• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.39-59
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• 1985

The purpose of this study was to investigate how gap distances of 0.13mm, 0.15mm, 0.20mm, and 0.30mm affects solder joint strength from gold alloys and nickel-chromium base alloys and to examine the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys. The tensile test specimens were prepared in the split stainless steel mold with a half dumbbell shape 2.5mm in diameter and l2mm in length. 6 pairs of specimens of each gap distance group of gold alloys and nickel-chromium base alloys were made and 48 pairs of all specimens were soldered with solder gold of 666 fineness. All soldered specimens were machined to a uniform diameter and then a tensile load was applied at a cross-head speed of 0.10mm/min using Instron Universal Testing Machine, Model 1115. The fractured specimens at solder gold of solder joint fracture with each gap distance of 0.13mm, 0.15mm, 0.20mm, and 0.30mm were examined under the Scanning Electron Microscope, JSM-35c and the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys was analyzed by Electron Probe Micro Analyzer. The results of this study were obtained as follows: 1. In case of soldering of gold alloys, the tensile strength between gold alloys showed $37.33{\pm}2.52kg/mm^2$ at 0.13, $39.14{\pm}3.35kg/mm^2$ at 0.15mm, $43.76{\pm}2.97kg/mm^2$ at 0.20mm, and $49.18{\pm}4.60kg/mm^2$ at 0.30mm. There was statistically significant difference at each gap distance, and so the greater increase of gap distance showed the greater tensile strength. 2. In case of soldering of nickel-chromium base alloys, the tensile strength between nickel-chromium base alloys showed $34.84{\pm}4.26kg/mm^2$ at 0.13mm, $37.25{\pm}2.49kg/mm^2$ at 0.15mm, $42.91{\pm}4.32kg/mm^2$ at 0.20mm, and $46.93{\pm}4.21kg/mm^2$ at 0.30mm. There was not statistically significant difference only between 0.13mm and 0.15mm and bet ween 0.20 mm and 0.30mm, but generally the greater increase of gap distance showed the greater tensile strength. 3. The greater increase of gap distance shoed less porosities in solder gold at solder joint fracture. 4. In solder gold Au, Cu, Ag, Zn, and Sn were composed and Au and Cu were mostly distributed uniformly. 5. In solder joints of solder gold and gold alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Au, Cu, Ag, Pt, and Pd were composed in gold alloys. Au and Cu of solder gold and gold alloys were mostly distributed uniformly and the diffusion of other elements except Pt and Pd around the solder joint was not almost found. In solder joints of solder gold and nickel-chromium base alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Ni, Cr, and Al were composed in nickel-chromium base alloys. Au and Cu of solder gold and Ni and Cr of nickel-chromium base alloys were mostly distributed uniformly and the diffusion of other elements except Cr around the solder joint was not almost found.

• Journal of The Korean Association For Science Education
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• v.36 no.4
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• pp.591-606
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• 2016

The purpose of this study is to develop the argumentation program to build scientific concepts on natural selection for science-gifted elementary students and to know how to implement this program. For this study, nine key concepts about natural selection such as the overproduction of offspring, limited resources, population stability, competition, variation, heredity of variation, differential survival, change of the population and speciation were selected through the literature study. The programs were developed by learning cycle instructional model. Argument writings and discourses have been collected, analyzed and compared before and after the program. Two questionnaires to compare pre and post concept change consist of multiple choice questionnaire and open-ended response question were developed and applied to 19 science-gifted elementary students. Sufficiency of the explanation and conceptual quality of the explanation were used to assess the quality of their arguments before and after the program. Discourse and visual models collected from the highest and lowest group about score improvement were compared. The scores of the gifted statistically improved significantly in multiple choice questionnaire. Students' alternative conceptions about natural selection at the beginning of the program decreased and changed scientifically after the program. Visual models drawn by the students supported the results as well. This study asserts that elementary science-gifted students are able to explain evolutionary perspectives about organism change and use the key concepts of natural selection. The study means that evolutionary perspective is possible to be reflected in elementary science curriculum for the gifted.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.43-53
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• 2009

