• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.453.1-453.1
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• 2014

Fluorine-doped tin oxide (FTO), which is commonly used in dye-sensitized solar cells (DSSCs), is a promising material of transparent conducting oxides (TCOs) because of advantages such as high chemical stability, high resistance, high optical transparency (>80% at 550nm), and low electrical resistivity (${\sim}10-4{\Omega}{\cdot}cm$). Especially, dye-sensitized solar cells (DSSCs) have been actively studied since Gratzel's research group required FTO substrate as a charge collector. When FTO substrates are used in DSSCs, photo-injected electrons may experience recombination at interface between dye-bonded semiconductor oxides ($TiO_2$) on FTO substrate and the electrolyte. To solve these problems, one is that because recombination at FTO substrate cannot be neglected, thin $TiO_2$ layer on FTO substrate as a blocking layer was introduced. The other is to control the morphology of surface on FTO substrate to reduce a loss of electrons. The structural, electrical, and optical characteristics of morphology controlled-FTO thin films as TCO materials were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Hall Effect Measurement, and UV spectrophotometer. The performance of DSSCs fabricated with morphology controlled FTO substrates was performed using Power Conversion Efficiency (PCE). We will discuss these results in detail in Conference.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.595-599
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• 2001

The mechanisms of pretilt angle generation for a nematic liquid cystal (NLC) using a photodimerization method with obliquely polarized UV exposure on the various new photo-crosslinkable polymer were studied. A good thermal stability of all the photo-crosslinkable polymers was obtained by thermogravimetric analysis (TGA) measurement until 450$\^{C}$. High pretilt angle of the NLC was observed by polarized UV exposure on the three kinds of the photo-crosslinkable polymers containing biphenyl(BP), decyl(de), and cholesteryl(chol) group, respectively. However, the low pretilt angle of the NLC was measured by obliquely polarized UV exposure on the two kinds of the photo-crosslinkable polymers containing fluorine and chalcone group. Consequently, the high NLC angle generated is attributable to the biphenyl and alkyl moieties, and photo-dimerized chalcone group of the photopolymer.

• Polymer(Korea)
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• v.35 no.2
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• pp.166-170
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• 2011

This study reported the synthesis of perfluoropolyether intermediate (TP-$COOCF_3$) having a $CF_3$ functional group via electrophilic fluorine substituting direct fluorination from PFPE intermediate (TP-$COOCH_3$) having a $CH_3$ functional group, which was synthesized by the ring opening polymerization and methyl esterification of HFPO. The effects of reaction conditions such as the amount of solvent, fluorine partial pressure, reaction time, were investigated. The results showed that the yield of fluorination reaction became the highest when the reaction was carried out in a mild condition for a long reaction time, which also minimized side reactions. The sample was characterized by FTIR and NMR, which confirmed the synthesis of the final product, TP-$COOCF_3$, via direct fluorination converting $CH_3$ of TP-$COOCH_3$ to $CF_3$ of TP-$COOCF_3$ with 95.4% yield.

• Journal of the Korean Dietetic Association
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• v.17 no.4
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• pp.364-377
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• 2011

This study was conducted to provide basic information on toothbrushing habits, snack intake frequency, and current dental caries in elementary school students. A total of 188 students (105 boys and 83 girls) in Changwon city participated in this study. Dental examination was conducted by two dental hygienists in July, 2010. The results were as follows. Exactly 86.2% of students were shown to have dental caries, which includes a sealant and removed teeth due to decay. The average number of teeth with dental caries per student was 3.8. Exactly 60.6% of students were shown to maintain correct toothbrushing habits to prevent dental caries, but only 12.8% brushed their teeth immediately after a meal or snack. Exactly 82.4% percent of participants received toothbrushing education, 47.1% of them received it from an expert, 43.9% received from their parents, and 28.2% used tooth paste with fluorine. Regarding snack intake frequency, ice cream was the most consumed cariogenic food and white milk was the most consumed protective food. The >=7 teeth with dental caries group consumed higher frequency of carbonated beverages intake than the 'no dental caries' group (P<0.05), and the '5~6 teeth with dental caries' group consumed higher frequency of chocolate intake than 'no dental caries' group (P<0.05).

