• Journal of Environmental Health Sciences
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• v.40 no.6
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• pp.435-441
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• 2014

Objectives: Bisphenol A, or BPA, is a chemical component in polycarbonate plastic with which many people come into contact every day. A great deal of controversy has arisen over its safety since this material, which is known to disrupt the human endocrine system and cause neurological difficulties and cancer, is commonplace in beverage containers, food can liners, and receipt paper rolls. In this study, we determined the levels of exposure to BPA of workers in the service industry depending on the number of receipts contacted. Methods: The participants were 16 male and 18 female workers employed in the service industry. Using a questionnaire, we investigated general and job characteristics. Urine samples were collected and analyzed by the LC-MS/MS technique after enzymatic hydrolysis and solid phase extraction (SPE). Results: The geometric mean (GM) concentration of urinary BPA from all subjects was 1.02 ng/ml. Workers were exposed significantly to more BPA according to the number of receipts they contacted, their work experience, and working hours per day. The BPA concentration of those who touched more than 100 receipts per day was 3.09 ng/ml, while that of the other participants was 0.61 ng/ml. It was shown that wearing gloves can protect from BPA exposure. Conclusion: We determined the urinary BPA concentrations of workers in service industry and found that the contact with receipts could increase the BPA exposure of service workers.

• Textile Coloration and Finishing
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• v.27 no.3
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• pp.175-183
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• 2015

Weight loss treatment of a fiber leads an improvement of its handle and drape properties. Hydrolysis of a fiber is commonly known as a method to reduce its weight of 5-40%. Most of the studies on the weight loss treatment are mainly based on polyester fibers and there has been almost no study on the weight reduction of nylon fibers. In this study, however, in order to develop a use of nylon 6 fiber for the industrial applications such as toothbrush, underwear, carpet and more, weight loss treatment of a nylon 6 fiber was carried out. Under various treatment conditions, morphological analysis were done to observe the change in the structure of the surface and analysis. From the observation of formic acid treated nylon 6 fiber, there were many etched and deformed morphologies. Thermal and crystalline properties were analyzed to find the changes in the crystal structure caused by the weight loss treatment. There were little differences in the crystalline properties of nylon 6 fiber by formic acid treatment. Tensile strength of nylon 6 fiber decreases with acid concentration. The FITR peak intensity of the amide bond decreases with formic acid concentration.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.61-63
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• 2003

A major research objective related to proton exchange membrane(PEM) for DMFC is to achieve high proton conductivity over 10$^{-2}$ S/cm, high hydrolytic stability and low methanol permeability with low cost base materials. for the purpose, a lot of thermoplastic polymers such as polysulfones, polyethersulfone, polyetherketones, polyimides, polyoxadiazole, polyphosphazene and polybenzimidazol have been investigated. Amongst those polymers, polyimides have been suggested as a potential PEM due to their excellent thermal, chemical stability and good mechanical properties. Generally, polyimides are synthesized by polycondensation with numerious diamines and dianhydriedes. In our study, polyimide was prepared using non-sulfonated diamine, sulfonated diamine directly synthesized by fuming sulfuric acid, and naphthalenic dianhydride to improve the hydrolysis stability under acidic condition. Through monomer sulfonation-subsequent polymerization method, the high proton conducting capability and the desired sulfonation level were effectively controlled at the same time. To reduce severe methanol transport through the membrane, the chemical crosslinking among polymer chains was introduced using various crosslinking agents with different chain lengths. The crosslinked sulfonated polyimide membranes showed high proton conductivity up to 8.09$\times$10$^{-2}$ S/cm and from crosslinking effect methanol transport through the membranes was considerably reduced as compared with unmodified membranes. For increase of chain length of crosslinker, methanol permeability was adversely reduced to 10$^{-8}$ $\textrm{cm}^2$/s due to decrease of IEC and increase of crosslinking desity.

• Journal of the Korean Society of Clothing and Textiles
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• v.16 no.3 s.43
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• pp.335-344
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• 1992

This study was conducted to investigate the influence of addition of cetyl trimethyl ammo­nium bromide (CTAB), and amine [ethylamine (EA) or ethylene diamine (EDA)] to aqueous sodium hydroxide (NaOH) solution on polyester alkaline hydrolysis, The experimental vari­ables such as CTAB concentration, EA or EDA concentration, NaOH concentration, tempera­ture and time were compared, and the changes in physical and chemical properties of alkaline­hydrolyzed PET fabrics depending on their treated conditions were measured, The results are as follows: 1. By adding CTAB and amine in aqueous NaOH solution, increasing effect on weight loss of PET fabrics was obtained in simultaneous addition of CTAB and EDA, but not in CTAB and EA. 2. By adding CTAB & EDA simultaneously, increasing effect on weight loss was obtained regardless of EDA concentration, time and temperature, and it was more effective at lower NaOH concentration. :l. The increase of void space (or irregularly grooved surface), of softness, of wickability, of dyeability on PET fabric, and the decrease of tensile strength, of molecular weight were observed according to the weight loss on the PET fabrics. These changes were equal to all alkaline-hydrolyzed PET fabrics regardless of addition of CTAB and amine. l. There was little changes on crystallinity, thermal behavior when PET fiber was treated with ,aqueous NaOH solution with CTAB and EDA. These results supported that increasing effect on weight loss take place without inducing of fine structural change of PET fibers.

