• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.433-443
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• 2023

The current paper discusses the dynamic and stability responses of cross-ply composite laminated plates by employing a refined quasi-3D trigonometric shear deformation theory. The proposed theory takes into consideration shear deformation and thickness stretching by a trigonometric variation of in-plane and transverse displacements through the plate thickness and assures the vanished shear stresses conditions on the upper and lower surfaces of the plate. The strong point of the new formulation is that the displacements field contains only 4 unknowns, which is less than the other shear deformation theories. In addition, the present model considers the thickness extension effects (ε_z≠0). The presence of the Winkler-Pasternak elastic base is included in the mathematical formulation. The Hamilton's principle is utilized in order to derive the four differentials' equations of motion, which are solved via Navier's technique of simply supported structures. The accuracy of the present 3-D theory is demonstrated by comparing fundamental frequencies and critical buckling loads numerical results with those provided using other models available in the open literature.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.295-310
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• 2022

This paper proposes a modified bar simulation method for analyzing the shear lag effect of variable sectional box girder with multiple cells. This theoretical method formulates the equivalent area of stiffening bars and the allocation proportion of shear flows in webs, and re-derives the governing differential equations of bar simulation method. The feasibility of the proposed method is verified by the model test and finite element (FE) analysis of a simply supported multi-cell box girder with constant depth. Subsequently, parametric analysis is conducted to explore the mechanism of shear lag effect of varied sectional cantilever box girder with multiple cells. Results show that the shear lag behavior of variable box-section cantilever box girder is weaker than that of box girder with constant section. It is recommended to make the gradient of shear flow in the web with respect to span length vary as smoothly as possible for eliminating the shear lag effect of box girder. An effective countermeasure for diminishing shear lag effect is to increase the number of box chambers or change the variation manner of bridge depth. The shear lag effect of varied sectional cantilever box girder will get more server when the length of central flanges is shorter than 0.26 or longer than 0.36 times of total width of top flange, as well as the cantilever length exceeds 0.29 times of total length of box's flange. Therefore, the distance between central webs can adjust the shear lag effect of box girder. Especially, the width ratio of cantilever plate with respect to total length of top flange is proposed to be no more 1/3.

• The Journal of Economics, Marketing and Management
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• v.11 no.5
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• pp.69-80
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• 2023

Purpose: The purpose of this study is to identify factors that affect decision-making for e-commerce users and to present ecommerce companies with the company's strategic directions for consumer purchases. Research design, data, and methodology: In this study, a structured research model was derived to confirm the relationship between brand image, product liking, heuristic and purchase intention and the difference according to psychological power. For analysis a total of 212 valid questionnaires from e-commerce users were used. confirmatory factor analysis, correlation analysis, and structural equations were conducted to verify. Results: Both brand image and product liking had a significant effect on purchase intention as well as heuristics. However, heuristics did not affect the purchase intention. It was found that the relationship between brand image, product liking, heuristic, and purchase intention differed depending on the psychological power. Conclusions: Companies should seek ways to increase the positive brand image and likability of products so that consumers can quickly purchase products. In the relationship between brand image and heuristic, the low-psychological group has more influence on heuristic, and in case of product liking, the high-psychological group has more influence on heuristic. In the relationship between brand image and product liking for purchase intention, both in the high psychological power group affect more influence on purchase intention. Since the process of purchasing products varies depending on the consumer psychological power tendency, it is necessary to identify the characteristics of consumers and establish strategies for purchasing promotion measures.

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.225-238
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• 2024

In this paper, a quasi-3D hyperbolic shear deformation theory for the bending responses of a functionally graded (FG) porous micro-beam is based on a modified couple stress theory requiring only one material length scale parameter that can capture the size influence. The model proposed accounts for both shear and normal deformation effects through an illustrative variation of all displacements across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the micro-beam. The effective material properties of the functionally graded micro-beam are assumed to vary in the thickness direction and are estimated using the homogenization method of power law distribution, which is modified to approximate the porous material properties with even and uneven distributions of porosity phases. The equilibrium equations are obtained using the virtual work principle and solved using Navier's technique. The validity of the derived formulation is established by comparing it with the ones available in the literature. Numerical examples are presented to investigate the influences of the power law index, material length scale parameter, beam thickness, and shear and normal deformation effects on the mechanical characteristics of the FG micro-beam. The results demonstrate that the inclusion of the size effects increases the microbeams stiffness, which consequently leads to a reduction in deflections. In contrast, the shear and normal deformation effects are just the opposite.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.325-334
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• 2008

The standard prestressed concrete I-girder bridge (PSC I-girder bridge) is one of the most prevalent types for small and medium bridges in Korea. When determining the member forces in a section to assess the safety of girder in this type of bridge, the general practice is to use the simplified practical equations or the live load distribution factors proposed in design standards rather than the precise analysis through the finite element method or so. Meanwhile, the live load distribution factors currently used in Korean design practice are just a reflection of overseas research results or design standards without alterations. Therefore, it is necessary to develop an equation of the live load distribution factors fit for the design conditions of Korea, considering the standardized section of standard PSC I-girder bridges and the design strength of concrete. In this study, to develop an equation of the live load distribution factors, a parametric analysis and sensitivity analysis were carried out on the parameters such as width of bridge, span length, girder spacing, width of traffic lane, etc. As a result, the major variables to determine the size of distribution factors were girder spacing, overhang length and span length in case of external girders. For internal adjacent girders, the determinant factors were girder spacing, overhang length, span length and width of bridge. For internal girders, the factors were girder spacing, width of bridge and span length. Then, an equation of live load distribution factors was developed through the multiple linear regression analysis on the results of parametric analysis. When the actual practice engineers design a bridge with the equation of live load distribution factors developed here, they will determine the design of member forces ensuring the appropriate safety rate more easily. Moreover, in the preliminary design, this model is expected to save much time for the repetitive design to improve the structural efficiency of PSC I-girder bridges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.474-481
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• 2018

