• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.103-115
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• 2000

The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.

• 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 the Korean earth science society
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• v.38 no.7
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• pp.511-521
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• 2017

This study analyzes Two-dimensional video disdrometer (2DVD) data while summer 2011-2012 in Daegu region and compares with Marshall and Palmer (MP) distribution to find out statistical characteristics and characteristics variability about drop size distribution (DSD) of Daegu region. As the characterize DSD of Daegu region, this study uses single moment parameters such as rainfall intensity (R), reflectivity factor (Z) and double moment parameters such as generalized characteristics number concentration ($N{_0}^{\prime}$) and generalized characteristics diameter ($D{_m}^{\prime}$). Also, this study makes an assumption that DSD function can be expressed as general gamma distribution. The results of analysis show that DSD of Daegu region has ${\log}_{10}N{_0}^{\prime}=2.37$, $D{_m}^{\prime}=1.04mm$, and c =2.37, ${\mu}=0.39$ on average. When the assumption of MP distribution is used, these figures then end up with the different characteristics; ${\log}_{10}N{_0}^{\prime}=2.27$, $D{_m}^{\prime}=0.9mm$, c =1, ${\mu}=1$ on average. The differences indicate liquid water content (LWC) of Daegu distribution is generally larger than MP distribution at equal Z. Second, DSD shape of Daegu distribution is concave upward. Other important facts are the characteristics of Daegu distribution change when Z changes. DSD shape of Daegu region changes concave downward (c =2.05~2.55, ${\mu}=0.33{\sim}0.77$) to cubic function-like shape (c =3.0, ${\mu}=-0.13{\sim}-0.33$) at Z > 45 dBZ. 35 dBZ ${\leq}$ Z > 45 dBZ group of Daegu distribution has characteristics similar to maritime cluster of diverse climate DSD study. However, Z > 45 dBZ group of Daegu distribution has a difference from the cluster.

• Journal of dental hygiene science
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• v.9 no.1
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• pp.115-120
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• 2009

The purpose of this study was to utilize it as a basic data for local self-government in each region to plan and perform the oral health program targeting children and mothers as guardian. Data had been obtained by using children's oral examination and mothers' self-reported questionnaire method from June 1 to June 30 in 2007 targeting kindergartens where are located in the region of Hwaseong city. The survey was conducted targeting totally 239 people. Its results are as follows. 1. The healthy-tooth rate in the whole children accounted for 79.12%, thus girls were indicated to be a little higher with 80.36% than boys with 78.13%. Carious-tooth rate showed 8.74% for boys and 6.07% for girls. The dental-caries experience treatment rate showed 11.37% for boys and 12.59% for girls. 2. The index of children at age 5, df rate was 39.3% in the whole, thereby having been indicated that boys with 41.3% are higher than girls with 37.2%. Even dft index is showing the higher index in boys with 3.9 than girls with 3.2. 3. As a result of examining mothers' oral-health behavior, mothers with out employment thought the self oral-health state to be good(p = 0.002). In appearance of scaling experience or of periodic dental checkup, a slight difference is being shown according to general characteristics, but wasn't significant. 4. As a result of examining children's oral management, it was indicated that the higher economic level(p = 0.011) and the more in mothers without employment lead to giving a light meal less(p = 0.41). In appearance of children's periodic dental checkup, the higher academic background level(p = 0.047) and the more employment(p = 0.044) led to receiving dental examination.

• Journal of agricultural medicine and community health
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• v.28 no.2
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• pp.31-48
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• 2003

Objectives: This study evaluated the status of Health-related Behavior in residents from rural areas. A self-administered questionnaire was given to 1,754 people (men; 633 persons, women; 1,121 persons) in rural areas aged over 30 years and under 80 years in Buk-myeon, Uljin-gun and Gigye-myeon, Pohang-si, Gyeongsangbuk-do in 2001 and 2002. Methods: The collected data was analyzed using a chi-square test after an age-adjusted and a chi-square trend test. The data was analyzed using a SPSS/win ver. 10.0. Results: The age-adjusted prevalence of the individual unhealthy behavior according to sex was 56.1% in men and 6.8% in women with regard to smoking; 65.4% and 21.6% with regard to drinking; 72.6% and 76.6% with regard to non-exercise on a regular basis; 23.3% and 28.2 with regard to an obese body mass index; 61.5% and 71.1% with regard to non-scaling in the dental service. The rate of alcohol and tobacco consumption increased with increasing age in both men and women (p<0.01). The age-adjusted proportion in the non-screening examination for stomach cancer according to sex was 49.3% in men and 51.4% in women; 64.0% and 70.7% in liver cancer; 88.9% and 87.5% in colon cancer; 58.3% and 59.1% in undergoing a medical health screening. Conclusions: It is essential for health educators to promote Health-related Behavior in residents in rural areas. In addition, it is expected that the health status of residents in rural areas will improve through efforts to encourage them to take more interest in a healthier lifestyle.

