The Experts below are selected from a list of 217230 Experts worldwide ranked by ideXlab platform
M. Ibrahim Sezan - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution image reconstruction from Lower-Resolution image sequences and space-varying image restoration
[Proceedings] ICASSP-92: 1992 IEEE International Conference on Acoustics Speech and Signal Processing, 1992Co-Authors: A. Murat Tekalp, M.k. Ozkan, M. Ibrahim SezanAbstract:The authors address the problem of reconstruction of a high-Resolution image from a number of Lower-Resolution (possibly noisy) frames of the same scene where the successive frames are uniformly based versions of each other at subpixel displacements. In particular, two previously proposed methods, a frequency-domain method and a method based on projections onto convex sets (POCSs), are extended to take into account the presence of both sensor blurring and observation noise. A new two-step procedure is proposed, and it is shown that the POCS formulation presented for the high-Resolution image reconstruction problem can also be used as a new method for the restoration of spatially invariant blurred images. Some simulation results are provided.
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ICASSP - High-Resolution image reconstruction from Lower-Resolution image sequences and space-varying image restoration
[Proceedings] ICASSP-92: 1992 IEEE International Conference on Acoustics Speech and Signal Processing, 1992Co-Authors: A. Murat Tekalp, M.k. Ozkan, M. Ibrahim SezanAbstract:The authors address the problem of reconstruction of a high-Resolution image from a number of Lower-Resolution (possibly noisy) frames of the same scene where the successive frames are uniformly based versions of each other at subpixel displacements. In particular, two previously proposed methods, a frequency-domain method and a method based on projections onto convex sets (POCSs), are extended to take into account the presence of both sensor blurring and observation noise. A new two-step procedure is proposed, and it is shown that the POCS formulation presented for the high-Resolution image reconstruction problem can also be used as a new method for the restoration of spatially invariant blurred images. Some simulation results are provided. >
K. A. Walker - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics, 2007Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 4%. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O 3 , HCl, N 2 O, and CH 4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics, 2007Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maxi- mum optical path difference of 250 cm, and the two Lower- Resolution instruments have maximum optical path differ- ences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution in- strument generally better than 4%. Total column amounts of the stratospheric species (O3 and HCl) have larger differ- ences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of strato- spheric gases from the Lower-Resolution instruments. Includ- ing the ILS information in the retrievals significantly reduces the difference in total column amounts between the three in- struments. The remaining errors for stratospheric species to- tal column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O<sub>3</sub>, HCl, N<sub>2</sub>O, and CH<sub>4</sub> over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics Discussions, 2006Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:Abstract. An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 3%, with respect to the high-Resolution FTS. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics Discussions, 2006Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 3%, with respect to the high-Resolution FTS. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
A. Murat Tekalp - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution image reconstruction from Lower-Resolution image sequences and space-varying image restoration
[Proceedings] ICASSP-92: 1992 IEEE International Conference on Acoustics Speech and Signal Processing, 1992Co-Authors: A. Murat Tekalp, M.k. Ozkan, M. Ibrahim SezanAbstract:The authors address the problem of reconstruction of a high-Resolution image from a number of Lower-Resolution (possibly noisy) frames of the same scene where the successive frames are uniformly based versions of each other at subpixel displacements. In particular, two previously proposed methods, a frequency-domain method and a method based on projections onto convex sets (POCSs), are extended to take into account the presence of both sensor blurring and observation noise. A new two-step procedure is proposed, and it is shown that the POCS formulation presented for the high-Resolution image reconstruction problem can also be used as a new method for the restoration of spatially invariant blurred images. Some simulation results are provided.