Objective: The purpose of this study was to compare the difference in three dimensional tooth movement using three different wire sizes($0.018{\times}0.025-in,\;0.016{\times}0.022-in$ 0.016-in) on a NiTi scissors-bite corrector. Methods: Computed tomography(CT) images of the experimental model before and after tooth movement were taken and reconstructed into three dimensional models for superimposition. The direction and the amount of tooth movement were measured and analyzed statistically. Results: The lingual and intrusive movements of the crown of the maxillary second molar were increased as the size of the NiTi wire increased. The roots of the maxillary second metals moved buccally except for the 0.016-in group. The intrusive movement of the roots of the maxillary second molars was increased as the size of the NiTi wire increased. Due to the use of orthodontic mini-implants, anchorage loss was under 0.2 mm on average. Conclusions: The $0.018{\times}0.025-in$ NiTi wire was most effective in lingual and intrusive movement of the maxillary second molar which was in scissors-bite position. Indirect skeletal anchorage with a single orthodontic mini-implant was rigid enough to prevent anchorage loss.

• Journal of dental hygiene science
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• v.1 no.1
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• pp.28-38
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• 2001

The aim of this study was to analyze the dental caries of chilren's deciduous teeth in relation to their mothers' socioeconomic factors and their oral health beliefs to increase the effect on children's oral health. One hundred seventy four children and their mothers were selected for the study. The children were 5 and 6 years old in children house in Kun-san, Korea. Research was conducted by oral examination, their mothers' socioeconomic factors and dental health belief model. The finding of analysis can be summaried as follows; In regard to the caries in deciduous teeth status, the five-year-old boy children's dft index was 3.39 and that of the girls of the same age was 2.76. The dft index of the boys of six was 3.86 and that of the girls of the same age was 3.27. The five-year-old boy children had the highest df rate(81.8%), and their dt rate was more than their ft rate. But for the six-year-old girl children, ft rate was higher than dt rate. For the five years old, the boy children's ft rate was significantly higher than that of the girls(p<0.05). Concerning the caries in deciduous teeth states by socioeconomic factors, their oral health status was significantly different according to mother employment and householder age. The df rate of the preschoolers with working mothers(84.7%) was significantly higher than that of those with nonworking mothers(66.7%)(p<0.05). The dft index of the group whose households were over forty was highest with 4.07, followed by the children of the households aged 35 to 39 with 3.83, those of the households aged 25 to 29 with 3.33, and those of the households aged 30 to 34 with 2.15. The difference between the groups was significant(p<0.05). As to the difference of maternal dental health beliefs by maternal socioeconomic factors, households educational background and whether to live with parents or parents-in-law under the same roof made a significant difference to maternal oral health beliefs. The mothers whose households were college graduates or better-educated were stronger in oral health susceptibility and seriousness(p<0.01, p<0.05). The salience was recognized more by those who lived with parents or parents-in-law than by the others who didn't(p<0.05). The dft index of the preschoolers was related to maternal dental health beliefs. That was lower when their mothers perceived dental health benefit better.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.7
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• pp.445-453
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• 2012

An investigation for removal of 1-indanone (1-ID), which were commonly produced from the biological and/or chemical treatment and natural weathering of the PAHs-contaminated soils, via oxidative transformation mediated by birnessite in the presence of various phenolic mediators is described. This study also examines the potential effect of the natural occurring substance humic acid (HA) on the oxidative transformation. The experiment was carried out in aqueous phase as a batch test (10 mg/L 1-ID, 0.3 mM phenolic mediators, $1.0g/L\;{\delta}-MnO_2$, at pH 5). All of the 11 tested phenoilic mediators belong to the group of natural occurring phenols and are widely used as model constituents of humic substances. From the results of HPLC analysis, it is demonstrated that 1-ID was not reactive to birnessite itself, but it can be effectively removed in birnessite-mediated cross coupling reactions in the presence of the phenolic mediators. The percent removals of 1-ID after 2 day incubation were ranged from 9.2 to 71.2% depending on the phenolic mediators applied. The initial rate constant ($K_{int}$, $hr^{-1}$) values for the 1-ID removals obtained from the pseudo-first-order kinetic plots also widely ranged from 0.18 to 15.0. Results of the correlative analysis between the removal efficiencies and structural characteristics of phenolic mediators indicate that the transformation of the 1-ID was considerably enhanced by the addition of electron-donating substituents (e.g., -OH, $-OCH_3$) at the benzne ring, and much less enhanced by the addition of electron-withdrawing substituents (e.g., -COOH, -CHO). The presence of HA showed that removal efficiencies of 1-ID in the birnessite-phenolic mediator systems decreased with increasing HA concentrations. However at low concentration of HA (< 2 mg/L), it caused some enhancement in the removals of 1-ID as compared to the control.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.4
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• pp.501-509
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• 2012

