• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.57-63
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• 2016

Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure.

• Composites Research
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• v.15 no.5
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• pp.7-13
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• 2002

The piezoelectric thin film sensor has good characteristics to observe the impact responses of composite structures. The capabilities for monitoring impact behavior of Gr/Ep laminates subjected to damage-induced impact using the PVDF(polyvinylidene fluoride) film sensor were examined. For a series of low-velocity impact tests from low energy to damage-induced energy, simulated sensor signals were compared with measured signals and the PVDF film sensor. Local impact damages(matrix cracking and delamination) were found at three impact tests, but the measured signals agreed well with the simulated sensor signals based on the linear relationship between the impact forces and the PVDF film sensor signals. And the inverse technique was applied to reconstruct the impact forces using the PVDF film sensor signals. Most of reconstructed impact forces had good agreement with the measured forces. The comparison results showed that the local damage due. to low-velocity impact didn't disturb the global impact responses of composite laminates and the reconstruction of impact forces from PVDF sensor signals wasn't affected by the local damage.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.241-255
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• 2016

In this study, the treatability of arsenic (As) contaminated water by direct contact membrane distillation (DCMD) at different delta temperatures (${\Delta}T$) 30, 40 and $50^{\circ}C$ has been investigated. Two different pore sizes ($0.22{\mu}m$ and $0.45{\mu}m$) of hydrophobic membranes made of polyvinylidene fluoride (PVDF) were used. The membrane pore sizes, the operating temperatures, the feed solution As concentration and conductivity have been varied during the experimental tests to follow the removal efficiency and flux behavior. Both membranes tested had high removal efficiency of arsenite (As (III)) and arsenate (As (V)) and all permeates presented As concentration far lower than recommended $10{\mu}g/L$ of world health organization (WHO). As concentration was below detection limit in many permeates. Conductivity reduction efficiency was over 99% and the transmembrane flux (TMF) reached $19L/m^2.h$ at delta temperature (${\Delta}T$) of $50^{\circ}C$ with PVDF $0.45{\mu}m$ membrane. The experimental results also indicated that $0.45{\mu}m$ pore sizes PVDF membranes presented higher flux than $0.22{\mu}m$ pore sizes membranes. Regardless of all operating conditions, highest fluxes were observed at highest ${\Delta}T$ ($50^{\circ}C$).

• Journal of dental hygiene science
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• v.3 no.1
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• pp.45-50
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• 2003

In order to develop the program of oral hygiene education for elementary school senior-students, a questionnaire survey of elementary fourth, fifth and sixth students who are under continual control program of oral hygiene. (1) For tooth brushing time, after dinner is more than before. 73.7% of respondents brushed the teeth twice or more a day. (2) 62.1% of respondents took the cariogenic food twice or more a day. (3) 90.1% of respondents had visited a dental clinic. (4) Concerning fear for dental treatment, only 14.4% had a feeling of fear. (5) Regarding the experience with a preventive treatment, 39.7% had an experience with pit and fissure sealing, and 24.2% had an experience with the application of fluorides. (6) 46.2% of respondents had a preference for the fluoride mouth rinsing program, and 38.4% wanted that program to keep going on. As to the reason to favor the fluoride mouth rinsing program, 38.2% preferred it because of prevention of dental caries, and 43.0%, the largest percentage, didn't favor it because they found it too much trouble to do. (7) Comparing with the research result in 2000, we proved positively the educational effect of brushing frequency, positive understanding and preference to water school fluoridation program, and got the negative data of experience of visiting to oral clinic and preventive treatment.