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ICASSP - High-Resolution image reconstruction from Lower-Resolution image sequences and space-varying image restoration
[Proceedings] ICASSP-92: 1992 IEEE International Conference on Acoustics Speech and Signal Processing, 1992Co-Authors: A. Murat Tekalp, M.k. Ozkan, M. Ibrahim SezanAbstract:The authors address the problem of reconstruction of a high-Resolution image from a number of Lower-Resolution (possibly noisy) frames of the same scene where the successive frames are uniformly based versions of each other at subpixel displacements. In particular, two previously proposed methods, a frequency-domain method and a method based on projections onto convex sets (POCSs), are extended to take into account the presence of both sensor blurring and observation noise. A new two-step procedure is proposed, and it is shown that the POCS formulation presented for the high-Resolution image reconstruction problem can also be used as a new method for the restoration of spatially invariant blurred images. Some simulation results are provided. >
D. Wunch - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics, 2007Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 4%. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O 3 , HCl, N 2 O, and CH 4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics, 2007Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maxi- mum optical path difference of 250 cm, and the two Lower- Resolution instruments have maximum optical path differ- ences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution in- strument generally better than 4%. Total column amounts of the stratospheric species (O3 and HCl) have larger differ- ences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of strato- spheric gases from the Lower-Resolution instruments. Includ- ing the ILS information in the retrievals significantly reduces the difference in total column amounts between the three in- struments. The remaining errors for stratospheric species to- tal column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O<sub>3</sub>, HCl, N<sub>2</sub>O, and CH<sub>4</sub> over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics Discussions, 2006Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:Abstract. An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 3%, with respect to the high-Resolution FTS. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
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Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different Resolutions
Atmospheric Chemistry and Physics Discussions, 2006Co-Authors: D. Wunch, J. R. Taylor, P. Bernath, J. R. Drummond, C. Midwinter, K. Strong, K. A. WalkerAbstract:An intercomparison of three Fourier transform spectrometers (FTSs) with significantly different Resolutions is presented. The highest-Resolution instrument has a maximum optical path difference of 250 cm, and the two Lower-Resolution instruments have maximum optical path differences of 50 cm and 25 cm. The results indicate that the two Lower-Resolution instruments can retrieve total column amounts of O3, HCl, N2O and CH4 using the SFIT2 retrieval code with percent differences from the high-Resolution instrument generally better than 3%, with respect to the high-Resolution FTS. Total column amounts of the stratospheric species (O3 and HCl) have larger differences than those of the tropospheric species (N2O and CH4). Instrument line shape (ILS) information is found to be of critical importance when retrieving total columns of stratospheric gases from the Lower-Resolution instruments. Including the ILS information in the retrievals significantly reduces the difference in total column amounts between the three instruments. The remaining errors for stratospheric species total column amounts can be attributed to the Lower sensitivity of the Lower-Resolution FTSs to the stratosphere.
Xiangjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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can Lower Resolution be better
Data Compression Conference, 2008Co-Authors: Xiangjun ZhangAbstract:Recently, many researchers started to question a long-standing paradox in the engineering practice of digital photography: oversampling followed by compression, and pursue more intelligent sparse sampling techniques. In this research we take a practical approach of uniform down sampling in image space, and the sampling is made adaptive by a spatially varying directional low-pass prefiltering. Since the down-sampled prefiltered image is a low-Resolution image of conventional square sample grid, it can be compressed and transmitted without any change to current image coding standards and systems. The decoder first decompresses the low-Resolution image and then upsamples it to the original Resolution by least-square estimation using a 2D piecewise autoregressive model and the knowledge of directional low-pass filter. The proposed joint adaptive down-sampling and up-sampling technique outperforms JPEG 2000 (the state-of-the-art in lossy image coding) in PSNR measure at low to modest bit rates and achieves superior visual quality at all bit rates. This work shows that oversampling not only increases cost and energy consumption, but it could, even when coupled with a sophisticated rate-distortion optimized compression scheme, cause inferior image quality at certain bit rates.
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DCC - Can Lower Resolution Be Better
Data Compression Conference (dcc 2008), 2008Co-Authors: Xiangjun ZhangAbstract:Recently, many researchers started to question a long-standing paradox in the engineering practice of digital photography: oversampling followed by compression, and pursue more intelligent sparse sampling techniques. In this research we take a practical approach of uniform down sampling in image space, and the sampling is made adaptive by a spatially varying directional low-pass prefiltering. Since the down-sampled prefiltered image is a low-Resolution image of conventional square sample grid, it can be compressed and transmitted without any change to current image coding standards and systems. The decoder first decompresses the low-Resolution image and then upsamples it to the original Resolution by least-square estimation using a 2D piecewise autoregressive model and the knowledge of directional low-pass filter. The proposed joint adaptive down-sampling and up-sampling technique outperforms JPEG 2000 (the state-of-the-art in lossy image coding) in PSNR measure at low to modest bit rates and achieves superior visual quality at all bit rates. This work shows that oversampling not only increases cost and energy consumption, but it could, even when coupled with a sophisticated rate-distortion optimized compression scheme, cause inferior image quality at certain bit rates.
