• Journal of Communications and Networks
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• v.14 no.6
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• pp.629-639
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• 2012

A challenge faced by smart grid systems is providing highly reliable transmissions to better serve different types of electrical applications and improve the energy efficiency of the system. Although wireless networking technologies can provide high-speed and cost-effective solutions, their performance may be impaired by various factors that affect the reliability of smart grid networks. Here, we first suggest the use of IEEE 802.11s-based wireless LAN mesh networks as high-speed wireless backbone networks for smart grid infrastructure to provide high scalability and flexibility while ensuring low installation and management costs. Thereafter, we analyze some vital problems of the IEEE 802.11s default routing protocol (named hybrid wireless mesh protocol; HWMP) from the perspective of transfer reliability, and propose appropriate solutions with a new routing method called HWMP-reliability enhancement to improve the routing reliability of 802.11s-based smart grid mesh networking. A simulation study using ns-3 was conducted to demonstrate the superiority of the proposed schemes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.528-532
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• 2005

As the current IEEE 802.11 wireless LAN standard provides the unified channel access procedure for each traffic service without considering its own traffic characteristics, it is difficult to get its differentiated service qualities at IEEE 802.11 wireless LAN system. To solve this limit, IEEE 802.11e standard that can provide differentiated service to each traffic is under preparation. In this study, we implemented IEEE 802.11e EDCA channel access scheme with NS-2 simulator, and showed its numerical results in various system environments with using average delay and throughput as performance measures.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.235-240
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• 2003

무선 인터넷 시장이 커짐에 따라 가장 크게 대두되는 이슈 중에 하나는 802.11 ESS에서의 AP간의 상호운영과 STA 정보의 안전한 핸드오프이다 IAPP는 액서스 포인트 AP(Access-Point)에 다양한 로컬 이벤트가 일어날 때 다른 AP들과 통신하기 위하여 AP 관리 개체에 의해 사용되는 통신 프로토콜이다. IAPP의 기능은 ESS의 생성과 유지를 용이하게 하고, STA의 안전하고 빠른 이동성을 지원하며 AP가 주어진 시간에 각 STA와 단독 결합 요청을 수행할 수 있도록 지원한다. 본 논문에서는 현재 802 11F에서 진행 중인 IAPP의 내용을 중심으로 RADIUS를 바탕으로 하는 IAPP의 운영에 대해서 연구했다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.145-147
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• 2005

IEEE 802.11 기술이 상용화된 이후 여러 가지 보안에 관련된 취약점들이 드러났다. 이를 보완하기 위하여 802.1li 그룹이 802.11보안 관련 표준안을 제시하였다. 그러나 802.11에서 문제가 되었던 여러 종류의 DoS 공격들 중 몇 개의 공격들은 802.11i에서 아직 유효하다. Deauthe-ntication, Disassociation 메시지를 이용한 공격이 802.1li에서도 유효한 대표적인 공격 중 하나이다. 이 공격은 802.1li에서의 관리 프레임에 802.11과 같은 수준의 데이터 암호화가 적용되기 때문에 가능한 것이다. 본 논문에서는 이러한 취약점을 TKIP를 이용해 제안된 state value를 암호화하여 이를 예상 값과 비교한 후 Deauthentication, Disassociation 공격을 판단하는 메커니즘을 제시 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1413-1416
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• 2008

최근 들어 IEEE 802.11 WLAN 서비스에 대한 수요의 증가와 함께 WLAN 환경에서 실시간 멀티미디어 서비스를 이용하려는 사용자의 관심이 날로 증가하고 있다. 그러나 IEEE 802.11i 의 보안 정책은 MS 의 이동이 빈번하게 발생하는 WLAN 환경에서 끊김 없는 실시간 멀티미디어 서비스를 제공하기에는 핸드오프 지연 시간이 너무 길다. 본 논문은 DoS 공격에 취약한 기존 802.11i 에서의 4-way Handshake 를 대체하는 신속하고 효율적인 인증 및 세션키 분배 메커니즘을 제안한다.

