• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.107-107
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• 2018

무전해 니켈도금 용액의 성분은 Ni(II)염, 환원제, 적합한 금속 배위 리간드, 안정제 및 특정 특성 요구에 대한 첨가제를 포함한다. 일반적으로 도금 욕에는 미량의 안정제가 함유되어 있다. 만약 적절한 안정화 시스템이 없는 도금 욕에서 도금 공정 시 도금 시작 직후에 많은 양의 니켈 플레이크(Ni flake)가 생성되어 빠르게 도금 용액이 분해되어 더 이상 도금이 어렵게 된다. 그러나 무전해 도금 욕에서 안정제의 역할 및 도금 층에 미치는 영향에 대한 연구는 여전히 부족한 실정이다. 따라서 본 연구에서는 $Pb^{2+}$ 안정제 농도가 도금 층에 미치는 영향과 캐비테이션 침식 실험을 통해 그 내구성을 평가하고자 하였다. 무전해 니켈코팅을 위한 모재는 회주철(FC250)을 $19.5mm{\times}19.5mm{\times}5mm$의 크기로 가공하였다. 회주철의 인장강도는 $330N/mm^2$이며, 그 성분 조성(wt.%)은 3.23 C, 1.64 Si, 0.84 Mn, 0.016 P, 0.013 S 그리고 나머지는 Fe이다. 시험편은 SiC 페이퍼 #1200까지 연마하여 시험편의 표면 거칠기는 $1.6-2.1{\mu}m$ 범위 내로 제작하였다. 무전해 도금 전 시험편은 탈지를 위해 상온의 아세톤 용액에서 3분간 초음파 세척하고, $90^{\circ}C$의 알카리 수용액으로 5분간 세척하였다. 그리고 표면 활성화를 위한 산세척은 5% 황산용액에서 30초 동안 실시하였다. 도금조로 500mL 비커를 사용하였으며, 모든 시험편은 2시간 동안 무전해 니켈도금을 실시하였다. 그리고 니켈도금 층의 내식성과 내구성을 평가하기 위해 전기화학적 분극 실험을 통한 타펠분석과 ASTM G32 규정에 의거한 캐비테이션 침식 실험을 실시하였다. 그 결과 안정제 농도가 도금 속도와 도금 층의 성분 변화에 크게 영향을 미쳤으며, 그에 따라 도금 층의 내식성과 내구성이 크게 변화되었다.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.58-64
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• 2005

Several tests were conducted to determine the optimum operational conditions of soil washing techniques for floe-forming arsenic-contaminated soils, collected from D abandoned Iron-mine in Korea. The optimum cut-off size was 0.15 mm $(sieve\;\#100)$, about $94\%$ of the mass of soils. Both sodium hydroxide and hydrochloric acid were effective to remove arsenic and the optimum mixing ratio (soil [g] : washing solution [mL]) was 1:5 for both washing agents. Arsenic concentrations, determined by KST Methods, for the dried floe solids obtained from flocculation at pH 5-6 were $990\~1,086\;mg/kg$ dry solids, which were higher concentrations than at the other pH values. Therefore, batch tests for sequential washings with or without removing floc were conducted to find the enhancement of washing efficiencies. After removing floe with 0.2 M HCl, sequential washings of 1 M HCl followed by 1 M NaOH showed the best results (15 mg/kg dry soil). The arsenic concentrations of washing effluent from each washing step were about $2\~3\;mg/L$. However, when these acidic and basic effluents were mixed together, arsenic concentration was decreased to be less than $50\;{\mu}g/L$, due to the pH condition of coagulation followed by precipitation for arsenic removal.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.107-115
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• 2013

Purpose: This study was conducted to investigate the change of soft contact lens parameters after eyeliner deposition and compare the cleaning efficiency and the recovery rate of lens parameters by different cleaning methods. Methods: The eyeliner was deposited on three types of soft contact lenses made of different materials for 1 hour, 4 hours and 6 hours and those lenses were washed by the eyeglasses ultrasonic cleaning and by hands. The changes in visible light transmittance, diameter and surface of those lenses were compared before and after cleaning of the lens. Results: The visible light transmittance of soft contact lenses decreased along with the deposition time of eyeliner. The patterns of the eyeliner deposition on soft contact lens appeared differently depending on the physical properties of the lens material. Thus, the largest eyeliner deposition was found on narafilcon A lens. The diameters of hilafilcon B and etafilcon A lenses were decreased, however, the diameter of narafilcon A lens was increased. The cleaning efficiency of the eyeliner deposition was greater with the multipurpose solution by hands than with the eyeglasses ultrasonic cleaner. However, the recovery of lens parameters such as the lens diameter, visible light transmittance and lens surface due to the eyeliner deposition to its original state was limited. Conclusions: From these results, it is suggested to minimize eye makeup when wearing soft contact lens. Furthermore, the reduced wearing time and shorter cycle of lens replacement may be needed by considering a change of lens parameter when the repeat eye makeup is applied.

