• Title/Summary/Keyword: hybrid detector

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Low Complexity Hybrid Interpolation Algorithm using Weighted Edge Detector (가중치 윤곽선 검출기를 이용한 저 복잡도 하이브리드 보간 알고리듬)

  • Kwon, Hyeok-Jin;Jeon, Gwang-Gil;Jeong, Je-Chang
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.3C
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    • pp.241-248
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    • 2007
  • In predictive image coding, a LS (Least Squares)-based adaptive predictor is an efficient method to improve image edge predictions. This paper proposes a hybrid interpolation with weighted edge detector. A hybrid approach of switching between bilinear interpolation and EDI (Edge-Directed Interpolation) is proposed in order to reduce the overall computational complexity The objective and subjective quality is also similar to the bilinear interpolation and EDI. Experimental results demonstrate that this hybrid interpolation method that utilizes a weighted edge detector can achieve reduction in complexity with minimal degradation in the interpolation results.

Zinc Sulfide-selenium X-ray Detector for Digital Radiography

  • Park, Ji-Koon;Kang, Sang-Sik;Kim, Jae-Hyung;Mun, Chi-Woong;Nam, Sang-Hee
    • Transactions on Electrical and Electronic Materials
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    • v.3 no.4
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    • pp.16-20
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    • 2002
  • The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/㎠/mR and 295 pC/㎠/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.

The dark-current and X -ray sensitivity measurement of hybrid digital X-ray detector having dielectric layer structure (a-Se 기반의 혼합형 X-선 검출기에서 유전층의 누설전류 저감효과)

  • Seok, Dae-Woo;Park, Ji-Koon;Joh, Jin-Wook;Lee, Dong-Gil;Moon, Chi-Woong;Nam, Sang-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05b
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    • pp.31-34
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    • 2002
  • In this paper, the electric properties of amophous selenium multilayer samples has been investigated. In order to develop the hybrid flat-panel digital· X-ray image detector, we measured and analyzed their performance parameters such as the X -ray sensitivity and dark-current for a amophous selenium multilayers X-ray detector with a phosphor layer, The hybrid digital X-ray image detector can be constructed by integrating a phosphor layer (or a scintillative layer) that convert X-ray to a light on a-Se photoconduction mulilayers that convert a light to electrical signal. As results, the dielectric materials such as parylene between the phosphor layer and the top electrode may reduce the dark-current of the samples. Amorphous selenium multilayers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. In this paper offer the method can reduce the dark-current in the hybrid X-ray detector.

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The characteristic study of hybrid X-ray detector using ZnS:Ag phosphor (ZnS:Ag phosphor를 이용한 hybrid 형 X-ray detector 특성 연구)

  • Park, Ji-Koon;Gang, Sang-Sik;Lee, Dong-Gil;Cha, Byeong-Yeol;Nam, Sang-Hee;Choi, Heung-Kook
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05b
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    • pp.27-30
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    • 2002
  • Photoconductor for direct detection flat-panel imager present a great materials challenge, since their requirements include high X -ray absorption, ionization and charge collection, low leakage current and large area deposition. Selenium is practical material. But it needs high thickness and high voltage in selenium for high ionization rate. We report comparative studies of detector sensitivity. One is an a-Se with $70{\mu}m$ thickness on glass. The other has hybrid layer of depositting ZnS phosphor with $100{\mu}m$ on a-Se. The leakage current of hybrid is similar to it of a-Se, but photocurrent is lager than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

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Multi-layer design of Hybrid method for digital X-ray imaging (디지털 X-ray imaging을 위한 Hybrid 방식의 다층구조 설계)

  • Cho, Sung-Ho;Park, Ji-Koon;Lee, Dong-Gil;Kim, Dae-Hwan;Kim, Jae-Hyung;Nam, Sang-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05c
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    • pp.75-78
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    • 2003
  • In recent years, there has been keen interest in developing flat panel detectors for all modalities of radiology, including gerneral radiology, fluoroscopy, electronic portal imaging, and mammography. In this paper, we report the new hybrid x-ray detector consisted of ZnS(Ag) photoemission layer and a-Se photoconductor layer to resolve problem of conventional x-ray detector such as the direct detector and the indirect detector. To design the structure of ZnS(Ag)/a-Se detector, the penetrated energy spectrum and absorption fraction was estimated using MCNP 4C code. Also, we carried out the experiment to demonstrate the result of MCNP 4C code. Experimental results showed that the absorption fraction of $500{\mu}m$-ZnS(Ag) film was above 87%, 75% at 60 and 80 kVp. As a results, we can determined the thickness of suitable phosphor and the thickness of photoconductor.

