• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.193-199
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• 2004

Poly(o-ethoxy)aniline (PEOA)/organoclay nanocomposite was prepared via a solvent intercalation using chloroform as a cosolvent with organically modified montmorillonite (OMMT) clay. The PEOA initially synthesized from a chemical oxidation polymerization in an acidic condition at pH = 1 was intercalated into interlayers of the clay with $25\;wt{\%}$ clay content. Electrical conductivity of the PEOA/OMMT nano­composite was found to be controlled via the intercalating process. The synthesized PEOA/OMMT nano­composite was characterized via an XRD and a TGA, and then adopted as an electrorheological (ER) material. The PEOA/OMMT synthesized with controllable electrical conductivity without a dedoping pro­cess was found to show typical ER characteristics possessing a yield stress from both steady state and dynamic measurements under an applied electric field.

• Korea-Australia Rheology Journal
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• 제18권3호
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• pp.161-167
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• 2006

This study presents results on the numerical simulation of Newtonian and non-Newtonian flow in a channel obstructed by an asymmetric array of obstacles for clarifying the descriptive ability of current non-Newtonian constitutive equations. Jones and Walters (1989) have performed the corresponding experiment that clearly demonstrates the characteristic difference among the flow patterns of the various liquids. In order to appropriately account for flow properties, the Navier-Stokes, the Carreau viscous and the Leonov equations are employed for Newtonian, shear thinning and extension hardening liquids, respectively. Making use of the tensor-logarithmic formulation of the Leonov model in the computational scheme, we have obtained stable solutions up to relatively high Deborah numbers. The peculiar characteristics of the non-Newtonian liquids such as shear thinning and extension hardening seem to be properly illustrated by the flow modeling. In our opinion, the results show the possibility of current constitutive modeling to appropriately describe non-Newtonian flow phenomena at least qualitatively, even though the model parameters specified for the current computation do not precisely represent material characteristics.

• 한국전기전자재료학회논문지
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• 제20권5호
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• pp.450-455
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• 2007

LCD color filters have been manufactured in a process called photolithography to date, but various printing methods have been studied currently in response to the trend of low-end LCD panels. Direct Printing Process is a suitable fabrication technique to develope pigment components whose dimensions are in nano. The success of this process depends on the systematic preparation of pigment millbase. Conventional millbase dispersions are constituted of the organic pigments, monomer, dispersant and solvents. An experimental study on the rheology of millbase dispersions is presented. Subsequently, this thesis attempts to find out the dispersive characteristics as well as the selection of pigments, monomers and dispersants in the part of millbase among the stages of manufacturing LCD color filters using the direct printing methods. The dispersive characteristics were shown through analytic devices such as PSA, Rheometer, etc.

• 한국건축시공학회지
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• 제14권2호
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• pp.118-126
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• 2014

본 연구에서는 콘크리트를 펌프압송할 경우, 콘크리트의 배합조건에 따른 레올로지 특성의 차이와 압송속도에 의해 펌핑관내의 마찰저항력이 달라지게 되는 것에 착안하여 레올로지특성과 펌핑관내 마찰저항계수의 상관관계를 도출하고자 하였다. 이를 위해 콘크리트용 레올로지 측정장치와 관내마찰저항 평가시험장치를 이용하여 레올로지특성과 마찰저항력을 측정하기 위한 펌프압송실험을 수행하였다. 연구결과, 펌핑전후의 레올로지특성에 큰 변화가 있는 것으로 파악되었으며, 시험장치에 의해 측정된 관내마찰 저항력과 이론상의 관내 최대전단력이 거의 동일한 값을 나타냈다. 또한, 펌핑 후 콘크리트의 소성점도와 관내마찰저항계수의 상관관계가 매우 높은 것으로 나타났으며, 본 연구에서 도출된 마찰저항계수에 의한 압송압력의 예측값이 실측결과와 매우 높은 상관관계를 갖는 것으로 나타났다.

• 동아시아식생활학회지
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• 제18권4호
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• pp.539-546
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• 2008

This study was conducted in order to investigate the effects of maesil extract on medium and cake flour using the falling number and RVA tests, as well as farinography, and alveography. The maesil extract were added on the medium and cake flour bases, 3% and 5% each. The falling numbers of the medium and cake flour with maesil extract were increased due to alteration of the protein in the flour. Analysis of the RVA characteristics showed that the addition of maesil extract did not have a significant effect on the initial pasting temperature. Peak viscosity, holding strength, final viscosity, and the breakdown and setback values of the medium flour were not consistent, but those of the cake flour decreased. Farinography demonstrated that the addition of maesil extract decreased water absorption and improved the stability of the medium and cake flour. The characteristics of the alveogram showed that the addition of maesil extract increased the extensibility and swelling index. Based on the experimental data, the processing rheology may be good when using maesil extract to make yellow layer cake.

