• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.390-393
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• 2007

The reliability as well as the power capability of the UPS system can be increased by replacing a single UPS unit with multiple small UPS units in parallel, resulting in a so-called module UPS. This module UPS system allows that a new module can be added or replaced while maintaining power to loads, which is a hot-swappable operation. In addition, it has desirable features such as ease of output power expandability, convenience of maintenance and repair, and high reliability. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. 5kVA modules are designed and implemented to confirm the effectiveness of the proposed approaches. Experimental results show that the module UPS system has a high power factor, a low distortion of output voltage and input current, hot-swappable operations and good load sharing characteristics.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.44-51
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• 2003

The module UPS can flexibly implement expansion of power system capacities. Further-more, it can be used to build up the parallel redundant system to improve the reliability of power system operation. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. In this paper, the three-arm converter/inverter is compared with the general full-bridge and half-bridge topology from a practical point of view and chosen as the module UPS topology. The switching control approaches based on a pulse width modulation of the converter and inverter of the system are presented independently. The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. Two prototype 3㎸A modules are designed and implemented to confirm the effectiveness of the pro-posed approaches. Experimental results show that the three-arm UPS system has a high power factor, a low distortion of output voltage and input current, and good load sharing characteristics.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.907-915
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• 2009

Spectrum sharing between wireless systems becomes a critical issue due to emerging new technologies and spectrum shortage. Recently, IMT system has been allocated in the same frequency C band (3400-4200MHz) along with FSS services on co-primary basis, which means that harmful interference probability may be inspired. In this paper, to estimate the spectrum sharing between IMT and FSS systems, the minimum separation distances have been evaluated considering major factors such as the clutter loss in some areas and the elevation angle of FSS earth station, and using I/N=-10dB which is fundamental criterion for coexistence.

• Journal of Power Electronics
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• v.19 no.1
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.169-182
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• 2017

The purpose of this study is to empirically examine a behavior improvement of unethical information sharing through the ethics program in organization. An unethical behavior of information sharing on organization members is to be get to private interests through divulgence of company's confidential information. An unethical information-sharing of individual is the opportunist and selfish behavior for an expansion of social capital and shows a negative ripple effect in organization. When conducting the research methods, the analysis order performs the cluster, discriminant, t-test and multiple regressions. According to the study, There are differences the behavior of unethical information sharing between opportunist and non-opportunist. The opportunist member for unethical behavior improvement required the program operation both value and compliance oriented program. Non-opportunist member required only the value-oriented program. The upcoming research needs to explore both ethics program's frequency and action of a punished person.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.507-514
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• 2019

Federal communications commissions (FCC) has announced the first set of rules for 3.5 GHz (3,550 - 3,700 MHz) band used Navy radar and fixed satellite service (FSS) earth stations as primary service to sharing for citizen broadband radio service (CBRS) enable development of relatively low powered network technologies like small cells. Since CBRS sharing technique based on the 3-tiered spectrum access system (SAS) is able to protect the higher tiered users from harmful interference from lower tiered users, it has been considered actively to be introduced in Korea. However, 3.5 GHz band had been already allocated to the 5G services in Korea, the sharing studies have been carried out for 3,700 - 5,000 MHz, As the result, the 3.8 GHz (3,800 - 3,900 MHz) band used for only FSS system is able to be sharing, and an introduction of CBRS has been proposed in Korea by analyzing the interference to the FSS earth stations.

• Nutrition Research and Practice
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• v.14 no.4
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• pp.401-411
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• 2020

BACKGROUND/OBJECTIVES: The expansion of menu labeling to restaurants has created a need to study customers' behavior toward nutrition information. Therefore, the purpose of this research was to compare college students' behavior toward nutrition information communication between Korea and the US. This study consisted of three objectives: 1) to compare the frequency of usage as well as degree of trust regarding smartphone-based communication channels in the acquisition of nutrition information among college students between Korea and the US, 2) to compare knowledge-sharing behavior related to nutrition information among college students between Korea and the US, and 3) to identify the role of country in the process of knowledge-sharing behavior. SUBJECTS/METHODS: A survey was distributed via the web to college students in Korea and the US. Data were collected in the 2nd week of March 2017. Completed responses were collected from 423 Koreans and 280 Americans. Differences between Koreans and Americans were evaluated for statistical significance using a t-test. In order to verify the effects of knowledge self-efficacy and transactive memory capability on knowledge-sharing behavior related to nutrition information, a regression analysis was performed. RESULTS: Significant differences were found in the frequency of usage as well as degree of trust in communication channels related to nutrition information between Korean and American college students. While knowledge self-efficacy and tractive memory capability had positive effects on knowledge-sharing behavior related to nutrition information, country had a significant effect on the process. CONCLUSIONS: This study is the first to compare customer behavior toward nutrition information acquisition and sharing between Korea and the US. Comparative research on nutrition information revealed differences among the different countries. Therefore, this study contributes to the body of knowledge on the nutrition information research, in particular, by providing a comparison study between countries.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.385-385
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• 2006

• Journal of Korean language education
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• v.29 no.3
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• pp.25-53
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• 2018

This study examined the influence of lexical factors on verbal Eojeol recognition. To meet the goal, forty-five L2 Korean learners and twenty-two Korean native speakers took Eojeol decision tasks measured with the lexical factors such as 'number of strokes', 'number of consonants and vowels', 'number of syllables', 'number of morphemes', 'whole Eojeol frequency', 'root frequency', 'first-syllable-sharing frequency', and 'number of dictionary meanings.' As a result, 'whole Eojeol frequency' was the most effective factor to predict Eojeol recognition reaction time for native speakers and L2 learners, which supports the full-list model. Other lexical factors influencing Eojeol recognition reaction time in L2 learners were different following their proficiency level.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.792-795
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• 2004

This paper is an interference analysis from S-DAB(Satellite-Digital Audio Broadcasting) into terrestrial IMT-2000 systems intending to use the band 2630-2 655 MHz and that could be used to determine the impact of S­DAB on terrestrial IMT-2000 in the context of co-frequency sharing through the development of pfd masks.