• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.66-70
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• 1995

The soil humic acid was subdivided into four subfractions by molecular weight (F1: >100.000 dalton; F2: >100.000 dalton; F3: >10.000 dalton; F4: >2.000 dalton) using MP-dual hollow fiber ultrafiltration system. The characterization using IR, 1H and 13C NMR spectroscopy, showed similar spectroscopic features of HA, demonstrating that the bulk properties of HA subfractions are very similar to one another. IR spectral data showed a decrease in polysaccharide contents and increase in carboxylate functionality as molecular weight become smaller.functions. The structure of (NO) can be described by two interactions (N${\cdot}{\cdot}{\cdot}$N, N${\cdot}{\cdot}{\cdot}$O). One is the ONNO structure with an (N${\cdot}{\cdot}{\cdot}$N) interaction. In this structure, acyclic cis-ONNO with $C_{2v}$-symmetry, acyclic trans-ONNO with $C_{2h}$, and cyclic ONNO with trapezoidal structure ($C_{2v}$) are optimized at the MP2 level. The other structure is the ONON structure with an (N${\cdot}{\cdot}{\cdot}$O) interaction. In the structure, acyclic cis-ONON with Cs$^{-symmetry}$ and cyclic ONON of the rectangular ($C_{2h}$), square $(D_{2h})$, rhombic $(D_{2h})$, and parallelogramic $(D_{2h})$ geometries are also optimized. It is found that acyclic cis-ONNO $(^1A_1$) is the most stable structure and cyclic ONNO ($^3A_1$) is the least stable. Acyclic trans-ONNO ($^3A_1$) with an (N${\cdot}{\cdot}{\cdot}$N) interaction, acyclic trans-ONON and bicyclic ONON $(C_{2v})$ with (N${\cdot}{\cdot}{\cdot}$O) interaction, and acyclic cis- and trans-NOON with an (O${\cdot}{\cdot}{\cdot}$O) interaction can not be optimized at the MP2 level. Particularly, acyclic trans-ONNO with $C_{2h}$-symmetry can not be optimized at the CCSD(T) level. Meanwhile, acyclic NNOO ($^1A_1$, $C_s)$ and trianglic NNOO ($^1A_1$,$C_{2v})$ formed by the (O${\cdot}{\cdot}{\cdot}$N) interaction between $O_2$and $N_2$are optimized at the MP2 level. The binding energies and the relative energy gaps among the isomers are found to be relatively small./sec. Spiral CT scans during the arterial phase were obtained 35 seconds after the injection of contrast medium. CT findings of 78 lesions less than 4cm in diameter were correlated with angiographic findings. Results : The attenuation of lesions was high(n = 69), iso(n = 5), and low(n = 4) compared with liver parenchyma during the arterial phase of spiral CT. In lesions with high-, iso-, and low-attenuation during the arterial phase of spiral CT, hypervascularity on angiograms was found in 63 of 69(91.3%), three of five(60%), and three of four lesions(75%), respectively. Six lesions with high-attenuation on the arterial phase of spiral CT were not seen on angiography. Two iso-attenuated and one low-attenuated lesion were hypovascular on angiograms. Conclusion : The results of this study suggest that with some exceptions there was good correlation between the arterial phase of spiral CT and angiography.

• Smart Structures and Systems
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• v.25 no.2
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• pp.135-153
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• 2020

There has been a sustained interest towards the non-contact structural displacement measurement by means of videogrammetric technique. On the way forward, one of the major concerns is the spurious image drift induced by temperature variation. This study therefore carries out an investigation into the temperature effect of videogrammetric technique, focusing on the exploration of the mechanism behind the temperature effect and the elimination of the temperature-caused measurement error. 2D videogrammetric measurement tests under monotonic or cyclic temperature variation are first performed. Features of measurement error and the casual relationship between temperature variation and measurement error are then studied. The variation of the temperature of digital camera is identified as the main cause of measurement error. An excellent linear relationship between them is revealed. After that, camera parameters are extracted from the mapping between world coordinates and pixels coordinates of the calibration targets. The coordinates of principle point and focal lengths show variations well correlated with temperature variation. The measurement error is thought to be an outcome mainly attributed to the variation of the coordinates of principle point. An approach for eliminating temperature-caused measurement error is finally proposed. Correlation models between camera parameters and temperature are formulated. Thereby, camera parameters under different temperature conditions can be predicted and the camera projective matrix can be updated accordingly. By reconstructing the world coordinates with the updated camera projective matrix, the temperature-caused measurement error is eliminated. A satisfactory performance has been achieved by the proposed approach in eliminating the temperature-caused measurement error.

