• Proceedings of the KIEE Conference
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• summer
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• pp.224-226
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• 2004

Flexible AC Transmission System (FACTS) can greatly reinforce power systems through improvement of power transmission capacity and utilization of equipment under the circumstance of continuous load growth and deregulation SVC and STATCOM are shunt FACT devices that have similar static characteristics with Mwhuical Swikhed Capacitor (MSC). The main issue of this paper is the analysis of different dynamic characteristics when STATCOM is solely adopted and when STATCOM is adopted with combination of other reactive power compensator such as SVC and M5C. Furthermore, better application of reactive power compensators can be clarified through analysis of dynamic characteristics of various combinations of reactive power compensators.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.319-321
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• 2001

When the fault occurred at distribution system, the restoration was late. There are 2 reasons The one is the error of fault location the other is multiple possible candidates of fault location. This paper presents two of new techniques for diagnosing fault regions. The proposed diagnosis scheme is capable of accurately identifying the location of fault upon its occurrence. based on the integration of information available from protective devices and measured load current change at the substation. In this paper expert system for real fault region is presented using these facts. Testing of the developed system using EMTP Simulation Model has demonstrated.

• Korean Journal of Organic Agriculture
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• v.4 no.1
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• pp.59-73
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• 1995

Some devices of sustaining the small scale farming in the changing social and economic conditions in which comparative disadvantages are evidently to be experienced in the near future, are becoming a central proposition in the Korean agriculture. In this connection, development of integrated activities in farming among individual farmers within a region may be an important device of overcoming prevailing limits of resource possession and use of individual farmers. These inter-farm or inter-group cooperation and integration can be promoted through establishing efficient cooperative system within a farming district. This study was undertaken to find facts pertaining to situations leading to successful performence of cooperative systems in group farming. In this study, The case in Cheunee Myun, Yungi-Gun, Chungchungnam-Do in which farming is specialized in production of so called "organic farming products" and farmers are integrated for increasing their productivity.ductivity.

• Journal of Educational Research in Mathematics
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• v.9 no.1
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• pp.295-309
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• 1999

The primary purpose of this study is to investigate problems with the current mathematics textbook. According to a survey, the following were the findings: Textbook is only a tool-book for introducing mathematical facts. It is a unique book for all students possessing different level of mathematical ability. There is difficulty in teaming math using technological devices and in activating(mental and concrete) manipulative activities. There is difficulty in communicating while doing mathematics. There is lack of defined and developed layout of textbook, et. al. It can be however found that these problems can be solved to some degrees, when mathematics textbook is developed based on constructivism. Recently, in mathematics education, it has been gradually emphasized that constructivism can be powerful in teaching and learning mathematics. There are however some difficulties in developing mathematics textbooks to reflect constructivism, such as to fill the gap between the contents written in the national curriculum determined in advance and the contents which students construct psychologically or socially in mathematics class.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.305-307
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• 2003

This paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS (Flexible AC Transmission System) devices, particularly the UPFC (Unified Power Flow Controller), between Kangjin and Jangheung in Korea. With the changes of UPFC's parameters, the measurement and protective range (trip boundaries) of the adaptive distance relay can also be changed. So, it is the most important part in the field of system protection to analyze the operating characteristic of relaying system. The presence of UPFC significantly affects the trip boundaries which are also adversely affected by fault resistance combined with remote end infeed. This paper presents the apparent impedance calculations and the distance relay setting characteristics for faults involving the UPFC in the KEPCO system.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.468-470
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• 1995

In this paper, a series compensator with a resonant LC circuit and a shunt compensator with the resonant circuit are compared based on the respective rating of its circuit elements. The rating are calculated over a range of compensation and over a range of bus angle. The components ratings are expressed in a per unit values. The results of this study can be easily converted to actual MVA by a simple change in scale. The methodology presented to rate the various components within the system will help to determine the feasibility of various FACTS devices in costs.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.3
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• pp.102-108
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• 2006

This paper proposes a 36-pulse back-to-back voltage source converter using four sets of 12-pulse bridges with pulse-Interleaving auxiliary circuit. The proposed back-to-back voltage source converter has an independent control capability of active power and reactive power at the at connection point. The principle of increasing the number of pulses was analyzed using theoretical approach. The operational feasibility of proposed system was verified through computer simulations with PSCAD/EMTDC software. The proposed back-to-back converter can be widely used for the HVDC and FACTS devices.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.110-113
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• 2002

Organic EL has been expected to adopt to a new styles of technology that make flat display after Tang & Vanslyke made good electric luminescence device in late 1980s. Their studies based on multi layer structure that consists of emitting layer and carrier transporting layer using proper organic material. In this study. we made multi layer device using $Eu(TTA)_3(phen)$ as a luminescence material by PVD and investigate luminous properties of each device. But oxidization of organic layer by ITO. energy walls in both pole interface. contaminations of ITO surface, importance of protecting membrane, diffusive dimming of light to cathode organic layer. these causes of degradations are common facts of a macromolecule and micromolecule. We think these degradation caused by the impact of heat and electro-chemical factor, bulk effect and interface phenomenon. and raise a question.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.198-200
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• 2004

The purpose of this paper is to explain improvement of voltage stability using STATCOM by active power margin and reactive power margin. STATCOM, the representative shunt compensator of the FACTS devices, is faster than machinery compensator in response speed and has the advantage of the small scale because it doesn't use reactor or large capacitor. In this paper, we investigated the compensatory effect of the STATCOM that applied to KEPCO system.

• Proceedings of the KIEE Conference
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• summer
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• pp.171-173
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• 2004

This paper presents the selection of optimal placement for STATCOM (Static synchronous Compensator) which is one of the FACTS (Flexible Alternating Current Transmission System) devices, considering line contingency. Line contingency ranking is gotten by using sensitivity of load margin. According to line contingency ranking line contingency was considered. And IOP (Index for selecting optimal Placement of STATCOM) is calculated by the variation of each bus's reactive mum for several line contingencies. The bus where has the biggest value of lOP is the most optimal placement to install STATCOM for voltage stability. IPLAN is used to program this part which get IOP. This study is carried out on the modified IEEE14 Bus Test System to confirm the efficiency of the method.