• The Journal of Korean Academy of Prosthodontics
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• v.27 no.1
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• pp.31-47
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• 1989

The purpose of this study was to evaluate the chemical bond strength of successively recast Pd-Ag ceramic alloys with porcelain and to investigate changes of quantity of trace elements at the metal-porcelain interface. Porcelain was fired as usual manner on the each successively recast specimen. Rectangular planar shear test was performed and bond strength was measured by Instron universal testing machine. Diffusion of trace elements at the each interface was observed by ESCA (Electron Spectroscopy for Chemical Analysis). The obtained results were as follows : 1. Chemical bond strength was significantly decreased after second recasting. But in case of first recasting, there was no significant decrease of bond strength statistically (p<0.05). 2. Bond strength was not significantly decreased in each generation, when fifty percents new alloy was added (p<0.05). 3. Ag, Sn and In were observed at the porcelain interface. But Pd was not observed. 4. The quantity of Ag, In ions were progressively increased at the metal-porcelain interface as the casting was repeated. Silver ion was most significantly increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.276-276
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• 2013

Here we report an integrated microdevice consisting of an efficient passive mixer, a magnetic separation chamber, and a capillary electrophoretic microchannel in which DNA barcode assay, target pathogen separation, and barcode DNA capillary electrophoretic analysis were performed sequentially within 30 min for multiplex pathogen detection at the single-cell level. The intestine-shaped serpentine 3D micromixer provides a high mixing rate to generate magnetic particle-pathogenic bacteria-DNA barcode labelled AuNP complexes quantitatively. After magnetic separation and purification of those complexes, the barcode DNA strands were released and analyzed by the microfluidic capillary electrophoresis within 5 min. The size of the barcode DNA strand was controlled depending on the target bacteria (Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella typhimurium), and the different elution time of the barcode DNA peak in the electropherogram allows us to recognize the target pathogen with ease in the monoplex as well as in the multiplex analysis. In addition, the quantity of the DNA barcode strand (~104) per AuNP is enough to be observed in the laser-induced confocal fluorescence detector, thereby making single-cell analysis possible. This novel integrated microdevice enables us to perform rapid, sensitive, and multiplex pathogen detection with sample-in-answer-out capability to be applied for biosafety testing, environmental screening, and clinical trials.

• Analytical Science and Technology
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• v.27 no.4
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• pp.201-212
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• 2014

Polycyclic aromatic hydrocarbons (PAHs) that are carcinogenic and persistent will be restricted in consumer products from December 27, 2015 by EU REACH regulation. Pretreatment using Soxhlet extraction and quantitative analysis by GC-MS were studied to develop the method for analyzing 18 PAHs in consumer products as well as to detect the amounts and the kinds of PAHs in consumer products such as grips of a bag and a hammer, a cable and a plastic sandal. Linearity and precisions were evaluated by analyses of the standard PAH solutions ranging from 0.3125 mg/L to 5.00 mg of each of 18 PAHs. Linearity of resulting standard curves for all 18 PAHs were obtained with $R^2$ above 0.999. Precisions of the retention times and the peak areas were found to be 0.00%~0.05% and 1.16%~3.69% of relative standard deviations, respectively. The recoveries for spiked samples were all around 95%~105% after Soxhlet extration using three different solvents such as dichloromethane, hexane and toluene. The limits of quantitation for 18 PAHs in solutions and polymer samples by GC-MS were evaluated to be 0.327 mg/L (Benzo[ghi]perylene)~0.464 mg/L (Acenaphthylene) and 1.635 mg/kg (Benzo[ghi]perylene)~2.32 mg/kg (Acenaphthylene) based upon dilution factor of 5, respectively. Under the developed analytical method, only trace amounts of phenanthrene were detected in three samples while 15 kinds of PAHs including phenanthrene were detected in a grip of hammer with concentrations of maximum 83.4 mg/kg of Phenanthrene and minimum 8.5 mg/kg of Acenaphthylene. Further studies are needed to decrease the quantitation limit and to check the feasibility of decreasing Soxhlet time as well as to demonstrate cases that the clean up is required.

• Korean Journal of Environmental Agriculture
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• v.39 no.2
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• pp.95-105
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• 2020

BACKGROUND: In this study, in order to verify the effects of supplemented organic amendment fertilizers recommended by the soil testing on cabbages, we used various amounts of organic amendment fertilizers. The amount of organic amendment fertilizers was decided by calculating each ratio of inorganic nitrogen, phosphorus, and potassium based on the recommended fertilizer composition. METHODS AND RESULTS: The cabbages subjected to treatments 1 and 2 showed similar or greater leaf colors (SPAD values), head heights, head widths, head weight, soil organic matter content, nitrate-nitrogen level, and conductivity after harvest, when compared with cabbages treated with chemical fertilizers. The phosphorus and potassium fixation in the soil were higher in the plot where cabbages were treated with chemical fertilizers, and the nutrient use efficiency was greater in the plots with organic amendments and mineral addition. CONCLUSION: The treatments 1 and 2 that were supplemented with 180-200% of nitrogen, 100-130% of phosphorus, and 185-250% of potassium in comparison to chemical fertilizers, applied by the inorganic ratios of nitrogen, phosphorus, and potassium can be used as organic amendment fertilizers for cabbages.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.355-363
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• 2024

