• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.290-299
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• 2006

Objectives: The purpose of this study is to evaluate the effect of ethylene glycol analogs on modulus of elasticity and ultimate tensile strength of moist, demineralized dentin matrix. Methods: Dentin disks 0.5 mrn thick were prepared from mid-coronal dentin of extracted. unerupted, human third molars. 'I' beam and hour-glass shaped specimens were prepared from the disks, the ends protected with nail varnish and the central regions completely demineralized in 0.5M EDTA for 5 days. Ultimate tensile stress (UTS) and low strain modulus of elasticity (E) were determined with specimens immersed for 60 min in distilled water $(H_{2}O)$, ethylene glycol $(HO-CH_{2}-CH_{2}-OH)$, 2-methoxyethanol $(H_{3}CO-CH_{2}-CH_{2}-OH)$, and 1,2-dimethoxyethane $(H_{3}CO-CH_{2}-CH_{3}-OCH_{3})$ prior to testing in those same media. Modulus of elasticity was measured on the same specimens in a repeated measures experimental design. The results were analyzed with a one-way ANOVA on ranks, followed by Dunn's test at ${\alpha}\;=\;0.05$. Regression analysis examined the relationship between UTS or E and hoy's solubility parameter for hydrogen bonding $({\delta}_{h})$ of each solvent. Results: The UTS of demineralized dentin in water, ethylene glycol, 2-methoxyethanol, and 1,2-dimethoxyethane was 24 (3), 30 (5), 37 (6), and 45 (6) MPa, ${\times}$ (SD) N = 10. Low strain E for the same media were 16 (13), 23 (14), 52 (24), and 62 (22) MPa. Regression analysis of UTS vs ${\delta}_{h}$ revealed a significant $(p\;<\;0.0001,\;r\;=\;-0.99,\;R^{2}\;=\;0.98)$ inverse, exponential relationship. A similar inverse relationship was obtained between low strain E vs ${\delta}_{h}\;(p\;<\;0.0005,\;r\;=\;-0.93,\;R^{2}\;=\;0.86)$. Significance: The tensile properties of demineralized dentin are dependent upon the hydrogen bonding ability of polar solvents $({\delta}_{h})$. Solvents with low ${\delta}_{h}$ values may permit new interpeptide H-bonding in collagen that increases its tensile properties. Solvents with high ${\delta}_{h}$ values prevent the development of these new interpeptide H-bonds.

• Journal of Korean society of Dental Hygiene
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• v.15 no.2
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• pp.261-269
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• 2015

Objectives: The purpose of the study is to investigate the correlation and influencing factors of oral health awareness, oral health behaviors, self-esteem and OHIP-14. Methods: A self-reported questionnaire was filled out by 313 childcare teachers in Jeonnam from June 4 to 14, 2013. The questionnaire consisted of 3 questions of general characteristics, 4 questions of occupation, 1 question of oral health education experience, and 1 question of oral health education participation. The instrument for awareness and behavior of oral health were modified and consisted of 10 questions of awareness and 10 questions of behavior by Likert 5 scale. Cronbach's alpha was 0.718 in awareness and 0.812 in behavior. Instrument for self-esteem was modified from Rosenberg. Self-esteem questionnaire consisted fo 5 questions of positive answers and 5 questions of negative answers by Likert 5 scale. Cronbach's alpha in self esteem was 0.846 in the study. Oral Health Impact Profile-14(OHIP-14) was adapted from Slade by Likert 5 scale and consisted fo 14 questions. Cronbach's alpha was 0.934 in the study. Data were analyzed by chi square test, t-test, one way ANOVA, Scheffe multiple range test, Pearason's correlation test, and stepwise multiple regression test. Results: There were positive correlations between oral health awareness, oral health behavior(r=0.502), and self-esteem(r=0.332), but negative correlations with OHIP-14. Oral health behavior showed positive correlations with self-esteem(r=0.230). The factors on oral health awareness were high oral health behavior and self esteem, low OHIP-14, and active participation in education. Self-esteem was closely related to high with high oral health awareness. low OHIP-14, low job satisfaction. Conclusions: Childcare teachers play the very important roles in the development of oral health education program for children and continuous education.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.313-318
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• 2016

