• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.114-122
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• 2016

Concrete is cost-benefit and high-durable construction material, however durability problem can be caused due to steel corrosion under chloride attack. Recently deicing salt has been widely spread in snowing season, which accelerates micro-cracks and scaling in surface concrete and the melted deicing salt causes corrosion in embedded steel. The previous governing equation of Fick's 2nd Law cannot evaluate the deteriorated surface concrete so that another technique is needed for the surface effect. This paper presents chloride penetration analysis technique for concrete subjected to deicing salt utilizing multi-layer diffusion model and time-dependent diffusion behavior. For the work, field investigation results of concrete pavement exposed deicing salt for 18 years are adopted. Through reverse analysis, deteriorated depth and increased diffusion coefficient in the depth are evaluated, which shows 12.5~15.0mm of deteriorated depth and increased diffusion coefficient by 2.0 times. The proposed technique can be effectively applied to concrete with two different diffusion coefficients considering enhanced or deteriorated surface conditions.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.319-324
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• 2020

Electroconvective instability is a non-linear transport phenomenon which can be found in ion-selective transport system such as electrodialysis, Galvanic cell and electrolytic cell. The instability is triggered by the fluctuation of space charge layer in adjacent of ion-selective surface, leading to increase of mass transport rate. Thus, in the aspect of mass transport, the instability has an important meaning. Although recent experimental techniques have opened up an avenue to direct visualize the instability, fundamental investigations have been conducted in limited area due to several experimental limitations. In this work, the electroconvective instability under potentiostatic mode was solved by numerical method in order to demonstrate correlation between current-time curve and the instability behavior. By rigorous time-resolved analysis, the transition behaviors can be divided into three stages; formation of space charge layer - growth of electroconvective instability - steady state. Furthermore, scaling laws of transition time were numerically obtained according to applied voltage as well.

• Journal of Korean society of Dental Hygiene
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• v.11 no.5
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• pp.695-706
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• 2011

Objectives : The purpose of this study is to assess oral health perception, oral health behavioral and family smoking status according to smoking experience in a part of high school students. Methods : A survey is conducted with a total of 648 first grader at high school in Dae-Gu city from 1st to 30th September, 2009. The results are as follows. Results : 1. 95.5% of respondents are 'smoking is very harmful for health' and the majority of smoking-related disease are lung cancer, oral disease, and oral cancer. 2. 127 respondents have experience in smoking and 62 respondents are smoking at that time. 59.7% respondents have 1 year smoking history and the majority of respondent are 5 cigarettes/day. 67.8% respondents are under 5 cigarettes/day. 3. In oral health behavioral by smoking, the majority of smokers' teeth brushing are 3 times, 47.2% and 2 times, 27.6%. The majority of nonsmoker's teeth brushing are 3 times, 47.0% and 2 times 26.5%. The results of teeth brushing time are significantly different between smokers and non-smokers(p<.001). The majority of smokers and non-smokers have not experienced about scaling. It is significantly different between 2 groups(p<.05). 4. The smoking rate of father and grandfather in smokers is higher than non-smokers. It is significantly different between 2 groups(p<.005). 5. The need for oral management in oral health education is gum treatment and dental caries treatment. 22.8% smokers and 25.7% non-smokers require to get gum treatment. 18.1% smokers and 20.2% non-smokers required to get dental caries treatment. Conclusions : Also Future longitudinal research is required to develop oral health promotion program contents according smoking-oral health.

• Journal of Korean society of Dental Hygiene
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• v.10 no.6
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• pp.965-972
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• 2010

Objectives : This study was conducted to improve oral heath behaviour of child by analyzing child's mother oral health behaviour. Methods : A total of 361(95.0%) 3-year-old-child's mothers who sent their child to child care institution in Daegu were analyzed from October 1, 2009 to October 31, 2009. Results : 1. In relation to general nature and experience on oral health education of child's mother, mother with higher monthly income, over than graduation from university and professional job had high oral health education experience, which was statistically related(p<0.01)(p<0.001). 2. In the case of mother with oral health education experience, this mother had higher dental clinic visit for 1 year, higher experience on scaling, higher good food preference for teeth health and higher use of floss, which was statistically related(p<0.05)(p<0.01). 3. Regarding child's oral management behaviour by mother's oral health importance, in the case that oral health was important, flouride toothpaste use, restriction on cavity inducting food and toothbrushing before sleep were higher only, which was statistically related(p<0.05)(p<0.001). Conclusion : In case of mother with oral health education experience, this mother had experience on dental clinic visit for prevention of cavity, dental clinic visit for treatment and restriction on food in which their child's oral health behaviour were satisfactory, which was statistically related.

