• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1563-1568
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• 2003

The introduction of invasive marine species of living things into new environments by ship's ballast water, attached to ships' hulls and via other vectors has been identified as one of the four greatest threats to the world's oceans by Global Environment Facility(GEF). Making use of the new technology of alpha-AL$_2$O$_3$ dielectric barrier layer, the strong electric-field gas discharge was introduced and obtained between micro-gap electrodes at high pressure (∼105㎩) of $O_2$ in air and $H_2O$ in seawater. The mixed air with $H_2O$ could be ionized and dissociated into large numbers of activated particles of OH, $O_2$＋, O(1D), HO$_2$ and so on, and then dissolved into the ballast water to form dissolved hydroxyl radical with the concentration of ∼20mg/L. Therefore, the invasive marine species was treated effectively through the hydroxyl radical dissolved pipeline of ballast water by strong electric -field discharge.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.180-186
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• 2005

This paper discusses the development of mixtures for silica fume as a stabilization/solidification agent and a binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (unconfined compressive strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC (total organic carbon) and chromium decreased as more OPC (Ordinary Portland Cement) was substituted with the silica fume. When a mixture had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76 mg-Cr/g-Cr in acidic solution. Also, microstructural studies of the solidified analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contrilbute to setting but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and the contaminant leachability.

• Journal of Electrochemical Science and Technology
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• v.10 no.1
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• pp.22-28
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• 2019

To maximize the oxygen evolution reaction (OER) in the electrolysis of water, nano-grade $IrO_2$ powder with a low specific surface was prepared as a catalyst for a solid polymer electrolyte (SPE) system, and a membrane electrode assembly (MEA) was prepared with a catalyst loading as low as $2mg\;cm^{-2}$ or less. The $IrO_2$ catalyst was composed of heterogeneous particles with particle sizes ranging from 20 to 70 nm, having a specific surface area of $3.8m^2g^{-1}$. The anode catalyst layer of about $5{\mu}m$ thickness was coated on the membrane (Nafion 117) for the MEA by the decal method. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) confirmed strong adhesion at the interface between the membrane and the catalyst electrode. Although the loading of the $IrO_2$ catalyst was as low as $1.1-1.7mg\;cm^{-2}$, the SPE cell delivered a voltage of 1.88-1.93 V at a current density of $1A\;cm^{-2}$ and operating temperature of $80^{\circ}C$. That is, it was observed that the over-potential of the cell for the oxygen evolution reaction (OER) decreased with increasing $IrO_2$ catalyst loading. The electrochemical stability of the MEA was investigated in the electrolysis of water at a current density of $1A\;cm^{-2}$ for a short time. A voltage of ~2.0 V was maintained without any remarkable deterioration of the MEA characteristics.

• Journal of Environmental Science International
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• v.30 no.9
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• pp.727-739
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• 2021

Measurements on mass size distribution of roadside aerosols were obtained in downtown Jeju City from July 2018 to May 2020 using an 8-stage cascade impactor sampler and the compositions of aerosols were analyzed. The mass size distribution of total aerosols was bimodal with aerosols existing in both the fine and coarse modes. The mass size distributions of Na⁺, Mg²⁺, Ca²⁺, Cl^-, NH₄⁺ and SO₄^2- were unimodal, whereas that of K⁺ was bimodal. For NO₃^-, the size distribution in winter and spring was bimodal with the peaks in both fine and coarse modes, whereas for summer and autumn the distribution was unimodal with a peak in the coarse mode. NH₄⁺ was found to co-exist with SO₄^2- in the fine mode with an average molar ratio of [NH₄⁺]/[SO₄^2-] equal to 2.05. Good correlation was observed between NO₃^- and NH₄⁺ in the fine mode particles in spring and winter. Based on the value of the marine enrichment factor for Cl^-, Mg²⁺, K⁺, Ca²⁺ and SO₄^2-, it may be inferred that a major part of the roadside aerosols in downtown Jeju City was largely contributed by terrigenous sources, although the influence of sea salt was normally present.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.287-295
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• 2023

