• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.37-48
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• 2014

Wireless mesh networks have emerged as a key technology in environment that needs wireless multi-hop communication without infrastructure and IEEE 802.11s mesh network standard have currently been established. One of big differences between this standard and the legacy IEEE 802.11 is that MCCA MAC is included to support QoS. MCCA supports bandwidth reservations between neighbors, so it can satisfy the QoS of bandwidth guarantee. However, MCCA has dis-advantages as follow; 1) it can not guarantee end-to-end bandwidth, 2) in multi-interface multi-channel wireless environments, the IEEE 802.11s does not provide a bandwidth reservation protocol and a wireless channel assignment etc. In this paper, we have proposed MIMC R-HWMP, which expands R-HWMP that was proposed in our previous work[3], to support multi-interface multi-channel. By simulation, we showed end-to-end bandwidth guarantee and the increase in the available bandwidth in multi-interface multi-channel wireless mesh networks.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.414-418
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• 2006

유비쿼터스 컴퓨팅의 인프라가 되는 센서 네트워크는 매우 작은 하드웨어로 이루어지는 많은 수의 센서 노드들로 구성된다. 이 네트워크의 토폴로지와 라우팅 방식은 그 목적에 따라 결정되어야 하며, 하드웨어 및 소프트웨어도 필요한 경우에는 변경되어야 한다. 따라서 그러한 네트워크를 최적으로 설계하기 위해서는 시스템 동작을 확인하고 성능을 예측할 수 있는 센서 네트워크 시뮬레이터가 필요하다. 현존하는 몇몇 센서 네트워크 시뮬레이터들은 특정 하드웨어나 운영체제에 맞추어 개발되었기 때문에, 그러한 특정 시스템들을 위해서만 사용될 수 있다. 그리고 시스템 설계 상의 주요 이슈가 되는 전력 소모량 및 프로그램 실행 시간을 추정하기 위한 어떤 수단도 지원하지 못하고 있다. 이 연구에서는 기존의 센서 네트워크 시뮬레이터들이 갖고 있는 문제점을 해결한 시뮬레이터를 개발하고, 센서 네트워크의 계층적 라우팅 프로토콜인 LEACH, TEEN, APTEEN의 전력소모량을 시뮬레이션을 이용하여 분석하였다. 시뮬레이션의 작업부하인 명령어 트레이스로는 ATmega128L 마이크로컨트롤러용 크로스컴파일러에 의해 생성된 실행 이미지를 사용하였다. 따라서 각각의 라우팅 프로토콜을 실제 센서 보드에서 동작하는 응용 프로그램으로 구현하고, 컴파일된 실행 이미지를 작업부하로 사용하여 시뮬레이션 하였다. 라우팅 프로그램들은 ETRI의 센서 네트워크 운영체제인 Nano-Q+ 1.6.1을 기반으로 구현되었으며, 하드웨어 플랫폼은 옥타컴의 센서 보드인 Nano-24이다. 시뮬레이션 결과에 따르면, 센서 네트워크는 그 사용 목적에 따라 라우팅 프로토콜을 적절히 선택해야 한다는 것을 알 수 있다. 즉, LEACH는 주기적으로 네트워크의 상황을 체크해야 하는 경우에 적합하고, TEEN은 환경의 변화를 수시로 감지해야 하는 경우에 적합하다. 그리고 APTEEN은 전력소모량과 기능 측면을 모두 고려할 때 가장 효과적인 라우팅 프로토콜이라고 할 수 있다.iRNA 상의 의존관계를 분석할 수 있었다.수안보 등 지역에서 나타난다 이러한 이상대 주변에는 대개 온천이 발달되어 있었거나 새로 개발되어 있는 곳이다. 온천에 이용하고 있는 시추공의 자료는 배제하였으나 온천이응으로 직접적으로 영향을 받지 않은 시추공의 자료는 사용하였다 이러한 온천 주변 지역이라 하더라도 실제는 온천의 pumping 으로 인한 대류현상으로 주변 일대의 온도를 올려놓았기 때문에 비교적 높은 지열류량 값을 보인다. 한편 한반도 남동부 일대는 이번 추가된 자료에 의해 새로운 지열류량 분포 변화가 나타났다 강원 북부 오색온천지역 부근에서 높은 지열류량 분포를 보이며 또한 우리나라 대단층 중의 하나인 양산단층과 같은 방향으로 발달한 밀양단층, 모량단층, 동래단층 등 주변부로 NNE-SSW 방향의 지열류량 이상대가 발달한다. 이것으로 볼 때 지열류량은 지질구조와 무관하지 않음을 파악할 수 있다. 특히 이러한 단층대 주변은 지열수의 순환이 깊은 심도까지 가능하므로 이러한 대류현상으로 지표부근까지 높은 지온 전달이 되어 나타나는 것으로 판단된다.의 안정된 방사성표지효율을 보였다. $^{99m}Tc$-transferrin을 이용한 감염영상을 성공적으로 얻을 수 있었으며, $^{67}Ga$-citrate 영상과 비교하여 더 빠른 시간 안에 우수한 영상을 얻을 수 있었다. 그러므로 $^{99m}Tc$-transierrin이 감염 병소의 영상진단에 사용될 수 있을 것으로 기대된다.리를 정량화 하였다. 특히 선조체에서의 도파민 유리에 의한 수용체 결합능의 감소는 흡연에 의한 혈중 니코틴의 축적 농도와 양의 상관관계를 보였다(rho=0.9, p=0.04). 결론: $[^{11}C]raclopride$ PET을 이용하여 비흡연 정상인에서 흡연에 의한 도파민 유리를 영상화 및 정량화 하였고, 흡연에 의한 선조체내 도파민 유리는 흡연시 흡수된

