• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.663-669
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• 2022

The content of fluoride in toothpaste commercially available in Korea has been increased to less than 1500 ppm. The purpose is to provide these results to consumers and to suggest alternatives to the safe use of toothpaste. This study was conducted on 1,300 people for 2 weeks from March 2021. As a research tool, general characteristics and oral health behaviors were surveyed. ConsExpo Web 1.0.2. It was used as an input variable for exposure evaluation. As a result of the study, when a toothpaste containing 1500 ppm of fluoride was used, the external dose on day of exposure was 2.3×10-2 mg/kg/day for males, 2.9×10-2 mg/kg/day for females, and children aged 2-3 years was estimated to be 7.3×10 -2 mg/kg/day. As a result of this study, it is thought that as the fluoride content of toothpaste distributed in the market increases, it will be used as a basic data to present standards for safe use by consumers.

• Journal of Korean society of Dental Hygiene
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• v.10 no.1
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• pp.93-106
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• 2010

Objectives : The study examined mothers' oral health knowledge and oral health management behavior to their children that affect directly children's oral health to prepare basic aiming at children. Methods : Therefore, a survey of 235 mothers in 10 kindergartens located in Seoul was conducted by self-administered questionnaires. Results : As to mothers' oral health knowledge, the correct-answer rate for questions about tooth-decay was highest, and the level of 'middle (5-7 points)' was the most common with 50.0%. Regarding oral health knowledge according to mothers' general characteristics, the higher academic background and family's monthly earnings were, the higher oral health knowledge was. It showed a statistically significant difference(p<.01). In terms of mothers' oral health management behavior to their children, 79.1% of mothers who had the visiting experience in the dentist's for caries prevention was highest. As to the number of brushing, the twice was highest with 51.2%, and regarding brushing time 2min was highest52.6%. Also, the rate of using the fluoride toothpaste was 68.4%, and the rate of mothers who helped their children's brushing was 83.3%. As to the oral health management behavior to their children by mothers' oral health knowledge, mothers with higher oral health knowledge used the fluoride toothpaste showing that there was a significant difference(p<.01). Also, mothers with higher oral health knowledge helped more children's brushing, so that there was a significant difference(p<.05). Regarding the oral health management behavior to their children according to mothers' visiting experience in the dentist's, mothers who visited the dentist's during the recent one year had higher visiting experience of dentist's for children's caries prevention(p<.01) and longer time of brushing by 3min(p<.05), and helped their children's brushing a lot. The findings showed a significant difference(p<.001). Conclusions : As the results above, as mothers' oral health knowledge and oral health management behaviors to their children affect closely children's oral health, more systematic, specific and active oral health programs should be provided to mothers.

• Journal of Korean society of Dental Hygiene
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• v.15 no.1
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• pp.119-127
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• 2015

Objectives: The purpose of the study is to investigate the relationship between dental caries and oral health behaviors in middle and high school students by web-based survey of the ninth(2013) Korean youth risk behavior. Methods: The subjects were 75,149 students from 400 middle schools and 400 high schools. Finally, the survey participation rate was 96.4%(72,435 students from 799 schools) by complex sample design. The questionnaire consisted of general characteristics of the subjects, oral health behaviors, and oral health status. General characteristics included gender, types of schools, economic condition, and residential types. Oral health behaviors included subjective oral health condition, frequency of tooth brushing, tooth brushing after meal within recent 7 days, sealant within 12 months, fluoride application within 12 months, scaling within 12 months, and oral health education experience within 12 months. Oral health condition included dental caries incidence within 12 months. Results: Oral health behavior influenced on dental caries in the middle and high school students in Korea. This study showed the relationship between the sociodemographic characteristics, tooth brushing frequency, sealant experience, dental caries and halitosis experience, and scaling within 12 months. Scaling is the best prevention method for dental caries and halitosis in the students. Conclusions: The study showed the necessity for practical oral health education and the effect of fluoride application for dental caries prevention.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.7-8
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• 2003

