• Corrosion Science and Technology
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• v.9 no.5
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• pp.216-222
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• 2010

Most of the thirteen substations in operation in the metropolitan area were installed around the year 2000, and since water cooling methods are used to directly withdraw heat from transformer oils, a stable supply of electric power is required through optimal maintenance of facilities. The water cooling tower installed outdoors, which uses the water supply as sprinkler water, experiences the most problems. Since more than 90% of the cooling water is reused, the dissolved composition in the water becomes concentrated due to long operating hours, and impurities dissolve in the water due to air flowing in from the outside, forming hard scales on the outer surface of the cooling tube, and in extreme cases, reacting with the tube material composition, leading to corrosion. As a result, not only is cooling efficiency lowered, but in extreme cases the cooling tube must be replaced. In this study, the characteristics and composition of the scales formed on the cooling tube were analyzed and corrosion characteristics of material types were identified in order to find an efficient maintenance method for cooling tubes. In addition, the degree of dissolution of various chemicals were investigated during the removal of scales that have been formed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.414-414
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• 2010

KSTAR vacuum vessel has been boronized by carborane ($C_2B_{10}H_{12}$) to reduce various kinds of impurities including carbon and oxygen from the wall, since carborane is solid, non-toxic, non-explosive and is easily evaporated, while diborane ($B_2D_6$) is toxic and explosive. To find the best wall condition for the removal of contaminants before application to KSTAR, various amounts (0.3g, 0.5g, 1g) of carborane are tested in a test chamber, where filament discharge was generated in the mixture of helium and carborane with the same KSTAR target pressure (~ 5 mTorr) from base pressure (${\sim}10^-7\;Torr$). Discharge is performed by a pulse sequence mode with 3 second power on and 5 second power off. Deposited films of a-C/B:H are characterized by ellipsometery, AES and XPS, and are compared with those of KSTAR.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.552-559
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• 1997

Fe (III) impurities in clay could be microbially removed by inhabitant dissimilatory Fe (III) reducing microorganisms. Insoluble Fe (III) in clay particles was leached out as soluble reductive form, Fe (II). The microorganisms removed from 10 to 45% of the initial Fe (III) when each sugar was supplemented to be in ranges of 1 - 5 % (w/w; sugar/clay). The microorganisms reduced 2.1 - 12.8 mol of Fe (III) per 100 mol of carbon in sugars metabolized when sugars such as glucose, maltose, and sucrose were used as sole carbon source. Bacillus sp. IRB-W and Pseudomonas sp. IRB-Y were isolated from the enrichment culture of the clay. The isolates were considered to participate in metabolizing organic compounds to fermentative intermediates with relatively little Fe (III) reduction at initial Fe (III) reduction process. By the microbial treatment, the whiteness of the clay was increased form 63.20 to 79.64, whereas the redness was obviously decreased form 13.47 to 3.55. This treatment did not cause any unfavorable modifications in mineralogical compositions of the clay.

• Clean Technology
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• v.19 no.3
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• pp.342-346
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• 2013

Several types of mesoporous silica-alumina adsorbents with varied $SiO_2/Al_2O_3$ ratios were prepared by spray pyrolysis and were used for the purification of the anticancer agent paclitaxel. When $S_{0.5}A_{0.5}$ (Silica/Alumina molar ratio = 0.5/0.5) was used, the highest purity (~27%) and yield (~63%) of paclitaxel were obtained from adsorbent treatment and hexane precipitation. Removal of impurities was confirmed by TGA analysis of the organic substances that were adsorbed to the adsorbent.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.149-150
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• 2006

Displayed result that handle particle contaminant and hydrospace organism included in number of ballast that is happened in ship using automatic back washing filter. Reason that remove first contaminant that is included in number of ballast is that heighten processing effect of after processing process. of the filter. Another advantage is to drop oft the solids with controlling revolution of drum screen in pretreatment filtration process. The fact that it is easy to attach and detach a several type of screen for getting the expected water quality is another advantage. Filter rotation speed at 1.0rpm is filter resistance 3.0bar and 3.0rpm is filter resistance 2.8bar. Filter out impurities from ballast water over 6.0rpm is filter resistance 2.6bar and 10rpm is filter resistance 2.5bar. Filtration system removal aquatic organism over $80{\mu}m$ in ballast water. This study shows that the filtration treatment system has a potential for the treatment of ballast water.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.103-107
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• 2008

