• 전기학회논문지
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• 제63권12호
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• pp.1683-1689
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• 2014

In this paper, we propose an image processing based time-frequency domain reflectometry(TFDR) in order to estimate the fault location of a cable. The Wigner-Ville distribution is used for analysis in both the time domain and the frequency domain when the conventional TFDR estimates the fault location in a cable. However, the Winger-Ville distribution is a bi-linear function, and hence the cross-term is occurred. The conventional TFDR cannot estimate the accurate fault location due to the cross-term in case the fault location is close to the position where the reference signal is applied to the cable. The proposed method can reduce the cross-term effectively using binarization and morphological image processing, and can estimate the fault location more accurately using the template matching based cross correlation compared to the conventional TFDR. To prove the performance of the proposed method, the actual experiments are carried out in some cases.

• 한국컴퓨터정보학회논문지
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• 제25권4호
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• pp.141-148
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• 2020

용어추출은 도메인 텍스트 모음으로부터 도메인 용어 목록을 인식하는 작업이다. 용어추출의 기존 효과적인 방법들은 비교사 방식으로 동작하며, 후보 용어 집합을 추출하는 작업과 후보 용어에 용어중요도를 할당하는 작업을 주요 단계로 포함한다. 후보 용어의 용어중요도 계산과 관련하여 본 논문에서는 후보 용어의 내부 및 외부용어집합을 활용한다. 내부용어집합은 후보 용어에 포함된 다른 짧은 용어들의 집합이며, 외부용어집합은 후보 용어가 포함된 다른 긴 용어들의 집합이다. 본 논문에서는 후보 용어의 내부 혹은 외부용어집합으로부터 후보 용어의 용어 강도를 계산하는 다양한 강도 함수들을 제시하고, 이들 용어 강도 값들과 C-value 점수를 결합하는 용어중요도 계산 방법을 소개한다. 생물학 및 전산언어학 분야 영어 데이터셋을 사용한 성능 평가에서는 제안된 방법의 용어추출 성능을 비교하고 분석한다. 제안된 방법은 생물학 및 전산언어학 분야 데이터셋에 대해 각각 최대 1%와 3% 차이의 성능 향상을 보였다.

• 산업기술연구
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• 제27권B호
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• pp.21-27
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• 2007

The power line channel has time-variant characteristics caused by various kind of electrical devices. This characteristics are synchronized with the main voltage by their own characteristics. The main factors of disturbance are the variation of the channel impedance and noises. In other papers, the synchronous noise modeling has been achieved. But the modeling is not satisfied simultaneously with the time domain and the frequency domain and there are not any discussion about short-term variations of the channel impedance which cause to the signal fading. Therefore, this paper researched to solve problems about the signal fading by analyzing the short-term variation of the channel impedance, and proposed the synchronous noise modeling which is satisfied simultaneously in the time domain and the frequency domain.

• 대한수학회지
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• 제57권5호
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• pp.1267-1286
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• 2020

We pay attention to a coupled problem by a penalty term which is induced from non-overlapping domain decomposition methods based on augmented Lagrangian methodology. The coupled problem is composed by two parts mainly; one is a problem associated with local problems in non-overlapping subdomains and the other is a coupled part over all subdomains due to the penalty term. For the speedup of iterative solvers for the coupled problem, we propose two different types of preconditioners: a block-diagonal preconditioner and an additive Schwarz preconditioner as overlapping domain decomposition methods. We analyze the coupled problem and the preconditioned problems in terms of their condition numbers. Finally we present numerical results which show the performance of the proposed methods.

• 대한전기학회논문지:전력기술부문A
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• 제52권11호
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• pp.632-638
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• 2003

Modern power systems are very complex and to model them completely is impractical for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of frequency dependent equivalent. The s-domain rational function form of frequency dependent equivalent does not need refitting if the simulation time-step is changed in the electromagnetic transient program. This is because the s-domain rational function coefficients are independent of the simulation time-step, unlike the z-domain rational function coefficients. S-domain rational function fitting techniques for representing frequency dependent equivalents have been developed using Least Squares Fitting(LSF). However it does not suffer the implementation error that exited in this work as it ignored the instantaneous term. This paper Presents the formulation for developing 1 Port Frequency Dependent Network Equivalent(FDNE) with the instantaneous term in S-domain and illustrates its use. This 1 port FDNE have been applied to the CIGRE Benchmark Rectifier test AC system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the 1 port (FDNE) developed with Thevenin and Norton Equivalent network. The study results have indicated the robustness and accuracy of 1 port FDNE for electromagnetic transient studies.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3797-3803
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• 2009