• Clean Technology
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• v.16 no.1
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• pp.39-45
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• 2010

In this paper, 4 bundle modules of PVDF hollow fiber membrane from Woori Tech company (Korea) were manufactured in a treatment capacity of 10 ton/day. A membrane bioreactor (MBR) pilot plant was installed at Sooyoung Wastewater Treatment Plant in Busan. An alternating aeration process was selected to avoid the concentration profile of suspended solid (SS) in the MBR. For stable operation, raw wastewater with mixed liquor suspended solid (MLSS) of about 1,000 ppm, which was in-flowed from the aeration tank of the wastewater treatment plant, was fed and filtered through the pilot plant. Subsequently the pilot plant were washed three times with washing water: once with ethanol solution, once with a solution of 5% NaOCl, and finally with washing water. After the chemical washing, the remaining water in the MBR was fed into the pilot plant. As a result, the SS removal efficiency was found to be more than 99.9%. The amount of filtrate with the aeration tank influent decreased by 16%, compared with that from the initial conditions, giving rise to 30% increase in the suction pressure. These results were used to set up continuous operation conditions. The results from the continuous operation with influent MLSS of 1,900 mg/L showed that the SS removal efficiency was about 99.99% and that the amount of filtrate and the suction pressure were $42{\sim}52L/m^2$ and 16~20 cmHg, respectively, indicating stable operation of the pilot plant. However, for the reuse of wastewater, methods need to be sought to avoid growth of algae which affects the SS removal efficiency at inlet and outlet of the permeate tank.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.11-18
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• 2021

Nano bubble water is used in various washing processes, including cleaning of solar panels, salt rejection of roads, and cleaning precision parts of machines. High cleaning efficiency and water conservation are obtained by applying nano bubbles during pretreatment of the marine waste cleaning system. This study compared the salt rejection of nano bubble water, and it was revealed that marine waste was produced by wood immersed in 200,000 mg/L NaCl solution. Using tap water and nano bubble water for washing, comparisons of the surface salt concentrations of wood were determined according to the nozzle, orifice diameter, pump speed and washing time. Decreased surface salt concentration was observed on the wood surface with increasing washing time. Water consumption was optimal between 5- and 10-seconds washing time. Increasing orifice diameter of the nozzle reduced the spraying pressure, with consequent increase in the wood surface salt concentration, thereby establishing the importance of orifice diameter of the nozzle. Compared to levels obtained with tap water, salt concentration of the wood surface after washing with nano bubble water was 2.2% lower with sector nozzle, and 30.9% lower with circular nozzle. In the washing experiment using nano bubble water, the salt concentration on the wood surface was about 9.5 mg/L lower when washed with sector nozzle than the circular nozzle.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.1-8
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• 2022

Purpose. The present study aimed to investigate the effective cleaning of healing abutment (HA) using Healing abutment case (HA case) by observing oral microorganisms with phase contrast microscope. Materials and methods. 32 patients with two or more implants placed in the same jaw, a total of 64 HAs (experimental group 32, control group 32) were selected and the control was cleaned with an alcohol swab. At the first and second visits, each group was observed before cleaning, and the experimental group was additionally observed after cleaning at the first visit. A 400× phase contrast microscope was used for the observation of oral microorganisms for its amounts. Results. There was no significant difference in the amount of oral microorganisms was found between the groups at the first visit, no significant difference according to gender, maxilla or mandible, and buccal or lingual surface. There was a statistically significant difference in the amount of oral microorganisms according to supra-gingival and sub-gingival (P<.05), There was also a significant difference in the comparison before and after cleaning in the experimental group (P<.05). There was a significant difference in the amount of oral microorganisms in each group at second visit (P<.05). Conclusion. Healing abutment cleaning using healing abutment case solution is more effective than simple cleaning with alcohol swab.