• Journal of Korean society of Dental Hygiene
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• v.14 no.6
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• pp.921-926
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• 2014

Objectives: The purpose of the study is to investigate the factors associated with gingival bleeding(GB) by tooth brushing in college students. Methods: A self-reported questionnaire was filled out by 232 college students in Daegu Health College from March to June, 2014. Data were analyzed for frequency, chi square test, and logistic regression analysis using SPSS 12.0 program. The study was a cross sectional study. The questionnaire consisted of general characteristics of the subjects(gender, age, marital status, and smoking), frequency and duration of tooth brushing, scaling experience, and physical health status. Self-reporting hemorrhage was reported by yes or no. Frequency of tooth brushing was documented as the number of behavior. Above 4 times of tooth brushing was defined as 4. Duration of tooth brushing was documented as minute. Above 4 minutes, it was recorded as 4. In physical health status, 1 is feeling weak and 4 is feeling very healthy. Cronbach alpha was 0.82 in the study. Results: There were significant relationships between gingival bleeding and age(p<0.05), subjective health(p<0.01), tooth brushing frequency(p<0.05) and duration(p<0.05) by chi square test. Logistic regression analysis showed that the age(p<0.05), subjective health(p<0.01), tooth brushing frequency(p<0.05) and duration(p<0.05) were associated with gingival bleeding. Prevalence of gingival bleeding in 20 years was 0.62(odds ratio 1.85, 95% CI 1.00~3.43) and it was higher than that in 10 years. Prevalence of gingival bleeding in good health group was -1.38 and it was lower than that in poor health group. Conclusions: The factors associated with gingival bleeding were age, subjective health, and tooth brushing frequency and time.

• Journal of Korean society of Dental Hygiene
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• v.15 no.1
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• pp.111-118
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• 2015

Objectives: The aim of the study is to investigate the health belief model affecting the oral health behavior in middle and high school students. Methods: The subjects were 296 middle and high school students in Seoul, Gyeonggi and Incheon from February 15 to March 21, 2014. The students filled out the self-reported questionnaires after receiving informed consents. The instrument was adopted and revised from those of Kim & Hwang, and Choi & Joo. The questionnaire consisted of 4 questions of general characteristics, 9 questions of oral health status including subjective oral health status, frequency of tooth brushing, duration of tooth brushing, method of tooth brushing, use of oral health devices, dental clinic visit, scaling services, snack intake, and smoking. The oral health belief consisted of 25 questions including susceptibility, seriousness, barriers, benefit, and self-efficacy using Likert 5 scale. The reliability of Cronbach's alpha in the study was 0.725. Data were analyzed using SPSS ver 18.0 for frequency analysis, t-test, ANOVA, ${\chi}^2$-test, and Pearson's correlation coefficient, simple regression, and binary logistic regression. Results: Oral health beliefs of middle and high school students affected the oral health behaviors. Susceptibility, barriers and self-efficacy also influenced on the oral health behaviors. In order to provide the best oral health education, susceptibility and self-efficacy are the primary factors to increase motivation because the motivation endows the students with correction of oral health behaviors that improve the knowledge, attitudes, and decrease barriers in oral hygiene. Conclusions: It is important to correct oral health behaviors in the middle and high school students by providing the continuing and systematic oral health education.

• Journal of IKEEE
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• v.15 no.4
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• pp.305-312
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• 2011

A primary interest of this work is to develop an efficient and powerful repetitive pulser system for the application of ultra wide band generation. The important component of the pulser system is a small-sized coaxial type spark gap with planar electrodes filled with SF6 gas. A repetitive switching action by the coaxial spark gap generates two consecutive pulses in less than a microsecond with rise times of a few hundred picoseconds (ps). A set of several parameters for the repetitive switching of the spark gap is required to be optimized in charging and discharging systems of the pulser. The parameters in the charging system include a circuit scheme, circuit elements, the applied voltage and current ratings from power supplies. The parameters in the discharging system include the spark gap geometry, electrode gap distance, gas type, gas pressure and the load. The characteristics of the spark gap discharge, such as breakdown voltage, output current pulse and recovery rate are too dynamic to control by switching continuously at a high pulse repetition rate (PRR). This leads to a low charging efficiency of the spark gap system. The breakthrough of the low charging efficiency is achieved by a parallel operation of two spark gaps system. The operational behavior of the two spark gaps system is presented in this paper. The work has focused on improvement of the charging efficiency by scaling the PRR of each spark gap in the two spark gaps system.

