• Journal of Conservation Science
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• v.37 no.5
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• pp.567-578
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• 2021

In this study, the physicochemical properties of 21 wall fragments and rooftile pieces excavated from Jeseoksa Dump-site were analyzed, and the possibility of heat exposure, such as the fire reported in the literature, was investigated by estimating the firing temperature. From the results, it was estimated that the rooftiles were composed of refined materials, and the walls were composed of materials having different particle sizes depending on the layer. Unlike ordinary rooftiles and walls, they exhibited an uneven surface with traces of bloating phenomenon in the cross section. It was estimated from the blackening of some portions that firing was not performed in a controlled state in a constant firing environment. In addition, the estimated firing temperature showed that the non-overfired rooftiles had endured a firing temperature of 900℃ or less, but the over-fired samples were subjected to a temperature of 1,000℃ or higher and were fired at a temperature higher than the manufacturing temperature at that time. Additionally, the rooftiles probably became defective during firing or molding at the time of production, but the non-overfired rooftiles exhibited an intact shape and showed the possibility of heat exposure due to fire. Therefore, the analytical results of this study confirm that the defective architectural components damaged by the fire, as reported in the literature, were discarded in the Jeseoksa dump-site.

• Journal of Conservation Science
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• v.37 no.2
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• pp.77-89
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• 2021

In this study, materials and color formation techniques were assessed for black potteries excavated from the Janghyeon-dong, Jungsan-dong and Gyodong-ri sites during the Proto-Three Kingdoms period in Ulsan, Korea. Although the black potteries were black superficially, the inner cores were either black or reddish yellow. Microscopy analysis identified that body clay was used for reddish iron oxide rich soils with quartz, alkali feldspar and mica, along with grains of myrmechite texture. Additionally, as marginal differences exist in the contents of SiO₂, Fe₂O₃ and CaO, the composition of the host rock and clay distributed around the sites was affected. Thus, we can deduce that pottery was made by soiling at a short distance. Raman spectroscopy results revealed that the black layer of the black pottery was used as amorphous combustion carbon. In addition, as a transparent layer of brown lacquer was observed on the substrate that was in contact with the surface layer, the black layer of the pottery induced black color development by a combination of combustion carbon and lacquer. Based on the mineral composition and microtexture of the body clay, the firing temperature of the potteries seemed to range from 750 to 850℃, whereas the lacquer layer was pyrolyzed at 468℃ by thermal analysis. Therefore, a combined layer of combustion carbon and lacquer, which formed the black color, was painted after the body clay was fired.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.177-182
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• 2006

In this work, we have prepared organophilic MMT having thermal stability by ion exchange reaction of various aromatic ammonium salts with MMT containing sodium ion. The organic modifiers having alkyl side chains and amine functional group were successfully synthesized by effectively introducing the surfaces of MMT via ion exchange reaction to form organophilic MMTs with a view to improve the reactivity and thermal stability. The WAXD patterns of organophilic MMT showed the more increased gallery spacing by $3.3{\AA}$ than that of the pristine MMT and also the onset of initial decomposition of organophilic MMT was $275^{\circ}C$ as determined by a thermogravimetric analysis. The polyimide (PI) nanocomposite films based on poly(amic acid) and organophilic MMT were prepared by a solution blending followed by cyclodehydration reaction. We have investigated the dispersity of organophilic MMTs in PI matrix by using WAXD and the effect of the organophilic MMT content on the mechanical properties of PI nanocomposite films was studied.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.224-230
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• 2001

The characteristics of $NO/N_2O$ annealed reoxidized nitrided oxide being studied as super thin gate oxide and gate dielectric layers of Non-Volatile Semiconductor Memory (NVSM) were investigated by Dynamic Secondary Ion Mass Spectrometry (D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and Auger Electron Spectroscopy (AES). The specimen was annealed by $NO/N_2O$ after initial oxide process and then rcoxidized for nitrogen redistribution in nitrided oxide. Out-diffusion of incorporated nitrogen during the wet oxidation in reoxidation process took place more strongly than that of the dry oxidation. It seems to indicate that hydrogen plays a role in breaking the Si N bonds. As reoxidation proceeds, incorporated nitrogen of $NO/N_2O$ annealed nitrided oxide is obsen-ed to diffuse toward the surface and substrate at the same time. ToF-SIMS results show that SiON species are detected at the initialoxide interface, and Si,NO species near the new $Si_2NO$ interface that formed after reoxidation. These SiON and $Si_2NO$ species most likely to relate to the origin of the state of memory charge traps in reoxidized nitrided oxide, because nitrogen dangling bonds of SiON and silicon dangling bonds of $Si_2NO$ are contained defects associated with memory effect.

• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.342-349
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• 2002

New formation technique of metal oxide sensing film was proposed m this paper. Silicon wafer with Pt electrodes was used as a substrate for depositing metal Sn film. Metal Sn was deposited in the state of not continuous film but only island state. The samples were prepared to obtain the optimal condition of metal Sn deposition. The resistances of deposited Sn onto Pt electrodes amounted to $1\;k{\Omega}$, $5\;k{\Omega}$, $10\;k{\Omega}$ and $50\;k{\Omega}$, respectively. Also The sample with $1,500\;{\AA}$ thickness of Sn was prepared m order to compare sensing properties between conventional type and proposing type. After deposition of metal Sn, $SnO_2$ was formed by thermal oxidation method for 3 hrs. in $O_2$ ambient at $700^{\circ}C$. Surface morphology, crystal structure and surface roughness of oxidized-sensing film were examined by SEM, XRD, and AFM, respectively. From the results of these analyses, the optimal deposition condition of Sn was that the Pt electrode resistance became $10\;k{\Omega}(300\;{\AA})$. Also, the sensing characteristics of fabricated sensing film for various concentrations of butane, propane and carbon monoxide gases were measured at he operating temperatures of $250^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$, respectively. Although catalyst as not added to the sensing film, it has exhibited the high sensitivity to all the test gases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3990-3996
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• 2014

Because the physical properties can be decreased when a Nylon 66/glass fiber composite is injected into a mold over $300^{\circ}C$, a systematic study of the thermal history in the case of re-use is needed. Nylon 66/glass fiber extrudates as a function of the extrusion number were prepared using a twin screw extruder at 305/290/273/268/265/$260^{\circ}C$. The chemical structure, thermal properties, melt index, crystal structure, Izod impact strength, and rheological properties were measured by Fourier transform infra-red (FT-IR), melt indexer, DSC, TGA, XRD, Izod impact tester, and dynamic rheometer. The FT-IR spectra indicated that the number of extrusions did not affect the chemical structure. The decrease in molecular weight with increasing extrusion number was confirmed by the melt index and the complex viscosity of extrudates. Based on the DSC and TGA results, the thermal history had no effect on the melting temperature, regardless of the number of extrusions, but the degradation temperature decreased up to $20^{\circ}C$ with increasing extrusion number. The Izod impact strengths of the extrudates were found to decrease with increasing extrusion number. No structural change after extrusion was also confirmed because there was no change in the slope and shape of the G'-G" plot.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.264-269
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• 2007

Today's research has been focused on changing the light source from filament to LED for luminarie illumination to overcome the shortcoming of a filament. The purpose of this research is to make an appropriate high power LED package structure for luminarie. We simulated radiation patterns of the various structures by the ray tracing simulator (Light Tools), and also analyzed the radiation patterns using an LED test system (OL770). As we increased an inner reflector angle, the radiation pattern split into two peaks and the angle between two peaks became larger. In addition, when we increased an outer reflector angle, the angle between side peaks gradually decreased, while it increased again when the angle reach $50^{\circ}$. These results could be understood from the ray tracing of the light reflected from two reflectors. We made the high power LED package for luminarie on the condition of the optimized structure which was made by ray tracing simulation results, and we measured the radiation patterns by using an LED test system, and these results were well matched to the simulation results.

• Journal of the Korean Applied Science and Technology
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• v.32 no.4
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• pp.639-648
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• 2015

Some materials of fatty acids in the biodiesel affect the physical/chemical properties like density, kinematic viscosity, total acid number and oxidation stability by forming an organic fatty acid in combination with oxygen in the air. To solve the problem of the oxidative stability of biodiesel, various kinds of antioxidant has added and analyze the characteristics of the physical/chemical property changes by the addition of antioxidant. Oxidation stability increased by the increase of additives content. The TBHQ among the seven kinds of the additives showed the best performance. Also, 4 kinds of additives like propyl gallate, butyl-amine and pyrogallo has showed above 10 hr of oxidation stability at the addition of 500 ppm. In case of pyrogallo, this is not appropriate as an additive to suitable quality standards of total acid number. TBHA, DTBHQ of hydroquinone was satisfied with the quality standard of oxidation stability but the target of this research(above 10 hr) did not satisfied with oxidation stability. Propyl gallate is also a suitable at the quality standards of total acid number but it was shown not to be an appropriate to the additives due to increasing the total acid number by increasing of the content of additives at the addition of 500 ppm.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.64-69
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• 2006

Cathode materials of Al-doped $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single-step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of $I_{003}\;to\;I_{104}$, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and $184mAhg^{-1}$ in a voltage range of $3.0\sim4.5V$ at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of $3.0\sim4.6V$, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to $Mn^{3+}$ ion decrease as the Al doping from the XPS analysis results.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.877-880
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• 2008

Recently the press and institute recognized fly ash as it had excellent performance. Its research and applications are on the rise largely as a substitute for cement. On the contrary, it is in a situation that the regulation of high quality fly ash remains at a low level. Accordingly, this study was to establish 8000 class of fineness of fly ash and three levels of substitute like 15%, 3 0%, and 45% in order to analyze the replacement ratio and effect of water-binder ratio for fly ash that affected the properties of ternary system concrete. As a result of experiment by planning water-binder ratio for two levels like 40% and 50%, it increased the fluidity in a fresh state, and it decreased the air content. This study has found out the setting acceleration and reduction of heat of hydration. As for the strength property in a set state, this study has shown the tendency of being equal or higher in age 28 days.