• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.12-16
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• 2015

In this paper, we introduce a wireless package system based on the amateur radio HR(HAM Radio) and satellite communication as a novel wireless disaster communication system and have configured a interference scenario receiving interference from adjacent base stations and D2D groups in the disaster network. In such interference scenarios, we propose a frequency re-allocation method to avoid interference and communicate with disaster networks by securing the channel capacity required between D2D terminals. As a result of computer simulation, we can find the proposed method has improved BED performance of a gain of 1.5dB and overall system throughput than conventional methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.322-331
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• 2002

In this paper, a single-phase to three-phase PWM converter topology using a single-phase half-bridge PWM rectifier and a 2-leg inverter for low cost three-phase induction motor drives is proposed. In addition, the source voltage sensor is eliminated with a state observer which controls the deviation between the model current and the system current to be zero. The converter topology is of lower cost than the conventional one, which gives sinusoidal input current, unity power factor, dc output voltage control, bidirectional power flow and VVVF output voltage. The experimental results for V/F control of 3Hp induction motor drives have been shown.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.225-230
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• 1996

We propose a statistical test for the nonlinear combiner logics which are usually combined with two maximal Linear Feedback Shift Registers and generate pseudorandom bit sequences. This test uses the mutual information between the output and set of inputs which will be a random variable and its distribution is obeyed to an approximate $\{chi}^2$ -distribution. We adopt this statistic to a $\{chi}^2$ -test of independence by using contingency table. We also apply a proposed test to some non-linear crptosystems and show that this useful to evaluate the strength of the cryptosystems.

• Annual Conference on Human and Language Technology
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• 1999.10d
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• pp.123-136
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• 1999

자연언어처리 분야에서 형태소 분석은 가장 기본적인 단계로서 응용 시스템의 목적에 따라 사용되는 형태소 분석기의 수준과 사용 정보가 달라진다. 기존의 형태소분석기의 기능을 다른 목적을 지닌 응용 시스템에서 사용하려 할 때, 분석수준과 사용정보의 이질성으로 인해 변경 또는 확장하는데 많은 어려움이 있다. 이러한 형태소 분석기의 변경과 확장에 대한 다양한 요구를 수용하기 위한 방법으로서 재사용가능한 모듈화된 형태소 분석기의 구현을 제안한다. 모듈화된 형태소 분석기는 구성 요소인 모듈들의 독립성과 재사용성을 보장하기 때문에 확장과 보수가 쉽고, 특정한 요구사항에 대하여 새로운 형태소 분석기를 구현하는데 기존의 모듈들을 사용함으로써 시스템의 개발 시간을 단축시킨다. 본 논문에서는 이러한 모듈들의 사용성을 보여주기 위해 전처리기, 형태소 분석기, 명사 추출기, 태거 등을 하나의 시스템 안에 모듈화된 개념으로 구현하였고, 형태소 분석기는 사전, 음운 변화 처리, 결합 검사, 분석 알고리즘 등을 모듈화하여 재사용할 수 있다는 것을 보여준다.

• Journal of Digital Convergence
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• v.12 no.6
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• pp.237-243
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• 2014

In this paper, we propose a mobile image retrieval system which utilizes the mobile device's sensor information and enables running in a variety of the environments, and implement the system on Android platform. The proposed system deals with a new image descriptor using combination of the visual feature with EXIF attributes in the target of JPEG image, and image matching algorithm which is optimized to the mobile environments. Experiments are performed on the Android platform, and the experimental results revealed that the proposed algorithm exhibits a significant improved results with large image database.

• Computational Structural Engineering
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• v.9 no.1
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• pp.141-149
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• 1996

Efficient approximate reanalysis techniques based on substructuring are presented. In most optimal design problems, the analysis precedure must be repeated many times. In particular, one of the main obstacles in the structural optimization systems is high computational cost and time required for the repeated analysis of large-scale structural systems. The purpose of this paper is to show how to evaluate efficiently the sturctural behavior of new designs using information from the previous ones, instead of the multiple repeated analysis of basic equations for successive modification in the optimal design. The proposed reanalysis method is a combined Taylor series expansion and reduced basis method based on substructuring. Several numerical examples illustrate the effectiveness of the method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.24-29
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• 2011

Comparing conventional one-way relaying, two-way relaying scheme with network coding can achieve high throughput by reducing the transmission time. Coded cooperation protocol, which is a algorithm that uses coding on physical layer, can achieve high reliability. In this paper, we propose coded cooperation protocol over two-way relay network. Simulation results show proposed protocol has better performance in terms of reliability and throughput compare with conventional amplify and forward protocol. Also, with same throughput, proposed protocol has better performance in terms of reliability compare with the conventional hybrid decoded and forward protocol.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.5
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• pp.583-586
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• 2004

Transition jitter noise is one of major sources of detection errors in high density recording channels. Implementation complexity of the optimal detector for such channels is high due to the data dependency and correlated nature of the jitter noise. In this paper, two types of hardware efficient sub-optimal detectors are derived by modifying branch metric of Viterbi algorithm and applied to partial response (PR) channels combined with run length limited modulation coding. The additional complexity over the conventional Viterbi algorithm to incorporate the modified branch metric is either a multiplication or an addition for each branch metric in the Viterbi trellis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.492-503
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• 2013

H.264/AVC has shown high coding efficiency by using various coding tools, including intra and inter prediction. However, there are still many more redundancy components in intra prediction than in inter prediction. In this paper, a novel intra prediction method is proposed with adaptive mode selection. The combined intra prediction modes and simplified gradient modes are added in order to refine the directional feature and gradation region. Suitable modes are selected according to the neighboring blocks that provide a high compression rate and lower computational complexity. The improvement of the proposed method is 1.96% in terms of the bitrate, 0.25 dB in PSNR, and 1.72 times in terms of the computational complexity.

• 전자공학회논문지 IE
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• v.49 no.2
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• pp.24-29
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• 2012

The sounds of exhaust emissions of automobiles are independent sound sources which are nothing to do with voices. We have no information for the sources of voices and exhaust sounds. Accordingly, Independent Component Analysis which is one of the Blind Source Separaton methods was used to segregate two source signals from each mixed signals. Maximum Likelyhood Estimation was applied to the signals came through the stereo microphone to segregate the two source signals toward the maximization of independence. Since there is no clue to find whether it is speech signal or not, the coefficients of the slope was calculated by the autocovariances of the signals in frequcency domain. Noise remover for speech signals was implemented by coupling the two algorithms.