• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.657-662
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• 2004

The kinetics of oxidation and disappearance of graphite in MgO-C refractories containing TiC were, in the temperature range from 1000 to 1200$^{\circ}C$, investigated to enhance the oxdation resistance of MgO-C refractproes. The air was blown into the furnace at flow rate of 0.2 litters per minute, and then weight decrease was measured with a thermo balance at 30 seconds intervals until the value of weight became unchanged. The value of effective diffusion coefficient (De) for the specimen of MgO-C was 1.39${\times}$10$\^$-4/ ㎡/sec. The diffusion of oxygen through decarburized layer was the rate deforming step in the overall oxidation process under present experimental conditions. The TiC additions enhanced the oxidation resistance of the MgO-C refractories.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.821-828
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• 2005

To investigate the role of RH and temperature on the transport of chloride in the concrete, two groups of specimens were configured. For both groups, mix design was based on w/c=0.45, $400kg/m^3$ cement, $794kg/m^3$ fine aggregate and $858kg/m^3$ coarse aggregate. After specimen fabrication these were exposed to four different RH (35, 55, 75 and $95\%$ RH) and temperature (0, 20, 30 and $40^{\circ}C$) conditions. After 3 and 6 months $15\%$ NaCl exposure 5mm cores were taken. These cores were sliced and individual cores were ground to powder. In addition, to evaluate the effect of temperature on the chloride binding some powder samples were leached in the each of four temperature chambers. Chloride titration fur these was performed using FDOT acid titration method. Based upon the resultant data conclusions were reached regarding that 1) effective diffusion coefficient, $D_e$, increased with increasing exposure RH, suggesting that the size and number of water paths increased with elevated moisture content in the specimens, 2) $D_e$ increased with increasing temperature in the range of 0 to $40^{\circ}C$ possibly by elevated thermal activation of chloride ions and reduced chloride binding at higher temperature, 3) water soluble chloride concentration, $[Cl^-]_s$, increased with increasing temperature, and 4) chloride concentration profile for initially dry concrete specimens was higher than for the initially wet ones indicating pronounced capillary suction (sorption) occurred for the dry concrete specimens.

• Geomechanics and Engineering
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• v.21 no.4
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• pp.357-369
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• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• Imaging Science in Dentistry
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• v.49 no.1
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• pp.53-58
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• 2019

Purpose: To present characteristic findings of Tc-99m hydroxymethylene diphosphonate (HMDP) scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging for osteonecrosis in the mandible, especially osteoradionecrosis(ORN) and medication-related osteonecrosis of the jaw(MRONJ). Materials and Methods: Thirteen patients with MRONJ and 7 patients with ORN in the mandible underwent Tc-99m HMDP scintigraphy, CT, and MR imaging (T1-weighted images[T1WI], T2-weighted images[T2WI], short inversion time inversion recovery images[STIR]), diffusion-weighted images[DWI], and apparent diffusion coefficient [ADC] mapping). The associations of scintigraphy, CT, and MR imaging findings with MRONJ and ORN were analyzed using the chi-square test with the Pearson exact test. Results: Thirteen patients with MRONJ and 7 patients with ORN in the mandible showed low signal intensity on T1WI and ADC mapping, high signal intensity on STIR and DWI, and increased uptake on scintigraphy. Periosteal bone proliferation on CT was observed in 69.2% of patients with MRONJ(9 of 13) versus 14.3% of patients with ORN(1 of 7)(P=0.019). Conclusion: This study presented characteristic imaging findings of MRONJ and ORN on scintigraphy, CT, and MR imaging. Our results suggest that CT can be effective for detecting MRONJ and ORN.

• Food Engineering Progress
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• v.23 no.1
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• pp.7-15
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• 2019

The impregnation of solid foods into the surrounding hypotonic or hypertonic solution was explored as a method to infuse NaCl in pork loin cube without altering its matrix. Mass transfer kinetics using a diffusive model as the mathematical model for moisture gain/loss and salt gain and the resulting textural properties were studied for the surrounding solutions of NaCl 2.5, 5.0, 10.0 and 15% (w/w). It was possible to access the effects of brine concentration on the direction of the resulting water flow, quantify water and salt transfer, and confirm tenderization effect by salt infusion. For brine concentrations up to 10% it was verified that meat samples gained water, while for processes with 15% concentration, pork loin cubes lost water. The effective diffusion coefficients of salt ranged from 2.43×10^-9 to 3.53×10^-9 m²/s, while for the values of water ranged from 1.22×10^-9 to 1.88×10^-9 m²/s. The diffusive model was able to represent well salt gain rates using a single parameter, i.e. an effective diffusion coefficient of salt through the meat. However, it was not possible to find a characteristic effective diffusion coefficient for water transfer. Within the range of experimental conditions studied, salt-impregnated samples by 5% (w/w) brine were shown with minimum hardness, chewiness and shear force.

