• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.108-115
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• 2019

The thermal response of elastomeric insulators used as protection against high-temperature and high-pressure combustion gases varies depending on their composition and thermal environment conditions. In this paper, the thermal response characteristics of elastomeric insulators in different mixing environments were compared. Tests to determine thermal protection performance were carried out using a thermal protection rubber evaluation motor(TPREM), combustion gas velocities of 20 m/s and 100 m/s were tested at a chamber pressure of 1,000 psig. The pressure time curve of the chamber, the temperature time curve of the internal materials, the residual thickness and the thermal destruction depth of the test specimens were obtained. The results showed that the thermal protection performance of elastomeric insulators in different mixing environments was similar.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.69-76
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• 2021

In this work, we have performed a corrosion failure analysis of a leaking tube connected to an upper header of a condensate pre-heater in a heat recovery steam generator. It was revealed that the leakage position in the tube was the location where the materials were easily vulnerable due to tensile residual stresses induced by the material manufacturing process and welding process. In addition to an imbalance in the module induced by temperature difference during operation of the pre-heater, the weight of the modules and thermal fatigue provoked a type of stress of tensile-tensile fatigue on the tube. Thus, the leakage position of the pre-heater was exposed to the tensile stress on the inner surface of the tube facing the gas, which rendered the unstable oxide layer susceptible to corrosion and the formation of pits on the water side. The cracks propagated along with the degraded microstructure in a transgranular cracking mode under fatigue loading and finally resulted in water leakage.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.36-42
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• 2021

In this study, the impregnation of Lyocell fabrics was performed using phosphoric acid, ammonium phosphate, diammonium hydrogen, triammonium phosphate as phosphorus flame retardant, to fabricate continuous graphite fabrics using lyocell fiber. The physical and chemical structure changes were investigated by thermogravimetric, Fourier-transform infrared spectroscopy, C-nuclear magnetic resonance, X-ray diffraction, and weight analyses, By analyzing the thermal behavior of phosphorus flame retardant, conditions for the temperature, gas, and residual time of the pyrolysis process were set. Graphite fabrics with a tensile strength of 1,007.19±11.47 N/5 cm and yield of 25.3% were fabricated using continuous pyrolysis, carbonization and graphitization process.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.39.1-39.1
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• 2020

We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The HORIZON-AGN simulation is analysed at z~2 using the DISPERSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.22 no.2
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• pp.159-171
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• 2024

This study aimed to develop an efficient recycling process for wastewater generated from soil-washing used to remediate uranium (U(VI))-contaminated soil. Under acidic conditions, U(VI) ions leached from the soil were precipitated and separated through neutralization using hydrazine (N₂H₄). N₂H₄, employed as a pH adjuster, was decomposed into nitrogen gas (N₂), water (H₂O), and hydrogen ions (H⁺) by hydrogen peroxide (H₂O₂). The residual N₂H₄ was precipitated when the pH was adjusted using sulfuric acid (H₂SO₄) to recycle the wastewater in the soil-washing process. This purified wastewater was reused in the soil-washing process for a total of ten cycles. The results confirmed that the soil-washing performance for U(VI)-contaminated soil was maintained when using recycled wastewater. All in all, this study proposes an efficient recycling process for wastewater generated during the remediation of U(VI)-contaminated soil.

• Membrane Journal
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• v.23 no.2
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• pp.151-158
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• 2013

The effect of layered double hydroxides (LDH) on the gas separation properties of ethylene vinyl acetate copolymer was investigated. Mg-Al LDH/EVA nanocomposite membranes were prepared from solution intercalation using organically modified LDH (DS-LDH). Dodecyl sulfate (DS)-LDH was obtained by the intercalation of DS anion in the interlayer. The nanocomposite structure has been elucidated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). XRD pattern clearly shows that the DS-LDH layers are disorderly well dispersed in the EVA matrix. The maximum tensile strength and elongation of the LDH/EVA nanocomposite membrane were found with the LDH content 3 wt%. The thermal properties of nanocompostie membrane were enhanced by the incorporation of LDH in EVA matrix. Gas permeation of LDH/EVA nanocomposite membranes with LDH contents of 1, 3, 5 wt% was studied for $O_2$ and $CO_2$ single gases. The presence of 3 wt% LDH decreased $O_2$ permeability by up to 53% compared to the EVA membrane. In spite of barrier property of nanocomposite membrane, however, the gas permeability for $CO_2$ was increased due to its strong affinity with the residual OH groups on the LDH.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.693-699
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• 2001

