• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.408-419
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• 2007

In the child, it is very important that he/she will have the ability to suppress aesthetic restorative materials of secondary caries. With the representative preventive material against caries, the importance of fluoride is more emphasized. This study examined the differences in fluoride release and re-uptake among some restorative materials, following a treatment of APF gel and fluoride varnish. The surface roughness was observed under scanning electron microscope. Studying this will provide for the research to find effective restorative materials and fluoride type in tooth caries prevention. It is applied from presence at a clinic that restorative materials are resin, flowable resin, compomer and glass ionomer. Fluoride release was measured at 24-hour intervals for 7 days, 3-day intervals from 8th to 38th day using an ion-selective electrode and analyzer. Then, the materials were treated with the fluoride gel and fluoride varnish respectively, fluoride release was measured and specimens were evaluated under scanning electron microscope for 4 weeks. It was concluded that 1. Fluoride was released for 38 days from restorative materials under 1 ppm in case of flowable resin, 1-2 ppm in compomer and 2-8 ppm in glass ionomer, a few of fluoride was released after 45 days 2. Fluoride has more releasing after application of APF gel than fluoride varnish. Fluoride re-uptake was observed under 0.6-0.2 ppm in fluoride varnish and 0.6-2.6 ppm in APF gel after starting the procedure one day(p<0.05). For the remaining 4 weeks, they demonstrated a similar release. 3. Specimens were evaluated under scanning electron microscope. Applied fluoride in the experimental group surface was rougher than the control group that did not receive fluoride application. Fluoride varnish group had a smoother surface than both the APF gel group and the varnish APF gel group that received a fluoride application.

• Membrane and Water Treatment
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• v.8 no.2
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• pp.149-160
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• 2017

This study investigated effects of NaOH cleaning on the intrinsic permeability of polyvinylidene fluoride (PVDF) membranes and flux recoveries and membrane resistances under various conditions encountered during ultrafiltration in water treatment plants. The NaOH cleaning using 10,000 mg/L NaOH led to discoloration of PVDF membranes and had little effect on water flux. The NaOH cleaning was efficient in removing the fouling layer caused by humic water. However, long filtration induced a fouling layer that was not removed easily by NaOH cleaning. The lower temperature during filtration yielded rapid increases in transmembrane pressure and decreases in NaOH cleaning efficiency. The alkaline cleaning of PVDF changed the membrane properties such as the hydrophobicity and morphology. Foulant properties, operational conditions such as temperature, and chemical agents should be considered for cleaning strategies for PVDF applied in water treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.84-88
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• 2021

The change of the photoluminescence properties of La2O3-CaF2-Al2O3-SiO2 glass-ceramics doped with rare earth material, that is used as laser and optical sensors, was analyzed according to heat treatment temperature. The heat treatment conditions for fabricating glass-ceramics were obtained through non-isothermal thermal analysis, and X-ray diffraction analysis was performed to determine the degree of crystal growth and kinds of crystal phases generated according to the heat treatment temperature. Using Scherrer's equation, it was predicted that crystals with a size of 25~40 nm would be generated inside the glass-ceramics. Photoluminescence (PL) analysis showed that the specimens heat-treated at 660℃ to 670℃ for 1 hour had the highest PL intensity. Also, from the CIE color coordinate analysis, all glass-ceramics specimens emitted red-orange light regardless of the heat treatment condition.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.3
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• pp.61-66
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• 1993

The interface properties of Fluoride/GaAs structures were investigated. It was foung that rapid thermal annealing(RTA) typically 800-850$^{\circ}C$for 1 min, was useful for improving the interface properties of that structures. The analysis by means of SIMS indicated that interdiffusion of each constitutional atom through the interface was negligible. The interfacial atom bonding model for RTA treatment was proposed. Bases on these results, inversion-type GaAs MISFET was fabricated using standard planar technologies.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.187-187
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• 2015

Polyvinylidene fluoride (PVDF) 코팅은 뛰어난 내후성으로 인해 Pre-painted metal에 많이 응용되며 주로 고가의 건축물 외장재에 적용되고 있는데, 수지의 열가소성 특성으로 인해 도막경화시 Baking 온도 및 냉각속도가 도막의 결정화도에 영향을 주어 가공특성이 상이하게 변함을 확인 하였다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.247-252
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• 2005

The typical treatment method for fluoride polluted water is the flocculation and precipitation method which usually is capable of reducing the fluoride concentration down to the level of about 10 ppm. However, this method is no longer effective for the treatment of contaminated water having less than 10 ppm of fluorides. To remove fluorides in polluted water from the fluoride concentration between 1 to 10 ppm, several adsorbents were prepared mainly based on an activated alumina and the fluoride removal efficiencies of the adsorbents were analyzed. The best fluoride removal efficiency was obtained when the activated alumina treated by sulfuric acid was used as the adsorbent. A proper calcination temperature for the sulfuric acid contained activated alumina was found to be about $500^{\circ}C$. An adsorption isotherm for the adsorbent was also obtained by using Freundlich model. The values of the constants in Freundlich isotherm model were calculated to be K=6.63 and 1/n=0.29 based on the results obtained from the series of batch type adsorption experiments.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.367-376
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• 2009

