• Journal of the Korean Society of Industry Convergence
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• v.18 no.4
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• pp.191-196
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• 2015

In this paper, we present a path-smoothing algorithm for a robot arm manipulator that finds the path using a joint space-based rapidly-exploring random tree. Unlike other smoothing algorithms which require complex mathematical computation, the proposed path-smoothing algorithm is done using a Gaussian process. To find the optimal hyperparameters of the Gaussian process, we use differential evolution hybridized with opposition-based learning. The simulation result indicates that the Gaussian process whose hyperparameters were optimized by hybrid differential evolution successfully smoothed the path generated by the joint space-based rapidly-exploring random tree.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.138-143
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• 2005

A hierarchical tree structure of clusters has advantages for the network design due to its scalability and simple routing protocol. In this paper, the cluster tree routing protocol is studied for the wireless sensor network. From the numerical analysis results, the data aggregation in the intermediate nodes reduces the number of communication message and saves the energy of sensor nodes, but it may result in increased data traffic latency. And also the selection of cluster head can increase the relaying hops very high.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.396-399
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• 2012

Topic detection is a problem of discovering the topics of online publishing documents. For topic detection, it is important to extract correct topic words and to show the topical words easily to understand. We consider a topic tree-based approach to more effectively and more briefly show the result of topic detection for online text documents. In this paper, to achieve the topic tree-based topic detection, we propose a new term weighting method, called CTF-CDF-IDF, which is simple yet effective. Moreover, we have modified a conventional clustering method, which we call incremental k-medoids algorithm. Our experimental results with Reuters-21578 and Google news collections show that the proposed method is very useful for topic detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.756-763
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• 2014

In this paper, we introduce a new sparse signal recovery algorithm referred to as the matching pursuit with greedy tree search (GTMP). The tree search in our proposed method is implemented to minimize the cost function to improve the recovery performance of sparse signals. In addition, a pruning strategy is employed to each node of the tree for efficient implementation. In our performance guarantee analysis, we provide the condition that ensures the exact identification of the nonzero locations. Through empirical simulations, we show that GTMP is effective for sparse signal reconstruction and outperforms conventional sparse recovery algorithms.

• JOURNAL OF ELECTRICAL WORLD
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• no.4 s.100
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• pp.48-51
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• 1985

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.901-903
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• 1998

Crosslinked Degree is an important factor to determine dielectric property of crosslinked polyethylene(XLPE) used for the insulation material in power cables. Recently, though it is necessary to investigate electrical properties according to crosslinked degree as a part of the whole characterization of cable. it is not examined closely. In this study, crosslinked degree of samples were measured according to temperature and holding time of crosslinking, electrical tree characteristics of these samples were analyzed by crosslinked degree and applied temperature that was changed from normal temperature to operating temperature of power cables. As a result. when the crosslinked degree was low, dielectric properties were decreased and influence of temperature was increased. but the crosslinked degrees were high. initiation voltages of treeing were increased and dielectric properties were improved. It is proved that the optimum. crosslinked degree was one of most important factor for aging time and residual lifetime of power cable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1322-1329
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• 2018

In this paper, the reliability test of three kinds of epoxy resin for GIS Spacer, which is a high voltage based heavy electric machine, AC electrical treeing experiments were performed. Three types of epoxy resins, Araldite B41, CT 5531 CI and B46, have slight viscosity differences. An non-uniform electric field, E = 1149.4 kV/mm, as the needle to plate electrode, a power source with a frequency of 1 kHz was applied to the tree electrode for accelerated deterioration. The treeing phenomena of the three kinds of epoxy resin all initiated, propagated, and destroyed by the branch tree. Epoxy Resin B46 was 145 times longer than B41 and 53 times longer than CT 5531CI. I think that the choice of epoxy resin is very important in choosing high voltage heavy electric machine insulation materials.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.552-558
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• 2009

We proposed a semi-blind digital image watermarking technique for copyright protection. The proposed algorithm embedded a binary sequence watermark into significant wavelet coefficients by using a quantization method. The main idea of the quantization method was to quantize a middle coefficient of the triplet of a significant wavelet coefficient according to the watermark's value. Unlike an existing algorithm, which used a random location table to find a coefficient in which the watermark bit will be embedded: the proposed algorithm used quad-tree decomposition to find a significant wavelet coefficient for embedding. For watermark detection, an original host image was not required. Thanks to the usage of significant wavelet coefficients, the proposed algorithm improved the correlation value, up to 0.43, in comparison with the existing algorithm.

• ETRI Journal
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• v.29 no.4
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• pp.507-515
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• 2007

Skeleton transform of which the medial axis transform is the most popular has been proposed as a useful shape abstraction tool for the representation and modeling of human posture. This paper explains this proposition with a description of the areas in which skeletons could serve to enable the representation of shapes. We present algorithms for two-dimensional posture modeling using the developed simplified shock graph (SSG). The efficacy of SSG extracted feature vectors as shape descriptors are also evaluated using three different classifiers, namely, decision tree, multilayer perceptron, and support vector machine. The paper concludes with a discussion of the issues involved in using shock graphs to model and classify human postures.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1476-1477
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• 2006

Solid insulation exposed to voltage is degraded and by electrical tree process. And the degradation of the insulation is accelerated by voltage application. For this experimental, specimen of electrical tree model is made by XLPE(cross-linked polyethylene). And the size of the specimen is 7*5*7 $mm^3$. Distance of needle and plane is 2mm. Voltage applied for acceleration test are 12kV. And distribution characteristic of degraded stage is studied too. As a PD detecting and data process, discharge data acquire from PD detecting system(Biddle instrument). Their results of PD distribution show good present and are good discriminating skill.