• Journal of Conservation Science
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• v.28 no.3
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• pp.229-233
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• 2012

This research was to evaluate conservational stability of cleaning treatment and color recovery by weak acid treatment on ivory. Before this experiment, had an ivory identification such as black light and schreger angle to find whether it is authentic or not. In wet cleaning treatment on ivory, used polar solvents such as distilled water, acetone, ethyl alcohol and acetic acid which usually used for cleaning ivory and bones. After cleaning took a experiment to evaluate conservational stability in surface observation, calculate weight and color difference. Following these results, these polar solvents were stable on the ivory samples. On the other hand, in weak acid treatment, used samples that were exposed by UV-A, UV-B, UV-C for 1 weeks, to restore its color from changed to original color. After treatment, found tiny cracks and exfoliation on the surface. Moreover, the color changed when it is treated by lemon juice, so, it is impossible to adapt.

• Restorative Dentistry and Endodontics
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• v.34 no.6
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• pp.484-490
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• 2009

The purpose of this study was to evaluate the effect of soft chelating irrigant on the sealing ability of root fillings by using a glucose leakage test. A total of 45 single-rooted teeth were selected for the study. The teeth were decoronated leaving a total length of 13mm. The root canals prepared using K3 NiTi rotary instruments to an apical dimension of size 45(0.06 taper). The specimens were then randomly divided into 3 experimental groups of 13 roots each and 2 control groups of 3 roots each. Specimen in each group were prepared with different irrigation protocols : group 1, 2.5% NaOCl; group 2, 2.5% NaOCl and 17% EDTA: group 3, 2.5% NaOCl and 15% HEBP. The root canals were filled with gutta-percha and AH Plus sealer using lateral condensation. After 7 days in $37^{\circ}C$, 100% humidity, the coronal-to-apical microleakage was evaluated quantitatively using a glucose leakage model. The leaked glucose concentration was measured with spectrophotometry at 1, 4, 7, 14, 21 and 28 days. There was a tendency of increase in leakage in all experimental groups during experimental period. HEBP-treated dentin showed no significant difference with EDTA-treated dentin during experimental period. From the 21th day onward, HEBP-treated dentin showed significantly lower leakage than smear-covered dentin. HEBP-treated dentin displayed a similar sealing pattern to EDTA-treated dentin and a better sealing ability than smear-covered dentin. Consequently, a soft chelator(HEBP) could be considered as the possible alternative to EDTA.

• Membrane Journal
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• v.30 no.2
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• pp.138-148
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• 2020

The purpose of this study was to identify the cleaning efficiency of fouled multi-bore hollow fiber membranes after purification of contaminated water. The PSf (polysulfone) based hollow fiber membrane manufactured by Pure & B Tech Co., Ltd. Was used in this study. The antifouling characteristics during the water treatment were studied using bovine serum albumin (BSA) as a model compound and the chemical resistance was evaluated after long-term impregnation in sodium hypochlorite (NaOCl) solution and Citric acid to understand the long term stability of the membranes. Water permeability and mechanical strength of the membranes after prolonged chemical exposure was measured to observe the change in mechanical stability and long term performance of the membrane. moreover, the recovery efficiency was also evaluated after chemical enhanced backwashing of a membrane contaminated with bovine serum albumin. The PSf hollow fiber membrane exhibited excellent chemical resistance, and it was confirmed that the efficiency of sodium hypochlorite was high as a result of chemical enhanced backwashing.

• Journal of Life Science
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• v.12 no.6
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• pp.694-699
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• 2002

The present experiment was carried out to determine the effect of seed-coat softening by various chemicals, washing, chilling, and light treatment alone and in combination during desiccation of seeds on germination of gourd (Lagenaria siceraria Standl.) seeds. Potassium hydroxide, sodium hydroxide, acetone, acetonitrile, and acetamide were used as chemicals for the softening. Washing, prechilling, drying and light treatment of the softened seeds were done for a hour with tap water, for one or three weeks at 3$^{\circ}C$, 12 hr at 35$^{\circ}C$, and 14 hr a day at 3$0^{\circ}C$ with red light illumination or darkness, respectively. FR-yongjadaemok and FR-kunghap were used as test cultivars. Seed-coat softening with 10% acetone and acetonitrile for 1 hour enhanced and accelerated seed germination compared to the other chemicals and water imbibition. KOH treated for the softening was necessary to increase the germination rate of seeds for following chilling, but acetone did not influence their germinability regardless of chilling. Washing the softened seeds in tap water increased the germination rate in comparison with no-washing. During desiccation of the seeds sequentially treated with the softening, washing and chilling, red light treatment showed higher germination rate than dark one, suggesting that red light treatment are necessary during desiccation.