• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1661-1678
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• 2016

Clustering is one of the key technologies in vehicular networks. Constructing and maintaining stable clusters is a challenging task in high mobility environments. DWCM (Distributed and Weighted Clustering based on Mobility Metrics) is proposed in this paper based on the d-hop dominating set of the network. Each vehicle is assigned a priority that describes the cluster relationship. The cluster structure is determined according to the d-hop dominating set, where the vehicles in the d-hop dominating set act as the cluster head nodes. In addition, cluster maintenance handles the cluster structure changes caused by node mobility. The rationality of the proposed algorithm is proven. Simulation results in the NS-2 and VanetMobiSim integrated environment demonstrate the performance advantages.

• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.13-18
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• 2010

In order to prepare the technical fundamental in production of premium quality fruits of 'Niitaka' pears, we compared the quality parameters and storability of the fruits that had various fruit set position in a cluster. The fruits set on $4^{th}$ from basal part in fruit cluster had the largest fruit size. The weight of fruits set on the higher position than $4^{th}$ from basal part in fruit cluster showed decreasing tendency. The production rates of marketable fruits which had 500g to 899g in weight were the high in $3-5^{th}$ from basal part in cluster than those in other position. The differences of fruit height and diameter which represent balanced fruit shape also showed less difference in the fruits set on $4-5^{th}$ from basal part in cluster than the fruits set closely on basal part in cluster. The fruits set on $3-4^{th}$ from basal part in cluster showed lower rate in incidence of core breakdown and pithiness disorder during 4 months of cold storage than those on the closer position to basal part in cluster.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.3
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• pp.337-340
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• 2004

The clustering problem can be formulated as the problem to find the number of clusters and a partition matrix from a given data set using the iterative or non-iterative algorithms. The author proposes a nearest neighbor and validity-based clustering algorithm where each data point in the data set is linked with the nearest neighbor data point to form initial clusters and then a cluster in the initial clusters is linked with the nearest neighbor cluster to form a new cluster. The linking between clusters is continued until no more linking is possible. An optimal set of clusters is identified by using the conventional cluster validity index. Experimental results on well-known data sets are provided to show the effectiveness of the proposed clustering algorithm.

• Journal of Environmental Science International
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• v.24 no.12
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• pp.1673-1679
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• 2015

This study was conducted to investigate the effects of fruit set internode on the germination of watermelon seeds. Generally fruits setted in higher than 20 internode were high percent of germination, fruit setted in low internode(5-10) is low. The higher fruit-set internode, fruit weight was significantly increased, but 1,000 seed weight was decreased the more fruit set internode. However number of seed was about 300 seeds irrespective of fruit-set internode. Investigating viability of seed by BP test, general percent germination was recorded highest at 5 flower cluster above 20 internode of fruit-set internode. In contrast, condition of fruit setted on 3, 4, 6 flower cluster were high percent of germination, regarded as unnormal germination not to be as normal seedling by 2~3%. Seed harvested at 5 flower-cluster had high viability on hypocotyl height and diameter of seedling through early growth test, but were not significant. Therefore 5 flower-cluster was optimum fruit-set internode to obtain high-quality seed.

• Korean Journal of Mathematics
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• v.14 no.1
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• pp.65-70
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• 2006

In this article, we mention some subsequent developments of the theory of cluster sets, and present a new boundary cluster set for a simply connected domain in the complex plane and its applications.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2806-2808
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• 2010

The structure of 3-aminophenol $(CO_2)_1$ cluster was computationally studied both in the ground and the lowest singlet excited electronic states. The ground state structure and binding energy of the cluster was investigated using the second-order M$\ddoot{o}$ller-Plesset perturbation theory (MP2) at the complete basis set (CBS) limit. The excited state geometry of the cluster was obtained at the second-order approximate coupled cluster (CC2) level with cc-pVDZ basis set, and the $S_0-S_1$ absorption spectrum was simulated by calculating Franck-Condon overlap integral. The ground state geometry of the global minimum with a very high binding energy of 4.3 kcal/mol was found for the cluster, due to the interaction between amino group and $CO_2$ in addition to the strong $\pi-\pi$ interaction between the aromatic ring and $CO_2$. The excited state geometry shows a very big shift in the position of $CO_2$ compared to the ground state geometry, which results in low intensity and broad envelope in the Franck-Condon simulation.

