• Fire Science and Engineering
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• v.28 no.5
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• pp.8-13
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• 2014

The purpose of this study is to analyze the damage pattern when overcurrent is applied to a thermal magnetic type molded case circuit breaker (MCCB) using a Primary Current Injection Test System (PCITS). When an overcurrent of 150 A was applied to the PCITS for 5 seconds with the trip bar of an MCCB being damaged, it was found that the surface of the temperature control device (bimetallic strip) positioned at the right was significantly carbonized. When an overcurrent of 300 A was applied to the PCITS for 5 s under the same conditions, the entire temperature control device was deteriorated, becoming flattened and in close contact with the MCCB. When an overcurrent of 450 A was applied to the PCITS for 5 s, the coil of the temperature control device was melted and disconnected. In addition, it was observed that the contacts, the enclosure and upper cover were deformed and there was a trace of carbonization on them. When approximately 3 s had elapsed after an overcurrent of 600 A was applied, white smoke occurred inside the MCCB and a flame was radiated out, after which the overcurrent supply stopped with "phutt" (whomp) sound. It was observed that when the same type of MCCB is damaged by a general flame, the surfaces of its handle, terminal, arc divider (extinguisher) and temperature control device were carbonized uniformly. In addition, it was found that the trip bar of the operating mechanism was melted down and the metal operation pin was moved while being tripped.

• Conservation Science in Museum
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• v.4
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• pp.23-32
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• 2003

As the kettle excavated from a site in Hwangnam-dong, Gyeongju was presumed to have been used as a melting crucible in a glass production workplace, we decided to prove its usage by scientific analysis. First, we performed conservation treatment to find the original status of the kettle, and then SEM-EDS and XRD analysis of the five corrosions created on the surface of the kettle. The fragment of the spout, which played a crucial role for the kettle to be considered as a melting crucible, was discovered during the conservation treatment. So the mouth rim of the kettle was restored to perfection. When we observed the microstructure of the metal sample, it was proved to be cast iron gradually cooled without heat treatment. In the corrosion products, the main components were Fe and O and other components such as P, Si, Ca, and S were found. The main compounds were quartz, vivianite, goetheite, akaganite, lepidocrocite, hematite, etc. Although these components were used as raw materials for making glass, these were found not in the melting status but mere raw materials. This can be an evidence to show these site where the kettle was excavated had been a glass production workplace. However, it is not sure that the kettle was used as a melting crucible. Moreover, if we consider the organic mold and sand clay accumulated in the well site when the kettle was excavated at first, we can see this as a formative factor of the corrosions of the kettle. Therefore, we concluded that the kettle is a typical cast iron and was not used as a melting crucible of glass.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• Journal of Environmental Science International
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• v.2 no.2
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• pp.123-133
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• 1993

Shingal reservoir is a relatively small (211ha) and shallow impoundment, and approximately 25 ha of its sediment is exposed after spring drawdown. At least 14 vascular p13n1 species germinate on the exposed sediment, but Persimria vulgaris Webb et Moq. quickly dominates the vegetation. In order to estimate the role of the vegetation in the dynamics of heavy metal pollutants in the reservoir, Cu concentration of water, fallout particles, exposed sediment, and tissues of p. vulgaris, Ivas analyzed. Cu content in reservoir water decreased from $13.10mg/m^2$ on May 15 (before dralvdown) to $3.08mg/m^2$ in June 1 (after drawdown), mainly due to the loiwering of water level. Average atmospheric deposition of Cu by fallout particles was $10.84 {\mu}g/m^2/day$. Cu content in the surface 15cm of exposed sediment decreased from $5.094g1m^2$ right after drawdown, to $0.530g/m^2$ in 41 days, which is a 89.6% decrease. Therefore up to 99.7% of Cu in the reservoir appears to exist in the sediment. only 0.3% in water If the rate of atmospheric Input by fallout particles is assumed to have been the same since 1958, when the reservoir was completed, cumulative input of Cu during the 38 years would have been $150.35mg/m^2$, which is only 3.0% of Cu content in sediment right after drawdown. Therefore, most of Cu in the Shingal reservoir must have been transported by the Shingal-chun flowing into the reservoir, Standing crop of vegetation on the exposed sediment 41 days after drawdown was $730.67g/m^2$, of which 630.91g/m2 was p. vulgaris alone, and Cu content in P vulgaris at this time was $6.612mg/m^2$. This was only 0.13% of Cu in the exposed sediment, but was 50.5% of Cu in water before drawdown, or 167% of the average annual input of Cu by atmospheric deposition. If other plants were assumed to absorb Cu to the same concentration as p. vulgaris, total amount of Cu absorbed in 41 days by vegetation on the exposed sediment is estimated to be 1913.3 g, which is a considerable contribution to the purification of the reservoir water.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1047-1053
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• 2016

