• 대한전기학회논문지:시스템및제어부문D
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• 제54권7호
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• pp.443-446
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• 2005

In this paper, we analyses transmission performance of communication security(COMSEC) bit synchronization information over the single channel ground and airborne radion system in variable message format system. Experimental results demonstrate the robust characteristics of the COMSEC bit synchronization information in 10-1 $\~$ 10-5 of bit error channel and the relationship of time duration of bit synchronization and probability of synchronization detection.

• 정보보호학회논문지
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• 제30권5호
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• pp.859-870
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• 2020

MQTT-SN(Message Queuing Telemetry Transport - Sensor Network) 프로토콜은 센서 기반의 IoT(Internet of Things)환경에서 사용되는 메시지 전송 프로토콜이다. 이 MQTT-SN 프로토콜은 메시지 전송 중간에 중개자(Broker)를 둔 발행-구독 모델(Publish-Subscribe Model)로 각 IoT 장치들이 메시지를 전달 할 때 반드시 중개자를 통해 메시지를 주고 받는 모델이다. 하지만 MQTT-SN 프로토콜은 메시지 보안, 상호 인증, 접근 제어, 중개자 보안등을 만족하는 보안 관련된 기능을 제공하고 있지 않다. 이에 따라 최근 다양한 보안 문제가 발생하고 있으며, 보안이 필요한 상황이 대두되고 있다. 본 논문에서는 MQTT-SN의 보안 요구사항을 다시 한번 살펴보고, 이 프로토콜이 적용되는 IoT의 자원이 제한된 환경에서의 제약 조건을 만족하면서 보안을 향상시키는 수정된 프로토콜을 제안한다. 제안 프로토콜은 기존과 다르게, 보안 필드와 인증 서버가 추가되었으며 이를 통해 보안 요구사항을 만족시키도록 한다. 더불어 제안된 프로토콜을 실제 구현 및 테스트하고 에너지 소모 관점에서 제안된 프로토콜이 실제 사용이 가능한지 평가하도록 한다.

• 융합보안논문지
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• 제16권7호
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• pp.3-11
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• 2016

최근 광네트워킹 기술의 급격한 발전, SDN (Software-Defined Network) 및 NFV (Network Function Virtualization)로 대두되는 네트워크의 소프트웨어화, 그리고 단순한 고성능연결서비스를 포함한 연구협업을 가능하게 하는 플랫폼으로써의 연구망 등 인터넷 서비스을 포함한 연구망에서는 급격한 변화가 진행되고 있다. 이에 슈퍼컴과 함께 국가과학기술경쟁력을 대표하는 국가연구망의 향후 발전방향을 선진 국가연구망의 비교분석 및 사회가 요구하는 연구망의 역할 변화에 맞추어 조망해본다. 또한 국가연구망 백본의 40Gbps 및 100Gbps급 초광대역 네트워크화, 대용량의 데이터를 고속으로 전송하기 위한 Science DMZ 기반의 망분리, 마지막으로 BRO 기반 프로그래머블 가능한 캠퍼스 네트워크 Lastmile 보안 환경 구축 방안을 제시한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4483-4501
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• 2015

In this paper, we investigate a security transmission scheme at the physical layer for cooperative wireless relay networks in the presence of a passive eavesdropper. While the security scheme has been previously investigated with perfect channel state information(CSI) in the presence of a passive eavesdropper, this paper focuses on researching the robust cooperative relay beamforming mechanism for wireless relay networks which makes use of artificial noise (AN) to confuse the eavesdropper and increase its uncertainty about the source message. The transmit power used for AN is maximized to degrade the signal-to-interference-plus-noise-ratio (SINR) level at the eavesdropper, while satisfying the individual power constraint of each relay node and worst-case SINR constraint at the desired receiver under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Cooperative beamforming weight vector in the security scheme can be obtained by using S-Procedure and rank relaxation techniques. The benefit of the proposed scheme is showed in simulation results.

