• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.80-84
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• 2010

Data multicasting from a source to multiple sinks in wireless sensor networks is used to achieve both reducing communication costs and energy efficiency. Almost all existing schemes for the multicasting might be effectively performed by optimal construction of a multicasting tree between a source and multiple stationary sinks. However, in practical sensor applications, sinks could move around on the wireless sensor networks for own missions, such as scouting of soldiers and saving lives of victims by firefighters. Unfortunately, the sink mobility causes frequent entire reconstruction of the multicasting tree and thus it leads to exhaustion of battery power of sensors. Hence, we propose an energy-efficient multicast protocol to support multiple mobile sinks by the local multicast tree reconstruction, called Local Update-based geographic Multicasting for Mobile sinks (LUMM) for wireless sensor networks. Our simulation results show that our scheme for mobile sinks is more efficient in terms of energy resource management than other exist works.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1528-1531
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• 2011

최근 악성봇은 해커에 의해 원격 조정되어 명령에 의해 스팸메일 발송, DDoS 공격 등의 악성행위를 수행하는 웜/바이러스이다[2]. 악성봇은 이전의 웜/바이러스와 달리 금전적인 이득을 목적으로 하는 것이 많아 작게는 일상생활의 불편함으로부터 크게는 사회적, 국가적으로 악영향을 주고 있다. 국내에서는 이러한 위험을 방어하기 위한 효과적인 대응 방법으로 DNS 싱크홀을 운영 하고 있다. 본 논문에서는 DNS 싱크홀 운영 중 수집한 봇 명령/제어 (Command and Control, C&C) 도메인을 Internet Service Provider (ISP) DNS 싱크홀 시스템에 적용하는 과정에서 나타나는 문제점을 효과적으로 해결 하기 위한 DNS Response Policy Zone(RPZ)을 이용한 DNS 싱크홀 운영 방안을 제시 하였다.

• 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.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.1109-1111
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• 2017

본 논문은 다양한 센서들과 디바이스들이 실시간으로 정보를 주고 산업 IoT 환경에서 실시간 분산 제어 역할을 하는 마스터 노드(Master Node)인 CPS시스템이 시스템장애 또는 내, 외부적인 요인으로 인해 정상적인 수행을 하지 못할 때 일시적으로 마스터 노드의 기능을 수행할 수 있는 싱크노드(Sink Node)를 선정하여 대리 마스터 노드를 결정하는 방안을 제시한다. 산업 IoT환경에서 마스터 노드의 역할로써 중요한 파라미터들을 선정한다. 이 후 상황에 따라 파라미터들의 가중치를 변경하여 우선순위 알고리즘을 통해 지속적으로 싱크 노드들의 우선순위에 대한 정보를 마스터 노드와 싱크노드들 간 공유하게 된다. 마스터 노드의 결함이 발생 시 우선순위가 높은 싱크노드가 마스터 노드의 역할을 대신 수행하여 예기치 못한 상황에도 데이터를 유지할 수 있도록 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.527-530
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• 2005

센서 네트워크는 다수의 센서 노드들이 싱크(sink) 노드와 데이터 중심(Data centric) 기반으로 통신을 하게 되는데 이때 사용되는 라우팅 알고리즘 중 한 가지가 Directed Diffusion이다. Directed Diffusion 은 싱크(sink)의 named data 질의 방송(diffuse)에 기반을 둔 라우팅 프로토콜(protocol)로 다수의 소스 노드와 다수의 싱크 노드의 상황에서도 효율적으로 동작한다는 점과 각각의 질의에 의한 라우팅 경로 중에 aggregation 과 caching을 수행할 수 있다는 장점을 갖는다. 그러나 강화된 gradient 패스를 얻기 위해 요구되는 부담이 크다는 단점을 갖는다. 따라서 본 연구에서는 interest 패킷에 hop-count를 도입하여 gradient가 과다하게 설정되는 것을 제한함으로써 에너지 사용 효율을 높일 수 있는 개선된 Directed Diffusion 알고리즘을 제시한다. 또한 시뮬레이션을 통해 제안된 알고리즘의 유용성 확인을 확인하고자 한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.53-64
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• 2005

Previous secure routing protocols for wireless sensor networks assume that a sink is static. In many cases, however, a sink operated by man or vehicle is moving. A mobile sink creates a lot of technical problems such as reconfiguration of routing path exposure of sink location. and selection of secure access point node, which are not considered by many previous researches. In this paper, we propose a new secure routing scheme for solving such problems using hi-directional hash chain and delegation nodes of grid structure. This scheme provides a secure routing path and prevents attacker from recognizing the location of a mobile sink in sensor networks. This new method reduces the resource requirements compared to the cashed routing schemes. Simulation results also show that the system is secure and efficient enough.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.563-564
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• 2020

본 논문에서는 이동형 군집형 센서 시스템에서 상황에 따른 경로 변경에 대해 고려한다. 이동형 군집형 센서 시템은 임무 수행을 위해 무선으로 상호 네트워크 연결을 유지한 채로 그룹 이동을 수행한다. 이러한 그룹 이동의 경우 경로 변경의 상황에서 싱크 시스템의 명령에 따라 경로 변경을 수행한다. 그러므로 본 논문에서는 이동 센서 시스템들의 경로 변경을 발생하는 환경에 대해 고려한다.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.1
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• pp.47-55
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• 2009

Bot is a kind of worm/virus that is remotely controlled by a herder. Bot can be used to launch distributed denial-of-service(DDoS) attacks or send spam e-mails etc. Launching cyber attacks using malicious Bots is motivated by increased monetary gain which is not the objective of worm/virus. However, it is very difficult for infected user to detect this infection of Botnet which becomes more serious problems. This is why botnet is a dangerous, malicious program. The Bot DNS Sinkhole is a domestic bot mitigation scheme which will be proved in this paper as one of an efficient ways to prevent malicious activities caused by bots and command/control servers. In this paper, we analysis botnet activities over more than one-year period, including Bot's lifetime, Bot command/control server's characterizing. And we analysis more efficient ways to prevent botnet activities. We have showed that DNS sinkhole scheme is one of the most effective Bot mitigation schemes.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.201-207
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• 2013

Voice Recognition technique has been developed and it has been actively applied to various information devices such as smart phones and car navigation system. But the basic research technique related the speech recognition is based on research results in English. Since the lip sync producing generally requires tedious hand work of animators and it serious affects the animation producing cost and development period to get a high quality lip animation. In this research, a real time processed automatic lip sync algorithm for virtual characters in digital contents is studied by considering Korean vocal sound system. This suggested algorithm contributes to produce a natural lip animation with the lower producing cost and the shorter development period.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5467-5473
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• 2014

This study examined the numerical analysis results with respect to the thermal behavior of a natural convection cooled pin-fin heat sink. The heat sink consisted of pin fins integrated with plate fins. The heat sinks were designed with two different types to fit the limited internal space. The two types of heat sinks designed were analyzed using the ANSYS software package, and the numerical analysis results were compared with the cooling performance of the two types of heat sinks. The results of the simulation were analyzed according to the temperature distribution and air flow characteristics, heat flux etc. This study examined the correlation of the cooling performance with the heat sink internal structure and fin shape. FEM (Finite Element Method) confirmed the cooling performance of heat sink type A under natural convection conditions as the best results. The results of the numerical simulation showed that the heat sink type A shape showed an approximately 70 percent better heat transfer rate with natural convection than that of type B.