• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.527-530
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• 1998

This paper presents the electrochemistry and molecular orbital (MO) picture of a series of conformationally-restricted thioxantone derivatives. A series of $C_2-substituted$ thioxanthones were examined to probe the electronic influence of the substituent on the electrooxidation and electroreduction sites (i.e., on the electron densities at the 10-and 9-positions), respectively. In the presence of "electrophoric" groups such as C=O and S, characteristic electrochemical reduction and oxidation responses are observed. The electrochemical reaction was diffusion-controlled, because the $I_p/{\upsilon}^{1/2}$ ratio was constant for the anodic and cathodic wave of thioxantone derivatives. These substituent effects are presented in terms of correlations of oxidation (or reduction) potentials with the highest occupied molecular orbital (HOMO), or lowest unoccupied molecular orbital (LUMO) energies, respectively. There is good correlation between energies of the HOMO vs. $E_{pa}^{(+)}$ and energies of the LUMO vs. $E_{pc}^{(-)}$. Frontier Molecular Orbital (FMO) is changed by the functional group of thioxanthones. FMO energy level was offered us the information about the electron transfer direction, and the coefficient of FMO was offered the information about the electron transfer position. Sulfur atom has an important effect on oxidation potential, $E_{pa}^{(+)}$ and the carbonyl carbon has an important effect on reduction potential, $E_{pc}^{(-)}$. Therefore we were appreciated that the contribution of sulfur atom for the $E_{pa}^{(+)}$ and HOMO energies is larger than the contribution of carbonyl group for the $E_{pc}^{(-)}$ and LUMO energies.

• The KIPS Transactions:PartA
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• 제19A권2호
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• pp.73-76
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• 2012

In this paper, we propose an efficient method to extract surface atoms from a protein molecule. Surface atoms are defined as a set of atoms who can contact given probe solvent $P$, where $P$ does not collide with the molecule. The atoms contained in the molecule are represented as a set of spheres with van der Waals radii. The probe solvent also is represented as a sphere. We propose a method to extract the surface atoms by computing the offset surface of the molecule with respect to the radius of $P$. For efficient computation of the offset surface of a molecule, a voxel map is constructed for the offset surfaces of the spheres. Based on GPU (graphic processor unit) acceleration, a data parallel algorithm is used to extract the surface atoms in 42.87 milliseconds for the molecule containing up to 6,412 atoms.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3707-3710
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• 2010

A chromo/fluorogenic $NO_2S_2$-macrocycle L functionalized with nitrobenzofurazan unit as a dual-signaling probe was synthesized and structurally characterized by single crystal X-ray analysis. In a cation-induced color change experiment, L exhibited excellent $Hg^{2+}$ ion selectivity by showing the color change from orange-red to yellow. However, this hypochromic shift by $Hg^{2+}$ was observed for the weaker coordinating anion system such as ${NO_3}^-$ and ${ClO_4}^-$ ions. The observed anion effect is due to the strong coordination of anions inhibits the bond formation between $Hg^{2+}$ and the macrocyclic tert-N atom, which is sensitive to induce the color change. In the fluorometric experiment, L showed chelate-enhanced fluorescence change effect only with $Hg^{2+}$ ion, together with a change from yellow to green emission. The sensing ability for $Hg^{2+}$ with the proposed chemosensor L is due to the stable complexation with 1:1 stoichiometry (metal-to-ligand).

• The Journal of Natural Sciences
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• 제12권1호
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• pp.41-48
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• 2002

Atomic coherences can be induced via atom-light interaction and can exhibit new interesting phenomena. Electromagnetically-induced-absorption (EIA) is one of such phenomena where the absorption of probe beam is increased due to the presence of strong coupling beam. EIA can be observed in multiple-V type atomic systems. This paper present a method to study EIA when the frequencies of probe beam and coupling beam are both near resonant to the same transition line. Time-varying interaction Hamiltonian was introduced and density matrix equations were solved and the amplitude of oscillations was used to calculate the EIA.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.273-276
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• 2008

In this study, microstructure and distribution of alloy elements were investigated in thermo-mechanically processed C-Mn-Si transformation induced plasticity (TRIP) steels. The microstructures of TRIP steels were investigated by using advanced analysis techniques, such as three dimensional atom probe tomography (3D-APT). At first, the microstructure was observed by using TEM. TEM results revealed that microstructure of C-Mn-Si TRIP steel was composed of ferrite, bainte, and retained austenite. 3D-APT was used to characterize atomic-scale partitioning of added elements at the phase interface. In the retained austenite phase, Ti and B were enriched with C. However, there was no fluctuation of Mn and Si concentration across the interface. Through these analysis techniques, the advanced characteristics of constituent microstructure in C-Mn-Si TRIP steels were identified.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.213-216
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• 2009

In this study, three cold-rolled TRIP steels containing different Al content (0.04wt%, 1.0 wt.% and 2.00wt%) were fabricated to understand the complex effects of Al in TRIP steel. The influences of Al on microstructural evolution of cold-rolled TRIP steels have been analyzed by using advanced analysis techniques, such as transmission electron microscope (TEM) and three dimensional atom probe tomography (3D-APT). TEM results revealed that second phases such as bainte and retained austenite decrease with increase of Al content. In addition, 3D-APT was used to characterize atomic-scale distribution of alloying elements at the constituent phases. Through these analysis techniques, the advanced characteristics of constituent microstructure in TRIP steels were identified depending on Al contents in TRIP steels.

