• Membrane Journal
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• v.26 no.6
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• pp.421-431
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• 2016

Novel membrane technologies that harness ordered nanostructures have recently received much attention because they allow for high permeability due to their reduced flow resistance while also maintaining high selectivity due to their isoporous characteristics. In particular, the opaline structure (made from the self-assembly of colloidal particles) and its inverted form (inverse-opal) have shown strong potential for membrane applications on account of several advantages in processing and the resulting membrane properties. These include controllability over the pore size and surface functional moieties, which enable a wide range of applications ranging from size-exclusive separation to catalytically-reactive membranes. Furthermore, when combined with multiscale architecturing strategies, inverse-opal-structured membranes can be designed to have specific pores or channel structures. These materials are anticipated to be utilized for next-generation, high-performance, and high-value-added functional membranes. In this review article, various types of inverse-opal-structured membranes are reviewed and their functionalization through hierarchical structuring will be comprehensively investigated and discussed.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.470-475
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• 2012

$La_{1-x}Sr_xMnO_3$(LSM,$0{\leq}x{\leq}0.5$) powders as the air electrode for solid oxide fuel cell were synthesized by a glycine-nitrate combustion process. The powders were then examined by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The as-formed powders were composed of very fine ash particles linked together in chains. X-ray maps of the LSM powders milled for 1.5 h showed that the metallic elements are homogeneously distributed inside each grain and in the different grains. The powder XRD patterns of the LSM with x < 0.3 showed a rhombohedral phase; the phase changes to the cubic phase at higher compositions($x{\geq}0.3$) calcined in air at $1200^{\circ}C$ for 4 h. Also, the SEM micrographs showed that the average grain size decreases as Sr content increases. Composite air electrodes made of 50/50 vol% of the resulting LSM powders and yttria stabilized zirconia(YSZ) powders were prepared by colloidal deposition technique. The electrodes were studied by ac impedance spectroscopy in order to improve the performance of a solid oxide fuel cell(SOFC). Reproducible impedance spectra were confirmed using the improved cell, which consisted of LSM-YSZ/YSZ. The composite electrode of LSM and YSZ was found to yield a lower cathodic resistivity than that of the non-composite one. Also, the addition of YSZ to the $La_{1-x}Sr_xMnO_3$ ($0.1{\leq}x{\leq}0.2$) electrode led to a pronounced, large decrease in the cathodic resistivity of the LSM-YSZ composite electrodes.

• Journal of Aquaculture
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• v.15 no.1
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• pp.7-13
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• 2002

Since 1993, the White Spot Syndrome Virus (WSSV) disease occurred in China among cultured shrimps resulting in mass mortality. Epizootiological surveys undertaken during the outbreak period of 1993-1994 indicated that all stages of Penaeus chinensis, P. japonicus and P. monodon were infected. Consequent to the transport of contaminated shrimp seedlings and seawater, the disease spread all over the farms of China. The disease was more rapidly transmitted at temperatures above $25^{\circ}C$. Challenge experiments showed the causative agent was highly virulent. White spots appeared on the carapace of both span-taneous and experimentally infected shrimps. Moribund shrimps contained turbid hemolymph, hypertrophied Iymphoid organ and a necrotic mid-gut gland. Electron microscopy showed the presence of viral particles in the gills, stomach, lymphoid organ, and epidermal tissue of the infected shrimp. The visions were slightly ovoid with an envelope and averaged 350 $\times$ 150 nm; nucleocapsids measured 375 $\times$ 157 nm. With discontinuous sucrose gradient of 35, 50 and 60% (w/v), the virus was separated from hemolymph of the infected shrimp. The estimated molecular weight of genomic DNA was 237 Kb with EcoR I, 247 Kb with Hind III and 241kb with Pst I. A total of 9 hybridoma colones secreting monoclonal antibodies (MAbs) were produced from mouse myeloma and spleen cells immunized with WSSV. The immunofluorescence assay of gill tissue showed that the MAbs reacted with diseased but not with healthy shrimp. The MAbs belonged to IgGl, IgG2b subclass and IgM class, all with kappa light Immune-electron-microscopy with colloidal gold marker showed the presence of 5 MAbs epitopes on the envelope and one on the capsid of the virus. Baculoviral mid-gut gland necrosis showed the specificity of the MAbs produced. For diagnosis 5 different methods were selected. Using Kimura primers for PCR, or MAbs for immunoblot, ELISA or FAT method, in situ hybridization was carried out to show the gene. All these methods detected WSSV in the organ samples of the diseased shrimp but not in healthy one.

