• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.772-777
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• 1999

$Y_2Ba_1Cu_1O_5(Y211)$ powders were prepared by pyrophoric synthesis method and by solid state reaction method using $Y_2O_3(99.9%)$, $BaCO_3(99.9%)$, and CuO(99.9%) powders in both of these processes. The phase formation and reaction kinetics of $Y_2Ba_1Cu_1O_5$ powders have been studied using X-ray diffraction analysis(XRD) of samples at various heat treatment temperatures and reaction time. The reaction characterization suggested that the phase formation rate is mainly controlled by the particle size of Y211 powders. The activation energy(${\Delta}E_a$) of Y211 phase formation in this pyrophoric synthesis method was found to be 136.42 kJ/mol compared with 149.46 kJ/mol for that of solid state reaction method. These results data showed that the pyrophoric synthesis method is kineticaly more efficient than the solid state reaction method in this $Y_2Ba_1Cu_1O_5$ system.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.165-171
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• 1998

The $Y_1Ba_2Cu_3O_{7-x}$(123) superconductor powders were prepared by pyrophoric synthesis method(PSM) using $Y_2O_3$(99.9%), $BaCO_3$(99.9%), and CuO(99.9%) powders. The phase formation and reaction kinetics of 123 superconductor manufactured with powders prepared in various pHs of pyrophoric synthetic solution have been studied through the experiments at various heat treatment temperatures and times. Inductively coupled plasma(ICP) spectroscopy and scanning electron microscopy(SEM) measurements were performed to examine the composition and morphology of the sample. X-ray diffraction(XRD) analysis was done to determine phase formation and conversion ratio of Y-Ba-Cu-O systems. The 123 powder prepared at pH 7(${\pm}0.3$) yields the best result in terms of purity, homogeneity, and reactivity. The activation energies(${\Delta}E_a$) of 123 phase formation were found to be 191 kJ/mol and 230kJ/mol in solid state reaction method and pyrophoric synthesis method, respectively.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.566-572
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• 2007

Two hybrid catalysts for the direct synthesis of DME were prepared and the catalytic activity of these catalysts were investigated. The hybrid catalyst for the direct synthesis of DME was composed as the catalytic active components of methanol synthesis and dehydration. The methanol synthesis catalyst was formed from the precursor contained Cu and Zn, the methanol dehydration catalyst was used ${\gamma}-Al_2O_3$. As PM-CZ+D and CP-CZA/D, Two hybrid catalysts were prepared by physical mixing method (PM-CZ+D) and precipitation method (CP-CZA/D), respectively. PM-CZ+D was prepared by physically mixing methanol synthesis catalyst and methanol dehydration catalyst, CP-CZA/D was prepared by depositing Cu-Zn or Cu-Zn-Al components on ${\gamma}-Al_2O_3$. The crystallinity and the surface morphology of synthesized catalyst were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) to investigate the physical property of prepared catalyst. And BET surface area by $N_2$ adsorption and the surface area of Cu by $N_2O$ chemisorption were investigated about the hybrid catalysts. In addition, catalytic activity of these hybrid catalysts was examined with varying reaction conditions. At that time, the reaction temperature of $250{\sim}290^{\circ}C$, the reaction pressure of 50~70 atm, the $[H_2]/[CO]$ mole ratio of 0.5~2.0 and the space velocity of $1,500{\sim}6,000h^{-1}$ were investigated the catalytic activity. From these results, it was confirmed that the reactivity of CP-CZA/D was higher than that of PM-CZ+D. When the conditions of reaction temperature, pressure, $[H_2]/[CO]$ ratio and space velocity were $260^{\circ}C$, 50 atm and 1.0, $3,000h^{-1}$ respectively, CO conversion using CP-CZA/D hybrid catalyst was 72% and the CO conversion of CP-CZA/D was more than 20% compared with the CO conversion of PM-CZ+D. It was known that Cu surface area of CP-CZA/D hybrid catalyst was higher than that of hybrid PM-CZ+D catalyst using $N_2O$ chemisorption. It was assumed that the catalytic activity was improved because Cu particle of hybrid catalyst prepared by precipitation method was well dispersed.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.774-780
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• 2019

An efficient Pd-coated $La_{0.1}Sr_{0.9}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF-1928) catalyst for total oxidation of methane under landfill gas at low tmeperature has been developed. Synergism was observed between Pd coating and LSCF-1928 substrate. When Pd coating on LSCF-1928, we used electroless plating method and conformed characteristic of catalyst through TPR(Temperature Programmed Reduction) analysis, XRD(X-ray Diffraction) analysis, SEM(Scanning Electron Microscope). The results demonstrated that the Pd coated LSCF-1928 catalysts showed higher performance than non-Pd LSCF-1928. Pd coated LSCF-1928 had low total oxidation temperature of methane (< $475^{\circ}C$) which is lower than total oxidation temperature of methane about non-Pd LSCF-1928 catalysts (= $475^{\circ}C$). Also, $O_2$ conversion rate was higher than non-Pd LSCF-1928 at same temperature.