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.585-600
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• 2012

Security issues in online games are increasing as the online game industry grows. Real money trading (RMT) by online game users has become a security issue in several countries including Korea because RMT is related to criminal activities such as money laundering or tax evasion. RMT-related activities are done by professional work forces, namely gold-farmers, and many of them employ the automated program, bot, to gain cyber asset in a quick and efficient way. Online game companies try to prevent the activities of gold-farmers using game bots detection algorithm and block their accounts or IP addresses. However, game bot detection algorithm can detect a part of gold-farmer's network and IP address blocking also can be detoured easily by using the virtual private server or IP spoofing. In this paper, we propose a method to detect gold-farmer groups by analyzing their connection patterns to the online game servers, particularly information on their routing and source locations. We verified that the proposed method can reveal gold-farmers' group effectively by analyzing real data from the famous MMORPG.

• Journal of the Korea Society for Simulation
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• v.19 no.1
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• pp.53-61
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• 2010

In wireless sensor networks(WSNs) individual sensor nodes are subject to security compromises. An adversary can physically capture sensor nodes and obtain the security information. And the adversary injects false reports into the network using compromised nodes. If undetected, these false reports are forwarded to the base station. False reports injection attacks can not only result in false alarms but also depletion of the limited amount of energy in battery powered sensor nodes. To combat these false reports injection attacks, several filtering schemes have been proposed. The statistical en-routing filtering(SEF) scheme can detect and drop false reports during the forwarding process. In SEF, The number of the message authentication codes(threshold) is important for detecting false reports and saving energy. In this paper, we propose a dynamic threshold determination method for energy efficient SEF using fuzzy-logic in wireless sensor networks. The proposed method consider false reports rate and the number of compromised partitions. If low rate of false reports in the networks, the threshold should low. If high rate of false reports in networks, the threshold should high. We evaluated the proposed method’s performance via simulation.

• International Journal of High-Rise Buildings
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• v.12 no.3
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• pp.225-234
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• 2023

