• Journal of the Korean Chemical Society
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• v.61 no.1
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• pp.7-11
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• 2017

The extended $H{\ddot{u}}ckel$ method is employed to analyze the interaction of carbon monoxide with the TiC(001) surfaces, both perfect and containing carbon vacancies. CO exhibits a similar ${\sigma}$-donation interaction for both $Ti_{25}C_{25}$ and $Ti_{25}C_{23}$ clusters, as deduced from the fact that the populations of the CO $5{\sigma}$ orbital are identical upon adsorption, but it bonds more strongly with the $Ti_{25}C_{23}$ than with the $Ti_{25}C_{25}$ because the metal d electron density in $Ti_{25}C_{23}$ provides ${\pi}$ back-bonding interactions with CO that are absent in $Ti_{25}C_{25}$. This work suggests that a difference in reactivity toward CO of stoichiometric TiC and TiC with carbon defects is connected with the occupancy of $2{\pi}^*$ orbitals that leads to a significant weakening of the C-O bond.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.128-131
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• 1996

From Raman spectra, the ${\nu}g$C=O frequencies of 4-substituted benzaldehydes were found to correlate with the ${\sigma}_p$ values of the 4-x atom or group as well as the acceptor number (AN) values of solvents. In various solvents, the ${\nu}g$C=O frequency of benzaldehyde decreased upon the increase of benzaldehyde concentration. This shift was mainly due to the hydrogen bonding between the carbonyl oxygen and/or aldehydic proton of benzaldehyde and the solvent molecules. Over the 1-80 volume % change, the ${\nu}g$C=O frequency of benzaldehyde down shifted from 1709.4 $cm^{-1}$ to 1700.2 $cm^{-1}$ in CCl4 solution and from 1703.0 $cm^{-1}$ to 1698.0 $cm^{-1}$ in $C_2H_5OH$ solution. This is due to the fact that hydrogen bonding between the benzaldehyde and C2H5OH was much stronger than that between the benzaldehyde and the other solvents.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.6-13
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• 2022

The electrostatic phenomenon seriously issued in extreme ultraviolet semiconductor cleaning was studied in junction with molecular dynamic aspect. It was understood that two lone pairs of electrons in water molecule were subtly different each other in molecular orbital symmetry, existed as two states of large energy difference, and became basis for water clustering through hydron bonds. It was deduced that when hydrogen bond formed by lone pair of higher energy state was broken, two types of [H₂O]⁺ and [H₂O]^- ions would be instantaneously generated, or that lone pair of higher energy state experiencing reactions such as friction with Teflon surface could cause electrostatic generation. It was specifically observed that, in case of electrolyzed cathode water, negative electrostatic charges by electrons were overlapped with negative oxidation reduction potentials without mutual reaction. Therefore, it seemed that negative electrostatic development could be minimized in cathode water by mutual repulsion of electrons and [OH]^- ions, which would be providing excellences on extreme ultraviolet cleaning and electrostatic control as well.

• Journal of the Korean Geosynthetics Society
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• v.16 no.3
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• pp.41-49
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• 2017

In this study, a series of laboratory and in-situ tests such as FVTs and CPTUs were carried out to evaluate undrained shear strength related to quasi overconsolidated characteristics in the near-surface clay at Busan new port. Using unconfined compression and field vane test results, correlation between undrained shear strength and effective overburden pressure, that is, equation of $10+0.262{\sigma}^{\prime}v_0$ (kPa) was obtained. From oedometer tests, OCR is around 1.9 at depths lower than 7 m and OCR below this depth is very close to unit. As stated by Hanzawa et al. (1983), a natural clay deposit in the near-surface, even in normally consolidated state, is more and less apparently overconsolidated due to aging effects such as chemical bonding. Based on this concept, it can be inferred that intercept of equation is mobilized due to chemical bonding irrespective of effective overburden pressure and strength incremental ratio in normally consolidated state is 0.262. From CPTU results, same trend was confirmed. The further study should be necessary to judge whether upper clay is under overconsolidated state due to chemical bonding or not based on the depositional environment.

