• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.291-298
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• 2010

In wireless sensor networks, energy is the most important consideration because the lifetime of the sensor node is limited by battery. The clustering is the one of methods used to manage network energy consumption efficiently and LEACH(Low-Energy Adaptive Clustering Hierarchy) is one of the most famous clustering algorithms. LEACH utilizes randomized rotation of cluster-head to evenly distribute the energy load among the sensor nodes in the network. The random selection method of cluster-head does not guarantee the number of cluster-heads produced in each round to be equal to expected optimal value. And, the cluster head in a high-density cluster has an overload condition. In this paper, we proposed both a token based cluster-head selection algorithm for guarantee the number of cluster-heads and a cluster selection algorithm for uniform-density cluster. Through simulation, it is shown that the proposed algorithm improve the network lifetime about 9.3% better than LEACH.

• Journal of the Korean earth science society
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• v.34 no.2
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• pp.148-161
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• 2013

The purpose of the study was to investigate the relationship between the communication status in group and the semantic network of science gifted students. Seven small groups, 5 members in each, participated in small group activities, in which they discussed the calculation of earth density. Both the communication status in group and the semantic network of science gifted students were analyzed using KrKwic, Ucinet 6.0 for Windows. As a result, the semantic network of prime movers in group represented more frequently used words, lesser rate of component, and higher density than that of out lookers. It means that the prime movers have coherent knowledge compared to out lookers, and they output more knowledge for problem solving than out lookers. Therefore, the results of this study may be applied to evaluating the cognitive level of science gifted students and group organization for small group activity.

• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.147-154
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• 2007

Network topology in ad hoc networks keeps changing because of node mobility and no limitation in number of nodes. Therefore, the scalability of routing protocol is of great importance, However, table driven protocols such as DSDV have been known to be suitable for relatively small number of nodes and low node mobility, Various protocols like FSR, OLSR, and PCDV have been proposed to resolve scalability problem but vet remain to be proven for their comparative superiority for scalability, In this paper, we compare and amine them by employing various network deployment scenarios as follows: network dimension increase's while keeping node density constant node density increases while keeping network dimension fixed, and the number of sessions increase with the network dimension and the number of nodes fixed. the DSDV protocol showed a low scalability despite that it imposes a low overhead because its convergence speed against topology change is slow, The FSR's performance decreased according to the increase of overhead corresponding to increasing number of nodes, The OLSR with the shortest convergence time among them shows a good scalability, but turned out to be less scalable than the PCDV that uses a clustering because of its relatively high overhead.

• Journal of Korea Technology Innovation Society
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• v.10 no.4
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• pp.605-628
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• 2007

We analyze the embedded structure of the cooperative research network of innovation studies in Korea by employing the social network methodology. The network covers all the contributing authors of two journals such as JTI and KTIS, which are the representative journals in the area. Across the networks, the following is noted: networks are highly segmented and the link density is low. However, the KTIS network contains a huge component with 131 authors which implies the existence of a strong cooperative research infrastructure. We derived three sub-networks such as technology economics, technology management, and technology policy. The technology policy network has the lowest link density, while the technology management network of KTIS shows relatively high cohesion among the researchers. Simulation analysis for the mean links of networks by author affiliation divided into university and others show no significant difference between the two networks. We also found a higher ratio of linkage within affiliated network than between networks, rejecting our hypothesis that researchers will not discriminate their research partners due to strong governmental inducement of academia-res each-industry cooperation. The explainability of indices from network structure such as structural holes and clustering coefficients on the performance of researchers measured by the number of citations confirms the results reported in Oh, Choi & Kim (2006) which dealt with the research network of information systems.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.3
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• pp.50-57
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• 2009

We propose a network node search scheme to address the network fragmentation due to high node mobility in the VANET. VANET is very similar to MANET in that a multi-hop ad-hoc network is configured by wireless communication between vehicles without any network infrastructure. However, high speed mobility, high node density, and frequent topology change induce frequent network fragmentation so that overall network traffic can be increased. In this paper, new broadcasting protocol called an adaptive relay node search protocol is proposed to decrease the network fragmentation. It reduces the network fragmentation and network traffic by researching nodes outside the dangerous area only in case of network fragmentation. Simulation results show that the proposed protocol decreases network fragmentation by up to 39.9% and increase informed rate by up to 41.9% compared to the existing broadcasting protocol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.105-107
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• 2015

