• 한국분무공학회지
• /
• 제16권3호
• /
• pp.140-145
• /
• 2011

Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the breakup process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. The breakup process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. As the injection pressure increased, rimless patterns which were composed of ligament sheets and small droplets emerged due to the effect of the aerodynamic action.

• Bulletin of the Korean Chemical Society
• /
• 제30권1호
• /
• pp.177-182
• /
• 2009

We present the geminate rebinding kinetics measurements of CO to 2-methylimidazole (2-MeIm) bound ferrous protoporphyrin- IX (FePPIX) in alkaline glycerol/water mixtures at 293 K after photolysis. The kinetics was probed by monitoring the CO stretching mode using femtosecond vibrational spectroscopy. When 2-MeIm is used in excess, heme dimers that typically form in low viscosity solutions disappear as the viscosity of the solvent increases. Heme aggregates formed in low viscosity solutions turn monomeric as more 2-MeIm is added, suggesting that 6-coordinated heme, including a strong proximal histidine tends to be in the monomeric form. The vibrational band of CO in the 2-MeIM-FePPIX-CO is well described by a single Gaussian function centered at 1958 $cm^-1$ and 28 $cm^-1$ full width at half maximum. The efficiency and rate of the geminate rebinding of CO to the heme increase with viscosity of the solvent, suggesting that retention of the dissociated CO near the heme, for a longer period by the viscous solvent media, accelerates rebinding.

• 펄프종이기술
• /
• 제29권3호
• /
• pp.17-25
• /
• 1997

Natural water-soluble polymers such as starch, casein and carboxy methyl cellulose(CMC) have been limited in their uses. However, the proper water retention of coating colors can not be obtained without addition of these polymers. Furthermore, the coating runnability and the physical properties of coated paper were not also satisfied. Therefore, the objective of this study was to synthesize the water retention and flow modifiers which can improve the water retention and flow properties of coating colors. We have measured physical properties of flow modifiers and coating colors which included flow modifiers. The viscosity of flow modifiers was very low at acid pH, and rapidly increased at about pH 7, and gradually reached to equilibrium at alkali pH. Such an increase comes from the molecular weight of flow modifiers and the amount of acrylic and methacrylic acids. The viscosity of coating color containing the flow modifiers was lower than that containing CMC. However, both of them had little difference in water retention. The water-phase viscosity of synthetic modifier containing coating color was either higher or similar compared to that of CMC containing coating color. The high shear viscosity of coating colors was low. Therefore, it can be concluded that the synthetic flow modifiers are very useful for improvement of flow properties and water retentions.

• 한국식생활문화학회지
• /
• 제20권3호
• /
• pp.299-304
• /
• 2005

This study investigated the feasibility of the bread making process with the mixture of the functional rice flour. The bread was manufactured with 20, 30 or 40% functional rice flour with increasing and wheat flour. Gelatinization characteristics of the rice starch was examined by differential scanning calorimetry(DSC). Coated with soluble dietary fiber rice showed the highest gelatinization enthalphy among functional rices and other functional rices were similar to normal rice. in the viscosity point of view. generally the viscosity related to the addition ratio. The most viscose case was 30% Sangwhang rice but in fermented with monascus ruber rice case, viscosity was low even with 40% case because of the transformation of the starch granules. In sensory evaluation, the highest sensory scores for the uniformity of pore size and flavor were obtained when sangwhang rice flour content was 20%. The textual study was mainly focused on the hardness, cohesiveness, adhesiveness, springiness, chewiness. Textural characteristics of functional rice bread crumb bakedwith 20% coated with soluble dietary fiber rice, 20% sangwhang was low in hardness, chewiness and gumminess. Therefore, Sangwhang rice flour 20%, Monascous ruber 20% and Coated soluble dietary fiber rice 20% were considered to be the most suitable addition ratio for the rice breads.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 추계학술대회 논문집
• /
• pp.230-233
• /
• 2008