Iron nanoparticles (Fe-NPs) were synthesized employing Lagenaria siceraria (LS) leaf aqueous extract as a reducing and capping medium to remove methylene blue (MB) dye and have antibacterial properties against G-negative (Escherichia coli) and G-positive bacteria (Staphylococcus aureus). The formation of LS-Fe-NPs (Lagenaria-siceraria-iron-nanoparticles) was confirmed by a change in color from pale yellow to dark brown. Characterization techniques, such as particle size analysis (PSA), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), were employed to prove nano spherical particles of size range between 80-100 nm. Phytochemicals and the presence of iron in LS-Fe-NPs nanoparticles were proved by UV-visible spectrophotometry. Further, Fourier transform infrared spectroscopy (FTIR) analysis results confirmed the existence of bioactive molecules in the plants. The magnetic property was analyzed using a vibrating sample magnetometer (VSM), which displayed that the synthesized nanoparticles were superparamagnetic and exhibiting a saturation magnetization of 12.5 emu/g. Synthesized magnetic nanoparticles were used in methylene blue (MB) dye removal through adsorption. About 83% of 100 mg/L MB dye was removed within 120 min at pH 6 with a maximum adsorption capacity of 246.8 mg/g. Antibacterial efficacy of LS-Fe-NPs was screened against G-negative (Escherichia coli) and G-positive bacteria (Staphylococcus aureus), respectively, and found that LS-Fe-NPs were effective against Staphylococcus aureus.

• Journal of the Korean Society of Safety
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• v.39 no.2
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• pp.38-43
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• 2024

Recently, with the expanding market for electronic devices and electric vehicles, secondary battery usage has been on the rise. Lithium-ion batteries are particularly popular due to their fast charging times and lightweight nature compared to other types of batteries. A secondary battery consists of four components: anode, cathode, electrolyte, and separator. Generally, the positive and negative electrode materials of secondary batteries are composed of an active material, a binder, and a conductive material. Acetylene Black (AB) is utilized to enhance conductivity between active material particles or metal dust collectors, preventing the binder from acting as an insulator. However, when recycling waste batteries that have been subject to high usage, there is a risk of fire and explosion accidents, as accurately identifying the characteristics of Acetylene Black dust proves to be challenging. In this study, the lower explosion limit for Acetylene Black dust with an average particle size of 0.042 ㎛ was determined to be 153.64 mg/L using a Hartmann-type dust explosion device. Notably, the dust did not explode at values below 168 mg, rendering the lower explosion limit calculation unfeasible. Analysis of explosion delay times with varying electrode gaps revealed the shortest delay time at 3 mm, with a noticeable increase in delay times for gaps of 4 mm or greater. The findings offer fundamental data for fire and explosion prevention measures in Acetylene Black waste recycling processes via a predictive model for lower explosion limits and ignition delay time.

• Journal of Plant Biotechnology
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• v.6 no.1
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• pp.9-13
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• 2004

Transient uidA expression was used to optimize parameters required for biolistic transformation of suspension cells of Easter lily, Lilium longiflourm. Maximum uidA expression occurred following bombardment with gold particles as compared to tungsten. A 3hr pre-treatment of suspension cells with 0.125M osmoticum resulted in a 1.5X increase in uidA expression. A helium pressure of 1550 psi combined with a particle travelling distance of 6cm resulted in maximum uidA expression as compared to either 1100, 1200, or 1800 psi. Transient transformation resulted in up to 493 uidA expressing cells/Petri plate. For stable transformation suspension cells of Lilium longiflorum, were co-bombarded with plasmid DNA containing cucumber mosaic virus (CMV) replicase under the rice actin (Act1) promoter and either the bar or PAT genes under the cauliflower mosaic virus (CaMV 355) promoter. Ten regenerated plants contained the transgene as analyzed by PCR, and two of the ten plants were confirmed to contain the transgene by Southern hybridization. The two transgenic plants were independent transformants, one containing the bar gene and the other both the CMV replicase and bar genes. Plants were sprayed at the rosette stage and found to be resistant to 1000 mg/L of phosphinothricin (Trade name-Ignite) indicating expression of the bar gene throughout the leaves when bar was under control of the CaMV 35S promoter.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.301-307
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• 2012

