• Elastomers and Composites
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• v.36 no.2
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• pp.102-110
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• 2001

The three types of surfactants such as nonylphenoxy poly(ethylene) ethanol homologues, caster oil poly(ethylene) ethanol homologues, and sodium perfluoroalkyl carboxylates are used to improve the wettability of rubber impression material. Among the surfactants, the usage of sodium perfluoroalkyl carboxylates containing fluoro group resulted in the lowest surface energy of impression material and the result gave the positive effect on the wettability of rubber impression material to teeth. Also, the anti-foaming agents were used to reduce or remove the hydrogen gas generating on the impression material by reaction. In the case of rubber impression material containing sodium perfluoroalkyl carboxylate as a surfactant, it was found that the tear strength of rubber impression material increased over 3 N/mm with the addition of anti-forming agent. Therefore, the anti-foaming agent could contribute to the mechanical property of rubber impression material without the change of surface property.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.48-53
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• 2009

The effect of bloating and fluxing agent on the microstructure and physical properties were studied in manufacturing the artificial lightweight aggregates of bulk density below] using clay and stone sludge. In case of the aggregates added only with bloating agent, the bulk density and water absorption were $0.5{\sim}1.0$ and $41{\sim}110%$ respectively but the microstucture was not uniform with a rough appearance. For the aggregates added with a fluxing agent and one bloating agent, a part of shell was lost due to explosion of specimen caused by over-bloating during a sintering. The mixed addition of bloating agents with vacuum oil, carbon and ${Fe_2}{O_3}$ made the microstructure homogeneous by generating an uniform black core and shell structure. The aggregates added with mixed agents and sintered at $1200^{\circ}C$ showed the bulk density 67 % lower and water absorption 48 times higher than those of the specimen with no additives. ]n this study, the artificial lightweight aggregates showing the bulk density of $0.5{\sim}1.0$ and water absorption of $50{\sim}125%$ could be fabricated to apply to various fields.

• Resources Recycling
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• v.5 no.3
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• pp.44-49
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• 1996

One of the most serious problems in utilizing the fly-ash produced from damcstic coal-firing power plants is lhc unburned-carbon mntained m the fly-ash In this shldy, the effects of fruther and collector an the yield,recuvery,unburnedcarbon rejectiou peiccntage,and process efficiency of product (cleaned fly-ash) wcrc examined when convzntional froth flotation was applied to rejcct the unburned-carbon included in the fly-ash of bituminous coal Alsa,the ash analysis for both thc raw and the clcaned fly-ash was conducted to review the change in thc major elements of fly-ash. Experimental results shawcd lhat tlle rcjectlon oI the unburned-cubon of thc raw fly-ash sample is available upto 92.4% using fiath flotalian and that the putity ol the pmdud(c1eancd fly-ash) attains up to 99.4%.

• Resources Recycling
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• v.9 no.6
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• pp.36-44
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• 2000

Fly ash was composed of the unburned carbon and mineral particles. The former was able to attach on the bubbles, while the latter was not. Therefore, it was possible to separate the unburned carbon and the mineral from fly ash using the froth flotation process. This study was carried out to evaluate the separation efficiency as a function of the ny ash particle properties in the column flotation. Separation efficiency was analyzed for various size fraction of -38 fm,38~125 fm and 1125 W, and for various fly ash samples containing 7, 11, and 20 wt% unburned carbon. For the size fractions of -38 fm containing 7 wt% unburned carbon, separation efficiency was 86ft, whereas separation efficiency was found to be 74% for the size fraction of +125$\mu\textrm{m}$ containing 20 wt% unburned carbon. The results indicated that separation efficiency increased with the decrease in the particle size and the unburned carbon content of the fly ash.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.960-968
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• 2012

In this study, the measurement of physical properties of 3 different ethylene oxide adducted zwitterionic surfactants were measured such as critical micelle concentration, surface tension, interfacial tension, contact angle, viscosity and foam stability. Also, the dual function characteristics of the zwitterionic surfactants were investigated by determining an isoelectric point, which were obtained using zeta potential measurement and QCM (quartz crystal microbalance) experiments. The isoelectric point of the synthesized zwitterionic surfactant determined by zeta potential measurement was close to that obtained by QCM experiment and both results have shown almost the same trend as that determined by the frictional property measured using an automated mildness tester. In particular, it has been observed that all three surfactants used during this study provide better softening effect at a pH of neutral condition than at an acidic or an alkaline condition. This result indicates that the synthesized surfactants act as a cationic surfactant at a pH of neutral condition and thus provide good softening effect during a rinsing cycle in the detergency process.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.301-307
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• 2014

