• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.6
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• pp.905-909
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• 2012

Recent WTO/TBT agreement was adopted by the IEC domestic. For this reason, low voltage electrical equipment was many Confusion arises. Low voltage circuit was also one of these. The case of low voltage circuit, existing domestic circuit breakers and circuit breakers IEC curve differs from the behavior of each other. If low voltage circuit breaker wrong facility, circuit breaker malfunction may occur due to the large property damage. In this paper, to solve these problems domestic circuit breakers and circuit breaker operation IEC curves were analyzed. And, through experiments suggested compatible breaker way.

• Journal of the Korean School Mathematics Society
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• v.3 no.2
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• pp.133-154
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• 2000

The purpose of this study is to analyze theoretically suggested performance test and find out the actual conditions is math class at high schools and to suggest some devices for improvement for the various problems. To achieve this goal of study, I applied a performance test to the first graders of high school for one semester, and analyzed various phenomena which appeared during its practice. I made several questionnaire based on the materials of an academic seminar, "Several questions and devices for the improvement on mathematics performance test" And through the analysis, I pointed several problems of the performance test and proposed alternative plans. Several practical alternatives can be suggested for the problems appeared in the operation of performance test. The most important thing than any other technical solution in teachers′ diverse endeavor and enthusiastic research attitude to overcome the difficulties. Teachers′ spontaneousness is the foundation to enhance their own specialty and eradicate the propriety of the performance test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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• pp.890-896
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• 2008

Sheet metal forming is one of the most useful and important method in manufacturing of the autobody panels because of the excellent production rate. The objectives of sheet metal forming processes are getting a desired geometrical shape of products with good quality, low cost and reasonable lead time. In this paper, we examined the validity of finite element method analysis on the automobile FRT-PLR-L/R stamping process by using the lancing engineering method. Lancing is a press operation in which a single-line cut or slit is made on part way across the strip stock, without removing any metal. As a result, it has shown that the proper lancing engineering method could prevent fracturing by improving sheet metal flow.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2058-2060
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• 2002

The demand for safety and reliability of Nuclear Power Plants (NPPs) has been constantly increasing and economical operation is also an important issue. Developing and adopting predictive maintenance technology for the major systems or equipment is considered as one way to achieve these goals. This paper suggests the predictive maintenance methodology that can be applied to NPPs and describes a sample application of the Rod Control System (RCS) to verify the effectiveness of the methodology. It is expected that the same methodology can be adopted for other systems of NPPs and general industry fields when its effectiveness is verified.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.442-446
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• 2009

As the railway transportation is getting faster and its operation speed has increased rapidly, its signal control has been complicated. For real time signal processing it is very important to prohibit any critical error from causing the system to malfunction. Today, most of the railroad's controling communications between wayside and train are made in one way. Therefore, by using a forward error correction technique, which receiver can actively correct the signal error, we can increase the performance and the stability of the railroad signaling system. In this paper, we introduce low density parity check(LDPC) that is used by next generation wireless communications and DMB technique. We verified that we can achieve low bit error rate(BER) in high signal to noise ratio(SNR) by using LDPC.

• IE interfaces
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• v.12 no.1
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• pp.26-31
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• 1999

Evolutionary Operation(EVOP) is a method for continuously monitoring and improving a full-scale process to get an optimal operating condition while production is under way. To avoid appreciable changes in the product quality characteristics only small changes are made in the levels of the process variables. One of the reasons why EVOP is not so popular is that people in charge of the EVOP is blamed when the EVOP does not produce good results. We present an EVOP procedure when prior information of the relationship between defect types and process variables is known. The procedure is illustrated with an injection molding case study.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2429-2433
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• 2008

A rotary vane blower was developed as an air supply system for fuel cell application. As one way of improving the blower efficiency, a roller was adapted between vanes and cylinder housing. The performance of blower was investigated experimentally. The blower power input was about 115W to compress the air at normal atmospheric condition to 0.2 bar with the flow rate of 140 NLPM, resulting in the blower overall efficiency of 43%. After 400 hours of operation, the performance of blower was not changed. The result showed that developed blower was confirmed to be suitable for fuel cell application.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1186-1192
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• 2012

In Jeju Smart Grid field test, Zigbee technology is being used as one of customer side solutions for AMI. Although Zigbee networks that provides effective connectivity and control among devices are advantages in ease of implementation and use, the data can be exposed to cyber attacks such as eavesdrop, unauthorized data dissemination and forgery. Currently authentication and confidentiality services are provided with the network and link keys generated based on public key pairs that are pre-installed in offline. However, the network is vulnerable once a hacker intrudes into a local network because operation and management policies for the generated keys are not well-established yet. In this paper, the vulnerability of the Zigbee security system in the customer side environment of Jeju Smart Grid field test is analyzed. Then, two-way authentication with the unique identifiers of devices and user-specific group management policies are proposed to resolve the vulnerability.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.22-32
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• 2008

This paper proposes a linearization technique for the 3-level NPC type inverter, which increases the linear control range of Inverter up to the one-pulse inverter. The overmodulation range is divided into two modes depending on the Modulation Index, MI. In overmodulation region I, the reference angles are derived from the fourier series expansion of the reference voltage corresponding to the MI. In overmodulation region II, the holding angles are also derived in the same way. Therefore, it is possible to obtain the linear control and the maximized utilization of PWM inverter output voltage.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.5
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• pp.511-520
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• 2015

Inventory, cost, and the level of service are three interrelated key metrics that most supply chain organizations are striving to optimize. One way to achieve this goal is to create a simulation model to conduct sensitivity analysis and optimization on several different supply chain policies that can be implemented in actual operation. In this paper, a case of Xerox global supply chain modeling and analysis to assess several "what if" scenarios for the consumable policy safety stock is presented. The simulation model, combined with analytical cost model and optimization module, is used to optimize the policy safety stock level to achieve the lowest total value chain cost. It was shown quantitatively that the policy safety stock can be reduced, but it is offset by the inbound premium transportation cost to expedite supplies in shortage, and the outbound premium transportation cost to send supplies to customers via express shipment, requiring fine balance.