• Tribology and Lubricants
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• v.30 no.5
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• pp.247-255
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• 2014

Charged polymer chains, i.e., polyelectrolytes, are known to show superior aqueous lubricating properties compared to those of neutral polymer chains, especially in brush conformation. This is primarily because of the incorporation of a large amount of counterions within the polymer layers and the consequently increased osmotic pressure. However, this effect is active only when the polymer chains remain immobilized even under tribostress, which is not realistic for high-contact pressure tribological applications, especially when they are irreversibly immobilized on tribopair surfaces. In contrast, with free polymers, which can be included as surface-active additives in the base lubricant (water), long-term lubricating performance based on "self-healing" properties is readily expected. In order to assess whether the superior aqueous lubricating properties of polyelectrolyte chains are valid for free polymers too, this study reviews recent studies on the tribological properties of many charged biopolymer and synthetic copolymers at a nonpolar, hydrophobic interface. In contrast to the irreversibly immobilized polyelectrolyte chains, free polyelectrolyte chains show inferior aqueous lubricating properties compared to their neutral counterparts owing to charge accumulation and the consequently impeded surface adsorption on the nonpolar surface. Nevertheless, bovine submaxillary mucin (BSM), a representative biopolymer, shows a sufficiently effective surface adsorption and aqueous lubricating capabilities even at neutral pH without losing the polyanionic characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1348-1358
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• 2004

The filling pattern and an adaptive grid refinement based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation fur flow analysis is Navier-Stokes equation including inertia and gravity effects. The mixed FE formulation and predictor-corrector method are used effectively for unsteady numerical simulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among seven filling patterns at each tetrahedral control volume. By adaptive grid refinement, the new flow field that renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. The collapse of a water dam and the filling of a fluidity spiral have been analyzed. The numerical results have been in good agreement with the experimental results and the efficiency of the adaptive grid refinement and filling pattern techniques have been verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.91-100
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• 1988

Assuming that tidal level is constantly changed with an amplitude of 10 meters and a cycle of 12 hours, the slope stability for a typical dyke is analysed. The variation of pore water pressure within the dyke during the tidal change is obtained using a computer program, FLUMP, which is incorporated with saturated-unsaturated and transient flow. The results show that the variation of free water surface and distribution of pore water pressure within the dyke during the tidal fluctuations can be clearly predicted with the computer program. When a tide is lowered to the minimum level, the predicted pressure head is higher than the level of the free water surface in some parts of the dyke; that is, excess pore water pressure is generated in a zone affected by the tidal change. Also an unsaturated zone which shows negative pore water pressure is temporally created when a tide is lowered. The shear strength of the zone can be predicted based on the proposal suggested by Fredlund et al. It is emphasized that the excess pore water pressure generated during tidal fluctuations and strength parameters for the unsaturated zone should be considered in analyzing the slope stability of dykes. When those are considered, the critical slip surface seems to be located below the free water surface obtained when a tide is at the lowest.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.5
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• pp.559-564
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• 2015

Distribution basins are used widely in the water treatment process. Uniform distribution at the distribution basin is an important because it affect precipitation efficiency of sedimentation basin. Generally distribution basin has a free surface water and is consisted of a weir. Study result, when inflow of distribution basin is less, amount of overflow is much at the nearest weir from the inlet. But when inflow is much, amount of overflow is much at the far weir from the inlet. The difference of distribution amount at the pipe is affected by the curvature and length of the pipe. The magnitude of the effect is determined by the relative energy loss and the flow state of the distribution basin. Optimization of the response surface method for minimizing an amount of deviation of the distribution is a very useful technique to determine the optimal ratio of the valve opening.

• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.285-291
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• 2010

To provide required flow rates of cooling or circulating water properly, approach flow conditions of vertical pump systems should be in compliance with state of the art acceptance criteria. The direct inflow should be vortex free, with low pre-rotation and symmetric velocity distribution. Physical model investigations are common practice and the best tool of prediction to evaluate, to optimize and to document flow conditions inside intake structures for vertical pumping systems. Optimization steps should be accomplished with respect to installation costs and complexity on site. The report shows evaluation of various approach flow conditions inside a compact waste water pumping station. The focus is on the occurrence of free surface vortices and the evaluation of air entrainment for various water level and flow rates. The presentation of the results includes the description of the investigated intake structure, occurring flow problems and final recommendations.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.303-307
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• 2001

Operation conditions to maximize the hydrolysis of beef tallow was investigated by using the response surface method. In the response surface analysis, reaction temperature, pressure, and ratio of fat to water was considered as independent variables. The concentrations of triglycerides. diglycerides, monoglycerides and free fatty acids were considered as dependent. variables. The optimum conditions for the hydrolysis was as follows' the reaction temperature was $271^{\circ}C$, pressure 86 bar and ratio of fat to water was 106.08g / 133.93 g. The maximum concentration of free fatty acids was 96.49 % at these optimum conditions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.286-288
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• 2014

This study deals with the catalyst free radio frequency plasma assisted polymerization of ethylene glycol using nitrogen as reactive gas to modify the surface chemistry and morphology. The deposited film was characterized through various analysis techniques i.e. surface profilometry, Forier transform infrared spectroscopy, water contact angle and UV-visible spectroscopy to analyze film thickness, chemical structure, surface energy and optical properties respectively. The surface topography was analyzed by Atomic force microscopy. It was observed that the ethylene oxide behaviour and optical transmittance of the film were reduced with the introduction of nitrogen gas due to higher fragmentation of monomer. However the hydrophilic behavior of the film improved due to formation of new water loving functional groups suitable for biomedical applications.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.323-337
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• 2015

Membrane Fouling was considered as major drawback in various industrial applications. Thus, this paper reviews the surface modification of polyethersulfone (PES) membranes for antifouling performance. Various modification techniques clearly indicate that hydrophilicity has to improve on the PES membrane surface. Moreover, the mechanism of fouling reduction with corresponds to various modification methods is widely discussed. Incorporation of hydrophilic functional groups on PES membrane surface enhances the surface free energy thereby which reduces the fouling. Characterization techniques adopted for the surface modified membranes was also discussed. These studies might be useful for the other researchers to utilize the modification technique for the applications of waste water treatment, chemical process industry and food industry.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.124.2-124
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• 2002

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2016.09a
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• pp.215-218
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• 2016