• 전기학회논문지
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• 제63권10호
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• pp.1393-1401
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• 2014

In this paper the operational characteristics of stand-alone microgrid was analyzed using RTDS simulation models. The accuracy of developed simulation models were verified by comparing with the analysis results using the PSCAD/EMTDC simulation models. The proper scenarios and operation algorithms were developed and analyzed in accordance with various situations that can occur in the actual system, so as to establish operation scheme for the stand-alone microgrid system. The developed simulation models can be effectively utilized to design a newly installed stand-alone microgrid and to develop various operation scenarios for stand-alone microgrid. And these models can be applied for analyzing the transient phenomena due to system fault so that system protection can be properly designed.

• Progress in Superconductivity
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• 제13권3호
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• pp.189-194
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• 2012

Studies on the development of high voltage superconducting apparatuses, such as transmission superconducting fault current limiters (SFCLs) and superconducting cables, have been performed worldwide. In this paper, a study on the electrical insulation characteristics of electro negative gas according to various pressures and utilization factors was conducted as a part of developing a high voltage superconducting coil with a sub-cooled nitrogen cooling system. Some gases such as helium (He), nitrogen ($N_2$), and sulfur hexafluoride ($SF_6$) are considered for pressurizing the sub-cooled nitrogen cooling system of high voltage SFCLs and superconducting cables. $SF_6$ is used to pressurize and enhance the dielectric performance of a superconducting system of a sub-cooled nitrogen cooling system for superconducting cables being developed in the Republic of Korea. In this paper, dielectric experiments on AC voltage, as well as lightning impulse voltage of $SF_6$, are conducted according to various utilization factors by using several kinds of sphere-to-plane electrode systems. As results, it is known that the empirical formulae of $SF_6$, known as an electro negative gas, are derived according to various pressures and utilization factors. Also, the appropriate pressure condition for designing a high voltage superconducting coil is found from the viewpoint of dielectric performance.

• 한국한의학연구원논문집
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• 제12권2호통권17호
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• pp.75-83
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• 2006

Pogostemonis and Agastachis Herba are the whole of Pogostemon cablin (BLANCO) BENTH or Agastache rugosa (FISCHER et MEYER) O. KUNTZE (family Labiatae) which is produced in all part of Korea and China. This drug is used for removing dampness by means of aromatics in oriental medicine. The standard formula of this drug is important from the viewpoint of the quality control. A characteristic discrimination of internal and external morphological standard in original plants and herbal states of Pogostemonis and Agastachis Herba are as follows. 1. The external characteristics: Pogostemon cablin has hairs and brown-like in stem, elliptical fruit. In the other hand, Agastache rugosa has no hairs and red-like in stem, obovatic trigone fruit. 2. The physical characteristics: Pogostemon cablin is gray in whole, has hairs in stem and numerous hairs of ash in leaf. In the other hand, Agastache rugosa is yellow-green in whole, has no hairs in stem. Specially the latter has deep-green colour and numerous hairs presenting mostly at lower epidermis in leaf. 3. The physical characteristics in currents: Pogostemon cablin is brown, has hairs and round-like stem. In the other hand, Agastache rugosa is green or yellow-green, has no hairs and tetragon in stem. 4. The internal characteristics: Pogostemon cablin has progressed spongy tissue in epidermal cell of leaf and many rank of epidermal cell in stem. In other hand, Agastache rugosa has 1 rank palisade tissue in leaf and few rank of epidermal cell in stem. In the external shape, it was possible that herbs were distinguished according to artificial classification and that same genus-degree of relatedness among herbs could be distinguished by more precise and active observation. In the shape of real herbs, I compared current herbs in market with original herbs which were just collected or were on the course of drying. In addition, it was possible that the internal shape could be identified by using microscope after butanol series. Though it was impossible to make distinction of herbs which are not current in my search contents, this search contents will be a standard for applying herbs in the future. An Additional standard establishment including physiochemical reaction and gene research is required in order to supplement the fault of this search.

