• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.187-193
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• 2007

Reynolds and Froude numbers, along with tracer tests, have been widely used to estimate hydrodynamics in full-scale horizontal sedimentation basin in water treatment plants (WTPs). In spite of this, the former numbers do not reflect actual operating conditions, instead most often being based on the dimensions of the structures. The index and graphic analyses most often used were found to be too subjective to accurately analyze tracer test results. In order to overcome these limitations, dispersion number was applied for analysis of tracer test results. Tracer tests were conducted in eight full-scale sedimentation basins in six WTPs, and then analyzed by index and graphic analyses as well as by dispersion number. The dispersion number was more useful as an indicator of the hydrodynamic behavior in the basin. It was also found that as dispersion number decreased, flow approached the ideal for plug flow in which case, higher sedimentation efficiency could be expected.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.22-27
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• 2006

This paper describes the development of the stream-tube based dispersion model for modeling contaminant transport in open channels. The operator-splitting technique is employed to separate the 2D contaminant transport equation into the pure advection and pure dispersion equations. Then the total variation diminishing (TVD) schemes are combined with the second-order Lax-Wendroff and third-order QUICKEST explicit finite difference schemes respectively to solve the pure advection equation in order to prevent the occurrence of numerical oscillations. Due to various limiters owning different features, the numerical tests for 1D pure advection and 2D dispersion are conducted to evaluate the performance of different TVD schemes firstly, then the TVD schemes are applied to experimental data for simulating the 2D mixing in a straight trapezoidal channel to test the model capability. Both the numerical tests and model application show that the TVD schemes are very competent for solving the advection-dominated transport problems.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.639-647
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• 1999

Experimental methods of plume dispersion in convective boundary layer using a composite turbulence water tank have been established through (ⅰ) manufacturing of water tank system, (ⅱ) providing of tracer whose volatility is relatively low, (ⅲ) development of software for image processing of dispersed particles in fluid, and (ⅳ) application of appropriate similarity law. Using these methods, the vertical dispersion coefficient $$\sigma$_2$ at long distances on mesoscale and the centerline height $Z_c$ of plumes have been measured. Measurement of $$\sigma$_2$ have been validated through comparison with CONDORS field experiments, and analysed with respect to the intensity of heat flux and mechanical turbulence as well as plume release height. Downwind distance where plume center height approaches to final level has also been analysed in respect of these three parameters.

• Water for future
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• v.28 no.4
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• pp.195-204
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• 1995

New dispersion coefficient equation which can be used to estimate dispersion coefficient by using only hydraulic data easily obtained in natural streams has been developed. Dimensional analysis was performed to select physically meaningful parameters, One-Step Huber method, which is one of the nonlinear multi-regression method, was applied to derive a regression equation of dispersion coefficient. 59 measured hydraulic data which were collected in 26 streams in the United States and were analyzed in the Part I of this study, were used in developing new dispersion coefficient equation. Among 59 measured data sets, 35 data sets were used in deriving regression equation, and 24 data sets are used for verification. The new dispersion coefficient equation, which has been developed in this study was proven to be superior in explaining dispersion characteristics of natural streams more precisely compared to existing dispersion coefficient equations.

• Textile Coloration and Finishing
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• v.29 no.4
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• pp.195-201
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• 2017

To study the effect of oxyfluorination on water dispersion of phthalocyanine blue(C.I. pigment blue 15:3), the pigment was oxyfluorinated using various oxygen to fluorine ratio of the reactant gas. After the oxyfluorination of the phthalocyanine blue pigment, no significant change in FT-IR spectra was observed, whereas XPS spectra showed the introduction of oxygen and fluorine containing functional groups. This suggests that the oxyfluorination of the pigment only occurred on the surface of the pigment particle and resulted in no significant change in UV-Vis spectra of the pigment. However, the oxyflurinated pigments showed improved water dispersion, compared to the non-treated pigment. Especially, when the oxygen to fluorine ratio was 47:3, the water dispersion of the oxyfluorinated pigments significantly increased, compared to the non-treated pigments. This suggests that the oxyfluorination of the phthalocyanine blue pigment has a potential to be used as a water dispersion improving method.

