• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.139-146
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• 2009

In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. The piezoceramic shear actuation mechanism along with elastic couplings of composite blades is used for vibration reduction. The rotor blades are modeled as composite box-beams with actuator layers bonded on the outer surfaces of the thin-walled section. The governing equations of motion for helicopter blades are obtained using Hamilton's principle. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. Various rotor configurations with different elastic couplings with appropriate actuator placement are used to investigate the hub vibration characteristics. Numerical results show that a substantial reduction of $N_b$/rev hub vibration can be achieved using the optimal control algorithm.

• Journal of Technology Innovation
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• v.25 no.4
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• pp.107-143
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• 2017

This study aims to understand the impact of internal and external environments and innovation efforts on a company's performance. First, the relationships and patterns between variables were determined through an exploratory factor analysis. Afterwards, a cluster analysis was conducted, in which the influential factors summarized in the factor analysis were classified. Finally, structural equation modeling was used to carry out an empirical analysis of the structural relationship between innovation efforts and the company's performance in the classified clusters. 7 factors were derived from the exploratory factor analysis of 40 input variables from external and internal environments. 4 clusters (n=1,022) were formed based on the 7 factors. Empirical analysis of the 4 clusters using structural equation modelling showed the following: Only independent technology development had a positive impact on the company's performance for Cluster 1, which is characterized by sensitivity to a technological/competitive environment and innovativeness. Only independent technology development and joint research had positive impacts on the company's performance for Cluster 2, which is characterized by sensitivity to a market environment and internal orientation. Joint research and the mediating variable of government support program utilization had positive impacts, while the introduction of technology had a negative impact on the company's performance for Cluster 3, which is characterized by sensitivity to a competitive environment, innovativeness, and willingness to cooperate with the government and related institutions. Independent technology development as well as the mediating variables of network utilization and government support program utilization had positive impacts on the company's performance for Cluster 4, which is characterized by openness and external cooperation.

• Journal of dental hygiene science
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• v.12 no.3
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• pp.271-277
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• 2012

This study aims to figure out the effects of dental hygienists' professionalism and self-efficacy on job satisfaction using structural equations. This research conducted a survey to 616 study subjects. According to the analysis using SPSSWIN 18.0 and AMOS 20, the results are as follows : 1. It was shown that the dental hygienists' professionalism gained 3.34 points, self-efficacy was 3.76 points, and job satisfaction received 3.36 points. 2. It was found that as their age was higher, educational degree was higher, they were married, and working experience was more, their professionalism, self-efficacy, and job satisfaction were higher, which showed statistically significant difference. 3. Regarding the study model, there was positive effect as the correlation coefficient of professionalism and self efficacy was .69, that of professionalism and job satisfaction was .33, that of self-efficacy and job satisfaction was .59. In other words, there was correlation between professionalism and self-efficacy. When self-efficacy was higher than professionalism, job satisfaction also increased. Job satisfaction is affected by various environments within an organization and each individual's internal factors. The reason why job satisfaction is important is that along with the medical service quality and productivity, it is also associated with dental hygienists' individual life quality. In order to cope with this changeful time, it is needed for an organization to make efforts for change to enhance dental hygienists' job satisfaction, and also it is necessary to make endeavors so that dental hygienists can have confidence in their job and their professionalism and self-efficacy can be improved.

• Journal of KIISE
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• v.42 no.10
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• pp.1207-1221
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• 2015

This research was conducted both to analyze the determining factors of and to suggest resolution methods for the smart divide of adults over 65 years of age in the rapidly aging society of the 2000s and the smart society of the 2010s following the information society of the 1990s. The research model based on the Technology Acceptance Model (TAM) includes 6 determining factors derived from existing studies: Self Efficacy, Training, Accessibility, Playfulness, Cost Rationality, and Policy Support. Research data were collected through a survey given to a total of 243 older adults in 14 Senior Welfare Centers nationwide, and research hypotheses were verified by structural equation model (SEM) analysis. The results of this research that gives priority to the order of Political Support, Playfulness, Self Efficacy, Accessibility, Cost Rationality, and Training can be used to develop various resolution methods for the smart divide of adults over 65 years of age.

• Korean Journal of Child Education & Care
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• v.18 no.1
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• pp.27-51
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• 2018

