• Advances in nano research
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• v.9 no.1
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• pp.59-67
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• 2020

Filter cake formation during rotary drilling operation is an unavoidable scenario, hence there is need for constant improvement in the approaches used in monitoring the cake thickness growth in order to prevent drill-string sticking. This study proposes an improved model that predicts the growth of mud cake thickness overtime with the consideration of the addition of nanoparticles in the formulated drilling fluid system. Ferric oxide, titanium dioxide and copper oxide nanoparticles were used in varying amounts (2 g, 4 g and 6 g), and filtration data were obtained from the HPHT filtration test. The filter cakes formed were further analyzed with scanning electron microscope to obtain the morphological characteristics. The data obtained was used to validate the new filtrate loss model. This model specifically presents the concept of time variation in filter cake formation as against the previous works of constant and definite time. Regression coefficient which is a statistical measure was used to validate the new model and the predicted results were compared with the API model. The new model showed R² values of 99.9%, and the predictions from the proposed filtration model can be said to be more closely related to the experimental data than that predicted from the API model from the SSE and RMSE results.

• Fire Science and Engineering
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• v.23 no.2
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• pp.78-84
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• 2009

We carried out fire extinguishing experiments with three kinds of water mist nozzle system. Fire extinguishing experiment according to installed nozzle height and fuel pan location was done. And fire extinguishing performance was compared with plain water and foam agent mixed solution. Water mist nozzle height was varied with 4m, 3.5m and 3m and position of fuel fan was varied 0.5m and 1m from the center of water mist nozzle. Foam agent that used in this experiment is 3% type of AFFF (Aqueous Film Forming Foam) solution. Experimental result showed the door opening effect was little. Fire extinguishing performance of foam agent mixture water mist was better than the plain water mist only.

• The Korean Journal of Zoology
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• v.7 no.1
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• pp.1-5
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• 1964

GamnH-irradiated aqueous solutions of triglycine were studied using low voltage electrophoresis, paper chromatography, and determination of carbonyl compound. Four generalizations can be made as follows: 1. One component from irradiated triglycine formed a complex with copper ions and had higher electronegativity than did triglycine. 2. Five components from irradiated triglycine were separated by paper chromatography; of these, two were identified. 3. Carbonyl compound formation in irradiated triglycine increased up to $5{\times}10^{20}\;ev/ml$ and decreased at higher doses up to $1.9{\times}10^{21}\;ev/ml$ indicating its participation in secondary reaction in the complex system. 4. The possibility of hydrolytic brcabtgc of peptide bond was indicated by the separation of glycine from irradiated triglycine.lycine.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.261-267
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• 1998

We have investigated the stability of macroemulsions of AOT prepared from Winsor systems. The emulsion system was prepared from heptane+aqueous NaCl+AOT. As the concentration of NaCl increases, the stability of the emulsion increases, reaches a maximum, and then decreases. At low salt concentration the creaming occurred due to density difference of oil and aqueous phases. We developed a model for the creaming. Behavior of the emulsions containing low salt could be described very well by the model, however, at high salt concentration the electrostatic repulsion decreased due to screening and droplets started to attract each other and the stability of the emulsion decreased.

• Journal of Pharmaceutical Investigation
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• v.41 no.2
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• pp.75-82
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• 2011

LB71350 is an HIV protease inhibitor with poor aqueous solubility and extensive first pass effect. The purpose of the present study was to test the feasibility of solid dosage form of LB71350 with improved bioavailability utilizing solid dispersion. Three different compositions with varying ratio of (LB71350: Gelucire 44/14: Tween 20) were studied. Capsule filling of these solid dispersion compositions was tested using a semi-automatic capsule filling system. Oral bioavailability in dog was tested. Chemical and physical stability at 4, 25 and $40^{\circ}C$ was monitored by HPLC assay, dissolution test, powder XRD and microscopy. The capsule filling system yielded uniform products of drug loading up to 10%. Oral bioavailability in dog was improved compared to the aqueous suspension of crystalline LB71350. Capsules were chemically stable for up to 6 months at $40^{\circ}C$. However, there were temperature and composition dependent physical changes. Decrease in dissolution rates after storage at $40^{\circ}C$ was due to the polymorphic change. In conclusion, manufacturing process, bioavailability, and physico-chemical stability have been considered to propose a solid dispersion capsule formulation for the HIV protease inhibitor with poor physico-chemical properties. A new less soluble crystalline form identified during the physical stability test warrants further study.