In this clinical research, the fluoride tape(SCMC-T-5) using fluoride(NaF) was developed and manufactured and the treatment effect of the fluoride tape in dentin hypersensitivity patients was evaluated and compared with the effect of existing fluoride varnish($CavityShield^{TM}$). Twenty two healthy adult patients(88 teeth) having dentin hypersensitivity participated in this clinical research and they were divided into two groups. The fluoride product was applied according to the manufacturer's instruction and the level of pain in the tooth after giving irritation using compressed air and ice stick was measured just after the application, after 3 days, after a week and after 4 weeks each using visual analog scale(VAS). In the experimental group, compared with the early VAS scores, all other VAS scores showed the significant decreases statistically. In the control group, all VAS scores except the VAS score of 34.091(air) measured 3 days after(using the irritation examination by the compressed air) showed the significant decreases statistically when compared with the early VAS scores. The fluoride tape and fluoride varnish used in this clinical research were able to treat the dentin hypersensitivity effectively.

• Journal of Korean society of Dental Hygiene
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• v.16 no.1
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• pp.77-83
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• 2016

Objectives: This study was carried out to investigate the effect of fluoride application after dental prophylaxis by the type of dental floss. Methods: Artificial caries lesion was made on the surface of cow's permanent teeth having sound enamel surface and vickers hardness number(VHN) was measured. Specimens were classified into APF gel group and artificial saliva group. Each group was divided into waxed floss group and unwaxed flossed group. All specimens were immersed into the artificial saliva for one minute and dental flossing was applied to waxed or unwaxed floss. After washing and drying, APF gel groups were applied with fluoride for four minutes and artificial saliva groups were immersed into the artificial saliva for four minutes. After treatment, specimens were measured by VHN and surface conditions of enamel were confirmed by scanning electron microscopy(SEM). Results: VHN of waxed flossing and fluoride application group increased to $6.78{\pm}2.75$. VHN of unwaxed flossing and fluoride application group increased to $7.36{\pm}2.51$. There was no significant difference between waxed and unwaxed groups(p>0.05). VHN of waxed flossing and artificial saliva group increased to $1.07{\pm}2.84$. VHN of waxed flossing and artificial saliva group increased to $1.05{\pm}3.13$. There was no significant difference between waxed and unwaxed groups(p>0.05). There was significant increase in VHN between waxed/unwaxed flossing and fluoride application. However, waxed/unwaxed flossing with artificial saliva showed no significant VHN increase. SEM demonstrated no residue on the enamel surface in the waxed flossing groups. Conclusions: No difference was found in the remineralization of enamel by waxed flossing or unwaxed flossing.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.109-112
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• 1964

A volumetric method of the determination of calcium carbonate and calcium fluoride in fluorspar concentrate is described. The carbonate is converted into solution by treatment of the sample in HNO$_3$-acetone (l% by volume) mixture, and the fluoride by treating the residue with H$_3BO_3$-HCl mixture. The calcium in the solution is determined volumetrically using EDTA standard solution. The selective dissolution of calcium carbonate by HNO$_3$-acetone mixture is superior to Bidtel's acetic method and little correction for the dissolution of calcium fluoride is needed. Triethanolamine is found to be superior to KCN in masking heavy metal ions.

• Toxicological Research
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• v.14 no.2
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• pp.163-169
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• 1998

Fluoride (F), over a narrow concentration range, increases bone formation. Aluminum (Ai) too is biphasic in its action on bone, being mitogenic at very low levels and inhibitory at higher levels. Both F and Al are present in finished drinking water where the chemical interaction of these two agents is well characterized. F and AI, given individually, accumulate preferentially in bone. In addition. in vivo studies have shown that F causes the co-accumulation of Al in bone. Thus, it was necessary to determine the interactive effect of these two agents on bone mitogenesis. Calvaria were obtained from neonatal CD-1 mice and cultured with various concentrations of F (0.05~19 ppm) as NaF, Al (2 ppb~2 ppm) as $AlCl_3$ , or F and Al for 3 days at $37^{\circ}C$ on a rotating roller drum. Alkaline phosphatase activity in calvaria and $\beta$-glucuronidase activity in culture medium were determined as a measures of bone turnover. Alkaline phosphatase activity in calvaria was significantly increased by F (0.05~2 ppm) treatment and $\beta$-glucuronidase activity was slightly increased in the culture medium of calvaria treated with 0.3 ppm Al. The combination of 19 ppm F and 0.3 ppm Al increased alkaline phosphatase activity in calvaria, but did not affect $\beta$-glucuronidase activity, suggesting the interactive effect of fluoride and aluminum on bone turnover.