• Journal of the Korean Chemical Society
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• v.29 no.2
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• pp.98-103
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• 1985

Orbital interactions between two nonbonding orbitals have been investigated for heteroatom analogues of trimethylene diradical using MINDO/3 and STO-3G methods. The results showed that the conformers in which significant ${\sigma}$-aromatic stabilization is involved exhibited level order reversal to $n_-$ below $n_+$ as it was found for trimethylene diradical. Lone pair orbitals (LPO) were found to be stabilized by charge dispersion accompanying vicinal trans $n-{\sigma}^*$ interaction and hydrogen bonding. In systems with different heteroatoms, N and O, the contribution of the LPO of oxygen, $n_O$ was always greater in the lower level whereas that of nitrogen, nN, was greater in the higher level as can be expressed as : $n_{\pm}$(lower) = $n_O{\pm}{\lambda}_Nn_N.\;n_{\pm}(higher)\;=\;n_N{\pm}{\lambda}_On_O$. where ${\lambda}_i$< 1.0

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1408-1414
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• 2004

The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. ACF (anisotropic conductive film) is one of the major flip-chip technologies, which has short chip-to-chip interconnection length, high productivity, and miniaturization of package. In this study, thermal fatigue lift of ACF bonding flip-chip package has been predicted. Elastic and thermal properties of ACF were measured by using DMA and TMA. Temperature dependent nonlinear hi-thermal analysis was conducted and the result was compared with Moire interferometer experiment. Calculated displacement field was well matched with experimental result. Thermal fatigue analysis was also conducted. The maximum shear strain occurs at the outmost located bump. Shear stress-strain curve was obtained to calculate fatigue life. Fatigue model for electronic adhesives was used to predict thermal fatigue life of ACF bonding flip-chip packaging. DOE (Design of Experiment) technique was used to find important design factors. The results show that PCB CTE (Coefficient of Thermal Expansion) and elastic modulus of ACF material are important material parameters. And as important design parameters, chip width, bump pitch and bump width were chose. 2$^{nd}$ DOE was conducted to obtain RSM equation far the choose 3 design parameter. The coefficient of determination ($R^2$) for the calculated RSM equation is 0.99934. Optimum design is conducted using the RSM equation. MMFD (Modified Method for feasible Direction) algorithm is used to optimum design. The optimum value for chip width, bump pitch and bump width were 7.87mm, 430$\mu$m, and 78$\mu$m, respectively. Approximately, 1400 cycles have been expected under optimum conditions. Reliability analysis was conducted to find out guideline for control range of design parameter. Sigma value was calculated with changing standard deviation of design variable. To acquire 6 sigma level thermal fatigue reliability, the Std. Deviation of design parameter should be controlled within 3% of average value.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2393-2397
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• 2009

Second-order rate constants ($k_{HOO}$‒) have been measured spectrophotometrically for nucleophilic substitution reactions of Y-substituted phenyl benzenesulfonates (1a-g) with $HOO^-$ ion in $H_2O$ at $25.0\;{\pm}\;0.1\;{^{\circ}C}$. The Br$\phi$nsted-type plot is linear with ${\beta}_{lg}$ = ‒0.73. The Hammett plot correlated with with ${\sigma}^-$ constants results in much better linearity than ${\sigma}^o$ constants, indicating that expulsion of the leaving group occurs in the rate-determining step (RDS) either in a stepwise mechanism or in a concerted pathway. However, a stepwise mechanism in which departure of the leaving group occurs in the RDS has been excluded since $HOO^-$ ion is more basic and a poorer leaving group than the leaving Y-substituted phenoxide ions. Thus, the reactions of 1a-g with $HOO^-$ ion have been concluded to proceed through a concerted mechanism. The $\alpha$-nucleophile $HOO^-$ ion is more reactive than its reference nucleophile $OH^-$ ion although the former is ca. 4 p$K_a$ units less basic than the latter (i.e., the $\alpha$-effect). TS stabilization through intramolecular H-bonding interaction has been suggested to be irresponsible for the $\alpha$-effect shown by $HOO^-$ ion, since the magnitude of the $\alpha$-effect is independent of the electronic nature of substituent Y in the leaving group. GS destabilization through desolvation of $HOO^-$ ion has been concluded to be responsible for the $\alpha$-effect found in the this study.

• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.436-441
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• 2001

The emission and excitation spectra of mer-[Cr(dien)(glygly)]ClO$_4$(glygly=glycylglycinate;dien=N-(2-aminoethyl)-1,2-ethanediamine) taken at 77 K are reported. The infrared and visible spectra at 298 K are also measured. The twelve electronic bands due to spin-allowed and spin-forbidden transitions are assigned. Using the observed transitions, a ligand field analysis has been performed to determine the bonding property of coordinated atoms in the chromium(III) complex. It is confirmed that the amine nitrogen atoms of the dien and glygly have strong $\sigma$-donor characters, but the peptide nitrogen of glygly has weak $\pi$-donor property toward chromium(III) ion.