The purpose of this study was to analyze that mother's daily hassles, children's cognitive regulation and children's emotive regulation are prospectively related on children's school readiness and to investigated the mediating role of children's cognitive regulation and children's emotive regulation between mother's daily hassles and children's school readiness. Also in particular children's sex. This study used data from 273 preschooler and their mothers from kindergartens and child care centers located in Seoul and Gyeonggi-do. The data was processed by SPSS 24.0 and Mplus 6.0. Pearson's correlation, confirmatory factor analysis(CFA), structural equation modeling(SEM), multi group analysis were used to find out the relationships and mediating effect. The results of this study were as follows: First, mother's hassles had a direct effect on children's cognitive regulation and children's emotive regulation. However, mother's hassles didn't have a direct effect on physical health and motor development, cognition development and general knowledge, social-emotional development, and life habit and attitude. Second, children's cognitive regulation had a direct effect on physical health and motor development, cognition development and general knowledge. And children's emotive regulation had a direct effect on social-emotional development. Third, children's cognitive regulation fully mediated the relation between mother's hassles and physical health and motor development, cognition development and general knowledge of school readiness. Also, children's emotive regulation fully mediated the relation between mother's hassles and social-emotional development of school readiness. Forth, mother's hassles had a little effect on boy's cognitive regulation, but boy's cognitive regulation had effect on physical health and motor development of school readiness stronger than girls.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.8-23
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• 1997

Steady and unsteady numerical simulations are conducted for the comparison with the experiments performed to investigate the ram accelerator flow field by using an expansion tube facility in Stanford University. Wavier-Stokes equations for chemically reacting flows are analyzed by fully implicit and time accurate numerical methods with Jachimowski's detailed chemistry model for hydrogen-air combustion involving 9 species and 19 reaction steps. Although the steady state numerical simulation shows a good agreement with the experimental schlieren and OH PLIF images for the case of $2H_2$＋$O_2$＋$17N_2$ fails in reproducing the combustion region behind the shock intersection point shown in the case of $2H_2$＋$O_2$＋$12N_2$ mixture. Therefore, an unsteady numerical simulation is conducted for this case and the result shows all the detailed flow stabilization process. From the result of unsteady numerical simulation, the experimental result seems to be an instantaneous state during the flow stabilization process. The combustion behind the shock intersection point is the result of a normal detonation formed by the intersection of strong oblique shocks that exist at early stage of the stabilization process. At final stage, the combustion region behind the shock intersection point disappears and the steady state result is retained. The time required for stabilization of the reacting flow in the model ram accelerator is found to be very long in comparison with the experimental test time.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.177-185
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• 1995

Gravity anomalies were recovered on a $5'\times{5'}$grid using the sea surface height data obtained from the combination of Geosat, ERS-1, Topex/Poseidon altimeter data around Korean Peninsula bounded by latitude between $30^\circ{N}\;and\;50^\circ{N}$ and longitude $120^\circ{E}\;to\;140^\circ{E.}$ In order to recover the gravity anomalies from SSH(Sea Surface Height), inverse FFT technique was applied. The estimated gravity anomalies were compared with gravity anomalies measured by shipboard around Korean Peninsula. In comparison with the differences of gravity anomaly between measured data and altimeter data, the mean and the standard deviation were found to be -0.51 mGal and 13.48 mGal, respectively. In case of comparison between the measured data and the OSU91A geopotential model, the mean and the standard deviation were found to be 11.93 mGal and 19.19 mGal, respectively. The comparison of gravity anomalies obtained from the OSU91A geopotential model and the altimeter data was carried out. The results were mean of 5.30 meal and standard deviation of 19.62 mGal. From the results, we could be concluded that the gravity anomalies computed from the altimeter data is used to the geoid computation instead of the measured data.

• Korean Journal of Childcare and Education
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• v.9 no.2
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• pp.311-330
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• 2013

This study investigated the relationships of preschool children's interactive peer play, stimulated home environment, and mother-child interaction. A total of 255 children were selected in this study. Data were analyzed with Pearson correlations and covariance structural analysis by using SPSS and AMOS, a statistical program for structural equation modeling. The major findings of this study were as follows: First, interactive peer play was associated with stimulated home environment and mother-child interaction. Second, the results confirmed the pathway from stimulated home environment via mother-child interaction to interactive peer play showing a significantly good model fit. The paths from stimulated home environment to children's interactive peer play were mediated by mother-child interaction.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.385-395
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• 2014

This study analyzes empirically main factors of willingness-to-pay for mobile IPTV emphasized as a key service in mobile environment. By structure equation analysis, the results shows that service diversity has influence on usefulness and service quality influences both usefulness and ease-to-use. Secondly, usability has positive impact on attitude and satisfaction. Thirdly, attitude and satisfaction influence willingness-to-pay. These result mean that quality assurance(ex, QoS) and improvement of usability are essential for revenue improvement revenue in mobile IPTV. And also this study can give empirical implications for service portfolio, pricing and bundling strategy as a leading study for mobile IPTV.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.426-434
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• 2008

A space averaged $SiH_4/O_2/Ar$ simulator for the high density inductively coupled plasma sources for $SiH_4/O_2/Ar$ discharge is developed. The developed simulator uses space averaged fluid equations for electrons, positive ions, negative ions, neutral species, and radicals in $SiH_4/O_2/Ar$ plasma discharge, and the electron heating model including the anomalous skin effect. Using the developed simulator, the dependency of the density of charged particles, neutral particles, and radicals, the electron temperature, the plasma resistance, and the power absorption coefficient for the RF power and pressure is calculated.