• Journal of agriculture & life science
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• v.46 no.1
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• pp.105-111
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• 2012

This study was conducted to evaluate the influence of fruit setting order by flower cluster on the fruit weight and the soluble solids content for the strawberry of 'Seolhyang' cultivar. The first flower cluster had higher fruit number, fruit weight, soluble solids content and ratio of large fruit compared to the second and third flower cluster. The fruit set on the upper position fruit in the same flower cluster had higher fruit weight and the soluble solids compared to the fruit set on the lower position fruit in the flower cluster. The fruit weight was highly positive correlated with the soluble solids content. The result indicated that the number of fruit set for marketable yield seemed to be 9-10 per the first flower cluster, 6 per the second flower cluster, 4 per the third flower cluster and 3 per the fourth flower cluster in 'Seolhyang' cultivar.

• Journal of Information Technology Applications and Management
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• v.26 no.1
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• pp.53-64
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• 2019

The purpose of this study is to find out the fast delivery route that several drones return a truck again after departing from it for delivery locations at each cluster while the truck goes through the cluster composed of several delivery locations. The main issue is to reduce the total delivery time composed of the delivery time by relatively slow trucks via clusters and the sum of maximum delivery times by relatively fast drones in each cluster. To solve this problem, we use a three-step heuristic approach. First, we cluster the nearby delivery locations with minimal number of clusters satisfying a constraint of drone flight distance to set delivery paths for drones in each cluster. Second, we set an optimal delivery route for a truck through centers of the clusters using the TSP model. Finally, we find out the moved centers of clusters while maintaining the delivery paths for the truck and drones and satisfying the constraint of drone flight. distance in the two-dimensional region to reduce the total delivery time. In order to analyze the effect of this study model according to the change of the number of delivery locations, we developed a R-based simulation prototype and compared the relative efficiency, and performed paired t-test between TSP model and the cluster-based models. This study showed its excellence through this experimentation.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.7
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• pp.51-60
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• 1997

Prototype based methods are commonly used in cluster analysis and the results may be highly dependent on the prototype used. In this paper, we propose a fuzzy clustering method that involves adaptively expanding convex polytopes. Thus, the dependency on the use of prototypes can be eliminated. The proposed method makes it possible to effectively represent an arbitrarily distributed data set without a priori knowledge of the number of clusters in the data set. Specifically, nonlinear membership functions are utilized to determine whether a new cluster is created or which vertex of the cluster should be expanded. For this, the membership function of a new vertex is assigned according to not only a distance measure between an incoming pattern vector and a current vertex, but also the amount how much the current vertex has been modified. Therefore, cluster expansion can be only allowed for one cluster per incoming pattern. Several experimental results are given to show the validity of our mehtod.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.810-819
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• 2010

This paper proposes an algorithm to improve total network lifetime for Wireless Sensor Network (WSN) application such as environmental condition monitoring systems based on LEACH protocol. Firstly, the algorithm had equal number of nodes allocated to each cluster at cluster set-up phase where it abided by LEACH protocol. Secondly, at cluster set-up phase, each node was determined the order to be cluster header of the cluster which it had joined. After then, the role of a cluster head delivers to the next node according to determined order when the cluster head has received certain number of packets. With above method energy consumption of each node made equal and overall network lifetime was increased. Simulation results shows that overall network lifetime of proposed algorithm was increased two times than that of LEACH and total energy consumption was one forth of that of LEACH protocol.