Purpose: This study measured and analyzed the PTO (power take off) torque of a transplanter according to the planting conditions during field operation. Methods: A torque measurement system was constructed with torque sensors to measure the torque of a PTO shaft, a measurement device to acquire sensor signals, and a power controller to provide power for a laptop computer. The field operation was conducted at four planting distances (26, 35, 43, and 80 cm) and two planting depths using the transplanter on a field with similar soil conditions. One-way ANOVA with planting distance and Duncan's multiple range test at a significance level of 0.05 were used to analyze the PTO torque. The torque ratio was calculated based on the minimum torque using the average PTO torque measured under each planting condition. Results: The average torques on the PTO shaft for planting distances of 26, 35, 43, and 80 cm at a low planting depth were 11.05, 9.07, 7.04, and 3.75 Nm, respectively; the same for planting distances of 26, 35, 43, and 80 cm at a middle planting depth were 12.20, 9.86, 7.94, and 4.32 Nm, respectively. When the planting distance decreased by 43, 35, and 26 cm, the torque ratio at a low planting depth increased by 88, 142, and 195%, respectively. When the planting distance decreased by 43, 35, and 26 cm, the torque ratio at the middle planting depth increased by 84, 128, and 182%, respectively. Conclusions: PTO torque fluctuated by planting distance and depth. Moreover, the PTO torque increased for short planting distances. Therefore, farmers should determine the planting conditions of the transplanter by considering the load and durability of the machine. The results of this study provide useful information pertaining to the optimum PTO design of the transplanter considering the field load.

• Journal of Korean society of Dental Hygiene
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• v.18 no.2
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• pp.253-267
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• 2018

Objectives: The purpose of this study was to examine how the dentist's servant leadership affects the happiness index of dental hygienists. Methods: The subjects were 221 dental hygienists that have been working at dental clinics or dental hospitals. The data were analyzed using SPSS Version 20.0 (IBM Co., Armonk, NY, USA). An independent t-test and one-way ANOVA analysis were conducted to examine the difference in the happiness index of dental hygienists according to general characteristics. The independent t-test was conducted to examine organizational culture and happiness index according to upper and lower group based on the mean score for servant leadership. Pearson's correlation analysis was used to examine the correlation among key factors. Multiple regression analysis was conducted to identify factors influencing the happiness index of dental hygienists. Results: According to the analysis, there was a statistically significant positive correlation between the dentist's servant leadership, the organizational culture and the happiness index of dental hygienists. However, a stewardship of the dentist's servant leadership factors was not found to have any correlation with the market culture. A multiple regression analysis was performed after including the dentist's servant leadership, the organizational culture and the happiness index of dental hygienists. Meanwhile, the stewardship and community-building effect of the dentist's servant leadership had a statistically significant effect on the happiness index of dental hygienists. Consequently, a higher servant leadership factor in dentists was correlated with a higher happiness index of dental hygienists. Conclusions:The findings show that the dentist's servant leadership affect the happiness index of dental hygienists. Therefore, effective intervention and education programs related to the dentist's servant leadership and sound organizational culture are necessary to enhance dental hygienists' happiness index. Additionally, a follow-up study will determine the causal relationship among the dentist's servant leadership, the organizational culture and the happiness index of dental hygienists, considering organizational members and the environment of the dental clinics.

• Restorative Dentistry and Endodontics
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• v.34 no.6
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• pp.508-514
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• 2009

The purposes of this study were to compare the efficacy of irrigation systems by removing a calcium hydroxide $(Ca(OH)_2)$ paste from the apical third of the root canal and the effect of the patency file. Sixty single rooted human teeth were used in this study. The canals were instrumented by a crown-down manner with .04 taper ProFile to ISO #35. $Ca(OH)_2$ and distilled water were mixed and placed inside the root canals. The teeth were divided into 6 groups according to the root canal irrigation system and the use of patency file as follows: group 1 - conventional method: group 2 - $EndoActivator^{(R)}$: group 3 - $EndoVac^{(R)}$; group 4 - conventional method, patency: group 4 - $EndoActivator^{(R)}$, patency; group 6 - $EndoVac^{(R)}$, patency. All teeth were irrigated with sodium hypochlorite. After the root canal irrigation, the teeth were split in bucco-lingual aspect. Percentage of the root canal surface coverage with residual $Ca(OH)_2$ until 3 mm from working length was analyzed using Image Pro Plus ver. 4.0. Statistical analysis was performed using the One-way ANOVA, t-test and Scheffe's post-hoc test. Conventional groups had significantly more $Ca(OH)_2$ debris than $EndoActivator^{(R)}$, $EndoVac^{(R)}$ groups. There was no significant difference between $EndoActivator^{(R)}$ and $EndoVac^{(R)}$ groups. Groups with patency file showed more effective in removing $Ca(OH)_2$ paste than no patency groups. but. it was no significant difference. This study showed that $EndoActivator^{(R)}$ and $EndoVac^{(R)}$ systems were more effective in removing $Ca(OH)_2$ paste from the apical third of the root canal than conventional method.