• Journal of the Korean Ceramic Society
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• v.33 no.8
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• pp.915-920
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• 1996

Fine mullite precursor was prepared by colloidal sol-gel processes. Aluminum isopropoxide $[Al(i-OC_3H_7)_3]$ as a starting material of $Al_2O_3$ and silicic acid extracted by THF from sodium silicate as a starting material of $SiO_2$ were used. Sodium silicate was first acidified by dilute sulfuric acid to form silicic acid. ; followed by extraction using THF, Mullite precursor was synthesized by sol-gel processes from aluminum isopropoxide and sillicic acid considering the degree of extraction of Si and the removal efficiency of Na. The impurity content of silicic acid extracted by THF was below 0.04% Synthetic mullite precursor consisted of $3Al_2O_3{\cdot}2SiO_2$ and showd spherical particles of $0.05{\mu}m$ diameter and below 0.462% of impurites. The mullite precursor was characterized by EDS, XRD, TG/DSC SEM, FT-IR spectroscopy ICP and TEM.

• Journal of Environmental Science International
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• v.26 no.5
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• pp.563-572
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• 2017

The Electrocoagulation-Flotation (ECF) process has great potential in wastewater treatment. ECF technology is effective in the removal of colloidal particles, oil-water emulsion, organic pollutants such as microalgae, and heavy metals. Numerous studies have been conducted on ECF; however, many of them used a conventional plate-type aluminum anode. In this study, we determined the effect of changing operational parameters such as power supply time, applied current, NaCl concentration, and pH on the turbidity removal efficiency of kaoline. We also determined the effects of different electrolyte types (NaCl, $MgSO_4$, $CaCl_2$, $Na_2SO_4$, and tap water), as well as the differences caused by using a plate-type and mesh-type aluminum anode, on the turbidity removal efficiency. The results showed that the optimal values of ECF time, applied current, NaCl concentration, and pH were 5 min, 0.35 A, 0.4 g/L NaCl in distilled water, and pH 7, respectively. The results also revealed that the turbidity removal efficiency of kaoline in different electrolytes decreased in the following sequence, given the same conductivity: tap water > $CaCl_2$ > $MgSO_4$ > NaCl > $Na_2SO_4$. The turbidity removal efficiency of the mesh-type aluminum anode was significantly greater than the plate-type aluminum anode.

• Korean Journal of Medicinal Crop Science
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• v.26 no.5
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• pp.417-429
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• 2018

Background: The objective of this study was to make colloidal dispersions of the active compounds of radix of Angelica gigas Nakai that could be charaterized as nano-composites using hot melt extrusion (HME). Food grade hydrophilic polymer matrices were used to disperse these compound in aqueous media. Methods and Results: Extrudate solid formulations (ESFs) mediated by various HPMCs (hydroxypropyl methylcelluloses) and Na-Alg polymers made from ultrafine powder of the radix of Angelica gigas Nakai were developed through a physical crosslink method (HME) using an ionization agent (treatment with acetic acid) and different food grade polymers [HPMCs, such as HP55, CN40H, AN6 and sodium alignate (Na-Alg)]. X-ray powder diffraction (XRD) analysis confirmed the amorphization of crystal compounds in the HP55-mediated extrudate solid formulation (HP55-ESF). Differential scanning calorimetry (DSC) analysis indicated a lower enthalpy (${\Delta}H=10.62J/g$) of glass transition temperature (Tg) in the HP55-ESF than in the other formulations. Infrared fourier transform spectroscopy (FT-IR) revealed that new functional groups were produced in the HP55-ESF. The content of phenolic compounds, flavonoid (including decursin and decursinol angelate) content, and antioxidant activity increased by 5, 10, and 2 times in the HP55-ESF, respectively. The production of water soluble (61.5%) nano-sized (323 nm) particles was achieved in the HP55-ESF. Conclusions: Nano-composites were developed herein utilizing melt-extruded solid dispersion technology, including food grade polymer enhanced nano dispersion (< 500 nm) of active compounds from the radix of Angelica gigas Nakai with enhanced solubility and bioavailability. These nano-composites of the radix of Angelica gigas Nakai can be developed and marketed as products with high therapeutic performance.

• Economic and Environmental Geology
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• v.33 no.3
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• pp.181-193
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• 2000

