• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.494-497
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• 2006

For commercialization of polymer electrolytemembrane fuel cell (PEMFC), durability of membrane electrode assemblies (MEAs) has to be improved. Especially, long-term stability of MEA is one of the most important issues for frequent shut-down and start-up processes of PEMFC. The degradation of MEA could be attributed to chemical attack of hydrogen peroxide radicals that are formed at high cell voltages without any special treatment to remove residual hydrogen from anode gas channel after shut-down of the fuel cell. In this study, we investigated the long-term stability of MEA under different on/off operation conditions. Residential hydrogen gas was removed from the anode flow channel by purging air or nitrogen. Also, a dummy resistance was applied to the fuel cell to exhaust residential hydrogen at the anode. In these cases, MEA showed much more stable durability. Electrochemical characteristics of the fuel cell were measured byrepeating the on/off cycles with the hydrogen removal processes. Also, degradation of MEA components was examined by SEM, TEM and XRD analyses.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.4
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• pp.207-211
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• 2007

The durable lifetime of RC structures is shortened by various reasons, which are the generation of cracks in construction and service term, the exterior deterioration according to climatic condition, the surface damage due to chloride attack and the corrosion of reinforced bars. The durability of concrete structures is nevertheless able to be increased by the method and the material of reinforcement and repair. The epoxy resin is widely used for reinforment and repair of concrete because of the superiority in mechanical property, adhesive property, abrasion resistance, impact resistance and chemical resistance. The epoxy cement mortar with hardening agent has a lot of disadvantages that are troublesome mixing work, weakened weatherability and high cost for hardening agent. In this study, the mix proportion of mortar is presented just only with epoxy resin and some admixtures, and the test result of mortar without hardening agent shows the higher strength than the mortar with hardening agent. In the mix proportion, the weight of epoxy resin must be less than 15% of the unit weight of cement, and 10% of unit weight of cement is adequate for the weight of admixtures.

• The Journal of Engineering Research
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• v.8 no.1
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• pp.31-50
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• 2006

Shrinkage may cause cracking in concrete. In practice such cracking must be considered in most concrete applications because, under normal conditions, drying of the concrete is unavoidable, and when drying takes place shrinkage occurs. Cracked concrete is an inferior concrete because it is weaker, more permeable, and more susceptible to chemical attack. The development of the strength of LAC with aging depends on a few factors such as type of the cement, W/C ratio, curing conditions and periods. The higher the strength of LAC, the lower the possibility of shrinkage cracking. Hence, the strength of LAC in the hypocaust system depends to a large extent on the effect of cracking decrease of the antifoaming rate to drying shrinkage in cement.

• Journal of The Korean Digital Architecture Interior Association
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• v.13 no.4
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• pp.61-68
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• 2013

Concrete structure is not the only material vulnerable to physical and chemical processes of deterioration associates with severe conditions. Deterioration of the concrete structure, however, occurs more progressively from the outside of the concrete exposed to severe conditions. Especially, Carbonation, chloride ion attack is more important factor of concrete durability. This study is interested in manufacturing the self-cleaning concrete surface impregnant including TEOS, lithium silicate for the repair of the exposed concrete surface and the color concrete requiring the advanced function in view of the concrete appearance. Form the results, TEOS and lithium silicate are very effective that increasing the concrete durability using self-cleaning concrete impregnant. Self-cleaning concrete impregnant specimens is satisfied with performance requirement of KS standard in adhesion test in tension but the reinforcement of concrete substrate is slight. So, the self-cleaning concrete impregnant of this study is more desirable for the improvement of durability rather than the reinforcement.

• The Plant Pathology Journal
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• v.21 no.3
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• pp.288-292
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• 2005

Pathogenesis-related protein-1a (PR-1a) is strongly induced in tobacco plants by pathogen attack, exogenous salicylic acid (SA) application and by other developmental processes. In order to develop a rapid screening system for the selection of plant defense-inducing compounds originated from various sources, we have transformed tobacco Samsun NN plants with a chimeric construct consisting of GUS $(\beta-glucuronidase)$. In the $T_1$ generation, three transgenic lines having stable GUS expression were selected for further promoter analysis. Using GUS histochemical assay, we observed strong GUS induction driven by PR-1a promoter in PR1a-GUS transgenic tobacco leaves in response to the exogenous application of SA or benzol (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH), a SA­derivative compound. In addition, GUS expression was maintained locally or systemically in PR1a-GUS transgenic line $\#5\;T_2$ generation) until after 3 days when they were treated with same chemicals. Our results suggested that the PR1a-GUS reporter gene system in tobacco plants may be applicable for the large-scale screening of defense-inducing substances.

• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.49-58
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• 2000

There are many methods to improve the performance of concrete. Especially, granuated blast furnace slag. by-products used in concrete as the replacement material of cement, could contribute to improve the fluidity, resistance of chemical attack and strength of concrete. Also, it could contribute to decrease the rate of generating hydration heat, in addition to cost-down of concrete and prevention of enviromental pollution. Therefore, in order to establish the systemical application of granuated blast furnace slag in normal concrete, the engineering properties of concrete, such as fluidity, strength, setting and hydration properties etc.. was evaluated. In this study, replacement ratio of granuated blast furnace slag was 0, 30, 50, 70(%), and target slump was 8, 12, 15, 18(cm). Results from the experiment, granuated blast furnace slag showed the outstanding effects of improving the engineering properties of concrete. From now on, positive application of granuated blast furnace slag is expected in the point of improving the performance and cost-down of concrete.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.97-103
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• 2007

A novel selective metallization process to fabricate the fine conductive line based on inkjet printing has been investigated. Recently, Inkjet printing has been widely used in flat panel display, electronic circuits, biochips and bioMEMS because direct inkjet printing is an alternative and cost-effective technology for patterning and fabricating objects directly from design without masks. The photosensitive etching resist used in this process is an organic polymer which becomes solidified when exposed to ultraviolet lights and has high viscosity at ambient temperature. A piezoelectric-driven inkjet printhead is used to dispense 20-30 ${\mu}m$ diameter droplets onto the copper substrate to prevent subsequent etching. Repeatability of circuitry fabrication is closely related to the formation of steady droplets, adhesion between etching resist and copper substrate. Therefore, the ability to form small and stable droplets and surface topography of the copper surface and chemical attack must be taken into consideration for fine and precise patterns. In this study, factors affecting the pattern formation such as adhesion strength, etching mechanism, UV curing have been investigated. As a result, microscale copper patterns with tens of urn high have been fabricated.

• Mycobiology
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• v.30 no.1
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• pp.37-40
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• 2002

The susceptibility of radiata pine sapwood to fungal attack and the ability of selected fungicides to control colonization of sapstain and mold fungi on green radiata pine sapwood were evaluated. Radiata pine sapwood was highly susceptible to fungal staining, suggesting that prompt application of fungicides after sawing is essential for preventing fungal colonization. The ability of commercial fungicides to prevent fungal discoloration on radiata pine sapwood was assessed using an accelerated 6-week test on small samples in the laboratory, and in field tests using bulk-piled boards exposed outdoors for 6 weeks during summer rainy season. In laboratory tests, Hylite extra provided excellent protection against fungal discoloration even at the lowest concentrations. Hylite clear, Britewood S, and NP-1 Plus provided good short-term protection(2 to 4 weeks), but higher chemical loadings were, required for long-term protection(6 weeks). Woodguard produced little or no protection over the test periods. In field tests, Kathon 893 provided markedly superior protection at the concentration of 0.5 percent or higher. NP-1 Plus provided relatively good protection at all concentrations evaluated. Hylite extra was effective only for short-term protection(2 to 4 weeks) at all concentrations tested, but higher solution strengths were needed for longterm protection.

• Journal of The Korean Dental Society of Anesthesiology
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• v.6 no.2 s.11
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• pp.121-126
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• 2006

Generalized anaphylaxis is a most dramatic and acutely life-threatening allergic reaction. Most fatalities from anaphylaxis occur within the first 30 minutes postantigenic exposure. The mechanism of generalized anaphylaxis is the reaction of IgE antibodies to an allergen that causes the release of histamine, bradykinin, and others. These chemical mediators cause the contraction of smooth muscles of the respiratory and intestinal tracts, as well as increased vascular permeability. Four major clinical symptoms are recognized: skin reactions, smooth muscle spasm (gastrointestinal and genitourinary tracts and respiratory smooth muscle), respiratory distress, and cardiovascular collapse. Epinephrine is the drug of choice for the management. Its syrnpathomimetic effects directly counteract most aspects of the attack. Respiration must be immediately supported by the establishment of a patent airway along with artificial ventilation. The circulation should be supported and the existing hypotension overcome by placing the victim in a position to allow gravity to aid venous return and by administering intravenous fluids, vasopressors, and corticosteroids. When an imperceptible pulse is evident, external cardiac compression must also be instituted. This is a case report of anaphylactic shock care during general anesthesia, possibly due to penicillin, pancuronium and others.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.507-521
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• 1994

Bentonite occurs in the Janggi Conglomerate of Tertiary age and consists mainly of montmorillonite with Mg as predominant interlayer cations. The bentonite was reacted with various concentrations of sulfuric acid (0.8~1.5M) for various reaction time (1-10h) at $103^{\circ}C$. Cation exchange capacity, exchangeable cations, surface area and solid acidity of the original bulk and acid activated bentonites were measured. Chemical analysis, X-ray diffraction, differential thermal analysis and infrared spectroscopy were used to characterize the changes in structure and properties of the acid activated bentonite. The dissolution of octahedral cations occurs not only from the edge of the clay platelets but also throughout the whole clay structure creating vacant octahedral sites. These lattice defects are created by $H^+$ diffused into the smectite layers. The cations leached possibly from the octahedral sheets are adsorbed on the interlayer exchange sites. They are exchanged with hydronium ions again by stronger acid attack. These reactions create wedge-shaped pores resulting in the increase of the surface area and the changes the morphology in the lattice structure.