• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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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.

• Journal of the Korea Society of Computer and Information
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• v.25 no.4
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• pp.141-148
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• 2020

Automatic term extraction is to recognize domain-specific terms given a collection of domain-specific text. Previous term extraction methods operate effectively in unsupervised manners which include extracting candidate terms, and assigning importance scores to candidate terms. Regarding the calculation of term importance scores, the study focuses on utilizing sets of inner and outer terms of a candidate term. For a candidate term, its inner terms are shorter terms which belong to the candidate term as components, and its outer terms are longer terms which include the candidate term as their component. This work presents various functions that compute, for a candidate term, term strength from either set of its inner or outer terms. In addition, a scoring method of a term importance is devised based on C-value score and the term strength values obtained from the sets of inner and outer terms. Experimental evaluations using GENIA and ACL RD-TEC 2.0 datasets compare and analyze the effectiveness of the proposed term extraction methods for English. The proposed method performed better than the baseline method by up to 1% and 3% respectively for GENIA and ACL datasets.

• Journal of Industrial Technology
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• v.27 no.B
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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.

• Journal of the Korean Mathematical Society
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• v.57 no.5
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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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.11
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3797-3803
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• 2009

Innovative capacities and performance are essential for the growth of the IT industry and the development of the Korean economy. Global R&D centers are important sources of innovation in the IT industry. In order to identify the structure of the innovation environment of global R&D centers in IT industry, we conducted a field survey of 50 global R&D centers and 50 global R&D policy experts in IT industry. According to the empirical results obtained using the Linear Structure Model, it is suggested that, first, with regard to a short-term IT global policy, the direction of the Korean government's policy should act as a trigger to connect the research domain and the market domain; second, the government policy should act as a facilitator to connect the development domain and the research domain in the mid-term period; and, finally, the government's R&D policy should serve as a disseminator to connect technological capability and the market space domain in the long-term perspective. For an effective way of internationalizing innovation, IT policy planners should regard global IT R&D centers as the important components of national innovation system and encourage the effective involvements by them in the process of IT industrial innovation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.139-144
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• 2009

The leveling of technical internet domain term with its aim to accumulate knowledge that machine can comprehend, which has been used widely in recent years. If stratify domain term weight, we believe that machine can manage and analyze in formation on its own using the ontology. In this paper, we propose an algorithm that allows us to extract properties of ontology weight from structured information already existing in web documents. In particular by stratification of the domain knowledge that is composed of property information, we were able to make the algorithm better and improve the quality of extraction results. In our experiments with 50 thousands targeted documents, we were able to extract property information with 94% confidence.

• Wind and Structures
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• v.27 no.6
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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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.4
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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.

• Journal of the Korean Mathematical Society
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• v.33 no.1
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• pp.89-99
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• 1996