• Advances in concrete construction
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• v.2 no.2
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• pp.109-123
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• 2014

This paper presents chloride induced corrosion durability of reinforcing steel in geopolymer concretes containing different contents of sodium silicate ($Na_2SiO_3$) and molarities of NaOH solutions. Seven series of mixes are considered in this study. The first series is ordinary Portland cement (OPC) concrete and is considered as the control mix. The rest six series are geopolymer concretes containing 14 and 16 molar NaOH and $Na_2SiO_3$ to NaOH ratios of 2.5, 3.0 and 3.5. In each series three lollypop specimens of 100 mm in diameter and 200 mm in length, each having one 12 mm diameter steel bar are considered for chloride induced corrosion study. The specimens are subjected to cyclic wetting and drying regime for two months. In wet cycle the specimens are immersed in water containing 3.5% (by wt.) NaCl salt for 4 days, while in dry cycle the specimens are placed in open air for three days. The corrosion activity is monitored by measuring the copper/copper sulphate ($Cu/CuSO_4$) half-cell potential according to ASTM C-876. The chloride penetration depth and sorptivity of all seven concretes are also measured. Results show that the geopolymer concretes exhibited better corrosion resistance than OPC concrete. The higher the amount of $Na_2SiO_3$ and higher the concentration of NaOH solutions the better the corrosion resistance of geopolymer concrete is. Similar behaviour is also observed in sorptivity and chloride penetration depth measurements. Generally, the geopolymer concretes exhibited lower sorptivity and chloride penetration depth than that of OPC concrete. Correlation between the sorptivity and the chloride penetration of geopolymer concretes is established. Correlations are also established between 28 days compressive strength and sorptivity and between 28 days compressive strength and chloride penetration of geopolymer concretes.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1749-1753
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the nucleophilic substitution reaction of Y-substituted-phenyl picolinates (7a-f) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOK] curves upward while the plot of $k_{obsd}/[EtO^-]_{eq}$ vs. $[EtO^-]_{eq}$ is linear with a positive intercept in all cases. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOK}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ ion and ion-paired EtOK, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The ${\sigma}^{\circ}$ constants result in a much better Hammett correlation than ${\sigma}^-$ constants, indicating that the reaction proceeds through a stepwise mechanism in which departure of the leaving group occurs after the rate-determining step (RDS). $K^+$ ion catalyzes the reaction by increasing the electrophilicity of the reaction center through formation of a cyclic transition state (TS). The catalytic effect decreases as the substituent Y becomes a stronger electron-withdrawing group (EWG). Development of a positive charge on the N atom of the picolinyl moiety through resonance interactions is responsible for the decreasing $K^+$ ion catalysis.

• Journal of the Korean Chemical Society
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• v.40 no.10
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• pp.649-655
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• 1996

The chemical behaviour of Pt(Ⅱ) and Pd(Ⅱ) complexes with the organic ligand tetramethylenesulfoxide(TMSO) has been investigated by UV/vis-spectrophotometric, magnetic, and electrochemical methods. Two energy absorption bands are observed in the spectra of these complexes. The crystal field splitting energy, spin pairing energy, and bond strength were obtained from the spectra of the complexes. The electronic properties of the complexes are found to be delocalized, and low-spin state. The correlation between ligand and metals were strong bonding strength. These complexes are diamagnetics. The redox reaction processes of the complexes were investigated by cyclic voltammetry in an aprotic solvent. The redox processes of complexes turned out to be respect to one-electrton one step. These complexes were considerably diffusion and reaction controlled.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4185-4190
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• 2011

The nucleophilic substitution reactions of ethylene phosphorochloridate (1c) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $5.0^{\circ}C$. The anilinolysis rate of 1c involving a cyclic five-membered ring is four thousand times faster than its acyclic counterpart (1a: diethyl chlorophosphate) because of great positive value of the entropy of activation of 1c (${\Delta}S^{\neq}=+30\;cal\;mol^{-1}K^{-1}$ compared to negative value of 1a (${\Delta}S^{\neq}=-45\;cal\;mol^{-1}K^{-1}$) over considerably unfavorable enthalpy of activation of 1c (${\Delta}H^{\neq}=27.7\;kcal\;mol^{-1}$) compared to 1a (${\Delta}H^{\neq}=8.3\;kcal\;mol^{-1}$). Great enthalpy and positive entropy of activation are ascribed to sterically congested transition state (TS) and solvent structure breaking in the TS. The free energy correlations exhibit biphasic concave upwards for substituent X variations in the X-anilines with a break point at X = 3-Me. The deuterium kinetic isotope effects are secondary inverse ($k_H/k_D$ < 1) with the strongly basic anilines and primary normal ($k_H/k_D$ > 1) with the weakly basic anilines and rationalized by the TS variation from a dominant backside attack to a dominant frontside attack, respectively. A concerted $S_N2$ mechanism is proposed and the primary normal deuterium kinetic isotope effects are substantiated by a hydrogen bonded, four-center-type TS.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2271-2276
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• 2014

