• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.272-273
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• 2015

This paper analyze scenario of feeder wire fault that occurs in the AC feeding system considering train position. The fault location of AC feeding system is calculated by measuring impedance. However, in this way, estimation error can be occurred because of tie connection, boosting current, etc. Therefore, it's hard to find fault location, so that it is required to detailed circuit analysis according to fault location. We analyze the short circuit impedance values with respect to feeder wire fault according to a train position. In this paper, PSCAD is used for modeling and analysis of AC railway feeding system.

• Proceedings of the Korean Magnestics Society Conference
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• 2012.11a
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• pp.24-25
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• 2012

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1547-1553
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• 2017

Due to the high penetration ratio of dispersed generations, overvoltage problem of the feeder has become more an important issue in distribution system operation. This paper proposes a new method for the smart inverter to control reactive power to mitigate voltage rise by the reverse power flow from the DGs. The proposed method controls reactive power based on current measurement while conventional methods use voltage measurement which include unacceptably large errors. Various case studies using MATLAB simulation have been performed to verify effectiveness of proposed method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.402-408
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• 2015

A series of numerical simulations have been carried out to study the performances of cyclone-type oil separators, which are designed for refrigeration-system compressors. The corresponding working fluid is R22, which is a typical refrigerant, whereby a mineral-oil droplet is supplied (Ed-highlight-My interpretation). The outlet-tube length in relation to the total chamber volume is considered a design parameter. Depending on the tube length, the separation efficiency varies from 98.7% to 99.3%, while the predicted pressure drop is between 5.1 kPa and 6.4 kPa. Considering both the pressure drop and separation efficiency, the length of the outlet-port tube of the separator is 152 mm.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.181-184
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• 2018

최근 주목 받고 있는 소프트웨어 정의 네트워크(SDN: Software-Defined Networks)는 기존 네트워크 운용의 비효율성과 복잡성을 근본적으로 해결하기 위해 등장한 개방형 네트워크 인프라이다. SDN 시스템이 점차 상용화, 개방화 되는 시점에서, 내재되어있는 보안적 위협을 줄이기 위하여 효율적이고 자동화된 취약점 탐지의 필요성이 대두되고 있다. 본 논문에서는 자동화된 소프트웨어 테스트 기법 중 하나인 퍼즈테스팅이 SDN에 적용되어야 할 이유를 살펴보고자 한다. 또한, 기존에 관련된 연구의 분석을 통해 현재 학계의 연구동향을 파악하고 앞으로의 연구 방향성을 제시한다.

• Journal of Korean Society of societal Security
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• v.2 no.1
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• pp.47-55
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• 2009

Organizations and customers lose if business activities are discontinued by an incident of information systems under the current business environment because they pursue real time enterprise and on demand enterprise. The loss includes the intangible decline in brand image, customer separation, and the tangible loss such as decrease in business profits. Thus, it is necessary to have preparedness in advance and mitigation for minimization of a loss due to the business discontinuity and IT risks. This paper described a IT risk assessment case about domestic construction company.

• KIPS Transactions on Software and Data Engineering
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• v.9 no.3
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• pp.77-82
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• 2020

Most of the navigation in the vehicle has been developed based on a complex structure of PSF(Physical Storage Format) files, making it difficult to support incremental map updates. DB-based navigation is drawing attention as a next-generation navigation method to solve this problem. In DB-based navigation that supports incremental map updates, data fragmentation due to continuous map data updates can increase data access costs, which can lead to a decrease in search performance. In this paper, as one of the performance enhancement methods of DB-based navigation that supports incremental map updates, data fragmentation prevention techniques were presented and the performance improvement effect was verified through actual implementation.

• The Journal of the Acoustical Society of Korea
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• v.36 no.6
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• pp.394-400
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• 2017

This paper shows the extension of SpSF (Sparse Spectrum Fitting) algorithm, which is one of covariance matrix fitting-based DOA (Direction-of-Arrival) estimation algorithms, from the time domain to the frequency domain, and presents that SpSF can be implemented in the frequency domain. The superiority of the SpSF algorithm has been demonstrated by comparing DOA estimation performance with the performance of Conventional DOA estimation algorithm in the frequency domain for sinusoidal incident signals.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.115-122
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• 2017

We propose a robust adaptive beamforming algorithm for triplet array sonar. The proposed beamforming algorithm obtains robustness to mismatches, left/right discrimination, and has two steps. The first is a cardioid beamformer, which supports left/right discrimination of target signals. It applies the conventional delay-and-subtract to each triplet's signal with its rotation angle and obtains multiple cardioid beams. The second is a robust adaptive beamforming to minimize nearby interferences. We regard cardioid beams as input signals of a line array and apply an adaptive beamforming algorithm to the cardioid beams. Simulations results show that the proposed algorithm provides significantly better performance than the conventional algorithms, while supporting left/right discrimination of target signals.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.100-107
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• 2017

The focused MVDR (Minimum Variance Distortionless Response) can be applied for source localization in near field. However, if the number of sensors are increased, it requires a large amount of calculation to obtain the inverse of the covariance matrix. In this paper we propose a focused MVDR method using that beam space is formed from output of far field beamformer at the subarray. The performances of the proposed method was evaluated by simulation. As a result of simulation, the proposed method has the higher spatial resolution performance then the conventional delay-and-sum beamformer.