• Journal of the Korean Society for information Management
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• v.25 no.3
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• pp.99-118
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• 2008

As time gees by, the function and role of website become more important. Therefore, it is very critical to evaluate and improve continuously the website to the purpose. Many previous studies show that some website evaluation factors will influence the user satisfaction and revisit to the website. The website evaluation criteria from the previous studies related to the university library website evaluation were classified into five assessment criteria which are design, contents, user interface, reliability, and site management. In the results, some significant suggestions were found out. User satisfaction is seriously affected by user interface, and user's intention to revisit is influenced by contents and reliability, but there may not be a close connection between them. Besides, the evaluation method in this study may be applicable to the new website-improving approach of website administrators and researchers.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.77-86
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• 2011

The advanced geotechnical information has been required to determine the accurate design parameters for complex construction. However, the Standard Penetration Test (SPT), which has low reliability, has been used to estimate the subsurface condition in the field. The objective of this paper is development and application of the Static-Dynamic penetrometer, which detects the resistances in soft clay, sand and rock. The energy losses according to the rod connection methods (perfect or non-perfect connection, and number rods) are experimentally evaluated. The reflection and transmission ratios are used to investigate the energy loss by a simulation. The static-dynamic cone penetrometer, in which the accelerometers and strain gauges are installed on the cone tip and the rod head, is used to estimate the energy loss during penetration by impacts. The experimental and simulation studies show that the transferred energy through rods with non-perfect connection dramatically decreases. Furthermore, the transferred energy on the rod head is not the same as that on the cone tip. This study demonstrates that the energy loss should be evaluated on the cone tip.

• Computers and Concrete
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• v.14 no.6
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• pp.711-725
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• 2014

The purpose of this study is to evaluate the behavior and the strength of SRG (Steel Reinforced Grout) externally strengthened Reinforced Concrete (RC) beams by using a nonlinear numerical analysis. The numerical simulation was carried out by using a three-dimensional (3D) finite element model. An interface element with a suitable damage model was used to model the connection between concrete surface and SRG reinforcing layer. The reliability of the finite element 3D-model was checked using experimental data obtained on a set of three RC beams. The parameters taken into consideration were the external configuration, with or without U-end anchorages, the concrete strength, the amount of internal tensile steel reinforcement. Conclusions were made concerning the strength and the ductility of the strengthened beams by varying the parameters and on the effectiveness of the SRG reinforcing system applied with two types of external strengthening configuration.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.355-357
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• 2006

A study of the photovoltaic generation system tend to concentrate its importance on specific filed such as analysis of photovoltaic characteristic, improvement of a inverter, and controller. In this paper, a practical facility of the photovoltaic generation system and connection of its organization are presnted with process of 1.2kW prototype. From the results of monitoring system which is for reliability and analysis of the photovoltaic generation system, stability of the system was confirmed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.171-180
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• 1994

Full scale structural test of 765kv electric transmission tower was performed to measure the stresses and displacement of towers under the design loadings, and the results were compared with analytical results based on three dimensional frame analysis. Also, the actual ultimate strength of the tower was measured through destructive test. Especially, to predict the behavior and failure of the connection of tubular member, finite element analysis was performed and compression test for the segments of tubular member were carried out. Valuable information for the overall and local behavior of the tower was obtained and reliability of current analytical method was confirmed.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1212-1213
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• 2011

PWM(pulse width modulation) rectifier has unit power factor and low harmonic distortion with high power conversion efficiency in entire loading range. These merits of PWM rectifier help the spread of DC distribution system. In addition, if multiple PWM rectifiers can be operated in parallel connection, maintenance process can be simple and reliability of power source can be advanced because of the hot swapping is available. The other way, the load unbalance among rectifiers can force a converter to stop by over current. The surge current by closed circuit composition between rectifiers can force switching devices damage. In this paper, some problems that can occur in case of parallel operation of PWM rectifiers and problem eliminating methods are considered.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2089-2098
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• 2017

Microgrid is a convenient, reliable, and eco-friendly approach for the integration of Distributed Generation (DG) sources into the utility power systems. To date, AC microgrids have been the most common architecture, but DC microgrids are gaining an increasing interest owing to the provision of numerous benefits in comparison with AC ones. These benefits encompass higher reliability, power quality and transmission capacity, non-complex control as well as direct connection to some DG sources, loads and Energy Storage Systems (ESSs). In this paper, main challenges and available approaches for the protection of AC and DC microgrids are discussed. After description, analysis and classification of the existing schemes, some research directions including coordination between AC and DC protective devices as well as development of combined control and protection schemes for the realization of future hybrid AC/DC microgrids are pointed out.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.237-239
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• 2009

This paper presents a new developed 160kV-120kW Class MPC (magnetic pulse compressor) power supply for DeNOx, DeSOx system. The circuit consists of N-series connected CCPS (capacitor charging power supply) and MPC Tank. The MPC power supply developed compared to the conventional LC resonant type has many advantage, it was verified reliability of a product by module, simulator and tank connection test. Now, the developed MPC power supply is installed POSCO sintering plant for DeSOx, DeNOx system.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.280-282
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• 2005

Micro-source units having power ratings in thousands of watts can provide even higher reliability and fuel efficiency than the conventional large scale units. These units are also clustered with loads creating micro-grid services to customer sites such as office buildings, industrial parks and homes. Micro-sources adopt voltage source inverter to ensure the power quality of sensitive loads. This paper deals with the connection of micro-sources into the system grid. Modeling and simulation of the grid connected micro-sources at the power frequency range are investigated. Simulation results show that the micro-grid system with two micro-sources has good dynamic characteristics.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.199-204
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• 2006

To develop a safety-critical network in nuclear power plants that puts more stringent requirements than the competitive commercial ones do, we establish four design criteria - deterministic communication, explicit separation/isolation structure, reliability, verification & validation. According to those design criteria, the fundamental design elements are chosen as follows - a star topology, point-to-point physical link, connection-oriented link control and fixed allocation access control. After analyzing the design elements, we also build a communication architecture with TDM (Time Division Multiplexing) bus switching scheme. Finally, We develop a DDCNet (Deterministic Data Communication Network) based on the established architecture. The DDCNet is composed of 64 nodes and guarantees the transmission bandwidth of 10Mbps and the delay of 10 msec for each node. It turns out that the DDCNet satisfies the aforementioned design criteria and can be adequately utilized for our purpose.