• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.325-335
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• 2016

To predict service life of coating systems registered in Korean specifications for steel bridge coatings, field deterioration evaluation and accelerated weatherproof test were carried out, and deterioration models were drawn through regression analysis for evaluation results. For the coating systems that have not been used in field, regression analyses were carried out for the virtual evaluation results drawn by applying coordination factor to the field evaluation results for chlorinated rubber and urethane topcoat system. Service life prediction results showed that application of thermal sprayed coating (TSC) could extend service life of coatings to more than twice of general coatings.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1100-1108
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• 2021

Supercritical water has great potential as a coolant for nuclear reactor. Its use will lead to higher thermal efficiency of Rankine cycle. However, in certain conditions heat transfer may get deteriorated which may lead to undesirable high clad surface temperature. It is necessary to estimate the operating conditions in which heat transfer deterioration (HTD) will take place, so as to establish thermal margins for safe reactor operation. In the present work, the heat flux corresponding to onset of HTD for vertically upward flow of supercritical water in a pipe is obtained over a wide range of system parameters, namely pressure, mass flux, and pipe diameter. This is done by performing large number of simulations using an in-house CFD code, which is especially developed and validated for this purpose. The identification of HTD is based on observance of one or more peak/s in the computed wall temperature profile. The existing correlations for predicting the onset of HTD are compared against the results obtained by present simulations as well as available sets of experimental data. It is found that the prediction accuracy of the correlation proposed by Dongliang et al. is best among the existing correlations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.215-218
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• 1998

The thermal stability of polyaniline-camphorsulfonic acid(PANI-CSA) film was studied as a function of temperature and time. A decrease in electrical conductivity of PANI-CSA film occurred when PANI-CSA film is subjected to temperature above 60$^{\circ}C$. From the result of thermogravimetry (TG), it was thought that the deterioration in electrical conductivity of PANI-CSA film was due to evaporation of water and residual solvent.

• 보존과학연구
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• s.7
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• pp.265-277
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• 1986

The degradation of wood is maimly caused by biological and thermal factor. In general, the field of wood preservation can be divided into two broadcategories; namely the deterioration, protection of wood, and the teatment of wood with preservatives. Wood in sea or brackish water incurs marine borer damage, consisting of attack by marine animal and also wood on land suffers severely from insect damage. But the largest wood degradation is caused by microorganism. Animals that attack wood in a marine environment are especially destructive in warm water-regions, little was achieved in their control recently. Therefore this manuscript only introduce the importance of wood deterioration caused by marine animal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.829-834
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• 2016

Coil specimens were prepared by continuous coating on a copper wire with flexible PAI (polyamideimide) and PAI/nanosilica (5 wt%) varnish and thermally aged at 150, 200 and $250^{\circ}C$ for 5, 10 and 15 days, respectively. AC insulation breakdown voltage was investigated under inverter surge condition at 60 Hz and 1,000 Hz and insulation breakdown voltage decreased with increasing aging temperature and aging time at each 60 and 1,000 Hz.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.143-149
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• 2022

As ESS safety issues increase recently, there is a need to more precisely monitor the temperature of the ESS. In this paper, DTS technology for temperature monitoring of ESS batteries is introduced and the temperature measurement principle is explained. The temperature of the battery module is measured using the DTS system, and the thermal deviation between battery cells inside the battery module is analyzed. In order to analyze how thermal imbalance affects the charging and discharging performance of the battery, an accelerated degradation test was conducted. Cycle life characteristics analysis, battery surface temperature change, and AC impedance characteristics were conducted to analyze how the performance of battery cells differs according to temperature conditions.

• The Korean Journal of Food And Nutrition
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• v.22 no.1
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• pp.150-157
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• 2009

The purpose of this study was to analyze the anthocyanin contents of black soybean crude extracts derived using a countercurrent system and to compare the effects of stabilizers(${\beta}-cyclodextrin$, maltodextrin) and sugars(sucrose, maltose) on the color deterioration of the anthocyanin. When the extraction process was kept at 100$^{\circ}C$ for 120$\sim$180 min, only C3G (cyanidin-3-glucoside) was detected in the water extract. The C3G contents in the water extracts acquired at 8$^{\circ}C$, 60$^{\circ}C$, and 80$^{\circ}C$ were 2.38 ppm, 1.73 ppm, and 1.73 ppm, respectively. Sucrose and maltose retarded color deterioration of the crude pigment extract by the countercurrent method with methanol. Finally, the additions of maltodextrin or ${\beta}-cyclodextrin$ did not retard thermal color deterioration of the black soybean crude pigment extract.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.417-422
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• 2002

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. In this study, the compensation device and temperature-based algorithm have been implemented on the machining center in order to compensate thermal error of machine tools under the real-time. The thermal errors are predicted using the neural network and multi-regression modeling methods. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.

• Journal of Conservation Science
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• v.37 no.6
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• pp.648-658
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• 2021

In this study, we aimed to analyze the chemical changes that occur in Korean paper in an accelerated deterioration environment of 105℃. We selected the Korean paper produced with different types of cooking agents (plant lye, Na₂CO₃) and during different manufacturing seasons (winter, summer). The degree of deterioration of the Korean paper was confirmed by measuring the brightness, yellowness, and pH level, and the degree of change in each vibrational region of cellulose as deterioration progressed through infrared (FT-IR) spectroscopy. The FT-IR analysis showed that, as deterioration progressed, the absorbance of the amorphous region in cellulose decreased, whereas the absorbance of the crystalline region slightly increased. X-Ray diffraction (XRD) analysis and Raman spectroscopy were performed to verify the changes in the crystalline and amorphous regions in cellulose indicated by the FT-IR results. Furthermore, the crystallinity index (CI) was calculated; it showed a slight increase after deterioration; therefore, CI was confirmed to follow the same trend as that observed for absorbance in the FT-IR results. In addition, as a result of Raman spectroscopic analysis, the degree of decomposition of the amorphous region in the cellulose under the manufacturing conditions was confirmed by the fluorescence measured after the deterioration.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.629-646
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• 2023

Host rock of Cheonjeon-ri petroglyph is shale belonging to the Daegu Formation of Cretaceous Gyeongsang Supergroup. The rocks were hornfelsified by thermal alteration, and shows high density and hardness. The petroglyph forms weathered zone with certain depth, and has difference in mineral and chemical composition from the unweathered zone. As the physical deterioration evaluations, most of cracks on the surface appear parallel to the bedding, and are concentrated in the upper part with relatively low density. Breakout parts are occurred in the upper and lower parts of the petroglyph, accounting for 6.0% of the total area and occurs to have been created by the wedging action of cracks crossing. The first exfoliation parts occupying the surface were 23.8% of the total area, the second exfoliations covered with 9.3%, and the exfoliation parts with three or more times were calculated as 3.4%. It is interpreted that this is not due to natural weathering, and the thermal shock caused by the cremation custom here in the past. As the ultrasonic properties, the petroglyph indicates highly strength in the horizontal direction parallel to bedding, and the area with little physical damage recorded mean of 4,684 m/s, but the area with severe cracks and exfoliations showed difference from 2,597 to 3,382 m/s on average. Physical deterioration to the Cheonjeon-ri petroglyph occurred to influence by repeated weathering, which caused the rock surface to become more severe than the inside and the binding force of minerals to weaken. Therefore, it can be understood that when greater stress occurs in the weathered zone than in the unweathered zone, the relatively weathered surface loses its support and exfoliation occurs.