• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.4
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• pp.206-216
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• 2010

Wireless sensor networks (WSNs) are used to collect various data in environment monitoring applications. A spatial clustering may reduce energy consumption of data collection by partitioning the WSN into a set of spatial clusters with similar sensing data. For each cluster, only a few sensor nodes (samplers) report their sensing data to a base station (BS). The BS may predict the missed data of non-samplers using the spatial correlations between sensor nodes. ASAP is a representative data collection algorithm using the spatial clustering. It periodically reconstructs the entire network into new clusters to accommodate to the change of spatial correlations, which results in high message overhead. In this paper, we propose a new data collection algorithm, name EPDC (Energy-efficient Periodic Data Collection). Unlike ASAP, EPDC identifies a specific cluster consisting of many dissimilar sensor nodes. Then it reconstructs only the cluster into subclusters each of which includes strongly correlated sensor nodes. EPDC also tries to reduce the message overhead by incorporating a judicious probabilistic model transfer method. We evaluate the performance of EPDC and ASAP using a simulation model. The experiment results show that the performance improvement of EPDC is up to 84% compared to ASAP.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.349-357
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• 2006

The purpose of this study is to evaluate the water pollution degree in the Mid-Nakdong River watershed regarding to landcover types using GIS method. As a result of landcover classification, rate of urban appeared highly on Daegu Metropolitan city. Also, rate of agriculture showed highly in the riparian zones of the Nakdong and Guemho River and rate of forest appeared highly in the borders of the study area. To identify the groups of watershed with similar landcover patterns using the Cluster Analysis. According to the cluster analysis, the fifty sub-watersheds were grouped in three clusters, 'Urban watershed', 'Agriculture watershed', 'Forest watershed'. The proportion of urban area in each cluster had a positive correlation with water pollution degree. Otherwise, the proportion of agriculture in the Agriculture watershed had a high positive correlation with water pollution degree. Therefore, it is necessary to estimate environmental capacity of water duality considering ecological and environmental characteristics of watershed ecosystem and expand water duality monitoring systems to small stream.

• Journal of architectural history
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• v.3 no.2 s.6
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• pp.9-28
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• 1994

A collective theory is tried in analysis on the architectural history of Temple Gowoon in Gyongbook Province. For this purpose, firstly, the chronicle of construction was composed based on the critical study of the old documents. Secondly, the drawings of existing facilities were made after the field survey. And lastly, the collective theory was be able to extracted from the relation between chronicle and physical composion of the Temple Gowoon. The whole temple is composed of two territories, northern one and southern, which are divided by the central ravine. Northern territory was enlarged from Gukrakgeon's cluster through Myongboogeon's to Yeonsoogeon's. On the other hand, southern territory was reduced its position and its size from Daewoongeon's cluster, which was one of the main cluster, to Monigeon's, sub one. These processes were the results of the architectural adjustment, that is say, the dogmatic principles adapted in the topographical environments. The collective forms of clusters are different from each other. Gukrakgeon's cluster is composed of four buildings which enclose the empty inner court. Monigeon's is similar to the small temple type, Myongboogeon's selects the straggling form, and Yoensoogeon's has the type of Confucian shrine. The various types of clusters were the physical settings to symbolize the religious heirarchy of their buildigs. In the front of temple area, Gawoonloo, which located on the ravine and has a big volume, integrates straggling clusters.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.51.2-51.2
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• 2017

Diffuse radio relics are often detected in merging galaxy clusters and are emitted by synchrotron process. Radio relics are believed to trace the shock waves in the intracluster medium induced by ram pressure during a major cluster merger. Radio halos and relics are found in approximately 50 galaxy clusters to date that are all in a state of merging. The rarest of these galaxy clusters contain pairs of relics of similar brightness as well as a radio halo. The massive galaxy cluster PLCKG287.0+32.9 belongs to this rare population and is the second most significant detection from the Planck SZ All-sky Survey. Perhaps even more intriguing is that the radio relics are observed at vastly different distances from the X-ray peak requiring a complex merging scenario. In this study, we use weak-lensing to peer deeper into the merging scenario by reconstructing the dark matter distribution. We relate the mass distribution to the radio, X-ray, and optical emissions to provide constraints for future simulations of the merger. Fitting an NFW profile to the tangential shear we infer the mass of the cluster and discuss its implications for the merging scenario.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.580-588
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• 2016

Energy efficiency is the main objective in the design of a wireless sensor network (WSN). In many applications, sensing data must be transmitted from sources to a sink in a timely manner. This paper describes an investigation of the trade-off between two objectives in WSN design: minimizing energy consumption and minimizing end-to-end delay. We first propose a new distributed clustering approach to determining the best clusterhead for each cluster by considering both energy consumption and end-to-end delay requirements. Next, we propose a new energy-cost function and a new end-to-end delay function for use in an inter-cluster routing algorithm. We present a multi-hop routing algorithm for use in disseminating sensing data from clusterheads to a sink at the minimum energy cost subject to an end-to-end delay constraint. The results of a simulation are consistent with our theoretical analysis results and show that our proposed performs much better than similar protocols in terms of energy consumption and end-to-end delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3714-3732
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• 2019