ChlorophyII destruction by irradiation in linoleic acid in methanol system was studied. ChlorophyII b standard (3 ppm) was added into methanol solution containing 1% of linoleic acid, and the sample was irradiated up to 20 kGy with or without nitrogen gas-bubbling. The content of chlorophyII b was analyzed by HPLC, and Hunter color value and UV-visible spectra were analyzed during 6 hr of photooxidation. The content of chlorophyll was reduced by irradiation and completely destroyed at 2.517 kGy. The model system with nitrogen gas-bubbling did not develop the lipid oxidation after irradiation or photooxidation at 20 kGy UV-visible spectra showed decreasing values of optical density by increase of irradiation doses, supporting the destruction of chlorophyII b. The results indicate that irradiation technology can be applied to reduce or eliminate the residual chlorophyII and to prolong the shelf-life of oil products.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.8-12
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• 2010

Purpose: In $^{18}F$-FDG automated synthesizer, deliver is done in automated mode after synthesis until the dispenser. After the delivery, the yield is calculated from the radioactivity which was read by the dose calibrator located in the dispenser. However, when the distance between the automated synthesizer and the dispenser is far, there are $^{18}F$-FDG residues, which results in loss of the amount of $^{18}F$-FDG. This study investigated the usefulness of a method that minimizes $^{18}F$-FDG residues. Materials and Methods: The structure of the tubing between the (TRACERlab Mx FDG; GE.) and the dispenser is that the distance is 8 m and the internal diameter is 1/16 inch. The synthesis process of The module goes through the synthesis process of trap, synthesis, delivery in the automated module. The time taken for synthesis is about 25 to 26 minutes, after which rinsing is done. However, after rinsing, as the distance of the tubing increased, there were 10~13% of $^{18}F$-FDG residues. Therefore, a method of using push syringe and $N_2$ gas in manual mode to minimize $^{18}F$-FDG residues is analyzed. Results: In manual mode, there were $^{18}F$-FDG residues of 4~5% for the push syringe, and there were $^{18}F$-FDG residues of less than 1% for the $N_2$ gas, which showed that the method using $N_2$ gas had superior usefulness. Also, there were no $^{18}F$-FDG residues in the cleaning the next day. Conclusion: The distance between the synthesizer and the dispenser needs to be reduced as much as possible, to reduce the rate of loss of $^{18}F$-FDG resulting from the distance of the tubing. However, in case the distance between the synthesizer and the dispenser has to be increased due to the system structure, using push syringe and $N_2$ gas simultaneously is a useful method for minimizing $^{18}F$-FDG residues.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.695-703
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• 2012

Recently, major infrastructure such as bridges, tunnels, PCCVs (Prestressed Concrete Containment Vessel), and gas tanks are Prestressed Concrete (PSC) structure types, which improve their safety by using confining effect from prestressing. Generally, concrete is known to be an outstanding fire resistant construction material. Because of this reason, researches related to extreme fire loaded PSC member behaviors are not often conducted even though PSC behavior under extreme fire loading is significantly different than that of ordinary reinforced concrete (RC) behavior. Therefore, in this study, RABT fire loading tests were performed on bi-directionally prestressed concrete panels with $1000{\times}1400{\times}300mm$ dimensions. The prestressed specimens were applied with 430 kN prestressing (PS) force using unbonded PS thread bars. Also, residual strength structural tests of fire tested PSC and ordinary RC structures were performed for comparison. The study results showed that PSC behavior under fire loading is significantly different than that of RC behavior.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.40 no.2
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• pp.163-170
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• 2014

Lipid membranes composed of phosphatidylcholine (PC) are used in biophysical study to mimic cellular membranes and interactions between the membrane and chemicals, where organics solvents are used in dissolving lipids or chemicals. Later, solvents are removed from the solution under nitrogen gas at room temperature, followed by the further removal of the solvent at vacuum condition for several hours. In this process, some solvents are easily removed under described conditions above and others are required more severe conditions. In this study, $^{31}P$ solid-state nuclear magnetic resonance (SSNMR) techniques and differential scanning calorimetry (DSC) were used to see any changes in the line shapes of $^{31}P$ NMR spectra of multilamellar vesicles (MLVs) samples of POPC and in the phase change temperature of multilamellar vesicles (MLVs) of DPPC in DSC thermogram with or without any residual solvents. The thermodynamic parameters associated with the solvents did exhibit noticeable changes depending on solvent types. Thus, it is concluded that solvents should be carefully chosen and removed completely and experimental results should also be interpreted with caution particularly for the experiments investigating lipid phase changes and related topics.