• Proceedings of the Polymer Society of Korea Conference
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.343-343
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• 2006

Surface-initiated atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out to produce high-density poly(MPC) brush on silicon wafer. Frictional properties of poly(MPC) was investigated by by sliding a glass ball (${\phi}\;10\;nm$) on the substrates over a distance of 20 mm at a sliding velocity of 90 mm/min under loading of 0.49 N at 298 K. Higher friction coefficients were observed in dry N2 atmosphere and in toluene condition, whereas the friction coefficients decreased to 0.02 in humid air and in water. It is supposed that water-swollen poly(MPC) brush works as a lubricant to moderate the interaction between brush and probe.

• Economic and Environmental Geology
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• 제21권3호
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• pp.287-307
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• 1988

The Cheongju gold-silver mine is located at approximately $36^{\circ}28^{\prime}$north latitude and $127^{\circ}31^{\prime}$ east longitude in the Cheongju City of the Chung cheong bug Do, South Korea. Gold-Silver bearing hydrothermal quartz veins, occur in Cheongju Granit of Jurassic age. K-Ar isotope data for sericite in quartz vein indicate that the Au-Ag mineralization took place in early Cretaceous ($97.5{\pm}2.18$ MA. Park, et ai, 1986). Three stage of mineralization recognized anre, from early to later, (I) Sulide stage: pyrite, arsenopyrite, pyrrhotite (Hpo), sphalerite, chalcopyrite, electrum and quartz (II) Electrum stage: pyrite, sphalerite, galena, chalcopyrite, electrum and quartz. (III) Silver mineral stage: pyrite, marcasite, pyrrhotite (Mpo), sphalerite, galena, electrum, native silver argentite, fluorite, calcite and quartz. In this paper, mode of occurrences and chemical compositions of electum and native silver have been investigated by means of microscope and EPMA. Electron probe microanalysis shows that an individual grain of electrum is almost homogeneous in composition. Silver content of electrum ranges from 44.7-67.1 atom.%. Gold content of native silver ranges below 0.2 atom. %. Vicker's hardness number (VHN) of electrum and native silver ranges $78.2-81.8kg/mm^{2}$ respectively. The filling temperature of fluid inclusions in quartz ranges from $130-280^{\circ}C$. On the basis of arsenpyrite geothemometer, the equilibrium temperature and sulfur fugacity of the pyrite-arsenopyrite-pyrrhotite(Hpo) assemblage is assumed to be in ange from $300-310^{\circ}C$ and $10^{-10}$ to $10^{-11}$ atm. The estimated ore reserviors on Cheongju mine area are calculated to 8000 T/M, averaing 8.6g/t Au, 27.8 g/t Ag, 1.25% Pb, l.65% Zn.

• Journal of the Korean Vacuum Society
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• 제8권1호
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• pp.63-69
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• 1999

The characteristic parameters of high density plasma source (Helical Resonator) have been measured with Langmuir probe to get the plasma density electron temperature, ion current density, etc. Optical emission spectra of Si and SiCl have been analyzed in $Cl_2$$/poly-Si system to elucidate etching mechanism. In this system, the main reaction to remove silicon atoms on the surface is proceeding mostly through chemical reaction, not pure physical reaction. The emission intensity of SiCl (chemical etching product) increases much faster than Si (pure physical etching product) with increasing the concentration of impurities (P). This is due to the electron transfer from substrate to the surface via Si-Cl bond. As a result, Si-Cl bond becomes more ionic and mobile, therefore the Cl-containing etchant forms $SiCl_x$ with surface more easily. Consequently, for the removal of Si atom from poly silicon surface, the chemical etching is more favorable than physical etching with increasing P concentrations.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.161-166
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• 2005

The plasma ion density in AC-PDP has shown to be increased from $5.6{\times}10^{11}cm^{-3}$ to $9.0{\times}10^{11)cm^{-3}$ as the Xe mixture ratio to neon increase from 1 % to 10 %, respectively, at fixed pressure of 400 Torr, by using the micro-Langmuir probe. It is noted that the plasma ion density is density increases as the gas pressure increases in this experiment. The electron temperature decreases from 2.3 to 1.2 eV as the Xe mole fraction increases from 1 % to 10 % at fixed pressure of 400 Torr, which is measured by the micro Langmuir probe and high-speed ICCD camera in this experiment. It is noted that the electron temperature decreases as the gas pressure increases from 150 to 400 Torr in this experiment. It is also observed that the exited Xe atom density and the plasma ion density are in strong correlation sharp between each other in this experiment. It is noted that $5.2{\times}10^{12}cm^{-3}$ in the $1s_5$ metastable state and $1.2{\times}10^{12}cm^{-3}$ in the $1s_4$ resonance state for the PDP cell with gap of 50 um distances under the fixed gas pressure of 400 Torr and Xe content ratio of 10 %.