• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.289-292
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• 2004

A trisaccharide, GlcNAcp- ${\beta}-(1{\to}3)-Galp-{\alpha}-(1{\to}2)$-6-deoxy-altroHepp- ${\alpha}-(1{\to}O$-propyl, as an O-antigenic repeating unit of C. jejuni serotype O:23 and O:36 was synthesized. Coupling of the GlcNPhth-(1${\to}$3)-Gal disaccharide donor with allyl 6-deoxy-altroHep acceptor in the presence of iodonium dicollidine perchlorate (IDCP) promoter afforded the ${\alpha}$-galactosidic trisaccharide with high stereoselectivities. Subsequent deacetalation, dephthaloylation, N-acetylation, and hydrogenolytic debenzylation furnished the title compound.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1396-1400
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• 1994

Electrical properties in the ZnO-Bi2O3-CoO-Zn7Sb2O12 system were investigated with Zn7Sb2O12 content (0.1~2 mol%). The increase of the Zn7Sb2O12 content inhibited the grain growth of ZnO, which showed a narrow grain size distribution of ZnO. The breakdown voltage (Vb) increased markedly with 1 mol% Zn7Sb2O12 addition due to the grain growth control behaviour of the Zn7Sb2O12 . The nonlinear I-V characteristic was significantly influenced by the Zn7Sb2O12 content (or Bi2O3/Zn7Sb2O12 ratio). Addition of 0.5 mol% Zn7Sb2O12 showed the highest nonlinear coefficient ($\alpha$) of 43. The leakage current in prebreakdown region was decreased with increasing Zn7Sb2O12 content.

• Bulletin of the Korean Mathematical Society
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• v.52 no.2
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• pp.661-677
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• 2015

In this paper, we consider the following Kirchhoff-type Schr$\ddot{o}$dinger system $$\{-\(a_1+b_1{\int}_{\mathbb{R^3}}{\mid}{\nabla}u{\mid}^2dx\){\Delta}u+{\gamma}V(x)u=\frac{2{\alpha}}{{\alpha}+{\beta}}{\mid}u{\mid}^{\alpha-2}u{\mid}v{\mid}^{\beta}\;in\;\mathbb{R}^3,\\-\(a_2+b_2{\int}_{\mathbb{R^3}}{\mid}{\nabla}v{\mid}^2dx\){\Delta}v+{\gamma}W(x)v=\frac{2{\beta}}{{\alpha}+{\beta}}{\mid}u{\mid}^{\alpha}{\mid}v{\mid}^{\beta-2}v\;in\;\mathbb{R}^3,\\u,v{\in}H^1(\mathbb{R}^3),$$ where $a_i$ and $b_i$ are positive constants for i = 1, 2, ${\gamma}$ > 0 is a parameter, V (x) and W(x) are nonnegative continuous potential functions. By applying the Nehari manifold method and the concentration-compactness principle, we obtain the existence and concentration of ground state solutions when the parameter ${\gamma}$ is sufficiently large.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1196-1202
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• 2018

$Li_2Sr_{1-x}Eu_xSiO_{4-{\alpha}}N_{\alpha}$ ($Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$) phosphors were synthesized by using a solid state reaction (SSR) method with submicron $Si_3N_4$ and nano $Si_3N_4$ powders as the sources of Si and N, and the optical properties of those phosphors were studied. The studied phosphors showed efficient excitation characteristics over the broad range from 230 to 530 nm. Also, They showed broad emission spectra covering a range from 500 to 700 nm, with a peak at 568 nm, which was shifted longer wavelength by 18 nm as compared with that of commercial $YAG:Ce^{3+}$. Combined with a 450 nm blue LED chip, the results support the application of the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$ phosphor as a luminescent material for a white-light source thaat is warmer than the commercial $YAG:Ce^{3+}$ white-light source. In addition, the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$ phosphors prepared from a submicron $Si_3N_4$ powder was found to emit a previously unreported self-activated luminescence in $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.263-269
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• 1987

It is investigated that the determination of the correlation between the change of microstructure and electrical properties. Yttria is added to the compositiojn of rhombohedral region in Pb(Mg1/3Nb2./3)O3-PbTiO3-PbZrO3 ternary system. Average grian size, lattice parameters and distribution of yttrium are characterized by XRD, SEM and EDS. Electrical properties are determined by measurement of Curie temperature, piezoelectric properties and hysteresis loops. The results are as follows; 1. Both lattice parameters, a and ${\alpha}$, are changed by addition of yttria to the composition of rhomboheadral region in Pb(Mg1/3Nb2./3)O3-PbTiO3-PbZrO3 ternary system and Curie temperature is proportional to the values at (90-${\alpha}$).

