• Korean Journal of Child Education & Care
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• v.18 no.2
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• pp.203-215
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• 2018

The purpose of this study was to investigate the structural relationship among preschool children's attachments, preschool children's temperaments and children's playfulness. Participants of this study were 275 child care teachers and preschool child mother's from U-city. The collected data were analyzed by structure equation model analysis using SPSS and AMOS program. Fitness was evaluated using the ${\chi}^2$, RMSEA, NNFI, CFI, and SRMR. The results of this study were as follows. First, there was a positive correlation between preschool children's attachments and preschool children's playfulness, and a positive correlation between preschool children's temperaments and preschool children's playfulness. Second, preschool children's attachments had a significant direct effect on preschool children's playfulness and preschool children's temperaments also had a significant indirect effect on preschool children's playfulness.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.395-404
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• 2005

This paper presents a reliable numerical procedure for nonlinear time-history analysis of space steel frames subjected to dynamic loads. Geometric nonlinearities of member (P-$\delta$) and frame (P-$\Delta$) are taken into account by the use of stability functions in framed stiffness matrix formulation. The gradual yielding along the member length and over the cross section is included by using a tangent modulus concept and a softening plastic hinge model based on the New-Orbison yield surface. A computer program utilizing the average acceleration method for the integration scheme is developed to numerically solve the equation of motion of framed structure formulated in an incremental form. The results of several numerical examples are compared with those derived from using beam element model of ABAQUS program to illustrate the accuracy and the computational efficiency of the proposed procedure.

• Tribology and Lubricants
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• v.34 no.3
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• pp.107-114
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• 2018

This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.

• Journal of Korean Society of Steel Construction
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• v.27 no.5
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• pp.435-445
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• 2015

Concrete filled steel tube(CFT), which has superior ductility and strength, is used for building column, bridge piers of ocean structure. Shear design equations of CFT existing in structural design provisions are excessively conservative. It has an effect on constructability and the economics of CFT. However, to suggest the reasonable shear design equation, experimental studies on the shear capacity of CFT have been rarely conducted. This study is analytical research to suggest improved shear design equations of large-diameter concrete-filled steel tubes. This analytical research was conducted to apply finite element analysis model of CFT based on the prior research. It was verified by comparison with prior test results. The verified model was used for parameter studies to estimate the influence of overhang length, concrete compressive strength and diameter-thickness ratio on shear strength.

• Journal of Information Technology Applications and Management
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• v.26 no.6
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• pp.29-46
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• 2019

This study analyzed the factors influencing the technology acceptance of the general public in the drones and ARs, one of the key technologies of the industry 4.0. The theoretical basis was the extended unified theory of acceptance and use of technology model(UTAUT2), which uses performance expectancy, effort expectancy, social influence, facilitating conditions, and hedonic motivation as factors common to both services. The price value factor was excluded considering that most ARs were free, and the perceived risk factors, including privacy, which were not in UTAUT2, were included because they are important factors for ICT technology acceptance. The hypothesis was tested by structure equation model. Social influence and hedonic motivation had a positive(+) effect on intention to use technology. On the other hand, in the case of effort expectancy, neither the AR nor the drone had a significant influence on intention to use technology. Furthermore, performance expectancy had a positive(+) effect on intention to use in AR, but no significant influence was found out in drones. On the contrary, in the case of the facilitating conditions, the influence of the drones was positive (+), but the relation of AR was not investigated. The perceived risk was tested for the negative (-) influence of use intention of AR, but no significant relationship was found out for the drones. Among the significant influencing factors, hedonic motivation was the most powerful factor in AR and drones. Theoretical and practical implications are presented based on these results.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.377-382
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• 2001

Mechanical behavior and electrical resistance change of CPDP (carbon particle dispersed plastic) composite consisting of epoxy resin and conductive carbon particle were investigated under monotonic loading and repeated loading-unloading. The electrical resistance almost linearly increased with increasing strain during loading and the residual electrical resistance was observed even after removing load. The value of the residual electrical resistance was dependent on the maximum strain under the applied stress. This result suggests that the estimation of maximum strain (i.e., damage) is possible by the measuring electrical resistance of composite. The behavior of electrical resistance change during and after loading was discussed on the basis of the results of microscopic deformation and fracture observation. Moreover, the relationship between the volume fraction of carbon particle and the electrical resistivity of CPDP was investigated in relation to the percolation theory. Simulation model of percolation structure was established by Monte Carlo method and the simulation result was compared to the experimental results. The electrical resistance change under applied loading was analyzed quantitatively using the percolation equation and a simple model for the critical volume fraction of carbon particle as a function of the mechanical stress. It was revealed that the prediction was in good agreement with the experimental result except in the region near the failure of material.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.263-272
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• 2013