우리나라 IT산업성장에서 혁신잠재력과 혁신수행능력이 중요한 역할을 했다. 글로벌 R&D센터는 IT산업의 혁신의 중요한 요소이다. IT산업에서 혁신환경에 대한 글로벌 R&D센터구조를 파악하기 위하여 R&D센터구성원과 정책입안자 각 50명씩 현장설문을 실시하였다. 본 실증분석결과를 보면 단기적으로 R&D정책은 연구영역과 시장역역의 인식차이를 해소하는 촉진자로서 역할이 중요하며, 중기적으로 R&D정책은 개발과 시장의 영격의 인식차이를 좁히는 조정자로 그리고 장기적으로는 기술능력과 시장의 확산 자로서 역할이 중요함을 보여준다. IT 정책입안자는 R&D정책에서 글로벌 R&D센터를 혁신체계의 요소로 활용하는 것이 요구된다.

• 한국인터넷방송통신학회논문지
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• 제9권4호
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• pp.139-144
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• 2009

최근의 여러분야에서 검색되어지고 있는 인터넷 도메인 용어의 전문성의 표시화는 온톨리지를 통한 지식의 축적의 목표가 되고 있다. 도메인 용어의 중요성을 표시화 한다면 기계가 온톨리지를 이용하여 정보의 관리 및 해석을 스스로 하는 것이 가능할 것으로 본다. 본 논문에서는 온톨로지의 중요성 (weight)을 구성하는 속성을 확장된 퍼지를 사용하여 기존 웹문서의 구조정보로부터 추출하는 알고리즘을 제안하였다. 특히 속성정보로 구성된 도메인 지식을 표시화 함으로써 속성추출 알고리즘을 개선하고, 추출결과의 품질을 향상시킨다. 5만문서를 대상으로 제안된 알고리즘을 적용한 결과 약 94%의 신뢰도의 속성정보를 추출할 수 있었다.

• Wind and Structures
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• 제27권6호
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• pp.357-368
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• 2018

For a long cable-stayed bridge, stay cables are its most important load-carrying components. In this paper, long-term monitoring of super-long stay cables of Sutong Bridge is introduced. A comprehensive data analysis procedure is presented, in which time domain and frequency domain based analyses are carried out. In time domain, the vibration data of several long stay cables are firstly analyzed and the standard deviation of the acceleration of stay cables, and its variation with time are obtained, as well as the relationship between in-plane vibration and out-plane vibration. Meanwhile, some vibrations such as wind and rain induced vibration are detected. Through frequency domain analysis, the basic frequencies of the stay cables are identified. Furthermore, the axial forces and their statistical parameters are acquired. To investigate the vibration deflection, an FFT-based decomposition method is used to get the modal deflection. In the end, the relationship between the vibration amplitude of stay cables and the wind speed is investigated based on correlation analysis. Through the adopted procedure, some structural parameters of the stay cables have been derived, which can be used for evaluating the component performance and corresponding management of stay cables.

• 대한전기학회논문지:전력기술부문A
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• 제54권4호
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• pp.165-171
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• 2005

Electromagnetic transient simulation can be used to model complex non-linearities that very difficult to represent adequately in the frequency domain. This problem is greatly reduced with the use of frequency dependent network equivalents for the linear part of the system. S-domain rational function fitting techniques for representing frequency dependent equivalents have been developed using Least Squares Fitting(LSF). However it does not suffer the implementation error that exited in this work as it ignored the instantaneous term. This paper presents the formulation for developing 2 port Frequency Dependent AC System Equivalent(FDACSE) with the instantaneous term in S-domain and illustrates its use. This 2 port FDNE have been applied to the New Zealand AC system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the 2 port (FDACSE) developed with Norton Equivalent network. The study results have indicated the robustness and accuracy of 2 port FDACSE for electromagnetic transient studies.

• 대한수학회지
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• 제33권1호
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• pp.89-99
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• 1996