• Journal of Korean society of Dental Hygiene
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• v.17 no.5
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• pp.757-767
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• 2017

Objectives: The purpose of this study is to identify the associated factors with subjective oral symptoms experience of obesity adolescents. Methods: The study subjects were targeting 8,139 obesity adolescents and 55,601 non-Obesity adolescents who completed 2016 Korean Youth Risk Behavior Web-based survey. Dependent variables were subjective oral symptoms experiences of fracture teeth, pain, throbbing pain, periodontal pain & bleeding, mucosal disease and bad breath. Independent variables were demographic characteristics of the subjects, oral health behaviors, health behaviors and eating habits. Results: Obesity adolescents were 12.8% with 61.9% subjective oral symptoms experience. Regarding the related factors of subjective oral symptoms experience of obesity adolescents, the factors were identified to be significantly higher in high school (OR=1.72) compared to middle school, learning achievement was higher in middle (OR=1.09) and lower (OR=1.31) compared to high, economic status was higher in lower (OR=1.09) compared to high, sealant experience (OR=1.10) and scaling experiences (OR=1.12) responded no were higher compared to responded yes, smoking experiences responded yes(OR=1.08) were higher compared to responded no, sweet drink (OR=1.14) and fastfood (OR=1.13) consumption were higher in consumption compared to non-consumption and females (OR=0.46) were higher than males. Oral symptoms experience were lower that father and mother's level of education were under high school graduation (OR=0.86) compared to unknown, economic status was in case of middle (OR=0.93) compared to high, tooth brushing was lower in under 1 time (OR=0.76), 2 times (OR=0.61) compared to more than 3 times, vigorous physical activities responded no (OR=0.75) were lower, compared to yes, vegetable consumption was lower in non-consumption (OR=0.68) compared to consumption. Conclusions: Subjective oral symptoms experiences were identified higher in obesity adolescents than non-obesity adolescents. It would be useful to use the results of this study to reduce oral symptoms and necessary to develop a program system considering characteristics of obesity adolescents.

• Earthquakes and Structures
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• v.24 no.4
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• pp.289-301
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• 2023

Developing a competent soil-bridge interaction model for the seismic analysis of piled foundation bridges is of utmost importance for investigating the seismic response and assessing fragility of these lifeline structures. To this end, ground motion histories are deemed necessary at various depths along the piles supporting the bridge. This may be effectively accomplished through time history analysis of a free-field standalone soil column extending from bedrock level to ground surface subjected to an input bedrock motion at its base. A one-dimensional site/ground response analysis (vide one-directional shear wave propagation through the soil column) is hence conducted in the present research accounting for the nonlinear hysteretic behavior of the soil stratum encompassing the bridge piled foundation. Two homogeneous soil profiles atop of bedrock have been considered for comparison purposes, namely, loose and dense sand. Analysis of the standalone soil column has been performed under a set of ten selected actual bedrock ground motions adopting a nonlinear time domain approach in an incremental dynamic analysis framework. Amplified retrieved PGA and maximum soil shear strains have been generally observed at various depths of the soil column when moving away from bedrock towards ground surface especially at large hazards associated with high (input) PGA values assigned at bedrock. This has been accompanied, however, by some attenuation of the amplified PGA values at shallower depths and at ground surface especially for the loose sand soil and particularly for cases with higher seismic hazards associated with large scaling factors of bedrock records.

• Journal of dental hygiene science
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• v.11 no.6
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• pp.513-520
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• 2011

The purpose of this study was to examine elderly people's oral health behaviors and education needs. The subjects in this study were 195 senior citizens who were users of senior cultural centers and senior welfare agencies in Seoul and Incheon. After a survey was conducted, the collected data were analyzed by the statistical package SPSSWIN 19.0. The findings of the study were as follows: 1. Gender, academic credential and monthly mean income were identified as the general characteristics to impact on their oral health attitude. 2. The senior citizens who ever received oral health education had a better knowledge(p<0.05) and took a better attitude(p<0.01). 3. As for a time for toothbrushing, many brushed their teeth after breakfast(74.9%) and dinner(71.8%). Utilized Oral hygiene devices were interdental brushes(21.5%), dental floss(13.8%). As many as 62.5% felt they had a dry mouth, and the most prevalent way for them to cope with it was drinking water often(68.2%). 79.5% didn't get their teeth cleaned on a regular scaling. 4. The rate of regular scaling was higher in the elderly groups that ever received oral health education and whose knowledge scores was above the average(p<0.05). 5. In relation to the necessity of oral health education, 87.2% felt the need for that, and as many as 79.0% intended to receive that education. Their favorite period of education was 6months(41.0%), and the greatest group hoped to receive that education for an hour(55.4%). The largest group wanted to learn about prevention of oral diseases, followed by toothbrushing, denture management, dry mouth. Given the findings of the study, senior welfare centers and senior cultural centers should offer oral health education programs as part of lifelong education to provide systematic and prolonged education for the elderly to improve their oral health care to promote their oral health.