The dietary intake of whole grains is known to reduce the incidence of chronic diseases such as obesity, diabetes, cardiovascular disease, and cancer. In our previous study, hog millet (HM, $Panicum$ $miliaceum$ L.) water extract showed the highest anti-lipogenic activity among nine cereal types in 3T3-L1 cells. In this study, the effect of hog millet water extract on hepatic steatosis and lipid metabolism in mice fed a high fat diet was investigated. Mice were fed a normal-fat diet (ND), high-fat diet (HFD) or HFD containing 1% or 2% (w/w) HM for 7 weeks. Body weight and food intake were monitored during the study period. Insulin resistance by homeostasis model assessment (HOMA-IR), fasting lipid profile, hepatic fatty acid metabolism-related gene expression determined, and intraperitoneal glucose tolerance test (IGTT) were performed at the study's end. The results indicated that 1% and 2% HM diets effectively decreased liver weights, blood TG and T-cholesterol levels (p<0.05), while the HDL-cholesterol level was increased (p<0.05) compared to HFD-induced steatotsis mice. Hepatic lipogenic-related gene ($PPAR{\alpha}$, L-FABP, and SCD1) expressions decreased, whereas lipolysis- related gene (CPT1) expression increased in animals fed the 2% PME diet (p<0.05). In addition, mice fed 1% or 2% HM diet had markedly decreased IGTT and HOMA-IR, compared to the those of the HFD-induced hepatic steatosis control group (p<0.05). These results indicated that HM inhibited hepatic lipid accumulation by regulating fatty acid metabolism, and suggested that HM is useful in the chemoprevention or treatment of high fat-induced hepatic steatosis and hepatic steatosis-related disorders including hyperlipidemia, glucose sensitivity, and insulin resistance.

• Sleep Medicine and Psychophysiology
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• v.21 no.1
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• pp.5-13
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• 2014

Objectives: Depression, sleep complaints and cognitive impairments are commonly observed in the elderly. Elderly subjects with depressive symptoms have been found to show both poor cognitive performances and sleep disturbances. However, the relationship between sleep complaints and cognitive dysfunction in elderly depression is not clear. The aim of this study is to identify the association between sleep disturbances and cognitive decline in late-life depression. Methods: A total of 282 elderly people who underwent nocturnal polysomnography in a sleep laboratory were enrolled in the study. The Korean version of the Neuropsychological Assessment Battery developed by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD-K) was applied to evaluate cognitive function. Depressive symptoms were assessed with the geriatric depression scale (GDS) and subjective sleep quality was measured using the Pittsburg sleep quality index (PSQI). Results: The control group ($GDS{\leq}9$) when compared with mild ($10{\leq}GDS{\leq}16$) and severe ($17{\leq}GDS$) depression groups, had significantly different scores in the Trail making test part B (TMT-B), Benton visual retention test part A (BVRT-A), and Stroop color and word test (SCWT)(all tests p<0.05). The PSQI score, REM sleep duration, apnea-hypopnea index and oxygen desaturation index were significantly different across the three groups (all indices, p<0.05). A stepwise multiple regression model showed that educational level, age and GDS score were predictive for both TMT-B time (adjusted $R^2$=35.6%, p<0.001) and BVRT-A score (adjusted $R^2$=28.3%, p<0.001). SCWT score was predicted by educational level, age, apnea-hypopnea index (AHI) and GDS score (adjusted $R^2$=20.6%, p<0.001). Poor sleep quality and sleep structure alterations observed in depression did not have any significant effects on cognitive deterioration. Conclusion: Older adults with depressive symptoms showed mild sleep alterations and poor cognitive performances. However, we found no association between sleep disturbances (except sleep apnea) and cognitive difficulties in elderly subjects with depressive symptoms. It is possible that the impact of sleep disruptions on cognitive abilities was hindered by the confounding effect of age, education and depressive symptoms.