• Journal of the Korean Applied Science and Technology
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• v.7 no.1
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• pp.93-105
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• 1990

Semicarbazone formation of nine monosubstituted benzaldehydes was studied kinetically in 20% methanol buffer solution at 15, 25, 35, and $45^{circ}C$. The rate of p-nitrobenzaldehyde semicarbazone formation is 2.7 times as fast as that of benzaldehyde, while p-hvdroxybenzaldehyde is 3.6 times as slow as that of benzaldehyde. Activation energies for p-chlorobenzaldehyde, benzaldehyde, p-methylbenzaldehyde, p-methoxybenzaldshyde, p-hydroxybenzaldehyde, and p-dimethylaminobenzaldehyde semicarbazone formation are calculated as 5.80, 6.19, 6.57, 7.06, 8.03, and 6.46 kcal/mol respectively. It is concluded from the effect of ionic strength that the reaction is affected by not ions but neutral molecules involving hydrogen bonding between oxygen atom of carbonyl group and hydrogen atom of acid-catalyst, and concerted attack of the necleophilic reagent, free base on carbonyl compound. Also, the effect of solvent composition is small in 20% and 50% methanol (and ethanol) aqueous solutions. The ${\rho}-{\sigma}$ plots for the rates of semicarbazone formation at pH 7.1 show a linear ${\rho}-{\sigma}$ relationship (${\rho}=0.14l$, in contrast to that at pH 2.75 and pH 5.4 corresponding to ${\rho}-{\sigma}$ correlations reparted by Jencks. The rate of semicarbazone formation at pH 5.4 show a relationship which is convex upward, resulting in a break in the curve but at pH 2.75, slight difference from a linear relationship. As a result of studying citric acid catalysis, second-order rate constants increase linearly with citric acid concentration and show a 2 times increase as the catalyst concentration is varied from 0.025 to 0.1 mol/1 at pH 2,9, but slight increase at pH 5.3. The rate-determining step is addition below pH 5 but is dehydration between pH 5 and 7. Conclusively, the rate-determining step of the reaction changes from dehydration to addition in respect to hydrogen ion activity near pH 5. The ortho: para rate ratio of the hydroxybenzaldehydes for semicarbazone formation is about 17 at $15^{\circ}C$. It is concluded that the results constitute strong evidence in favor of greater stabilization of p- than o-hydroxybenzaldehyde by substituent which donate electrons by resonance and is due to hydrogen bonding between the carbon-bound hydrogen of the-CHO group and the oxygen atom of the substituent.

• YAKHAK HOEJI
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• v.33 no.3
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• pp.141-148
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• 1989

The weak UV absorbing antihistaminics such as chlorpheniramine, triprolidine, tripelennamine and diphenhydramine were analyzed by charge-transfer spectrophotometric method. The results obtained are summarized as folows. It was possible to determine a weak UV absorbing antihistaminics using the intense charge-transfer UV bands in chloroform. Charge transfer complexes were formed in a 1:1 ratio between antihistaminics and iodine in chloroform. Linear relationship was found between absorbance and concentration in the range of $1.0\;{\times}\;10^{-5}M-5.0\;{\times}\;10^{-5}M$ for chlorpheniramine( ${\varepsilon}\;=\;2.082\;{\times}\;10^4$) and tripelennamine ( ${\varepsilon}\;=\;1.578\;{\times}\;10^4$), $1.0\;{\times}\;10^{-5}M-8.0\;{\times}\;10^{-5}M$ for triprolidine ( ${\varepsilon}\;=\;1.120\;{\times}\;10^4$) and $1.0\;{\times}\;10^{-5}M-1.0\;{\times}\;10^{-4}M$ for diphenhydramine ( ${\varepsilon}\;=\;9.900\;{\times}\;10^3$). Charge transfer complexes of chlorpheniramine, triprolidine and tripelennamine have absorption maxima at 293 nm and complex form of diphenhydramine has absorption maximum at 270 nm. By UV, IR spectra, it could be inferred that CT-complexes were formed by interaction between the basic nitrogen of antihistaminics as electron donor (non bonding electron) and iodine as electron acceptor (${\sigma}$ bonding electron).