• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.109-114
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• 2012

This study is the things to experiment and evaluate the performance of self-healing water-proofing on the concrete to be using the crystal growth composite waterproofing admixture. The cylinder to be making on the concrete by ${\varnothing}150{\times}300$ mm for evaluating the performance of self-healing water-proofing was aging 90 days and cut on a 50 mm. So, it prompted the crack and applied. After it measured the quantity of water to be flow the water throughout the crack part of the cylinder, it applied the basic formular of Darcy's law and calculated the coefficient of water permeability. So, it verified the performance of self-healing water-proofing on the basis of the changing shape of the water permeability. This experiment is the thing to be applied the general evaluation of the structure to demand the real watertightness on doing for the evaluating of performance of the quantity of water leak and self-healing water-proofing about the various penetration crack.

• Journal of the Korean institute of surface engineering
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• v.50 no.2
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• pp.114-118
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• 2017

Bismuth telluride ($Bi_2Te_3$) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic $Bi_2Te_3$ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical $Bi_2Te_3$ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above $375^{\circ}C$ for 6h. The reduced $Bi_2Te_3$ powders have a mean particle size of $1.5{\mu}m$. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1305-1306
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• 2006

A monolayer assembly of anthracene-viologen linked thiol ($AMVC_{8}SH$) was fabricated on a gold electrode by self-assembly method. Structural property of the self-assembled monolayers (SAMs) was carried out by optical and electrochemical method. Firstly, we investigated PL spectrum and UV/visible absorption for the optical properties in solution state. Secondly, we determined the characteristics of charge transfer in different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the PL spectrum and UV/visible absorption were observed and the well-defined shape peaks were nearly equal charges during redox reactions and existed to an excellent linear relationship between the scan rates and existed to currents. The mass change was determined during redox reaction. The mass change behavior of SAMs was not only governed by the mobility of the ion in the viologen but the valence of the ion in the electrolyte solution.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.393-401
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• 1997

Commercial flake graphite cast iron substrate was coated with titanium powder by low pressure plasma spraying and was irradiated with a $CO_2$ laser to produce the wear resistant composite layer. From the experimental results of this study, it was possible to composite TiC particles on the surface layer by direct reaction between carbon existed in the cast iron matrix and titanium with thermal sprayed coating by remelting and alloying them using laser irradiation. The cooling rate of laser remelted cast iron substrate without titanium coating was about $1{\times}10^4$ K/s to $1{\times}10^5$ K/s in the order under the condition used in this study. The microstructure of alloyed layer consisted of three zones, that is, TiC particule crystallized zone (MHV $400{\sim}500$), the mixed zone of TiC particule+ledebulite (MHV $650{\sim}900$) and the ledebulite zone (MHV $500{\sim}700$). TiC particules were crystallized as a typical dendritic morphology. The secondary TiC dendrite arms were grown to the polygonized shape and were necking. And then the separated arms became cubic crystal of TiC at the slowly solidified zone. But in the rapidly solidified zone of fusion boundry, the fine granular TiC particules were grouped like grape.

• Korean Journal of Materials Research
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• v.30 no.7
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• pp.338-342
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• 2020

Tin oxide (SnO₂) nanocrystals are synthesized by a thermal evaporation method using a mixture of SnO₂ and Mg powders. The synthesis process is performed in air at atmospheric pressure, which makes the process very simple. Nanocrystals with a belt shape start to form at 900 ℃ lower than the melting point of SnO₂. As the synthesis temperature increases to 1,100 ℃, the quantity of nanocrystals increases. The size of the nanocrystals did not change with increasing temperature. When SnO₂ powder without Mg powder is used as the source material, no nanocrystals are synthesized even at 1,100 ℃, indicating that Mg plays an important role in the formation of the SnO₂ nanocrystals at temperatures as low as 900 ℃. X-ray diffraction analysis shows that the SnO₂ nanocrystals have a rutile crystal structure. The belt-shaped SnO₂ nanocrystals have a width of 300~800 nm, a thickness of 50 nm, and a length of several tens of micrometers. A strong blue emission peak centered at 410 nm is observed in the cathodoluminescence spectra of the belt-shaped SnO₂ nanocrystals.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.690-696
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• 2005