• Geomechanics and Engineering
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• 제16권4호
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• pp.435-448
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• 2018

In order to make reliable earthquake-resistant design of civil engineering structures, one of the most important considerations in a region with high seismicity is to pay attention to the local soil condition of regions. It is aimed in the current study at specifying dynamic soil characteristics of Kirikkale city center conducting the 1-D equivalent linear and non-linear site response analyses. Due to high vulnerability and seismicity of the city center of Kirikkale surrounded by active many faults, such as the North Anatolian Fault (NAF), the city of Kirikkale is classified as highly earthquake-prone city. The first effort to determine critical site response parameter is to perform the seismic hazard analyses of the region through the earthquake record catalogues. The moment magnitude of the city center is obtained as $M_w=7.0$ according to the recorded probability of exceedance of 10% in the last 50 years. Using the data from site tests, the 1-D equivalent linear (EL) and nonlinear site response analyses (NL) are performed with respect to the shear modulus reduction and damping ratio models proposed in literature. The important engineering parameters of the amplification ratio, predominant site period, peak ground acceleration (PGA) and spectral acceleration values are predicted. Except for the periods between the period of T=0.2-1.0 s, the results from the NL are obtained to be similar to the EL results. Lower spectral acceleration values are estimated in the locations of the city where the higher amplification ratio is attained or vice-versa. Construction of high-rise buildings with modal periods higher than T=1.0 s are obtained to be suitable for the city of Kirikkale. The buildings at the city center are recommended to be assessed with street survey rapid structural evaluation methods so as to mitigate seismic damages. The obtained contour maps in this study are estimated to be effective for visually characterizing the city in terms of the considered parameters.

• 조명전기설비학회논문지
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• 제16권1호
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• pp.100-105
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• 2002

본 연구에서는 FACTS 기기 중 가장 우수한 기기로서 활발히 연구가 진행되고 있는 UPFC가 송전계통에 연계되었을 경우 거리계전기가 보는 임피던스 특성을 분석하였다. 최근, 계통 안정도와 전력 전송용랑을 증가시키기 위해 UPFC가 사용됨에 따라 기존의 보호계전기에 어떠한 영향을 줄 것인가를 미리 연구하여 보호계전기가 오동작 및 부동작이 나지 않도록 대책을 강구할 필요성이 있다. UPFC가 연계되어 운전되면 송전계통의 조건이 UPFC의 운전조건에 따라 변하게 되고 송전선로 보호용으로 설치된 거리계전기가 보는 임피던스값도 영향을 받을 것이다. 따라서 UPFC가 설치된 선로에서 사고를 검출하는 거리계전기가 임피던스를 계산시 UPFC기기에 의한 보상전압 크기와 위상을 충분히 고려해서 계산되어져야 한다. 본 연구에서는 UPFC기기가 연계된 송전선로에서 사고 발생시, 거리 계전기의 오동작을 방지하기 위해 보호협조가 필요함을 제시하였으며 PSCAD/EMTDC를 통해 UPFC와 계통을 모델링하여 사고를 모의후 거리계전기가 보는 임피던스 특성을 분석하였다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2292-2300
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• 2018

A field-circuit coupling model of a typical faulty generator is established to correct through-bolt end-region overheating and breakdown failure in a tubular hydro-generator. Using the model, eddy current loss and electromagnetic forces on through bolts under normal and failure conditions are analyzed and compared and the natural frequency of a through bolt is determined. Based on the analysis results, the causative mechanism of failure is revealed and targeted improvement design measures are proposed. The numerical results are found to be consistent with the actual fault characteristics, validating the design measure improvements. The results are useful in improving the design and manufacturing standards and enhancing the operational reliability of large tubular hydro-generators.

• International Journal of Contents
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• 제9권4호
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• pp.1-10
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• 2013

The electroencephalogram (EEG) time series is a measure of electrical activity received from multiple electrodes placed on the scalp of a human brain. It provides a direct measurement for characterizing the dynamic aspects of brain activities. These EEG signals are formed from a series of spatial and temporal data with multiple dimensions. Missing data could occur due to fault electrodes. These missing data can cause distortion, repudiation, and further, reduce the effectiveness of analyzing algorithms. Current methodologies for EEG analysis require a complete set of EEG data matrix as input. Therefore, an accurate and reliable imputation approach for missing values is necessary to avoid incomplete data sets for analyses and further improve the usage of performance techniques. This research proposes a new method to automatically recover random consecutive missing data from real world EEG data based on Linear Dynamical System. The proposed method aims to capture the optimal patterns based on two main characteristics in the coevolving EEG time series: namely, (i) dynamics via discovering temporal evolving behaviors, and (ii) correlations by identifying the relationships between multiple brain signals. From these exploits, the proposed method successfully identifies a few hidden variables and discovers their dynamics to impute missing values. The proposed method offers a robust and scalable approach with linear computation time over the size of sequences. A comparative study has been performed to assess the effectiveness of the proposed method against interpolation and missing values via Singular Value Decomposition (MSVD). The experimental simulations demonstrate that the proposed method provides better reconstruction performance up to 49% and 67% improvements over MSVD and interpolation approaches, respectively.