With the rapid development of network, Intrusion Detection System(IDS) plays a more and more important role in network applications. Many data mining algorithms are used to build IDS. However, due to the advent of big data era, massive data are generated. When dealing with large-scale data sets, most data mining algorithms suffer from a high computational burden which makes IDS much less efficient. To build an efficient IDS over big data, we propose a classification algorithm based on data clustering and data reduction. In the training stage, the training data are divided into clusters with similar size by Mini Batch K-Means algorithm, meanwhile, the center of each cluster is used as its index. Then, we select representative instances for each cluster to perform the task of data reduction and use the clusters that consist of representative instances to build a K-Nearest Neighbor(KNN) detection model. In the detection stage, we sort clusters according to the distances between the test sample and cluster indexes, and obtain k nearest clusters where we find k nearest neighbors. Experimental results show that searching neighbors by cluster indexes reduces the computational complexity significantly, and classification with reduced data of representative instances not only improves the efficiency, but also maintains high accuracy.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.32.2-32.2
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• 2020

Massive Compact Elliptical Galaxies (MCEGs) found in the local universe are as massive as normal galaxies but extremely compact (M∗ > 1011 Msun, Reff < 1.5 kpc). They are considered to be the relics of red nugget galaxies found at high redshift. They are not likely to have undergone many mergers, keeping their original mass and size. Moreover, it is expected that they host a dominant population of red (metal-rich) globular clusters rather than blue (metal-poor) ones. Indeed, Beasley et al. (2018) found that the color distribution of the cluster system of NGC 1277 is unimodal, showing only a red population. However, NGC 1277 is the only case whose cluster system was studied among MCEGs. In this study, we investigate globular cluster systems of 14 nearby MCEGs with a homogeneous data set of HST/WFC3 F814W/F160W archive images. We detect tens to hundreds of globular clusters in each galaxy and examine their color distributions. Surprisingly, the fractions of red globular clusters are similar to those of normal galaxies, and are much lower than that of NGC 1277. We additionally obtain Gemini/GMOS-N g'r'i' images of PGC 70520, one of the 14 nearby MCEGs, to detect more globular clusters from deeper and wider images. We will discuss the results from the Gemini data combined with the results from the HST data in relation with the formation of MCEGs.

• The Journal of the Korea Contents Association
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• v.11 no.12
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• pp.145-151
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• 2011

This study assumed the competitive structure based on genre classification for Korean online game contents market, and carried out the analysis on the degree and characteristics of the competition that appear differently in each sub market classified according to the genre. First, to analyze the market power of the rank 1 and 2 game contents in each genre, using the play time share ratio and standard deviation statistics values in the genre, ANOVA analysis and Cluster analysis were carried out for each genre. According to ANOVA analysis result, in the rank 1 game share ratio in each genre, there was a relationship of 'FPS/Racing > RST/Sports > Poker > Go-stop > RPG > Arcade > Board', and in the play time total share ratio of rank 1 and 2 games, the relationship of 'RTS > FPS/Racing > Sports > RPG > Go-stop > Poker > Arcade > Board' was verified. And in Cluster analysis, the groups of the genres with the degree of market power tendency and the variability at similar level were classified and stated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5B
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• pp.721-733
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• 2010

In this paper, we propose a scalable content-based routing scheme for the tactical mobile ad-hoc networks where the nodes usually move together forming a group. Our scheme is classified as a content-based routing scheme based on publish and subscribe model. The nodes compose a cluster according to their position and interest. Our scheme allows multi-level cluster nesting. As a publish/subscribe model does, each node announces its interest to the cluster head who aggregates and announces the interests from cluster members to its neighbor cluster head. Actual data messages are delivered to the end node via cluster header in the reverse direction of the interest announcement. Using Qualnet simulator, we evaluated the performance of our scheme in comparison with two well-known content-based routing schemes. Simulation results show that our scheme maintains higher message delivery ratio as number of nodes increases whereas the two schemes show much lower delivery ratio. In addition, as the group mobility gets faster our scheme incurs less or similar control message overhead compared with the two schemes.

• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.949-960
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• 2016

This paper uses all sections of highway data (VDS) for two years (Jan. 2014-Dec. 2015), with 15 minute units. The first purpose of this study is to find clusters with similar patterns that appear repeatedly with time variables of month, week and hour. The cluster analysis results indicate a variety of patterns of average traffic speeds by time variables depending on the clusters; subsequently, these can be utilized to model for the forecast of the speed at a specific time. The second purpose is to do cluster analysis for grouping sections by effect nets that are closely related to each other. For the similarity measure we use cross-correlation functions calculated after pre-whitening the speed of each section. The cluster analysis gets 19 clusters, and sections within a cluster are geographically close. These results are expected to help to forecast a real-time speed.