The ultrastructure ore of a nanostructured apatite film nucleated from solution was studied to gain insights into that of bone minerals which is the most important constituent to sustain the strength of bones. Needle-shaped apatite crystal plates with a bimodal size distribution $(\~100\;to\;\~1000 nm)$ were randomly distributed and they were found to grow parallel to the c-axis ([002]), driven by the reduction of surface energy. Between these randomly distributed needle-shaped apatite crystals which are parallel to the film, apatite crystals (20-40nm) with the normal of the grains quasi-perpendicular to the c-axis were observed. These observations suggest that the apatite film is the interwoven structure of apatite crystals with the c-axis parallel and quasi-perpendicular to the fan. In some regions, amorphous calcium phosphate, which is a precursor of apatite, was also observed. In the amorphous phase, small crystalline particle with the size of 2-3 nm were observed. These particles were quite similar, in size and shape, to those observed in the femoral trabecular bone, suggesting the nucleation of apatites by a biomimetic process in vitro is similar to that in vivo.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.249-253
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• 2014

Palladium on carbon catalysts for hexafluoropropylene hydrogenation were prepared using imidazolium hexafluorophosphate with various cation parts. The morphology of palladium was relatively affected by the cation parts of the ionic liquid. With increasing alkyl chains of the ionic liquid cation, the shape of palladium particle changed from spherical to cylindrical due to the effect of steric stabilization. After calcination at $500^{\circ}C$, all catalysts possessed the comparable crystal structure. Under the identical reaction conditions, the catalyst prepared using the ionic liquid with hexyl chain in cation parts showed the most effective reactivity.

• Bulletin of the Korean Chemical Society
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• v.11 no.1
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• pp.25-28
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• 1990

The superconducting properties have been studied for high-Tc superconductors of the $Bi_{2-x}Mo_xSr_2Ca_2Cu_3O_y$ system (x = 0.03-0.30). The crystal structure is pseudo tetragonal with the average lattice parameters a = 5.38 ${\AA}$, b = 5.44 ${\AA}$ and c = 30.6 ${\AA}$. All samples exhibit superconductivity with Tc offset at 79 K and Tc onset at 90-115 K. The Tc onset point decreases with increasing x, but the Tc offset points are nearly the same for all samples. Scanning electron micrographs show a special growth behavior of the grains with a plate shape. It is suggested that the decrease in Tc onset points with substitution of Mo for Bi is due to the decrease in lattice parameters and to the p-orbital of Mo. It is concluded that Mo does not play a crucial role in the superconducting transition of the $Bi_2Sr_2Ca_2Cu_3O_y$ system.

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.491-496
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• 1993

A class A ${\beta}$-lactamase from Staphylococcus aureus PC1 complexed with 3R,5R-clavulanate is studied. The starting geometry for the computation is the crystal structure of the ${\beta}$-lactamase. Docking of the clavulanate to the enzyme is done exploiting the requirements of electrostatic and shape complementarity between the enzyme and clavulanate. This structure is then hydrated by water molecules and refined by energy minimization and short molecular dynamics simulation. In the energy refined structure of this complex, the carboxyl group of the clavulanate is hydrogen bonded to Lys-234, and the the carbonyl carbon atom of the clavulanate is adjacent to the $O_{\gamma}$ of Ser-70. It is found that a crystallographic water molecule initially located at the oxyanion hole, which is formed by the two -NH group of Ser-70 and Gln-237, is replaced by the carbonyl oxygen atom of the 3R,5R-clavulanate after docking and energy reginement. The crystallographic water molecules are proved to be important in ligand binding. Glu-166 residue is found to be repulsive to the binding of clavulanate, which is in agreement with experimental observation. Arg-244 residue is found to be important to the binding of clavulanate as well as to interaction with C2 side chain of the clavulanate. The electron density redistribution of the clavulanate on binding to the ${\beta}$-lactamase in studied by an ab initio quantum-mechanical calculation. A significant redistribution of electron density of the clavulanate is induced by the enzyme, toward the enzyme, toward the transition state of the enzymatic reaction.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.639-642
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• 2019

Hydroxyapatite (HAP) containing hexadecyltrimethylammonium chloride (CTAC) as a cationic surfactant was prepared by a precipitation method. X-ray diffraction (XRD), transmission electron microscopy (TEM) and micropore physisorption analyzer were used for characterizing the crystal phase, morphology and specific surface area of HAP and CTAC-HAP. After thermal treatment, the specific surface area of both pure HAP and CTAC-HAP were reduced. The sharp rod morphology of CTAC-HAP was changed into a round shape with a smaller aspect ratio after the heat treatment. The morphological change by thermal treatment was also observed in pure HAP. Therefore, the morphological change and decrease of the specific surface area suggested that pores from the removal of CTAC during thermal treatment were not retained.