• Journal of Magnetics
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• v.15 no.1
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• pp.21-24
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• 2010

A new synthetic method for the formation of uniform $\alpha-Fe_2O_3$ nanoparticles was reported and their magnetic properties were investigated. The sonochemical synthesis and the subsequent take-off technique resulted in spherical shaped $\alpha-Fe_2O_3$ nanoparticles with an average diameter of 60 nm. The temperature- and applied magnetic field-dependent magnetization of the $\alpha-Fe_2O_3$ nanoparticles was explained by the sum of two contributions, i.e., the Morin transition and superparamagnetism, because the critical size for superparamagnetism was within the size variation of the nanoparticles.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.257-260
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• 1987

The asymmetric reduction of representative prochiral ${\alpha},{\beta}$-acetylenic ketones with a new chiral borohydride reducing agent, potassium 9-0-(1,2: 5,6-Di-O-isopropylidene-${\alpha}$ -D-glucofuranosyl)-9-boratabicyclo[3.3.1]nonane, 1, in THF at $-78^{\circ}C$ was studied. Structurally different acetylenic ketones such as internal ${\alpha},{\beta}$-acetylenic ketones $RC {\equiv} CCOCH_3$ and terminal ${\alpha},{\beta}$-acetylenic ketones $HC {\equiv} CCOR$ were chosen. Thus, the reduction of internal ${\alpha},{\beta}$-acetylenic ketones yields the corresponding propargyl alcohols, such as 67% ee for 3-hexyn-2-one, 75% ee for 5-methyl-3-hexyn-2-one, 86% ee for 5,5-dimethyl-3-hexyn-2-one, 74% ee for 3-nonyn-2-one and 61% ee for 4-phenyl-3-butyn-2-one. Terminal ${\alpha},{\beta}$-acetylenic ketones, such as 3-butyn-2-one, 1-pentyn-3-one, 4-methyl-1-pentyn-3-one and 1-octyn-3-one, are reduced to the corresponding alcohols with 59% ee, 17% ee, 44% ee and 12% ee of optical induction respectively. With one exception (4-methyl-1-pentyn-3-one), all propargyl alcohols obtained are enriched in R-enantiomers.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.842-848
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• 2003

Semiconducting $\alpha$-Fe$_2$O$_3$ film was prepared by the cathodic electrodeposition method on Indium Tin Oxide (ITO) substrate for photoelectrochemical cell application. After heat treatment at 50$0^{\circ}C$, the phase was changed from Fe to $\alpha$-Fe$_2$O$_3$. The phase, morphology, absorbance, and photocurrent density (A/$\textrm{cm}^2$) of the film depended on the preparation conditions: deposition time, applied voltage, and the duration of heat treatment. The $\alpha$-Fe$_2$O$_3$ film was characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM), and UV -Visible Spectrophotometer. The stability of the $\alpha$-Fe$_2$O$_3$ film in aqueous solution was tested at zero bias potential under the white-light source of 100 mW/$\textrm{cm}^2$. The apparent grain size of the films formed at -2.0 V was larger than that grown at -2.5 V. The $\alpha$-Fe$_2$O$_3$ film deposited at -2.0 V for 180 s and heat-treated at 50$0^{\circ}C$ for 1 h showed the predominant photocurrent of 834$\mu$A/$\textrm{cm}^2$.

• Applied Biological Chemistry
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• v.37 no.2
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• pp.124-129
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• 1994

The rate of hydrolysis of insecticidal $O,O-diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothioate\;(Volaton^{\circledR})$ has been studied in 25% (v/v) aqueous dioxane. On the basis of solvent effect (pH 6.0; m=0.21, n=1.55, pH 12.0; m=0.42, n=3.14 & $|m|{\ll}|l|$), general base catalysis, hydrolysis product analysis, calculation of molecular orbital (MO) and rate equation, it may be concluded that the hydrolysis of Volaton proceeds through the $A_{AC}2$ mechanism via trigonal bipyramidal $(sp^3d^2)$ intermediate below pH 7.0, while above pH 9.0 the hydrolysis proceeds through the $B_{AC}2$ mechanism. Hydrolysis reactivity of Volaton depends on positive charge strength $(p{\gg}{\alpha}C_2)$ rather than steric hindrance. In the range between pH 7.0 and pH 9.0, these two reactions occur competitively.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.341-346
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• 1986

The electrical conductivity of the system ${\alpha}-Fe_2O_3-CoO$ was measured in the temperature range 200-1000$^{\circ}C$ and PO$_{2}$ range 10$^{-7}-2{\times}10^{-1}$ atm. Possible defect models were suggested on the basis of conductivity data, which were measured as a function of temperature and of oxygen partial pressure. The observed activation energies were 0.50 eV and 1.01 eV in the low- and high-temperature regions, respectively. The observed conductivity dependences on PO$_{2}$ were ${\sigma}\;{\alpha}\;PO_2^{-1/6}$ in the PO$_{2}$ range $10^{-7}-10^{-4}$ atm and ${\sigma}\;{\alpha}\;PO_2^{-1/4}$ at PO$_{2}$ 's of $10^{-4}-2{\times}10^{-1}$ atm at temperatures from 300-1000$^{\circ}C$. An extrinsic electron conduction due to an Vo defect and an intrinsic electron conduction due to an Fei' defect were suggested at different temperature and oxygen partial pressure regions, respectively.