• Journal of dental hygiene science
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• v.8 no.4
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• pp.225-231
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• 2008

The purpose of this study was to examine the relationship between oral health habits and oral diseases in an attempt to raise awareness of the need for prolonged dental checkup projects and lay the foundation for oral health education and sustained oral health care projects. The subjects in this study were 2,643 workers from 76 workplaces in Siwha Industrial Complex in the city of Ansan, Gyeonggi province, who were at the age of 20 and up. The findings of the study were as follows: 1. Concerning the experience of visiting a dental clinic over the past year, 760 male workers (37.4%) and 237 females (38.9%) visited dental clinics in the past year. By age group, those who were in their 50s (54.0%) visited dental clinics the most, and the workers in their 30s (67.9%) paid a visit the least. The gap between the age groups was statistically significant (p < 0.001). 2. In regard to the time for toothbrushing by age group, the workers in their 20s (64.6%) made up the largest group that brushed their teeth before breakfast, and those who were in their 60s and up constituted the greatest group that did toothbrushing after breakfast. The workers in their 20s brushed their teeth the least, as the rates of the workers of this age group who did toothbrushing after breakfast and dinner respectively stood at 64.0 percent and 54.5 percent. The disparities between the age groups were statistically significant (p < 0.001). 3. As for scaling experience for the past year, 302(46.0%) out of the workers who got their teeth scaled in the past year had periodontal diseases, and 1,600(80.6%) out of those who didn't suffered from periodontal diseases. The gap between them was statistically significant (p < 0.001). 4. Regarding the relationship of subjective oral health state to dental caries among the workers without dental caries, the largest group that numbered 327(54.1%) considered themselves to be in good oral health. In the event of the workers with dental caries, the greatest group that numbered 708(75.5%) found themselves to have one or more carious tooth(teeth). The disparity between them was statistically significant (p < 0.001). 5. As for connections between dietary habits and dental caries, those who had dental caries (2.29) showed a greater preference for snack than the others who hadn't (2.21). The preference for snack made a bigger statistically significant difference to dental caries than the other dietary habits (p < 0.05).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4B
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• pp.337-346
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• 2010

Climate change has a huge impact on various parts of the world. This study quantified and analyzed the effects on hydrological behavior caused by climate, vegetation canopy and land use change of Soyanggang dam watershed (2,694.4 $km^2$) using the semi-distributed model SWAT (Soil Water Assessment Tool). For the 1997-2006 daily dam inflow data, the model was calibrated with the Nash-Sutcliffe model efficiencies between the range of 0.45 and 0.91. For the future climate change projection, three GCMs of MIROC3.2hires, ECHAM5-OM, and HadCM3 were used. The A2, A1B and B1 emission scenarios of IPCC (Intergovernmental Panel on Climate Change) were adopted. The data was corrected for each bias and downscaled by Change Factor (CF) method using 30 years (1977-2006, baseline period) weather data and 20C3M (20th Century Climate Coupled Model). Three periods of data; 2010-2039 (2020s), 2040-2069 (2050s), 2070-2099 (2080s) were prepared for future evaluation. The future annual temperature and precipitation were predicted to change from +2.0 to $+6.3^{\circ}C$ and from -20.4 to 32.3% respectively. Seasonal temperature change increased in all scenarios except for winter period of HadCM3. The precipitation of winter and spring increased while it decreased for summer and fall for all GCMs. Future land use and vegetation canopy condition were predicted by CA-Markov technique and MODIS LAI versus temperature regression respectively. The future hydrological evaluation showed that the annual evapotranspiration increases up to 30.1%, and the groundwater recharge and soil moisture decreases up to 55.4% and 32.4% respectively compared to 2000 condition. Dam inflow was predicted to change from -38.6 to 29.5%. For all scenarios, the fall dam inflow, soil moisture and groundwater recharge were predicted to decrease. The seasonal vapotranspiration was predicted to increase up to 64.2% for all seasons except for HadCM3 winter.

