• Membrane Journal
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• v.17 no.3
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• pp.184-190
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• 2007

This study reports on the pervaporation separation of a volatile organic compound(VOC), dichloromethane(DCM) from water using fluorinated copolysiloxaneimide membranes. The copolysiloxaneimide membranes were prepared from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA) and two diamines(polysiloxane diamine(SIDA), 2-(perfluorohexyl)ethyl-3,5-diaminobenzene(PFDAB)). By varying the ratio of flexible polysiloxane diamine(SIDA)/rigid fluorinated aromatic diamine(PFDAB) from 0/100 to 100/0 mol%, five copolysiloxaneimide membranes were prepared success- fully. The pervaporation properties of DCM/water were examined in terms of two diamine monomer ratio at room temperature and the feed composition of 0.05 wt% in water. It was found that the increase in SIDA content led to high permeation flux and pervaporation selectivity towards DCM by the enhanced sorption/sorption selectivity and diffusion coefficient/diffusion selectivity due to the increased hydrophobicity and fractional free volume.

• The Journal of the Korea Contents Association
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• v.17 no.7
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• pp.498-504
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• 2017

Oral health behavior such as toothbrushing one's teeth, using dentifrice and such are an important part of improving one's oral health and therefore quality of life. However, it is also necessary to research exposure to harmful chemical substances. Therefore, this study investigated the factors that affect researching fluorine exposure resulting from oral health behavior initiation so that correct oral health guidelines can be provided. As a result of applying the fluorine compound's oral exposure in the ConsExpo 5.0 model, adult males' oral external dose was at 0.000196 mg/kg, oral acute (internal) dose at 0.000196 mg/kg/day and oral chronic (internal) dose at 0.000465 mg/kg/day. In the case of females, the oral dose was at $4.1{\times}10^{-6}mg/kg$, oral acute (internal) dose at $4.1{\times}10^{-6}mg/kg$ and oral chronic (internal) dose at $9.99{\times}10^{-6}mg/kg/day$.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.2
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• pp.5-18
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• 2023

As a result of the survey on the emission status of fluorine-based chemicals in Korea, 13 kinds of substances, including hydrogen fluoride (91%) and perfluorocarbons (5%), were emitted in workplaces. By regional groups, about 98% was emitted in the Gyeongbuk, Gyeonggi and Chungcheong regions, and about 98% in three sectors of industry related to manufacture of electronic parts, chemicals and non-metallic mineral products. The detection status of PFOS and PFOA in domestic main rivers was continuously detected in the Nakdong River, the Geum River and the Anseong Stream estuary with high fluorine-related chemical emissions, and four sites of PFOS and two sites of PFOA were detected for the first time in 2021. PFOS and PFOA were continuously detected in relatively high concentrations in the rivers where there were many semiconductor and display related sectors of industry.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.1
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• pp.41-47
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• 2013

Purpose: To evaluate the usefulness of Integrated PET/CT and compare the gloss tumor volume (GTV) identified on CT, PET, PET/CT to that obtained from fluorodeoxyglucose (FDG). Materials and Methods: This experimental study was obtained using GE Discovery 690 (General Electric Healthcare, Milwaukee, MI, USA) PET/CT simulator with Gammex Laser System for five non-small cell lung cancer (NSCLC) patients. In order to increase the reproducibility of the patient setup, We have to fixed to patients using the Extended Wing Board. GTV delineation was painted using the EclipseTM ver.10 contouring program for CT, PET, PET/CT images. And then, We were to compare the changes in the GTV. Results: These results are drawn from 5 patients who have atelectasis or pneumonitis. Compared to CT defined GTV, PET was decreased by 10.5%, 11.8% and increased by 67.9%, 220%, 19.4%. PET/CT was decreased by 7.7%, 6.7%, 28% and increased by 232%, 24%. Conclusion: We were able to determine the usefulness of PET/CT simulator for NSCLC. PET/CT simulator in radiation therapy is useful to define the target volume and It is possible to delineate Objective and accurate target volume. It seems to be applicable to other areas in the near future.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.451-464
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• 2006