Since PVDF/poly(1,4-butylene adipate) blend shows much lower LCST curve compared with PVDF/PMMA blend, the PVDF/PBA blend can be a good candidate for investigating the effect of the electric field on the phase separation and dissolution behavior of an electro-active polymer and electro-inactive polymer blend. (omitted)

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.14-20
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• 2015

A Large Eddy Simulation(LES) was performed for the prediction of unsteady dispersion behavior of hydrogen fluoride (HF). The HF leakage accident occurred at the Gumi fourth industrial complex was numerically investigated using the Fire Dynamics Simulator (FDS) based on the LES. The accident area was modeled three-dimensionally and time-varying boundary conditions for wind were adopted in the simulation for considering the realistic accident conditions. The Message Passing Interface (MPI) parallel computation technique was used to reduce the computational time. As a result, it was found that the present LES simulation could predict the unsteady dispersion features of HF near the accident area effectively. The dispersion behaviors of the leaked HF was much affected by the unsteady wind direction. The LES could predict the time variation of the HF concentration reasonably and give an useful information for the risk analysis while the prediction with the time-averaging concept of HF concentration had a limitation for the amount of HF concentration at specific location point. It was identified that the LES is very useful to predict the dispersion characteristics of hazardous chemicals.

• Macromolecular Research
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• v.17 no.10
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• pp.757-762
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• 2009

The micro domain structures and crystallization behavior of the binary blends of poly(methyl methacrylate)-b-poly(pentafluorostyrene)-b-poly(methyl methacrylate) (PMMA-PPFS-PMMA) triblock copolymer with a low molecular weight poly(vinylidene fluoride) (PVDF) were investigated by small-angle X-ray scattering (SAXS), small-angle light scattering (SALS), transmission electron microscopy (TEM), optical microscopy, and differential scanning calorimetry (DSC). A symmetric, PMMA-PPFS-PMMA triblock copolymer with a PPFS weight fraction of 33% was blended with PVDF in N,N-dimethylacetamide (DMAc). In the wide range of PVDF concentration between 10.0 and 30.0 wt%, PVDF was completely incorporated within the PMMA micro domains of PMMA-PPFS-PMMA without further phase separation on a micrometer scale. The addition of PVDF altered the phase morphology of PMMA-PPFS-PMMA from well-defined lamellar to disordered. The crystallization of PVDF significantly disturbed the domain structure of PMMA-PPFS-PMMA in the blends, resulting in a poorly-ordered morphology. PVDF displayed unique crystallization behavior as a result of the space constraints imposed by the domain structure of PMMA-PPFS-PMMA. The pre-existing microdomain structures restricted the lamellar orientation and favored a random arrangement of lamellar crystallites.

• Polymer(Korea)
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• v.28 no.6
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• pp.509-518
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• 2004

Microdomain structures and crystallization behavior of the binary blends consisting of an asymmetric block copolymer and a homopolymer were investigated using small-angle X-ray scattering (SAXS), optical micro scope (OM) and differential scanning calorimetry (DSC). Poly(methyl methacrylate)-block-polystyrene block copolymer (PMMA-b-PS) (weight fraction of PMMA =0.53) was mixed with low molecular weight poly(vinylidene fluoride) (PVDF). As the PVDF concentration was increased, the morphological change from a lamellar to a cylindrical structure occurred. The crystallization of PVDF significantly disturbed the orientation of the pre-existing microdomain structure, resulting in a poorly ordered morphology. In the blends, PVDF exhibited unique crystallization behavior due to the PMMA block which is preferentially miscible to PVDF and the space constraint imposed by the microdomains.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.280-285
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• 2016