The vanadium rich ash of petroleum coke can give a slagging problem during because of the high melting point of $V_2O_3$. For continuous removal of the slag, petroleum coke is often mixed with coal, and the viscosity of the mixed slag is an important property, determining the gasification temperature. The viscosities of the mixed slag from various mixing ratios of petroleum coke and a bituminous coal were investigated. When mixed with a crystalline coal slag, $T_{cv}$ was increased at a higher the coke content in the mixed feed. When the $V_2O_3$ concentration was greater than 4.5%, it was difficult to get accurate measurements of $T_{cv}$. The SEM/EDX analyses of the cooled slag revealed that the major crystalline phase was anorthite, and $T_{cv}$ should be related to the formation temperature of anorthite. The SEM/EDX analyses also showed that, at low concentrations of vanadium, part vanadium formed a crystalline phase with Al-Si-Ca-Fe, and the rest remained in the glassy phase, suggesting that vanadium existed as a slag component at the low viscosity region. At a high concentration, vanadium forms a phase with Ca, and the Ca-V phase was separated from the slag phase, and formed a layer above the slag. FeO in petroleum coke also played an important role determining viscosity: at high temperatures, increased FeO lowered the viscosity, but as it formed a spinel phase, the depletion of FeO in the slag resulted in a higher viscosity.

• 한국건설순환자원학회논문집
• /
• 제6권2호
• /
• pp.123-129
• /
• 2018

본 연구의 목적은 고강도 및 일반강도 영역의 물-결합재 비에 대해 시멘트계열 재료의 점도를 감소시키기는 것에 대한 정보를 제공하는 것이다. 시멘트 계열 재료의 유동성을 결정하는 것은 물-결합재 비 및 치환재료와 감수제가 있다. 이를 레올로지적으로 보았을 때 물-결합재 비가 낮은 경우 항복치와 점도를 낮추며 감수제의 경우 항복치 저감에 영향을 주지만 점도 저하에는 한계가 있다. 따라서 이 연구에서는 시멘트 계열 재료의 점도를 낮추기 위해 물-결합재 비에 따른 폐석회석 치환에 대한 점도 저하 가능성을 분석하였다. 실험 결과, 폐석회석을 치환하였을 경우 점도 저하의 효과가 있었으며 이는 시멘트 계열 재료의 점도 제어에 유의미한 결과를 주는 것으로 판단되었다. 따라서 본 연구의 결과는 시멘트 계열 재료의 점도를 낮추는 방안으로써 분체 치환에 의한 방안의 기초적인 자료가 될 것으로 생각된다.

• 해양환경안전학회지
• /
• 제22권2호
• /
• pp.240-245
• /
• 2016

본 연구에서는 해상용 경유의 희석량에 따른 선박용 윤활유의 점도 및 전단응력의 변화 등 유변학적 거동에 대한 연구를 하였다. 연료희석에 의한 윤활유의 점도감소는 피스톤링 및 라이너의 마모로 인한 엔진내구성을 저하키는 중요한 요소이다. 연구에 사용된 윤활유는 고유황 경유(황함유량 0.05 %)를 3 %, 6 %, 10 %, 15 %, 20 %로 희석하여 magnetic stirrer를 이용, 혼합하여 제조하였다. 측정온도는 $-10^{\circ}C{\sim}80^{\circ}C$ 범위로 설정하고, 점도 및 전단응력 변화는 회전점도계인 Brookfield Viscometer를 이용하여 측정하였다. 윤활유에 해상용 경유의 희석량이 증가할수록 점도 및 전단응력이 감소하며, 이것은 상대적으로 낮은 점도의 해상용 경유가 윤활유에 희석됨에 따라 윤활유의 점도 및 전단응력이 낮아지기 때문이다. 특히, 저온($0{\sim}-10^{\circ}C$)에서는 점도 및 전단응력이 급격이 낮아지다가, $40^{\circ}C$ 이상에서는 점도 및 전단응력 감소가 해상용 경유 희석량의 영향을 거의 받지 않는다. 온도가 높아짐에 따라, 윤활유의 점도 및 전단응력 감소는 윤활유의 뉴턴유체 거동을 보이는 것을 확인했다. 경유의 혼입에 의한 점도감소로 선박의 엔진마모를 촉진할 수 있으므로 엔진의 내구성 향상을 위해 윤활유의 주기적인 관리가 필요하다.