• Journal of dental hygiene science
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• v.12 no.4
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• pp.348-358
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• 2012

This study aims to prepare the basic data of the teeth color by measuring analyze mode using the color of the maxillary anterior teeth (maxillary central incisor, lateral incisor, canine) of the college students in their twenties as the dental colorimeter. The maxillary anterior teeth of the subjects of study as 467 students (male 89, female 378) were measured from 14 November to 2 December, 2011, so the color of total 1,401 teeth was examined, and oral health and eating habit attributes were researched. The survey results were as follows. 1. The color of maxillary anterior teeth was changed from maxillary central incisor to maxillary canine, brightness ($L^*$) was decreased $76.79{\pm}4.86$ to $69.72{\pm}4.62$, red chroma ($a^*$) was increased $2.02{\pm}2.00$ to $4.10{\pm}2.60$, yellow chroma ($b^*$) was increased $15.51{\pm}3.42$ to $20.10{\pm}3.46$. 2. Brightness ($L^*$) was different according to sex (p< 0.001), major (p<0.001), grade (p<0.001), smoking (p<0.001), oral health education (p<0.01), daily brushing frequency (p<0.001), brushing method (p<0.05), oral hygiene devices (p<0.001), and red chroma ($a^*$) to major (p<0.001), daily brushing frequency (p<0.05), brushing time after meals (p<0.01), oral hygiene devices (p<0.01), and yellow chroma ($b^*$) to brushing time after meals (p<0.01), subjective tooth color (p<0.001). 3. Brightness ($L^*$) of eating habit attributes was different according to coke, candy ($R^2=0.053$, p<0.05). In conclusion, this study demonstrates that the color of maxillary anterior teeth has differences in brightness ($L^*$), red chroma ($a^*$), yellow chroma ($b^*$) from each tooth, also these showed various tendency according to the oral health and eating habit attributes.

• Journal of Korean Academy of Dental Administration
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• v.5 no.1
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• pp.13-21
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• 2017

Objective: To understand the experience of medical accidents and disputes according to clinical career of dental hygienists. Methods: A self-administrated questionnaire survey was conducted from May 2012 to June 2012 targeting 313 dental hygienists in Gyeongsangnam-do, Republic of Korea. Data were analyzed by descriptive analysis, χ2-test, and one-way analysis of variance (ANOVA). Collected data were analyzed using SPSS 18.0. Results: 1) The group who had more than 6 years of clinical experience experienced complaints from patients (70.3%) and dental hygienists duty (30.7%); 2) Complaints were related to diagnosis, dental treatment instruments and materials, scaling, impression preparation, and prosthodontics. Pediatric patients had significantly more complaints compared to other patients. Overall, there were more frequent cases in the group with over 6 years of clinical career; 3) For the psychological state after experiencing patients' complaints, 'the process is difficult, but I forget after thinking it could be happen' had 160 respondents. Among them, 38.1% had clinical experience of more than 6 years, 37.5% had less than 3 years, and 24.4% had clinical career of 3~6 years; 4) About 73.6% of those had 3~6 years of clinical career answered that 'sometimes it is doubtful' on the issue of medical accidents and conflicts on prevention education of dental hygienists that 'there is a doubt about the issue of medical treatment or the occurrence of disputes'. About 60.0% of those who had less than 3 years of clinical experience answered that it was highly 'necessary but not urgent' on the necessity of preventive education, while 87.1% of those who had more than 6 years of clinical career answered that it was highly 'necessary but not urgent' on the necessity of preventive education. The difference between the two was not statistically significant. Conclusions: It is necessary and urgent to provide education related to prevention and countermeasures against malpractice disputes for dental hygienists.

• Journal of Korean Academy of Dental Administration
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• v.5 no.1
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• pp.1-12
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• 2017

Although dental hygienists have performed chair-side assisting and other dental cares as well as preventive dental cares in Korea, medical technician law confines duties of dental hygienists as closed narrative. The aim of this study was to investigate difference in perception of duties of dental hygienists in dental clinic between dentists and dental hygiene students. A total of 245 copies of questionnaires were distributed to dentists and students by post-mail. Only 42 dentists and 30 students in an area replied these questionnaires about the present and future duties of dental hygienists after providing written consent. Both groups agreed that intra and extra oral X-ray taking, education about oral health behavior, instruction after dental treatment, chair-side assisting, consulting for patients, scaling, initial impression taking, management of dental materials and equipment, sterilization of equipment, and receiving dental bills are duties of dental hygienists. However, they had different perceptions about various dental treatments as duties of dental hygienists even if they were under instructions of a dentist, including infiltration anesthesia, filling in cavity, intramuscular injection, FC change, canal irrigation, orthodontic treatment including separating, ligature bracket bonding and removing, setting crown and bridge, making individual, removing implant screw, and so on. These findings demonstrated that there were different perceptions about duties of dental hygienists between dentists and dental hygiene students, especially on dental treatment.