• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.820-829
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• 2017

Vegetable oil dielectrics have been used in transformers as green alternatives to mineral insulating oils for about twenty years, because of their advantages of non-toxic, biodegradability, and renewability. However, the viscosity of vegetable oils is more than 3 times of mineral oils, which means a poor heat dissipation capacity. To get low-viscosity dielectrics, transesterification and purification were performed to prepare vegetable oil methyl esters in this study. Electrical and physical properties were determined to investigate their potential as dielectrics. The results showed that the methyl ester products had good dielectric strengths, high water saturation and enough fire resistance. The viscosities (at $40^{\circ}C$) were 0.2 times less than FR3 fluid, and 0.7 times less than mineral oil, which indicated superior cooling capacity as we expected. With the assistance of 0.5 wt% pour point depressants, canola oil methyl ester exhibited the lowest pour point ($-26^{\circ}C$) among the products which was lower than FR3 fluid ($-21^{\circ}C$) and 25# mineral oil ($-23^{\circ}C$). Thus, canola oil methyl ester was the best candidate as a low-viscosity vegetable oil-based dielectric. The low-viscosity fluid could extend the service life of transformers by its better cooling capacity compared with nature ester dielectrics.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.581-589
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• 2015

In this study, the viscosity of a liquid carbon dioxide ($LCO_2$) that can potentially be used in a wet feed coal gasifier was evaluated. A pressurized capillary viscometer was employed to obtain the viscosity data of $LCO_2$ using two different methods. During the first method, the measurements were conducted under quasi-steady and high pressure flow conditions where two-phase flow was greatly minimized. The viscosity of $LCO_2$ was determined using turbulent friction relationship. At the second flow condition where unsteady flow is induced, the viscosity of $LCO_2$ was measured using the half-time pressure decay data and was further compared with values calculated by the first method.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.574-592
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• 1996

This study investigated the time-dependent dimensional changes of elastomeric impression materials using holographic interferometry. Six commercial impression materials, Permlastic(polysulfide), Xantopren VL (condensation silicone), low and medium viscosity of Exafine, Provil (addition silicone), and Impregum(polyether), were selected. Steel plate was used as custom tray, and each impression specimen was 20 mm in width, 15 mm in length and 3 mm in thickness. Each impression material was evaluated at 30 minutes, 1, 2, 4, 6, 8 and 12 hours after setting using real-time holography. The results were as follow : 1. Xantopren VL and Permlastic showed relatively severe and continuous dimensional changes after setting. Low viscosity of Exafine, Provil, Impregum showed relatively slight dimensional changes with function of time and medium viscosity of Exafine showed almost no dimensional change from 2 hours after setting to 6 hours. 2. On initial dimensional changes within 1 hour, the amount of change in low viscosity of Exafine was the least and Xantopren VL was the largest. 3. On dimensional changes at 4 hours after setting, the amount of change in medium viscosity of Exafine was the least and tile change of Xantopren VL was the largest. 4. In overall dimensional stability during 12 hours, medium viscosity of Exafine was the most stable and Xantopren VL and Permlastic were least stable.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.411-415
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• 2009

To replace waste oil with the lowest grade which has high viscosity into heating fuel, light oil and buncker C oil in waste oil was used and the fuel characteristic was analyzed by its concentration after mixing oil. The mixture conditions were controlled by the reaction time (30 s~30 min) and kept by the reaction temperature ($75{\pm}5^{\circ}C$) when mixing speed was stirred at 3400~3600 rpm. We used the buncker C oil and light oil to decrease viscosity of waste oil and the dynamic viscosity was decreased by 81~96%. Optimum mixing ratio (waste oil : buncker C oil : light oil) as heating fuel was 1 : 1 : 1. Flash point, dynamic viscosity and heating value of this case were identified $78^{\circ}C$, $20.02mm^{2}/s$, 9158 kcal/L respectively.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.369-375
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• 2015

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and $28{\mu}m$, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D's high performance.