In this study, welding of pure titanium was carried out by using a continuous wave fiber laser with a maximum output of 6.3 kW. Because brittle regions form easily in titanium as a result of oxidation or nitriding, the weld must be protected from the atmosphere by using an appropriate shielding gas. Experiments were performed by changing the type and the flow rate of shielding gases to obtain the optimal shielding condition, and the weldability was then evaluated. The degree of oxidation and nitriding was distinguished by observing the color of beads, and weld microstructure was observed by using an optical microscope and a scanning electron microscope. The mechanical properties of the weld were examined by measuring hardness. When the weld was oxidized or nitrified, the bead color was gray or yellow, and the oxygen or nitrogen content in the bead surface and overall weld tended to be high, as a result of which the hardness of the weld was thrice that of the base metal. A sound silvery white bead was obtained by using Ar as the shielding gas.

• Journal of Environmental Science International
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• v.2 no.2
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• pp.29-29
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• 1993

Shingal reservoir is a relatively small (211ha) and shallow impoundment, and approximately 25 ha of its sediment is exposed after spring drawdown. At least 14 vascular p13n1 species germinate on the exposed sediment, but Persimria vulgaris Webb et Moq. quickly dominates the vegetation. In order to estimate the role of the vegetation in the dynamics of heavy metal pollutants in the reservoir, Cu concentration of water, fallout particles, exposed sediment, and tissues of p. vulgaris, Ivas analyzed. Cu content in reservoir water decreased from $13.10mg/m^2$ on May 15 (before dralvdown) to $3.08mg/m^2$ in June 1 (after drawdown), mainly due to the loiwering of water level. Average atmospheric deposition of Cu by fallout particles was $10.84 {\mu}g/m^2/day$. Cu content in the surface 15cm of exposed sediment decreased from $5.094g1m^2$ right after drawdown, to $0.530g/m^2$ in 41 days, which is a 89.6% decrease. Therefore up to 99.7% of Cu in the reservoir appears to exist in the sediment. only 0.3% in water If the rate of atmospheric Input by fallout particles is assumed to have been the same since 1958, when the reservoir was completed, cumulative input of Cu during the 38 years would have been $150.35mg/m^2$, which is only 3.0% of Cu content in sediment right after drawdown. Therefore, most of Cu in the Shingal reservoir must have been transported by the Shingal-chun flowing into the reservoir, Standing crop of vegetation on the exposed sediment 41 days after drawdown was $730.67g/m^2$, of which 630.91g/m2 was p. vulgaris alone, and Cu content in P vulgaris at this time was $6.612mg/m^2$. This was only 0.13% of Cu in the exposed sediment, but was 50.5% of Cu in water before drawdown, or 167% of the average annual input of Cu by atmospheric deposition. If other plants were assumed to absorb Cu to the same concentration as p. vulgaris, total amount of Cu absorbed in 41 days by vegetation on the exposed sediment is estimated to be 1913.3 g, which is a considerable contribution to the purification of the reservoir water.

• Restorative Dentistry and Endodontics
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• v.30 no.4
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• pp.327-334
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• 2005

This study investigated the effect of anticurvature filing method on preparation of the curved root canal using ProFile. Thirty six resin blocks were divided equally into three groups by instrumentation motions: anticurvature filing motion. circumferential filing motion and straight up-and-down motion. Each resin block was sectioned at 8mm level from the apex and at the greatest curvature of the canal and reassembled in metal mold by a modified Bramante technique. All groups were instrumented with the ProFile system. At each levels. image of sectioned surface were taken using CCD camera under a stereomicroscope at $\times40$ magnification and stored. Distances of transportation at the inner and outer area of curvature and the centering ratio were determined and compared by statistical analysis. along with the assessment of the increase of root canal cross-sectional area. The results were as follows; 1. In all groups. there was no statistical difference in the mean increase of root canal cross-sectional area. the centering ratio. and the mean distances of transportation at the inner area of curvature at each level. 2. At 8mm level from the apex. the mean distances of transportation at the outer area of curvature decreases in following order anticurvature filing motion. circumferential filing motion. straight up-and­down motion but. no significant difference at the greatest curvature of the canal among three groups. Effect of anticurvature filing motion using ProFile does not seem to be different from other instrumentation motions at the inner area of curvature in curved root canal.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.291-298
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• 2016

