• Title/Summary/Keyword: 공간 필터

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An inverse filter design for multi-channel sound field reproduction system (다채널 음장 재현시스템에서의 역필터의 설계에 관한 고찰)

  • Park Byoung-Uk;Kim Hack-Yoon
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.241-244
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    • 2001
  • 다채널 음장 재현 시스템에서 공간 전달 특성을 제거하는 역필터의 설계가 불가결하다. 주파수영역에서 최소 Norm해를 이용한 설계 방법은 시간 영역 설계방법과 비교하여 볼 때, 적은 계산량과 메모리량으로 설계할 수 있다. 그러나, 이 방법에서는 역필터를 필요로 하게 되고 FIR 필터로 설계 가능하다는 보장이 없다. 따라서, 본 연구에서는 주파수 영역 처리를 반복하여 수행하는 것으로 다 채널 음장 재현시스템을 위한 안정한 역필터를 설계하는 방법을 제안한다.

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Small Target Detection Using 3-dimensional Bilateral Filter (3차원 양방향 필터를 이용한 소형 표적 검출)

  • Bae, Tae-Wuk
    • Journal of Korea Multimedia Society
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    • v.16 no.6
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    • pp.746-755
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    • 2013
  • This paper presents a three dimensional bilateral filter detecting target trajectory, extracting spatial target information using two dimensional bilateral filter and temporal target information using one dimensional bilateral filter. In order to discriminate edge pixel with flat background and target region spatially and temporally, spatial and temporal variance are used for an image and temporal profile. With this procedure, background and background profile are predicted without original target through two dimensional and one dimensional bilateral filter. Finally, using spatially predicted background and temporally predicted background profile, small target can be detected. For comparison of existing target detection methods and the proposed method, the receiver operating characteristics (ROC) is used in experimental results. Experimental results show that the proposed method has superior target detection rate and lower false alarm rate.

Off-axis pSDF Spatial Matched Filter for Pattern Classification (패턴분류를 위한 Off-axis pSDF 공간정합필터)

  • 임종태;박한규;김명수;김성일
    • Korean Journal of Optics and Photonics
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    • v.2 no.2
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    • pp.83-88
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    • 1991
  • Studies on space-invariant pattern recognition have been carried out from various approaches. Pattern recognition system using SDF filter, from weighted linear summation of tranining images, has been the focus of research since its first appearence. In this thesis, off-axis pSDF spatial matched filter has been constructed by combining angular multiplexing of off-axis reference plane wave with pSDF filter made from pseudo-inverse algorithm, and transformed to phase only filter. From observation of the correlation responses in the correlation plane, it is shown that proposed off-axis pSDF spatial matched filter is available to pattern classification and can be used for optical correlator.

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Acquisition of River Velocity Data Using Acoustic Doppler Current Profiler (ADCP를 이용한 하천 유속 자료의 추출)

  • Lee, Chan Joo;Lee, Du Han;Kim, Myoung Hwan
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.365-370
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    • 2004
  • 본 연구에서는 ADCP를 이용하여 수집된 3차원적 하천 유속 자료를 기기 특성상 오류, 운용상 오류 등을 고려하여 검토하였으며, 원시 자료의 편차를 보정하는 공간평균기법을 적용하여 필터링함으로써 유속 자료를 추출하였다 공간평균기법으로 추출된 자료는 원시 자료에 비해 유속 편차가 감소되어 매끄러운 유속 분포를 보여주었을 뿐만 아니라 원시 자료에 의한 유량 계산 결과와 거의 일치하여 유속 분포를 적절하게 필터링하는 것으로 파악되었다. 또한 공간평균된 유속 자료를 이용하여 하천의 흐름장을 일목요언하게 제시할 수 있는 평면적 유속 벡터와 단면상 유속 벡터를 제시하였다. 차후 다른 유속계를 이용한 결과와 적절히 비교된다면 공간평균된 자료는 원시 자료에 비해 보다 유용할 것으로 예상되며 하천 흐름 해석 및 수치 모의에 기초 자료로 이용될 수 있을 것으로 기대된다.