• The Korean Society of Law and Medicine
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• v.22 no.2
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• pp.3-48
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• 2021

Among the major rulings handed down in 2020, there were cases involving anaphylaxis, which is timely as a side effect of coronavirus and flu vaccine. And as a rare case, a ruling was handed down that if medical treatment was done so unfaithfully beyond the limit of patience of ordinary people, it can be an independent illegal act and a cause of compensation for emotional distress. Also, there was a ruling in the appellate court that evaluated disability rate applying the Korean Academy of Medical Sciences Guides for the Evaluation of Permanent Impairment, not McBride system. And the supreme court made it clear that telemedicine is illegitimate. In relation to duty of explanation, it is in the process of adding detail criterion on the firm principles in the individual cases. In regard of medical records, there was a case that even when a medical record is strongly suspected to be tampered with, it is not considered to be an obstruction of proof. There were cases that resulted in different conclusion between the court of first instance and the appellate court rulings. Lastly, in the face of a growing number of cases in which doctors are sentenced to prison for malpractice, we reviewed a ruling that sentenced a doctor to prison.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.509-516
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• 1994

Liquid phase hydrogenation come into use for the removal process of unsaturated hydrocarbon such as croton aldehyde. The croton aldehyde is generated in a very small amount as by-product in the ethanol production, and it is converted into n-butanol through hydrogenation. Liquid phase hydrogenation is low energy consumption process as compared with gas phase hydrogenation. The nickel catalyst is selected with respect to the economic aspect such as durability and cost. The analysis of the conversion were performed by method of the PMT(permangante time) test. The PMT was sharply decreased as the initial concentrations of croton aldehyde in the ethanol solution were increased. The hydrogenation of croton aldehyde to n-butanol was carried out in sequence after the saturation of the carbon-carbon double bond. The formation of both butyraldehyde and n-butanol followed zero order kinetics. Within expermental conditions the PMT gets longer as reaction temperature goes higer and as LHSV becomes slower, while the reaction pressure has almost no relation with PMT.

• The Journal of the Acoustical Society of Korea
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• v.21 no.4
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• pp.401-406
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• 2002

Each Korean digit is composed of only a syllable, so recognizers as well as Korean often have difficulty in recognizing it. When digit strings are pronounced, the original pronunciation of each digit is largely changed due to the co-articulation effect. In addition to these problems, the distortion caused by various channels and noises degrades the recognition performance of Korean connected digit string. This paper dealt with some techniques to improve recognition performance of it, which include defining a set of PLUs by considering phonemic variations in Korean digit and constructing a recognizer to handle speakers various speaking styles. In the speaker-independent connected digit recognition experiments using telephone speech, the proposed techniques with 1-Gaussian/state gave string accuracy of 83.2%, i. e., 7.2% error rate reduction relative to baseline system. With 11-Gaussians/state, we achieved the highest string accuracy of 91.8%, i. e., 4.7% error rate reduction.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.9
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• pp.1321-1327
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• 2011

The microorganism producing an invertase (E.C. 3.2.1.26) was isolated from wine and tentatively identified as Saccharomyces cerevisiae by cellular fatty acid analysis. The invertase was purified to homogeneity by ammonium sulfate precipitant, dialysis, ion-exchange chromatography on DEAE-Sephadex A-50, and gel chromatography on Sephadex G-200 from the culture supernatant of Saccharomyces cerevisiae JS59. The specific activity and the purification fold of the purified invertase were 7620.9 unit/mg protein and 13.9, respectively. The molecular weight of the purified invertase was estimated to be 38.5 kDa by SDS-PAGE. The optimum pH and temperature for the invertase activity were pH 5 and $55^{\circ}C$, respectively. The invertase activity was relatively stable at pH 4~6 and temperature $55^{\circ}C$. The activity of invertase was inhibited by $Ag^{2+}$ and $Hg^{2+}$, but on the contrary, activated by $Co^{2+}$ and $Mn^{2+}$. Michaelis constant ($K_m$) for invertase reaction in sucrose solution was 11.5 mM. TLC analysis of the products produced in sucrose solution during invertase reaction showed the progressive presence of glucose and fructose in accordance with sucrose hydrolysis.

• Sleep Medicine and Psychophysiology
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• v.12 no.1
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• pp.58-63
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• 2005

Objectives: REM sleep behavior disorder (RBD), characterized by excessive motor activity during REM sleep, is associated with loss of muscle atonia. In recent years, it has been reported that RBD has high co-morbidity with CNS disorders (especially, Parkinson's disease, dementia, multiple system atrophy, etc.). We aimed to assess differences in clinical and polysomnographic findings among RBD patients, depending on the presence or absence of central nervous system (CNS) disorders. Methods: The medical records and polysomnographic data of 81 patients who had been diagnosed as having RBD were reviewed. The patients were classified into two groups: associated RBD (aRBD, i.e., with a clinical history and/or brain MRI evidence of CNS disorder) and idiopathic RBD (iRBD, i.e., without a clinical history and/or brain MRI evidence of CNS disorder) groups. Twenty-one patients (25.9%) belonged to the aRBD group and 60 patients (74.1%) belonged to the iRBD group. The clinical characteristics and polysomnographic findings of the two groups were compared. Results: Periodic limb movement disorder (PLMD), i.e., PLMI (periodic limb movement index)>5, was observed more frequently in the aRBD group than in the iRBD group (p<0.001, Fisher's exact test). Also, obstructive sleep apnea syndrome (OSAS), i.e., RDI (respiratory disturbance index)>5, was found more frequently in the aRBD group (p=0.0042, Fisher's exact test). The percentages for slow wave sleep and sleep efficiency were significantly lower in the aRBD group than in the iRBD group. Conclusion: We found that 1 out of 4 RBD patients had associated CNS disorders, warranting more careful neurological evaluation and follow-up in this category of RBD. In this category of RBD patients, we also found more frequent PLMD and OSAS. These patients were also found to have lower slow wave sleep and sleep efficiency. In summary, RBD patients with associated CNS disorders suffer from more disturbed sleep than those without them.