Second-order rate constants ($k_N$) have been measured spectrophotometrically for the reaction of 4-chloro-2-nitrophenyl X-substituted-benzoates (6a-6h) with a series of primary amines including hydrazine in 80 mol % $H_2O$/20 mol % DMSO at $25.0^{\circ}C$. The Br${\o}$nsted-type plot for the reaction of 4-chloro-2-nitrophenyl benzoate (6d) is linear with ${\beta}_{nuc}$ = 0.74 when hydrazine is excluded from the correlation. Such a linear Br${\o}$nsted-type plot is typical for reactions reported previously to proceed through a stepwise mechanism in which expulsion of the leaving group occurs in the rate-determining step (RDS). The Hammett plots for the reactions of 6a-6h with hydrazine and glycylglycine are nonlinear. In contrast, the Yukawa-Tsuno plots exhibit excellent linear correlations with ${\rho}_X$ = 1.29-1.45 and r = 0.53-0.56, indicating that the nonlinear Hammett plots are not due to a change in RDS but are caused by resonance stabilization of the substrates possessing an electron-donating group (EDG). Hydrazine is ca. 47-93 times more reactive than similarly basic glycylglycine toward 6a-6h (e.g., the ${\alpha}$-effect). The ${\alpha}$-effect increases as the substituent X in the benzoyl moiety becomes a stronger electron-withdrawing group (EWG), indicating that destabilization of the ground state (GS) of hydrazine through the repulsion between the nonbonding electron pairs on the two N atoms is not solely responsible for the substituent-dependent ${\alpha}$-effect. Stabilization of transition state (TS) through five-membered cyclic TSs, which would increase the electrophilicity of the reaction center or the nucleofugality of the leaving group, contributes to the ${\alpha}$-effect observed in this study.

• Journal of the Korean GEO-environmental Society
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• v.14 no.2
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• pp.51-55
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• 2013

Among various construction methods, deep soil stabilization by chemical method have been widely used in order to improve soft ground. Dynamic variables using ground(such as sand, weathered granite soil and rock) -structure interaction design affected by dynamic load and cyclic load were studied a lot. However, there is something yet to learn about earthquake resistant design regarding reinforced ground by grout. Therefore, in this study using RC test, the correlation between shear strain and shear modulus with change of water content and injection rate in normal portland cement and clay was compared and analyzed by using Ramberg-Osgood model normalization As the result, dynamic coefficient was considerably affected by water content and grout injection rate.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.2
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• pp.174-183
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• 2017

The background level and timely variation characteristics of atmospheric $^{222}Rn$ concentrations have been evaluated by the real time monitoring at Gosan site of Jeju Island, Korea, during 2008~2015. The average concentration of atmospheric radon was $2,480mBq\;m^{-3}$ for the study period. The cyclic seasonality of radon was characterized such as winter maximum and summer minimum, consistent with the reduction in terrestrial fetch going to summer. On monthly variations of radon, the mean concentration in October was the highest as $3,041mBq\;m^{-3}$, almost twice as that in July ($1,481mBq\;m^{-3}$). The diurnal radon concentrations increased throughout the nighttime approaching to the maximum ($2,819mBq\;m^{-3}$) at around 7 a.m., and then gradually decreased throughout the daytime by the minimum ($2,069mBq\;m^{-3}$) at around 3 p.m. The diurnal radon cycle in winter showed comparatively small amplitude due to little variability in atmospheric mixing depth, conversely, large amplitude was observed in summer due to relatively a big change in atmospheric mixing depth. The cluster back-trajectories of air masses showed that the high radon events occurred by the predominant continental fetch over through Asia continent, and the radon concentrations from China continent were about 1.9 times higher on the whole than those from the North Pacific Ocean. The concentrations of $PM_{10}$ also increased in proportion to the high radon concentrations, showing a good linear correlation between $PM_{10}$ and radon concentrations.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.44-50
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• 1992

The ability to account for magnetic and spectra properties of complexes was investigated for the splitting of the degenerate d-orbitals and with nonaqueous solution by UV/vis-spectrophotometric method. The correlation of the magnetitude of 10Dq obtained from the spectra, the pairing energy, and the spin state of the complexes. The electrochemical behavior of complexes were investigated by the use of cyclic voltammetry in aprotic media. These reduction peak of $[(C_6H_5)3_P]_2Pd(II)(CH_3COO)_2$ and $[(C_6H_5)_3Pd]_2Pd(II)Cl_2$ were irreversible one-electron processes at peak $E_{pc1} = -1.32 V,\;E_{pc2} = -1.56 V$ and $E_{pc1} = -1.74 V,\;E_{pc2} = -1.88 V$ of these complexes vs. Ag/AgCl, but nickel complexes were not to be reducible.