• 동아시아식생활학회지
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• 제19권4호
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• pp.641-649
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• 2009

This study was conducted to investigate the effects of wheat germ on medium flour using falling number and RVA tests, as well as farinogram and rheofermentometer analyses. The wheat germ was added to the medium flour on a 3, 5, and 7% basis. Falling numbers increased with increasing amounts of wheat germ. Analysis of the RVA characteristics showed that the wheat germ additions did not have significant effects on the initial pasting temperature. In the farinogram, water absorption decreased with an increasing amount of wheat germ. Also, development time was longest in the control group and shortest in the group with the highest addition of wheat germ. The results of the effects of added wheat germ on fermentation by rheofermentometer analysis showed that the H'm value reached a maximum height at 3%. Finally, the volume of $CO_2$ lost was increased whereas the retention coefficient was decreased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.178-179
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• 2014

The fine blast furnace slag is widely used as the admixture as it helps to increase the fluidity, long term strength of the concrete but decrease the heat of hydration. In case of the fine blast furnace slag, if the fineness of the slag is enhanced with the addition of gypsum to the concrete for the supplement of low strength in early stage and the facilitation of the initial hydration, the quality of the concrete is expected to change depending on the volume of the gypsum volume fraction. But, up to now the study on the fine blast furnace slag has only focused on the effect of fineness, replacement and admixture and there have been almost no studies on the effect of the gypsum volume fraction. Accordingly, this study focuses on what effect the gypsum volume fraction would make on the fluidity characteristics of the ultrafine furnace slag cement paste by using the rheology properties.

• 한국전산유체공학회지
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• 제16권2호
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• pp.81-87
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• 2011

The importance of shear thinning non-Newtonian blood rheology on the hemodynamic characteristics of idealized cerebral saccular aneurysms were investigated by carrying out CFD simulations assuming two different non-Newtonian rheology models (Carreau and Ballyk models). To explore effects of vessel curvature, a straight and a curved vessel geometry were considered. The wall shear stress(WSS), relative residence time(RRT) and velocity distribution were compared at the different phases of cardiac cycle. As expected, blood entered the aneurysm at the distal neck and created large vortex in both aneurysms, but with higher momentum on the curved vessel. Hemodynamic characteristics such as WSS, and RRT exhibited only minor effects by choice of different rheological models although Ballyk model produced relatively higher effects. We conclude that the assumption of Newtonian fluid is reasonable for studies aimed at quantifying the hemodynamic characteristics, in particular, WSS-based parameters, considering the current accuracy level of medical image of cerebral aneurysm.

• Korea-Australia Rheology Journal
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• 제15권1호
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• pp.35-41
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• 2003

It is expected that particle size distribution of any portion obtained through screening, is of more uniform than that of the original mixture, typically following such as log-normal, Rosin-Rammler distributions and so on. In this study, therefore, a new relation between parameters of the uniform distribution and flow characteristics of the coarse particle suspensions is derived based on the continuous polydisperse model (Ookawara and Ogawa, 2002b), which is derived from the discrete polydisperse model (Ookawara and Ogawa,2002a). The derived model equation predicts a linear increase of viscosity with shear rate, viz., dilutant flow characteristics. Further, the increase of viscosity is expected to be proportional to the square of volume fraction of particles, and to show the linear dependency on density and average diameter of particles. It is also shown that the uniform distribution model includes additional term that expresses the effect of distribution width. For verification of the model, the experimental results of Clarke (1967) are cited as well as in our previous work for the monodisperse model (Ookawara and Ogawa,2000) since most parameters were varied independently in his work. It is suggested that the newly introduced term expands the applicable range compared with the monodisperse model.

• Korea-Australia Rheology Journal
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• 제19권2호
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• pp.61-66
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• 2007

The aggregation characteristics of red blood cells (RBCs) are known as important factors in the microvascular flow system, and increased RBC aggregation has been observed in various pathological diseases, such as thrombosis and myocardial infarction. This paper describes a simple microfluidic device for measuring the RBC aggregation by integrating a microfluidic slit rheometry and laser-backscattering technique. While a decreasing-pressure mechanism was applied to the microfluidic rheometry, a syllectogram (the light intensity versus time) showed an initial increase and a peak caused by the high shear stress-induced disaggregation, immediately followed by a decrease in the light intensity due to RBC aggregation. The critical shear stress (CST) corresponding to the peak intensity was examined as a new index of the RBC aggregation characteristics. The CST of RBCs increased with increasing aggregation-dominating protein (fibrinogen) in the blood plasma. The essential feature of this design was the combination of the rheometric-optic characterization of RBC aggregation with a microfluidic chip, which may potentially allow cell aggregation measurements to be easily carried out in a clinical setting.