• Journal of the Korea Society of Computer and Information
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• v.21 no.10
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• pp.77-83
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• 2016

To verify the trustworthiness of messages, public key certificates and certificate revocation list(CRL) has been standardized for vehicular networks. However, timely distribution of large CRLs to vehicles should be more elaborated with low bandwidth utilization from a practical point of view. To address this concern, we propose a CRL distribution scheme using long term evolution(LTE) point-to-multicast transmission, namely the enhanced multimedia broadcast multicast service(eMBMS). The schem is much more resource efficient than the existing unicast CRL distribution schemes for vehicular networks and it allows realizing the regional CRL distribution schemes efficiently in LTE network. By means of ns-3 simulation, we analyze the performance, latency, and execution time of the scheme in terms of varying coverage of the multimedia broadcast multicast service over single frequency network (MBFSN).

• Journal of information and communication convergence engineering
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• v.12 no.2
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• pp.75-82
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• 2014

Dispersion management (DM), optical phase conjugation (OPC), and the combination of DM and OPC are promising techniques to compensate for optical signal distortion due to group velocity dispersion and nonlinear Kerr effects. The system performance improvement in DM links combined with OPC has been reported; however, the fixed residual dispersion per span (RDPS) usually used in these links restricts the flexibility of link configuration. Thus, in this paper, a flexible optical link configuration with artificially distributed single-mode fiber (SMF) lengths and RDPS in the combination of DM and OPC is proposed. Simulation results show that the best artificial distribution pattern is the gradually descending distribution of SMF lengths and the gradually ascending distribution of RDPS, as the number of fiber spans is increased, regardless of the average RDPS, the optimal net residual dispersion, and the dispersion coefficient of the dispersion compensating fiber.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.328-333
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• 2011

A Distribution Automation System (DAS) is operated by monitoring and control of the field statesusing Feeder Remote Terminal Units (FRTUs) installed together withautomatic switches.An optimal placement of automatic switchescan enhanceefficiencyof the operation and restoration, and improve the power supply reliability ofa DAS.This paper proposes an algorithm to decide the optimal placement of automatic switches ina DAS.The proposed algorithm was developed ona DAS witha six sections and three links configuration. The proposed algorithm was provided inaneight-feeder power distribution system.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.355-357
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• 2002

Distribution lines are spanned on a much large area as compared to transmission lines, and therefore, are more often susceptible to lightning strokes. The selection of the proper value of basic insulation level(BIL), for particular insolation components of distribution structures in specific, is very important. Lightning strikes has current risetimes ranging from 0.1 to several $\mu s$ and can produce transient overvoltages substantially greater than the BIL of many distribution systems in spite of lightning arresters. This paper describes lightning overvoltage of a 22.9kV distribution system due to lightning strike. This study will provide the information on insulation coordination studies to adopt BIL.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.315-318
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• 2002

The use of high-temperature superconducting materials for transmission cable application is being realized in prototype situation. HTS cable systems have been installed in laboratories and tested successfully around the world. In korea. the first step in development of superconducting cables is distribution system. In this paper. it is proposed the HTS distribution system modeling using ATPDraw and EMTDC programs. In the multilayer conductor, the inner layers have higher impedance than the outer layers. As a result, the current concentrate$ in the outer layers. This paper presents the result of the current distribution in EMTDC.

• KIEE International Transactions on Power Engineering
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• v.5A no.2
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• pp.171-176
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• 2005

The effects of surge arresters for the protection of transmission systems against direct lightning strokes have already been reviewed by many researchers. However, their studies have not encompassed underground cable systems. Therefore, in this paper we investigate the 22.9kV combined distribution systems that have arresters and ground wires. In addition, we analyze the overvoltages on underground distribution cable sections when direct lightning strokes contact the overhead ground wire using EMTP. Finally, we discuss the effect of lightning strokes according to the change of cable length and installation of arresters. This study provides insulation coordination methods for reasonable system design in 22.9kV underground distribution cable systems.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.360-362
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• 2003

In operation of distribution system, DGs(Distributed Generations) are installed as an alternative of extension and establishment of substations, transmission and distribution lines according to increasing power demand. Optimal capacity and allocation of DGs improve power quality and reliability. This paper proposes a method for determining the optimal number, size and allocation of DGs needed to minimize operation cost of distribution system. Capacity of DGs for economic operation of distribution system can be estimated by the load growth and line capacity during operation planning duration. DG allocations are determined to minimize total cost with failure rate and annual reliability cost of each load point using GA(Genetic Algorithm).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.801-807
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• 2008

Recently, CV, CN-CV and CNCV-W cable are used for HVDC transmission and distribution cable. However, XLPE which is used as insulation layer of power cable has thermosetting properties. It is very difficult to recycling. In this paper, we prepared HDPE/EVA film, which the blending ratio are 80:20, 70:30, 60:40, 50;50 respectively for the purpose of recycling. Main factor such as electric field distribution and its resistivity in insulation system affected on insulation performance and reliability for HVDC applications. Therefore, electric field distribution formed by space charge and characteristics of volume resistivity was currently investigated. We suggest the possibility of utilization for HVDC insulation layer from the results.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.199-203
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• 2016

The cost needed to managing equipment is constantly increasing because of increase of power equipment. The regulations such as PAS 55 and ISO 55000 were enacted to manage equipment assets. The advanced management methods such as real-time monitoring, condition evaluation, and health indices are avalable in generation system, transmission system, and substation transformers. However, These methods can not be applied to distribution equipment because of a lot of equipment. Therefore reliability assessment is very important in case of distribution equipment. In this paper, failure rates are extracted considering characteristics of regions, and which are the essential factors to reliability evaluation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.267.2-267.2
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• 2013

In the citrate reduction method of gold nanoparticle (AuNP) synthesis, pH of the reaction mixture can have a considerable impact on the size and size distribution of AuNPs. In this work, effects of pH variation upon the size and its distribution were examined systematically. As the initial pH was change from 5.5 to 10.5, it showed an optimal pH around 7.5. At this pH, both of the size and the size distribution showed their minimum values, which was verified by transmission electron microscopy and UV-vis spectroscopy. This occurrence of optimal pH was discussed with the results of in situ monitoring pH during the reaction of AuNP synthesis.