• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.9-15
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• 2011

In this paper, we designed and fabricated a dual-band bandpass filter which can control upper and lower bandwidth using the transformed E-shaped dual-mode resonator. The filter is made the coupling between even-mode not to affect odd-mode resonant frequency by the transformed resonator to control upper bandwidth effectively. The cross coupling between input and output feed lines was employed to improve stopband characteristic. The bandpass filter has been designed to indicate the same bandwidth at center frequency 2 GHz and 3 GHz to show to control bandwidth.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.05a
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• pp.387-392
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• 2005

최근에는 LiDAR 시스템의 등장으로 기존의 항공사진측량에 비하여 효율적이고, 경제적으로 도시지역의 수치표고자료를 효과적으로 구축할 수 있게 되었으나, 도시지역에서는 다양한 형태의 객체들이 모두 포함된 DSM(Digital Surface Model) 형식의 자료를 취득하게 된다. 따라서, 홍수범람예측에 있어서의 인공지물의 영향 해석 등을 위하여 건물이 제거된 지형에 관한 상세한 정보를 제공하기 위해서는 DSM으로부터 DEM(Digital Elevation Model)을 추출하기 위한 전처리 과정이 필요하다. 본 연구는 LiOAR 시스템으로부터 취득된 도시지역에 대한 DSM으로부터 건물 등이 제거된 DEM을 추출하기 위한 연구로서 영상처리기법의 경계검출 알고리즘을 적용하여 건물 등의 지물들에 대한 경계를 추출하였으며, 선행연구에서 건물로 추출된 지역에 대하여 보간법을 적용함으로써 발생하는 원시 DSM 자료의 변형에 따른 대안으로써, 추출된 경계에 대여 평균값 필터링, 중간 값 필터링, 최소 값 필터링을 각각 적용함으로써 원시 DSM 자료의 변형을 최소화하여 건물 등의 지물들을 제거하였으며, LiDAR DSM으로부터 DEM을 제작하는 과정을 간략화, 자동화하였다.

• The Transactions of the Korea Information Processing Society
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• v.2 no.1
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• pp.106-118
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• 1995

In this work, the optimized design methodology in high-level synthesis related with scheduling and hardware allocation is developed by simulated annealing technique effectively modified . Applying this method to digital filter design, the optimized tradeoff problem of speed and hardware costs in pipelined digital filter case and array digital filter case are investigated. While, it is confirmed that the suggested method gives the improved cost function value faster and can be used in complicated digital filter design.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.7
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• pp.271-276
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• 2014

Short message service(SMS) in a mobile communication environment is a very convenient method. However, it caused a serious side effect of generating spam messages for advertisement. Those who send spam messages distort or deform SMS sentences to avoid the messages being filtered by automatic filtering system. In order to increase the performance of spam filtering system, we need to recover the distorted sentences into normal sentences. This paper proposes a method of normalizing the various types of distorted sentence and extracting keywords through automatic word spacing and compound noun decomposition.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.113-120
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• 2009

Currently the verbal abuse in text message over on-line game is so serious. However we do not have any effective policy or technical tools yet. Till now in order to cope with this problem, the online game service providers have accumulated a set of forbidden words and applied this list on the textual word used in on-line game, which is called 'Swear filter'. But young on-line game players easily avoid this filtering method by coining another words which is not kept in the list. Especially Korean is very easy to make new variations of a vulgar word. In this paper, we propose one smart filtering algorithm to identify newly coined profanities. Important features of our method include the canonical form transformation of coined profanities, semi-global alignment between in the level of consonant and vowel units. For experiment, we have collected more than 1000 newly coined vulgar words in on-line gaming sites and tested these word against our methods. where our system have successfully filtered more than 90% of those newly coined vulgar words.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.139-150
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• 2023