In this paper, we proposed LTD(Load Tolerance Density-distribution) algorithm using dynamic density for analyzing distribute routing path. MANET(Mobile Ad-hoc Networks) consists of the node that has a mobility. By the Mobility, the topology is exchanged frequently. To reduce the exchange of topology, the hierarchy network is studied. However, if the load is concentrated at the cluster head node, the communication is disconnected. the proposed algorithm measure the dynamic density of the node using poisson distribution. And this algorithm provides distribute routing path using dynamic density. The simulation results, the proposed algorithm shows improved packet delivery ratio than the compared algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1241-1248
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• 2014

An efficient battery usage of sensor nodes is main goal in a sensor network, which is the substructure of Internet of Things. Maximizing the battery usage of sensor nodes makes the lifetime of sensor network increase as well as the reliability of the network improved. The previous solutions to solve these problems are mainly focused on the cluster head selection based on the remaining energy. In this paper, we consider both the head selection and the replacement interval which is determined by a threshold that is based on the remaining energy, density of alive nodes, and location. Our simulation results show that the proposed scheme has outstanding contribution in terms of maximizing the life time of the network and balancing energy consumption of all nodes.

• Electronics and Telecommunications Trends
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• v.17 no.5 s.77
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• pp.37-46
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• 2002

이동통신에서는 무선자원의 효율적인 사용을 위하여 variable rate vocoder 및 VoX 기법을 이용한 음성 전송이 일반적 추세이며, 버스티 특성을 갖는 패킷 트래픽의 경우 statistical multiplexing을 이용하여 무선 채널의 사용을 극대화 시킨다. 트래픽 밀도를 나타내는 Erlang 용량은 일정속도의 회선교환 트래픽에 대하여 동시에 점유할 수 있는 dedicated circuit의 수에 기초하는 개념이므로 statistical multiplexing으로 처리되는 데이터 패킷의 트래픽 밀도는 queuing model에 근거한 데이터 스루풋이 현실적이다. 그러나 이동통신 시스템에서 트래픽 특성을 달리하는 circuit 및 패킷 타입의 혼합 서비스가 동시에 제공될 경우 네트워크 planning을 위한 구성 시스템의 용량산정을 위해 트래픽 밀도의 통합적인 표현을 요구한다. 따라서 Erlang 용량과 데이터 스루풋의 상호 변환을 통하여 네트워크 구성요소의 용량 산정에 적당한 용량표현을 선택할 수 있다. 본 고에서는 트래픽 처리기로서의 통신시스템을 기술하기 위하여 일반적인 텔레트래픽 시스템 모델과 파라미터를 정의한다. 또한 음성 및 비음성 서비스의 혼합 트래픽 환경에서 트래픽 밀도계산을 위한 Erlang 용량과 데이터 스루풋의 상호 변환 관계를 소개한다. 마지막으로 3G1x 무선접속환경에서 음성 및 HSPD 서비스가 공존할 경우 기지국 CE dimensioning에 필요한 혼합 트래픽 Erlang 용량 산출 방법을 기술한다.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.44-54
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• 2012

In wireless sensor networks, a moving object tracking scheme is one of core technologies for real applications such as environment monitering and enemy moving tracking in military areas. However, no works have been carried out on processing the failure of object tracking in sparse sensor networks with holes. Therefore, the energy consumption in the existing schemes significantly increases due to plenty of failures of moving object tracking. To overcome this problem, we propose a novel moving object tracking scheme based on polynomial regression prediction in sparse sensor networks. The proposed scheme activates the minimum sensor nodes by predicting the trajectory of an object based on polynomial regression analysis. Moreover, in the case of the failure of moving object tracking, it just activates only the boundary nodes of a hole for failure recovery. By doing so, the proposed scheme reduces the energy consumption and ensures the high accuracy for object tracking in the sensor network with holes. To show the superiority of our proposed scheme, we compare it with the existing scheme. Our experimental results show that our proposed scheme reduces about 47% energy consumption for object tracking over the existing scheme and achieves about 91% accuracy of object tracking even in sensor networks with holes.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.179-186
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• 2020

The purposes of this paper were: 1) to identify the structural changes of the northeast Asia airport network caused by the pandemic of COVID-19 using social network analysis (SNA) and 2) to suggest proposals for improving airport competitiveness. In this respect, the entire international air routes in northeast Asia airport collected data of 4-10 March 2019 and 9-15 March 2020 through schedules analyzer database of OAG. We found that both the density and centrality have decreased since the spread of COVID-19. The government and airport authorities need active support such as a reduction of various fees and a moratorium on transportation rights to overcome the crisis in the air transport industry. When the COVID-19 situation calms down in the future, we hope that further research will be conducted to identify the structural changes in the SNA aspects through the vast data establishment in countries such as the EU and America.