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A New Confidence Measure for Eye Detection Using Pixel Selection (눈 검출에서의 픽셀 선택을 이용한 신뢰 척도)

  • Lee, Yonggeol;Choi, Sang-Il
    • KIPS Transactions on Software and Data Engineering
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    • v.4 no.7
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    • pp.291-296
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    • 2015
  • In this paper, we propose a new confidence measure using pixel selection for eye detection and design a hybrid eye detector. For this, we produce sub-images by applying a pixel selection method to the eye patches and construct the BDA(Biased Discriminant Analysis) feature space for measuring the confidence of the eye detection results. For a hybrid eye detector, we select HFED(Haar-like Feature based Eye Detector) and MFED(MCT Feature based Eye Detector), which are complementary to each other, as basic detectors. For a given image, each basic detector conducts eye detection and the confidence of each result is estimated in the BDA feature space by calculating the distances between the produced eye patches and the mean of positive samples in the training set. Then, the result with higher confidence is adopted as the final eye detection result and is used to the face alignment process for face recognition. The experimental results for various face databases show that the proposed method performs more accurate eye detection and consequently results in better face recognition performance compared with other methods.

X-ray Sensitivity of Hybrid-type Sensor based on CaWO4-Selenium for Digital X-ray Imager

  • Park, Ji-Koon;Park, Jang-Yong;Kang, Sang-Sik;Lee, Dong-Gil;Kim, Jae-Hyung;Nam, Sang-Hee
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.4
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    • pp.133-137
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    • 2004
  • The development of digital x-ray detector has been extensively progressed for the application of various medical modalities. In this study, we introduce a new hybrid-type x-ray detector to improve problems of a conventional direct or indirect digital x-ray image technology, which composed of multi-layer structure using a CaWO$_4$ phosphor and amorphous selenium (a-Se) photoconductor. The leakage current of our detector was found to be ∼180 pA/cm$^2$ at 10 V/m, which was significantly reduced than that of a single a-Se detector. The x-ray sensitivity was measured as the value of 4230 pC/cm$^2$/mR at 10 V/m. We found that the parylene thin film between a CaWO$_4$ phosphor and an a-Se layer acts as an insulator to prevent charge injection from indium thin oxide (ITO) electrode into an a-Se layer under applied bias.

A Study on Diagnosing Fouling of Heat Exchangers of a Hybrid Heat Pump (하이브리드 열펌프 열교환기 오염 진단 연구)

  • Shin, Younggy
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.5
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    • pp.240-246
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    • 2014
  • A fault detector was developed for heat exchangers of a hybrid heat pump (HP) for household. The proposed detector can be applied directly to raw operating data. It is to monitor a tracking error between a measured saturation temperature and its state observer. The observer was estimated from a state-space model simulating dynamics of a heat exchanger. The real hybrid HP was substituted with a dynamic simulator that implemented two-phased heat transfer and was validated by experimental data. And artificial fault data were generated using the simulator. Diagnosing the data showed the following. The residual calculated from the state observer error shows a relatively robust consistency with respect fouling level. The fault detector is practically useful because it detects a threshold fouling beyond which the performance starts to deteriorate significantly.

X-ray Response Characteristic of Hybrid-type CdZnTe Detector (혼합형 CdZnTe 검출기의 X선 반응특성)

  • Cha, B.Y.;Kang, S.S.;Kong, H.G.;Lee, G.H.;Kim, J.H.;Nam, S.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05b
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    • pp.35-38
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    • 2002
  • In this paper, for digital x-ray conversion receptor development studied by hybrid technology of based on CdZnTe. For this study, First searched fabricate method of CdZnTe x-ray receptor. Second, search the phosphor material & fabricate method for scintillator layer. Fabricated sample is analyzed with physical & electric measurement. This result is showed good SNR ratio hybrid thechnology with direct method & indirect method. In this paper offer the method can reduce the dark-current in the hybrid X-ray detector.

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The Study on Composition ratio of Iodine in Hybrid X-ray Sensor (혼합형 X선 센서에서 a-Se 의 Iodine 첨가비 연구)

  • Gong, Hyung-Gi;Park, Ji-Koon;Choi, Jang-Yong;Moon, Chi-Wung;Nam, Sang-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.11a
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    • pp.366-369
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    • 2002
  • At present, the study of direct digital X-ray detector and indirect digital X-ray detector proceed actively. But it needs high thickness and high voltage in selenium for high ionization rate. Therefore, we carried out the study of electric characteristics of a-Se with additive ratio of Iodine in drafting study for developing Hybrid X -ray Sensor for complementing direct digital X -ray detector and indirect digital X-ray detector in this paper. On this, there are formed Amorphous selenium multi-layers by sticking phosphor layer$(Gd_{2}O_{2}S(Eu^{2+}))$ using optical adhesives of EFIRON Co. Amorphous selenium multi-layers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. We make Amorphous selenium multi-layers with $30{\mu}m$ thickness on glass.

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