• Restorative Dentistry and Endodontics
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• v.34 no.5
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• pp.397-405
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• 2009

This study compared the effect of an activator, intermediate bonding resin and low-viscosity flowable resin on the microtensile bond strength of a self-curing composite resin used with two-step total etching adhesives. Twenty extracted permanent molars were used. The teeth were assigned randomly to nine groups (n=10) according to the adhesive system and application of additional methods (activator, intermediate adhesive, flowable resin). The bonding agents and additional applications of each group were applied to the dentin surfaces. Self-curing composite resin buildups were made for each tooth to form a core, 5mm in height. The restored teeth were then stored in distilled water at room temperature for 24h before sectioning. The microtensile bond strength of all specimens was examined. The data was analyzed statistically by one-way ANOVA and a Scheffe's test. The application of an intermediate bonding resin (Optibond FL adhesive) and low-viscosity flowable resin (Tetric N-flow) produced higher bond strength than that with the activator in all groups. Regardless of the method selected, Optibond solo plus produced the lowest ${\mu}TBS$ to dentin. The failure modes of the tested dentin bonding agents were mostly adhesive failure but there were some cases showed cohesive failure in the resin.

• Korean Security Journal
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• no.29
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• pp.115-137
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• 2011

The purpose of this study was to look into impacts of career barriers and college major satisfactions on career preparation behaviors of Security major college students. The subjects of this study were collected among 200 security major students attending universities in Choungnam and Junnam Provinces, and 170 out of 200 were analyzed. Based on collected data, exploratory factor analysis, correlation analysis, multiple regression analysis, and one-way ANOVA were conducted using SPSS 18.0. According to the result, career barriers showed negative correlations on career preparation behaviors, and self-concept clarity deficiency showed significant impact on it. College major satisfactions showed positive correlations, and major satisfaction showed significant impact on it. Also result shows college junior and senior students experience less career barriers compare to freshman and sophomore students, and college junior and senior students were more satisfied on the college major satisfactions as well. The study has found important implications of impacts of career barriers and college major satisfaction on career preparation behaviors. In long term, the finding of the study seem to provide useful insights for security major students and Human Resource Personnel to execute the process of career preparations and related counseling effectively.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.101-108
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• 2018

Objective: The aim of this study was to investigate gender differences in ground reaction force (GRF) components among different speeds of running. Method: Twenty men ($age=22.4{\pm}1.6years$, $mass=73.4{\pm}8.4kg$, $height=176.2{\pm}5.6cm$) and twenty women ($age=20.7{\pm}1.2years$, $mass=55.0{\pm}8.2kg$, $height=163.9{\pm}5.3cm$) participated in this study. All participants were asked to run on an instrumented dual belt treadmill (Bertec, USA) at 8, 12, and 16 km/h for 3 min, after warming up. GRF data were collected from 30 strides while they were running. Hypotheses were tested using one-way ANOVA, and level of significance was set at p-value <.05. Results: The time to passive peaks was significantly earlier in women than in men at three different running speeds (p<.05). Further, the impact loading rates were significantly greater in women than in men at three different running speeds (p<.05). Moreover, the propulsive peak at 8 km/h, which is the slowest running speed, was significantly greater in women than in men (p<.05), and the vertical impulse at 16 km/h, which is the fastest running speed, was significantly greater in men than in women (p<.05). The absolute anteroposterior impulse at 8 km/h was significantly greater in women than in men (p<.05). In addition, as the running speed increased, impact peak, active peak, impact loading rate, breaking peak, propulsive peak, and anteroposterior impulse were significantly increased, but vertical impulse was significantly decreased (p<.05). Conclusion: The impact loading rate is greater in women than in men regardless of different running speeds. Therefore, female runners might be exposed to the risk of potential injuries related to the bone and ligament. Moreover, increased running speeds could lead to higher possibility of running injuries.