• Tribology and Lubricants
• /
• 제30권3호
• /
• pp.189-198
• /
• 2014

This paper presents the results of an experimental investigation of the correlation between the lubrication characteristics of an engine and its fuel economy. Improving the lubrication characteristics of the engine oil is one of the most efficient ways to improve a car's fuel economy. The methods to accomplish this include lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver. In addition, it is necessary to use different methods to reduce the friction to individual lubrication areas, because different lubrication regimes are used for different engine parts. The experimental investigation in this study is based on design of experiments ; this paper presents the results of a modified Sequence VID test, which is an ASTM standard test used to measure the effects of automotive engine oils on the fuel economy of passenger cars. The results demonstrate the effects of the following lubrication factors on the fuel economy : the low temperature cranking viscosity, high-temperature high shear (HTHS) viscosity, friction modifier, polymer type and shear stability index of the viscosity index improver. Moreover, this study involves an analysis of variance based on design of experiments. The test results show that the HTHS viscosity, friction modifier and shear stability index of the viscosity index improver are more effective than the other factors. Therefore, lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver should be considered to improve fuel economy.

• Journal of Korean Neurosurgical Society
• /
• 제62권2호
• /
• pp.183-192
• /
• 2019

Objective : The objective of this study was to analyze patient-specific blood flow in ruptured aneurysms using obtained non-Newtonian viscosity and to observe associated hemodynamic features and morphological effects. Methods : Five patients with acute subarachnoid hemorrhage caused by ruptured posterior communicating artery aneurysms were included in the study. Patients' blood samples were measured immediately after enrollment. Computational fluid dynamics (CFD) was conducted to evaluate viscosity distributions and wall shear stress (WSS) distributions using a patient-specific geometric model and shear-thinning viscosity properties. Results : Substantial viscosity change was found at the dome of the aneurysms studied when applying non-Newtonian blood viscosity measured at peak-systole and end-diastole. The maximal WSS of the non-Newtonian model on an aneurysm at peak-systole was approximately 16% lower compared to Newtonian fluid, and most of the hemodynamic features of Newtonian flow at the aneurysms were higher, except for minimal WSS value. However, the differences between the Newtonian and non-Newtonian flow were not statistically significant. Rupture point of an aneurysm showed low WSS regardless of Newtonian or non-Newtonian CFD analyses. Conclusion : By using measured non-Newtonian viscosity and geometry on patient-specific CFD analysis, morphologic differences in hemodynamic features, such as changes in whole blood viscosity and WSS, were observed. Therefore, measured non-Newtonian viscosity might be possibly useful to obtain patient-specific hemodynamic and morphologic result.

• 대한기계학회논문집B
• /
• 제26권6호
• /
• pp.868-874
• /
• 2002

A high-impulse, low-power, digital microthruster has been developed using low-boiling-temperature liquid propellant with high-viscosity fluid plug. The viscous fiction force of the fluid plug increases the blast pressure and the low-boiling-temperature liquid propellant is intended to reduce input power consumption. The three-layer microthruster has been fabricated by surface micromachining as well as bulk micromachining in the size of 7$\times$13$\times$1.5㎣. A digital output impulse bit of 6.4$\times$10$^{-8}$ Nsec has been obtained from the fabricated microthruster using perfluoro normal hexane (FC72) propellant and oil plug, resulting in about ten times increase of the impulse bit using one hundredth electrical input energy compared to the conventional multiple-shot microthruster.