Electrochemical water treatment process as a useful treatment method for the removal of non-degradable matter has been consistently studied for several decades. Key process of electrochemical water treatment are oxidation reaction from an anode and reduction from a cathode. In this study, the effect of pre-treatment methods in the insoluble electrode manufacturing process for the water treatment has been evaluated for the life time of electrode The results of this study showed that pre-treatment methods of a base metal such as surface roughness, clean method and interlayer formation influenced to life time of electrode when the same condition (catalyst electrode layer coating method and material system) was applied for pre-treatment methods. This study was conducted by using $IrO_2/Ti$ electrode In the test of sand-blasting process, an electrode manufactured by using sanding media of different sizes resulted in the most effective electrode life time when the size of alumina was used for $212{\sim}180{\mu}m$ praticle size (#80). The most effective method was considered using arc plasma in the additional roughness control and cleaning process, sputtering method to form Ta type interlayer formation process.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.51-58
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• 2017

We investigated the efficiency of natural zeolite with different cation exchange capacity (CEC) as capping material for the remediation of marine sediments contaminated with heavy metals. Three different zeolite with high CEC (HCzeo, 163.74 cmolc/kg), medium CEC (MCzeo, 127.20 cmolc/kg), and low CEC (LCzeo, 70.62 cmolc/kg) were used. The surface area of the zeolite was in decreasing order: HCzeo ($59.43m^2/g$) > MCzeo ($52.10m^2/g$) > LCzeo ($10.12m^2/g$). The results of mineralogical composition obtained from X-ray diffraction (XRD) show that LCzeo was mainly composed of quartz and albite. In the XRD result of MCzeo and HCzeo, the peaks of clinoptilolite, heulandite, and mordenite were also observed along with that of quartz and albite. Sorption equilibrium onto the HCzeo, MCzeo, and LCzeo was reached in 6 h at initial concentration of 10 mg/L and 100 mg/L. Higher adsorption of Cd and Zn onto the zeolite with higher CEC were achieved but adsorption of Cu and Ni were not dependent on the CEC of zeolite. It can be concluded that the zeolite with high cation exchange ability is recommended for the contaminated sediments with Cd and Zn but the inexpensive zeolite with low CEC for Cu and Ni.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2010.03a
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• pp.40-40
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• 2010

Studies on attractive color changing property of dye chromophore and fluorophore have been greatly enjoyed in the related industrial and research fields such as optoelectronics, chemosensor, biosensor and so on. The optical property based on D-$\Pi$-A intramolecular charge transfer (ICT) system of chromophore molecules can be utilized as suitable sensing probes for checking media polarity and determining colorimetric chemosensing effect, especially heavy metal detection. These finding are obtained by absorption and emission properties. In this work, donor-acceptor D-$\Pi$-A type fluorescent dyes were designed and synthesized with the corresponding donor and acceptor groups. The selected donor moieties might be provided prominent amorphous properties which are very useful in designing and synthesizing functional polymers and in fabricating devices. Another reasons to choose are commercial availabilities in high purity and low price. Donor-bridge-acceptor (D-A) type dyes can produce impressive optical-physical properties, yielding them potentially suitable for applications in the synthesis of small functional organic molecules. Small organic functional molecules have unique advantages, such as better solubility, amorphous character, and represent an area of research which needs to be explored and developed. Currently, their applications in metalorganic compounds is rapidly expanding and becoming widespread in self-assembly processes, photoluminescence applications, chiral organocatalysts, and ingrafts with nanomaterials. Colloidal nanoparticles have received great attentions in recent years. The photophysical properties of nanoparticles, particularly in terms of brightness, photostability, emission color purity and broad adsorption range, are very attractive functions in many applications. To our knowledge background, colloidal nanoparticles have been enjoyed their applications in bio-probe research fields. This research interest can be raised by the advantages of the materials such as high photoluminescence quantum yields, sharp emission band, long-term photostability and broad excitation spectra. In recent, the uses of nanoparticles being embedded in a polymer matrix and binded on polymer surface have been explored and their properties such as photo-activation and strong photoluminescence have been proposed. The prepared chromophores and nanoparticles were investigated with absorption and emission properties, solvatochromic behaviors, pH induced color switching effects, chemosensing effects and HOMO/LUMO energy potentials with computer simulation. In addition, synthesized fluorophore dyes and particles were applied onto PE/Aramid fiber fluorescing colorations. And the related details were then discussed.