• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.233-239
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• 1991

$N_1-alkyl-5-fluorouracil$ derivatives from 2-chloro-ethylacrylate(CEA) were synthesized. The reaction of 5-fluorouracil(5-FU) with 2-chloroethyl acrylate gave 1-hydroxyethyl-5-fluorouracil(HEFU) in 70% yield. The treatment of HEFU with acryloyl chloride afforded 1-acryloyloxyethyl-5-fluorouracil (AOEFU). Poly(1-acryloyloxyethyl-5-fluorouracil)[Poly(AOEFU)] was also synthesized from 5-fluorouracil and Poly(CEA). The hydrolysis rates of $N_1-alkyl-5-fluorouracil$ derivatives were observed by means of UV spectrophotometer at 265 nm in ethanol-water(1 : 1); k = the constant of hydrolysis rate, $k=1.38{\times}10^{-4}$/sec for HEFU, $k=9.25{\times}10^{-5}$/sec for AOEFU, $k=4.16{\times}10^{-5}$k = 4.16 ${\times}$ $10-5}sec$ for Poly(AOEFU). The differential thermal analysis and thermogravimetry of 5-fluorouracil derivatives have been discussed.

• Polymer(Korea)
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• v.39 no.2
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• pp.346-352
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• 2015

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in the terms of physical and chemical characteristics such as low pour point, high viscosity index (VI), and thermal and oxidation stability. Several kinds of PAOs have been synthesized by using 1-pentene, 1-hexene, 1-octene, or 1-dodecene as monomer with three kinds of aluminum-based Lewis acid catalysts via cationic polymerization. The control of the catalytic performance and physical properties of PAO such like molecular weight, kinematic viscosity, pour point, and viscosity index was done by changing polymerization parameters. The alkyl aluminum halide-based catalysts show better catalytic activity than that of the conventional $AlCl_3$ catalyst. The microstructure of PAO was investigated by means of TOF-MS (time of flightmass spectroscopy) analysis in order to elucidate the correlation between the performances of the lubricant (VI, pour point) and the molecular structure of PAO. The VI of PAO increases with increases in the carbon number of ${\alpha}$-olefin. In other words, the performances of PAO as a lubricant strongly depended on the branch length of PAO.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.387-392
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• 2005

For the production of further functional bio-degradable plastic(polybutylene succinate:PBS) with $TiO_{2}$ as photocatalyst, which shows the decomposition of detrimental organic compound and pollutant under ultraviolet irradiation, we attempted to prepare $TiO_{2}$ coatings on PBS substrate by HVOF and plasma spraying techniques under various conditions. The microstructures of coatings were characterized with SEM and XRD analysis, and the photocatalytic efficiency of coatings was evaluated through the photo degradation of gaseous acetaldehyde. The effects of primary particle size and spraying parameters on the formation behavior, photo catalytic performance and mechanical characteristics of the coatings have been investigated. The results indicated that with respect to both the HVOF sprayed $P_{200}$ and $P_{30}$ coatings, the high anatase ratio off 100% can be achieved regardless of fuel gas pressure. On the other hand, the HVOF sprayed $P_{7}$ coating exhibited largely decreased anatase ratio (from 100% to 49.1%) with increasing the fuel gas pressure, which may be attributed to the much higher susceptibility to heat of 7nm agglomerated powder. In terms of photocatalytic efficiency, HVOF sprayed $P_{200}$ and $P_{30}$ coatings seem to predominate as compared to that of plasma sprayed $P_{200}$ coatings owing to the higher anatase ratio. However, the HVOF sprayed $P_{7}$ coatings didn't show the photo catalytic activity, which may result from the extremely small reaction surface area to the photo-catalytic activity and low anatase ratio. Such functional PBS with new roles is expected to cosiderably contribute to the reduction of aggravated environmel problem.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1203-1210
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• 2006

The filmwise condensation heat transfer coefficients of R-134a on the horizontal copper and stainless steel tubes were measured and analyzed. The outside diameter of the tubes was 15.88 mm, and the tube thickness ranged from 0.89 to 1.65 mm. The polished stainless steel tube had an RMS surface roughness($R_q$) of 0.37 $\mu$m, and commercial stainless steel tubes had an surface roughness($R_q$) of 1.855 $\mu$m. The tests were conducted at the saturation temperatures of 20 and $30^{\circ}C$, and the liquid wall subcoolings from 0.4 to $2.1^{\circ}C$. The measured condensation heat transfer coefficients were significantly lower than the predicted data by the Nusselt analysis. This trend in the stainless steel tube was explained by the effects of thermal resistance of tube material and surface roughness. Based on the experimental data with respect to wall thickness and surface roughness, it was suggested that the existing correlation on external condensation should be modified by considering material and surface roughness factors. The revised correlation was developed by introducing the effects of wall thickness and surface roughness into the Nusselt equation. The average deviation of the revised correlation was 13.0 %.

• The Journal of the Korea Contents Association
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• v.12 no.11
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• pp.482-491
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• 2012

Because the satellite imagery can detect the radiative heat from the surface using the thermal IR (TIR) channel, there have been many efforts to verify the relationship between the land surface temperature (LST) and urban heat island. However, the relationship between geomorphological characteristics like surface aspects and LST is relatively less studied. Therefore, the geomorphological elements, for example, surface aspects and surface slopes, are considered to evaluate their effects on the change of the surface temperature distribution using the Landsat 7 ETM+ TIR channel and the possibility of the image to detect anthropogenic heat from the surface. We found that the surface aspect is ignorable but the surface slope with the sun elevation influences on the surface temperature distribution. Also, the radiative heat from the surface to the atmosphere could not be accurately recorded by the satellite image due to the surface slope but the slope correction process used in this study could correct the surface temperature under slope condition and the slope correction, in fact, was not influenced on the average temperature of the surface. The possibility of the anthropogenic heat detection from the surface from the satellite imagery was verified as well.

