• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.91-92
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• 2002

Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the characteristics of a certain lubricant under the condition of additives. especially for traction performance. it is also important to get the information of traction force as well. In this work. we developed the device for measuring friction force of EHL contact condition, which can trace the film thickness over the contact area with optical interferometer. To verify the validity of the measuring system, the friction force and film thickness under EHL condition are measured with the variation of additive ratios of viscosity Index improvers.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.267-271
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• 2002

Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the characteristics of a certain lubricant, it is also important to get the information of traction force as well. In this work, we developed the device for measuring friction force of ehl contact condition together with the film thickness. To verify the validity of the measuring system, the friction force and film thickness under ehl condition are measured with the variation of additive ratios of viscosity index Improvers.

• 한국인쇄학회지
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• 제12권1호
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• pp.13-27
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• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printablility of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular weight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• 한국인쇄학회지
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• 제12권1호
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• pp.145-157
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• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printability of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular \veight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.825-828
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• 2000

The objective of the present study is to develop a new device that the viscous characteristics of fluids are determined by applying the unsteady flow concept to the traditional capillary tube viscometer. The capillary tube viscometer consists of a small cylindrical reservoir, capillary tube, a load celt system oat measures the mass flow rate, interfacers, and computer. Due to the small size of the reservoir the height of liquid in the reservoir decreases as soon as the liquid in the reservoir drains out through the capillary and the mass flow rate in the capillary decreases as the hydrostatic pressure in the reservoir decreases resulting in a decrease of the shear rate in the capillary tube. The instantaneous shear rate and. driving force in the capillary tube are determined by measuring the mass flow rate through the capillary, and the fluid viscosity is determined from the measured flow rate and the driving force.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.762-767
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• 2007

As a macromolecule material, melted rubber flow shows characteristics of shear thinning fluid. The dynamic viscosity of this rubber fluid is influenced by temperature and shear strain rate. In this study, the numerical simulation of rubber extrusion forming process has been performed using commercial CFD code, Polyflow. Power-law model considering the effect of shear rate is used for the computer simulation of this non-Newyonian flow. Also Non-isothermal behavior is considered as Arrhenius-law model. Distributions of velocity and temperature are predicted through the simulation.

• 한국식품과학회지
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• 제29권1호
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• pp.138-144
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• 1997

토양으로부터 분리한 Metarrhizium anisopliae (Metschn.) Sorok이 생산하는 biopolymer YU-122의 물리, 화학적 특성을 알아보고, 그의 식품 및 생물산업에의 응용 가능성을 검토하여보았다. Biopolymer YU-l22의 flow behavior index (n)는 0.173으로서 pseudoplastic한 non-Newtonian용액 특성을 보였으며, 농도, 온도 및 pH의 변화에 따른 점도의 변화를 검토한 결과 0.3% 이상의 농도에서부터 농도의 증가에 따라 급격한 점도의 증가를 나타냈으며, $60^{\circ}C$, pH 11.0까지 점도의 변화 없이 안정한 성질을 갖는 것으로 나타났다. 또한 기존에 보고된 다른 polymer와는 달리 $NaCl,\;CaCl_2$ 등의 무기염의 첨가에 대하여서도 점도의 변화를 나타내지 않았다. Metarrhizium anisopliae (Metschn.) Sorok이 생산하는 biopolymer YU-122의 산업적 응용성을 검토하기 위하여 유화안정제로서의 성질 및 film 형성능, 해빙시간에 미치는 영향 등을 검토한 결과 옥수수유를 사용한 경우 xanthan gum보다 4배인 120시간동안 유화효과를 나타내었다. 또한 xanthan gum보다 우수한 film 향성능을 나타내었으며, 1% biopolymer YU-122용액에서 해빙시간이 3배까지 연장되어 해빙에 미치는 영향도 매우 우수한 것으로 나타났다.

• Korea-Australia Rheology Journal
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• 제14권1호
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• pp.1-9
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• 2002

Steady and dynamic shear properties of two hydrophobically modified alkali soluble emulsions (HASE), NPJI and NPJ2, were experimentally investigated. At the same polymer concentration, NPJ1 is appreciably more viscous and elastic than NPJ2. The high hydrophobicity of NPJ1 allows hydrophobic associations and more junction sites to be created, leading to the formation of a network structure. Under shear deformation, NPJ1 exhibits shear-thinning behaviour as compared with Newtonian characteristics of NPJ2. NPJ1 and NPJ2 exhibit a very high and a low level of elasticity respectively over the frequency range tested. For NPJ1, a crossover frequency appears, which is shifted to lower frequencies and hence, longer relaxation times, as concentration increases. Three different surfactants anionic SDS, cationic CTAB, and non-ionic TX-100 were employed to examine the effects of surfactants on the rheology of HASE. Due to the different ionic behaviour of the surfactant, each type of surfactant imposed different electrostatic interactions on the two HASE polymers. In general, at low surfactant concentration, a gradual increase in viscosity is observed until a maximum is reached, beyond which a continuous reduction of viscosity ensues. Viscosity development is a combined result of HASE-surfactant interactions, accompanied by constant rearrangement of the hydrophobic associative junctions, and electrostatic interactions.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.111-112
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• 2006

In order to investigate flow characteristics of blood flow in a micro tube ($100{\mu}m$ in diameter) according to hematocrit, in-vitro experiments were carried out using a micro-PIV technique. The micro-PIV system consists of a microscope, a 2 head Nd:YAG laser, a 12 bit cooled CCD camera and a delay generator. Blood was supplied into the micro tube using a syringe pump. Hematocrit of blood was controlled to be 20%, 30% and 40%. The blood flow has a cell free layer near the tube wall and its thickness was changed with increasing the flow rate and hematocrit. The hemorheological characteristics such as shear rate and viscosity were evaluated using the velocity field data measured. As the flow rate increased, the blunt velocity profile in the tube center was sharpened. The viscosity of blood was rapidly increased with decreasing shear rate, especially in the region of low shear rate, changing RBC rheological properties. The variation of velocity profile and blood viscosity shows typical characteristics of Non-Newtonian fluids. On the basis of inflection points, the cell free layer and two-phase flow consisting of plasma and suspensions including RBCs were clearly discriminated.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.296-309
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• 2003

The periodicity of the physiological flow has been the major interest of analytic research in this field up to now Among the mechanical forces stimulating the biochemical reaction of endothelial cells on the wall, the wall shear stresses show the strongest effect to the biochemical product. The objective of present study is to find the effects of velocity waveform on the wall shear stresses and pressure distribution along the artery and to present some correlation of the velocity waveform with the clinical observations. In order to investigate the complex flow phenomena in the bifurcated tube, constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids, are determined, and pulsatile momemtum equations are solved by the finite volume prediction. The results show that pressure and wall shear stresses are related to the velocity waveform of the physiological flow and the blood viscosity. And the variational tendency of the wall shear stresses along the flow direction is very similar to the applied sinusoidal and physiological velocity waveforms, but the stress values are quite different depending on the local region. Under the sinusoidal velocity waveform, a Newtonian fluid and blood show big differences in velocity. pressure, and wall shear stress as a function of time, but the differences under the physiological velocity waveform are negligibly small.