• Asian Journal of Atmospheric Environment
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• v.7 no.4
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• pp.217-226
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• 2013

The collection of TSP and $PM_{2.5}$ aerosols has been made at the Gosan Site of Jeju Island during 2008-2011, and their ionic and elemental species were analyzed, in order to examine the seasonal variation and characteristics of aerosol compositions. The anthropogenic components ($NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$, S, Zn, Pb) and the soil components ($nss-Ca^{2+}$, Al, Fe, Ca) showed high concentrations in spring as the prevailing westerly wind, but the concentrations of the sea-salt components ($Na^+$, $Cl^-$) were high in winter. In TSP, the neutralization by $NH_3$ increased in summer, but the neutralization by $CaCO_3$ increased in spring and fall seasons. The organic acids ($HCOO^-$, $CH_3COO^-$) contributed to the acidification of the aerosols by only 5.0%, so the acidification could be mostly contributed by the inorganic acids ($SO_4{^{2-}}$, $NO_3{^-}$). From the examination of the source origins by factor analysis, the compositions of TSP were influenced by the order of soil > anthropogenic > marine, on the other hand, those of $PM_{2.5}$ were by the order of anthropogenic > marine > soil. The backward trajectory analyses showed that the concentrations of $NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$ and $nss-Ca^{2+}$ increased highly when the air masses had moved from China continent into Gosan area of Jeju Island.

• Journal of Magnetics
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• v.19 no.2
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• pp.111-115
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• 2014

X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) were used to investigate the influence of Ni ions on the structural, electronic, and magnetic properties of nickel-ferrites ($Ni_xFe_{3-x}O_4$). Spinel $Ni_xFe_{3-x}O_4$ ($x{\leq}0.96$) samples were prepared as polycrystalline thin films on $Al_2O_3$ (0001) substrates, using a sol-gel method. XRD patterns of the nickel-ferrites indicate that as the Ni composition increases (x > 0.3), a structural phase transition takes place from cubic to tetragonal lattice. The XPS results imply that the Ni ions in $Ni_xFe_{3-x}O_4$ substitute for the octahedral sites of the spinel lattice, mostly with the ionic valence of +2. The minority-spin d-electrons of the $Ni^{2+}$ ions are mainly distributed below the Fermi level ($E_F$), at around 3 eV; while those of the $Fe^{2+}$ ions are distributed closer to $E_F$ (~1 eV below $E_F$). The magnetic hysteresis curves of the $Ni_xFe_{3-x}O_4$ films measured by VSM show that as x increases, the saturation magnetization ($M_s$) linearly decreases. The decreasing trend is primarily attributable to the decrease in net spin magnetic moment, by the $Ni^{2+}$ ($2{\mu}_B$) substitution for octahedral $Fe^{2+}$ ($4{\mu}_B$) site.

• Fisheries and Aquatic Sciences
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• v.1 no.2
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• pp.201-208
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• 1998

A protease, which had no tryptic and chymotryptic activity, was purified from the hepatopancreas of shrimp, P. japonicus, through ammonium sulfate fractionation, Q­Sepharose ionic exchange, benzamidine Sepharose 6B affinity, and Sephacryl S-100 gel chromatography. Molecular weight (M.W.) of the protease was estimated to be 24 kDa by gel filtration and showed a single peptide band by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). The protease had a low ratio of acidic to basic amino acids, which is different with pro teases from marine animals. The enzyme was partially inhibited by benzamidine, tosyl-L-lysine chioromethyl ketone (TLCK), phenylmethylsulfonyl fluoride (PMSF), soybean trypsin inhibitor (SBTI), and pepstatin. The enzyme did not have any activity against benzoyl-D,L-arginine p-nitroanilide (BAPNA) or benzoyl-L-tyrosine ethyl ester (BTEE) which is a specific substrate of trypsin and chymotrypsin, respectively. However, the enzyme showed activity forward N-CBZ-L-tyrosine p-nitrophenyl ester (CBZ-Tyr-pNE), N­CBZ-L-tryptophan p-nitrophenyl ester (CBZ-Trp-pNE), and N-CBZ-L-proline p-nitrophenyl ester (CBZ-Pro-pNE). The protease did not showed tryptic and chymotryptic activity, which was not reported in shrimp hepatopancreas.

• Clean Technology
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• v.5 no.2
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• pp.37-44
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• 1999

The influence of the reactant composition on the surface free energy and on the dispersity in water was investigated by using the fluorine-containing water-soluble polyurethane synthesized with the fluorine-containing diol and hydrophilic diol. The diol donating ionic characteristics was more effective than polyol, and stable emulsion with the diameter of 610~310 nm was obtained in the range of 0.3~0.7 molar ratio of the diol to polyol. According to the increment of fluorine-containing compound up to 10 wt %, the surface free energy of polyurethane was dramatically decreased from 22.3 to 12.6 dyn/cm, and the diameter of water dispersed polyurethane increased from 380 to 860 nm due to the strong interaction between polymer molecules because fluorine segments are arranged on the surface of molecules. The macromonomer with perfluoroalkyl group was more effective in complement of the weak point of water-soluble polyurethane, which is a decrease of hydrophobicity, because of strong hydrophobicity.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.235-240
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• 2008

