• Analytical Science and Technology
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• v.26 no.1
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• pp.27-33
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• 2013

Polyalkylsilanes such as poly(dialkyl)silanes and poly(monoalkyl)silanes were synthesized by sonochemical dechlorination-condensation method from (dialkyl or monoalkyl)chlorosilanes with sodium metal. Those polyalkylsilanes were analyzed for the properties such as thermal behaviors from TGA analysis and obtained ceramic yields of 10-20% for poly(dialkyl)silanes and 40-60% for poly(monoalkyl)silanes. Ceramic composite discs were prepared by the combined mixture of polyalkylsilanes and SiC powder and were tested by TGA and analyzed by SEM and XRD for the application as binder for ceramic composite precursors.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.573-578
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• 2008

In the preparation of hydroxyapatite(HAp)/gelatin(GEL) nanocomposite, GEL matrix was modified by the introduction of chondroitin sulfate(ChS) to obtain a strongly organized composite body. The formation reaction of the HAp/GEL-ChS nanocomposite was then investigated via XRD, DT/TGA, FT-IR, TEM and SEM. The organic-inorganic interaction between HAp nanocrystallites and GEL molecules was confirmed from DT/TGA and FT-IR. According to the DT/TGA results, the exothermal temperature zone between 300 and $550^{\circ}C$ showed an additional peak temperature that indicated the decomposition of the combined organics of the GEL and ChS. From the FT-IR analysis, calcium phosphate(Ca-P) was covalently bound with the GEL macromolecules modified by ChS. From TEM and ED, the matrix of the GEL-ChS molecules was mineralized by HAp nanocrystallites and the dense dried nanocomposite body was confirmed from SEM micrographs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1154-1157
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• 2004

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in imitation stator winding of high voltage motors. The motor was energized to 4.47kV, 6.67, respectively. Applied voltage to Imitation winding was used two voltage level, 4.47[KV]and 6.67[KV]. Motors having imitation stator winding were installed with 80pF capacitive couplers at the terminal box Case of PD Pattern regarding applied voltage phase angel, the PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). As the result, we could discrimidate using TGA the difference of internal and surface discharge for imitation stator winding. We have used the other technique, in order to feature extraction of faulty signals on stator winding, Daubechies Discrete wavelet transform and Harmonics analysis(FFT) about faulty signals.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1062-1067
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• 2007

In this paper, we have investigated thermal properties of semiconductive shield materials for power cables. EEA (Ethylene Ethyl Acrylate) was used for base polymer and TGA (Thermal Gravimetric Analysis) and AFM (Atomic Force Microscope) were investigated with various carbon black and CNT (carbon nanotube) contents. When CNT reinforced composites and conventional composite were investigated with TGA, we knew that thermal properties of CNT reinforced composite were better than them of conventional composite. To investigate roughness, we used AFM. Before and after aging, AFM was applied and after aging, roughness was increased. As a result, suitable CNT and CB(carbon black) content is CNT:CB=50:50.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2091-2093
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• 2005

Five model coils of 6.6kV motor were manufactured with several defects. These stator coils have artificial defects such as void of groundwall insulation, removal of semi-conductive coating and damage of strand insulation. Epoxy-mica coupler(80 pF) was connected to five model coil terminals, respectively The voltage applied to the coils was 3.81kV, 4.76kV, 6.0kV and 6.6kV. Partial discharge(PD) tests performed in the laboratory and shield room. Digital PD detector (PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in pC were measured with PDD. PD patterns of model coils were indicated the internal and slot discharges. PD patterns coincide with both PDD and TGA.

• Composites Research
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• v.37 no.1
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• pp.1-6
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• 2024

A liquid crystalline thermosetting epoxy was synthesizes with DGE-DHMS and 1-Methyl Imidazole. To investigate thermal stability, activation energies for thermal decomposition were calculated via Flynn-Wall-Ozawa method and Kissinger method with the data obtained from TGA analysis. The result showed that there were no differences in thermal decomposition behavior between liquid crystalline phases and isotropic phase and also the same thermal decomposition mechanism was applied to the entire process.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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• pp.525-529
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• 2017

To improve the thermal resistance of a porous borosilicate lining block, we prepared and applied polysiloxane-fumed silica-ethanol slurry on top of the block and fired the coating layer using a torch for 5 minutes at $800^{\circ}C$. We conducted magnified characterizations using a microscope and XRD analysis to observe phase transformations, and TGA-DTA analysis to determine the thermal resistance. Thermal characterizations showed improved heat resistance with relatively high polysiloxane content slurry. Cross-sectional optical microscope observation showed less melting near the surface and decreased pore formation area with higher polysiloxane content slurry. XRD analysis revealed that the block and coating layer were amorphous phases. TGA-DTA analysis showed an endothermic reaction at around $550^{\circ}C$ as the polysiloxane in the coating layer reacted to form SiOC. Therefore, coating polysiloxane on a borosilicate block contributes to preventing the melting of the block at temperatures above $800^{\circ}C$.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.47-53
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• 2004

Emulsion polymerization ws carried out using Alkyl methacrylate(RMA) like MMA, EMA, BMA and Styrene Monomer(SM) for core-shell latex preparation. It was synthesized at $80^{\circ}C$ in the presence of anionic surfactant SLS(Sodium Lauryl Sulfate). FT-IR and DSC analysis are used to confirm the synthesized core-shell emulsion latexes. Moreover DSC and TGA were used to investigate the thermal characterisitcs of them. The differences of the decomposition rate and the activation energy from TGA and DSC analysis are not so big. It considers that the pendent group is not affect of the thermal characteristics and stability on core-shell latexes, which is synthesized with RMA and Styrene. For investigating combustion products, LC50 values were calculated by FED(Fractional Effective Dose)from the Pyrolyzer-Mass sepctrometer.

• Journal of the Korea Safety Management & Science
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• v.11 no.3
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• pp.217-226
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• 2009

The combustion reaction of polyvinylchloride(PVC) was investigated using a thermogravimetric technique under an air atmosphere condition at several heating rates from 10 to $50^{\circ}C$/min. To obtain information on the kinetic parameters, the dynamic thermogravimetric analysis curve and its derivative were analyzed by a variety of analytical methods such as Kissinger, Friedman, Chatterjee-Conrad, Ozawa and Coats-Redfern methods. The combustion reaction of PVC proceeded in two steps; the first step was caused by the dehydrochlorination process in PVC, and the second step by the combustion of polyene. The comparative works for the kinetic results obtained from various methods should be performed to determine the kinetic parameters, because there are tremendous differences in the calculated kinetic parameters depending upon the mathematical method taken in the analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.7
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• pp.41-47
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• 2014

The on-line partial discharge (PD) in stator windings of air-cooled gas turbine (GT) generator (119.2MVA, 13.8kV) is measured and analyzed in this paper. This generator was designed by global vacuum pressure impregnation (VPI). The generator failed two times at top bar (16T) of phase B in the stator slot. Six epoxy-mica capacitors were installed in three phases of GT generator. On-line PD test was performed on GT generator using turbine generator analyzer (TGA). TGA showed that the normalized quantity number (NQN) and the PD magnitude($Q_m$) were high in phase B. Internal discharges were generated in phases A, B and C. The trend analysis of NQN and $Q_m$ value are obtained in order to monitor the insulation condition in GT generator stator windings. Phases A and C were in good condition. But phase B had deteriorated significantly