• Journal of the Korean Society of School Health
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• v.4 no.1
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• pp.116-125
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• 1991

The purposes of this study are to identify the degree of exercise intent and behavior and to determine factors influencing exercise and behavior in middle school students. The subjects for this study were 658 middle school students in Chonbuk area. The data were obtained by questionaire for the period from Nov. 1 to Dec. 20, 1990. The instrument used for the study were included 6 existing scales and 2 scales developed by the researcher for this study. They are: 1) The exercise intent scale to assess the exercise plan even when they had no longer physical education. 2) The current exercise behavior to measure of exercise frequency for 1 week. 3) The scale to measure the level of self -esteem. 4) The scale to measure the level of knowledge about exercise. 5) The scale to measure the level of the perceived ability to make commitment. 6) The scale to measure the level of the perceived benifit of exercise. 7) The scale to measure the level of the perceived athletic ability. 8) The scale to measure the level of the attitude toward physical education. The data were analyzed using frequency, percentage, one way ANOVA, Pearson Coeffecients Correlation and stepwise multiple regression. The following; results were obtained. 1. Exercise intent level was in the intermediate range(mean on five point scale of 3.66, with 1 = definitely no). 2. The current exercise behavior level was relatively low(mean=1.77, with l=less than once per week and 4 = 4 or more times per week). 3. Self -esteem levels were in the intermediate range(mean on five point scale of 2.96, a mean of 5.0 indicate highest level of self-esteem.) 4. The levels of perceived ability to make commitments were in the intermediate range(mean=3.05, with 5.0 as most able). 5. The levels of perceived exercise as benificial were relatively high(mean=3.72, with 5.0 as most benificial). 6. Knowledge levels about exercise were realatively high(mean=3.97, with 5.0 as most knowledgeable). 7. The levels of perceived athletic ability were in intermediate range(mean=3.01, with 5.0 as highest score). 8. The levels of attitudes toward physical education were in the intermediate range(mean=3.29, with 5.0 as most favorable). 9. Among the general characteristic variables, sex, interest sports activities were related to the difference of exercise intent levels. 10. Of the predictor variables analyzed, self - esteem, perceived benifit of exercise, perceived athletic ability, knowledge about exercise and attitude about physical education correlated significantly and positively with exercise intent. Correlations of predictors with current exercise behavior were similiar to exercise intent, exept knowledge about exercise. 11. The stepwise multiple regression analysis shows findings as follows: 1) The most important factor to explain the difference of exercise intent was current exercise behavior. 2) The most improtant factor to explain the difference of current exercise behavior was perceived athletic ability.

• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.308-319
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• 2016

In order to evaluate the role of macrophytes as refuge of zooplankton on physical distribution (i.e. summer rainfall), we investigated the environmental factors, macrophytes, and zooplankton in waterside zones (macrophytes zones) and open water zones of 17 wetlands from May and August, 2011. In this study, a total of 51 zooplankton species were identified, and Polyarthra sp. and Diaphanosoma brachyurum were found to be the most dominant species. Waterside area of each wetland were occupied by a total of 10 macrophyte species, species composition and biomass (dry weight) were different in the survey sites. Zooplankton was more abundant in waterside zone than open water zones lacking macrophytes (One-way ANOVA, df=2, F=27.1, P<0.05), in particular, waterside zone of 1, 8, 9, 10, and 11 wetland were supported by high zooplankton density after summer rainfall. This wetlands were developed by various macrophyte species than other wetland, and submerged plant commonly presented. Waterside zones with various macrophyte species provides complexity to the habitat structure, should be utilized as refuge to avoid disturbance such as summer rainfall. The results indicate that macrophytes are the key components to enhance bio-diversity include zooplankton, and the inclusion of diverse plant species in wetland construction or restoration schemes will result in ecologically healthy food webs.