• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.19-25
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• 1998

Remote fault diagnosis and maintenance system using general telecommunication network is necessary for an effective fault diagnosis and higher productivity of NC machine tools. In order to monitor machine tool condition and diagnose alarm states due to electrical and mechanical faults, a remote data communication system for monitoring of NC machine fault diagnosis and status is developed. The developed system consists of (1) remote communication module among NC's and host PC using PSTN. (2) 8 channels analog data sensing module, (3) digital I/O module for control or NC machine, (4) communication module between NC machine and remote data communication system via RS-232C, and (5) software man-machine interface. Diagnostic monitoring results generated through a successive type inference engine are displayed in user-friendly graphics. The validity and reliability of the developed system is verified to be a powerful commercial version on a vertical machining center through a series of experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1754-1760
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• 2010

The HVDC system consists of ac side and dc side through thyristor valve. ac side protection is similar to conventional ac system protection schemes but dc side protection is different from ac side of HVDC system. AC system don't have controller but HVDC system has controller that controls and protects system from faults and disturbance. This paper show protectional function of HVDC dc side such as asymmetry protection, ac/dc differential protection, dc overvoltage, dc overcurrent protection. Protection models is developed using RTDS software and assessment of protection models is also performed by RTDS system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.107-108
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• 2008

This paper surveys areas of vulnerability to voltage sags in KEPCO system. The area of vulnerability can be defined as the region where the occurrence of faults will lead to voltages lower than the sensitivity threshold of equipment. The analysis of the area of vulnerability is essential for estimating system voltage sag performance and establishing efficient countermeasures for voltage sag problems. In this paper, two buses in KEPCO system were randomly selected and the areas of vulnerability for the buses were calculated by using dedicated software.

• Journal of Korea Multimedia Society
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• v.20 no.11
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• pp.1793-1802
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• 2017

In the recent years, IT and Network Technology has rapidly advanced environment in accordance with the needs of the times, the usage of the smart learning service is increasing. Smart learning is extended from e-learning which is limited concept of space and place. This system can be easily exposed to the various security threats due to characteristic of wireless service system. Therefore, this paper proposes the improvement methods of smart learning system security by use of faults analysis methods such as the FTA(Fault Tree Analysis) and FMECA(Failure Mode Effects and Criticality Analysis) utilizing the consolidated analysis method which maximized advantage and minimized disadvantage of each technique.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.3
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• pp.54-59
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• 2007

It is widely recognized that increasing the accuracy and diversity of rotating machinery necessitates an appropriate diagnostic technique and maintenance system. Until now, operators have monitored machinery using their senses or by analyzing simple changes to root mean square output values. We developed an expert diagnostic system that uses fuzzy inference to expertly assess the condition of a machine and allow operators to make accurate judgments. This paper describes the hardware and software of the expert diagnostic system. An assessment of the diagnostic performance for five fault phenomena typically found in pumps is also described.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.118-120
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• 2001

This paper presents a distance relaying algorithm based on the Discrete Fourier Transform(DFT) for elimination of DC-Offset. When the DFT is applied to current signal. the real and imaginary parts of fundamental component consist of fundamental component itself and DC-Offset. The DC-Offset is calculated by four consecutive values of the imaginary components, so that the fundamental component can be accurately estimated. Performance evaluation is presented for A-phase ground faults on 154kV 80km overhead transmission line. The proposed algorithm is inspected by software simulation and hardware simulation.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.238-247
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• 1999

A study on the static type simulator will include an instructor's station, two cabs for ISA with visual and sound system, and realistic and accurate model of the trains operation. The simulator is easy to extend and maintenance using structured the S/W. The training of new drives requires that the environment of the cab, controls placement, etc. must highly realistic so that driver can readily transfer his training experience to the real world. The simulator detailed software model and extensive scenario design capability allows both for a wide variety of scenarios and accurately modeled response covering most aspects of brakes, rules, and faults.

• Journal of the Korean Home Economics Association
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• v.30 no.1
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• pp.49-65
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• 1992

The writer did a survey of current textile patterns for the purpose of identifying a motif trend. After identifying a current motif trend the writer used an IBM PC 386 Computer and Lumena Software to design actual patterns. The results are as follows: 1. The most common currently used prints are floral patterns. 2. Knowing that floral patterns are most popular, the writer established a motif using the Rose of Sharon, the national flower of Korea. 3. Using computer graphics to move, enlarge and scale-down motif, the writer has been able to design various textile patterns. 4. Creating patterns with computer graphics was not only more efficient, but it also produced more accurate designs and a greater variety of designs. 5. Using the many computer graphic functions avaliable, a greater variety of patterns changes and compositions can be displayed than would be possible if produce by hand. 6. Computer simulations of textiles and clothing made it possible to evaluate the printed fabric or finished product. Faults in the printed fabric or clothing could be corrented before production. Through simulation then it is possible to create higher quality garments and readuce costly mistakes. Thereby greater profits will be realized from the finished garments.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.471-473
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• 1999

Recently, the computer based control systems instead of conventional relays circuitry are widely used to industrial applications, and also those technology is available to railway signaling which are safety-critical systems. However, the safety and reliability of software for those systems are harder to demonstrate than in traditional relays circuitry because the faults or errors can not be analyzed and predicted to those systems. So, the safety problems are crucial more and more in computer based control system. In this paper, the GRAFCET(GRAphe Fonctionnel do Commande Etape/Transition) language is used as a analysis and verification tool for safety-critical interlocking logic. The general description for Grafcet notation are provided and the general modeling for interlocking logic is presented.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.103-105
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• 1996

This paper describes real time dynamic tests on the digital distance relay using new digital test system including RTDS(Real Time Digital Simulator) in KEPRI. The RTDS is developed by the Manitoba HVDC Research Centre and consists of specialized hardware and software which allows transients simulation of electrical power systems in real time. From high impedance fault test, it is known that the characteristics of distance reach is influenced by load flow. A detailed discussion of relay test using the RTDS simulator, high impedance faults and test results are included in the paper.