• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.1
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• pp.12-17
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• 2003

Optimal determination of cluster size has an effect on the result of clustering. In K-means algorithm, the difference of clustering performance is large by initial K. But the initial cluster size is determined by prior knowledge or subjectivity in most clustering process. This subjective determination may not be optimal. In this Paper, the genetic algorithm based optimal determination approach of cluster size is proposed for automatic determination of cluster size and performance upgrading of its result. The initial population based on attribution is generated for searching optimal cluster size. The fitness value is defined the inverse of dissimilarity summation. So this is converged to upgraded total performance. The mutation operation is used for local minima problem. Finally, the re-sampling of bootstrapping is used for computational time cost.

• Journal of Korea Multimedia Society
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• v.13 no.1
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• pp.1-9
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• 2010

Today's growth of the mobile communication infrastructure made mobile computing systems like cellular phones came next to or surpassed the desktop PCs in popularity due to their mobility. Although the performance of mobile devices is now being improved continuously, it is a current common sense that compute intensive large-scale applications can hardly run on any kind of mobile handset devices. To clear up this problem, we decided to exploit the mobile cluster computing system and surveyed the existing ones first. We found out, however, that most of them are not the actual implementations but a mobile cluster infrastructure proposal or idea suggestions for reliable mobile clustering. To make cell phones participated in cluster computing nodes, in this paper, we propose a redesigned JPVM cluster computing engine and a set of WIPI mobile runtime functions interfacing with it. And we also show the performance evaluation results of real parallel applications running on our Mobile-JPVM cluster computing systems. We find out by the performance evaluation that large-scale applications can sufficiently run on mobile devices such as cellular phones when using our mobile cluster computing engine.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4228-4247
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• 2018

Many methods have been developed for the vehicles to create clusters in vehicular ad hoc networks (VANETs). Usually, nodes are vehicles in the VANETs, and they are dynamic in nature. Clusters of vehicles are made for making the communication between the network nodes. Cluster Heads (CHs) are selected in each cluster for managing the whole cluster. This CH maintains the communication in the same cluster and with outside the other cluster. The lifetime of the cluster should be longer for increasing the performance of the network. Meanwhile, lesser the CH's in the network also lead to efficient communication in the VANETs. In this paper, a novel algorithm for clustering which is based on the social behavior of Gray Wolf Optimization (GWO) for VANET named as Intelligent Clustering using Gray Wolf Optimization (ICGWO) is proposed. This clustering based algorithm provides the optimized solution for smooth and robust communication in the VANETs. The key parameters of proposed algorithm are grid size, load balance factor (LBF), the speed of the nodes, directions and transmission range. The ICGWO is compared with the well-known meta-heuristics, Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO) for clustering in VANETs. Experiments are performed by varying the key parameters of the ICGWO, for measuring the effectiveness of the proposed algorithm. These parameters include grid sizes, transmission ranges, and a number of nodes. The effectiveness of the proposed algorithm is evaluated in terms of optimization of number of cluster with respect to transmission range, grid size and number of nodes. ICGWO selects the 10% of the nodes as CHs where as CLPSO and MOPSO selects the 13% and 14% respectively.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.10
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• pp.539-549
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• 2002

PC cluster-based Information Retrieval (IR) systems improve their performances by parallel processing of query terms using cluster nodes. However TCP/IP based communication used to exchange data between cluster nodes prevents the performance from being improved further. The user-level communication mechanisms solve the problem by eliminating the time-consuming kernel access in exchanging data between cluster nodes. The Virtual Interface Architecture (VIA) is one of the representative user-level communication mechanisms which provide low latency and high bandwidth. In this paper, we propose a VIA-based parallel IR system on a PC cluster. The IR system is implemented using the following three communication methods: Sealable Coherent Interface (SCI) based VIA, MPI on SCI based VIA, MPI on Fast Ethernet based VIA. Through experiments, the performances of the three methods are analyzed in various aspects.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3494-3510
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• 2019

Wireless sensor networks encounter energy saving as a major issue as the sensor nodes having no rechargeable batteries and also the resources are limited. Clustering of sensors play a pivotal role in energy saving of the deployed sensor nodes. However, in the cluster based wireless sensor network, the cluster heads tend to consume more energy for additional functions such as reception of data, aggregation and transmission of the received data to the base station. So, careful selection of cluster head and formation of cluster plays vital role in energy conservation and enhancement of lifetime of the wireless sensor networks. This study proposes a new mutation chemical reaction optimization (MCRO) which is an algorithm based energy efficient clustering protocol termed as MCRO-ECP, for wireless sensor networks. The proposed protocol is extensively developed with effective methods such as potential energy function and molecular structure encoding for cluster head selection and cluster formation. While developing potential functions for energy conservation, the following parameters are taken into account: neighbor node distance, base station distance, ratio of energy, intra-cluster distance, and CH node degree to make the MCRO-ECP protocol to be potential energy conserver. The proposed protocol is studied extensively and tested elaborately on NS2.35 Simulator under various senarios like varying the number of sensor nodes and CHs. A comparative study between the simulation results derived from the proposed MCRO-ECP protocol and the results of the already existing protocol, shows that MCRO-ECP protocol produces significantly better results in energy conservation, increase network life time, packets received by the BS and the convergence rate.