• Journal of Powder Materials
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• v.18 no.5
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• pp.437-442
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• 2011

The present study focused on the synthesis of Bi-Te-Se-based powder by an oxide-reduction process, and analysis of the thermoelectric properties of the synthesized powder. The phase structure, chemical composition, and morphology of the synthesized powder were analyzed by XRD, EPMA and SEM. The synthesized powder was sintered by spark plasma sintering. The thermoelectric properties of the sintered body were evaluated by measuring its Seebeck coefficient, electrical resistivity, and thermal conductivity. $Bi_2Te_{2.7}Se_{0.3}$ powder was synthesized from a mixture of $Bi_2O_3$, $TeO_2$, and $SeO_2$ powders by mechanical milling, calcination, and reduction. The sintered body of the synthesized powder exhibited n-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depend on the reduction temperature. The Seebeck coefficient and electrical resistivity of the sintered body were increased with increasing reduction temperature. The sintered body of the $Bi_2Te_{2.7}Se_{0.3}$ powder synthesized at $360^{\circ}C$ showed about 0.5 of the figure of merit (ZT) at room temperature.

• Journal of Powder Materials
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• v.27 no.3
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• pp.226-232
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• 2020

Bismuth vanadate (BiVO₄) is considered a potentially attractive candidate for the visible-light-driven photodegradation of organic pollutants. In an effort to enhance their photocatalytic activities, BiVO₄ nanofibers with controlled microstructures, grain sizes, and crystallinities are successfully prepared by electrospinning followed by a precisely controlled heat treatment. The structural features, morphologies, and photo-absorption performances of the asprepared samples are systematically investigated and can be readily controlled by varying the calcination temperature. From the physicochemical analysis results of the synthesized nanofiber, it is found that the nanofiber calcines at a lower temperature, shows a smaller crystallite size, and lower crystallinity. The photocatalytic degradation of rhodamine-B (RhB) reveals that the photocatalytic activity of the BiVO₄ nanofibers can be improved by a thermal treatment at a relatively low temperature because of the optimization of the conflicting characteristics, crystallinity, crystallite size, and microstructure. The photocatalytic activity of the nanofiber calcined at 350℃ for the degradation of RhB under visible-light irradiation exhibits a greater photocatalytic activity than the nanofibers synthesized at 400℃ and 450℃.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.114-120
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• 2014

The purpose of this study is to conduct the study of the combustion and thermal characteristics through transportation oil for the analysis of fire hazard. Transportation oil breaks down into fuels such as diesel for civilian demands, gasoline, DF1(diesel for military), high sulfur diesel(for marine), kerosene and JP1(for aviation), and lubricants like brake fluid, power steering oil, engine oil, and automatic and manual transmission oil. The experiments of flash point, ignition point, flame duration time, heat release rate were carried out using TAG closed cup flash point tester(AFP761), Cleveland open cup auto flash point analyzer(AFP762), KRS-RG-9000 and Dual cone calorimeter. As a result, the fuel's ignition points were lower than lubricants, especially that of gasoline was not conducted as it has below zero one. Gasoline has the highest ignition point of about $600^{\circ}C$, while the other fuels showed $400{\sim}465^{\circ}C$. For flame duration time, lubricants had over 300 seconds, but fuels had less than 300 seconds except high sulfur diesel(350 seconds). Total heat release rate ranged $287{\sim}462kW/m^2$ for lubricants and gasoline showed the highest total heat release rate, $652kW/m^2$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.8
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• pp.32-39
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• 2010

Hydrogen is sustainable energy without environment pollution. In this study, experiments and analysis of hydrogen generation from gases methanol and ethanol using cylindrical barrier discharge reactor was carried out. The discharge reactor to generate hydrogen molecules used in this work is one type of Non-thermal Plasma (NTP) reactors and neon-transformer as power source to make a plasma was used. Hydrogen concentrations were measured as parameters of applied voltage, concentrations of methanol and ethanol, and flow rates of carrier gases($N_2$). Hydrogen generation increased according to applied voltage and produced largely in case of methanol compared with ethanol. It is thought that the reason is deeply related with those different chemical structures. Energy yield of hydrogen generation in case of ethanol decreases according to increasing applied voltage, but that in case of methanol has a peak at applied voltage of 22[kV] and decreased. Specifically, hydrogen generation increased with increasing applied voltage, but low voltage was better, which is the best parameter in the aspects of energy efficiency.

• Elastomers and Composites
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• v.42 no.3
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• pp.151-158
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• 2007

MWNTs have been widely investigated due to unique properties of such as good electrical conductivity and thermal stability in polymer composites industries. This paper established the procedure to fabricate PMMA/MWNT composites by a modular intermeshing co-rotating twin screw extruder with L/D ratio of 42. The electrical properties of PMMA/MWNT composites with different content of MWNT have been investigated. A sheet resistance percolation was observed at 4 wt% of MWNT for the melt processed composites. Sheet resistance of PMMA/MWNT composite film containing 4 wt% of MWNT was nearby $10^4{\Omega}/sq$ and this shows the possibility of potential application to EMI (Electronic Magnetic Interference) shielding materials. The characteristics of composites were analyzed by TGA, DSC, and SEM. In addition, MFI (Melt Flow Index) has been measured to analyze the rheological property.