In this study, we investigated the influences of potassium fluoride(KF) addition on the surface characteristics of plasma electrolytic oxidation(PEO) coating produced on Al alloy. The PEO of marine grade Al alloy(5083 grade) was conducted in KOH 1g/L solution adding different concentrations of KF(0, 1 and 2 g/L) under a galvanostatic regime. With KF addition, unusual behavior was observed on the voltage-time characteristic curves, which can be characterized by the following process: (i) initial rapid increase in voltage (ii) a short plateau after 1st breakdown (iii) gradual increase in voltage (iv) intermittent fluctuation of voltage after 2nd breakdown. The SEM observation revealed irregular surface morphology with KF addition, as compared with one formed without KF addition, which had a reticulate structure. The XRD analysis detected the formation of aluminium hydroxide fluoride hydrate($H_{4.76}Al_2F_{3.24}O_{3.76}$) on surface grown by PEO process with KF. Particularly, at very early stage of the process (~ 120 s), thin film was formed having nanoporous structure, and F element was confirmed on surface by EDS analysis. The thickness and surface roughness of the coating increased with increasing KF concentration. As a result, KF addition was found to be less beneficial influences on PEO of marine grade Al alloy, and therefore needs further research to improve its capability.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.483-489
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• 2006

The behavior of rare earth compounds such as $La_{2}O_{3}$, $CeO_{2}$, and $Ca(OH)_{2}$ on the removal of fluoride and heavy metals in the steel wastewater has been investigated. The removal mechanism of fluoride by rare earth elements has been known to be the formation of insoluble compounds between $F^{-}$ and cations such as $La^{3+}$ and $Ce^{4+}$ produced by the dissociation of rare earth compounds (To reduce the running cost of the fluoride wastewater treatment facility, their fluoride removal efficiencies were compared with those of inexpensive rare earth minerals such as natural lanthanide and cerium compound used as a glass polishing agent). All of the rare earth oxides used in this study showed a higher removal efficiency of fluoride than $Ca(OH)_{2}$ in the wastewater. In the case of artificial HF solution, the removal efficiency of fluoride showed in the order: $CeO_{2}$-mineral < $CeO_{2}$ < $Ca(OH)_{2}$ < $La_{2}O_{3}$-mineral < $La_{2}O_{3}$. However, the removal efficiency of fluoride in the wastewater increased in the following order: $Ca(OH)_{2}$ < $CeO_{2}$ mineral < $CeO_{2}$ < $La_{2}O_{3}$ mineral < $La_{2}O_{3}$. All agents showed high efficiencies for the removal of Mn and total Cr in the rare earth compounds. In the case of $Ca(OH)_{2}$, fluoride removal decreased with increasing pH while. However, the rare earth compounds showed a higher fluoride removal in higher pH condition, the optimum pH condition seemed to be around 7 considering both water quality and fluoride removal. Under the pH 7 condition, the $Ca(OH)_{2}$ was superior to rare earth compounds in Mn removal and the lanthanide was superior to others in total Cr removal.

• Journal of Korean society of Dental Hygiene
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• v.15 no.6
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• pp.999-1007
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• 2015

Objectives: The objective of the study is to investigate oral health behavior and oral health education experience in Korean adolescents from the ninth(2013) web-based survey of Korean youth risk behavior. Methods: The subjects were 72,435 students through the ninth 2013 web-based survey of Korean youth risk behavior conducted by the Ministry of Education, Science, and Technology, the Ministry of Health and Welfare, and the Korea Centers for Disease Control. The questionnaire consisted of socio-demographical characteristics of the subjects, oral health behavior, and oral health education experience. Data were analyzed by SPSS 18.0 program. Results: Oral health education had much influence on tooth brushing after lunch, oral cavity disease prevention, sealants, fluoride application, scaling experience, and consumption of vegetables, milk, carbonated soft drinks, noodles, and snacks. The oral health education had a great impact on those who took good oral health behavior into action. Conclusions: It is very important and necessary to develop the continuing effective oral health education program for the adolescents and make them tale into action.