Terretial LiDAR surveying is highly useful for maintenance of civil facilities as it can easily detect the temporal deformation of structures or topography. However, for river facilities such as levess, it is difficult to detect the deformation of the topography or structure under vegetations due to the influence of vegetation. Vegetation filters can be divided into color filters and morphological filters. In this study, combined filters with color and morphology are developed to improve the accuracy of vegetation filters. 8 color filters, 6 morphological filters, and 4 combined filters are applied to the vegetation removal on the embankment slope, and their accuracy and calculation time are compared. Color filters show a short calculation time, but the accuracy was low in the vegetation area. Morphological filters show high accuracy in the vegetation area, but low accuracy in places with severe local topographical changes such as heavy rocks. Combined filters also show a tendency similar to morphological filters, but in the case of ExGGM, the accuracy is excellent in both the vegetation and rock area. Considering the accuracy and calculation time, the combined filter ExGGM is suitable for general cases, and the shape filter GrMIn or the complex filter ExGISL is suitable for cases where the local topographical change is not severe.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.351-354
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• 2007

In recent years, digital processing techniques have been applied diversity of fields. Typical signal processing techniques are speech processing and image processing. And filters for the signal processing can be divided in FIR (finite impulse response) filter and IIR (infinite impulse response) filter. Compared with IIR filter, the FIR Filter has a defect of high-degree, but has a merit of stability and uses simply. Futhermore, FIR filter also has linear phase response characteristics, it is using in fields regarding wave information importantly. To FIR Filter design, the main issue is to remove the Gibbs phenomenon. Therefore, in this paper I was proposed a method using FIR digital filter applied a modified window function and the method was compared with conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.114-119
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• 2019

The transmitted acoustic signals are severely influenced by multiply reflected signals from boundaries, such as sea surface and bottom in the shallow water. Very large reflection signals from boundaries cause inter-symbol interference so that the performance of the underwater acoustic communication is degraded. Usually, the waveform shaping filters are used to prevent the reflected signals under this kind of acoustic channel. Especially, the raised cosine filter is widely used, which can also be used to restrict the bandwidth of the transmitted signal. In this study, we evaluate the raised cosine filter for image data transmission in the shallow water, and propose a new modified raised cosine filter. The QPSK (Quadrature Phase Shift Keying) system is used for the underwater acoustic communication simulations with different distances and symbol rates. As a result, the bit error rate was reduced from the minimum 1.0 % to the maximum 32 %.

• Proceedings of the Acoustical Society of Korea Conference
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• 1996.06a
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• pp.18-21
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• 1996

예인형 선배열 소나에서 기존의 선배열 빔형성 기법을 적용하면 예인함 기동시 선배열 형상 변형에 의해 심각한 성능 저하 현상이 나타난다. 이러한 문제 해결을 위해 센서배열 변형을 고려한 견실한 빔형성 기법은 선배열 형상 추정을 위해 칼만필터를 이용한 형상 추정기법을 이용하고, 변형보상 빔형성을 위해 선배열 세그먼트 기울기 추정값을 이용하는 변형보상 빔형성 알고리즘을 제안하였다. 제안된 기법을 기존의 빔형성 기법을 적용하여 시뮬레이션에 의해 제안된 기법의 보상성능을 입증 하였다.

• Journal of Broadcast Engineering
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• v.6 no.1
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• pp.21-31
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• 2001

In the PN-sequence based audio watermarking system, the PN sequence is shaped by a filter derived from the psychoacoustic model to increase robustness and inaudibility The psychoacoustic model calculated in each audio segment, however, requires heavy computational loads. In this paper, we propose an efficient watermarking system adopting a fixed-shape perceptual filter that substitutes psychoacoustic model derived filter. The proposed filter can shape the PN-sequence to be inaudible and enable to embed the robust watermark in a simple manner. Moreover, we propose an anchitecture for the PN-sequence compensation fitter In the watermark detecter to increase correlation between the watermark and the PN-sequence. With the proposed architecture, the blind watermark detection performance has been enhanced.