• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.481-488
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• 2009

GIS is used to isolate large power electrical equipment using SF6 gas. While GIS has simple structure, it has few break down, relatively high reliability. But it is hard to check up faults for reason of pressure. Faults of GIS should have a ripple effect on community and be hard to recovery. Consequently, GIS imports a preventive diagnostic system to find internal faults in advance. It is most important that reliability on the GIS preventive diagnostic system, because it estimates abnormality of system by analysis result of collected data. But, exist system which used central data management is low efficiency, and hard to guarantee timeliness and accuracy of data. To guarantee timeliness and accuracy, the GIS preventive diagnostic system needs accordingly to use a real-time middleware. So, in this paper, to improve reliability of the GIS preventive diagnostic system, we use a middleware based on TMO for guaranteeing timeliness of real-time distributed computing. And we propose an improved GIS preventive diagnostic system applying data acquisition, monitoring and control methods based on the TMO model. The presented system uses the Communication Control Unit(CCU) for distributed data handling which is supported by TMO. CCU can improve performance of the GIS preventive diagnostic system by guaranteeing timeliness of data handling process and increasing reliability of data through the TMO middleware. And, it has designed to take full charge of overload on a data acquisition task had been processed in an exist server. So, it could reduce overload of the server and apply distribution environment from now. Therefore, the proposed system can improve performance and reliability of the GIS preventive diagnostic system and contribute to stable operation of GIS.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.280-288
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• 2017

Nanocarbon base materials such as, graphene and graphene hybrid with high electrochemical performances have great deal of attention to investigate flexible, stretchable display and wearable electronics in order to develop portable and high efficient energy storage devices. Battery, fuel cell and supercapacitor are able to achieve those properties for flexible, stretchable and wearable electronics, especially the supercapacitor is a promise energy storage device due to their remarkable properties including high power and energy density, environment friendly, fast charge-discharge and high stability. In this study, we have fabricated flexible supercapacitor composed of graphene/conductive polymer composite which could improve its electrochemical performance. As a result, specific capacitance value of the flexible supercapacitor (unbent) was $198.5F\;g^{-1}$ which decreased to $128.3F\;g^{-1}$ (65% retention) after $500^{th}$ bending cycle.

• Journal of the Korean Society for Library and Information Science
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• v.47 no.1
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• pp.327-347
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• 2013

The use of the Internet is spread over all areas of our lives. However, its features raised serious social issues due to unethical behavior. To understand the level of Internet ethics among undergraduate students, a survey questionnaire of 31 questions regarding netiquette awareness, ethical norms, information credibility, and personal background is devised; data was collected from 830 students. Descriptive analysis shows low level of netiquette awareness, considerable deviation from six categories of ethical norms and problems of network information credibility. Results of statistical testing show gender and grade level as factors affecting Internet ethics. However, there is no significant difference in Internet ethics depending on related education experience. Based on the results, recommendations to promote Internet ethics are suggested.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.161-169
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• 2009

Multicast-based data communication is an efficient communication scheme in wireless networks where the Media Access Control (MAC) layer is based on one-hop broadcast from one source to multiple receivers. Compared with unicast, multicast over wireless channel should handle varying channel conditions of multiple users and user mobility to achieve good quality for all users. However, IEEE 802.11 does not support reliable multicast due to its inability to exchange RTS/CTS and ACK with multiple recipients. Thus, several MAC layer protocols have been proposed to provide reliable multicast. For the reliable multicast, an additional overhead is introduced and it degrades the system performance. In this paper, we propose a cross-layer design to reduce the control overhead for reliable multicast in OFDMA systems. We present an analytical formulation of the system throughput associated with the overhead.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2279-2284
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• 2017

Recent wireless communications using the unlicensed band have been on the rise and the range of use is increasing. The license-exempted band is a prerequisite for accepting interference between telecommunication equipment. In particular, the interference phenomenon of Bluetooth, wireless LAN, and RFID (Radio Frequency Identification) using the 2.4 GHz band is getting serious. In such urban areas, the wireless transmission medium may be in a bad state. There are roughly two ways to make effective transmission in this environment. The first is the IEEE 802.11 RTS / CTS method and the second is the frame fragmentation method. In this paper, it is difficult to transmit a frame over a certain size in a jamming environment due to the interference of the wireless environment. In this environment, we implement a frame division transmission scheme that guarantees effective transmission and reliability by dividing a frame into smaller units in order to perform reliability transmission and efficient transmission.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.9-19
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• 2004