Even at this point in the era of digital transformation, we are still facing many problems in the safety sector that cannot prevent the occurrence or spread of human casualties. When you are in an unexpected emergency, it is often difficult to respond only with human physical ability. Human casualties continue to occur at construction sites, manufacturing plants, and multi-use facilities used by many people in everyday life. If you encounter a situation where normal judgment is impossible in the event of an emergency at a life site where there are still many safety blind spots, it is difficult to cope with the existing manual guidance method. New variable guidance technology, which combines artificial intelligence and digital twin, can make it possible to prevent casualties by processing large amounts of data needed to derive appropriate countermeasures in real time beyond identifying what safety accidents occurred in unexpected crisis situations. When a simple control method that divides and monitors several CCTVs is digitally converted and combined with artificial intelligence and 3D digital twin control technology, intelligence augmentation (IA) effect can be achieved that strengthens the safety decision-making ability required in real time. With the enforcement of the Serious Disaster Enterprise Punishment Act, the importance of distributing a smart location guidance system that urgently solves the decision-making delay that occurs in safety accidents at various industrial sites and strengthens the real-time decision-making ability of field workers and managers is highlighted. The smart location guidance system that combines artificial intelligence and digital twin consists of AIoT HW equipment, wireless communication NW equipment, and intelligent SW platform. The intelligent SW platform consists of Builder that supports digital twin modeling, Watch that meets real-time control based on synchronization between real objects and digital twin models, and Simulator that supports the development and verification of various safety management scenarios using intelligent agents. The smart location guidance system provides on-site monitoring using IoT equipment, CCTV-linked intelligent image analysis, intelligent operating procedures that support workflow modeling to immediately reflect the needs of the site, situational location guidance, and digital twin virtual fencing access control technology. This paper examines the limitations of traditional fixed passive guidance methods, analyzes global technology development trends to overcome them, identifies the digital transformation properties required to switch to intelligent variable smart location guidance methods, explains the characteristics and components of AI-based public facility smart fire safety integrated system (ISFS).

• The KIPS Transactions:PartC
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• v.10C no.5
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• pp.625-634
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• 2003

More than a decade after its initial proposal, deployment of IP Multicast has been limited due to the problem of traffic control in multicast routing, multicast address allocation in global internet, reliable multicast transport techniques etc. Lately, according to increase of multicast application service such as internet broadcast, real time security information service etc., overlay multicast is developed as a new internet multicast technology. In this paper, we describe an overlay multicast protocol and propose fast join mechanism that considers switching of the tree. To find a potential parent, an existing search algorithm descends the tree from the root by one level at a time, and it causes long joining latency. Also, it is try to select the nearest node as a potential parent. However, it can't select the nearest node by the degree limit of the node. As a result, the generated tree has low efficiency. To reduce long joining latency and improve the efficiency of the tree, we propose searching two levels of the tree at a time. This method forwards joining request message to own children node. So, at ordinary times, there is no overhead to keep the tree. But the joining request came, the increasing number of searching messages will reduce a long joining latency. Also searching more nodes will be helpful to construct more efficient trees. In order to evaluate the performance of our fast join mechanism, we measure the metrics such as the search latency and the number of searched node and the number of switching by the number of members and degree limit. The simulation results show that the performance of our mechanism is superior to that of the existing mechanism.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.1
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• pp.1-8
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• 2017

Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling mobility in wireless sensor networks. To do this, many studies have been proposed to support mobile sink groups. When closely looking at mobile sink groups, they can be divided into (multiple) small groups according to the property of applications. For example, a platoon can be divided into multiple squads to carry out its mission in the battle field. However, the previous studies cannot efficiently support the division of mobile sink groups because they do not address three challenging issues engendered by the mobile sink group division. The first issue is to select a leader sink for a new small mobile sink group. The efficient data delivery from a source to small mobile sink groups is the second issue. Last, the third issue is to share data between leader sinks of small mobile sink groups. Thus, this paper proposes a routing protocol to efficiently support the division of mobile sink groups by solving the three challenging issues. For the first issue, the proposed protocol selects a leader sink of a new small mobile sink group which provide a minimum summation of the distance between the new leader sink and the previous leader sink and the distance from the new leader sink to all of its member sinks. For the efficient data delivery from a source to small mobile sink groups in the second issue, the proposed protocol determines the path to minimize the data dissemination distance from source to small mobile sink group by calculating with the location information of both the source and the leader sinks. With regard to the third issue, the proposed protocol exploits member sinks located among leader sinks to provide efficient data sharing among leaders sinks by considering the location information of member sinks. Simulation results verified that the proposed protocol is superior to the previous protocol in terms of the energy consumption.