• Bulletin of the Korean Chemical Society
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• v.3 no.4
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• pp.133-139
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• 1982

It has been presumed that the molten sulfur above $159^{\circ}C$ consists of an equilibrium mixture of $S_8$ rings and $S_x$ polymers where the number average degree of polymerization, P, is large. But it is known that admixture of halogens with liquid sulfur greatly reduce the viscosity. Constructing a new equilibrium equation, it is possible to evaluate the viscosity when halogens are added to liquid sulfur. Calculated viscosity is in good agreement with experimental values. Using the proposed model, the thermodynamic properties of liquid sulfur are also calculated over a wide range of temperature which the sulfur exists as the polymer.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.11a
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• pp.94-99
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• 1989

This paper analyzes file stiffness, damping coefficient, friction force and flow coefficient of externally pressurized oil journal beating, including the effect of journal rotation according to the Sommerfeld number. This paper assumed that the oil in the whole pocket has constant pressure, and that the oil in the whole bearing region has constant viscosity, temperature and density. Reynolds equation is derived from Nuvier - Stokes equation and continuity equation. And solved bearing pressure by ADI method for whole bearing region and fitted with out flow rate of pocket region. The model for numerical simulation is hydro - static oil journal bearing for high-speed, high-accuracy lathe spindle.

• Bulletin of the Korean Mathematical Society
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• v.43 no.2
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• pp.245-252
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• 2006

In this paper we study the uniform decay estimates of the energy for the nonlinear wave equation of Kirchhoff type $$y'(t)-M({\mid}{\nabla}y(t){\mid}^2){\triangle}y(t)\;+\;{\delta}y'(t)=f(t)$$ with the damping constant ${\delta} > 0$ in a bounded domain ${\Omega}\;{\subset}\;\mathbb{R}^n$.

• East Asian mathematical journal
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• v.29 no.5
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• pp.503-510
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• 2013

A quadratic B-spline finite element method for the spatial variable combined with a Newton method for the time variable is proposed to approximate a solution of Benjamin-Bona-Mahony-Burgers (BBMB) equation. Two examples were considered to show the efficiency of the proposed scheme. The numerical solutions obtained for various viscosity were compared with the exact solutions. The numerical results show that the scheme is efficient and feasible.

• Fire Science and Engineering
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• v.17 no.2
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• pp.43-49
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• 2003

For the inert gases of Ar, $N_2$and $CO_2$, the empirical equations of the gas mixture were correlated in terms of saturated pressure, density and viscosity. They were obtained by regression analysis based on the mixing rule. The empirical equation of saturated pressure was assumed as the first order function of temperature. The empirical form of density was expressed as compressibility factor and saturated pressure while the empirical equation of viscosity was formulated as a power function of temperature. This empirical equations of the physical properties were obtained in the composition of Ar, $N_2$and $CO_2$, 40/50/10(mol. %).

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.156-164
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocity and temperature fields during rheology forming process, the earth governing equation correspondent to the liquid and solid region are adapted. Therefore, each numerical models considering the solid and liquid region existing within the semi-solid material have been developed to predict the deflect of rheology forming gnarls. The Arbitrary Boundary Maker And Cell (ABMAC) method is employed to solve the two-phase flow model of the Navier-Stokes equation. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity. The liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Journal of Advanced Marine Engineering and Technology
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• v.6 no.2
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• pp.21-41
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• 1982

Viscosity, especially characteristic among various properties of visco-elastic fluids such as high polymer solutions, is affected mainly by temperature and concentration. Hence, it is important for fluid engineering to express, by some equations, how the fluid characteristics vary with the change of temperature and concentration and to analyze them to obtain consistent viscous characteristics. High polymer solutions, synthetic products of modern chemical industry, suggest many interesting investigations because they are typical visco-elastic materials. Experimentation was made to derive some useful fluid characteristic equations of SEPARAN-NP10 (polyacylamide) expressed by n (flow behavior index) and K' (consistency index) when it is given temperature and concentration variation. To measure viscosity, capillary viscometer was adopted and the range of experimentation is 0-2,000 P.P.M. in concentration and 15-55 .deg.C in temperature. The experimental results are summarized as follows: The flow behavior index n 1) has nearly constant results irrespective of temperature variation at same conentration and the results are shown in (Table. 4-4-3) 2) has following equation, regardless of temperature, for the variation of concentration. n=-1.0765*10$^{-4}$ P+0.9915 (P:P.P.M.) The consistency index K' 1) has different results for the variation of temperature at same concentration and the results are given in (Table.4-7-2) 2) has following equation for the variation of concentration at same temperature. log 10$^{4}$K' =6.4785*10$^{-4}$ P-1.0529 (P:P.P.M)

• Fire Science and Engineering
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• v.17 no.1
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• pp.26-32
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• 2003

Inert gases, Af, $N_2$, $CO_2$, as a Halon alternative, the empirical equations were correlated in terms of saturated pressure, density and viscosity, They were obtained by regression analysis from the experimental data in the literature. The empirical equations of saturated pressure were expressed as the second and third order function of temperature. The empirical equation for Ar and $N_2$ of density were expressed as the first order function of temperature. And $CO_2$ was expressed as the second and third order function of temperature. The empirical equation of viscosity was formulated as a power function with temperature. This empirical equations would allow us to predict pure component state.

• Advanced Composite Materials
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• v.17 no.3
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• pp.191-214
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• 2008

Polypropylene/layered silicate nanocomposites containing maleic anhydride grafted polypropylene were prepared by melt compounding and their rheological behavior was investigated in shear flow. Transient and steady shear flows were simulated numerically by using the K-BKZ integral constitutive equation along with experimentally determined damping functions under dynamic oscillatory and step strain shear flows. Nonlinear shear responses were predicted with the K-BKZ constitutive equation using two different damping functions such as the Wagner and PSM models. It was observed that PP-g-MAH compatibilized PP/layered silicate nanocomposites have stronger and earlier shear thinning and higher steady shear viscosity than pure PP resin or uncompatibilized nanocomposites at low shear rate regions. Strong damping behavior of the PP/layered silicate nanocomposite was predicted under large step shear strain and considered as a result of the strain-induced orientation of the organoclay in the shear flow. Steady shear viscosity of the pure PP and uncompatibilized nanocomposite predicted by the K-BKZ model was in good agreement with the experimental results at all shear rate regions. However, the model was inadequate to predict the steady shear viscosity of PP-g-MAH compatibilized nanocomposites quantitatively because the K-BKZ model overestimates strain-softening damping behavior for PP/layered silicate nanocomposites.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.3
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• pp.466-470
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• 2001

Response surface methodology was used for monitoring extraction conditions, based on quality properties of old pumpkin extracts. Hunter's color L value of extracts was maximized at 101℃, 2.6 hr and decreased gradually after maximum point. The polynomial equation for Hunter's color L value showed 10% of significance level and 0.8799 of R². Hunter's color a value was minimized at 117℃, 3.9 hr and R² of polynomial equation was 0.9852 within 1% significance level. Hunter's color b value and ΔE value increased as the extracting temperature and time increased. Extraction yield of old pumpkin was maximized at 110℃, 4 hr and increased in proportional to the extracting temperature and time, but decreased after 113℃ and 2 hr. Viscosity of pumpkin extracts were maximized at 120℃, nearly 3 hr. R² of polynomial equations for yield, viscosity and sugar content were 0.9532, 0.9812 and 0.8869, respectively. Optimum ranges of extraction conditions for quality properties of old pumpkin were 102∼109℃, 2.5∼3.5 hr, respectively. Predicted values at the optimum extraction condition agreed with experimental values.