• Journal of Korean society of Dental Hygiene
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• v.6 no.1
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• pp.49-61
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• 2006

This study was intended to identify the pregnant women's oral health care behaviors and the necessity of active oral care so as to use in the dental hygiene education at dental clinics as basic materials to inform the importance of oral health during pregnancy and instruct how to improve it. And to suggest a dental service direction for dental hygienists, 150 pregnant women who visited the Ostetrics and Genecology Clinics located in tl,e north part of Cholla province were surveyed with questionnaire on their oral care behaviors, from september to October in 2004. The findings were as below: 1. 43.8% of the pregnant women have ever used the dental care institutes within the recent 3 months during pregnancy period. The purpose of the visits was mostly treatment of dental caries, accounting for 40.0%. Next came the treatment of periodontal diseases, accounting for 33.8%. 2. At dental care service, 84.7% of the pregnant women informed the clinic staff of their pregnancy, 12.0% of the pregnant women were having periodical oral examination. 3. 56.7% of the pregnant women have ever inquired about oral care methods, 24.0% of the pregnant women have ever taken any oral health education, of whom 47.1% had higher schooling over graduate school, with a statistically signifiant difference. 4. 55.3% of the pregnant women made changes in their oral care practice after they got pregnant. Change of oral care practices was more obvious in those who had higher schooling background, of whom specialist women accounted 76.9%. Change of oral care practices after pregnancy was statistically significantly different to the academic background and occupation. 5. Of the changes in oral care practice after pregnancy, 51.8% of the pregnant women answered they got sensitive to change in their oral status, and 39.8% increased the frequency of tooth brushing. 6. In selecting a tooth paste after they got pregnant, 58.0% of the women didn't give any special consideration to the kind of tooth paste, while 10.7% women as low selected such tooth pastes that contain fluoride. 7. Pregnant women's route for gathering oral care information was mostly mass media and Internet which accounted for 50.7%.

• Journal of Korean society of Dental Hygiene
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• v.12 no.6
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• pp.1119-1127
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• 2012

Objectives : The aim of this study was to examine the level of oral health knowledge, oral health importance, oral health status and oral health interest of the social workers engaged in child care facilities to analyze the influential factors on oral health promotion activities and provide the basic data for oral health promotion activities. Methods : The subjects in this study were those social workers engaged in child care facilities from May 15th to May 25th in 2011. The self-report questionnaires were distributed and withdrawn and then a total of 205 papers from the subjects that participated in this study were analyzed for the final analysis. Results : 1. Oral health knowledge had $12.16{\pm}1.66$ in a full score of 15 and oral health importance, oral health status and oral health interest were $1.12{\pm}0.36$, $2.80{\pm}0.50$ and $2.14{\pm}0.8$ respectively in a full score of 5. 2. According to the general characteristics, the difference analysis of cognition-recognition factors showed that singles had significantly higher oral health knowledge married couples (p<0.05) and the social workers unusing auxiliary oral hygiene devices had significantly higher oral health interest than those using them(p<0.01). 3. The mean of oral health promotion was $3.28{\pm}0.51$, characteristics of detailed specific-area were as follows ; the toothbrushing was $3.77{\pm}0.57$, the use of fluoride was $2.67{\pm}0.98$, periodic dental screening and treatment were $2.98{\pm}1.09$ and eating habits was $4.14{\pm}0.57$. These results generally showed tooth-brushing and eating habits show a little higher figures. 4. Considering the factors oral health promotion behaviors of social workers engaged in child care facilities, the higher oral health interest was, the higher oral health promotion behavior was. Conclusions : It seems that social workers engaged in child care facilities are required to pay attention to the importance of oral health and learn oral health knowledge, which will lead to much better improvement of oral health for children brought up by them.

• Journal of dental hygiene science
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• v.8 no.4
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• pp.375-380
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• 2008

This study evaluated the effect of an school-based oral health program supplied to primary school children in Anyang city. This program included oral health education, pit and fissure sealing, fluoride mouth rinsing and professional tooth brushing. The numbers of the subjects were 311 children in the program participant group and 165 children in the control group which were not in the program. Data were analyzed with t-test, one way ANOVA and pearson's correlation coefficient using SPSS WIN 12.0 program. In attitude, behavior of oral hygiene, participant group was better than the control group. In case of the perceived oral health, satisfaction of oral health, need oral treatment there was no significant difference between the two groups. These results suggest that school children can learn the good attitude and behaviors and oral health promotion can be achived from the oral health program run by shool dental clinic.

