• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.3
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• pp.221-230
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• 2006

Recently, the need for esthetic results has increased the interest for all-ceramic crown prosthesis. Furthermore, the development of zirconium core via CAD/CAM system has allowed the all ceramic restorations to be applied to almost all fixed prosthesis situations. But, the increased strength has been reported to increase in proportion with the bond strength of cement, and recently, the tribochemical system which increases the bond strength through, silica coating and silanization has been introduced. The purpose of this study was to compare the $Rocatec^{TM}$ system and $CoJet^{TM}$ system with the traditional acid etching and silanization method of the irconium based ceramic. The surface character was observed via SEM(X2000), and the bond strength with the resin cement were measured. 50 In-Ceram Zirconia (Adens, Korea) discs were fabricated and embedded in resin, group 1 was treated with glass-bead blasting and cleaning, group 2 was treated with 20% HF for 10 minutes and silanized, group 3 was treated with the $Rocatec^{TM}$ system, and group 4 was treated with the $CoJet^{TM}$ system. Each group was comprised of 10 specimens. The specimens were cemented to a $3mm{\times}5mm$ resin block with Super-Bond C&B. The shear bond strength was measured with the $Instron^{(R)}$ 8871 at a crosshead speed of 0.5mm/min. The results were as follows. 1. According to SEM results, there were little difference between group 1 & group 2, but in group 3 and 4, silica coating was detected and there was increase in surface roughness. 2. The shear bond strength decreased in the order of group 3(46.28MPa), group 4(42.04MPa), group 2(31.56MPa), and group 1(27.46MPa). 3. There was significant differnce between group 1&2 and group 3&4(p<0.05). From the results above, it can be considered that the conventional method of acid etching and silane treatment cannot increase the bond strength with resin cements, and that by applying the tribochemical system of $Rocatec^{TM}$ system and $CoJet^{TM}$ system, we can achieve a stronger all ceramic restoration. Further studies on surface treatments to increase the bond strength are thought to be needed.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.1
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• pp.57-65
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• 2020

To prevent loss of hair protein during hair washing process by water through, a shield coating the pathway of water molecules was studied. Hydrophobic virgin hair, hydrophilic hair, which was damaged only methyleicosanoic acid (18-MEA) on the surface, and a repaired hair re-bound 18-MEA, were prepared and water mass changes by as heat were measured. Results showed that hydrophobic hairs followed bi-exponential function of 39 s and 151 s and other two hairs exhibited fast- and mono-exponential decay with 83 s, reflecting the extraction of water molecules without any resistance at the hydrophobic surface. On the assumption that hydrophobic surface resists an extraction of protein in water during the wash, the protein concentrations were compared from the hair of hydrophobic and hydrophilic surface. The extracted hair proteins were 179 and 148 ㎍/mL from the hair coated with hydrophilic polyethylene glycol (PEG) and hydrophobic polydimethylsiloxane (PDMS), respectively. This study suggested that hydrophobic coating on the hair surface could be used to prevent protein loss in wash, represented by LFM. In conclusion, this research provides some useful information to contribute to the development of hair washing products that can prevent protein loss in the cleaning process by granting hydrophobic coatings.

• Resources Recycling
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• v.30 no.5
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• pp.38-48
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• 2021

In this study, we determine the optimal process conditions for selectively recovering Si from a solar cell surface by removal of impurities (Al, Zn, Ag, etc.). To selectively recover Si from solar cells, leaching is performed using HCl solution and an ultrasonic cleaner. After leaching, the solar cells are washed using distilled water and dried in an oven. Decompression filtration is performed on the HCl solution, and ICP-OES (Inductively Coupled Plasma Optical Emission spectroscopy) full scan analysis is performed on the filtered solution. Furthermore, XRD (X-ray powder diffraction), XRF (X-ray fluorescence), and ICP-OES are performed on the dried solar cells after crushing, and the purity and recovery rate of Si are obtained. In this experiment, the concentration of acid solution, reaction temperature, reaction time, and ultrasonic intensity are considered as variables. The results show that the optimal process conditions for the selective recovery of Si from the solar cells are as follows: the concentration of acid solution = 3 M HCl, reaction temperature = 60℃, reaction time = 120 min, and ultrasonic intensity = 150 W. Further, the Si purity and recovery rate are 99.85 and 99.24%, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.155-163
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• 2017

