• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.2
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• pp.88-92
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• 2006

We present a microfluidic system with microvalves and a micropump that are easily integrated on the same substrate using the same fabrication process. The fabricated microfluidic system is suitable for use as a disposable device and its characteristics are optimized for use as a micro chemical analysis system (micro-TAS) and lab-on-a-chip. The system is realized by means of a polydimethylsiloxane (PDMS)-glass chip and an indium tin oxide (ITO) heater. We demonstrate the integration of the micropump and microvalves using a new thermopneumatic-actuated PDMS-based microfluidic system. A maximum pumping rate of about 730 nl/min is observed at. a duty ratio of 1 $\%$ and a frequency of 2 Hz with a fixed power of 500 mW. The measured power at flow cut-off is 500 mW for the microvalve whose channel width, depth and membrane thickness were 400 $\mu$m, 110 $\mu$m, and 320 $\mu$m, respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.1
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• pp.27-36
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• 1998

A three-dimensional numerical model of water circulation has been developed. The model employs the equations on $\sigma$-coordinate and the finite element method for numerical integration. To verify accuracy of the model, a series of numerical experiments have been conducted. The experiments include wind-driven currents in an one-dimensional channel, wind-driven currents in a square lake, and tidal current distributions in Masan-Jinhae Bay. The simulation results showed good agreements with the analytic solutions for wind-driven current and the field data sets in Masan-Jinhae Bay. The model can be used widely for modeling of water circulation in the waters with a complex geometry.

• Steel and Composite Structures
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• v.25 no.6
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• pp.727-734
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• 2017

This paper describes a quasi-static finite element analysis, which uses the explicit integration method, of the apex joint of a cold-formed steel portal frame. Such cold-formed steel joints are semi-rigid as a result of bolt-hole elongation. Furthermore, the channel-sections that are being connected have a reduced moment capacity as a result of a bimoment. In the finite element model described, the bolt-holes and bolt shanks are all physically modelled, with contact defined between them. The force-displacement curves obtained from the quasi-static analysis are shown to be similar to those of the experimental test results, both in terms of stiffness as well as failure load. It is demonstrated that quasi-static finite element analysis can be used to predict the behavior of cold-formed steel portal frame joints and overcome convergence issues experienced in static finite element analysis.

• Advances in Energy Research
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• v.3 no.2
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• pp.81-95
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• 2015

Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.705-707
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• 2014

The vehicle network such as CAN, MOST, Ethernet has different protocols. In the case of Ethernet data, when data is transmitted from Ethernet to MOST150, it cannot be treated by Ethernet channel of MOST150, leading to data loss and transmission delays. Thus, this thesis proposes vehicle integration GATEWAY, which can form a network by organically connecting the Ethernet and MOST150 networks and minimize the delay and data losses caused by the differences in bandwidth.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5588-5613
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• 2018

Virtualization technology has been widely applied in the area of computer security research that provides a new method for system protection. It has been a hotspot in system security research at present. Virtualization technology brings new risk as well as progress to computer operating system (OS). A multi-level perception security model using virtualization is proposed to deal with the problems of over-simplification of risk models, unreliable assumption of secure virtual machine monitor (VMM) and insufficient integration with virtualization technology in security design. Adopting the enhanced isolation mechanism of address space, the security perception units can be protected from risk environment. Based on parallel perceiving by the secure domain possessing with the same privilege level as VMM, a mechanism is established to ensure the security of VMM. In addition, a special pathway is set up to strengthen the ability of information interaction in the light of making reverse use of the method of covert channel. The evaluation results show that the proposed model is able to obtain the valuable risk information of system while ensuring the integrity of security perception units, and it can effectively identify the abnormal state of target system without significantly increasing the extra overhead.

• Research in Community and Public Health Nursing
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• v.32 no.1
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• pp.12-23
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• 2021

Purpose: This study explored how and why young and middle-aged adults disclose depressive feelings to others. In particular, we investigated the role of social norms to see whether using mobile instant messaging (MIM) could lower the perceived barriers of emotional disclosure. Furthermore, the motivations of emotional disclosure via MIM were compared between young and middle-aged adults. Methods: A total of 255 Koreans (128 middle-aged people, 127 young adults) participated in an online survey. Pearson's correlation coefficients, paired t-tests, SPSS PROCESS macro, and exploratory factor analysis were used to examine the relationships among the key variables. Results: The perceived social norms were found to be a significant deterrent in disclosing depressive feelings to others. However, there was a significant interaction effect between generations and perceived social norms. Although young adults with low social norm awareness were more likely to disclose depressive feelings via MIM, emotional disclosure among middle-aged adults increased with higher levels of perceived social norms. Also, different motivations were observed. Conclusion: The results confirmed the significant effect of social norms as well as generational differences when using MIM as a channel of emotional disclosure.

