• 대한치과교정학회지
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• 제45권1호
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• pp.29-37
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• 2015

Objective: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. Methods: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a $0.017{\times}0.025$-in wire in the 0.018-in slots and a $0.019{\times}0.025$-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey's post-hoc test at the 95% confidence level (${\alpha}$ = 0.05) were also used for statistical analyses. Results: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (${\mu}$ = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (${\mu}$ = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (${\mu}$ = 0.85). Conclusions: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.

• 한국치위생학회지
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• 제16권5호
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• pp.687-693
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• 2016

Objectives: The purpose of the study was to investigate the influence of instructor trust on learning flow and academic achievement in dental hygiene students. Methods: A self-reported questionnaire was completed by 202 dental hygiene students in Gyeongnam from July to August, 2016. A five point Likert scale questionnaire consisted of intimacy (8 items), professionalism (8 items), teaching ability (5 items), and leadership (6 items). Measurement of learning flow was adapted and modified by Kim et al. Academic achievement was adapted and modified by Noe and Schmitt. Cronbach's ${\alpha}$ of learning flow was 0.77 and that of academic achievement was 0.78 in the study. Data wee analyzed by t-test, one way ANOVA, $Scheff{\acute{e}}$ test, and Pearson's correlation using SPSS 23.0 program. Results: The scores of instructor trust, learning flow, and academic achievement were 4.37, 3.46, and 3.23, respectively. Academic achievement had a close positive correlation with instructor trust (r=0.46, p<0.001) and learning flow (r=0.63, p<0.001). Instructor trust had a positive correlation with learning flow (r=0.50, p<0.001). Learning flow took mediating effects on instructor trust and academic achievement. Conclusions: The trust between students and instructors had a great influence on learning flow and academic achievement. So the instructor should try to make the students concentrate on learning.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.418-424
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• 2019

Densification is a process for improving the strength properties of wood from the felling of young trees, which is a common harvest practice in community forests. A series of experiments was conducted to refine the process with particular regard to the determination of suitable pretreatment and treatment conditions. Samples of pine and gmelina measuring $23cm(L){\times}20cm(W){\times}2cm(T)$ underwent pretreatment through immersion in a 1:1 $CH_3COOH-H_2O_2$ solution at concentrations of 15%, 20%, and 30%. Samples pretreated with the 20% solution showed the greatest improvement in strength; further experiments were conducted to determine the optimum treatment conditions in terms of temperature and duration following immersion. Test samples with the same dimensions as those in the pretreatment experiment were soaked in a 1:1 20% $CH_3COOH-H_2O_2$ solution and warmed in a water bath. The test samples were then individually hot pressed to the target thickness, which was 30% less than the original thickness and held at $150^{\circ}C$ or $170^{\circ}C$ for 15 or 30 minutes. The treated samples were cut for an analysis of their density, recovery of set, and bending strength. Pine and gmelina exhibited the best characteristics after treatment at $150^{\circ}C$ for 30 and 15 minutes, respectively. The results suggest that the modified densification process had increased the bending strength of the wood, but the temperature and duration of treatment must be carefully considered for different wood species.

• 한국도로학회논문집
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• 제10권4호
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• pp.41-52
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• 2008

본 연구는 박리방지 첨가제를 혼입한 아스팔트 혼합물의 수분민감성에 대한 특성 평가 방안을 제시하고자, 기존의 수침 시험을 개선한 3가지 종류($H_c$, $V_s$, F-T)의 수침 방법을 통하여 생석회, 소석회, 1종의 액상 박리방지 첨가제를 혼입한 각 아스팔트 혼합물에 대한 수분민감성의 거동 특성을 분석하였다. 실험방법은 AASHTO TP-9에 규정된 간접인장시험(Indirect Tensile Test, IDT)을 통한 크리프시험 (Creep Test), 회복탄성계수시험(Resilient Modulus Test) 및 강도시험(Strength Test)을 수행하였다. 분석방법으로는 미국 플로리다 대학의 Roque에 의해 제안된 에너지비(Energy Ratio, ER) 개념을 사용하여 박리방지제의 사용에 따른 효과 및 수분민감도 특성을 평가하였다(Roque, 2004). 시험결과, 수분처리 방법 에 따른 아스팔트 흔합물의 물성 변화뿐만 아니라 박리 방지 첨가제에 따른 물성 변화가 현저하게 나타났다. 또한 누적 수분 손상에 의해 발생되는 균열에 대한 저항성이 각 첨가제 및 수분처리 방법에 따라 변화됨을 나타내었다. 이를 토대로 Energy Ratio를 분석한 결과 약 $10{\sim}30%$ 정도의 균열 저항성 변화가 나타났다.