Membrane filtration has become more popular in drinking water treatment recently, since the filtration can control not only particulate matters but also pathogenic microorganisms such as giardia and cryptosporidium very effectively. Pilot-scale ($120m^3/d$ of treatment capacity) and test-bed ($25,000m^3/d$ of treatment capacity) microfiltration experiments were conducted to find optimum operating mode and the critical flux. Optimum operating mode of pilot-test was assessed as inflow 1.0 min, filtration 36.5 min, air backwash 0.9 min, backwash 1.0 min and outflow 1.0 min with 50 LMH ($L/min{\cdot}m3^$) of critical flux. Critical Flux was calculated to be $50L/m^2-h$ (within TMP 0.5 bar) based on the increase formula of the transmembrane pressure difference according to the change of time at Flux 20, 40, 56 and 62 LMH in pilot operation. Chemical cleaning was first acid washed twice, and alkali washing was performed secondarily, and a recovery rate of 95% was obtained in the test-bed plant. The results of operating under these appropriate conditions are as follows. Turbidity of treated water were 0.028, 0.024, 0.026 and 0.028 NTU in spring, summer, autumn and winter time, respectively. Microfiltration has superior treatment capability and performance characteristics in removing suspended solids and colloidal materials, which are the main cause of turbidity and important carrier of metal elements, and it has shown great potential in being an economically substitute to traditional processes (sand filtration).

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.760-769
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• 1993

Solvent-free low foaming scouring agents(LFSA) were prepared by blending of polyoxyethylene(30) octadecylbenzylammonium chloride(POAC), block copolymer of propylene oxide-ethylene oxide[p(PO-b-EO) glycol], Sedlan FF-200(FF-200) and sulfonic acid-amine condensate of polyoxyethylene(10) nonylphenyl ether(PSAC). In consequence of several tests, FF-200/POAC/p(PO-b-EO) glycol/PSAC/water (20g/10g/5g/5g/60g) mixture (LFSA-5) showed good cleaning power, penetrating ability, emulsifiability and stability to alkali, and gave less problem in water pollution. Scouring effect of LFSA-5 was investigated by the change of percentage of exhaustion before and after scouring at various dyeing temperatures. The percentage of exhaustion of the unscoured PET fabric was 4.5% at $70^{\circ}C$, while that scoured with LFSA-5 was 1.3% at the same temperature, which proved LFSA-5 to be a good scouring agent. Moreover, the foaming power of LFSA-5 measured by Ross and Miles method was 6mm foam height immediately after foaming, and that measured by Ross and Clark method was less than 300mm foam height at $30^{\circ}C$, and 20mm at $80^{\circ}C$. As a result, LFSA-5 proved a good low foaming scouring agent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.438-444
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• 2015

The aim of this research was to apply a HACCP system (Hazard Analysis Critical Control Point) to fermented milk. The main ingredients of fermented milk, work facilities and workers were obtained from a company named YD, which is located in Seobuk-gu, Cheonan-si between November 5 2013 to April 13, 2014. A manufacturing process chart was prepared by referring to the manufacturing process of fermented milk manufacturers in common. The manufacturing process chart was made with raw materials; Raw milk, High Fructose Corn Syrup, Oligosaccharides, Lactic Acid bacteria and Subsidiary ingredients, Warehousing of packaging materials, Storage, Input, Preheating, Mixing, Homogeneity, Sterilization, Precooling, Culture, Filtration, In packaging, Out packaging, Storage, and Consignment, as listed Table 1. The results of the microbiological hazard analysis on the raw materials was safe after sterilization($90^{\circ}C{\pm}5^{\circ}C$, $35{\pm}3min.$) On the other hand,a microorganism test of an environment and workers suggested that the microbiological hazard should be reduced through systematic cleaning and disinfection accompanied by improved personal hygiene based on hygienic education on workers and the management of microorganisms in air.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.06a
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• pp.135-153
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• 1998