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Change of Contrast Sensitivity Induced by Tinted Spectacle Lens (칼라필터 렌즈에 따른 대비감도의 변화)

  • Seo, Jae-Myoung
    • Journal of Korean Ophthalmic Optics Society
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    • v.21 no.1
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    • pp.47-51
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    • 2016
  • Purpose: The purpose of this study was to investigate the change of contrast sensitivity by prescribing tinted lenses and to provide the clinical manual. Methods: Contrast sensitivity was measured for twenty adults with normal vision while they wore yellow, orange and green tinted lenses. To measure contrast sensitivity, the 5 spatial frequencies (2, 4, 6, 8 and 10 cpd) were used for 33 ms and 233 ms, respectively. Results: The contrast sensitivity was overall higher with 233 ms than 33 ms (p<0.05). The peaks of contrast sensitivity with 33 ms and 233 ms were 1.75 log unit with the yellow lens and 1. 85 log unit without the color respectively. However, there was no significance between the yellow and orange tinted lens (p>0.64) Conclusions: Yellowish tinted lens that reduces chromatic aberration and the scattering is prescribed for the various purposes to improve visual functions. Before prescribing tinted lens, identifying characteristic of user and tinted lens for cut off wavelengths is recommended.

Current Control for an AFE Rectifier Using Space Vector PWM (공간벡터변조방식에 의한 AFE정류기의 전류제어)

  • Jeon, Cheol-Hwan;Hur, Jae-Jung;Yoon, Kyoung-Kuk;Yoo, Heui-Han;Kim, Sung-Hwan
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.4
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    • pp.498-503
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    • 2019
  • Electric propulsion ships are gaining widespread interest in the marine industry owing to extreme air pollution concerns. Consequently, several studies are actively being conducted for improving the power quality. Various methods have been developed that incorporate passive filters, notch filters, and active filters for reducing the harmonic content in the input current of a conventional diode front end rectifier. Among such filters, the active front end (AFE) rectifier is considered as an excellent technology. In this paper, current control for an AFE rectifier employing space vector PWM (Pulse Width Modulation) is proposed. Conventional current control methods for the AFE rectifier, hysteresis, SPWM (Sinusoidal Pulse Width Modulation), and SVPWM (Space Vector Pulse Width Modulation) were simulated by employing the PSIM software tool for analysis and comparisons. The results corroborate that SVPWM has the simplest structure and provides the best performance.

Image Magnification Using Median Filter and Spatial Variation (메디안 필터와 공간 변화량을 이용한 영상 확대)

  • Kwak, Nae-Joung
    • The Journal of the Korea Contents Association
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    • v.7 no.9
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    • pp.72-80
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    • 2007
  • Image magnification is the estimation of a few pixel in images with high quality from a pixel of an image with low resolution and there have been studied many techniques to make images with high quality. In this paper, we propose an image interpolation method using median filter and spatial information. The proposed method makes an interpolating pixel using an average value of a median filtered value and an average value of two pixels correlated with an interpolating pixel tightly. Also we make the magnified image with improved quality to add the directional information of surrounding pixels and the characteristic of ones using average value and max value of spatial variation. We evaluate the performance using PSNR in the quality of enlarged image comparing the proposed method with existing methods. The results show the proposed method improves PSNR than the existing methods and make images preserving the characteristic of original imges.

Comparative Analysis and Accuracy Improvement on Ground Point Filtering of Airborne LIDAR Data for Forest Terrain Modeling (산림지형 모델링을 위한 항공 라이다 데이터의 지면점 필터링 비교분석과 정확도 개선)

  • Hwang, Se-Ran;Lee, Im-Pyeong
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.29 no.6
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    • pp.641-650
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    • 2011
  • Airborne LIDAR system, utilized in various forest studies, provides efficiently spatial information about vertical structures of forest areas. The tree height is one of the most essential measurements to derive forest information such as biomass, which can be estimated from the forest terrain model. As the terrain model is generated by the interpolation of ground points extracted from LIDAR data, filtering methods with high reliability to classify reliably the ground points are required. In this paper, we applied three representative filtering methods to forest LIDAR data with diverse characteristics, measured the errors and performance of these methods, and analyzed the causes of the errors. Based on their complementary characteristics derived from the analysis results, we have attempted to combine the results and checked the performance improvement. In most test areas, the convergence method showed the satisfactory results, where the filtering performance were improved more than 10% in maximum. Also, we have generated DTM using the classified ground points and compared with the verification data. The DTM retains about 17cm RMSE, which can be sufficiently utilized for the derivation of forest information.