• 대한화학회지
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• 제36권5호
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• pp.652-660
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• 1992

폴리아민 리간드인 diethylenetriamine(dien), triethylenetetramine(trien), tetraethylenepentamine(tetren), 및 pentaethylenehexamine(penten)을 Chloromethylated Polystyrene $({\circledP}-) 수지에 반응시켜 각기 {\circledP}_L-Dien, {\circledP}_L-Trien, {\circledP}_L-Tetren 및 {\circledP}_L-Penten 수지를 합성한 후 Bjerrum법으로 pH를 측정하여 산해리상수 및 금속과의 안정도상수를 결정하였으며, Van't Hoff 식에 의해 {\Delta}H와 {\Delta}G도 구하였다. 이들 수지의 안정도상수(log k1)는 금속이온의 종류에 따라 Cu(Ⅱ) > Ni(Ⅱ) > Cd(Ⅱ) > Zn(Ⅱ) > Co(Ⅱ)의 순으로 감소하였으며, 수지중 주게 원자인 질소수가 증가함에 따라 {\circledP}_L-Dien < {\circledP}_L-Trien < {\circledP}_L-Tetren < {\circledP}_L-Penten의 순으로 증가하였다. 그리고 pH 변화에 대한 금속이온의 흡착량 및 분리도를 시험해 본 결과 이들 금속이온과의 안정도 상수값의 순서와 일치하였다.

• 대한기계학회논문집A
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• 제33권3호
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• pp.210-217
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• 2009

This paper presents the analytical prediction of stability lobes in milling. The stability lobes are obtained by measuring the frequency response function (FRF) of a machining center at the cutting point of the end mill cutter, identifying cutting constants, and approximating cutting force coefficients. The stability lobes are experimentally verified through cutting tests.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제20권3호
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• pp.223-232
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• 2013

Alexseev's formula generalizes the variation of constants formula and permits the study of a nonlinear perturbation of a system with certain stability properties. In recent years M. Pinto introduced the notion of $h$-stability. S.K. Choi et al. investigated $h$-stability for the nonlinear differential systems using the notion of $t_{\infty}$-similarity. Applying these two notions, we study bounds for solutions of the perturbed differential systems.

• 대한화학회지
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• 제54권5호
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• pp.541-550
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• 2010

새로운 일곱 자리 질소-산소($N_4O_3$)계 리간드 N,N'-Bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol(H-BAP 4HCl)를 합성하였다. H-BAP 4HCl의 페놀 수산기의 para위치에 브롬, 염소, 메톡 시기 및 메틸기를 가진 Br-BAP 4HCl, Cl-BAP 4HCl, $CH_3O$-BAP 4HCl 및 $CH_3$-BAP 4HCl 염산염을 합성 하였다. 각 리간드의 화학구조는 C, H, N 원소분석법, $^1H$-NMR 및 $^{13}C$-NMR 분광법, 적외선 분광법 및 질량분석법을 통하여 확인하였다. 합성된 $N_4O_3$계 리간드의 전위차 적정 법을 이용하여 계산된 양성자 단계 해리상수는 여섯 단계의 해리상수(${\logK_n}^H$)값을 나타내었고, 각 리간드의 양성자 총괄 해리상수($log{\beta}_p$) 값은 Br-BAP < Cl-BAP < H-BAP < $CH_3O$-BAP < $CH_3$-BAP의 순서로 para Hammett 치환기상수($\sigma_p$) 값의 순서와 역순으로 잘 일치하였다. 각 리간드들과 전이금속(II) 이온들의 착물 안정도상수($logK_{ML}$) 값의 크기순서는 Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II)로 나타났다. 이때 각 리간드들과 전이금속(II) 이온들의 착물 안정도상수 값은 리간드의 총괄 해리상수 값의 크기순서와 같은 경향을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제26권3호
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• pp.393-398
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• 2005

The stability constants for the diaza-18-crown-6 ethers 2-6 and alkali metal cations ($Na^+,\;K^+,\;Rb^+\;and\;Cs^+$) were determined using potentiometry in 95% methanol. For each metal ion the stability constants of the partiallyfluorinated ligands 3-6 were larger than that of the non-fluorinated ligand 2, which might reflect an interaction between fluorine atoms and alkali metal cations. The stability constant of the ligand 4 was larger than that of the ligand 5 for each metal cation tested. This finding was also supported by the results of cation-induced chemical shifts in $^1H-,\;^{19}F$-NMR and extraction experiment. The potentiometry and NMR results as well as the X-ray crystal structures revealed that the position and number of fluorine atoms in the benzyl side arms was crucial for the enhanced interaction between a ligand and an alkali metal.

• Bulletin of the Korean Chemical Society
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• 제21권7호
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• pp.685-689
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• 2000

The complexation reaction between Pb2+,TI and Cd2+ions and macrocyclic ligands, 18-crown-6 ( 18C6) and dibenzo- 18-crown-6 (DB 18C6), was studied in dimethylsulfoxide (DMSO)-nitromethane (NM) and dimethyl-formamide (DMF)-nitromethane binary system s by square wave polarography (SWP) technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the Iigand concentration. In most cases, the stability constants of complexes increase with increasing amounts of the nitromethane in mixed binary solvents used in this study. The complexes formed between 18C6 and DB18C6 and these metal cations in all cases had a stoichiometry of 1 : 1. The results obtained show that there is an inverse relationship between the formation constant of complexes and the donor number of solvents based on a Gatmann donocity scale and the stability constants show a high sensitivity to the composition of the mixed solvent systems. A linear behavior was observed for variation of log Kf of I8C6 complexes vs the composition of the mixed solvent systems in NM/DMSO and NM/DMF,but a non-linear behavior was observed in the case of DB 18C6 complexes in these binary systems. In most of the systems investigated, the Pb2+ cation forms a more stable complex with the 18C6 than other two cations and the order of selectivity of this Iigand for cations is: Pb2+ > TI+,Cd2+.

