• Journal of Christian Education in Korea
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• v.63
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• pp.255-281
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• 2020

The purpose of this study was to investigate the structural relationship among self-directed learning ability, learner-instructor interaction, learner-learner interaction, and class satisfaction in online learning environments by the structural equation modelling (SEM). Participants of the study consisted of 300 students (110 = high school students, 190 = college students). Through latent mean analysis (LMA), there was no significant difference of study variables between high school and college groups. However, thorough multi-group analysis, self-directed learning ability had a direct and indirect effect on class satisfaction for the college group via learner-instructor and learner-learner interactions, while learner-learner interaction played a full mediating role of the relationship between self-directed learning ability and class satisfaction for the high school group. In addition, self-directed learning ability had a stronger influence on learner-learner interaction for the college group than the high school group. These results would provide important implications for understanding the different mechanisms between high school and college online learning contexts.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.289-302
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• 1995

The purpose of this study was to estimate the shear bond strength and observe the fractured and interfacial surfaces of various dentin bonding agents used conjunction with a visible light cured composite. The senentytwo human premolars and molars extracted due to periodontal or orthodontic reasons were used and randomely divided into six groups. All the prepared dentin surfaces were treated with Superbond D-liner, Scotchbond Multi-Purpose, All-Bond 2 and Prisma Universal Bond 3 accroding to the manufacturer's instructions. Six specimens were then demineralized in 10 % HCl for 24 hours and the other six specimens were not demineralized in order to observe the interfacial surfaces with Hitachi X-450 SEM at 25Kv. Also shear bond strength were obtained using an Instron Testing Machine with a crosshead speed of 1mm/min. The following results were obtained : 1. Although shear bond strength of Superbond D-Liner(17.35 MPa) and Scotch-bond Multi-Purpose group(17.29 MPa) were higher than the All-Bond 2(12.80 MPa) and Prisma Universial Bond 3 (13.43 MPa), there were no significant statistic differences in the shear bond strength between 4 groups.(P<0.05) As a result of etching to dentin in Prism a Universial BOND 3 experimentally, the resin tag was formed, but shear bond strength was decreased. 2. The resin tag into the opened dentinal tubule was formed in Superbond D-Liner, Scotchbond Multi-Purpose, All-Bond 2(etching) and Prisma Universial Bond 3(etching), but not in the All-Bone 2 and Prism a Universial Bond 3(non-etching). 3. Strong, durable bonds between dentin and dentinal bonding agents are essential, not only resin tag into the dentinal tubules, but also hybrid layer.

• Design & Manufacturing
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• v.13 no.1
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• pp.5-12
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• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.418-423
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• 2009

MWCNT(multi-wall carbon nanotube)-doped PEDOT:PSS(poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), used as a HIL(hole injection layer) material in OLEDs(organic light emitting diodes), was spin-coated on to the ITO glass to form PEDOT:PSS-MWCNT nano composite thin film. Morphology and transparency characteristics of nano composite thin films with respect to the loading percent of MWCNT have been investigated using FT-IR, UV-Vis and SEM. Furthermore, ITO/PEDOT:PSS-MWCNT/NPD/$Alq_3$/Al devices were fabricated, and then J-V and L-V characteristics were investigated. Functional group-incorporated MWCNT was prepared by acid treatment and showed good dispersion property in PEDOT:PSS solution. PEDOT:PSS-MWCNT thin films possessed good transparency property. For multi-layered devices, it was shown that as the loading percent of MWCNT increased, the current density increased but the luminance dramatically decreased. It might be conclusively suggested that the enhanced charge mobility by MWCNT could increase the current density but the hole trapping property of MWCNT could dramatically decrease the hole mobility in the current devices.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.113-128
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• 1995

The purpose of this study was to investigate the effect of stannous fluoride on the dentin bonding with three kinds of commercially available dentin bonding systems containing different adhesive monomers. Dentin specimens with exposed labial dentin prepared from freshly extracted bovine mandibular anterior teeth were divided into experimental and control groups. The specimens of experimental groups were bonded with dentin bonding systems and composite resins including All bond 2 ㅡ& Bisfil, Scotchbond Multi-Purpose & Z100, and Denthesive II Charisma after 2 % stannous& fluorided application for S minutes and washing for 1 minute. The specimens of control groups were bonded with the same dentin bonding systems and composite resins as used in the experimental groups. After bonded specimens were stored in $37^{\circ}C$ distilled water for 24 hours, the tensile bond strength and cohesive failure rate were measured, and then the pretreated dentin surfaces and the fractured dentin surfaces were examined under scanning electron microscope. The results were as follows : Mean bond strength of stannous fluoride applied groups of All bond 2, Scotchbond MP, and Denthesive II were 2.5MPa, 1.1MPa, and 1.1MPa respectively, and those of control groups were 7.5MPa, 8.1MPa, and 4.6MPa. Bond strength values of stannous fluoride applied groups were significantly lower than those of the control groups(p<0.05). SEM findings of dentin surfaces after stannous fluoride application demonstrated an appearance of partially remained smear layer and smear plugs inspite of pretreatment with 10 % phosphoric aicd or maleic acid solution, and an appearance of smear layer covered surface under Denthesive II priming. But those of control groups commonly showed clean dentin surfaces without smear layer and smear plugs. On SEM observation of the fractured dentin-resin interface, while most of the specimens of stannous fluoride applied groups showed adhesive failure mode, those of All bond 2 and Scotchbond MP control groups showed mainly adhesive-cohesive mixed failure mode, and mainly adhesive failure mode in Denthesive II control group.