Although copolymer aramid is a fiber with excellent flexural performance, there is no test method to evaluate flexural fatigue performance. Various studies are currently being conducted in korea to develop copolymer aramid, and in order to develop the reliability of aramid fibers to a global level, it is necessary to develop a test method to evaluate the flexural fatigue performance of aramid fibers. In this study, we developed an test equipment and test method that can evaluate the flexural fatigue performance of copolymer aramid and analyzed the flexural fatigue performance of aramid fiber. Flexing rollers are made of ceramic materials and rotating shapes to minimize friction. The diameter of the roller was set to 10 mm by calculating the minimum allowable curvature. The B₁₀ life was calculated through a flexural fatigue test, and the para-aramid was 125,770 cycles, the copolymer aramid was 598,150 cycles, and the aramid nano fiber(ANF) coated copolymer aramid was 589,073 cycles. Through the S-N diagram, the fatigue life relationship according to the load change was confirmed. copolymer aramid fibers exhibit better flexural fatigue performance than para-aramid fibers at high loads. The ANF coated copolymer aramid also exhibits excellent flexural fatigue performance.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.436-446
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• 2020

In this study, we verified the effects of organic amendment application based on soil testing in potato cultivation. The application rate of organic amendments was determined based on the inorganicization rate of nitrogen, phosphoric acid, and potassium in the organic amendments. There was no significant difference in the length, stalk number, stalk diameter, and leaf color of potato plants under organic amendment application compared with those under chemical fertilization. The quantity of potato tubers and yield of marketable tubers under organic amendment application were higher than those under chemical fertilization. The top fresh weight and top-to-root ratio were the highest under organic amendment application, followed by those under chemical fertilization and the control. The inorganic nitrogen content in the leaves and stems of potato plants was the highest under chemical fertilization. There was no difference in the phosphoric acid content between the potatoes under chemical fertilization and those under organic amendment application. The potassium content in potatoes was higher under chemical fertilization than that under organic amendment application. While the change trend of inorganic nitrogen content in the roots was similar to that in the leaves and stems, the potatoes under organic amendment application, with the highest yield, showed the highest dry weight. The tuber weight showed a positive correlation with plant length, stalk number, and stalk diameter. The higher the weight of the tuber, the higher the weight of the marketable tuber, and the higher the top fresh weight, the higher the yield. Therefore, to increase yield, it is necessary to supply nutrients to improve the top fresh weight to the optimal level. There was no difference in the utilization efficiency of nitrogen and potassium between the potatoes under chemical fertilization and those under organic amendment application. The utilization efficiency of phosphoric acid was increased by 0.1% in potatoes under organic amendment application compared with that under other treatments. Regarding soil chemistry after harvest, the soils under organic amendment application showed a higher electrical conductivity and higher nitrogen and phosphoric acid content than those under other treatments. Therefore, the organic amendment method used in this study can be an alternative to chemical fertilization. It is also advantageous for the cultivation of subsequent crops in potato fields.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.247-252
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• 2012

Crystal structure and chemical compositions of Plasma electrolytic oxidized layer of A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for plasma electrolytic oxidation was mixture of distilled water, $Na_2P_2O_7$, Cu, Cr metal salts and KOH. ${\eta}$-Alumina, as well as ${\alpha}$-alumina, was main crystal phase. Another crystals such as $(Al_{0.948}Cr_{0.052})_2O_3$ and $(Al_{0.9}Cr_{0.1})_2O_3$ were also formed in the oxide layer. It was thought that the effect of electrolyte compositions on the physical properties and crystal system of PEO layers was greater than the effect of Al alloy composition variation.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• Safety and Health at Work
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• v.10 no.1
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• pp.125-129
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• 2019

The ultimate goal of the quality control program for special periodic health examination agencies is to diagnose the health condition of a worker correctly, based on accurate examination and analysis skills, leading to protect the worker's health. The quality control program on three areas, chemical analysis for biological monitoring since 1995, and pneumoconiosis, audiometric testing since 1996, has contributed to improve the reliability of occupational health screenings by improving the issues including standardization of testing methods, tools, diagnostic opinions, and reliability of analysis for biological monitoring. It has contributed to improving the reliability of occupational health monitoring by rectifying the following issues associated with previous monitoring: absence of standardized testing methods, testing tools that are not upgraded, mismatching diagnostic opinions, and unreliable results of biological specimen analysis. Nevertheless, there are issues in need of further improvement such as lack of expertise or the use of inappropriate method for health examination, and passive and unwilling participation in the quality control. We suggested solutions to these problems for each area of quality control program. Above all, it is essential to provide active support for health examiners to develop their expertise, while encouraging all the health screening agencies, employers, and workers to develop the desire to improve the system and to maintain the relevance.

• Fashion & Textile Research Journal
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• v.25 no.3
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• pp.398-408
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• 2023

Smart clothing products can experience a decrease in performance and reliability due to various mechanical, biological, and chemical stress factors that occur throughout their life cycle. These issues can hinder consumer acceptance of the products. This study aims to enhance the reliability of smart clothing and facilitate quality control by analyzing and identifying the current status of international standardization for smart clothing and electronic textiles (e-textiles). The focus of this analysis was on the durability test methods in the use environment. Furthermore, similar standards published by different standardization organizations for durability tests were compared in depth. The study showed that a total of 27 international standards have been developed or are currently under development. The current standardization efforts mainly aim to develop functionality and durability test methods for smart clothing and e-textile products. A detailed comparison was made between two international standards (IEC 63023-204-1:2023 and AATCC TM210:2019) specifically in relation to the washing durability test method and the electrical resistance measurement standards (BS EN 16812:2016 vs AATCC EP13-2021), before and after the environmental exposure tests. Based on this comparison, several suggestions have been made and discussed for the future revision of these international standards.