• BMB Reports
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• 제36권4호
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• pp.367-372
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• 2003

The stability of four hemoglobins (Hb) in dimer forms (low concentration) were investigated by the kinetics of denaturation. The rate constants of denaturation were obtained by variation of 280 nm absorption versus time in 10 mM Tris-HCl, 10 mM EDTA, pH 8.0 at $45^{\circ}C$ in the absence and presence of 0.5 M ethanol, dimethyl sulfoxide (DMSO), formamide, and glycerol. The results show the trend of rate constants in different co-solvents in the following order: chicken hemolysate < human hemolysate and chicken Hb D < chicken Hb A. The buried surface area was calculated for Hb samples in the absence of cosolvents. Accordingly, the trend points out that: chicken Hb D > chicken Hb A > human Hb A. These results suggest that both chicken hemolysate and chicken Hb D are relatively more stable than human and chicken Hb A, respectively. However, the denaturation rate constants of Hb in different co-solvents have designated the following order: ethanol > DMSO > formamide > glycerol. As a matter of fact, this phenomenon is an indication of an increase in the denaturation capacity (DC) and hydrophobicity, and a decrease in the surface tension of the solution in the preceding co-solvents.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.819-822
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• 2004

Protonation constants of calix[4]-cyclen-benzo-crown-6, L in 1X$10^{-2}$ M $Bu_4NCF_3SO_3$ in 40% $CH_2Cl_2/CH_3OH$ at $25^{\circ}C$ determined by potentiometric titration are log $K_1$ = 10.91, log $K_2$ = 10.30, log $K_3$ = 6.24 and log $K_4$ = 2.55. Stability constants for the receptor L complexes with Cu(II) and Zn(II) in 1X$10^{-2}$ M $Bu_4NCF_3SO_3$ in 40% $CH_2Cl_2/CH_3OH$ at $25^{\circ}C$ were determined by UV-VIS spectrometric titration. Stability constants of the CuL and ZnL complexes as log $\beta$ are 4.37 and 3.45, respectively. Stabilization energies for protonations of receptor L, derived from ab initio Hartree-Fock method with 6-31G basis set, are ${\Delta}E_1$ = -290.1, ${\Delta}E_2$ = -205.0, ${\Delta}E_3$ = -124.9 and ${\Delta}E_4$ = -26.9 kcal/mol and complexation energy of ZnL complex is -370.3 kcal/mol.

• Bulletin of the Korean Chemical Society
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• 제15권7호
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• pp.581-584
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• 1994

A comparative investigation of the complexations of divalent metal ions (Cd, Cu, and Pb) by a well characterized soil humic acid (HA) from Okchun Metamorphic Belt was carried out in 0.05 M $KNO_3$ and pH of 4.5 using ion selective electrodes. A continuous distribution model based on the Scatchard Plot was used to determine the stability constants, because the constants obtained by this modeling technique takes the variations in binding energies into consideration without regards to the manner in which M(II) ion is bound on HA. The mean value of log $K_i$ were $4.05{\pm}0.60,\;4.92{\pm}0.36,\;and\;5.63{\pm}0.34\;{\ell}\;mol^{-1}$ for Cd(II)-, Pb(II), and Cu(II)-humate complexes respectively. The values of intrinsic constant (log $K_{int}$; binding at strongest site) were $7.12{\pm}0.30,\;6.59{\pm}0.32,\;and5.07{\pm}0.56\;{\ell}\; mol^{-1}$ in the order Cu(II) > Pb(II) > Cd(II) ion.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.653-656
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• 1997

The new unsymmetric $N_6$ ligand 1-amino-13-(2-pyridyl)-3,6,9,12-tetraazatridecane (aptatd) containing one pyridyl group has been synthesized and characterized by EA, IR, and NMR. Its proton association constants $(log K_H^n)$ and stability constants $(log K_{ML})$ for Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) ions were determined at 298.1 K and ionic strength 0.100 mol $dm^{-3}$ (KNO₃) in aqueous solution by potentiometry: log $K_H^1$=8.80, log $K_H^2$=8.49, log $K_H^3$=6.84, log $K_H^4$=4.17, log $K_H^5$=3.47; log $K_{ML}(Co^{2+})$=18.00, log $K_{ML}(Ni^{2+})$=21.31, log $K_{ML}(Cu^{2+})$=23.62, log $K_{ML}(Zn^{2+})$=15.60. The X-ray structure of its nickel(Ⅱ) complex [Ni(aptatd)]$(ClO_4)_2$ are reported: orthorhombic space group Pbca, a=15.715(1) Å, b=14.280(2) Å, c=19.443(2) Å, V=4363.4 (9) ų with Z=8. The geometry around nickel is a distorted octahedron with the pyridine nitrogen atom being cis to the nitrogen atom of the terminal primary amine.