The purpose of this study was to examine the mediating effects of maternal family experience on the relationship between mothers' tendency to addicted to smartphones and the social competence of young children. The subjects of this study were 481 mothers who delivered infants to a kindergarten or daycare center in Jeju area After conducting the questionnaire, the results of the responses were analyzed. To analyze the collected data, structural equations were implemented using SPSS Statistic 18.0 program. The results of this study are summarized as follows. First, the correlational analysis showed that the tendency of the addiction of smartphone and the social ability of the infant showed a significant correlation with the mother's family experience. Second, in the relationship between the mother's smartphone tendency and the social competence of the infant, The research model and the competition model were set up to examine the mediating effect and the competition model was found to be more appropriate. As a result, it can be seen that mother's original family experience is partly mediated in relation to mother's tendency to add to smartphone and social competence of infant. Based on these results, the implications of this study and suggestions for subsequent research were discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.236-243
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• 2018

The purpose of this study was to investigate the mediating effects of parental attachment and ego resiliency in the tendency toward social networking site (SNS) addiction in college students. For this purpose, 382 college students in the Jeju area were surveyed and their responses analyzed. To analyze the collected data, structural equations were implemented using SPSS Statistics version 18.0. According to the results of the study, there is a significant negative correlation between attachment formation and SNS intoxication in college students, and a negative correlation between ego resiliency and SNS addiction. Also, there is a significant positive correlation between formation of parental attachment and ego resiliency in college students, indicating that parental attachment and ego resiliency are significant factors in lowering SNS addiction. Second, in order to examine the mediating effects of ego resiliency in the relationship between the formation of parental attachment and SNS addiction in college students, a research model and a competition model were established and verified. As a result, the relationship between parent attachment and SNS addiction was mediated completely, and the research model is more appropriate. These findings suggest that ego resiliency is of practical significance in seeking ways to improve the problem of SNS addiction in the future. In other words, overuse of SNSs by university students can lead to addiction, but strengthening ego resiliency enables sound SNS use.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.63-67
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• 2014

Fischer-Tropsch synthesis mainly produces a wax which is a viscous liquid for long carbon chain. When a catalytic fixed-bed reactor is used for Fischer-Tropsch synthesis, the wax generated on a catalyst surface can keep adsorbing on the catalyst surface. This liquid hold-up causes significant pressure drop and clogging problems through the reactor. Thus, the model for liquid hold-up is required to design the size of reactor and catalyst particles. In this study, the liquid hold-up model considering structural and operational conditions was proposed based on empirical equations for convective mass transfer between the syngas flow and the wax-adsorbed catalyst. The developed model was validated by comparing with the experimental data from Knochen's work (2010). The influence of reactor length and coross section on the wax hold-up in reactor were analyzed and the optimal reactor size were proposed.

• Informatization Policy
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• v.29 no.1
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• pp.60-83
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• 2022

The purpose of this study is to empirically analyze the effect of individual perception of artificial intelligence and the level of digital literacy on the acceptance of artificial intelligence-based public services. For empirical analysis, a research model was set up based on the technology acceptance model and planned behavior theory using survey data of 2017 and analyzed through structural equations. To summarize the results of the analysis, firstly, the positive perception of individuals about artificial intelligence technology plays a role in reinforcing attitudes toward benefits and reducing concerns about public service in which artificial intelligence technology has been introduced. Secondly, the level of digital literacy reinforces both benefits and concerns about artificial intelligence technology, but it was found that the intention to use public services was reinforced through the benefits of artificial intelligence technology perceived by individuals, rather than privacy concerns about artificial intelligence technology. Thirdly, it was confirmed that the perceived benefits of individuals on artificial intelligence technology reinforced the intention to use public civil services, and privacy concerns negatively influenced the intention to use. It was confirmed that the influence of a perceived ease of use and usefulness, as opposed to privacy concerns, further reinforces the intention to use. Both citizens' positive perceptions regarding the accuracy and reliability of information provided through artificial intelligence technology and institutional complementation of responsibility for errors caused by artificial intelligence technology are strengthened, and technical problems related to privacy protection are solved.

• Information Systems Review
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• v.25 no.1
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• pp.165-187
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• 2023

The continuous increase in life expectancy and high interest in health has brought about significant changes in the use of health information by the public according to the development of information technology represented by the Internet and smartphones. As the medical market expands to the mobile health environment, many health-related apps have been created and distributed, but the acceptance rate is slow as it has become challenging to provide services due to various regulations. In this study, perceived value, perceived risk factors (psychological risk, risk of time-loss, legal risk), and perceived benefits (usefulness, interaction, autonomy) were derived and verified as factors that affect the acceptance resistance of personal health record apps based on the privacy calculation model. In addition, by analyzing the moderating effect of trust in the manufacturer, how the perceived risk and perceived benefit affect the perceived value was verified. A survey was conducted on Korean college students who recognized the personal health record apps but did not use them, and 127 samples were analyzed using structural equations. As a result of hypothesis verification, perceived value has a negative effect on acceptance resistance, perceived risk (risk of time-loss) has a negative effect on perceived value, and perceived benefits (usefulness, interaction, autonomy) were found to have a positive effect on perceived value. Trust in manufacturers has weakened the impact of perceived risks (legal risk) on perceived values. This study is expected to play an important role in maintaining a competitive advantage in the personal health record app market environment by identifying and proposing detailed criteria for reducing the acceptance resistance of personal health record apps.