• Earthquakes and Structures
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• 제12권1호
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• pp.1-12
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• 2017

Historical earthquakes have shown that successive seismic events may occur in regions of high seismicity. Such a sequence of earthquakes has the potential to increase the damage level of the structures, since any rehabilitation between the successive ground motions is practically impossible due to lack of time. Few studies about this issue can be found in literature, most of which focused their attention on the seismic response of SDOF systems or planar frame structures. The aim of the present study is to examine the impact of seismic sequences on the damage level of 3D multistorey R/C buildings with various structural systems. For the purposes of the above investigation a comprehensive assessment is conducted using three double-symmetric and three asymmetric in plan medium-rise R/C buildings, which are designed on the basis of the current seismic codes. The buildings are analyzed by nonlinear time response analysis using 80 bidirectional seismic sequences. In order to account for the variable orientation of the seismic motion, the two horizontal accelerograms of each earthquake record are applied along horizontal orthogonal axes forming 12 different angles with the structural axes. The assessment of the results revealed that successive ground motions can lead to significant increase of the structural damage compared to the damage caused by the corresponding single seismic events. Furthermore, the incident angle can radically alter the successive earthquake phenomenon depending on the special characteristics of the structure, the number of the sequential earthquakes, as well as the distance of the record from the fault.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1146-1149
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• 2014

단자 표식이 불분명한 3상유도전동기에서 고정자 권선의 극성을 판별하는 데는 외부 여자전류에 의해 유도되는 기전력 특성에 기초하거나 또는 회전자의 잔류자기를 이용하는 방법이 가능하다. 회전자의 잔류자기로 유도되는 권선에서의 기전력은 자속 크기와 수동 구동의 회전자 속도 및 위상 관계에 따라 정해지며 이 같은 극성 판별이 작업현장에서 가능하려면 기전력의 크기가 멀티테스터로 확인될 수 있는 정도이어야 하고 또한, 코일 간 위상 특성이 극성 판별에 적합해야 한다. 잔류자기에 의한 기전력들이 3상 평형 관계에 있다면 전체 합성 전압은 권선들의 극성 연결 상태가 정상일 때 0이 되어야 하는 한편, 극성 연결의 오류 시에는 상대적으로 큰 출력 전압을 나타낸다는 점에서 본 연구에서는 각 경우에 대한 특성을 분석하였다. 또한, 잔류자기에 의한 판별 방식을 실험용 전동기에 적용하여 극성의 정상 및 이상 상태에서의 출력 파형을 비교함으로써 제시된 방식이 극성 판별 방법으로서 현장에서 용이하게 활용될 수 있는지를 확인한다.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.121-129
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• 2002

본 논문에서는 효과적인 접지그리드 설치기법에 대하여 기술하였으며, 낙뢰나 지락고장서지, 개폐서지 등으로 부터 인체의 감전보호나 컴퓨터를 비롯한 전기·전자기기의 보호를 위한 접지그리드의 시설 및 배치방법에 따른 실험적인 평가를 수행하였다. 접지그리드의 배치에 따른 대지표면전위경도의 분석과 위험전압으로 작용하는 대지 표면전위상승의 억제에 주안점을 두고 실험용 모델접지전극을 시설한 후 임 펄스전류를 인가하였다. 기존의 등간격 접지그리드의 결점을 보완하기 위해 접지그리드에 경사를 가지는 보조접지그리드를 시설하였으며, 보조접지그리드를 시설한 접지시스템에서는 인체나 전기·전자기기에 위험전압으로 작용하는 대지표면전위경도를 최대 50%이상 완화시키는 효과를 얻었다.