• 초등상담연구
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• 제6권1호
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• pp.117-140
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• 2007

This study is to know the effect of drama therapy on the sociality of isolated children. To achieve this goal, the following hypothesis was built. Hypothesis I. Dramatherapy program will improve the sociality of isolated children. I -1. Dramatherapy program will improve in cooperation. I -2. Dramatherapy program will improve in independency. I -3. Dramatherapy program will improve in sociability. I -4. Dramatherapy program will improve in law-abiding. To test this hypothesis, the social and emotional isolation test was conducted in 190 children consisting of fifth-grader from N elementary school located in Busan to select 28 children whose founded to be isolated; among these children, eight who wanted to participate in the program were positioned at the experimental group and other eight who didn't want to do and who demonstrated the range of marks similar to the experimental group were positioned at the control group. The dramatherapy program was based on the theory by Robert Landy (2002), Jennings (2003) and Phil Jones (2005) to improve the sociality of isolated children and was implemented in a total of 15 sessions, two sessions a week after school. To test the effect of the program, A modified test paper by Suh, Poongyeon (1991) with the content of testing sociality into a test paper of human nature for elementary school students to be made by Jeong, Bummo (1971) was used which consists of four sub-factors: cooperation, independency, sociability, law-abiding. As a quantitative analysis, Mann-Whitney Test were analyzed for experimental and control groups. As a qualitative analysis, the interaction patterns among student were analyzed on he basis of video tapes. The tool of observe the interaction patterns among student was Interaction Process Analysis System which was made by Bales (1970). This study obtained the following result First, the drama therapy had meaningful effect on the sociality of the sociality of isolated children. But the quantitative change of the sociality test conclusion was showed meaningfully and positive social behavior was increased in periodical process analysis. Second, in the Interaction Process Analysis(IPA) affirmative interactions increased and negative interactions decreased.

• 한국도로학회논문집
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• 제15권4호
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• pp.43-51
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• 2013

PURPOSES : The main purposes of this study are to examine the influences of polyethylene wax-based WMA additive on the optimum asphalt content of warm-recycled asphalt mixture based on the Marshall mix design and to evaluate performance of warm-recycled asphalt mixture containing 30% RAP with polyethylene wax-based WMA additive. METHODS: Physical and rheological properties of the residual asphalt were evaluated in terms of penetration, softening point, ductility and performance grade (PG) in order to examine the effects of polyethylene wax-based WMA additive on the residual asphalt. Also, To evaluate performance characteristics of the warm-recycled asphalt mixtures using polyethylene wax-based WMA additive along with a control hot-recycled asphalt mixture, indirect tensile strength test, modified Lottman test, dynamic immersion test, wheel tracking test and dynamic modulus test were conduced in the laboratory. RESULTS : Based on the limited laboratory test results, polyethylene wax-based WMA additive is effective to decrease mixing and compacting temperatures without compromising the volumetric characteristics of warm-recycled asphalt mixtures compared to hot-recycled asphalt mixture. Also, it doesn't affect the optimum asphalt content on recycled-asphalt mixture. All performance test results show that the performance of warm-recycled asphalt mixture using polyethylene wax-based WMA additive is similar to that of a control hot-recycled asphalt mixture. CONCLUSIONS: Overall, the performance of warm-recycled asphalt mixture using polyethylene wax-based WMA additive is comparable to hot-recycled asphalt mixture.

• Journal of Biosystems Engineering
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• 제37권4호
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• pp.233-244
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• 2012

Purpose: The kinetic evaluation was performed for swine manure (SM) degradation and biogas generation. Methods: The SM was anaerobically digested using batch digesters at feed to inoculum ratio (F/I) of 1.0 under mesophilic conditions ($36.5^{\circ}C$). The specific gas yield was expressed in terms of gram total chemical oxygen demand (mL/g TCOD added) and gram volatile solids added (mL/g VS added) and their effectiveness was discussed. The biogas and methane production were predicted using first order kinetic model and the modified Gompertz model. The critical hydraulic retention time for biomass washout was determined using Chen and Hashimoto model. Results: The biogas and methane yield from SM was 346 and 274 mL/ TCOD added, respectively after 100 days of digestion. The average methane content in the biogas produced from SM was 79% and $H_2S$ concentration was in the range of 3000-4108 ppm. It took around 32-47 days for 80-90% of biogas recovery and the TCOD removal from SM was calculated to be 85%. When the specific biogas and methane yield from SM (with very high TVFA concentration) was expressed in terms of oven dried volatile solids (VS) basis, the gas yield was found to be over estimated. The difference in the measured and predicted gas yield was in the range of 1.2-1.5% when using first order kinetic model and 0.1% when using modified Gompertz model. The effective time for biogas production ($T_{Ef}$) from SM was calculated to be in the range of 30-45 days and the critical hydraulic retention time ($HRT_{Critical}$) for biomass wash out was found to be 9.5 days. Conclusions: The modified Gompertz model could be better in predicting biogas and methane production from SM. The HRT greater than 10 days is recommended for continuous digesters using SM as feedstock.