• Journal of Korean society of Dental Hygiene
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• v.1 no.2
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• pp.227-242
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• 2001

The purpose of this study was 10 examine whether or not the dental- health education experiences of elementary school teachers have any influence on their oral-health awareness and attitude. The subjects in this study were 414 selected teachers from Seoul and North Cholla province. The instrument used by Lee Heung-su was modified into self- reporting questionnaire, and the schools where the subjects were working were visited to conduct a survey for 28 days from September 15 to October 13, 2000. For data analysis, SPSS was employed, and chi-squre, t-test and ANOVA were implemented. The findings of this study could be listed as below: 1. 184(44.4%) out of the techers investigated had ever been educated in dental health, and 230 teachers(55.6%) hadn't. 47% replied they hadn't received oral-health education for the lack of education opportunities. 2. In regard to dental-health awareness and attitude. the presence or absence of dental-health education experiences didn't make any difference to their daily toothbrushing frequency(p>0.05). The use of fluorine was significantly different between the groups(p<0.01), as 42.9% of the teachers with dental-health education experiences and 63.9% of the others with no such a experience didn't use that, 45.7% of the former group and 29.1 % of the latter accurately knew how to brush teeth, and the difference between the two was significant (p<0.01). 3. Concerning student-related dental-health awareness and attitude, the dental-health education experiences make 45.7% of the educated group and 31.7% of the uneducated group agreed to the strong need for oral examination, and the gap between the two was significant(p<0.01). 90.8% of the former group gave counsel to students on dental health, and 77.2% of the latter didn't. The gap between the two was significant as well (p<0.01). 77.2% of the educated group and 41.3% of the uneducated group offered frequent dental-health education, and the difference between the two was significant (p<0.01). 4. Their awareness of the fluorine-based toothbrushing project differed significantly by region(p<0.05), as the teachers from North Cholla province recognized it better than those from Seoul. The female teachers provided more education regarding that project, and those who were older or had more teaching experiences were more aggressive in instructing that project(p<0.01). And the married teachers took more forward attitude than the unmarried (p<0.01). By school location, the teachers from Seoul showed more active attitude than those from North Cholla province(p<0.01), and the gap between the two was significant. As to cooperation, those who were older or had more teaching experience were more cooperative, and the married teachers joined forces better than the unmarried. The gap was significant (p<0.01). 5. Concerning the awareness and attitude of the fluorine-based toothbrushing project, the educated teachers took more aggressive attitude, and the difference between the two was significant(p<0.01). The above-mentioned findings suggested that the dental-health awareness and attitude of the elementary school teachers were under a lot of influence of their oral-health education experiences, and there is a need to develop and carry out education programs for teacher.

• Journal of dental hygiene science
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• v.22 no.3
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• pp.156-163
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• 2022

Background: This study attempted to apply resin infiltrant (RI) as a method to maintain the effect of tooth bleaching treatment and compared it with fluoride varnish (FV) or artificial saliva to evaluate the effect. Methods: Sixty healthy lozenge specimens were classified into five groups. Group 1 was the negative control group, and discoloration was induced after artificial saliva treatment of the tooth specimen (G1_S+C). Group 2 was a positive control group, in which pigmentation was induced after bleaching treatment and artificial saliva treatment (G2 _B+S+C). Coloration was induced in group 3 (experimental group 1) after bleaching treatment and artificial saliva treatment, followed by application of fluorine varnish (G3_B+FV+S+C). Coloration was induced in Group 4 (experimental group 2) after applying RI after bleaching treatment and artificial saliva treatment (G4_B+RI+S+C). Pigmentation was induced in group 5 (experimental group 3) after bleaching treatment and artificial saliva treatment, followed by acid treatment (etching) and treatment with RI (G5_B+E+RI+S+C). Coffee and wine were used to induce discoloration. The lightness value (L^*) of the CIE L^*a^*b^* color system was obtained by image analysis. Kruskal-Wallis H analysis was performed for the mean difference in L^* values by group. Results: When coloration was induced with coffee, there was no significant difference in L^* value between artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups. There was no significant difference in L^* values between the artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups, even in the case of wine induced coloration. Conclusion: It was confirmed that artificial saliva or RI treatment had similar effects to the FV previously used to maintain the effect of tooth bleaching treatment.