This paper presents results and observations obtained from a study of the optical and thermal properties of alkali tellurite depending on the composition. Fourier transform infrared (FT-IR) spectra showed evidence of chemical modification from $TeO_4$ trigonal bipyramids (tbp) to $TeO_3$ trigonal pyramids (tp) in tellurite glasses. The optical band gaps of the different glass samples calculated using Tauc's method were found to range from 3.5-3.8 eV. The glass transition temperature (Tg) and glass stability (${\Delta}T$) of alkali tellurite glasses were investigated, as $M_2O$ [M: Li, Na, K] amounted to 25 mol%, through the use of differential thermal analysis (DTA). The coefficient of thermal expansion (CTE) was measured in a thermo mechanical analysis (TMA) with a slow heating rate after the glass samples were annealed. The results confirm that the optical band gap of alkali tellurite glasses depends on the Te-O-Te structural relaxation related to the ratio of bridging/non bridging oxygen (BO/NBO). In contrast, the thermal properties are related to the ionic field strength of the Te-O-M and M-O-M bonds, and the Te-O-Te breakage depends on the ratio of BO/NBO.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.660-664
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• 2001

$Zn_xSr_{1-x}S$ thin films were prepared in the whole composition range by rf sputtering, using powder targets of a mixture of ZnS and SrS with the required mole fraction. The possibility of existence of $Zn_xSr_{1-x}S$ solid solutions was systematically investigated from the results of thin film growth, in terns of structural, optical characteristics and the chemical bonding of the constituent atoms. The XRD, XPS and optical results made it clear that the solid solutions with a single-phased zincblende structure and a single-phased rocksalt structure were formed at $0.86~0.93{\leq}x{\leq}1$ and $0{\leq}x{\leq}0.29$, respectively. The miscibility gap, including phase separation regions was found to exist in $0.3{\leq}x{\leq}0.86~0.91$, in which lattice constants, binding energy and absorption edges kept almost constant by the same values as those at border compositions. The experimental results on phase transition agreed well with the fraction of ionic character $f_{i}$ based on the Phillips'dielectric theory.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.99-104
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• 1992

The permeability vs. temperature curve, the loss factor and the microstructure of a commercial Mn-Zn ferrites were investigated by X-ray diffractometer, SEM and LCR meter, where the additives, such as $SnO_{2}$ and $GeO_{2}$, were added to the main composition. Their wt% were 0.05, 0.3 and 1.0, respectively. When the content of additives increased, the SPM (Secondary Peak Maximum) of the permeability moved from $80^{\circ}C$ to below the room temperature. This movement, without the significant change of the microstructure, is because Sn and Ge, having the different ionic radius, were soluble in the matrix. There was no variation of the permeability with the frequency up to 100 kHz. And the loss factor showed the maximum value at 10 kHz.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.220-225
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• 2008

Lead-free ferroelectric ceramics are widely researched today for industrial applications as sensors, actuators and transducers. Since $Pb(Zr_aTi_{1-a})O_3$-(PZT) has high Curie temperature($T_C$), high piezoelectric properties near its morphotropic phase boundary(MPB) composition and small temperature dependence electrical behavior, it has been used to commercial materials for wide temperature range and different application fields. According to the tolerance factor concept, since the $Bi^{3+}$ cation with 12-fold coordinate has a smaller ionic radius than 12-fold coordinate $Pb^{2+}$, most bismuth based perovskites possess a smaller tolerance factor. Therefore, MPBs with a higher $T_C$ may be expected in $Bi(Me^{3+})O_3PbTiO_3$ solid solutions. As in lead based perovskite systems, it is clear that we need to explore more materials in simple or complex bismuth based MPB systems. The objective of this study is to investigate the $Bi(Ni_{1_a}X_a)O_3-PbTiO_3(X=Ti^{4+},\;Nb^{5+})$ perovskite solid-solution. For improving the electronic conduction problem, the magnesium and manganese modified system was also studied.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.237-244
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• 1993

The characteristics of composite polymer electrolytes obtained by adding a fine ceramic powder($\gamma-{LiAlO}_{2}$) with a diameter of $1{\mu}$m to a poly(ethylene oxide)/lithium trifluoromethane sulfonate (LiC$F_3$S$O_3$) complex are described in terms of morphological and mechanical behavior. The addition of uniformly dispersed ceramic powder greatly improves the electrical and mechanical properties of solid polymer electrolytes at ambient temperature. For the composite polymer electrolytes under this study, the optimum composition of the $\gamma-{LiAIO}_{2}$ in the composite for maximum ionic conductivity was found to be 20 wt%.

• Environmental Engineering Research
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• v.24 no.1
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• pp.159-172
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• 2019

To investigate the influence of pollution events on the chemical composition and formation processes of aerosol particles, 24-h integrated size-segregated particulate matter (PM) was collected during the fall season at an urban site of Gwangju, Korea and was used to determine the concentrations of mass, water-soluble organic carbon (WSOC) and ionic species. Furthermore, black carbon (BC) concentrations were observed with an aethalometer. The entire sampling period was classified into four periods, i.e., typical, pollution event I, pollution event II, and an Asian dust event. Stable meteorological conditions (e.g., low wind speed, high surface pressure, and high relative humidity) observed during the two pollution events led to accumulation of aerosol particles and increased formation of secondary organic and inorganic aerosol species, thus causing $PM_{2.5}$ increase. Furthermore, these stable conditions resulted in the predominant condensation or droplet mode size distributions of PM, WSOC, $NO_3{^-}$, and $SO{_4}^{2-}$. However, difference in the accumulation mode size distributions of secondary water-soluble species between pollution events I and II could be attributed to the difference in transport pathways of air masses from high-pollution regions and the formation processes for the secondary chemical species. The average absorption ${\AA}ngstr{\ddot{o}}m$ exponent ($AAE_{370-950}$) for 370-950 nm wavelengths > 1.0 indicates that the BC particles from traffic emissions were likely mixed with light absorbing brown carbon (BrC) from biomass burning (BB) emissions. It was found that light absorption by BrC in the near UV range was affected by both secondary organic aerosol and BB emissions. Overall, the pollution events observed during fall at the study site can be due to the synergy of unfavorable meteorological conditions, enhanced secondary formation, local emissions, and long-range transportation of air masses from upwind polluted areas.