• 대한치과교정학회지
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• 제48권4호
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• pp.224-235
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• 2018

Objective: The purpose of this study was to compare the skeletal, dental, and soft-tissue treatment effects of nonextraction therapy using the modified C-palatal plate (MCPP) to those of premolar extraction (PE) treatment in adult patients with Class II malocclusion. Methods: Pretreatment and posttreatment lateral cephalographs of 40 adult patients with Class II malocclusion were retrospectively analyzed. The MCPP group comprised 20 patients treated with total arch distalization of the maxillary arch while the PE group comprised 20 patients treated with four PE. Fifty-eight linear and angular measurements were analyzed to assess the changes before and after treatment. Descriptive statistics, paired t-test, and multivariate analysis of variance were performed to evaluate the treatment effects within and between the two groups. Results: The MCPP group presented 3.4 mm of retraction, 1.0 mm of extrusion, and $7.3^{\circ}$ lingual inclination of the maxillary central incisor. In comparison, the PE group displayed greater amount of maxillary central incisor retraction and retroclination, mandibular incisor retraction, and upper lip retraction (5.3 mm, $14.8^{\circ}$, 5.1 mm, and 2.0 mm, respectively; p < 0.001 for all). In addition, the MCPP group showed 4.0 mm of distalization and 1.3 mm of intrusion with $2.9^{\circ}$ distal tipping of the maxillary first molars. Conclusions: These findings suggest the MCPP is an effective distalization appliance in the maxillary arch. The amount of incisor retraction, however, was significantly higher in the PE group. Therefore, four PE may be recommended when greater improvement of incisor position and soft-tissue profile is required.

• 가정과삶의질연구
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• 제21권2호
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• pp.19-30
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• 2003

In this study, housewives' attitudes toward genetically modified foods (GM foods) and their willingness to purchase GM foods were examined. The findings of this study could provide useful information for consumer education and consumer policy development regarding GM foods. The specific purposes of this study were: (1) to examine consumers' attitudes toward GM foods, (2) to analyze the effect of the perception of GM foods and demographic variables on consumers' attitudes toward GM foods, and (3) to analyze the effect of the perception of GM foods and demographic variables on consumers' willingness to purchase GM foods. The questionnaire used in the survey was constructed by the author, based on existing literature. The survey was conducted with 1,100 housewives, and 723 of the completed survey forms were used in the final analysis. Frequencies, percentages, means, standard deviation, t-tests, ANOVA, Duncan-test, Pearson's Correlation, factor analysis, and discriminant analysis were employed for data analysis methods. Major findings are: (1) Consumers' attitudes toward GM foods consist of three factors, that are, attitude regarding potential danger, attitude regarding the use of GM technique on plants, and attitude regarding the use of GM technique on animals. (2) Consumers with a higher level of education tend to perceive GM food as more dangerous, whereas consumers with a lower level of education tend to accept more the use of GM technique on plants. (3) Consumers who tend not to consider GM foods as dangerous, and those who acknowledged benefits in using GM technique on plants are more willing to buy GM foods.

• 임상간호연구
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• 제23권3호
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• pp.398-406
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• 2017

Purpose: The purpose of this study was to evaluate food carving among hemodialysis patients and to identify factors affecting the food carving. Methods: A descriptive correlational study was conducted. Data were collected from 129 patients receiving hemodialysis between March 15 and April 15, 2017. Measurement instruments included the general food craving questionnaire trait, the center for epidemiological studies-depression scale, and stress response inventory-modified form. The statistical analysis included t-test, analysis of variance, pearson correlation analysis, and stepwise multiple regression analysis. Results: Mean food craving score was $53.00{\pm}12.36$. Food craving was higher in patients younger than 40 years (F=4.36 p=.006) and having occupation (t=2.18 p=.031). Patients receiving hemodialysis demonstrated higher levels of depression ($21.37{\pm}9.62$) and stress ($39.68{\pm}15.95$). Factors influencing food craving were depression (${\beta}=.52$, p<.001), stress (${\beta}=.65$, p<.001), and age 50~59 years old (${\beta}=-.28$, p=.001) and 60~69 years old (${\beta}=-.19$, p=.026), which accounted for 25.6% of total variance. Conclusion: Food craving among hemodialysis patients was influenced by patients' depression, stress and age. Assessment and management of depression and stress needs to be incorporated as a nursing strategy for dietary management for hemodialysis patients.