• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.948-952
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• 2009

Recently, a new distributed grid scheme, called DS-GRID(distributed S-GRID), has been proposed to manage the location information of moving objects in a spatial network[1]. However, because DS-GRID uses uniform grid cells, it cannot handle skewed data which frequently occur in the real application. To solve this problem, we propose a dynamic distributed grid scheme which splits a grid cell dynamically based on the density of moving objects. In addition, we propose a k-nearest neighbor processing algorithm for the proposed scheme. Finally, it is shown from the performance analysis that our scheme achieves better retrieval and update performance than the DS-GRID when the moving objects are skewed.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1527-1534
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• 2016

Online voltage stability monitoring using real-time measurements is one of the most important tasks in a smart grid system to maintain the grid stability. Loading margin is a good indicator for assessing the voltage stability level. This paper presents an Extreme Learning Machine (ELM) approach for estimation of voltage stability level under credible contingencies using real-time measurements from Phasor Measurement Units (PMUs). PMUs enable a much higher data sampling rate and provide synchronized measurements of real-time phasors of voltages and currents. Depth First (DF) algorithm is used for optimally placing the PMUs. To make the ELM approach applicable for a large scale power system problem, Mutual information (MI)-based feature selection is proposed to achieve the dimensionality reduction. MI-based feature selection reduces the number of network input features which reduces the network training time and improves the generalization capability. Voltage magnitudes and phase angles received from PMUs are fed as inputs to the ELM model. IEEE 30-bus test system is considered for demonstrating the effectiveness of the proposed methodology for estimating the voltage stability level under various loading conditions considering single line contingencies. Simulation results validate the suitability of the technique for fast and accurate online voltage stability assessment using PMU data.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.30-41
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• 2011

In order to obtain more clear x-ray images, an antiscatter grid, which can absorb the scattered rays, is employed. In the high-resolution direct digital radiography, however, the artifacts due to the grid are visible. In this paper, within the methods of obtaining x-ray digital images by employing the rotated grids for the facility of grid artifact reduction, the previous work, where the frequencies of the artifact components on the boundary, is further analyzed and extended, and a min-max optimization for a given grid density is proposed. For practical grid densities, appropriate grid angles are provided and a grid artifact reduction algorithm is proposed for the appropriate grid angles. The proposed algorithm is tested for real x-ray digital images with a comparison, and can remove the grid artifacts while maintaining the resolution of the original image.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.46-53
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• 2007

Micro-grid consists of micro-sources which adopt environmentally friendly and reliable power sources such as Fuel-Cell and Micro-Turbines with independent real and reactive power control capability for providing premium power quality. This paper deals with the basic aspect of dynamic modeling and the stability analysis of the micro-grid system. The fundamental frequency model of the micro-source inverters are considered to form a dynamic model of the micro-grid system Stability analysis is performed based on the linearized dynamic model of the micro-grid system Case study results show the parameters affecting the stability of the micro-grid.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.1-6
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• 2008

Data grid shares distributed large data via wide-band network. Such grid environment consumes much time for large data transmission. Because it is implemented on internet as physical network. Many replication strategies were proposed for solving this problem, but they are not optimal in real Data grid environments. Because they were proposed that based on logical topology without consideration of real internet architecture. Grid data access time is largely influenced by internet architecture as physical network of Data grid. In this paper, we propose a new data replication strategy RSIA(Replication Strategy based on Internet Architecture) based on internet architecture. The RSIA places replicas considering structural hierarchy in each element of internet, and avoid the performance bottlenecks to reduce system performance degradation when a data transfer. Through simulation, we show that the proposed RSIA data replication strategy improves the performance of Data Grid environment compared with previous strategies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.107-118
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• 2002

The purpose of this study is to investigate the strengthening effect of RC beams with carbon fiber grid. Carbon fiber grid that is very lightweight and stronger than steel reinforcement does not rust or corrode and has a very high resistance to salt. In this study, five real size specimens which are strengthened with different types of carbon fiber grid are tested. With the results of this tests, we found the physical and mechanical properties of carbon fiber grid and polymer mortar which are used to strengthen the damaged or cracked reinforcement concrete beams. we also investigate the strengthening effect of carbon fiber grid on the five flexural test specimens that have cracks.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.169-174
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• 2001

A novel simulation scheme of transient phenomenon for the photovoltaic (PV) generation system under the real weather conditions has been proposed in this paper. A grid connected PV array is simulated using PSCAD/EMTDC. The transient changes of the output current of PV array under the real weather conditions is described and the output current of DC/AC converter flowing through the utility power network is also analyzed with the PWM switching width. Moreover, the MPPT control of PV generation system is combined to the system during the simulation for the comparison purposes of the control schemes. The outcome of the simulation demonstrates the effectiveness of the proposed simulation scheme. The result shows that the cost effective verifying for the efficiency or availability and stability of PV generation systems and the comparison research of various control schemes like MPPT under the same real whether conditions are eventually possible.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.6
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• pp.804-809
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• 2012

This paper presents the economic impact of consumer participation in Real-Time Pricing (RTP). A computer model was developed to analyze the impact of real-time pricing on the average price, electricity sales, and the social welfare. Four revenue reconciliation alternative were introduced to illustrate the effect of RTP. Finally a case study was done to analyze the consequent impact of the dynamic load profile on the long-term fuel mix, and the results were compared with those of $5^{th}$ national power development plan.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1305-1313
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• 2011

Web based online real-time reliability integrated information system is asked rapidly for more efficiency and demand response in recent. As the utilization of renewable resources has been receiving considerable attention in recent years, the information system requirement is increased. Specially, the reliability information system is more important for implementing the smart grid. This paper describes architecture of the WORRIS(Web based Online Real-time Reliability Integrated Information System) Version 7.0 system that simulates the reliability indices in composite power system considering wind turbine generators(WTG) developed successfully in this paper. And we had simulated the case study using Jeju island power system data.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.388-397
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• 2012

Recently, one of the received attraction fields in web based service is 'Human Relationship Service' that is called SNS. This relationship map service is able to deliver information to user more easily and visually because it is intuitive data that is linked with offline real world. While past map service put physical real information in the map, present map service is evolving into new communicative platform that expresses social relationship beyond simple search platform that shows real world. In this paper, we propose smart social grid system using sketch map that is based on online map service structure. This system has features such as standardized interface provision for various SNS, use to governance hub tool in case of establishing a personal network through expanded social grid, a role of bridge to mashup software linked with other SNS, user environment construction that reproduces social grid data, and the faster service setup by improved search technology.