• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.113-116
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• 2009

This study analyzed fire-resistant characteristics according to changes in repair methods of PFH mixed high-strength concrete roof structures having undergone fire damage. The results of the study are as follows. First, as a repulsive characteristics of structures, the remaining repulsion was shown to increase following fire-resistance tests according to increases in depth of coverings. The results of the relationship between depth of coverings and remaining repulsion rates following fire-proofing tests showed a high correlation. At a covering depth of 67.3mm, remaining repulsion rate was estimated to be 100%. For fire-resistant characteristics following repairs of structure, as for spalling, severe separation was shown in the case of general plaster while general plaster + Metal Lath showed overall superior spalling prevention. For internal structure temperatures, general plaster showed max temperatures of 705℃, average temperatures of 636℃ while general plaster + metal lath showed max temperature of 660℃ and average temperature of 520℃, demonstrating lower temperature distributions than use of only general plaster. In conclusion, after removing the covering of structures damaged due to high temperatures of fires within high-strength concrete installations, the use of fire-resistant mortars and applying metal laths on surfaces of general plaster will provide superior fire-resistance performance in the occurrence of a 2nd fire.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.225-229
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• 2015

This study was performed to investigate crystal structure of cubic spinel-type monophase oxide composed of the Mn-Co-Ni ternary system. Starting material was prepared by mixing Mn, Co, Ni oxides then evaporation to dryness. The XRD patterns were analyzed by in-situ XRD as increasing temperature from room temperature to $1400^{\circ}C$ in air atmosphere. The cubic spinel phase was existed in a temperature range from $900^{\circ}C$. However, separation of NiO phase was detected from $1300^{\circ}C$, which was the origin of deterioration in the crytallinity. The surface morphology of the manufactured NTC thermistors were analyzed by FE-SEM for comparison of good and bad samples.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.967-974
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• 2009

Experiments were conducted to measure the heat flux and temperature over a protuberance, using an impulse hypersonic shock tunnel-coaxial thermocouples and a blowdown hypersonic wind tunnel-temperature sensitive paints(TSP). Experimental data were compared with the heat flux data using a blowdown hypersonic wind tunnel-heat flux gauges and it was confirmed data sets agreed well. The measured heat flux is large when the height of the protuberance is large. Also, the heat flux measurements at the upper positions are larger than at the lower positions. For high protuberances, a severe jump in the heat flux is observed, from about 0.6~0.7 of the height of the protuberances. However, when the protuberance is sufficiently short, a rise in the heat flux is rarely observed as the protuberance is submerged totally under the separation region.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.29-33
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• 2019

Carbon nanotubes, nanofibers and powders were used for acetylene adsorption experiments. A total of 15 different experiments were designed by 3-level of Box-Behnken Design (BBD) with 3 factors including the Pd concentration of 0 to 5%, adsorption temperature of 30 to $80^{\circ}C$ and $C_2H_2/CO_2$ of 3 to 10. Based on those data, a second order polynomial regression analysis was used to derive the adsorption amount prediction equation according to operating conditions. The adsorption temperature showed the greatest influence index while the $C_2H_2/CO_2$ ratio showed the smallest according to the F-value measurement of the ANOVA analysis. However, there was little interaction between major factors. In the adsorption optimization analysis, a 22.0 mmol/g was adsorbed under the conditions of Pd concentration of 3.0%, adsorption temperature of $47^{\circ}C$ and $C_2H_2/CO_2$ of 10 with 95.9% accuracy.

• Elastomers and Composites
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• v.37 no.4
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• pp.211-216
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• 2002

The polymer-polymer interaction parameter, x 23t, of the styrene-butadiene polymer (SBR) and ethylene-propylene-diene terpolymer (EPDM) was investigated by observing the phase behavior of the ternary system of SBR/EPDM/solvent. The solvent used in this study was benzene acting as a good solvent for SBR but as a poor solvent for EPDM. Ternary solutions with various concentrations and mixing ratios of the two component polymers were separated into two phases by temperature change The cloud point curves (CPC) showed that the differerence of solvent affinities toward each polymer and the repulsive interaction between two polymers considerably affect the shape of CPC near 15℃. In the temperature range of 5℃ ~ 25℃, incompatible behaviours arised from both the difference of mixing ratios and concentration were clearly observed. Also the phase separation temperature greatly influenced on the composition of each separated phase. The calculated x 23t values from Flory-Huggins theory were in the range of 0.6301 ~ 1.0775, which suggest that the SBR/EPDM systems are incompatible.

• Journal of Climate Change Research
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• v.34 no.20
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• pp.8257-8271
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• 2021

This study presents the ability of seasonal forecast models to represent the observed midlatitude teleconnection associated with El Niño-Southern Oscillation (ENSO) events over the North American region for the winter months of December, January, and February. Further, the impacts of the associated errors on regional forecast performance for winter temperatures are evaluated, with a focus on 1-month-lead-time forecasts. In most models, there exists a strong linear relationship of temperature anomalies with ENSO, and, thus, a clear anomaly sign separation between both ENSO phases persists throughout the winter, whereas linear relationships are weak in observations. This leads to a difference in the temperature forecast performance between the two ENSO phases. Forecast verification scores show that the winter-season warming events during El Niño in northern North America are more correctly forecast in the models than the cooling events during La Niña and that the winter-season cooling events during El Niño in southern North America are also more correctly forecast in the models than warming events during La Niña. One possible reason for this result is that the remote atmospheric teleconnection pattern in the models is almost linear or symmetric between the El Niño and La Niña phases. The strong linear atmospheric teleconnection appears to be associated with the models' failure in simulating the westward shift of the tropical Pacific Ocean rainfall response for the La Niña phase as compared with that for the El Niño phase, which is attributed to the warmer central tropical Pacific in the models. This study highlights that understanding how the predictive performance of climate models varies according to El Niño or La Niña phases is very important when utilizing predictive information from seasonal forecast models.