In order to reduce the emission of carbon dioxide($CO_2$), this research use blast furnace slag in concrete manufacture, as 100% replacement of cement. The aim of this study is to investigate the density and strength properties of alkali-activated lightweight composites with alkali activators of different types and different amounts. The bubble for achieving the lightweight of alkali-activated lightweight composites was generated in the reaction between the paper ash and the alkali activators instead of using a foaming agent. Lightweight formed concrete was conducted basic experimental for determining replacement ratio of paper ash. Then, the density and strength were measured according to the types and the contents of the alkali accelerator that can react with the paper ash. As results, the optimum replacement ratio of the paper ash was 5%. The alkali activator containing NaOH 12.5% obtained the lowest weight of $1.13g/cm^3$. Also, compressive strength were relatively high. Therefore, this study demonstrated that alkali accelerator with a certain amount of NaOH can achieve relatively high strength and lightweight alkali-activated lightweight composites.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.255-261
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• 2016

In this study, among various factors having influence on SUV, we intended to compare and analyze the change of SUV using CT(4 type) and MRI(3 type) contrast agents which are commercialized now. We used Discovery 690 PET/CT(GE) and NEMA NU2 - 1994 PET phantom as experimental equipment. We have conducted a study as follows; first, we filled distilled water to phantom about two-thirds and injected radioisotope(18F-FDG 37 MBq), contrast agent. Second, we mixed CT contrast agent with distilled water and MRI contrast agent with that water separately. And then, we stirred the fluid and filled distilled water fully not to make air bubble. In emission scan, we had 15minutes scanning time after 40 minutes mixing contrast agent with distilled water. In transmission scan, we used CT scanning and its measurement conditions were tube voltage 120 kVp, tube current 40 mA, rotation time 0.5 sec, slice thickness 3.27 mm, DFOV 30 cm. Analyzing results, we set up some ROIs in 10th, 15th, 20th, 25th, 30th slice and measured SUVmean, SUVmax. Consequently, all images mixed 3 types of MRI contrast agent with distilled water have high SUVmean as compared with pure FDG image but there was no statistical significance. In SUVmax, they have high score and there was statistical significance. And other 4 images mixed 4 types of CT contrast agent with distilled water have significance in both SUVmean and SUVmax. Attenuation correction in PET/CT has been executed through various methods to make high quality image. But we figured out that using CT and MRI contrast agents before PET/CT scanning could make distortion of image and decrease diagnostic value. In that reason, we have to sort out the priority of examination in hospital not to disturb other examination's results. Through this process, we will be able to give superior medical service to our customers.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.9
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• pp.743-748
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• 2009

Chemical sludge conditioning is widely used to improve the dewatering efficiency. It is treated with commonly used conditioners, and then thickened and dewatered with a mechanical device. This paper aims to examine the flotation and thickening efficiencies of sewage sludge for conditioning conditions, such as unaerobic storage time, kinds of coagulant and dosages, and flotation conditions, such as sludge concentration and A/S ratio, using an dissolved air flotation apparatus. Experimental results showed that the specific surface area and specific resistance to filtration (SRF) were significantly increased and the flotation and thickening efficiencies were decreased with anaerobic storage time. However, the flotation and thickening efficiencies faintly decreased in sewage sludges conditioned as $Al_2(SO_4)_3$, $Fe_2(SO_4)_3$, and PSO-M. Flotation and thickening efficiencies in conditioned sewage sludge could be sustained up to 96% at A/S ratio of 0.01 mL/mg or over.

• Conservation Science in Museum
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• v.28
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• pp.65-88
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• 2022

The characteristics and behavior of bullets are important because they are directly related to the firearm performance. However, research related to bullets have been small. In this paper, scientific analysis was conducted to find out the materials and manufacturing process of metal bullets during the Joseon Dynasty, owned by Korea Army Museum, and the types of firearms available were classified and organized according to the bullet diameter. As a result, bullets were classified into iron bullets, lead bullets, and lead-coated iron bullets. Most of the iron bullets and lead bullets were made from casting. Some iron bullets were made from forging. And the lead-coated iron bullet was made by pouring molten lead after putting the iron bullet into the mold. Finally, the bullets could be used for Hand Cannon, Matchlock Musket, Frankish Cannon, Hyeon-ja Cannon, Dae-Wiwon Cannon, Small Cannon, and Hong-Yi Cannon.

• Elastomers and Composites
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• v.38 no.4
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• pp.316-325
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• 2003

The blends of waste-polyethylene (W-PE)/waste-ethylene vinyl acetate copolymer (W-EVA) with inorganic and phosphorous flame retardants (i.e., aluminium hydroxide, magnesium hydroxide, and so on) were prepared by melt mixing techniques at different compositions and foamed. The flame retardancy and foaming properties of the blends, limiting oxygen index (LOI), heat release rate (HRR), carbon monoxide yield (COY), total heat release (THR), effective heat of combustion (EHC), expandability and cell structure were investigated using cone calorimeter, SEM, LOI tester and polarizing microscope. When the composition ratios of the W-PE/W-EVA blends were 50/50 (w/w), and the ranges of the flame retardants contents were $175{\sim}220 phr$, we could obtain foams with the uniform and closed cell, high expandability (1900 % or more), high LOI, and low HRR values. These results depend on crosslinking and loaming conditions, a char formation and smoke suppressing effect. Aluminium hydroxide had more effect in the increase of LOI than magnesium hydroxide, while magnesium hydroxide considerably affected the decrease of HRR and COY.