• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.340-343
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• 2001

In an electrical network, electrical power are transmitted by a various of protection, isolation and control electric circuit devices. This thesis deals with the protection function between circuit-breakers. The protective coordination concerns the behaviour of two devices placed in series in an electrical network, with a short-circuit downstream circuit-breaker. It has two basic principles: First, discrimination which is an increasing requirement of low voltage electrical distribution systems. Second, which is less well known: cascading, which consists of installing a device, whose breaking capacity is less than the three-phase short-circuit current at its terminals and helped by main circuit-breaker. The important advantage of cascading is to be able to install at a branch circuit-breaker of a lesser performance without endangering the safety of the installation for more economical usage. To determine and guarantee co-ordination between two circuit breakers, it is necessary to carry out a theoretical approach, first, and then confirm the results by means of standard tests. This is illustrated in appendix A of IEC 947-2.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.254-259
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• 2005

In this study, measurement of thermal conductivity of multilayer thin dielectric film has been conducted via differential 3$\omega$ method. Also, verification of differential 3$\omega$ method has been accomplished with various proposed criteria. The target film for measurement is 300 nm silicon dioxide and this thin film is covered with various thicknesses of upper protective layer. The upper protective layer is inserted between the target film and the heater line for purpose of electrical insulator or anti-oxidation barrier since the target film may be a good electrical conductor or a well-oxidizing material. However, the verification of differential 3$\omega$ method has not been conducted. Thus we have shown that the measurement of thermal conductivity of thin films with upper protective layer via differential 3$\omega$ method is verified to be reliable as long as the proposed preconditions are satisfied. Experimental results show that the experimental errors tend to increase with aspect ratio between upper protective layer thickness and width of the heater line due to heat spreading effect.

• 전산구조공학
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• 제25권3호
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• pp.7-12
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• 2012

• 조명전기설비학회논문지
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• 제27권5호
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• pp.95-103
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• 2013

Protection of the electrical and electronic equipment against surges in low voltage AC power distribution systems is based on wide applications of surge protective devices(SPDs). Cascade application of SPDs located at the service entrance of a building and near sensitive equipment is intended to ensure the optimal voltage protection level and energy sharing among cascade SPDs. In this paper, when surges impinge at the service entrance of the building of interest, the protection characteristics of two-stage cascade SPD systems were investigated. The influence of the distance between the upstream and downstream SPDs on the voltage protection level and energy sharing of the two-stage cascade SPD systems were analyzed experimentally. It was found that the energy sharing of two-stage cascade SPD systems strongly depends on the distance between the two SPDs and the component of SPD. As the distance between the two SPDs increases, the energy absorbed by the upstream SPD increases while the energy absorbed by the downstream SPD decreases. Consequently, it is desirable to select the upstream and downstream SPDs having the proper energy capability with due consideration of the distance between the two SPDs.

• Elastomers and Composites
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• 제34권2호
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• pp.177-182
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• 1999

SBS thermoplastic elastomers offer an inexpensive alternative to vulcanised rubbers for many undemanding applications. They are, however, particularly susceptible to attack from atmospheric ozone leading to cracking as soon as any strain is applied. In most rubber applications some strain is unavoidable. In this paper a compounding approach to protecting SBS thermoplastic rubbers against ozone is described. An explanation is offered for why a protective effect Is observed only when certain combinations of additive are used. SBS elastomers are the most affordable class of thermoplastic rubbers. To achieve finished products resistant to ozone and without compromising the light colours often demanded, recourse must be made to blending with other saturated elastomers or replacement by hydrogenated (SEBS) types. The latter is a significantly more expensive alternative. Under laboratory conditions where the rate of ozone attack is increased by several decades, unprotected SBS begins to crack within a few hours. Several different protective agents are examined here, the best of which, a cyclic enol ether, $Vulkazon^{(R)}$ AFD, can extend the resistance to any cracking to several weeks by the use of a few percent by weight of additive. The systems reported neither discolour the polymer nor stain other materials with which it may be in contact. Use of the protective systems described here could enable SBS elastomers to compete in many applications with the more expensive SEBS polymers.

