• Proceedings of the KSME Conference
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• 2001.06d
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• pp.909-914
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• 2001

Fluid properties which are most commonly used to evaluate spray atomization characteristics, are important because they affect velocity and size distribution of droplets. The purpose of this study was to incorporate the significant characteristics in atomization process of industrial etching spray and how each of them affects the design of precise pressure-swirl nozzles. The experiment was carried out with different viscosity and density of fluid. The macro characteristics of liquid spray, such as the spray angle and shape were captured by PMAS and the micro characteristics of liquid spray, such as droplet size and velocity were obtained by PDA. The mean velocity and SMD of droplets were measured along axial and radial direction. It was found that the higher viscosity and density resulted in the larger SMD and the lower mean velocity of droplets.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.241-246
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• 2001

Vortices terminating at free surface have been investigated extensively. Most of investigations, however, are focused on surface parallel vortices and little has been known about surface normal vortex or columnar vortex. Visualized experimental results utilizing LIF technique are discussed for the purpose of characterization of columnar vortex interacting with a clean and a contaminated free surfaces and a solid body interface in the present investigation. The results reveal that surface tension changes due to surface contamination although bulk viscosity remains constant and eventually the behavior of a columnar vortex interacting with a contaminated free surface and a solid body interface are totally different from the clean free surface case.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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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.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.59-64
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• 2001

The fluid flow, mass transfer and film thickness variation during a wafer spin coating process are numerically studied. Governing equations for the cylindrical coordinates are simplified using the similarity transformation and solved efficiently using the finite difference method. Concentration dependent viscosity and the binary diffusivity of the coating liquid are used in the analysis. The time variational velocity components of the coating liquid and the film thickness are analyzed according to the various spin speed. When the evaporation is considered, the flow decease in the early times due to the increase of the viscosity and the resultant flow resistance. Effects of the two film thinning mechanism, the flow-out and evaporation are also considered in the analysis.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.269-273
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• 1999

Immiscible polymer blends containing a liquid crystalline polymer dispersed phase can be described by existing blend theories when the dispersed-phase droplets are large relative to the orientation correlation length ("domain size") of the LCP. There does not appear to be an interfacial contribution to the linear viscoelastic properties of the blend from droplets smaller than the correlation length. Polyester blends, where interfacial interactions occur between the LCP and the matrix, exhibit a reduction in viscosity to below the viscosity of either component at low shear rates, where the droplet morphology is spherical. These anomalies cannot be explained in the context of existing theory.ng theory.

• The Korean Journal of Rheology
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• v.8 no.2
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• pp.92-102
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• 1996

두 종류의 열방성 액정고분자와 세종류의 엔지니어링 고분자와의 블렌드들에 대해 유변학적/형구학적 연구를 한 결과 블렌드의 유동거동과 물성이현저히 다른 두 그룹으로 나 뉘어짐을 발견하였다. 즉 연속상의 조업온도가 분산상의 전이온도보다 높은 그룹A에 속하 는 블렌드의 전단점도/신장점도는 액정고분자를 첨가할수록 첨가할수록 감소하고 블렌드의 신장점도는 연속상의 그것처럼 신장변형률속도가 커질수록 증가하였다. 또한 분산상의 점도 가 연속상의 그것보다 작아서 분산상이 미세섬유구조의 형태로 존재하였다. 이와 대조적으 로 연속상의 조업온도가 액정고분자의 전이온도보다 낮은 그룹 B에 속하는 블렌드는 반대 의 거동을 보였고 분산상의 미세섬유구조가 존재하지 않았다. 그러나 연신변형이 주가 되는 방사공정을 거치면 그룹A와 B블렌드 공히 분산상이 비슷한 미세섬유구조의 형태로 존재하 고 기계적 성질도 크게 향상되는 결과를 보였다. 이는 블렌드내의 신장유동이 분산상의 섬 유구조형상에 결정적 역할을 하기 때문이라 판단된다.

• Proceedings of the KSME Conference
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• 2000.04b
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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.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1316-1321
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• 2004

An experimental study is performed on atomization characteristics and stable operating condition for injection of high viscous waste vegetable oil using effervescent atomizer with two aerator tubes. Consideration is given to the effects of ALR and liquid viscosity on the velocity and mean diameter of the injected droplet. It is found that (i) as ALR increases, the axial velocity of the droplet is increased, while half-velocity width and SMD are decreased regardless of the change in liquid viscosities, (ii) the rate of fine drop distribution occupied in the total spray field is increased with an increasing in ALR, and (iii) the effect of viscosity on atomization characteristics is minor.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.843-846
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• 2004

For the fast growing Liquid Crystal Display (LCD) TV market, it is essential to make the LCD panels to show moving images without any visual difficulties such as blurring or tailing. Owing to reduction of the cell gap and the improved Liquid Crystal (LC) mixtures with low viscosity, it is possible that our S-IPS TFT-LCDs feature a response time (R/T) as fast as 1-frame time (16ms) for a white-black operation and less than a 16rns in all gray levels without Over Driving Circuit (ODC) technology. Currently, mass production of the large size IPS panels with high speed has been successfully achieved. In order to achieve faster response time, new LC mixtures have been developed, optimizing the physical properties of rotational viscosity (${\gamma}$1) and elastic constants (Kii). Also, the LC mixtures with high elastic constant allow us to increase the cell gap. In this paper, realization of fast switching time in IPS mode with optimized '${\gamma}$1/Kii' parameter in the LC mixtures forms the core of this paper.

• Bulletin of the Korean Chemical Society
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• v.5 no.6
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• pp.245-248
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• 1984

Raman spectroscopy was used to study the reorientational motion of hexafluorobenzene in benzene and also in neutral solvents. From the viscosity dependence of the reorientation time, intermolecular interaction in the systems was investigated. No evidence was found to support the presence of long-lived 1:1 complex of hexafluorobenzene and benzene. The unusual viscosity dependence of the reorientational motion observed in the systems was explained as due to the formation of transient complexes.