• Journal of Multimedia Information System
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• v.7 no.1
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• pp.87-96
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• 2020

Parents' desire for daily English practice for students and the urge for a etter English education has led to a demand for a highly qualified educational curriculum. In addition to getting deep-dive insights into parents' decision-making process, the increasingly important role of STEM education method has been proved in accordance with plenty of evidenced-based many of previous research. This study was conducted to examine the five independent factors affecting parents' intentions when designating English centers for their children, respectively named: Facility, Teachers, Brands, Social factors and Tuition. Through a preliminary approach, 235 samples were analyzed. Analysis of the sample responses reveals the importance level of five independent factors affecting Parents' intention to choose English centers in descending order: Facilities, Teachers, Brands, Tuition and Social factors. Furthermore, a positive correlation was found between STEM and Intention to choose English centers, indicating that whether the center applies STEM-related curriculum in English courses or not, in fact, has a significant impact on parents' decision. In terms of attitude towards STEM, further statistical tests revealed an interesting finding, which is the fact that how STEM affects Intention of parents is directly proportional to the Attitude towards STEM. With the help of SPSS 20 and AMOS 20, the SEM analysis was processed in order to draw conclusions about factors impacting Intentions to choose English centers. Combining with Multi-group analysis, the major role of STEM education has been assessed in relation to plenty of correlations. In light of recent major and massive growth of English teaching market in Vietnam, several suggestions and recommendations in terms of sustainable developments have been displayed in this research.

• Journal of Korean Home Economics Education Association
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• v.29 no.3
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• pp.1-14
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• 2017

The purpose of this study was to investigate the relationship between parental psychological control and adolescent school adjustment mediated by hope of adolescents. Four hundred three middle and high school students participated in this study. The data were analyzed using descriptive statistics, t-tests, Pearson's correlations, structural equation modeling(SEM), and multi group analysis. The average level of school adjustment was significantly higher in male adolescent group compared to female adolescent group. Adolescents' hope partially mediated the relationship between parental psychological control and adolescents' school adjustment. The proposed model was not significantly different as a function of gender. These results suggest that adolescents' school adjustment could be improved by reducing levels of parental psychological control and enhancing adolescents' hope.

• Textile Coloration and Finishing
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• v.9 no.2
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• pp.1-9
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• 1997

This paper was carried out to introduce flame retardant and antibiotic properties to polyester(PET) and polyester/cotton(P/C) blend fabrics. PET and P/C blend fabrics were treated by a paddry-cure method in the aqueous solutions of the finishing agents(JA 6034, JA 6050, DC-5700). The corona discharge technique was applied to increase the polar group of the polymer surface. The characteristics of the treated fabric were investigated by means of scanning electron microscope (SEM) and electron spectroscopy for chemical analysis(ESCA), and water penetration time, limiting Oxygen index(LOI), and K/S value were also measured. Wettability of the fabrics was increased considerably with the corona discharge treatment. ESCA was used to elucidate the surface chemical composition of the fabrics treated with the corona discharge. Relative Ols intensity increased and oxygen was incorporated in the form of -C-O-, -C=O, and O=C-O on the polymer surface. The current study indicated that corona discharge treatment was effective for modifying the polymer surface.

• Korean Journal of Health Education and Promotion
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• v.34 no.1
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• pp.25-34
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• 2017

Objectives: Although the number of the oldest-old is rapidly increasing due to longevity, very little is known about the trajectory of depressive symptoms(DS) and its related factors among the oldest-old. Much less is known about whether the trajectory of DS differs by gender among the oldest-old. The current study aims (1) to estimate the trajectory of DS and (2) to examine whether the trajectory differs by gender among the oldest-old. Methods: Sample consists of 296 persons aged 85 and over who participated in the Korean Welfare Panel Study data. Data were processed using the latent growth curve modeling to estimate the trajectory and multi-group SEM to examine gender difference. Results: This study showed that (1) the trajectory of DS was increasing over time and (2) the DS trajectory of males was much more rapidly increasing than that of females, indicating male oldest old are more vulnerable to depression than female oldest old in later life. Conclusions: Given the fact that females are known to be more vulnerable to depression, the findings are counterintuitive to the previous knowledge on depression and gender difference. Based on the findings, implications for intervention and education related to DS among the oldest-old.

• Asia-Pacific Journal of Business
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• v.3 no.2
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• pp.8-15
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• 2012

Mobile Entertainment is the new era in mobile communication. Mobile Entertainment service is a combination of games, music, videos, chatting and telecommunication which has created a wide market in India. There is a variation between male and female customers towards Mobile Entertainment services. This study is aimed at analyzing gender impact of attitude, subjective norm, perceived behaviour control intention and behaviour towards mobile entertainment services. The Theory of planned Behaviour (TPB) provided a framework. Total 566 male and 376 female mobile users of different age groups participated in the research. The data analysis was conducted in three-stages. First, reliability tests were performed. Upon satisfactory results, confirmatory factor analysis (CFA) is used to analysis convergent, concurrent and discriminant validity of the model. Once the model was validated Structural Equation Model (SEM) Multi-group analysis is used to find the impact of gender behaviour towards Mobile entertainment services. The results of the study confirmed that the model is viable in predicting variation in gender impact on mobile entertainment services. The findings have revealed that attitude, perceived behaviour control and intention has a significant impact on behaviour to use mobile entertainment but subjective norm has no significant impact on behaviour to use mobile entertainment.