WLAN (Wireless Local Area Networks) needs error recovery and flow control schemes to support reliable multicast protocol. Limited wireless bandwidth, as well as queuing losses caused by the asymmetric wired/wireless interactions, demands more effective approaches for reducing packet losses. Moreover, since the wireless channel is a shared broadcast medium, if sender receives feedback information simultaneously from several receivers, the feedback delays data frame transmission of forward direction by introducing channel congestion and burden at the sender. Therefore, it is important to minimize the amount of feedback information from receivers. In this paper, we propose an ARS(Adaptive Redundancy Scheme) that combines FEC(Forward Error Correction) using channel state estimation and ARQ(Automatic Repeat Request) both to reduce the amount of feedback information and the number of retransmissions and to guarantee high data reliability in a WLAN multicast environment. Performance of the proposed scheme is evaluated by means of analysis and simulations in AWGN and Rayleigh fading channels. The results show that the proposed scheme reduces the amount of feedback information and the number of retransmissions and guarantees high data reliability, while keeping throughput efficiency similarly with the conventional FEC and ARQ scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1190-1194
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• 2007

In sensor network, the importance of transporting data with reliability is growing gradually to support communications. Data flow from sink to nodes needs reliability for the control or management, that is very sensitive and intolerable, however relatively, data flow from nodes to sink is tolerable. In this paper, with emphasis of the data flow from sink to nodes, we proposed the mechanism that establishes confidence interval for transport. Establishing confidence interval herby-hop, not end to end, if errors happen or there's missing data, this mechanism recovers them with selective acknowledgement using fixed window. In addition, this mechanism supports franc congestion control depending on the buffer condition. Through the simulation, we showed that this mechanism has an excellent performance for error recovery in sensor network.

• The Journal of Bigdata
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• v.7 no.2
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• pp.103-111
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• 2022

There are many institutions, organizations, and sites related to responding to infectious diseases, but as the pandemic situation such as COVID-19 continues for years, there are many changes in the initial and current aspects, and accordingly, policies and response systems are evolving. As a result, regional gaps arise, and various problems are scattered due to trust, distrust, and implementation of policies. Therefore, in the process of analyzing social data including information transmission, Twitter data, one of the major social media platforms containing inaccurate information from unknown sources, was developed to prevent facts in advance. Based on social data, which is unstructured data, an algorithm that can automatically detect infectious disease threats is developed to create an objective basis for responding to the infectious disease crisis to solidify international competitiveness in related fields.

• Review of KIISC
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• v.20 no.3
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• pp.58-61
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• 2010

최근 영상압축 및 전송기술의 발달과 저장매체의 대용량화 등 IT 기술의 발달로 영상기반의 보안시스템은 누구나 쉽게 사용할 수 있는 보편화된 시스템이 되고 있다. 그리고 프로세서의 발달로 인해 감시카메라에서 취득한 영상을 영상처리를 통해 자동으로 해석하는 지능형 영상감시 시스템은 주목 받고 있다. 하지만 외부로부터 카메라가 공격을 당해 감시불능인 상태가 되면 아무리 뛰어난 지능형 영상감시 시스템이라고 해도 무용지물이 되기 때문에 카메라 무력화를 감시하는 알고리즘은 반드시 필요하다. 카메라 무력화 검지 알고리즘은 사용자로 하여금 시스템을 편리하게 사용할 수 있게 해 주지만 아직 많은 알고리즘들은 조명변화와 같은 일상적인 상황에 잦은 오보를 출력함으로 시스템의 신뢰도를 떨어뜨리고 오히려 사용자에게 불편을 주고 있다. 따라서 본 논문에서는 조명변화에 강건하도록 입력영상의 코너를 특징점으로 이용하여 감시카메라의 공격을 검출하는 방법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.100-102
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• 2005

RFID/USN이 큰 이슈가 되면서 RFID 에 대한 각종 연구와 응용이 현재 활발히 진행 중이다. 유선 네트워크상에서의 보안은 지금까지의 연구와 개발로 신뢰적인 통신이 가능하다. 그러나 RFID는 Air Interface를 전송매체로 사용하기 때문에 유선의 상황보다 외부의 노출정도가 훨씬 크다. 따라서 외부의 공격에 쉽게 노출 될 수 있으며 이를 보완하기위해 Tag안에 ID를 직접 넣지 않고 DataBase에서만 ID를 관리하는 방식의 RFID 인증 프로토콜을 제안했다. 기존의 RFID 인중 프로토콜보다 Reader의 작업량을 줄였고, 태그로부터 정보를 탈취하여 복호화 한다 하더라도 ID가 없기 때문에 쓸모없는 정보가 된다.