• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.45-48
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• 2003

Ad hoc network는 무선 노드들의 집합으로서 어떤 인프라스트럭처 도움 없이 그들 서로가 multi-hop 경로를 통해 통신한다. 네트워크를 구성하는 노드들의 움직임이 빈번히 발생하기 때문에 클러스터간 노드들의 재 가입이 계속되므로 네트워크의 안정성을 유지하기 어렵다. 그러므로 최대한 네트워크 토폴로지의 안정성을 유지하는 것이 필요하다. 본 논문에서는 ad hoc network를 구성하는 노드들을 클러스터로 형성한 후 제한된 broadcast 메커니즘을 이용하여 네트워크의 제어 메시지 flooding 수를 줄이는 효율적인 라우팅 방법을 제안한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.709-712
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• 2010

A military tactical information communication network uses no base station and all mobile terminal are independent while mobile networks use an infra structure that a fixed base station supports many mobile terminals. A clustering system is more efficient than the existing one in small Ad-hoc network using a limited message size. The development of an adaptive clustering algorithm is necessary to maximize the network efficiency via a study on a clustering for military tactical information communication network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1661-1669
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• 2010

In this paper, I propose an Energy efficient Clustering based on Genetic Algorithm(ECGA) which reduces energy consumption by distributing energy overload to cluster group head and cluster head in order to lengthen the lifetime of sensor network. ECGA algorithm calculates the values like estimated energy cost summary, average and standard deviation of residual quantity of sensor node and applies them to fitness function. By using the fitness function, we can obtain the optimum condition of cluster group and cluster. I demonstrated that ECGA algorithm reduces the energy consumption and lengthens the lifetime of network compared with the previous clustering method by stimulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.608-614
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• 2009

In wireless sensor networks, there are hundreds to thousands of small battery powered devices which are called sensors. As sensors have a limited energy resources, there is a need to use it effectively. A clustering based routing protocol forms clusters by distributed algorithm. Member nodes send their data to their cluster heads then cluster heads integrate data and send to sink node. In this paper we propose an energy efficient cluster-head selection algorithm. We have used some factors(a previous cluster head experience, a existence of data to transmit and an information that neighbors have data or not) to select optimum cluster-head and eventually improve network lifetime. Our simulation results show its effectiveness in balancing energy consumption and prolonging the network lifetime compared with LEACH and HEED algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.1001-1008
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• 2015

Mobile Ad hoc Network(MANET) consists of a node that has mobility. In MANET, the node has routing, the node builds a network of their own, no dependent infrastructure. Topology are exchanged due to node mobility in MANET. For reducing the change of topology, hierarchical network algorithm has been investigated. In hierarchical network, cluster member node communicates through cluster head node. When the load-balancing of cluster head node is exceed, assigned cluster member node can't communicate with base station. To solve this problem, we proposed Load Tolerance algorithm. The proposed algorithm, when cluster member node can't send a message by cluster head node that exceed load-balancing, then the cluster member node sends a message by selected load tolerance node. Through a simulation, the proposed algorithm improves packet delivery ratio in cluster routing.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.77-86
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• 2008

Traditional cluster-based routing method is a representative method for increasing the energy efficiencies. In these cluster-based routing methods, the selected cluster head collect/aggregate the information and send the aggregated information to the base station. But they have to solve the unnecessary energy dissipation of frequent information exchange between the cluster head and whole member nodes in cluster. In this paper, we minimize the frequency of the information exchange for reducing the unnecessary transmit/receive frequencies as calculate the overlapped area or number of overlapped member nodes between the selected cluster head and previous cluster head in the setup phase. And besides, we consider the direction of super cluster head for optimal cluster formation. So, we propose the modified cluster selection scheme that optimizes the energy dissipation in the setup phase and reuses the saved energy in the steady phase efficiently that prolongs the whole wireless sensor network lifetime by uniformly selecting the cluster head.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2006.11b
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• pp.27-45
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• 2006

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.703-707
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• 1998

• Journal of the Korean association of regional geographers
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• v.21 no.3
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• pp.489-502
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• 2015

Sometimes called the Silicon Fen, the Cambridge cluster is well known as the most innovative hi-tech cluster in the world. This paper attempts to explore the evolutionary dynamics of the Cambridge cluster, drawing upon the triple-helix approach. To understand the evolutionary dynamics of the Cambridge cluster, it is important to examine the role and impact of the University of Cambridge, which is conceived as one of the best higher educational institutions in the world. The Cambridge cluster has been evolved on the basis of a strong university-industry relationship. University spin-outs have a long tradition in Cambridge with the history of more than a century, and they have played a critical role in making the cluster more innovative. Business networks and social capital molded for a long time in the region become a foundation for active local spin-out activities. However, since 2000 the central government started steadily to require British universities to be an entrepreneurial university, with the purpose of the reduction of university subsidies. As a result of this, spin-out activities in the Cambridge cluster show a sharp decline, which is a factor of threatening the dynamic evolution of the cluster.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.68-77
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• 2012

Flow characteristics of base region of small scaled 4 nozzle clustered engine has been analyzed with CFD approach along with the tests of numerical methods. The numerical test shows that Spalart-Allmaras turbulence model is appropriate for the present research. Plumes expanded from nozzles exits collide with each other and make high pressure stagnation region. Some of collided plumes expand again reversely into the base region with supersonic speeds. The reversed plume in the base region goes out to the outer region through the minimum vent area formed by the nearest nozzle exterior surfaces. But different from the empirical theory, the minimum vent area does not play a role of throat. Additionally the temperature of the nozzle inner surface strongly affects the temperature of the reversed plumes.