• The Korean Journal of Community Living Science
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• v.16 no.4
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• pp.83-93
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• 2005

This study was conducted to provide information about the behavioral intentions to diet in adolescent females. To explain the behavior intention to diet, a conceptual framework based on the ' Social Support, Control and the Stress Process Model ' and the ' Theory of Reasoned Actio ' was used. The survey was carried out by self-questionnaires with 463 female high school and college students in Daegu. Analysis of data was done by using mean, correlation and multiple regression analysis with the SAS computer program. Subjects were divided into 3 groups-underweight, normal weight, and overweight-according to their current body size. The most powerful influencing factor related to perceived stress -that is dissatisfaction with body image- was the current figure, regardless of current body size. The fatter the current body size, the higher the score for the behavioral intention to diet. In attitude toward the behavior of dieting, the fatter the current figure, the higher the attitude score, and the belief of behavioral outcome was the main decision variable. For the score of the subjective norm, the overweight group was significantly higher than other groups. The influencing factors for the behavioral intention to diet were perceived stress and attitude toward dieting behavior, especially beliefs of behavioral outcome.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.555-563
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• 2004

The pH of beverages is known to be low and have, therefore, been implicated in the increasing incidence of erosion. Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will always be a contribution from attrition and abrasion. The aim of the present study was to evaluate the effect of yogurt on the progression of erosive demineralization in human enamel using demineralization model in vitro. In 4 yogurts, available on the market, pH, buffering capacity and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. 50 milliliters of each drink was then titrated with 1M sodium hydroxide, added in 0.5 milliliters increments, until the pH reached about 7. Human deciduous enamel(n=40) samples were divided into four groups and exposed to 80ml of the yogurt for 30,60, 90 and 120min. Enamel surface microhardness(VHN) was examined before and after each exposure. 1. The average PH of fermented milk was 3.77 and this pH value was acidic enough to cause tooth erosion. 2. All of the fermented milks were found to be erosive(p<0.05) 3. The teeth exposed to the fermented milk all showed erosion like lesions and microhardness measurements showed that enamel surface hardness decreased proportionately with increased time of immersion in all tooth specimen groups. 4. After immersion for 30 and 60 minutes, reduction rate of microhardness values was not significantly different between the groups(p>0.05). However, after 90 and 120 minutes, reduction rate of each group was significantly different(p<0.05).

• Journal of Service Research and Studies
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• v.10 no.3
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• pp.23-42
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• 2020

This study conceptualized the essence and propensity of modern management in service age, based on philosophy, and developed items to evaluate the conceptualized content. It was carried out as a new study to deepen the study of management philosophy and management theory by the new management framework. In order to establish the philosophical foundation of the modern management, the essence of the modern management was conceptualized based on the fundamental ideas of the East and West, and then an evaluation item was developed to put the essence and propensity of the modern management into practical use through analytical and empirical methods. After analyzing the representative ideas of mankind, it was derived that the Book of Change has the qualification as a philosophical model that can derive the essence of modern management. The Book of Change explains the reasoning of the world in the structure of two opposing parties, such as Taiji or Yin and Yang, and the process of acknowledging the contradictions within each opposing party and overcoming the contradictions through change is the central idea. Because you can see. After conducting a conceptual study, through empirical research, the essence and propensity of a modern manager should be conceptualized. The concept of essence and empirical study of the modern management using the leading role was conducted in two stages. First, a qualitative study using repetitive comparative analysis (CCM), focus group interview (FGI), and text mining was conducted to derive the essential and propensity conceptualization items that modern managers should possess. In addition, a quantitative study using factor analysis to develop sample items and develop measurement items through literature review and FGI was conducted to derive the essential concept of the modern management. Finally, the essence of modern management was derived: learning, preparation, challenge, inclusion, trust, morality, and sacrifice. In the future, it is necessary to conduct empirical research on the effectiveness of the essence of modern management for global and Korean representative companies.