• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.239-247
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• 2013

Recently renewable energy such as offshore wind energy takes a higher interest due to the depletion of fossil fuel and the environmental pollution. This paper deals with multi-body dynamics (MBD) analysis technique for offshore wind turbine system considering aerodynamic loads and Thevenin equation used for determination of electric generator torque. Dynamic responses of 5MW offshore wind turbine system are evaluated via the MBD analysis, and the system is the horizontal axis wind turbine (HAWT) which generates electricity from the three blades horizontally installed at upwind direction. The aerodynamic loads acting on the blades are computed by AeroDyn code, which is capable of accommodating a generalized dynamic wake using blade element momentum (BEM) theory. In order that the characteristics of dynamic loads and torques on the main joint parts of offshore wind turbine system are simulated similarly such an actual system, flexible body modeling including the actual structural properties are applied for both blade and tower in the multi-body dynamics model.

• 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.

• Smart Structures and Systems
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• v.25 no.4
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• pp.487-499
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• 2020

This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.206-225
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• 2016

This study analyzes the effect of authentic leadership on organizational climate, organizational citizenship behavior, and job performance to suggest the implications behind the growing importance of authentic leadership. In particular, this study substantiates existing arguments that organizational climate moderates the tension between leaders and employees by investigating the mediating effects of organizational climate on the relationship between authentic leadership and job performance. A survey was conducted on employees of various business areas in Korea, and 444 responses were used in statistical analysis which was performed using SPSS/WIN 24.0 and STATA 14.0 statistics package and verified using structural equations. The analysis results showed that 1) authentic leadership has positive effects on organizational climate, organizational citizenship behavior, job performance; 2) organizational climate has positive effects on organizational citizenship behavior and job performance; 3) organizational citizenship behavior has a positive effect on job performance; and 4) organizational climate performs a mediating role in the relationships among authentic leadership, organizational citizenship behavior, and job performance. By including organization climate's mediating effect as a factor in the research on authentic leadership, this study presents a new perspective for future studies on leadership.

• The Journal of the Korea Contents Association
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• v.16 no.6
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• pp.135-150
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• 2016

This study aims to investigate how perceived interactivity between the mobile messenger application and its user gives rise to user's enjoyment and continuous usage intention. Perceived interactivity was assumed to be formed by the combination of control, share, and responsiveness in light of the previous studies. The relations between perceived interactivity, enjoyment, and usage intention are hypothesized on the basis of the pleasure-arousal-dominance emotional state model, the theory of reasoned action, and the theory of planned behavior. Survey data were collected from 481 mobile messenger users in Korea and China. In order to test hypotheses, structural equation modeling analyses were conducted. As a result, perceived interactivity concerning connectedness and responsiveness not only positively affected enjoyment, but also had a significant effect on usage intention. However, while control positively influenced usage intention, it was not significantly related to enjoyment. In addition, there was a positive relation between enjoyment and usage intention. Incidentally, multi-group analysis was conducted to explore the differences between Korean and Chinese users. The findings would provide managerial implications for mobile messenger corporations on causal effects of perceived interactivity and the differences of the path coefficients between in Korea and China.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.512-519
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• 2007

The purpose of this study is to investigate the potential of a novel tissue engineering approach to regenerate intervertebral disc. In this study, thermosensitive scaffold (chitosan-Pluronic hydrogel) and nanofiber were used to replace the nucleus pulposus (NP) and annulus fibrosus of a degenerated intervertebral disc, leading to an eventual regeneration of the disc using the minimally invasive surgical procedure and organ culture. In preliminary study, disc cells were seeded into the scaffolds and cellular responses were assessed by MTT assay and scanning electron microscopy (SEM). Based on these results, we could know that tissue engineered scaffolds might provide favorable environments for the regeneration of tissues. Organ culture was performed in fresh porcine spinal motion segments with endplates on both sides. These spinal motion segments were classified into three groups: control (Intact), injured NP (Defect), and inserting tissue engineered scaffolds (Insert). The specimens were cultivated for 7 days, subsequently structural stability, cell proliferation and morphological changes were evaluated by the relaxation time, quantity of DNA, GAG and histological examination. In these results, inserting group showed higher relaxation time, reduced decrement of DNA contents, and accumulated GAG amount. Consequently, the tissue engineered scaffolds used in this study seen to be a promising base scaffolds for regenerative intervertebral disc due to its capacity to absorb external dynamic loading and the possible ideal environment provided for disc cell growing.

• 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 Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.448-458
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• 2017

This study reviews the literature related to the omni-channel and derived structural relationship between experiential perception of omni-channel brand and consumer-brand relational quality. A total of 250 questionnaires were distributed to university students, workers, and consumers in Busan, Korea, who had experience using SSG.com. 210 questionnaires were used for final validation of research model. The hypotheses set in this study was validated through SPSS18.0 and LISREL8.3 based on the research model. The results showed that all hypotheses were accepted, except for 2 hypotheses(Hypothesis 2-3, Hypothesis 2-4). Findings of this study suggest the following:First, the consumer's experience with the omni-channel brand was found to be an important factor influencing consumers' cognitive and emotional responses formed by the transfer effect of experiential factors through senses. Second, the relationship between consumers and the omni-channel brand was found to be an important factor in building attachment and psychological bond through experience and trust for the omni-channel brand. Thus, the results of this study provide the basis for overall understanding of the strategic experiential module (SEMs) for the omni-channel, which recently emerged as a new trend of distribution channel, as well as for managing the spatial environment. Finally, we present the theoretical and practical implications related to consumers' experience and relational perception.

• The Korean Journal of Pesticide Science
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• v.2 no.2
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• pp.53-58
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• 1998

For evaluating the mutagenic potential of 2-carbomethoxy-4-chlorodiethyl phosphate, three different short-term mutagenicity tests were used; Salmonella typhimurium preincubation assay with and without rat liver microsomal activation, chromosome aberration test in cultured chinese hamster lung fibroblast cell and in vivo micronucleus test in male mice bone marrow. In Salmonella typhimurium reverse mutation assay using TA98, TA100, TAl535 and TAl537, 2-carbomethoxy-4-chlorodiethyl phosphate did not show any mutagenic response in the presence and absence of S9 mix. It did not induce any significant structural chromosome aberrations in the absence of metabolic activation. In micronucleus test using ICR mice, the frequency of micronucleated polychromatic erythrocytes (MNPCE) increased in bone marrow cells treated with positive control, mitomycin-C, but 2-carbomethoxy-4-chlorodiethyl phosphate did not increase micronucleated polychromatic erythrocytes. These results indicate that 2-carbomethoxy-4-chlorodiethyl phosphate does not show any positive responses in short-term genotoxicity assays.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.179-186
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the developemnt could be easily neglected.