• Journal of Korea Society of Industrial Information Systems
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• v.8 no.2
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• pp.84-91
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• 2003

KOMPSAT series use software-controlled unregulated bus system in which the main bus is directly connected to a battery and the duty-ratio for PWM switch is controlled by the on-board satellite software. This paper proposes a new power-stage circuit that can be available for modularization of the power regulator which is used at the software-controlled unregulated bus system satellite. And we analyze the proposed power-stage operation according to its operating modes and verify it by performing software simulation and hardware experiment using prototype. We construct a parallel-module converter which is composed of proposed power-stages and perform experiment to verify modular characteristics of the proposed power-stage. Finally, we verify the usefulness of the proposed power-stage by comparing above results with those of a parallel-module converter made of conventional power-stages.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.678-690
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• 2014

The current networks do not disclose information about a management domain due to scalability, manageability and commercial reasons. Therefore, it is very hard to calculate an optimal path to the destination. Also, due to poor information sharing, if an error occurs in the intermediate path, it is very difficult to re-search the path and find the best path. Hence, to manage each domain more efficiently, an architecture with top-level path computation node which can obtain information of separate nodes are highly needed This study aims to investigate a federation of a united network around NRN(National Research Network) that could allow resource sharing between countries and also independent resource management for each country. Considering first the aspects that can be accessed from the perspective of a national research network, ICE(Information Control Element) and GFO(Global Federation Organizer)-based architecture is designed as a top-level path computation element to support traffic engineering and applied to the multi-domain network. Then, the federation for the independent management of resources and resource information sharing among national research networks have been examined.

• Journal of Information Technology Applications and Management
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• v.10 no.3
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• pp.1-22
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• 2003

P2P systems have been studied by many researchers in universities and commercial firms in recent years. In this study. we design and implement a system that makes UP for shortcomings of currently available P2P systems. Gnutella and Napster. The study also includes an efficiency analysis scheme conducted through a series of experimental data. The data sharing system of the study demonstrated duality of roles(client, service) of peers. But, their roles were separated from the existing client-server systems. Also, the study implements mechanism that shows the redundancy of data to communicate efficiently among peers for transferring data. The results of performance measure of the system shows that the amount of information shared by peers increases as the amount of peers increases but with no significant increase in response time. This constant response time is far more stable and faster than current file sharing systems. such as Gnutella and Napster. Business applications such as knowledge management, enterprise information portal management and transfer of data are done by use of supercomputers. They need to extend their systems to equip with more capacity and throughput as the number of clients increases. Moreover, they will face with more complicated problems if integration with new systems exists. If this JDSS is introduced to these business applications. it would easily augment scalability of the system with high performance at less expense.

• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.411-424
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• 2018

Purpose: The purpose of this study is to improve submarine TACM launcher system safety device performance. Methods: In this study, EPLD(Electrically Programmable Logic Device) control and time sharing method to the safety device actuator motor and discrete signal processor in launch control panel were used to resolve unusual performance of safety system. Results: The result of this study are as follows; First, sporadic stopping of safety device actuator motor due to insufficient In-Rush current was resolved. Second, repeat of safety device condition as lock & release due to chattering for motor activating was resolved. Third, simultaneous release function for safety device actuator was available. Conclusion: The unusual performance of function for submarine TACM launcher system was overcame by applying EPLD control and time sharing method. The suggestions were proved by performance test in the pressure chamber. The results of this study enhanced survivability of ${\bigcirc}{\bigcirc}{\bigcirc}$ class submarine from enemy torpedo.

• Journal of information and communication convergence engineering
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• v.9 no.3
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• pp.325-330
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• 2011

Due to the wide growth and popularity of social network website, large numbers of users discover these social network sites are a place where they can be able to spend their leisure time sharing interests, sharing ideas freely, sharing personal experience, and also to search for new friends or partners. These websites give an opportunity for its users to socialize with new people and to keep in touch or reconnect with current or old friends and families across disperse continents, which traditionally replace the common traditional methods. These social network websites need accurate and careful investigations and findings on the usability issues for effective interactivity and more usability. However, little research might have previously invested on the usability of these social network websites. Therefore, we propose a new framework to study and test the usability of these social network sites. We namely call our framework "Interactivity". This framework will enable developers to assess the usability of the social network sites. It will provide an overview of the user's behavior while interacting in these social network websites. Performance of the framework will be performed using Camtasia software. This software will entirely capture the interactivity of users including the screen and the movements, which the screen and the motion of the user action will undergo to analysis at the end of our research.

• Journal of The Korean Association of Information Education
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• v.11 no.2
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• pp.243-249
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• 2007

Most homepages of schools are available to publicize activities of education, to load educational materials efficiently. But we can't use current homepages of schools in making characteristic information or sharing educational resources. In this study, this I-CUBE system with RSS was designed and embodied for sharing characteristic educational activities and works in schools. Currently, I-CUBE is being under experimental test for sharing education activities and making community in elementry schools,.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.81-90
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• 2015

This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.

• The Journal of Society for e-Business Studies
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• v.14 no.4
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• pp.195-214
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• 2009

Semantic web portal is expected to overcome the shortcomings of the current web portals through advanced semantic web technologies and to be an effective and efficient method of knowledge sharing. In order to contribute to the knowledge sharing, semantic web portal needs to construct and integrate ontologies of each organization. Also, it needs to support search and navigation of inter-related knowledge. In this paper, we will design a semantic web portal that satisfies such requirements in the domain of display industry, and construct an ontology which links various knowledge of different fields. Moreover, we want to suggest an effective and automatic search/navigation method that supports customers who do not know the details of an ontology to easily get the desired results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.1065-1085
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• 2020

With rapid growth of content demands, device-to-device (D2D) content sharing is exploited to effectively improve the service quality of users. Considering the limited storage space and various content demands of users, caching schemes are significant. However, most of them ignore the influence of the asynchronous content reuse and the selfishness of users. In this work, the user preferences are defined by exploiting the user-oriented content popularity and the current caching situation, and further, we propose the social-aware rate, which comprehensively reflects the achievable contents download rate affected by the social ties, the caching indicators, and the user preferences. Guided by this, we model the collaborative caching problem by making a trade-off between the redundancy of caching contents and the cache hit ratio, with the goal of maximizing the sum of social-aware rate over the constraint of limited storage space. Due to its intractability, it is computationally reduced to the maximization of a monotone submodular function, subject to a matroid constraint. Subsequently, two social-aware collaborative caching algorithms are designed by leveraging the standard and continuous greedy algorithms respectively, which are proved to achieve different approximation ratios in unequal polynomial-time. We present the simulation results to illustrate the performance of our schemes.

• Korean Journal of Child Studies
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• v.33 no.3
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• pp.149-175
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• 2012

This study is designed to positively transform a teacher's emotional state whilst teaching their classes and be able to create happier lessons for preschool children. To do this, a teacher needs to reflect upon current problems and take steps to deal with them. The data for this study was collected from participatory observation and in-depth interviews, making use of photos, a reflective teacher's journal and interview records from Mar. 28, 2011 through Oct. 7, 2011. The problems identified were, (1) teacher centered classes, (2) a daily routine filled with large group activities, (3) disruptive students, and (4) repetitiveness. The routes to greater classroom "happiness" are (1) rearranging seats, (2) "story sharing activities" in small groups, (3) making a separate "story sharing activity" area, (4) using small groups instead of large groups, (5) changing the daily routine. The role of the teacher in finding greater "happiness" are (1) meaningful, 'real observation', (2) discovering genuine change from small points, (3) power sharing, and (4) growing and developing with children.