• Journal of dental hygiene science
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• v.12 no.4
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• pp.359-367
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• 2012

This study was to evaluate the influence of dental caries prevention-related concerned and perceived in Korean adults and oral health behavior of their first child if they had children. A cross-sectional study in 1,014 adults over 19 years old were conducted in Korean adults, asked to answer a computer-assisted telephone interview regarding their oral health-related knowledge, behavior, concerned of caries prevention and child's behaviors such as frequencies of tooth brushing, chewing the xylitol gum and dental checkup. The statistical analysis was done by using the SPSS 19.0 program (IBM Co., Armonk, NY, USA). Awareness of caries prevention in the female than male, 40~49 years old age group was higher. Parents of school-age children were higher level of awareness of the dental caries prevention than other group. As knowledge and behavior of dental caries prevention were higher, the child's conduct regular oral health checkups, fluoride topical application and dental sealant was significantly higher. The higher the concerned of caries preventive, the intention of oral health behaviors and child's oral health behaviors was more increased. Awareness of caries prevention had effect on the perception of the impact of the child's oral health behaviors.

• Journal of dental hygiene science
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• v.5 no.4
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• pp.171-177
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• 2005

This study aims to analyze effects of mothers' socioeconomic features, and knowledge and behavior of oral health on experience and purpose of using dentistry. By survey to 103 mothers of 5-6 year old children, who use day care centers in seoul, the results are obtained as follows: 1. As for the rate of experiencing dental care classified by its purpose, 56.7% for dental treatment, 23.3% for regular check-up and 20.0% for precaution 2. There was no significant difference of correlativity between mothers' socioeconomic features and knowledge of oral health and experience of using dental care, while the lower rate of using dental floss, the higher rate of experiencing dental care(p < 0.01). 3. In respect of correlativity between mother's socioeconomic features and purpose of using dental care, the purpose of regular checkup was high in a group of mothers between 33 and 35 years old(71.4%) by ages and in a group of mothers who graduated from college(57.1%) by academic background(p < 0.05). 4. In correlativity between mothers' behavior of oral health and purpose of using dental care, the result showed that the higher the rate of using dental floss was, the higher the rate of experiencing dental care for a regular check-up was(p < 0.001) and the higher the rate of using fluoride dentifrices was, the higher the rate of using dental care for cure was(p < 0.05). 5. Multiple regression based on dependent variable of experience in using dental care showed that average monthly income(less than 2,500,000 won) was significant explanatory factor with 65% of explanatory variance. On the other hand, multiple regression based on dependent variable of purpose of using dental care showed that vocation(professional job) and age(between 33 and 35 years old) was significant explanatory factor with 70% of explanatory variance for a regular check-up, age(between 33 and 35 years old) and average monthly income (less than 2,500,000 won) was significant factor with 78% of explanatory variance for precaution and age(less than 32 years old) was significant explanatory factor with 33% of explanatory variance for treatment.

• Journal of dental hygiene science
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• v.8 no.3
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• pp.147-153
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• 2008

The purpose of this study was to attempt to lay the foundation for the development of oral health programs geared toward promoting the oral health of low socioeconomic class children. The subjects in this study were 257 school children who used local children's centers. The findings of the study were as follows: 1. The children mean scored 5.74 on oral health knowledge. 2. In terms of oral health awareness, 47.1% viewed the right toothbrushing as the best way to stay away from dental caries. 3. 45% of the subjects reported toothbrushing at least three times daily. 21.4% visited dental institutions three or more times in the past year. 33.1% had never undergone application of fluoride. 30.4% had never received oral health education. 4. The mean level of caries was 4.61 dft index in 1-2th grade, 3.27 DMFT index in 5-6th grade, 1.47 DMFT index in the 3-4th grad and 1.19 DMFT index in the 1-2th grade. 5. The mean level of Patient Hygiene Performance (PHP index) was 3.59, and there was no significant association was pound between PHP index and grade. 6. Oral health behavior wasn't affected by their oral health awareness, and knowledge.