• 한국조명전기설비학회지:조명전기설비
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• 제11권4호
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• pp.109-116
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• 1997

I본 논문은 교류 전원용 바리스터와 LC필터를 조합한 서지 보호장치에 대해서 기술하였다. 지금까지 교류 전류용 서지 보호장치로써 바리스터만이 주로 사용되어 왔으나, 이것은 급상승하고 높은 잔류전압 때문에 보호되어야 할 장비에 해로운 결과를 초래하는 경우도 있다. 따라서 본 연구에서는 교류 전원용 서지 보호장치의 차단 성능을 향상시키기 위하여 바리스터와 LC필터로 구성된 조합형 서지 보호장치를 설계.제작하였다. 그리고 서지 보호장치의 동작특성과 차단 성능의 분석에 대한 실험을 1.2/50[$\mu\textrm{s}$] 임펄스 발생기를 적용하여 수행하였다. 결론적으로 본 연구에서 제시한 조합형 서지보호장치는 서지 전압을 더욱 낮게 제한할 수 있고, dV/dt의 값을 매우 낮은 값으로 감소시키며, LC필터에 의한 출력단의 고주파 전압을 효과적으로 감쇠시킬수 있기 때문에 전자시스템의 손상과 전도를 더욱 더 효과적으로 방지할 수 있다.

• 동의생리병리학회지
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• 제18권2호
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• pp.586-595
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• 2004

Kamidojuk-San (KDJS) is known to be effective for treating cardiovascular diseases such hypertension, and clinically applied for the treatment of cerebral palsy or stoke patients. Yet, the overall mechanisms underlying its activity at the cellular levels are not known. Using experimental animal system, we investigated whether KDJS has protective effects on cells in cardiovascular and nervous systems. KDJS was found to rescue death of cultured primary neurons induced by AMPA, NMDA and kainate as well as BSO and Fe/sup 2+/ treatments. Moreover, KDJS treatment promoted animal's recovery from coma induced by a lethal dose of KCN treatment, and improved survival in animals exposed to lethal dose of KCN. Neurological examinations further showed that KDJS reduced the time which is required for animals to respond in terms of forelimb and hindlimb movements. To examine its physiological effects on cardiovascular and nervous systems, we induced ischemic injury in hippocampal neurons and cerebral neurons by middle cerebral artery (MCA) occlusion. Histological examination revealed that KDJS significantly protected neurons from ischemic damage. Thus, the present data suggest that KDJS may play an important role in protecting cells of cardiovascular and nervous systems from external noxious stimulations.

• Journal of Electrical Engineering and information Science
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• 제3권1호
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• pp.51-57
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• 1998

As DAS becomes a common practice, various operational tools are needed. This paper proposes the new restoration strategy considering the coordination of the protective devices and the generalized method for determining the switching sequence. The effectiveness of the proposed method has been tested on the various real systems.

• Tribology and Lubricants
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• 제7권1호
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• pp.16-27
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• 1991

The mechanism of failure of lubricated surfaces at high sliding speeds was investigated. Experiments were performed with the ball-on-flat and cylinder-on-flat geometries, using lubricants of four different chemical reactivities. Surface failure was found to not be predictable using the ratio, $\lambda$, of fluid film thickness to composite surface roughness except when chemically inert lubricants are used. Even then the influence of temperature rise on fluid film thickness does not adequately explain the low load carrying capacity of lubricants at high sliding speeds, which causes surface failure. The protective layers on sliding surfaces that form by chemical reaction with the lubricant were found to reduce the surface roughening and increase the load carrying capacity of surfaces to values of $\lambda$ as low as 0.03. Neither the surface roughening nor the formation of the protective layers have been incorporated into failure models for lubricated systems.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.167-173
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• 2011

This paper presents a method for the development of the impedance locus to test the dynamic characteristics of protective relays. Specifically, using the proposed method, the impedance locus can comprise three impedance points, and the speed of impedance trajectory can be adjusted by frequency deviation. This paper is divided into two main sections. The first section deals with the configuration of impedance locus with voltage magnitude, total impedance magnitude, and impedance angle. The second section discusses the control of the locus speed with the means of the deviation between two frequencies. The proposed method is applied to two machine equivalent systems with offline simulation (i.e., PSCAD) and real-time simulation (i.e., real-time simulation environment) to demonstrate its effectiveness.