• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.60-67
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• 2000

The wavelength of the surface plasmon absorption depends on the dielectric matrix. $TiO_2/SiO_2$ complex oxide films doped with Au nanoclusters were prepared by sol-gel spin-coating method using $Ti(OPr^i)_4$, $Si(OEt)_4$, and $HAuCl_4{\cdot}7H_2O$. The wavelength of the maximum absorption of Au nanoehrsters in the $TiO_2/SiO_2$ thin films was obtained with lineality from 540 nm to 615 nm depending on the molar ratio of $TiO_2$. The particle sizes and structures of these nanoclusters have been identified through a TEM and X-ray diffraction patterns. The dielectric constants of $TiO_2/SiO_2$ thin films were calculated from the experimental results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.233-238
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• 2000

t-$ZrO_2/Al_2O_3$composites having a superior biocompatability and phase stability were prepared by adding 0~4 mol% of $Eu_2O_3$and sintered for 1 h at $1600^{\circ}C$ to evaluate phase stability, chromaticity and mechanical properties of the composites. No tetragonal to monoclinic phase transformation was observed for the composites containing $Eu_2O_3$after heat treatment for 20 h at $180^{\circ}C$ under 3.5 MPa water vapor pressure condition. As $Eu_2O_3$content increased, the color of the composites was changed from a slight white ivory to a light pink. The strength and the fracture toughness of the composites containing $Eu_2O_3$were above 620 MPa and 7.6 MPa.$m^{1/2}$, respectively, when $Eu_2O_3$was added up to 3 mol%.

• Resources Recycling
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• v.11 no.1
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• pp.19-25
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• 2002

For $ZnSO_4$-$Na_2$$SO_4$-$H_2$ $SO_4$-$NaOH-H_2$O system, pH of solutions with different electrolyte concentrations was measured at $25^{\circ}C$ and ionic equilibria were analyzed by using K-value method. Activity of water and activity coefficients of solutes were calculated by Pitzer equation. The equilibrium concentration and activity coefficients of solutes were calculated from initial experimental conditions. At high ionic strength of 4m, the pH values calculated were in good agreement with those measured. In the experimental ranges of ionic strength of solution from 3.5 to 4.3 m, the mean activity coefcient of $ZnSO_4$calculated agreed well with those obtained from literature.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.241-246
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• 2003

Numerical simulations are performed at atmospheric pressure in order to understand the effect of additives on flame speed and the NOx formation in freely propagating $H_{2}/O_{2}/N_{2}$ flames with oxygen enrichments. A chemical kinetic mechanism is developed, which involves 26 gas-phase species and 99 reactions. Under several equivalence ratios and oxygen enrichments, flame speeds are calculated and compared with those obtained from the experiments, the results of which is in good agreement. As hydrogen chloride as additive is added into $H_{2}/O_{2}/N_{2}$ flames with low oxygen enrichments, its chemical effect causes the decrease of flame speed, radical concentration, and the NO production rate. It is found that the chemical effect of additive has much more influence on the reduction of EINO than its physical effect. However, in flames with very high flame temperature the physical effect rather than the chemical effect becomes more important on the reduction of EINO.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.312-317
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• 2019

The objective of this study was to investigate the corrosion behavior of aluminum (AA1100) in a mixed solution of 0 ~ 0.1 g/L Na₂S + 0.3 ~ 3 g/L NaCl + 0 ~ 10 mL/L H₂O₂. Potentiodynamic polarization tests were performed. Effects of solution compositions on corrosion potential, corrosion rate, and pitting potential of aluminum were statistically analyzed with a regression model. Results suggested that localized corrosion susceptibility of aluminum was increased in the solution with increasing concentration of NaCl because the pitting potential was lowered linearly with increasing NaCl concentration. On the contrary, H₂O₂ mitigated the galvanic corrosion of aluminum by increasing the corrosion potential. It also mitigated localized corrosion by increasing the pitting potential of aluminum. Na₂S did not exert a noticeable effect on the corrosion of aluminum. These effects of different chemical species at various concentrations were independent of each other. Synergy or offset effect was not observed.

• Journal of the Korean Magnetic Resonance Society
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• v.14 no.2
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• pp.76-87
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• 2010

The structural phase transition of $Cs_2MnCl_4{\cdot}2H_2O$ single crystals was investigated by determining the $^{133}Cs$ spin-lattice relaxation time $T_1$. The number of resonance lines in the $^{133}Cs$ spectrum changes from seven to one near 375 K, which means that above 375 K the Cs sites are symmetric. Further, the $T_1$ of the $^{133}Cs$ nucleus undergoes a significant change near 375 K, which coincides with the change in the splitting of the $^{133}Cs$ resonance lines. The change in $T_1$ near $T_C$ is related to the loss of $H_2O$, and means that the forms of the octahedra of water molecules surrounding $Cs^+$ are disrupted.

• Korean Journal of Crystallography
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• v.13 no.3_4
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• pp.148-151
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• 2002

The molecular and crystal structure of metalaxyl C/sub15/H/sub21/NO₄, was determined by single crystal x-ray diffraction study. Crystallographic data for, title compound P2₁/c, a=7.849(4) Å, b=13.081(5) Å, c=15.100(3) Å, β=101.8(2)°, V= 1517.6(3) ų, Z=4. The molecular. Structure model was solved by direct method and refined by full-matrix least- squares. The final reliable factor, R, is 0.067 for 1694 independent reflections (F/sub o//sup 2/>4σ(F/sub o//sup 2/)). The molecular structure of title compound shows an intramolecular hydrogen bond: Cl2-Hl2A…O1.

