• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제28권2호
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• pp.105-112
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• 2017

In order to satisfy the diffusion of multimedia service in mobile communication and the demand for high-speed communication, it is essential to modify and improve high efficiency, wideband and nonlinear characteristic of multiband power amplifier. This research is designed to implement a single-stub matching circuit as a 2nd harmonic one that meets conditions of the Class-J power amplifier. Low characteristic impedance of the single-stub line is necessary to suit conditions of wideband Class-J. This research uses ceramic substrates having high permittivity to implement the single-stub line with low characteristic impedance, which eventually results in an amplifier satisfying the output impedance terms of Class-J in wideband frequency range. This result attributes to use of GaN HEMT packaged with a 2nd harmonic matching circuit and external fundamental circuit. The measurement results of the Class-J amplifier confirms the following characteristics: more than output power of 50 W(47 dBm) in bandwidth of 1.8~2.7 GHz(0.9GHz), maximum drain efficiency of 72.6 %, and maximum PAE characteristic of 66.5 %.

• Journal of Korea Multimedia Society
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• 제18권11호
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• pp.1319-1331
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• 2015

In the Republic of Korea, there's been a culture called 'Hyo' since Koryo Dynasty and this word represents the meaning of paying utmost respects to one's own parents and ancestors whether they are alive or have passed. However, nowadays, most of people live away from their family gravesites so that they do not and cannot take care of them except on the special holidays. For this reason, people could not respond promptly to the incidents occurred at the sites as they receive notifications much later dates most of the time. Thus, in this paper, we propose a low-cost gravesite monitoring system which the users can immediately respond to the disastrous events after being informed of current situations through PLC without delay. For the performance evaluation, the lab and test bed experiments were performed on an actual ship using 200Mbps and 500Mbps products instead of performing an on-site experiment after the system has actually been constructed. The Mountain Region PLC was installed on the power lines and the result showed successful 36.14Mbps communication. Therefore, we expect that this study will contribute in time and cost reduction while constructing the internet infrastructures in mountain regions or building the Smart-graves, tumulus, and charnel houses.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.167-174
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• 2016

The Korean distribution line currently consists of overhead ground wires (OHGW), overhead distribution lines, neutral wires (NW), and messenger wires (MW). The MW is installed under the NW. The lightning protection system in Korea is focused on OHGW and lightning arrester and the MW are not considered. Therefore, this paper proposes the applicability of MW for purpose of lightning protection. For this, we analyzed the effects of lightning overvoltage according to the existence of OHGW and MW and the grounding conditions of the MW in the Korean distribution system. The grounding conditions of the MW that we took into consideration were the common or separate grounding of the MW and NW. The analysis based on the equivalent circuit of the distribution pole at each condition was performed. The distribution lines and lightning were modeled using the Electromagnetic Transients Program (EMTP). For each of the installation conditions of the OHGW and MW, the various lightning conditions were simulated and analyzed for both direct and indirect lightning. The simulation results showed that, if the OHGW was not installed in the Korean distribution system, the lightning overvoltage could be reduced by the common grounding of the MW and NW.

• Transactions on Electrical and Electronic Materials
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• 제6권2호
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• pp.78-84
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• 2005

Standard crystalline solar cells are generally fabricated with the front grid pattern of silver paste contact. We have reported a detailed theoretical analysis of the proposed segmented cross grid line pattern in this paper. This work was carried out for the optimization of spacing and width of grid finger, main busbar and sub-busbar. The overall electrical and optical losses due to front contact were brought down to $10\%$ or even less as compared to the usual loss of $15\%$ or more in the conventional screen printed silver paste technology by choosing proper grid pattern and optimizing the grid parameters. The total normalized power loss for segmented mesh grid with plated metal contact was also observed and the total power loss could be brought down to $10.04\%$ unlike $11.57\%$ in the case of continuous grid and plated contact. This paper is able to outline the limitations of conventional screen printed contact.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제16권6호
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• pp.644-651
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• 2005

In this paper, a new predistortion method to reduce nonlinearity or a traveling wave tube amplifiers(IWTAs) is proposed. Nonlinear transfer characteristics of TWTA are analyzed using carrier complex power series. Inverse carrier complex power series or a predistortion linearizer to linearizer TWTA are also proposed. The inverse nonlinear distortion characteristics of predistorter can be realized with reflective structure that is composed of Schottky diode and resistive-terminated transmission line. The AM-to-AM and the AM-to-PM characteristics for TWTA by proposed predistortive linearizer on K-band were improved from -5.825 dB and -37.321^{\circ} to 0.786 dB and 6.742^{\circ}, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.285-285
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• 2009