• Journal of Photoscience
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• v.10 no.2
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• pp.199-202
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• 2003

The relationship between the morphology of nanostructured TiO$_2$ films and the photo-injected electron transport has been investigated using intensity-modulated photocurrent spectroscopy (IMPS). For this purpose, three different TiO$_2$ films with 5 ${\mu}{\textrm}{m}$ thickness are prepared: The rutile TiO$_2$ film with 500 nm-sized cluster-like spherical bundles composed of the individual needles (Tl), the rutile TiO$_2$ film made up of non-oriented, homogeneously distributed rod-shaped particles having a dimension of approximately 20${\times}$80 nm (T2), and the anatase TiO$_2$ film with 20 nm-sized spherically shaped particles (T3). Cross sectional scanning electron micrographs show that all of the TiO$_2$films have a quite different particle packing density: poorly packed Tl film, loosely packed T2 film and densely packed T3 film. The electron transport is found to be significantly influenced by film morphology. The effective electron diffusion coefficient D$_{eff}$ derived from the IMPS time constant is an order of magnitude lower for T2 than for T3, but the D$_{eff}$ for the Tl sample is much lower than T2. These differences in the rate of electron transport are ascribed to differences in the extent of interparticle connectivity associated with the particle packing density.ity.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.515-521
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• 2020

Organic-inorganic hybrid perovskite nanocrystals have attracted a lot of attention owing to their excellent optical properties such as high absorption coefficient, high diffusion length, and photoluminescence quantum yield in optoelectronic applications. Despite the many advantages of optoelectronic materials, understanding on how these materials interact with their environments is still lacking. In this study, the fluorescence properties of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanoparticles are investigated for the detection of volatile organic compounds (VOCs) and aliphatic amines (monoethylamine, diethylamine, and trimethylamine). In particular, colloidal MAPbBr₃ nanoparticles demonstrate a high selectivity in response to diethylamine, in which a significant photoluminescence (PL) quenching (~ 100 %) is observed at a concentration of 100 ppm. This selectivity to the aliphatic amines may originate from the relative size of the amine molecules that must be accommodated in the perovskite crystals structure with a narrow range of tolerance factor. Sensitive PL response of MAPbBr₃ nanocrystals suggests a simple and effective strategy for colorimetric and fluorescence sensing of aliphatic amines in organic solution phase.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.382-387
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• 1999

The processes and the kinetics of the lithium intercalation into the spin coated $V_2O_5$ xerogel prepared by the sol-gel processing have been studied employing impedance analyzer. Homogeneous and quasi-isotropic thin films of the xerogel can be obtained as a result of random distribution of the $V_2O_5$ gels on the substrate by the use of the spin coating. Effective diffusion coefficient and charge transfer resistance vary more than one order of magnitude at high and low lithium composition in $V_2O_5$ xerogel, respectively.

• Journal of Pharmaceutical Investigation
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• v.28 no.1
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• pp.43-50
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• 1998

Niosomes are vesicles formed from synthetic non-ionic surfactants, offering an alternative to chemically unstable and expensive liposomes as a drug carrier. Non-ionic surfactant and cholesterol mixture film leads to the formation of vesicular system by hydration with sonication method. The formation of niosome was ascertained by negative staining of TEM. The entrapment efficiency of niosomal suspension was gradually increased with increasing the ratio of cholesterol to surfactant. It was found that the niosome with 6 : 4 (polyoxyethylene 2-cetyl ether: cholesterol) ratio was more stable than those with other ratios. The topical application of acyclovir(ACV) in the treatment of herpes simplex virus type 1(HSV-1) skin disease has a long history. There are an increasing number of reports, however, in which topical ACV therapy is not as effective as oral administration. Lack of efficacy with topical ACV has been hypothesized to reflect the inadequate delivery of drug to the skin. We investigated the permeation of niosome containing $[^{3}H]ACV$ in hairless mouse skin using Franz diffusion cell model. Permeation coefficient(P) of aqueous ACV was $6.7{\times}10^{-4}\;(cm/hr)$ and that of ACV in niosome was $23.4{\times}10^{-4}\;(cm/hr)$, suggesting about 3.5 times increase in the transdermal permeation.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.329-335
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• 1999

Clenbuterol, a selective ${\beta}_2-adrenergic$ receptor stimulant, has been introduced as a potent bronchodilator for patients with bronchial asthma, chronic bronchitis and pulmonary emphysema. For the purpose of developing a transdermal preparation for clenbuterol, we attempted to select an optimal solvent system and permeation enhancer among fatty acids and fatty alcohols which are known to accelerate the penetration of various drugs in permeation experiments using hairless mouse skin and Franz diffusion cell. Apparent partition coefficient of clenbuterol was increased as pH of buffer solution was increased and solubility of clenbuterol was increased as the percent of propylene glycol(PG) in buffer solution(pH 10) was increased. Permeability of clenbuterol from different buffer(pH 10)/PG solvent mixtures was decreased as the percent of PG in pH 10 buffer solution was increased and among the various enhancers studied, lauryl alcohol was found to be the most effective enhancer, increasing the permeability of clenbuterol approximately 76-fold compared with control. Lauryl alcohol$(0{\sim}2%)$ enhanced the permeability of clenbuterol concentration-dependently. In this study, the optimal solvent system for the penetration of clenbuterol was found to be 50/50 buffer(pH 10)/PG solvent mixture containing 2% lauryl alcohol.