• Journal of the Korean Chemical Society
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• v.13 no.1
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• pp.16-24
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• 1969

Ni, Co, Zn, Cd, Mn, Mg, Ca, Sr, Ba 등의2가 금속과 U(VI) 및 V(IV)의 이온이 만드는 $MCup_2$ 조성의 cupferrates 착화합물에 관하여, 그 용해도가 좋은 dioxane-$H_2O$, methanol-$H_2O$, ethanol-$H_2O$ 및 2-propanol-$H_2O$의 혼합용매를 사용하여, 그들의 몰분율을 변화시키면서 제 1, 제 2 및 전체의 열역학적인 안정도상수를 전위차적정법에 의하여 측정하고, 안정도 상수와 유기용매의 몰분율에 관한 실험식을 얻었다. 한편 분광광전법에 의하여 가능한 cupferrates의 전체 안정도 상수를 측적하여 이들과 비교하였다. 2가 금속 cupferrates의 안정도상수는 위에 적은 금속의 순서로 감소하고, 이들의 log $K_1$은 log $K_2$보다 크지만, U(VI)과 V(IV)의 cupferrates는 log $K_1$$K_2$여서 1:1과 1:2 착화합물 사이에 구조 변화가 있는듯하다. 몰분율이 영인 점에서의 안정도상수는 금속 cupferrates의 수용액에서의 용해반응의 평형상수에 해당하며, 금속의 착화합물의 안정도상수와 용해도와는 무관하고, K<$10^5$인 cupferrates에 관해서는 분광전법을 적용하기 어렵다.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.201-209
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• 1996

Background : Auto-PEEP which develops when expiratory lung emptying is not finished until the beginning of next inspiration is frequently found in patients on mechanical ventilation. Its presence imposes increased risk of barotrauma and hypotension, as well as increased work of breathing (WOB) by adding inspiratory threshold load and/or adversely affecting to inspiratory trigger sensitivity. The aim of this study is to evaluate the relationship of auto-PEEP with WOB and to evaluate the effect of PEEP applied by ventilator (external PEEP) on WOB in patients with auto-PEEP. Method : 15 patients, who required mechanical ventilation for management of acute respiratory failure, were studied. First, the differences in WOB and other indices of respiratory mechanics were examined between 7 patients with auto-PEEP and 8 patients without auto-PEEP. Then, we applied the 3 cm $H_2O$ of external PEEP to patients with auto-PEEP and evaluated its effects on lung mechanics as well as WOB. Indices of respiratory mechanics including tidal volume ($V_T$), repiratory rate, minute ventilation ($V_E$), peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), peak inspiratory pressure (PIP), $T_I/T_{TOT}$, auto-PEEP, dynamic compliance of lung (Cdyn), expiratory airway resistance (RAWe), mean airway resistance (RAWm), $p_{0.1}$, work of breathing performed by patient (WOB), and pressure-time product (PTP) were obtained by CP-100 Pulmonary Monitor (Bicore, USA). The values were expressed as mean $\pm$ SEM (standard error of mean). Results : 1) Comparison of WOB and other indices of respiratory mechanics in patients with and without auto-PEEP : There was significant increase in WOB ($l.71{\pm}0.24$ vs $0.50{\pm}0.19\;J/L$, p=0.007), PTP ($317{\pm}70$ vs $98{\pm}36\;cm$ $H_2O{\cdot}sec/min$, p=0.023), RAWe ($35.6{\pm}5.7$ vs $18.2{\pm}2.3\;cm$ H2O/L/sec, p=0.023), RAWm ($28.8{\pm}2.5$ vs $11.9{\pm}2.0cm$ H2O/L/sec, p=0.001) and $P_{0.1}$ ($6.2{\pm}1.0$ vs 2.9+0.6 cm H2O, p=0.021) in patients with auto-PEEP compared to patients without auto-PEEP. The differences of other indices including $V_T$, PEFR, $V_E$ and $T_I/T_{TOT}$ showed no significance. 2) Effect of 3 cm $H_2O$ external PEEP on respiratory mechanics in patients with auto-PEEP : When 3 cm $H_2O$ of external PEEP was applied, there were significant decrease in WOB ($1.71{\pm}0.24$ vs $1.20{\pm}0.21\;J/L$, p=0.021) and PTP ($317{\pm}70$ vs $231{\pm}55\;cm$ $H_2O{\cdot}sec/min$, p=0.038). RAWm showed a tendency to decrease ($28.8{\pm}2.5$ vs $23.9{\pm}2.1\;cm$ $H_2O$, p=0.051). But PIP was increased with application of 3 cm $H_2O$ of external PEEP ($16{\pm}2$ vs $22{\pm}3\;cm$ $H_2O$, p=0.008). $V_T$, $V_E$, PEFR, $T_I/T_{TOT}$ and Cdyn did not change significantly. Conclusion : The presence of auto-PEEP in mechanically ventilated patients was accompanied with increased WOB performed by patient, and this WOB was decreased by 3 cm $H_2O$ of externally applied PEEP. But, with 3 cm $H_2O$ of external PEEP, increased PIP was noted, implying the importance of close monitoring of the airway pressure during application of external PEEP.

• Journal of Life Science
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• v.13 no.4
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• pp.412-415
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• 2003

The purpose of this present study was to investigate the polymorphism of esterase locus for individual identification and parentage verification in Jeju native horse (JNH). Seventy three random JNH samples were studied by polyacrylamide gel isoelectric focusing(IEF) at pH 3.5 ∼ 6.0. We detected international recognized alleles, F, G, H, I, M, and an silent allele $I^o$. Gene frequencies of allele I showed 0.479 the highest, while allele H and M($I^o$) with relatively low frequencies were 0.027 and 0.014, respectively.