Due to a development of a modem technology as Power Line Communication(PLC) over 200 Mbps, the high-speed multi-media data trasmission could be currently possible. In This paper we develop a high quality media transmitter-receiver based on merging the HomePlug AV, which is 200 Mbps class PLC technology and HDMI Interface technology. Smart Live 6 software were used for the assessment of audio property. As the result of measurement of the HD class images by capturing from the receiver of the PLC, the quality of images couldn't be confirm any deterioration, which has compared with original reflections. In case of audio part as the result of confirmation of the Phase, Magnitude, it has been confirmed that over 90% of nomal transmition and receiving of acoustic signal.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권2호
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• pp.1355-1363
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• 2015

In order to maintain customer voltage within allowable limit($220{\pm}13V$), tap operation of SVR(step voltage regulator) installed in primary feeder could be carried out according to the scheduled delay time(30 sec) of SVR. However, the compensation of BESS(battery energy storage system) is being required because the customer voltages during the delay time of SVR have a difficultly to maintain within allowable limit when PV system is interconnected with primary feeder. Therefore, this paper presents modeling of SVR to regulate voltage with the LDC(line drop compensation) method and modeling of BESS to control active and reactive power bi-directionally. And also, this paper proposes the coordination control modeling between BESS and SVR in order to overcome voltage problems in distribution system. From the simulation results based on the modeling with the PSCAD/EMTDC, it is confirmed that proposed modeling is practical tool for voltage regulation analysis in distribution system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제42권8호
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• pp.1-6
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• 2005

A dual-level low voltage differential signalling (DLVDS) circuit is proposed aiming at reducing transmission lines for LCD driver IC. In the proposed circuit, we apply a couple of primitive data to DLVDS circuit as inputs. The transmitter converts two inputs to two kinds of fully differential level signals. In this circuit, two transmission lines are sufficient to transfer two primitive inputs while keeping the LVDS feature. The receiver recovers The original input data through a level decoding circuit. We fabricated the proposed circuit using $0.25\mu m$ CMOS technology. The resultant circuit shows 1-Gbps/2-line data rate and 35-mW power consumption at 2.5V supply voltage, respectively.

• The Journal of Information Systems
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• 제22권1호
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• pp.65-87
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• 2013

The development and expansion of communication technology in the field of information technology (IT) have changed the method and culture of communication, mediating communication among people. In particular, since social network service (SNS) has the attributes of information delivery and processing, it has a more powerful dissipating effect and influence than other existing communication methods. The role of users in SNS is important because it has the communication structure of producer-consumer, which consists of sharing, connection and participation of users. In this line, the purpose of this study is to investigate the intention for continued use of SNS by user ability. In order to explain the motivation and behavior for continued use of SNS by users, this study employed the motivation theory and post-adaptation model. The study applied 'media literacy' to the characteristics of SNS media and environment and expanded it into the concept of 'SNS literacy' to identify the moderating effect by user ability. Referred to as 'user's ability that is required to use SNS,' the SNS literacy was verified for its moderating effect with the three sub-dimensions: 'technical accessing ability,' 'understanding ability' and 'creative ability.' The major findings of this study are as follows. First, the perceived usefulness and playfulness were found to have a significant effect on the intention for continued use of SNS, showing the same result with previous studies on technology acceptance. In other words, usefulness and playfulness are variables with an explanatory power in the SNS environment as well. Second, the conceptualization of SNS literacy with accessing ability, understanding ability and creative ability was found to be valid. Third, it was verified that there was a significant difference in the SNS literacy between perceived usefulness and continued use, indicating that users with higher ability respond sensitively to usefulness and affect continued behavior. The moderating effect of SNS literacy was also verified in the relationship between perceived playfulness and intention for continued use. The results above confirm the difference in post-adaptation behavior of individuals, and are expected to provide several implications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3412-3432
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• 2019

Recent advances in radio frequency (RF) power transfer provide a promising technology to power sensor nodes. Adoption of mobile chargers to replenish the nodes' energy has recently attracted a lot of attention and the mobility assisted energy replenishment provides predictable and sustained power service. In this paper, we study the joint optimization of mobile charging and data gathering in sensor networks. A wireless multi-functional vehicle (WMV) is employed and periodically moves along specified trajectories, charge the sensors and gather the sensed data via one-hop communication. The objective of this paper is to maximize the uplink throughput by optimally allocating the time for the downlink wireless energy transfer by the WMV and the uplink transmissions of different sensors. We consider two scenarios where the WMV moves in a straight line and around a circle. By time discretization, the optimization problem is formulated as a 0-1 programming problem. We obtain the upper and lower bounds of the problem by converting the original 0-1 programming problem into a linear programming problem and then obtain the optimal solution by using branch and bound algorithm. We further prove that the network throughput is independent of the WMV's velocity under certain conditions. Performance of our proposed algorithm is evaluated through extensive simulations. The results validate the correctness of our proposed theorems and demonstrate that our algorithm outperforms two baseline algorithms in achieved throughput under different settings.