• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.83-93
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• 2012

This paper proposes an image segmentation framework that modifies the objective function of Fuzzy C-Means (FCM) to improve the performance and computational efficiency of the conventional FCM-based image segmentation. The proposed image segmentation framework includes a locally weighted fuzzy c-means (LWFCM) algorithm that takes into account the influence of neighboring pixels on the center pixel by assigning weights to the neighbors. Distance between a center pixel and a neighboring pixels are calculated within a window and these are basis for determining weights to indicate the importance of the memberships as well as to improve the clustering performance. We analyzed the segmentation performance of the proposed method by utilizing four eminent cluster validity functions such as partition coefficient ($V_{pc}$), partition entropy ($V_{pe}$), Xie-Bdni function ($V_{xb}$) and Fukuyama-Sugeno function ($V_{fs}$). Experimental results show that the proposed LWFCM outperforms other FCM algorithms (FCM, modified FCM, and spatial FCM, FCM with locally weighted information, fast generation FCM) in the cluster validity functions as well as both compactness and separation.

• Land and Housing Review
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• v.1 no.1
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• pp.51-57
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• 2010

The importance of seismic design is greatly emphasized recently in Korea, resulting in an increase in the number of dynamic analysis being performed. One of the most important input parameters for the dynamic seismic analysis is input ground motion. However, it is common practice to use recorded motions from U.S. or Japan without considering the seismic environment of Korea or synthetic motions generated in the frequency domain. The recorded motions are not suitable for the seismic environment of Korea since the variation in the duration and energy with the earthquake magnitude cannot be considered. The artificial motions generated in frequency domain used to generated design response spectrum compatible ground motion has the problem of generating motions that have different frequency characteristics compared to real recordings. In this study, an algorithm that generates target response spectrum compatible ground motions in time domain is used to generate a suite of input ground motions. The generated motions are shown to preserve the non-stationary characteristics of the real ground motion and at the same, almost perfectly match the design response spectrum.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.4
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• pp.463-469
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• 2010

Since MOLA(Mars Orbiter Laser Altimeter) data, which provides altimetry data for Mars, does not cover the whole Mars area, image matching with MOC imagery should be implemented for the generation of DEM. However, automatic image matching is difficult because of insufficient features and low contrast. In this paper, we present the area based semi-automatic image matching algorithm with MOC-NA(Mars Orbiter Camera ? Narrow Angle) imagery. To accomplish this, seed points describing conjugate points are manually added for the stereo imagery, and interesting points are automatically produced by using such seed points. Produced interesting points being used as initial conjugate points, area based image matching is implemented. For the points which fail to match, the locations of initial conjugate points are recalculated by using matched six points and image matching process is re-implemented. The quality assessment by reversing the role of target and search image shows 97.5 % of points were laid within one pixel absolute difference.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.167-174
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• 2007

This study proposes a practical and realistic method to establish an optimal lifetime maintenance strategy for deteriorating bridges by considering the life-cycle performance as well as the life-cycle cost. The proposed method offers a set of optimal tradeoff maintenance scenarios among other conflicting objectives, such as minimizing cost and maximizing performance. A genetic algorithm is used to generate a set of maintenance scenarios that is a multi-objective combinatorial optimization problem related to the and the life-cycle cost and performance as separate objective functions. A computer program, which generates optimal maintenance scenarios, was developed based on the proposed method. The subordinate relation between bridge members has been considered to decide optimal maintenance sequence. The developed program has been used to present a procedure for finding an optimal maintenance scenario for steel-girder bridges on the Korean National Road. Through this bridge maintenance scenario analysis, it is expected that the developed method and program can be effectively used to allow bridge managers an optimal maintenance strategy satisfying various constraints and requirements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.659-665
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• 2006

When using the Mobile IP which is the representative technology to secure the mobility in general IP networks, the packet loss during the handover is inescapable. To remedy the packet loss problem, the smooth handover was introduced. However, the smooth handover causes the packets sequence disruption during the packet forwarding procedure and it may result in the degradation of the network performance. The same problem also occurs in the WiBro (High-speed Portable Internet) system that is the next generation portable IP service system. The WiBro system, which provides the high speed data service just like xDSL and leased line in wired internet, aims to guarantee the portability, mobility, and the differentiated service based on IEEE 802.16. So, the handover mechanisms that solve the problems of packet loss and packet sequence distribution are required in the WiBro system. In this paper, we propose the handover mechanism and the packet sequence control algorithm that provide the reliability and the differentiated service for the unicast service in the WiBro system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.371-377
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• 2011

