렷하나, 춘작의 남작과 하작 4종은 상승폭이 작았다. 으깬감자와 수우프의 식미검사를 보면 춘작에서는 남작이 가장 우수하였으며, 하작에서는 수미가 가장 높은 점수를 보였다. 감자의 농도에 따라 수우프의 맛은 달라지는데 춘작의 대지, 도원 및 수미는 19.8％와 23.5％ 농도에서 우수하였으나, 하작감자와 춘작의 남작은 27％농도에 서 우수하였다.

• 펄프종이기술
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• 제43권5호
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• pp.49-54
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• 2011

Curtain coating has been considered as the best coating technology because it is a coating technology that forms contour coating layer with better coverage. To increase the curtain stability surfactants are being used. In this study, the effect of a surfactant on the stability of curtain coating colors was examined by evaluating dynamic surface tension with a bubble surface tensiometer. Di-2-ethylhexyl sodium sulfosuccinate was used as a surfactant since it showed low dynamic surface tension at low surface age. And we evaluated the influence of surfactant on coating color properties including surface tension, viscosity and curtain stability. The surface tension of coating color was decreased when surfactant addition was increased up to 0.5 pph, but it was leveled off at 0.3 pph of surfactant addition. With the increase of surfactant addition rate, viscosity of coating color were increased. Micelles formed by surfactant contributed to the increase of the viscosity. Curtain stability was improved with the addition of surfactant until it reached up to 0.5 pph. Excessive addition of surfactant (> 0.5 pph) didn't improve curtain stability. This was attributed to Marangoni effect(self-healing) and decreasing of curtain thickness.

• 한국미생물·생명공학회지
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• 제22권2호
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• pp.175-181
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• 1994

A bacterial strain producing highly viscous polysaccharide(A29 POL) was isolated from soil and identified sa Bacillus sp. A29. The cultural conditions of the Bacillus sp. A29 for the polysaccharide prouction were dextrin 12%, soytone 0.2%, SnCl$_{2}$ $\cdot $2H$_{2}$O 0.02%, Na$_{2}$HPO$_{4}$ $\CDOT $12H$_{2}$O 0.36%, L-alanine 0.01%, initial pH6.8, and 30$\circ $C at pH 3 FOR 4 days. Final viscosity of the culture broth was 65, 000 cp and then the amount of produced polysaccharide was 8.3 g/l. A29 POL was composed of glucose and xylose. A29 POL showed high viscosity at low concentration(0.1%) and in the presence of the salts such as NaCl or CaCl$_{2}$. A29 POL showed high viscosity acid condition and at alkali condition and high pseudoplasticity in the presence of a NaCl or CaCl$_{2}$. It was shown that the viscosity at high temperature(80$\circ $C) was decreased but it was recovered at low temperature (20$\circ $C. A29 POL was able to from film and gel in the presence of MgSO$_{4}$ $\CDOT $7H$_{2}$O, Na$_{2}$CO$_{3}$ \CDOT $H$_{2}$O, MnSO$_{4}$ $\CDOT $ 7H$_{2}$O. A29 POL had anionic charge.

• 폴리머
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• 제31권6호
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• pp.491-496
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• 2007

고분자계 치아 수복용 복합재에서 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane(Bis-GMA) 70 wt%와 희석제인 triethylene glycol dimethacrylate(TEGDMA)가 30 wt% 포함된 혼합물이 레진 기질로 사용되고 있다. Bis-GMA의 높은 점도로 인해 첨가되는 TEGDMA는 수복재의 높은 경화 수축과 물성 저하의 원인이 된다. 본 연구에서는 TEGDMA 첨가량을 감소시켜 우수한 특성을 나타내는 수복재를 제조하기 위해 저점도 Bis-GMA 유도체들을 이용하여 새로운 치과용 수복재를 제조하였다. 히드록실기를 포함하지 않는 Bis-GMA 유도체들의 경화 특성은 Bis-GMA와 비슷하였지만 이들의 흡습성과 점도는 Bis-GMA에 비해 크게 낮았다. Bis-GMA 유도체를 포함한 수복재를 제조하여 경화 수축률, 흡습성, 기계적 물성을 실험한 결과 기존 상업적으로 사용되는 수복재보다 낮은 흡습성과 탁월한 물성을 나타내었고, 경화 수축률도 약 25% 감소하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.181-185
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• 2001

Three-dimensional finite-element-based numerical model of turbulent flow, heat transfer, macroscopic solidification and inclusion trajectory in a continuos steel slab caster was developed Turbulence was incorporated using the Improved Low-Re turbulence model with positive preserving approach. The mushy region was modeled as the porous media with average effective viscosity. A series of simulations was carried out to investigate the effects of the casting speed, the slab size, the delivered superheat the immersion depth of the SEN on the transport phenomena. In the absence of any known experimental data related to velocity profiles, the numerical predictions of the solidified profile on a caster was compared with breakouts data and a good agreement was found.

• Fibers and Polymers
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• 제5권2호
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• pp.145-150
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• 2004

Blends of poly(phenylene sulfide) (PPS) and polyethylene, either linear low density polyethylene (LLDPE) or metallocene-catalyzed polyethylene (MPE), that were prepared by melt blending, were investigated. From the rheological properties as determined by capillary rheometry, the melt viscosity of both PPS/LLDPE and PPS/MPE blends was low when PE was in dispersed phase, but high melt viscosity was observed for both blends with PPS in dispersed phase. Significant differences depending on the composition were found in the mechanical properties such as percent elongation at break and notched Izod impact strength. In addition, dispersed phase morphology of the blends was analyzed by a scanning electron microscope (SEM), together with brief discussion about the difference between them.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.337-339
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• 2008

Recently, Note PCs have being widely used due to their features such as good mobility and low power consumption. In order to ensure the current market position, further improvement is required. Especially, the lower operating voltage is essential for the long operating time of Note PCs. For the achievement of lower operating voltage, possible contributions from LC materials side are to lower the viscosity and to increase the dielectric constant without sacrificing the reliability. In order to achieve lower driving voltage, new LC mixtures have been developed, optimizing theirs physical properties.