• Membrane Journal
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• v.14 no.3
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• pp.201-206
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• 2004

The stability of the prepared silica membrane by chemical vapor deposition (CVD) method in the HI-$H_2O$ gaseous mixture was evaluated aiming at the application for hydrogen iodide decomposition in the thermochemical IS process. Porous $\alpha$-alumina having pore size of 100 nm was modified by the different CVD temperature using tetraethoxysilane as the Si source. The CVD temperature was $700^{\circ}C$, $650^{\circ}C$, and $600^{\circ}C$. The $H_2$/H$_2$ selectivities of the modified membranes which were measured by single-component permeation experiment showed 43.2, 12.6, and 8.7 at $600^{\circ}C$ for the M1 (CVD temperature was $700^{\circ}C$), M2 (CVD temperature was $650^{\circ}C$) and M3 membranes (CVD temperature was $600^{\circ}C$), respectively. Stability experiment in the HI-$H_2O$ gaseous mixture was carried out at $450^{\circ}C$. The prepared silica membrane at $600^{\circ}C$ of CVD temperature was more stable than that at the other CVD temperature.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.227-230
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• 2013

The phase change of $(U_{1-x}Nd_x)_3O_8$ powder produced by oxidation of Nd-doped $UO_2$ pellet at $500^{\circ}C$ was investigated by high temperature oxidation heat treatment at $900{\sim}1500^{\circ}C$ under an air atmosphere. The XRD analysis results showed that the formation of $(U_{1-y}Nd_y)O_{2+z}$ phase and $U_3O_8$ phase from metastable $(U,Nd)_3O_8$ phase initiated at a temperature of $1000^{\circ}C$. The relative integrated intensity of $(U_{1-y}Nd_y)O_{2+z}$ phase to $U_3O_8$ phase increased with increasing of the oxidation temperature from 1100 to $1500^{\circ}C$. And also, it was found from the SEM observation that the particle size of $(U_{1-y}Nd_y)O_{2+z}$ phase increased with increasing of the oxidation temperature. However, electrone probe X-ray microanalyzer (EPMA) analysis results showed that Nd contents in $(U_{1-y}Nd_y)O_{2+z}$ phase decreased with increasing of the oxidation temperature. This behavior on the ground of XRD, SEM, and EPMA analysis data could be interpreted in terms of the transportation of U ions from $U_3O_8$ phase into $(U_{1-y}Nd_y)O_{2+z}$ phase through the interface of two phases during high temperature oxidation.

• Composites Research
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• v.36 no.3
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• pp.180-185
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• 2023

This paper investigates the impact of fiber dispersion on the internal structure and mechanical strength of SiC_f/SiC composites manufactured using spread SiC fibers. The fiber volume ratio of the specimen to which spread SiC fiber was applied decreased by 9%p compared to the non-spread specimen, and the resin slurry impregnated between the fibers more smoothly, resulting in minimal matrix porosity. In order to compare the fiber dispersion of each specimen, a method was proposed to quantify and evaluate the separation distance between fibers in composite materials. The results showed that the distance between fibers in the spread specimen increased by 2.23 ㎛ compared to the non-spread specimen, with a significant 42.6% increase in the distance between fiber surfaces. Furthermore, the 3pt bending test demonstrated a 49.3% higher flexural strength in the spread specimen, accompanied by a more uniform deviation in test data. These findings highlight the significant influence of SiC fiber dispersion on achieving uniform densification of the SiC_f/SiC matrix and increasing mechanical strength.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.11
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• pp.1837-1842
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• 2013

Photostimulated luminescence (PSL) and thermoluminescence (TL) analyses were conducted for the detection of different gamma-irradiated dried fishes (mussel, squid, beka squid, mitra squid, plaice, and saury) at 0, 1, 5 and 10 kGy. For TL analysis, the contaminating silicate minerals were obtained by density separation or acid hydrolysis treatment. PSL determinations indicated that all the non-irradiated samples showed PSL photon counts/60 s (PCs) lower than 700 PCs (negative), but the irradiated mussel sample at 5 and 10 kGy were only possibility identified showing higher than 5000 PCs (positive). Irrespective of sample kinds and methods of mineral separation, all the non-irradiated samples showed TL glow curves in low-intensity with a maximum peak only after $250^{\circ}C$. However, all the irradiated samples produced TL glow curves in high intensity with a maximum peak particularly in the temperature range of 1$150{\sim}250^{\circ}C$. In conclusion, more distinguishable TL results [glow curve, TL ratio ($TL_1/TL_2$)] were obtained from the marker minerals separated by acid hydrolysis rather than density method.