• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.2
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• pp.114-120
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• 2011

The characteristics of a helical turbine to be used for tidal stream energy conversion have been numerically studied with varying a few design parameters. The helical turbines were proposed aiming at mitgating the well known poor cut-in characteristics and the structural vibration caused by the fluctuating torque, and the basic concept is introducing some twisting angle of the vertical blade along the rotation axis of the turbine. Among many potential controling parameters, we focused, in this paper, on the twisting angle and the height to diameter ratio of the turbine, and, based on the numerical experiment, We tried to propose a configuration of such turbine for which better performance can be expected. The three-dimensional unsteady RANS equations were solved by using the commercial CFD software, FLUENT with k-${\omega}$ SST turbulence model, and the grid was generated by GAMBIT. It is shown that there are a range of the twisting angle producing better efficiency with less vibration and the minimum height to diameter ratio above which the efficiency does not improve considerably.

• Journal of The Korean Association For Science Education
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• v.33 no.2
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• pp.538-551
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• 2013

Korea is reported as one of the highest performing OECD countries in PISA 2009 science achievement, ranking $4^{th}{\sim}7^{th}$ among 65 participating countries. However, the top level 6 percentage came only at 1.1% and ranks $18^{th}$ among paticipating countries. Such dissatisfying results call for attention to seek effective teaching and learning strategies for top level students in Korea. This study aims to investigate the effect of reading motivational and behavioral factors on PISA 2009 science achievement for the population who scored high compared to populations scoring middle and low. For this purpose, PISA 2009 science achievement as well as students questionnaire data were utilized. Variables of reading motivational and behavioral factors were selected and structural equation modeling was employed to examine a hypothetical cause-effect relationship between reading factors and science achievement. It was found that there is a cause-effect relationship between reading factors and science achievement for the whole population. For those in the top 16% of students in PISA 2009 science achievement, reading behaviors on text-memorization have had little or no effects, while reading motivational and other behavioral factors showed a significant influence. In contrast, the middle 68% and low 16% populations have had significant effects for text-memorization on science achievement.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.64-72
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• 2017

The longitudinal dynamic instability which can occur in the fueling process of a space launch vehicle is called pogo. It is caused by coupling between the fuselage and propulsion system and they would be formed as a closed-loop system. so that the amplitude of the response may increase or decrease. In this paper, a mathematical model which is applicable to the systematic pogo analysis of a general launch vehicle is developed for an example of space shuttle. The formulations are composed of the linearized second-order differential equation for the propulsion system, and of the pressure, weight displacement, and generalized displacement. Those are important parameters for pogo analysis, are derived through eigenvalue analysis. By the formulation suggested in this paper, it is expected that mathematical modeling method of the pogo system can be obtained and systematic pogo stability analysis for any launch vehicle will be enabled.

• International Commerce and Information Review
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• v.15 no.1
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• pp.161-183
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• 2013

The essential purpose of this study is to exemplify empirically some relations of between Korea image attributes and Korea image making in Uzbekistan. This study is for providing basically empirical analysis for intensifying Korea's economic capacity based on Korean image in Uzbekistan and for offering any kinds of implications for the entry and management activities of Korean enterprises in world-wide business. This study is organized in two stages. First, the study model is designed by reappraising relevant theories, previous studies and the current investment qualifications concerning the country image attributes and image making. Second, the survey of Uzbekistan people who are living in South Korea is accomplished by collecting questionnaires. SPSS 15.0 for windows is being activated for correlation, reliability, validity and finally the statistical method of structural equation modeling is utilized to testing the hypothesis by AMOS 7.0 for windows. In conclusion partially, Korea image attributes: economic capability, popular culture, national traits and enterprise competence are proved to influence positively to Korea image making: recognition, attractiveness and confidence which is considered generally by Uzbekistan people.

• Journal of Digital Convergence
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• v.14 no.7
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• pp.155-166
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• 2016

In accordance with the increase of the importance of information security, organizations are making continuous investments to develop policies and adapt technology for information security. Organization should provide systemized support to enhance employees' security compliance intention in order to increase the degree of organization's internal security. This research suggests security policy goal setting and sanction enforcement as a method to improve employees' security compliance in planning and enforcing organization's security policy, and verifies the influencing relationship of Theory of Planned Behavior which explains employee's security compliance intention. We use structural equation modeling to verify the research hypotheses, and conducted a survey on the employees of organization with information security policy. We verified the hypotheses based on 346 responses. The result shows that the degree of goal setting and sanction enforcement has positive influence on self-efficacy and coping efficacy which are antecedents that influence employees' compliance intention. As a result, this research suggested directions for strategic approach for enhancing employee's compliance intention on organization's security policy.