SiAlON glasses are silicates or alumino-silicates, containing Mg, Ca, Y or rare earth (RE) ions as modifiers, in which nitrogen atoms substitute for oxygen atoms in the glass network. These glasses are found as intergranular films and at triple point junctions in silicon nitride ceramics and these grain boundary phases affect their fracture behaviour. This paper provides an overview of the preparation of M-SiAlON glasses and outlines the effects of composition on properties. As nitrogen substitutes for oxygen in SiAlON glasses, increases are observed in glass transition temperatures, viscosities, elastic moduli and microhardness. These property changes are compared with known effects of grain boundary glass chemistry in silicon nitride ceramics. Oxide sintering additives provide conditions for liquid phase sintering, reacting with surface silica on the $Si_3N_4$ particles and some of the nitride to form SiAlON liquid phases which on cooling remain as intergranular glasses. Thermal expansion mismatch between the grain boundary glass and the silicon nitride causes residual stresses in the material which can be determined from bulk SiAlON glass properties. The tensile residual stresses in the glass phase increase with increasing Y:Al ratio and this correlates with increasing fracture toughness as a result of easier debonding at the glass/${\beta}-Si_3N_4$ interface.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.43-49
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• 2016

This analyzed a Young's modulus (E), a thermal expansion coefficient (TEC, ${\beta}$) and a thermal conductivity (${\kappa}$) of the material with simple cubic particulate inclusion using two model structures: a parallel structure and a series structure of laminated layers. The derived ${\beta}$ equations were applied to calculate the ${\beta}$ value of the W-MgO system. The accuracy was higher for the series model structure than for the parallel model structure. Young's moduli ($E_c$) of sintered porous alumina compacts were theoretically related to the development of neck growth of grain boundary between sintered two particles and expressed as a function of porosity. The series structure model with cubic pores explained well the increased tendency of $E_c$ with neck growth rather than the parallel structure model. The thermal conductivity of the three phase system of alumina-mullite-pore was calculated by a theoretical equation developed in this research group, and compared with the experimental results. The pores in the sintered composite were treated as one phase. The measured thermal conductivity of the composite with 0.5-25% porosity (open and closed pores) was in accordance with the theoretical prediction based on the parallel structure model.

• Korean Journal of Veterinary Research
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• v.30 no.1
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• pp.85-91
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• 1990

This study was designed in order to investigate the effect of copper sulfate to the ultrastructural changes of the hepatocytes in Sprague Dawley rats. The animals were administered with copper sulfate (10mg/kg B.W.), which was dissolved in normal saline. The solution was injected into abdominal cavity every day. The animals were sacrificed at the 6th, 12th, and 24th day from the beginning of administration. The specimens obtained from the liver were observed with electron microscope and significant changes were as follows. 1. A prominent dilatation and disruption of the cisternae of rough endoplasmic reticulum were recognized. Also, the detachment of membrane bound ribosomes was shown. 2. The proliferation of smooth endoplasmic reticulum and the depletion of glycogen particles were noted. 3. The increase of primary lysosomes and autophagic vacuoles was obserbed. 4. The dilatation of mitochondrial cristae was obserbed. And it was irregulary scattered in the stroma of mitochondria. 5. The atrophy of microvilli in the bile canaliculi and space of Disse was prominent. 6. Membrane of hepatocytes was damaged and significant hydrophic degeneration was obserbed in the perisinusoidal regions. 7. The damage of Fat-storing cells was more significant than that of hepatocytes.