• Information Systems Review
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• v.5 no.2
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• pp.241-256
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• 2003

This empirical study is to explain critical success factors for building effective regional IT cluster from the literature reviews which have some limitations, and is to suggest new key factors from the views of Regional Innovation System and Sectoral Systems of Innovation. For building successful cluster, the new key factors not only stress on regional networks, the spill-over of tacit knowledge through learning by interacting, institutions which contain regional custom, norms, established practices, culture, and characteristics from the Regional Innovation System, but also emphasize on heterogeneous agents who are interacting by each others from Sectoral Systems of Innovation. From these factors we suggest some strategies for building effective "Daegu IT Cluster" as following; making characterized IT brands which are selected and concentrated based on regional and IT sectoral characteristics, strengthening learning competence of tacit knowledge built in multiple heterogeneous agents network, establishing strong agent networks which are composed of universities, companies, institutes and government, and sharing the institution of mind-opening culture in order to correspond with environmental changes and link to other industrial clusters. By putting above strategies in force, the compatabilities of Daegu region are reinforced. Tacit knowledges spill over and the regional innovation competence are accumulated. Also IT cluster plays core role of employment in Daegu for long term. Especially, "Daegu IT Cluster" changes city's image from medium and small manufacturing city to new industrial city based on high technologies.

• World Technopolis Review
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• v.4 no.2
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• pp.87-103
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• 2015

This paper aims to explore how firms develop and grow in regional clusters based in a developing country. The argument is that start-ups / small and large firms are able to grow by developing linkages or networks for resources within clusters - and this tenet is based on studies of firms that are based from such clusters as Silicon Valley in the US, Cambridge in UK and other clusters from which have evolved over long periods of time. Most of the time we hear narratives from the developed world where there are brownfield cluster development efforts. In developing countries governments are making efforts to develop clusters from scratch - which in this paper we term as greenfield cluster versus a brownfield development, which is where the cluster is developed based on existing and new organisations in a region. In this paper, we believe the context of clusters can be important in determining the way firms develop linkages for their growth - and we look at two contexts in Malaysia ie. A greenfield cluster and a brownfield cluster. The paper presents findings from case studies of firms in a greenfield cluster (Cyberjaya) and a brown field cluster (Penang) in Malaysia. The cases reveal fairly different approaches to development of linkages or networks, which we hope will provides insights to cluster development officials and policy makers and implications to researchers for developing studies of clusters and innovation systems.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.261-268
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• 2001

With the rapid growth of the Internet, various web-based businesses are creating a new environment in an imaginary space. However, this expanding Internet and user increase cause an overflow of transmission and numerous subordinate problems. To solve these problems, a parallel cluster system is produced using different methods. This thesis recommends a multi0distribution cluster group. It constructs a MPP dynamic distribution sub-cluster group using numerous low-priced and low-speed systems. This constructed sub-cluster group is then connected with a singular virtual IP to finally serve the needs of clients (users). This multi-distribution cluster group consists of an upper structure based on LVS and a dynamic serve cluster group centered around an SC-server. It conducts the workloads required from users in a parallel process. In addition to the web service, this multi-distribution cluster group can efficiently be utilized for the calculations which require database controls and a great number of parallel calculations as well as additional controls with result from the congestion of service.

• Journal of Information Processing Systems
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• v.10 no.1
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• pp.36-54
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• 2014

Resource sharing is a major advantage of distributed computing. However, a distributed computing system may have some physical or virtual resource that may be accessible by a single process at a time. The mutual exclusion issue is to ensure that no more than one process at a time is allowed to access some shared resource. The article proposes a token-based mutual exclusion algorithm for the clustered mobile ad hoc networks (MANETs). The mechanism that is adapted to handle token passing at the inter-cluster level is different from that at the intra-cluster level. It makes our algorithm message efficient and thus suitable for MANETs. In the interest of efficiency, we implemented a centralized token passing scheme at the intra-cluster level. The centralized schemes are inherently failure prone. Thus, we have presented an intra-cluster token passing scheme that is able to tolerate a failure. In order to enhance reliability, we applied a distributed token circulation scheme at the inter-cluster level. More importantly, the message complexity of the proposed algorithm is independent of N, which is the total number of nodes in the system. Also, under a heavy load, it turns out to be inversely proportional to n, which is the (average) number of nodes per each cluster. We substantiated our claim with the correctness proof, complexity analysis, and simulation results. In the end, we present a simple approach to make our protocol fault tolerant.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4223-4249
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• 2015

A novel jamming detection technique to detect the presence of jamming in the downstream direction for cluster based wireless sensor networks is proposed in this paper. The proposed technique is deployed in base station and in cluster heads. The proposed technique is novel in two aspects: Firstly, whenever a cluster head receives a packet it verifies whether the source node is legitimate node or new node. Secondly if a source node is declared as new node in the first step, then this technique observes the behavior of the new node to find whether the new node is legitimate node or jammed node. In order to monitor the behavior of the existing node and new node, the second step uses two metrics namely packet delivery ratio (PDR) and received signal strength indicator (RSSI). The rationality of using PDR and RSSI is presented by performing statistical test. PDR and RSSI of every member in the cluster is measured and assessed by the cluster head. And finally the cluster head determines whether the members of the cluster are jammed or not. The CH can detect the presence of jamming in the cluster at member level. The base station can detect the presence of jamming in the wireless sensor network at CH level. The simulation result shows that the proposed technique performs extremely well and achieves jamming detection rate as high as 99.85%.