This study was to execute the experiment for analyzing the quality characteristics of mortar by type of recycled sand by using the recycled sand produced by the manufacturing system by wet gravity separation in order to develop the removal device of impurities for the production of high-quality recycled sand. As a result, this study has sown that the mortar using the high-quality recycled sand through the manufacturing system by wet gravity separation in the fluidity property, strength property, and shrinkage property largely, compared with the mortar using low-quality recycled sand that not passed the device of sand flux. There was a tendency similar to the plane mortar. In conclusion, it was considered as various quality performances of the recycled sand were improved through the production stage of prototype.

• Tribology and Lubricants
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• v.33 no.6
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• pp.282-287
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• 2017

SU-8 is an epoxy-type photoresist widely used for the fabrication of high-aspect-ratio (HAR) micro-structures in micro-electro-mechanical systems (MEMS). To fabricate highly integrated structures, chemical mechanical polishing (CMP) has emerged as the preferred manufacturing process for planarizing the MEMS structure. In SU-8 CMP, an oxidizer decomposes organic impurities and particles in the CMP slurry remove the chemically reacted surface of SU-8. To fabricate HAR microstructures using the CMP process, the adhesion between SU-8 and substrate material is important to avoid the delamination of the SU-8 film caused by the mechanical-dominant material removal characteristic. In this study, the friction force during the CMP process is measured with a CMP monitoring system to detect the delamination phenomenon and investigate the delamination of the SU-8 film from the silicon substrate under various pressure conditions. The increase in applied pressure causes an increase in the frictional force and wafer-edge stress concentration. The frictional force measurement shows that the friction force changes according to the delamination phenomenon of the SU-8 film, and that it is possible to monitor the delamination phenomenon during the SU-8 CMP process. The delamination at a high applied pressure is explained by the effect of stress distribution and pad deformation. Consequently, it is necessary to control the pressure of polishing, which can avoid the delamination in SU-8 CMP.

• Polymer(Korea)
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• v.39 no.1
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• pp.99-106
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• 2015

The surface of nano-kenaf containing cellulose fibers was treated with alkali (NaOH) and their effects on the physical properties of the polypropylene (PP) composite were investigated. The treatment of alkali on the fibers increased the melt flow index (M.I.), elongation%, and impact strength, while it decreased the tensile strength, flexural modulus and heat deflection temperature (HDT) of the compound compared to the untreated one. It seemed the alkali treatment on the nano-kenaf fiber changed the character of the fiber due to removal of impurities and chemicals on the surface and resulted in decreased interfacial adhesion between the nano-fiber surface and the PP matrix and changed the character of the PP.

• Journal of Hydrogen and New Energy
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• v.27 no.2
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• pp.135-143
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• 2016

Biogas is a renewable fuel from anaerobic digestion of organic matters such as sewage sludge, manure and food waste. Raw biogas consists mainly of methane, carbon dioxide, hydrogen sulfide, and water. Biogas may also contain other impurities such as siloxanes, halogenated hydrocarbons, aromatic hydrocarbons. Efficient power technologies such as fuel cell demand ultra-low concentration of containments in the biogas feed, imposing stringent requirements on fuel purification technology. Biogas is upgraded from pressure swing adsorption after biogas purification process which consists of water, $H_2S$ and siloxane removal. A polymer electrolyte membrane fuel cell power plant is designed to operate on reformate produced from upgraded biogas by steam reformer.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.41-48
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• 2015

Stainless steel mesh has been used as a filter in various fields, including domestic, medical, etc. However, the surface before machining may have an adverse effect the product quality and performance because it is not smooth. Especially, adsorbed impurities in the surface result in difficulty in cleaning. Therefore, in this paper, we propose an improved surface quality through electrochemical polishing (ECP). Two electrodes, composed of STS304 (anode) and copper (cathode) underwent machining with two conditions according to polishing time and current density. As the polishing time and current density increase, the surface of curvature decreases, and roughness and material removal rate (MRR) improves. The machined surface roughness and image were obtained through the atomic force microscope (AFM) and stereoscopic microscope. The study also analyzed hydrophilic effect through contact angles. This obtains corrosion resistance, smoothness, hydrophilic property, etc.