• Microbiology and Biotechnology Letters
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• v.20 no.4
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• pp.409-416
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• 1992

The optimum cultural temperature and time for the pullulanase production by Bacillus cereus were $15^{\circ}C$ and 72 hrs, respectively. The addition of casein, nutrient broth and egg albumin to the basal medium, respectively, increased greatly the enzyme production. The enzyme was purified by ammonium sulfate fractionation, CM-cellulose and DEAE-cellulose column chromatographies. The specific activity of the purified enzyme was 29.09 U/mg protein and the yield of enzyme activity was 17.1% The purified enzyme showed a single band on polyacrylamide disc gel electrophoresis and its molecular weight was estimated to be 61,000 by SDSpolyacrylamide disc gel electrophoresis. The isoelectric point for the purified enzyme was pH 7.0. The optimum temperature and pH were $40^{\circ}C$ and 6.5. The purified enzyme was stable below $35^{\circ}C$ and in the pH range of 6.5-11.0. It was greatly inhibited by $Ag^{+}$, $Hg^{2+}$ and $Zn^{2+}$, and its thermal stability was increased by the addition of $Ca^{2+}$ Among various substrates, pullulan was favorably hydrolyzed by the purified enzyme and the hydrolysis product 011 pulluIan was maltotriose.

• Korean Journal of Materials Research
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• v.23 no.10
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• pp.543-549
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• 2013

The purpose of this paper was to investigate the effect of a high-energy milling (HEM) process on the particle morphology and the correlation between a thermal treatment and tetragonal/monoclinic nanostructured zirconia powders obtained by a precipitation process. To eliminate chloride residue ions from hydrous zirconia, a modified washing method was used. It was found that the used washing method was effective in removing the chloride from the precipitated gel. In order to investigate the effect of a pre-milling process on the particle morphology of the precipitate, dried $Zr(OH)_4$ was milled using a HEM machine with distilled water. The particle size of the $Zr(OH)_4$ powder exposed to HEM reduced to 100~150 nm, whereas that of fresh $Zr(OH)_4$ powder without a pre-milling process had a large and irregular size of 100 nm~1.5 ${\mu}m$. Additionally, modified heat treatment process was proposed to achieve nano-sized zirconia having a pure monoclinic phase. It was evident that two-step calcining process was effective in perfectly eliminating the tetragonal phase, having a small average particle of ~100 nm with good uniformity compared to the sample calcined by a single-step process, showing a large average particle size of ~300 nm with an irregular particle shape and a broad particle size distribution. The modified method is considered to be a promising process for nano-sized zirconia having a fully monoclinic phase.

• Archives of Pharmacal Research
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• v.25 no.1
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• pp.39-44
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• 2002

Recently, we have reported that 2-bromopropane might have an immunotoxic potential in rats when exposed for 28 days. In the present studies, the possibility of 2i-deoxyguanosine abduct formation by 2- bromopropane was investigated in vitro to elucidate molecular mechanism of 2-bromopropane-induced immunosuppression. $N^7-Guanine adduct$ of 2'-bromopropane (i.e., $N^7-isopropyl$ guanine) was chemically synthesized and structurally characterized by analysis of UV,$^1H-NMR,{\;}^{13}C-NMR$, COSY and fast atom bombardment mass spectrometry to use as a reference material. Incubation of 2'-deoxyguanosine with an excess amount of 2-bromopropane in PBS buffer solution, pH 7.4, at $37^{\circ}C$ for 16 h, followed by a thermal hydrolysis, produced a detectable amount of $N^7-isopropyl$ guanine by an HPLC and UV analysis. The present results suggest that 2-bromopropane might form a DNA adduct in $N^7-position$ of 2'-deoxyguanosine at 3 Physiological condition.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.196-202
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• 2020

The air vent connected to a heat supply pipeline in the district heating system has been used to eliminate the existing air in the pipe, which has a detrimental effect on corrosion durability and heat efficiency. Recently, the air vent installed under a manhole for 22 years was corroded and several pinholes were detected in the front-end of the air vent. To identify the cause of the failure, thickness reduction, corrosion products, and water quality were examined. The corrosion damage was significant at the outside of the front-end of the air vent where the insulator was covered. While a thin oxide layer was formed in the interior of the tube, the coarse and porous corrosion products consisting of magnetite and hematite were found externally. Water flowing into the thermal insulator was absorbed by the insulator following hydrolysis. The hydrolyzed insulator ejected the corrosion factors such as Cl^-, SO₄^2-, and NH₄⁺. The findings suggest that the corrosion under insulation due to rain water is the main cause of the underlying failure in the air vent.

• Polymer(Korea)
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• v.37 no.4
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• pp.437-441
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• 2013

A novel sulfonate flame retardant, 1,3,5,7-tetrakis(phenyl-4-sodium sulfonate)adamantane (FR-A), was successfully synthesized from 1-bromoadamantane in sequential four-step reactions involving Fiedel-Crafts phenylation, sulphonation, hydrolysis, and neutralization. The success of synthesis was confirmed by FTIR spectra, $^1H$ NMR spectra, elemental analyses and mass spectra. The effect of FR-A on the flame retardacy of polycarbonate (PC) has been studied. Limiting oxygen index (LOI) and thermogravimetric analysis (TGA) showed that this novel sulfonate flame retardant had effective flame retardancy on polycarbonate (PC). With a small amount (0.08 wt%) of FR-A, the flame retardancy of PC was improved obviously, which got to UL 94 V-0 rating. TGA and DTA curves demonstrated that the additive raised the degradation rate of PC by promoting the quick formation of an insulating carbon layer on the surface, and confirmed that the flame retardant mechanism of PC/FR-A system was similar to potassium diphenylsulfone sulfonate (KSS).