• Journal of health informatics and statistics
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• v.42 no.4
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• pp.309-316
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• 2017

Objectives: Radon and its progeny pose environmental risks as a carcinogen, especially to the lungs. Investigating factors affecting indoor radon concentrations and models thereof are needed to prevent exposure to radon and to reduce indoor radon concentrations. The purpose of this study was to identify factors affecting indoor radon concentration and to construct a comprehensive model thereof. Methods: Questionnaires were administered to obtain data on residential environments, including building materials and life style. Decision tree and structural equation modeling were applied to predict residences at risk for higher radon concentrations and to develop the comprehensive model. Results: Greenery ratio, impermeable layer ratio, residence at ground level, daily ventilation, long-term heating, crack around the measuring device, and bedroom were significantly shown to be predictive factors of higher indoor radon concentrations. Daily ventilation reduced the probability of homes having indoor radon concentrations ${\geq}200Bq/m^3$ by 11.6%. Meanwhile, a greenery ratio ${\geq}65%$ without daily ventilation increased this probability by 15.3% compared to daily ventilation. The constructed model indicated greenery ratio and ventilation rate directly affecting indoor radon concentrations. Conclusions: Our model highlights the combined influences of geographical properties, groundwater, and lifestyle factors of an individual resident on indoor radon concentrations in Korea.

• Journal of the Korea Society of Computer and Information
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• v.24 no.11
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• pp.87-98
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• 2019

In recent years, many organizations protect their information resources by investing in information security technology. However, information security threats from insiders have not been reduced. This study proposes a method for reducing information security threats within an organization by mitigating negative information security behaviors of employees. Specifically, the study finds a relationship between information security related role stress and negative behavior and suggests whether organizational justice mitigates role stress. That is, the purpose of the study is to suggest a mechanism between organizational justice, information security related role stress, and negative behavior. Negative behavior consist of avoidance behavior and deviant behavior, and security related role stress consist of role conflict and role ambiguity. Organizational justice consist of distributional justice, procedural justice, and informational justice. The research model is verified through structural equation modeling. After establishing a research model and hypothesis, we develop a survey questionnaire and collect data from 383 employees whose organizations have already implemented security policies. The findings appear that security related role stress increases negative behavior and that organizational justice mitigates role stress. The results of the analysis suggest the direction of organizational strategy for minimizing insider's security-related negative behaviors.

• Journal of the Korea Convergence Society
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• v.12 no.8
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• pp.229-243
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• 2021

As systematic information protection and management is recognized as an organization's core value, organizations are pursuing a shift from an individual-centered information management method to an organization-oriented information management method. The Enterprise content management system(ECMS) is a solution that supports document security and information sharing by insiders and is being introduced by many organizations due to recent technological developments. The purpose of this study is to present a method of improving performance through continuous use of the ECMS from the user's point of view and also suggest a method to improve the intention of continuous use through the expansion of the technology acceptance model. This study surveyed the employees of organizations that adopted the ECMS and verified the research hypothesis derived from previous studies through structural equation modeling. As a result of the analysis, usefulness, and ease of use affected on the intention of continuous use of the ECMS, and the knowledge sharing culture and the ECMS quality factors affected the technology acceptance model factors. The results of this study have academic and practical significance in terms of suggesting a plan to increase the usability of the ECMS from the user's point of view.

• Korean Journal of Culture and Social Issue
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• v.24 no.4
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• pp.519-539
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• 2018

This study investigates the impact of organizational socialization tactics on newcomers' organizational citizenship behaviors. We explains this relationship with the concept of perceived organizational support, which refers to the extent to which individuals perceive that the organization recognizes their contributions and takes care of their well-being. We expect that the more institutionalized the organization's socialization tactics are, the more organizational support individuals perceive, consequently increasing the performance of organizational citizenship behaviors. We performed a survey targeting 450 newcomers in domestic companies, and adopted 382 data for path analyses based on the structural equation modeling. As the result, in all the three dimensions of socialization tactics (content, context, social), the extent to which socialization tactics are institutionalized is positively related to the perception of organizational support. It also has the positive relationship with individuals' organizational citizenship behaviors, being fully mediated by the perceived organizational support. More specifically, context socialization tactics shows the highest level of impact both on the perceived organizational support and organizational citizenship behaviors, whereas social tactics has the lowest level of impact. These results imply that the range of effects the organizational socialization has on the newcomers' attitudes and behaviors should be more extended and detailed.

• Journal of Digital Convergence
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• v.21 no.3
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• pp.1-14
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• 2023

This raises the question of how competitive advantage can be created, prompting firms to enhance their capacity for change. In this context, the role of knowledge creation becomes increasingly vital. This research aims to explore the role of intellectual capital and how to improve knowledge cration ability through absorptive capacity framework. It examines the links among knowledge acquisition, learning of new knowledge, knowledge creation, intellectual capital, and competitive advantage, drawing from both internal and external sources. The study focuses on small and medium-sized supplier firms in Korea, with data collected from 15 industries, totaling 106 responses. The research model employs structural equation modeling (SEM) and utilizes AMOS 22 for analysis. As anticipated, all hypotheses were supported. The study provides robust evidence that absorptive capacity is a pivotal factor in cultivating suppliers' competitive advantage. Furthermore, it posits that intellectual capital should be viewed as a criucial component of suppliers' knowledge stock, significantly enhancing the impact of absorptive capacity on their competitive edge. Future studies should aim to validate the research model in different international settings or across multinational corporations to enhance its generalizabulity.