Users of the Information Age, IT usage patterns of the wired broadband information services and various forms of the same quality wireless multimedia services are required. Changes of these times the next-generation mobile communications (IMT-Advanced) has emerged as the necessity of developing its current voice and packet data communications on the move in the high-speed 100Mbps, 1Gbps in stationary and slow data transmission rates up to fixed-mobile convergence based on needed to provide ubiquitous service platform for the realization of IMT-Advanced is the time for preparation. In particular, 3-5GHz band, focused on mobile communications can be used to secure the necessary frequency band relocated and the existing crosstalk analysis methodology developed for the services rendered, and the frequency of such results to obtain new spectrum for IMT-Advanced for the country to secure the frequency characteristics and IMT-Advanced 3-5GHz band for the radio frequency of the characterization techniques necessary to develop a national wireless communication interference and frequency-based technology acquisition and management skills were identified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.9
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• pp.606-613
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• 2014

The Internet of Things (IoT), which has recently attracted attention as next-generation IT industry, is based on a wired and wireless network platform that can connect various Things. However, it is challenging to implement the IoT platform because of the heterogeneity of the network. Particularly, the ZigBee transmission may be significantly harmed due to Wi-Fi with the relatively much higher power, and this is one of the reason making the platform implementation difficult. In this paper, the ZigBee transmission is measured and analyzed by the BEB algorithm for finding the slot time when ZigBee can transmit, and an actual transmission happens stochastically depending on the network environment. The simulation results show that it guarantees high success rate of the ZigBee transmission by overcoming Wi-Fi interference in the 2.4 GHz frequency band.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.540-550
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• 2016

Since energy efficiency has become a significant concern for network infrastructure, next-generation network devices are expected to have embedded advanced power management capabilities. However, how to effectively exploit the green capabilities is still a big challenge, especially given the high heterogeneity of devices and their internal architectures. In this paper, we introduce a hierarchical power management architecture (HPMA) which represents physical components whose power can be monitored and controlled at various levels of a device as entities. We use energy aware state (EAS) as the power management setting mode of each device entity. The power policy controller is capable of getting information on how many EASes of the entity are manageable inside a device, and setting a certain EAS configuration for the entity. We propose the optimal local control policy which aims to minimize the router power consumption while meeting the performance constraints. A first-order Markov chain is used to model the statistical features of the network traffic load. The dynamic EAS configuration problem is formulated as a Markov decision process and solved using a dynamic programming algorithm. In addition, we demonstrate a reference implementation of the HPMA and EAS concept in a NetFPGA frequency scaled router which has the ability of toggling among five operating frequency options and/or turning off unused Ethernet ports.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1065-1072
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• 2006

An OFDM(Orthogonal Frequency Division Multiplexing) system has the problem of the PAPR(Peak-to-Average Power Ratio) due to the overlapping phenomena of many sub-carriers. The previously proposed GA-SPW(Genetic Sub-block Phase Weighting) method not only improved the reduction of PAPR as the number of sub-blocks increases in an OFDM symbol but also decreased the number of calculations involved in the iterative phase searching yields to depend on the number of population and generation by using genetic algorithm not on the number of sub-blocks and phase elements. In this paper, we propose the modified GA-SPW method in order to improve the performance and to decrease the complexity. It is shown that the proposed modified GA-SPW method achieves the significant performance and the reduction of search complexity comparing to the ordinary technique, iterative flipping and previously proposed GA-SPW by the experimental results and analysis.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.81-89
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• 2012

Commonly used horizontal-axis wind turbines (HAWT) have the following structure: two or three blades, a nacelle which contains power converting equipments, generators, and a tower which supports the nacelle. The generated power is transmitted from the nacelle to the ground. Due to this structure, the power transmission lines are twisted when the nacelle is yawing. Thus, slip ring or additional yaw control mechanism is required. We propose a new structure of HAWT which is free of this transmission line problem. Moreover, the size of inverter can be reduced since two generators are connected in parallel in our mechanism so that power is distributed. A controller for yawing is developed so that it works in harmony with the controller for power generation. A MPPT (Maximum Power Point tracking) algorithm is implemented for the proposed system and efficiency of the system is validated by simulation.