• Macromolecular Research
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• v.17 no.12
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• pp.943-949
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• 2009

A highly dispersed W/O emulsion of silicone oil (cyclomethicone)/water system was prepared with a nonionic surfactant. The surface and interfacial tension between the oil and water were characterized in terms of the droplet size distribution and viscosity change of the emulsion. When the dispersed phase concentration was relatively high, the viscosity of the emulsion was rapidly increased and the droplet size of the emulsion was decreased. The rheological behavior of the emulsion system showed non-Newtonian and shear thinning phenomena depending upon the content of the dispersed phase. The droplet size of the emulsion was decreased with increasing surfactant content and water concentration. The relative viscosity of the emulsion was better predicted with the Choi-Schowalter model than with the Taylor model. The value of the complex modulus increased with increasing surfactant concentration. The linear viscoelastic region was expanded with a dispersed phase concentration. According to the change in the viscosity, the behavior was classified into three distinct regions: [I] linear viscoelastic, [II] partially viscoelastic, and [III] viscous. The creep/recovery behaviors in each region were characterized.

• Membrane Journal
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• v.19 no.2
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• pp.122-128
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• 2009

We prepared monodispersed spherical silica microgels by controlling various conditions of emulsification procedure using a lab-scale membrane emulsification system equipped with SPG (Shirasu porous glass) porous membrane having pore size of $1.5{\mu}m$. We determined the effects of process parameters of membrane emulsification (ratio of dispersed phase to continuous phase, sodium silicate concentration, emulsifier concentration, dispersed phase pressure, stirring speed) on the mean size and size distribution of silica microgels. The increase of the ratio of dispersed phase to continuous phase, dispersed phase pressure and sodium silicate concentration led to the increase in the mean size of microgels. On the contrary, the increase in emulsifier concentration and stirring speed of the continuous phase caused the reduction of the mean size of microgels. Through controlling these parameters, monodisperse spherical silica microgels with about $6{\mu}m$ of the mean size were finally prepared.

• Journal of Pharmaceutical Investigation
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• v.20 no.2
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• pp.79-88
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• 1990

A numerical model for diffusion and dissolution controlled transport from dispersed matrix is presented. The rate controlling process for transport is considered to be diffusion of drug through a concentration gradient coupled with time-dependent surface change and/or disappearance of the dispersed drug in response to the dissolution. The transport behavior of drug was explained in terms of ${\nu}$ parameter: ${\nu}$ value means a ratio of diffusion time constant and dissolution time constant. This general model has wide range of application from where release is controlled by the diffusion rate to where release is governed by the dissolution rate. Based on this model, theoretical drug concentration, particle size distributions in the polymer matrix system and the resulting release rate were also investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.922-927
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• 2001

Single-layer green ELs was fabricated with using molecularly-dispersed Bu-PBD into poly-N-vinylcarbazole(PVK) which has low operating voltage and high quantum efficiency. A EL cell structure of glass substrate/indium-tin-oxide/PVK:Bu-PBD:C6(∼ 100nm)/Ca(20nm)/Al(20nm) was employed with variable doping concentration. The keys to obtain high quantum efficiency was excellent film forming capability of molecularly dispersed into PVK and appropriate combination of cathode for avoiding exciplex. We obtained the turn-on voltage of 4.2V and quantum efficiency of 0.52% at 0.lmol% of C6 concentration which has been improved about a factor of 50 in comparison with the undoped cell. The PL peak wavelengths wouldn\`t be turned by changing the concentration of the C6 dopant. Green EL emission peak and FWHM were 520nm and 70nm respectively. PL emission peak was obtained at 495nm.

• Macromolecular Research
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• v.12 no.2
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• pp.225-232
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• 2004

We have successfully synthesized relatively monodisperse and cross-linked melamine-formaldehyde (M-F) microspheres by dispersed polycondensation and subsequent pH adjustment with serum replacement cleaning. The average particle sizes (equation omitted): weight-average and (equation omitted) : number-average), the polydispersity index (equation omitted), the number of particles N$\_$p/ and the gel content of the M-F microspheres were observed by varying the pH, the surfactant concentration, and the polymerization temperature. We observed that both the pH and the polymerization temperature were predominant factors in determining (equation omitted) and N$\_$p/, but the effect that the temperature and pH had on the gel content ( ＞ 94% for all samples) was negligible. The exponents of the slopes of plots of N$\_$p/ versus pH and surfactant concentration were －10 and 0.6, respectively. Particle nucleation and growth were achieved within short periods; the incessant coagulation occurred even in the presence of surfactants.

