• Journal of Power System Engineering
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• v.16 no.1
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• pp.58-64
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• 2012

Power plant boiler is one of the most important utilities providing steam to turbine in thermal power plant. It is composed of thousands of boiler tubes for high efficient heat transfer. Boiler tube material is used in such high temperature and pressure as $540^{\circ}C$, $170kg/mm^2$. The boiler tube material is needed to resist corrosion damage, creep damage and fatigue damage. 2.25%Cr-1Mo steel is used for conventional boiler tubes. In these days steam temperature and pressure of the power plant became higher for high plant efficiency. So, the material property of boiler tube must be upgraded to meet the plant property. Several boiler tube material was developed to meet such condition. X20CrMoV12.1 steel is also developed in early 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensitic structure, which is difficult to evaluate the material degradation. Boiler tube material at severe condition was tested to evaluate long term and short term degradation and creep. Through long term and high temperature degradation test, lath structure was decreased and recrystallization has been proceeded by sub-crystal. And in this research the effect of temperature and stress on boiler tube characteristic,for example, deformation by creep was changed rapidly at relatively high temperature and stress because creep was affected easily by temperature and stress.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.519-522
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• 2002

In this paper, we analyze the impact of plasma etching process induced device degradation on low temperature poly-Si TFTs. The results indicate the relationship between device degradation and PPID effect during plasma fabrication. The dual-gate structure, which is used to suppress leakage current, is also discussed in this research.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.44-51
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• 1998

In order to develop the evaluation methods of degradation for the Ni-Cr-Mo-V steel, which is in use for turbine rotor in nuclear power plant, the degraded materials were prepared by simulated degradation methods. The result of impact test and fatigue crack growth test shows that the FATT(Fracture Appearance Transition Temperature) and fatigue crack growth rate increased with the increase of degradation. And the result of new electrochemical polarization test method was suggested for the evaluating FATT, fatigue crack growth exponent and coefficient C values based on the results of relationship between corrosion current density(Icorr) & FATT, and the m & C and Icorr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.28-32
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• 2004

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16% drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20% mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to $30^{\circ}C$ and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around $15^{\circ}C$ at the encapsulant discoloration spot of PV array.

• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.57-62
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• 2004

Turbulent drag reduction (DR) efficiency of water soluble poly(ethylene oxide) (PEO) with two different molecular weights was studied as a function of polymer concentration and temperature in a turbulent flow produced via a rotating disk system. Its mechanical degradation behavior as a function of time in a turbulent flow was also analyzed using both a simple exponential decay function and a fractional exponential decay equation. The fractional exponential decay equation was found to fit the experimental data better than the simple exponential decay function. Its thermal degradation further exhibited that the susceptibility of PEO to degradation increases dramatically with increasing temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1289-1295
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• 2004

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16 % drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20 % mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to 3$0^{\circ}C$ and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around 15$^{\circ}C$ at the encapsulant discoloration spot of PV array.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.680-685
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• 1998

Two kinds of new aliphatic diols were synthesized by the ring-opening reaction of lactide and glycolide with 1,4-butanediol, a difunctional initiator, in the presence of stannous octoate. The resulting aliphatic diols were melt-polymerized with D-tartaric acid at 150 ℃ to produce new crosslinkable polyesters. They were reacted with hexamethylene diisocyanate in THF at 65 ℃ in a teflon mold for 24 h to prepare sequentially ordered crosslinked polyesters (BD/LT/GL/D-tartarate). Degradation of the prepared yellow crosslinked films was carried out in a buffer solution in order to examine the effect of time, pH, temperature and crosslinking degree on their degradation rate and mechanism. The rate of degradation increased with an increase in pH and temperature, but it decreased with increasing degree of crosslinkage incorporated into the crosslinked polyesters. We also found that the crosslinked polymers were converted into the acidic compounds such as lactic, glycolic, and D-tartaric acids during the degradation.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.121-128
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• 1998

The degradation of mechanical properties in the high nitrogen steel HN3 developed for nuclear fusion reactor has been evaluated quantitatively using the small punch(SP) test, X-ray diffraction (XRD) analysis has also been conducted to identify carbides or nitrides precipitated on grain boundaries of the heat treated samples. Mechanical properties of the steel HN3 significantly decreased with increasing heat treatment time and temperature or with decreasing testing temperature. Combination of XRD and metallurgical observation, revealed that the material degradation in the thermally aged steel was caused by precipitation of carbides on the grain boundaries. While the weld metal showed the lowest mechanical properties among various microstructures in GTA weldments. By combining SP test and XRD analysis, cryogenic fracture behaviors and aging degradation for high nitrogen steel could be successfully evaluated in nondestructive manner.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.353-356
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• 2007

This paper presents the thermal and electrical characteristics of ZnO arrester blocks under the AC voltages. The leakage currents of ZnO arrester blocks were measured as a function of time. The temperature distributions of ZnO arrester blocks were observed by the forward looking infrared camera The degradation and thermal runaway of ZnO arrester blocks were closely related with the temperature limit of ZnO arrester blocks which decided heat generation and dissipation As a result, the degradation and thermal runaway of ZnO arrester blocks depend on the temperature and leakage current of ZnO arrester blocks.

• Environmental Engineering Research
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• v.25 no.3
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• pp.316-323
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• 2020

The degradation of aqueous oxytetracycline (OTC) from an aqueous solution antibiotic using H₂O₂/Fe²⁺ process was studied in one 1 L batch chemical reactor. The extent of OTC degradation (20 mg/L) was investigated from a known initial pH solution, temperature and the type of catalyst (Fe²⁺, Fe³⁺) and for various initial concentrations of OTC, H₂O₂ and Fe²⁺. The degradation efficiency achieved was found to be very important (90.82% and 90.63%) at initial pH solution of 3 and 4, respectively. However, the type of catalyst and the reaction temperature had a slight impact on the final degradation of OTC. The results showed that the OTC removal increased with increasing initial H₂O₂ concentration in the range of 70 to 150 mg/L and initial Fe²⁺ concentrations in the range of 2 to 5 mg/L. The highest degradation efficiency obtained at ambient temperature was 90.95% with initial concentration of OTC of 10 mg/L, H₂O₂ = 150 mg/L and Fe²⁺ = 5 mg/L. Moreover, biodegradability improved from 0.04 to 0.36 and chemical oxygen demand degradation was 78.35% after 60 min of treatment. This study proved that Fenton process can be used for pretreatment of wastewater contaminated by OTC before a biological treatment.