Nanofiltration (NF) is a recently introduced term in membrane separation. In 1988, Eriksson was one of the first authors using the word 'nanofiltration' explicitly. Some years before, FilmTech started to use this term for their NF50 membrane which was supposed to be a very loose reverse osmosis membrane or a very tight ultrafiltration membrane. Since then, this term has been introduced to indicate a specific boundary of membrane technology in between ultrafiltration and reverse osmosis. The application fields of the NF membranes are very broad as follows: Demeneralizing water, Cleaning up contaminated groundwater, Ultrapure water production, Treatment of effleunts containing heavy metals, Offshore oil platforms, Yeast production, Pulp and paper mills, Textile production, Electroless copper plating, Cheese whey production, Cyclodextrin production, Lactose production. The earliest NF membrane was made by Cadotte et al, using piperazine and trimesoyl chloride as monomers for the formation of polyamide active layer of the composite type membrane. They coated very thin interfacially potymerized polyamide on the surface of the microporous polysulfone supports. The NF membrane exhibited low rejections for monovalent anions (chloride) and high rejections for bivalent anions (sulphate). This membrane was called NS300. Some of the earliest NF membranes, like the NF40 membrane of FilmTech, the NTR7250 of Nitto-Denko and the UTC20 and UTC60 of Toray, are formed by a comparable synthesis route as the NS300 membrane. Commercially available NF membranes nowadays are as follows: ASP35 (Advanced Membrane Technology), MPF21; MPF32 (Kiryat Weizmann), UTC20; UTC60; UTC70; UTC90 (Toray), CTA-LP; TFCS (Fluid Systems), NF45; NF70 (FilmTec), BQ01; MX07; HG01; HG19; SX01; SX10 (Osmonics), 8040-LSY-PVDI (Hydranautics), NF CA30; NF PES 10 (Hoechst), WFN0505 (Stork Friesland). The typical ones among the commercially available NF membranes are polyamide composite membrane consisting of interfacially polymerized polyamide active layer and microporous support. While showing high water fluxes and high rejections of multivalent ions and small organic molecules, these membranes have relatively low chemical stability. These membranes have low chlorine tolerance and are unstable in acid or base solution. This chemical instability is appearing to be a big obstacle for their applications. To improve the chemical stability, we have tried, in this study, to prepare chemically stable NF membranes from PVA. The ionomers and interfacially polymerized polyamide were used for the modification of'the PVA membranes. For the detail study of the active layer, homogeneous NF membranes made only from active layer materials were prepared and for the high performance, composite type NF membranes were prepared by coating the active layer materials on microporous polysulfone supports.

• Membrane Journal
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• v.19 no.4
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• pp.324-332
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• 2009

This study aimed to measure chemical resistance properties of the microfiltration flat-sheet membrane made by Chlorinated Polyvinyl Chloride (CPVC) with respect to the immersed time. The solutions of effective chlorine 0.5 wt% NaClO, HCl 1 wt% and pH 4 buffer under acidic condition, NaOH 4 wt% and pH 10 buffer under alkine condition were used as widely applied chemicals for membrane washing. The CPVC membrane samples were immersed in the above chemical solutions during 1, 3, 5 and 10 days at 5, 25 and $50^{\circ}C$, respectively. After then, the tensile strength and elongation at break as the chemical durability for the samples were measured and evaluated. The tensile strength decreased within 5% at $5^{\circ}C$, but decreased up to 17% at 25 and $50^{\circ}C$ for 0.5 wt% NaClO solution mainly used for membrane cleaning. The chemical resistance of CPVC membrane was good enough for HCl 1 wt% and pH 4 buffer acid solutions, but the most vulnerable for NaOH 4 wt% solution.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.2
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• pp.139-147
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• 1991

The preservative effect of cellophane film packing on the quality of semi-salted and dried mackerel was studied. The product(P) of semi-salted and dried mackerel was prepared from raw mackerel by filleting, cleaning, soaking in 15%9v/w) salt solution for 30min, draining, packing with cellophane film (PT# 300, thickness:$20{\mu}{\textrm}{m}$) and drying for 4 hrs at $40^{\circ}C$ in hot air dryer. The product (C) was also prepared without cellophane film packing after draining. The product (C) and (P) were stored at $5.0{\pm}0.5^{\circ}C$. After processing and during storage, moisture content of product (P) was higher than that of product (C), but contents of VBN(volatile basic nitrogen), amino nitrogen and TMA of product (P) on dry basis were lower than those of product (C). Viable cell count, TBA value, peroxide value and decreasing rate of polyenoic acid of product (P) were also lower than those of product (C). In sensory evaluation, the shelf life of product (C) was about 9 days and that of product (P) was about 14 days. From the results of chemical and sensory evaluation, it was concluded that cellophane film packing was a good condition for preserving the quality of semi-salted and dried mackerel.

• Resources Recycling
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• v.31 no.6
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• pp.60-65
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• 2022

This study presents the carburization process for recycling sludge, which was formed during silicon wafer machining. The sludge used in the carburization process is a mixture of silicon and silicon carbide (SiC) with iron as an impurity, which originates from the machine. Additionally, the sludge contains cutting oil, a fluid with high viscosity. Therefore, the sludge was dried before carburization to remove organic matter. The dried sludge was washed by acid cleaning to remove the iron impurity and subsequently carburized by heat treatment under vacuum to form the SiC powder. The ratio of silicon to SiC in the sludge was varied depending on the sources and thus carbon content was adjusted by the ratio. With increasing SiC content, the carbon content required for SiC formation increased. It was demonstrated that substoichiometric SiC_x (x<1) was easily formed when the carbon content was insufficient. Therefore, excess carbon is required to obtain a pure SiC phase. Moreover, size reduction by high-energy milling had a beneficial effect on the suppression of SiC_x, forming the pure SiC phase.