• Journal of Distribution Science
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• v.20 no.3
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• pp.95-106
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• 2022

Purpose: This study aims to verify the effects of omnichannel characteristics on pleasure, resistance and repurchase intention in the omnichannel situation in order to provide the innovative commercial business. Research design, data and methodology: The study examined relations between research concepts centered on previous studies, set hypotheses, developed a research model, and verified the model through a questionnaire survey. A total of 297 questionnaires were used for the final analysis, excluding the questionnaires showing insincere or outliers. Results: First, Omnichannel showed multi-dimensional characteristics consisting of consistency, innovation, economy, and integration. Second, innovation and economic feasibility had a positive effect on pleasure. Third, only economic feasibility had a negative effect on user resistance. Fourth, consumers' shopping pleasure had a negative effect on user resistance. Fifth, repurchase intention of consumers was positively affected by innovation. Conclusions: This research contributed to extend academic framework of distribution research by examining causal relationship through adoption of economic and innovation factors as new characteristics from the integrated perspective beyond the research frame of the existing omnichannel distribution environment. Companies should provide meaningful experiences by resolving concerns about side effects caused by human-computer interaction and providing smart information that matches the products most suitable for consumer needs.

• Journal of Distribution Science
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• v.13 no.9
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• pp.81-93
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• 2015

Purpose - "Showrooming" refers to the phenomenon where a shopper visits a store to see and compare products but makes the purchase online at a lower price. Surveys on showrooming activities at home and abroad indicate that a significant number of consumers pursue showrooming activities. The advent of "showroomers," who engage in buying activities, hovering both on and offline, while selectively choosing sales channels to suit their needs, is powerful enough to erode the borders between channels and bring about seismic changes in the distribution industry. However, surprisingly, there has been no in-depth discussion on showrooming. This study seeks to theoretically investigate what impact personal characteristics have on showrooming preferences and attitudes in a multi-channel environment. Specifically, assumptions have been made that price perception, perceived performance risk, and trust in online shopping not only have a direct impact on showrooming attitudes but also indirectly affect it through the means of contact motivation. Research design, data, and methodology - To test the hypotheses, this study conducted a survey of male and female shoppers, ages 20 through 40s, who live in metropolitan areas, and have actively showroomed fashion items in the last six months. A clothing item usually purchased after a careful decision-making process was chosen as the target product of the study. The survey was conducted between October and November 2014, using a professional survey service provider. A total of 200 surveys were collected, of which 198 were used for analysis. Conceptual model Structural Equation Modeling (SEM) and Amos 18.0 were employed for data analysis and model verification. In addition, following the confirmatory factor analysis and measurement model analysis, the theoretical model that corresponds to the research model was analyzed. Results - Analysis results show that price perception, perceived performance risk, and trust in online shopping have a statistically significant and positive (+) impact on showrooming attitudes. In addition, in terms of the indirect influence of price perception and perceived performance risk on showrooming attitudes through means of contact motivation, price perception had a statistically significant and positive impact on means of contact motivation, whereas perceived performance risk did not have a statistically significant impact on it, with the relevant hypothesis rejected. Conclusions - These analysis results imply that the ultimate goal of consumers is to maximize their shopping benefits by selectively and strategically taking advantage of different channels in a complementary manner. This study presents many implications for distributors to encourage a deep understanding of showrooming consumers who have complicated consumption behaviors and to build channel integration strategies. This study has limitations in theoretical and practical implications. Therefore, subsequent studies need to focus on verifying that showrooming activities are based on reasonable and planned decisions by applying the theory of reasoned or planned behavior. In addition, the scope of the study should expand to include web showrooming, where consumers conduct product research online and purchase offline.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.376-381
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• 2018

The purpose of this study is to investigate price transmissions between wholesale and retail markets regarding Jeju tangerines by employing co-integration analysis and vector error correction model. The results of this study are summarized as follows: First, the long-run equilibrium relationship was found among wholesale and retail markets in time series for level by distribution channel. Second, a short-run causality relationship was observed between wholesale and retail markets. Third, the long-run causality relationship between wholesale market and retail markets was found bidirectional and feedback effect. These results imply that the wholesale price performs a central role in establishing price in the tangerine market, and the wholesale market influences tangerine price. In conclusion, for the development of a competitive tangerine industry, it is necessary to aggressively promote the policy of supply and demand control of tangerine production through organizing producers.