This study was conducted to look into consulting areas that can secure loyalty customers by clarifying relations between perceived quality factors, brand image and customer loyalty in terms of a multi-function printer. To accomplish the study purpose, this study carried out a validation analysis, a reliability analysis and a structural equation model analysis by setting up a study model and a hypothesis based on precedent studies and collecting data from purchase decision-makers. The findings of the study are summarized as follows. First, effects of perceived quality components of a multi-function printer on brand image were product quality, sales man's service and service quality in order of majority. Second, brand image of a multi-function printer has a positive impact on customer loyalty. This study is meaningful as it expanded the scope of study related to a multi-function printer up to the administrative field. This study is expected to help industries, who have similar business structure of a multi-function printer, establish a business strategy and support practical work and administrative consulting.

• The Journal of Information Systems
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• v.29 no.2
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• pp.95-110
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• 2020

Purpose This paper attempts to explain the recent expanding trend in Mobile Grocery Shopping(MGS). More specifically, the authors have applied the Post Acceptance Model(PAM) in order to examine the conceptual structure among the four constructs of 'Expectation Confirmation', 'Perceived Usefulness', 'User Satisfaction', and 'Continuance Intention to Use' in Mobile Grocery Shopping. Design/methodology/approach Through a survey agency, data were collected from a sample of 312 consumers who had the previous experience in Mobile Grocery Shopping. The Structural Equation Modeling(SEM) analysis was conducted with the survey data using AMOS 22.0. Subsequently, 8,200 real customer data from an open market site were collected in order to find out their revisit and repurchase behavior. Findings This study supported the causal relationships of Expectation Confirmation → Perceived Usefulness, Expectation Confirmation → User Satisfaction, Perceived Usefulness → User Satisfaction, and User Satisfaction → Continuance Intention to Use, but did not support the direct effect of Perceived Usefulness on the Continuance Intention to Use Mobile Grocery Shopping. This implies that consumers with any experience in Mobile Grocery Shopping would not consider repurchase, unless they are satisfied with the experience even though they perceive its usefulness. Also, Expectation Confirmation has much larger effect on User Satisfaction than Perceived Usefulness. In addition, the real customer data showed that the revisit and the repurchase rate of mobile grocery shoppers were higher than those of online grocery shoppers, although the rates of adding to shopping carts, coupon downloads, and adding to favorites are similar.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.17-26
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• 2014

This paper presents a dynamic crack propagation algorithm based on the Moving Least Squares(MLS) difference method. The derivative approximation for the MLS difference method is derived by Taylor expansion and moving least squares procedure. The method can analyze dynamic crack problems using only node model, which is completely free from the constraint of grid or mesh structure. The dynamic equilibrium equation is integrated by the Newmark method. When a crack propagates, the MLS difference method does not need the reconstruction of mode model at every time step, instead, partial revision of nodal arrangement near the new crack tip is carried out. A crack is modeled by the visibility criterion and dynamic energy release rate is evaluated to decide the onset of crack growth together with the corresponding growth angle. Mode I and mixed mode crack propagation problems are numerically simulated and the accuracy and stability of the proposed algorithm are successfully verified through the comparison with the analytical solutions and the Element-Free Galerkin method results.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.275-280
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• 2018

Methyl ester derived from coconut oil is very interesting to study since it contains free-fatty acid with chemical structure of medium carbon chain ($C_{12}-C_{14}$), so the methyl ester obtained from its part can be a biodiesel and another partially into biokerosene. The use of heterogeneous catalysts in the production of methyl ester requires severe conditions (high pressure and high temperature), while at low temperature and atmospheric conditions, yield of methyl ester is relatively very low. By using microwave irradiation trans-esterification reaction with heterogeneous catalysts, it is expected to be much faster and can give higher yields. Therefore, we studied the production of methyl ester from coconut oil using CaO catalyst assisted by microwave. Our aim was to find a kinetic model of methyl ester production through a transesterification process from coconut oil assisted by microwave using heterogeneous CaO catalyst. The experimental apparatus consisted of a batch reactor placed in a microwave oven equipped with a condenser, stirrer and temperature controllers. Batch process was conducted at atmospheric pressure with a variation of CaO catalyst concentration (0.5; 1.0; 1.5; 2.0, 2.5%) and microwave power (100, 264 and 400 W). In general, the production process of methyl esters by heterogeneous catalyst will obtain three layers, wherein the first layer is the product of methyl ester, the second layer is glycerol and the third layer is the catalyst. The experimental results show that the yield of methyl ester increases along with the increase of microwave power, catalyst concentration and reaction time. Kinetic model of methyl ester production can be represented by the following equation: $-r_{TG}=1.7{\cdot}10^6{_e}{\frac{-43.86}{RT}}C_{TG}$.