• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.23-38
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• 1988

In order to investigate the material formed by application of fluoride on human dentin, exposed dentin of tooth cervix and sound dentin powder was treated by several fluoride solutions. The former was observed by scanning electron microscope and the latter was analysed by x-ray diffractometer and infrared spectrophotometer. The results obtained were as follows: 1. Application with NaF, $SnF_2$ and $Na_2PO_3F$ on exposed dentin of tooth cervix formed mineralized materials covered. 2. The amount of mineralized materials increased with time intervals of applying the fluorides. 3. The density of mineralized materials was highest in $Na_2PO_3F$ treatment group, and NaF treatment group was higher than $SnF_2$ treatment group. 4. $SnF_2$ remained in covering of mineralized materials. 5. Application with NaF and $Na_2PO_3F$ formed mineralized materials characterized apatitic crystals. 6. The crystallinity of mineralized materials was higher prominently in $Na_2PO_3F$ treatment group.

• Journal of Oral Medicine and Pain
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• v.21 no.1
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• pp.7-14
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• 1996

This study was performed to compare the anticarious effects of different fluoride agents(NaF, $NH_4F, TIF_4,$ APF gel, Elmex gel ) on artificial carious lesion. Enamel samples treated with 5 kinds of fluoride agents by pH cycling method were evaluated for fluorine uptake, enamel solubility, and microhardness. The results were as follows : 1. Greater fluoride uptakes were obtained in carious lesion treated with APF gel and $TiF_4$ solution than in that treated with other fluoride solutions. 2. TiF4 group was more resistant to acid than otter groups, but it was not significantly different with APF gel group. 3. Surface of enamel specimen was harkened by fluoride application and pH cycling. APF gel was more effective on enhancing surface hardness than control group. 4. APF gel, $NH_4F, TIF_4,$ solution were effective on fluoride uptake, enamel solubility, and microhardness.

• Proceedings of the Botanical Society of Korea Conference
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• 1995.07a
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• pp.109-130
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• 1995

지난 반세기간에 우리나라에 채소 육종은 주요 채소의 주년공급을 가능하게 하였으며, 토지 생산성의 향상, 상품화율의 증대, 품질의 향상 등의 면에서도 괄목할 만한 성과를 거두었고 인공교잡은 물론이고 웅성불임성과 자가불화합성의 활용에 의한 1대잡종 품종의 일반화로 채소 산업의 발전에 크게 기여하였다. 앞으로는 기왕의 업적을 심화시키는 한편, 생산비를 절감하기 위한 생력화, 기계화 재배용 품종 및 내제초제성 품종의 개발 환경보호 및 식품안정성의 확보를 위한 내병층성 품종 개발, 수출시장과 다양화하는 국내의 시장기호에 대응하고 가공 식품의 표준화된 품질관리를 지원할 수 있도록 품질 면에서의 개량과 신작물 또는 신생태형 품종의 개발에도 더욱 노력이 필요하다. 이러한 육종목표를 달성하기 위한 유전자원의 확보는 더욱 어려워질 것이며 유전 양식이 복잡하고, 환경요인의 작용이 상대적으로 크기 때문에 전통적인 육종 방법만으로는 목표달성에 필요한 인적, 물적, 시간적 소요가 훨씬 증가될 전망이다. 유전변이의 창성 및 확대, 유용 대립인자의 도입, 동정 및 선발, 그리고 종자생산을 위한 자가 불화합성 및 웅성불임성과 개화·수정 관련 유전인자의 발현 조절에 분자유전학의 보완적 역할이 기대되며 이렇게 되면 전통육종과 분자유전학간의 잡종강세로 품종 개량의 효율은 크게 높아질 것이다.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.48-54
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• 2006

Hydroxyapatite $(HAp,\;Ca_{10}(PO_4)_6(OH)_2)$/alumina composites were fabricated with the addition of fluorides, such as $MgF_2$ and $CaF_2$. In this study, the effect of fluorides on the inhibition of phase decomposition and the mechanical properties of HAp was investigated. Due to the higher solubility of F ion in HAp structure, $MgF_2$ additive was more effective compared to $CaF_2$ additive in the lowering decomposition temperature of HAp. Therefore, the dissociation tendency of HAp was fully inhibited below $1400^{\circ}C$. The mechanical properties of HAp composites with $MgF_2$ additive showed higher value (flexural strength: $\~170MPa$, Vickers hardness: $\~7\;GPa$, fracture toughness: $\~1.5\;MPam^{1/2}$) compared to $MgF_2-free$ composites. The linear thermal expansion coefficient of HAp composites with $MgF_2$ showed the value of $16.4\times10^{-6}/^{\circ}C\;at\;20\~400^{\circ}C $.

• Resources Recycling
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• v.6 no.1
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• pp.5-10
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• 1997

The aluminum was recovered from the middle size (Q1.0-12.0 mm) aluminum drosses using NaCl and KC1 mixuture as a basic salt flux. The maximum aluminum recovery was about 76.9% when 40% basic salt flux was added to aluminum dross at 850$^{\circ}$C for two hours. Also, aluminum remvery increased with increasing fluoride (1%-5%) addition to basic salt flux. But, there was no considerable effect due ta the increasing of viscosity when the fluorides were added over 5%, respectively. E s p d y , the most aluminum recovery was about 83.5% when 5% cryolite was added to 40% basic salt flux.