• 한국정보통신학회논문지
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• 제22권11호
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• pp.1554-1561
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• 2018

본 논문은 실시간 통신 미들웨어인 DDS에 대해 알아보고, DDS 보안통신의 성능을 향상하기 위한 방법을 제시한다. DDS는 OMG(Object Management Group)에서 지정한 통신 미들웨어 표준이다. OMG는 최근 발생하는 보안이슈들에 대응하기 위해 DDS Security 표준을 지정하였다. DDS의 보안의 성능은 기밀성의 유지와 전송 속도를 고려해야 한다. 기밀성 측면에서 현재 DDS Security 표준의 암호화 알고리즘인 AES-GCM은 강력한 암호화 알고리즘이지만 메시지 인증관련 부분에 약점이 존재한다. 속도 측면에서 보안기능을 위한 연산 부하는 실시간성이 요구되는 시스템에서 DDS를 사용하는데 제약사항이 된다. DDS의 보안기능을 개선하기 위해서는 AES-GCM보다 빠르고 암호화 강도가 높은 알고리즘이 필요하다. 본 논문에서는 이러한 요구사항을 충족하기 위해 AES-OCB 알고리즘을 적용한 DDS 메시지 암호화 방법을 제안하고 DDS와 전송성능을 비교해 최대 12%의 성능개선을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1512-1519
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• 2013

Oil-impregnated paper is a major type of insulation used in oil-filled converter transformers for both traditional and new energy systems. This paper presents and analyzes the results of the experiment conducted on the electrical aging of oil-impregnated paper under AC-DC combined voltages using the pulsed electro-acoustic (PEA) technique. The formation and dynamics of space charge affected the performance of insulation material. The electrical aged oil-paper insulation was obtained through electrical aged experiments under the voltages. Based on the PEA technique, measurements were carried out when the oil-paper insulation system was subjected to different stressing and aging times. The space charge dynamics in the bulk of the oil-paper insulation system with different aging times were measured and analyzed. Characteristic parameters such as the total charge injection amount, the total charges of fast moving and slow moving, and the distortion factor of electric field were calculated and discussed. Results show that the longer electrical aging time, the more charges trapped in the bulk of aging sample. It leads to larger distortion factor of electric field in the bulk of aging samples and accelerate degradation of oil-paper insulation under AC-DC combined voltages.

• Journal of Power Electronics
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• 제16권2호
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• pp.685-694
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• 2016

This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1682-1691
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• 2018

Natural ester is a suitable substitute for mineral oil and has been widely used in AC transformer in many countries. In order to further application of natural ester in direct current (DC) equipment, it is needed to investigate its long term insulation property under DC condition. In this paper, a thermal ageing experiment was conducted for both mineral oil-paper and natural ester-paper insulation. The DC breakdown and space charge characteristics of insulation paper impregnated with natural ester and mineral oil was compared. Results show that the resistivity of the paper immersed in natural ester and mineral oil both increase as the ageing goes on. While insulation paper impregnated with natural ester has higher resistivity and DC breakdown voltage than the paper impregnated with mineral oil. The DC breakdown voltage for the oil impregnated insulation paper being DC pre-stressing is higher than that without pre-stressing. The average DC breakdown field strength difference between the test with pre-stressing and without pre-stressing clearly shows that there is an apparent enhancement effect for the homo-charge injection on the DC breakdown.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1686-1693
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• 2014

In this paper, oil-paper samples composed of transformer windings were used to investigate the insulation degradation process subjected to partial discharge (PD), with artificial defects inside to simulate the PD induced insulation degradation. To determine appropriate test voltages, the breakdown time obtained through a group of accelerated electrical degradation tests under high voltages was firstly fitted by two-parameter Weibull model to acquire the average breakdown time, which was then applied to establish the inverse power law life model to choose advisable test voltages. During the electrical degradation process, PD signals were synchronously detected by an ultra-high frequency (UHF) sensor from inception to breakdown. For PD analysis, the whole degradation process was divided into ten stages, and chaos theory was introduced to analyze the variation of three chaotic parameters with the development of electrical degradation, namely the largest Lyapunov exponent, correlation dimension and Komogorov entropy of PD amplitude time series. It is shown that deterministic chaos of PD is confirmed during the oil-paper degradation process, and the obtained results provide a new effective tool for the diagnosis of degradation of oil-paper insulation subjected to PD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.192-194
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• 2001

The Transmission network provides physical transport, network security, and connection services. The five principles of Transmission pricing are economic efficiency, cost recovery, efficient regulation, simplicity and transparency, non-discrimination. The Transmission Charges are made up of transmission connection charge and transmission charge of network. The Transmission Losses will be considered through Marginal Transmission Loss Factors in the market operation. The transmission loss rentals are used for the reduction of the annual revenue requirement of the transmission network for the purpose of derivation of transmission use of network charge.