• 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.

• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.20-24
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• 2009

YBCO coated conductors (CC) on the $CeO_2$-buffered IBAD-MgO template were fabricated by metal-organic deposition (MOD) Process with Ba-trifluoroacetate and fluorine-free Y and Cu precursor materials. The precursor solution was coated on $CeO_2$-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to $400^{\circ}C$ within 3 h, and finally fired at $740{\sim}800^{\circ}C$ in a reduced oxygen atmosphere. Microstructure, texture, and superconducting properties of YBCO films were found highly sensitive to both the firing temperature and time. The high critical current density ($J_C$) of $1.15\;MA/cm^2$ at 77.3K in the self-field could be obtained from $1\;{\mu}m$ thick YBCO CC, fired at $740^{\circ}C$ for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of $J_C$ values is expected by improving the in-plane texture of $CeO_2$-buffer layer and avoiding the metal substrate contamination.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.7
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• pp.979-985
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• 2001

Two experiments on commercial broiler chickens (3-37 d) and WL layers (252-364 d) were conducted to study the relative bioavailability of phosphorus (P) from different P supplements in comparison to tricalcium phosphate (TCP), at constant dietary calcium (Ca):P ratio. The P sources tested were dicalcium phosphate (DCP), steam sterilized bone meal (SSBM), commercial mineral mixture (CMM), phosphoric acid (PA) and a combination of CMM + PA. Fluorine (F) content in CMM and SSBM was 13.12 and 0.14 g/kg, respectively. In commercial broiler diets, DCP, SSBM or PA could be used as supplemental P sources without affecting (p<0.05) weight gain, feed intake, tibia ash and, P and Ca contents in tibia ash when compared to TCP. Severity of leg abnormality and deposition of F in bone were higher (p<0.05) in group fed CMM. P retention and serum inorganic P content was significantly reduced (p<0.05) in CMM fed birds compared to those fed TCP, SSBM, PA or CMM+PA. Among other P sources (TCP, SSBM, PA and CMM+PA) the serum inorganic P levels did not vary significantly (p<0.05). The P retention also significantly reduced in CMM fed groups compared to those fed DCP or PA. The P retention significantly increased from 0.183 to 0.216 units by supplementation of PA to CMM diet. In layers, egg production was not affected by replacing TCP with DCP, SSBM, PA or CMM+PA, but significantly (p<0.05) reduced with CMM. Feed (kg)/kg egg mass, egg weight, shell quality (shell weight and shell thickness) and serum Ca levels were not influenced by dietary variation in P source. The poor performance of both broilers and layers fed on CMM based diets could be attributed to the presence of hlgher levels of F (647.8 and 630.1 mg/kg, respectively) and low P utilization. Based on growth, bone mineralization and P retention it is concluded that DCP, SSBM or PA can be used as alternatives to TCP in broiler diets. In WL layer diets, in addition to above P sources, CMM can also be used as supplemental P source by replacing one half of P from CMM with PA without affecting egg production and shell quality.

• Polymer(Korea)
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• v.25 no.1
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• pp.33-40
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• 2001

Fluorinated polyurethane elastomers were synthesized by two step polyaddition of a perfluorinated polyether diol(trade name of Fomblin $ZDOL^{\circledR}$) and diisocyanates such as 4,4'-diphenyl methane diisocyanate(MDI) and toluene 2,4-diisocyanate(TDI). In order to control the Fomblin moiety of the soft segment in the synthesized elastomers to 10~50%, polyether type polyols such as polypropylene glycol(PPG) and polytetramethylene glycol(PTMG) were mixed during the polymerization reaction. Ethylene diamine or 1,4-butane diol was used as chain extenders. The structure and average molecular weight of the produced polyurethanes were confirmed by using FT-IR, $^1H-NMR$, DSC, and GPC. The surface properties were analyzed by using X-ray photoelectron spectroscopy(XPS) and contact angle meter. From the results of the surface analysis it was concluded that the fluorine groups were localized on the surface rather than the inside of the polyurethane films.