• YAKHAK HOEJI
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• v.49 no.4
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• pp.268-274
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• 2005

Paclitaxel is an effective antineoplastic agent against ovarian, colon and breast tumors. But there have been many difficulties to formulate this drug due to the extremely low aqueous solubility. Paclitaxel is currently formulated in a vehicle composed of Cremophor EL and absolute ethanol mixture which is $5\~20$ fold diluted in normal saline or $5\%$ dextrose solution before I.V. injection. However, this formulation has many problems such as allergic reactions and drug precipitation on aqueous dilution. To overcome these problems, we prepared the micelle and microemulsion systems for parenteral administration of paclitaxel by using glycofurol, $Soluto^{(R)}lHS$ 15 and oleic acid. Phase diagram, pH-rate stability, particle size distributions and pharmacokinetics of the systems were studied. Micelles and microemulsions formulated as nano-particle delivery system were physically and chemically stable. Therefore, these formulations might be the promising alternative candidate for the parenteral delivery of paclitaxel.

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.143-149
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• 1995

At low concentration a simplified model of organic dye-surfactant system has been used to evaluate. By applying the resultant three parameter equation to the experimental data, values for the equilibrium constants for the ion-pair formation $(K_O)$, surfactant molecule addition to aggregates $(K_S)$ and dye aggregation reactions $(K_D)$ could be calculated and changes of free energy have obtained from its values. $K_O$ and K_S$ values were larger than those expected electrostatic interaction indicatihng a hydrophobic contribution and the $K_D$ values were about 10~20 times higher than those found for association in pure aqueous solutions which can be ascribed to the screening effect of the electrostatic repulsion.

• Journal of the Korean Ceramic Society
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• v.31 no.7
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• pp.723-730
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• 1994

Stable aqueous dispersion of magnetite colloid was obtained by allowing a fatty acid, such as nonanoic acid, decanoic acid and undecanoic acid, dissociated with NH4OH solution to adsorb on the monomolecular adsorption of oleate. To obtain a stable dispersion, added amounts of sodium oleate and nonanoic acid for magnetite 20g were more than 2.63$\times$10-2 mol and 0.04 mol respectively. In this colloid, good dispersions of magnetite which is sterically stabilized in aqueous system were achieved about pH 7.7. Water-based magnetic fluids using in this study were able to redisperse to water-based magnetic fluids by adding NH4OH solution to dried water-based magnetic fluid powders. Changing a magnetic fluid carrier such as kerosene was also attemped by adding kerosene to dried water-based magnetic fluid powders. In this study, we can obtain a kerosene-based magnetic fluids using drying process.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.436-442
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• 2008

Organic-inorganic hybrid mesoporous anion-exchange resins were prepared for the adsorption of anions from aqueous solutions. The prepared samples were characterized using nitrogen adsorption-desorption measurements, Fourier transform infrared (FTIR) spectroscopy, and elemental analyses. Batch and kinetic experiments were performed to examine the anion-exchange performances of the prepared samples. Among the prepared samples, the hybrid mesoporous anion-exchange resins functionalized with tributylammonium groups showed higher adsorption capacities for perrhenate ions than did the resin functionalized with trimethylammonium groups. The surfactant, hexadecylamine, which had hydrophobic alkyl chains, also showed affinity for hydrophobic perrhenate anions.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1208-1212
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• 2003

CaCO$_3$ powders were synthesized by aqueous solution reaction of CaC1$_2$ㆍ2$H_2O$-(NH$_4$)$_2$CO$_3$ system with NH$_4$OH at 45$^{\circ}C$ and pHs 8, 9, 10, and 11 and in the concentration range of 0.1∼5 M and its polymorphism, morphology and size were investigated. In order to investigate the influence of pH on nucleation, pH was adjusted before and after reaction respectively. When pH was adjusted after reaction a formation ratio of vaterite was increased with increasing pH and concentration but vaterite was formed with calcite. But, when pH was adjusted before reaction, the formation rate of vaterite was increased with increasing pH and concentration. resulting in a phase-pure vaterite with a spherical shape and 2∼5 $\mu\textrm{m}$ in size. It was found that solubility of alkaline vaterite was decreased with increasing OH- ions in the high pH solution. When pH was adjusted before nucleation in the high concentration range, in particular, decreasing of solubility disturbed transformation of initially formed numerous vaterite to calcite.