• Composites Research
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• v.35 no.1
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• pp.18-22
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• 2022

Dispersion is one of the most important factors in the manufacture of composite materials. In the manufacture of composite materials, solvents are used to better disperse the reinforcement, nano-filler in the matrix. Since dispersion is affected with solvents, it is necessary to study which solvent is adopted to get good dispersion. In this study, the dispersion behavior and solubility of graphene oxide(GO) were examined under various solvents (DMF, NMP, ethylene glycol, Acetone, DI water) to identify dispersion. As a result of UV-Vis spectroscopy absorbance measurement, it was found that DMF and ethylene glycol had the best dispersibility, whereas DI water showed the lowest dispersibility. In addition, as a result of visually observing the dispersion according to the surface tension and time, it was found that the dispersibility was excellent in the order of DI water, ethylene glycol, NMP, DMF, and acetone, which was consistent with the Hansen solubility parameter value.

• Journal of Pharmaceutical Investigation
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• v.41 no.4
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• pp.239-247
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• 2011

Simvastatin is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which catalyzes the conversion of HMG-CoA to mevalonate, an early and rate-limiting step in the biosynthesis of cholesterol. Simvastatin has good permeability, but it also has low solubility (BCS class II), which reduces its bioavailability. To overcome this problem, a solid dispersion is formed using a spray-dryer with polymeric material carrier to potentially enhance the dissolution rate and extend drug absorption. As carriers for solid dispersion, Gelucire$^{(R)}$44/14 and Gelucire$^{(R)}$ 50/13 are semisolid excipients that greatly improve the bioavailability of poorly-soluble drugs. To avoid any toxic effects of an organic solvent, we used aqueous medium to melt Tween$^{(R)}$ 80 and distilled water. The structural behaviors of the raw materials and the solid dispersion were analyzed by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The DSC and PXRD data indicated that the crystalline structure of simvastatin was transformed to an amorphous structure through solid dispersion. Then, solid dispersion-based tablets containing 20 mg simvastatin were prepared with excipients. Dissolution tests were performed in distilled water and artificial intestinal fluid using the USP paddle II method. Compared with that of the commercial tablet (Zocor$^{(R)}$ 20 mg), the release of simvastatin from solid dispersion based-tablet was more efficient. Although the stability study is not complete, this solid dispersion system is expected to deliver poorly water-soluble drugs with enhanced bioavailability and less toxicity.

• Journal of the Korean Society of Marine Environment & Safety
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• v.6 no.1
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• pp.47-55
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• 2000

A three-dimensional digital image processing technique is proposed to quantitatively predict the dispersion phenomena of oil droplet onto the surface of the water. This technique is able to get the dispersion rate of an oil droplet three-dimensionally just below the surface of the water over time. The obtained dispersion rate obtained through this technique is informative to the investigation into the relationship among the gravity, surface tensions between oil, water, and air. This technique is based upon the three-dimensional PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a three CCD(Charge Coupled Device) cameras, an image grabber, and a host computer in which an image processing algorithm is adopted for the acquisition of dispersion rate oil an oil droplet.

• Macromolecular Research
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• v.10 no.3
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• pp.140-144
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• 2002

Dispersion polymerization of acrylamide was carried out in the media of methyl alcohol/$H_2O$ mixtures using hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively. The effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, methyl alcohol/$H_2O$ ratio, and purification of monomer and nitrogen purge on the particle size of the latices and molecular weight of the polymers were investigated. The average particle diameter increased with increasing concentration of initiator, water content in methyl alcohol/$H_2O$ media, and polymerization temperature, but decreased with monomer and stabilizer concentrations. The viscosity average molecular weight increased with increasing concentrations of monomer, steric stabilizer, and water content in dispersion media, but decreased with initiator concentration and polymerization temperature. The PAM polymers prepared with the purified monomer and the nitrogen purging before the reaction showed the highest molecular weight.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.33-40
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• 2000

Dispersion of high temperature and high salinity water discharged from a desalination plant is numerically estimated to investigate its impact on marine environment. The plant is installed on a floating barge located in Jinhae Bay and takes 200 tons of seawater per day. Fifty tons of intake are changed into fresh water, while 150 tons of those are discharged as the water of 15℃ warmer and 1.33 times saltier than surrounding seawater. In this dispersion model, advection is described by two-dimensional tidal currents and turbulent diffusion is simulated by Monte Carlo technique. Decay of water temperature is modelled by heat exchange between the atmosphere and the ocean, while decay of water salinity is ignored. The distributions of temperature and salinity come to equilibrium when the dispersion model is run for 100 days for temperature and for 365 days for salinity, respectively. At equilibrium state the water temperature and salinity rise 0.01℃ and 0.001‰ higher than ambient seawater, respectively.