This study was undertaken to evaluate the drinking water quality based on physicochemical properties and chemical compositions of the supply water in the Daedeok Campus, and to verify the analytical reliabilities of ICP-MS and IC equipped in the Central Research Facilities at Chungnam National University , Korea. The supply water belongs to $Ca^{2+}-({HCO_3}^-+{SO_4}^{2-})$type, whereas the original water from the Daecheong lake belongs to $(Ca^{2+}-(Mg^{2+})-{HCO_3}^-$ type. Generally, temperature (14.1$^{\circ}C$), pH (6.95), Eh (0 mV), electrical conductivity (117${\mu}$S/cm) and TDS (86.975mg/l) of supply water were higher than those of original lake water . Results using WATEQ4F revealed that potentially toxic ions of the supply water might exist mainly as free metals ($M^{2+}$) and a small amount as ${CO_3}^{2-}$ and $OH^-$ complexes. Also, the water composition belongs to the kaolinite field. Calculated average enrichment indies of the supply water normalized to lake water for anions, mamor cations, toxic cations and total ions are 1.05 , 1.56, 13.05 and 1.17 , respectively. Those values of the ground water in the Daedeok Campus showed 1.71, 4.78, 5.71 and 2.49 , respectively. However , contents of all constituents of these water are within the drinking water standard. All samples were filtered before the chemical analysis. Pale yellow or yellowish brown colored materials of colloidal particles coated the filter paper to thickness of 0.02 to 0.2mm. these are mainly Fe-Cy-Zn compounds with traces of Ni and Pb, the net weights of which compounds range from 0.01to 3.20mg/l. Most elements did not show any conceivable filtering effect of Cu, Fe and Zn. Especially, mean concentration of total Fe decreased considerably from 168.52${\mu}g$/lto 42.58${\mu}g$/l by filtering .

• Journal of the Korean institute of surface engineering
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• v.4 no.1
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• pp.5-15
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• 1971

"Rapid Determination of Boric Acid in Nickel Plating Solution" by the addition of Na$_2$C$_2$O$_4$ and thus preventing the precipitation of i(OH)$_2$ during titiration , has previously been reported. In this paper, the exact amount of glycerine and the complexing possibility of oxalate with nickel has been determined by measn of conductivity titrations. This experimental work has been supported by the mathematical application of the Debye-Huckel and mass action equitions as well as statistical analysis. The results were ; (1) Fro determining boric acid in nickel plating solution, 20 ml of 400ml/ι glycerine was sufficient, since 97% of the H$_3$BO$_3$ was dissoicated by this addition. (2) In the absence of Na$_2$C$_2$O$_4$ the continious precipitation of Ni(OH)$_2$ during titration with NaOH even past end -point for boric acid determination resulted in considerable anlaytical error. (3) In the presence of Na$_2$C$_2$O$_4$ during titration , Ni++ combined with C$_2$O$_4$-to form NiC$_2$O$_4$. The solution with this precititate of very fine, colloidal , trantsparent particles, remained quite clear for approximately 2 hours. Therefore it was shown that the presence of Na$_2$C$_2$O$_4$ prevents the formation of gross Ni(OH)$_2$ precititation by forming NiC$_2$O$_4$ instead of a complex salt with Ni++ , which did not interfere with the visible determination of the end point for boric acid with NaOH titation. This observous may be interpreted in the light of the previously published solubility ratio for NiC$_2$O$_4$ and Ni(OH)$_2$, 0.3mg/100g H$_2$O(25$^{\circ}C$), respectively. Precipitation of the less soluble , albeit transparent salt, NiC$_2$O$_4$ precluded therefore the precipitation of the Ni(OH)$_2$ salt.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.78-81
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• 2010

Surface modification of silica nanoparticles was investigated using an aerosol self assembly. Stearic acid was used as surface treating agent. A two-fluid jet nozzle was employed to generate an aerosol of the colloidal suspension, which contained 20 nm of silica nanoparticles, surface modifier, and ethyl alcohol. Powder properties such as morphology, specific surface area and pore size distribution were analyzed by SEM, BET and BJH methods, respectively. Surface properties of the silica power were analyzed by FT-IR. The OH bond of the $SiO_2$ surface was converted to a C-H bond. It was revealed that the hydrophilic surface changed to a hydrophobic one due to the aerosol self assembly. Morphology of the surface treated powder was nanostructured with lots of pores having an average diameter of around $2\;{\mu}m$. Depending on the stearic acid concentration (0.25 to 1.0 wt%), the pore size distribution of the particles and the degree of hydrophobicity ranged from 1.5 nm to 180 nm and 29.6% to 50.2%, respectively.

• Polymer(Korea)
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• v.25 no.2
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• pp.302-310
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• 2001

Cu/PET film composites were prepared by electroless copper plating method. In order to improve adhesion between electroless Cu plated layer and polyester (PET) film, the effect of pretreatment conditions such as etching method and mixed catalyst composition, and accelerator was investigated. Compared to NaOH etching medium, PET film was more finely etched by HCl solution, resulting in an improvement in adhesion between Cu layer and PET film. However, there were no significant differences in electromagnetic interference shielding effectiveness as a function of etching medium. The surface morphology of Cu plated PET film revealed that Pd/Sn colloidal particles became more evenly distributed in the smaller size by increasing the molar ratio of PdCl$_2$ : SnCl$_2$ from 1 : 4 to 1 : 16. With increasing the molar ratio of mixed catalyst, the adhesion and the shielding effectiveness of Cu plated PET film were increased. Furthermore, HCl was turned out to be a better accelerator than NaOH in order to enhance the activity of the mixed PdCl$_2$/SnCl$_2$ catalyst, which facilitated the formation of more uniform copper deposit on the PET film.