The purpose of this study was to search for an appropriate method of coating $TiO_2$ on orthodontic appliances. $TiO_2$ thin films were deposited on orthodontic wires and brackets using sol-gel, CVD (Chemical Vapor Deposition) and PE-CVD (Plasma Enhanced-CVD) methods. The roughness of $TiO_2$-coated surfaces was investigated via scanning electron microscope (SEM) and adhesive strength of $TiO_2$ thin films was measured by adhesive tape pull test. Methylene blue degradation test was carried out to evaluate the photocatalytic activity of $TiO_2$ and the corrosion resistance of $TiO_2$ thin films against fluoride solution was also analyzed by observing the surfaces of $TiO_2$-coated wires and brackets via SEM after immersion in sodium fluoride solution. Through the comparison of properties and photocatalytic activity of $TiO_2$ thin films according to the coating methods, the following results were obtained. Smoother surfaces of $TiO_2$ thin films were generated by CVD or PE-CVD methods than through the sol-gel method or the control. Adhesive strength of the $TiO_2$ thin films was highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Photocatalytic activity of $TiO_2$ thin films on methylene blue was the highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Corrosion resistance of $TiO_2$ thin films against fluoride solution was stronger in CVD and PE-CVD methods than in the sol-gel method. The results of this study suggest that the CVD or PE-CVD methods is more appropriate than the sol-gel method for $TiO_2$ coating on orthodontic wires and brackets.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.94-95
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• 1999

불소나 염소가 수소대신에 치환 되어있는 활로겐화 화합물인 염화불화탄화수소(CFCs chlorofluoro carbons)는 오존층 파괴물질 그리고 지구온난화 기체물질로 널리 알려져있다. 이러한 CFCs는 Mauna Loa, Niwot Ridge, South Pole과 같은 지구배경농도지역에서 70년대 후반부터 지속적으로 측정되어 오고 있다. 대기중 CFCs농도는 일반적으로 수백 ppt 수준으로 매우낮아 측정이 매우 어려운 것으로 알려져왔다.(중략)

• Polymer Science and Technology
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• v.21 no.5
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• pp.416-425
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• 2010

• The Korean Journal of Pesticide Science
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• v.14 no.3
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• pp.199-208
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• 2010

Phenylformamidine derivatives are well known as insecticides for their specific activity against the insects. It has now been established that they show insecticidal activity as agonists on the octopamine receptor. In order to get a highly active compound we have intensively exploited fluorine substituted-aromatic formamidines possessing N-dialkylaminosulfeny group. Up to now, there are several candidates we found: N-(dialkylamino)sulfenyl-N-methyl-N'-(4-fluoro-2-methylphenyl)formamidines. The miticidal activity of Compound 29 show five-fold higher than Amitraz.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.173-178
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• 1988

The purpose of the study was to confirm the influence of fluoride to enamel decalcification. Specimens were prepared from 20 extracted teeth. Every tooth was sliced into 4 pieces by means of seperating disc. The pieces with sound enamel were distributed to 4 groups. 1st group was treated with 0.5% NaF solution for 2 minutes. 2nd group was treated with 0.5% NaF solution for 10 minutes. 3rd group was treated with 1% NaF solution for 2 minutes. 4th group was treated with 1% NaP solution for 10 minutes. The enamel surface of each specimen were decalcified with 30% $H_3PO_4$ for 2 minutes and the findings through electron microscope were as follows; 1. The degree of decalcification on the 1st group was greater than that of the 2nd group. 2. Roughness of the 3rd group was slightly higher than that of the 4th group. 3. Under the same procedure of decalcification, the specimen treated by higher conceutration of NaF solution for same length of time showed less decalcified picture. 4. Under the same procedure, of decalcification, the specimens treated by same concentration of NaF solution for different length of time, were compared and found longer the time less decalcified.

• Journal of the korean academy of Pediatric Dentistry
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• v.11 no.1
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• pp.151-157
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• 1984

The purpose of this study was to compare the growth-inhibiting effect of sodium fluoride and stannous fluoride on a cariogenic strain of Streptococcus mutans exposed to the different concentration of $SnF_2$ and NaF The result were as follows: 1. The growth rate of the Streptococcus mutans was unaffected by 75 ppmF, slowed by 150 ppmF, and immediately arrested by 300 or 600 ppmF where increments of NaF were added to actively growing 12-hour broth culture. 2. $SnF_2$ slowed the growth rate at 75 ppmF, was to bactericidal initially at 150 and 300 ppmF, and was to totally bactercidal at 600 ppmF. 3. $SnF_2$ has been shown to be more effective than NaF in inhibiting the growth activity of Streptococcus mutans. 4. The inhibitory effect of fluoride compounds on the growth of Streptococcus mutans was increased in the decreased pH at concentration of 600 ppmF.