• Environmental Engineering Research
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• v.22 no.3
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• pp.245-254
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• 2017

This study investigates methyl orange (MO) degradation by an ultrasonically dispersed nano-metallic particle (NMP) assisted advanced Fenton process. The NMPs were synthesized from the leachate of automobile-shredder residue. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were performed for the prepared NMPs. Various parameters, such as the effects of the NMP dosage, the pH value of the solution, the initial concentration of MO, and the amount of $H_2O_2$ on the degradation efficiency of MO were studied. The MO degradation efficiency could be increased by approximately 100% by increasing the dosages of the NMPs and $H_2O_2$ to certain limits, after which in both cases the degradation efficiency was reduced when an excess amount was added. The MO degradation efficiency was found to be 100% at pH 2.0 and 2.5 with the 10 mg/L of initial concentration of the MO. The degradation of MO by ultrasonically dispersed NMPs was appropriate with the pseudo-first-order kinetics.

• Journal of the Economic Geographical Society of Korea
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• v.14 no.4
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• pp.671-683
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• 2011

The technical development of transportation and communication increases freedom of location choice. This higher freedom allows to company can pursues bigger profit than before. Company's separated spatial configurations tend to go to most optimal location, so some places showed unexpected agglomeration. This study conducted to prove "dispersed concentration" for specific example, pharmaceutical enterprises, in real business world. As a result, separation of spatial configuration clearly observed as product output goes bigger and R&D's depth goes deeper. And spatial concentration of each function was found. Most headquarters are located in Seoul, R&D centers make agglomeration at some spaces. Plants' location concentrated until 1990s, but, in 2000s, plants expand out of metropolitan area.

• YAKHAK HOEJI
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• v.39 no.1
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• pp.68-77
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• 1995

Aluminum magnesium silicate was synthesized by reacting the mixed solutions of sodium aluminate and magnesium chloride with sodium silicate solution in this study. The optimal synthesis conditions based on the yield of the product has been attained according to Box-Wilson experimental design. It was found that the optimal synthetic conditions of aluminum magnesium silicate were as follows: Reaction temperature=$69~81^{\circ}C$; concentration of two reactants, sodium aluminate and magnesium chloride= 13.95~14.44 w/w%; molar concentration ratio of the two reactants, [NaAlO$_{2}$]/MgCl$_{2}$]=3.63~4.00; reaction time= 12~15 min; drying temp. of the product=$70~76^{\circ}C$. Aluminum magnesium silicate synthesized under the optimal synthesis condition was dispersed in 0.75, 1.0 and 1.5w/w% aqueous solution or suspension of six dispersing agents, and the Theological properties of the dispersed systems prepared have been investigated at $15^{\circ}C$ and $25^{\circ}C$ using Brookfield LVT Type Viscometer. The acid-consuming capacity of the most excellent product was 272~278 ml of 0.1N-HCl per gram of the antacid. The flow types of 5.0 w/w% aluminum magnesium silicate suspension were dependent upon the kind and concentration of dispersing agents added. The apparent viscosity of the suspension was generally increased with concentration of dispersing agents and was not significantly changed or decreased as the temperature was raised. A dispersing agent, hydroxypropyl cellulose suspension, exhibited an unique flow behavior of antithixotropy. The flow behavior of the suspension dispersed in a given dispersing agent not always coincided with that of the dispersing agent solution or suspension itself.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.296-298
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• 2005

Hydrogen generation by the hydrolysis of aqueous sodium borohydride $(NaBH_4)$ solutions was studied using IRA-400 anion resin dispersed Pt. Ru catalysts and Lithium Cobalt oxide $(LiCoO_2)$ supported Pt, Ru and PtRu catalysts. The performance of the $LiCoO_2$ supported catalysts is better than the ion exchange resin dispersed catalysts. There is a marked concentration dependence on the performance of the $LiCoO_2$ supported catalysts and the hydrogen generation rate goes down if the borohydride concentration is increased beyond $10\%$. The efficiency of PtRu- $LiCoO_2$ is almost double that of either Ru-$LiCoO_2$ or Pt-$LiCoO_2$ for $NaBH_4$ concentrations up to $10\%$.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.577-583
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• 2011

Stabilized biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) were prepared by controlled coprecipitation method for hyperthermia application. ESR measurements determined that all of the interactions in the individual SPIONs (1 nm and 11 nm) were antiferromagnetic in nature because the ions contributed to the magnetization with a range of magnetic moments. In-situ monitoring of the temperature increment was performed, showing that the microwave absorption rate of the SPIONs was dispersed in an appropriate host media (polar or non-polar solvents) during microwave irradiation. Microwave absorption energy rates and heat loss of SPIONs in solvent were calculated by non-linear data fitting with an energy balance equation. The microwave absorption rates of SPIONs dispersed in solvent linearly increases when the concentration of SPIONs increases, implying that the microwave absorption rate can be tunable by changing the concentration of SPIONs.