• The Korean Journal of Rheology
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• v.9 no.1
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• pp.27-32
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• 1997

GM 은 Amorphopallus Konjac K. Koch의 tuber의 주성분으로알카리 응고제를 첨가 함에 따라 열적으로 안정한 gel을 형성한다. GM에 침전제로 메탄올을 사용하여 4단계로 분 별하였고 각 분별물(F.1, F.2, F.3, F.4)들은 Mark-Houwink 식을 이용하여 분자량을 산출하 였다. Ubbelohde를 이용한 농도에 따른 환산점도로부터 고유 점성도값을 구한 결과 분자량 이 높은 분별물이 분자량이 낮은 분별물에 비하여 직선으로부터 벗어남을 알수 있었다. 또 한 고유점성도는 분자량이 증가할수록 증가하였고, 분자량 분포 범위가 broad하게 나타났다. GM용액의 frequency와 shear rate에 따른 viscosity를 측정한결과 낮은 frequency에서는 loss modulus(G＂)가 storage modulus(G＂)보다 큰 값을 가졌으나 높은 frequency에서는 G ＇가 G＂보다 크게 나타났다. 이 현상은 분자들의 얽힘에 관한 시간 의존도로써 설명할수 있다. 즉높은 frequency에서는 탄소 사슬간의 얽힘들이 진동기간내에 분자결합이 끊어지기 에 충분한 시간을 갖지 못하여 그 조직이 교차 결합을 한 gel처럼 행동하게 되고 한편 낮은 frequency에서는 탄소사슬들의 얽힘이 풀리고 흐르기에 충분한 시간을 갖게된다. Shear rate에 따른 viscosity값과 frequency에 대한 dynamic viscosity값은 거의 유사한 변화를 나 타내었다.

• Journal of Magnetics
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• v.4 no.1
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• pp.13-16
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• 1999

Magnetic viscosities of a commercialized metal evaporated tape were measured as a function of sweeping rate in VSM at room temperature. Within several seconds in the viscosity measurement, curves are downward concave and more concave with increasing sweeping rate when magnetization were plotted as a logarithmic function of time. However, magnetization varied as a logarithmic function of time after several seconds. Magetic viscosity coefficient gradually increased with increasing sweeping rate and then kept a constant value at a rate faster than 61.5 Oe/s. It was supposed that magnetic viscosity occurs during field sweeping, which was in good agreement with Sharrock's model qualitatively. Activation volume decreased with increasing sweeping rate, which was due to the fact that magnetic viscosity coefficients increased with sweeping rate while irreversible susceptibilities were not affected by sweeping rate.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.707-710
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• 1999

Moisture content and intrinsic viscosity of antistatic polyethyleneterephthalate(PET) depending on the thermal stabilizer content was studied. The terminal moisture content of antistatic PET was a function of drying temperature rather than drying time. Intrinsic viscosity drop of antistatic PET after melt spinning increased with increasing moisture content of it. After melt spinning, intrinsic viscosity of antistatic PET was decreased due to the thermal degradation of polyoxyalkyleneglycol(POAG) component of antistatic agent. Triphenylphosphate(TPP) was more effective as a thermal stabilizer than trimethylphosphate(TMP). A little intrinsic viscosity drop after melt spinning was found in PET containing 300 ppm of TPP as a thermal stabilizer.

• Food Science of Animal Resources
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• v.18 no.3
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• pp.209-215
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• 1998

Effects of protein concentration, ionic strength, pH, and temperature range on the heat-induced denaturation of salt soluble protein extracted from spent layer meat were investigated. Viscosity of salt soluble protein heated at 65$^{\circ}C$ for 30 min began to increase sharply above 7 mg/ml of breast protein concentration, and above 21 mg/ml of leg protein concentration, respectively. Both turbidity and viscosity showed the highest value in cooked protein solution with pH 6.0 and 1% NaCl. The turbidity of salt soluble protein started to increase continuously from 40$^{\circ}C$ to 80$^{\circ}C$. The viscosity increased rapidly from 45$^{\circ}C$ to 60$^{\circ}C$ in breast protein, and increased from 50$^{\circ}C$ to 55$^{\circ}C$ in leg protein, respectively, and then kept relatively constant. Breast protein had higher viscosity than leg protein during heat-induced gelation. Therefore, salt soluble protein from spent layer meat was associated with denatured protein (turbidity change) prior to gelation (viscosity change) during heating. Breast protein showed lower thermal transition temperature, and better gel formation than leg protein during heating.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.2
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• pp.67-73
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• 2012

Structural stability and shock absorption are important properties for corrugated board. In order to maintain structural stability, adhesive properties between top/bottom liners and corrugated medium are not only essential but also important for productivity and product quality. Borax has been an essential ingredient in corrugating adhesive solution. Borax increases viscosity, bonding between starchs and green adhesive bond. The objective of this research is to improving adhesive strength and viscosity stability by adding cross-linking agent instead of borax. Rheology and penetration of main starch gelatinization slurry were affected by borax addition level. Borax increased viscosity and decreased viscosity stability, while cross-linking additives increased viscosity stability and adhesive strength by anchoring effect.