• Journal of Korean society of Dental Hygiene
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• v.19 no.1
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• pp.151-159
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• 2019

Objective: This study aimed to investigate the relation between rinsing time and the change in enamel surface after fluoride application on the enamel surface. Methods: We recruited two sample groups with different mouth rinsing times. While one group rinsed the teeth immediately after applying acidulated phosphate fluoride (APF) gel, the other group rinsed the teeth 30 minutes after APF gel application. In each group, we performed the following four-step experiment: (i) apply APF gel on the teeth, (ii) rinse the teeth, (iii) immerse the teeth in orange juice, and (iv) measure enamel surface microhardness and scan enamel surfaces. Results: The group that rinsed 30 minutes after treatment exhibited greater microhardness than the group that rinsed immediately after fluoride treatment. The former also showed smooth and regular crystallization, whereas the latter showed rough and damaged crystallization and irregular surfaces. Conclusions: Based on these observations, we conclude that delaying the rinsing time improves the dental caries preventive effect of fluoride.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.43-48
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• 2018

An etchant capable of forming a circuit in an FTO film that can replace ITO, which depends on full imports, was prepared. The etching solution is composed of 1 to 30% by weight of fluoride, 1 to 20% by weight of acid, 0.5 to 5% by weight of surfactant, 5 to 20% by weight of solvent, 0.5 to 10% by weight of corrosion inhibitor and the balance of water. This etchant can be etched using a dry film, thereby reducing the cost, and is free from bubbles and residue of the etchant. The characteristics of the etchant were etched in a time of 2 minute with a 100 nm thick FTO, and the etchant temperature was maintained at $50^{\circ}C$. An undercut of -0.00364% was obtained when put into a 2 minute etching solution. No harmful substances such as Cd, Pb, Hg and Cr components were measured. The use of FTO in Korea where rare earths do not exist can achieve localization and import substitution effect.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.5
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• pp.303-311
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• 2015

To determine the concentrations of selected 10 perfluorinated compounds (PFCs), a field study was conducted in the water body of Yeongsan River Water System. Raw water samples were collected in the spring and the fall, respectively, which included 18 sampling sites. Collected samples were equally mixed and then served as an analytical sample. The concentration of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) were in range of 20.80-92.0 ng/L and ND-28.40 ng/L respectively. Perfluorononanoate (PFNA) and perfluorohexanesulfonate (PFHxS) were ranged from ND to 42.20 ng/L and from ND to 11.47 ng/L. The detection frequencies of other PFCs selected in this study were very sparse at very low concentrations, except for PFOS, PFOA, PFNA and PFHxS. PFOS was higher detection frequency and concentration in both spring and fall, PFOA and PFNA were in spring, and PFHxS was in fall. As a result, the observed concentrations of PFCs in the downtown water area of Gwangju, located in the wastewater treatment plants, were relatively higher than other sampling points.

• Clean Technology
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• v.16 no.3
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• pp.172-181
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• 2010

Hydrofluoroethers (HFEs) with fluoride molecules in their structure which are evaluated as the third generation replacement alternatives to chlorofluorocarbons (CFCs) are known to be excellent for removal of nanoparticles and fluoride-type soils due to their low surface tension and high wetting index. In addition, HFEs have good physical properties with no flash point and excellent drying characteristics. But, HFEs also have shortcomings in that they are not effective for removal of organic soils due to their poor solubility in soil. In this study, $C_5$ HFE-based cleaning agents were formulated through addition of solvents such as isopropyl alcohol (IPA), ethyleneglycol monoether (EG), propyleneglycol monoethylether (PM) to HFE-7100 [$CF_3CF_2CF_2CF_2OCH_3$] or HFE-mec-f [$CF_3CHF=CF_2OCH_2CF_3$] with its maximum amount, respectively, in order to have no flash point for the safety in the working environment. These solvents are known to be excellent for dissolving organics in soil. Their physical properties and cleaning abilities for fluxes, water-insoluble cutting oils, and fluoride-type oils were evaluated and compared with those of other cleaning agents with single components. The experimental results show that the HFE-based formulated cleaning agents have various good physical properties which are almost similar to those of a single type of HFE cleaner. They show excellent cleaning ability for fluxes, water-insoluble cutting oils, and fluoride-type oils. These results indicate that the HFE-based formulated cleaning agents can be applicable to various industrial cleaning fields because of their good physical properties and cleaning abilities for various soils.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.41-46
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• 2008

Etching kinetics of $EAGLE^{2000TM}$ LCD glass was investigated using 2.5MHF-xMHCl$(x:0\sim8)$ acid mixtures. It was concluded that the reaction of HF-containing solutions with the glass was the rate-determining step for the dissolution process when considering following observations; the value of the activation energy $35\sim45$ kJ/mol and insensitivity of the dissolution rate to the etching time and the moving velocity of the glass into the solution. The etching rate linearly increased with increasing the HCl concentration in the etchant. It was also observed that the etched surface was as smooth as the original surface by addition of HCl and increase in etching temperature. This is due to the catalytic role of the $H_{3}O^{+]$ ions in the dissolution process.