• The Korean Journal of Mycology
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• v.13 no.2
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• pp.83-87
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• 1985

The temperature dependency and the stability of enzyme systems for $11{\alpha}-hydroxyla­tion$ of progesterone were investigated using Aspergillus phoenicis. Though A. phoenicis conserves high enzyme activities for lactose hydrolysis even at high temperatures, the bioconversion reaction of progesterone by this strain was found to be very temperature sensitive. The compositions of reaction mediums of inside and outside of cells were analyzed using sonication technique. At early stage of reaction, the concentration of $11{\alpha}-hydroxyprogesterone$ of cell inside was higher than that of outside. But as the reaction proceeded further, the $11{\alpha}-hydroxyprogesterone$ existing inside of cells being converted into another products, its concentration was lower within the cells that in the bulk medium. Even in the reaction mediums containing organic solvents, A. phoenicis was founded to be able to metabolite, so that $11{\alpha}-hydroxyprogesterone$ can be produced continuously from fixed bed reactions packed with immobilized A phoenicis in vivo.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.41-46
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• 2007

Surface potential properties at the interface of pentacene thin films on gold (Au) and aluminum (Al) surfaces were investigated by using a near-field scanning microwave microprobe (NSMM). The surface potential formed across the pentacene film was observed by measuring the microwave reflection coefficient $S_{11}$ and compared with the result of a Kelvin-probe method. The obtained reflection coefficient ${\Delta}S_{11}$ of the pentacene thin films on Al was decreased as the pentacene film thickness increased due to the increased accumulation of negative space charges, while for Au ${\Delta}S_{11}$ was essentially constant.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1305-1309
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• 2002

Subsurface radar characterize a broadband frequency to collect a information, such as a crack of building, because of using narrow pulse. In this paper, we design a broadband bowtie antenna, using a microstrip, with a FR-4 substrate of ${\varepsilon}_r=4.0$, t=1.6mm. It has a 9.31% bandwidth at s11<-10 dB and s11=-27.45 dB, VSWR=1.089 at 5.78GHz.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.338-341
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• 2005

Recently there are increasing needs for Internet and various kinds of contents. These traffics for various contents need more amount of data to provide high-quality information and require various QoS depending on the characteristics of contents. However, current Internet service supports BE (Best Effort) service only, therefore IntServ (Integrated Service) scheme and DiffSserv (Differentiated Service) scheme are represented to support QoS in IP layer. This paper describes new scheme that provides QoS taking into account the traffic characteristics over Mobile IPv6 network based on IEEE 802.11e by decreasing signal process time using traffic class of DiffServ and evaluates the performance through computer simulation.

• Journal of Genetic Medicine
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• v.6 no.2
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• pp.175-178
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• 2009

The 22q11.2 duplication syndrome is an extremely variable disorder with a phenotype ranging from normal to congenital defects and learning disabilities. Recently, the detection rate of 22q11.2 duplication has been increased by molecular techniques, such as array CGH. In this study, we report a familial case of 22q11.2 duplication detected prenatally. Her first pregnancy was terminated because of 22q11.2 duplication detected incidentally by BAC array CGH. The case was referred due to second pregnancy with same 22q11.2 duplication. We perfomed repeat amniocentesis for karyotype and FISH analysis. Karyotype analysis from amniocytes and parental lymphocytes were normal, while FISH analysis of interphase cells presented a duplication of 22q11.2 in the fetus and phenotypically normal mother. The fetal ultrasound showed grossly normal finding. After genetic counseling about variable phenotype with intrafamilial variability with 50% recurrence rate, the couple decided to continue the pregnancy. The newborn had no apparent congenital abnormalities until 2 weeks after birth. We recommend that family members of patients with a 22q11.2 duplication be tested by the interphase FISH analysis. Also, we point out the importance of genetic counseling and an evaluation of the clinical relevance of diagnostic test results.