• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.9-17
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• 2012

Recently, a new image appearance model, named iCAM06, was developed for High-Dynamic-Range (HDR) image rendering. The dynamic range of a HDR image needs to be mapped on the range of output devices, which is called the tone reproduction or tone mapping. The iCAM06, the representative HDR rendering algorithm also uses the tone compression using a S-curve mapping function for image reproduction on the dynamic range of output devices. However the iCAM06 occurs white point shift during its tone compression process. Therefore, we propose a compensation method for white point shift problem using the corrected channel gain function. Experiment results show that the proposed method has better performance than the iCAM06.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7A
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• pp.1005-1015
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• 1999

This paper is concerned with an improvement on IFFT (inverse fast Fourier transform) and FFT based baseband digital implementation algorithm for BPSK (binary phase shift keying)-modulated MC-CDMA (multicarrier-code division multiple access) systems, that is functionally equivalent to the conventional implementation algorithm, while reducing computational complexity and bandwidth requirement. We also derive an equalizer structure for the proposed implementation algorithm. The proposed algorithm is based on a variant of FFT algorithm that utilizes a N/2-point FFT/IFFT for simultaneous transformation and reconstruction of two N/2-point real signals. The computer simulations under additive white Gaussian noise channels and frequency selective fading channels using equal gain combiner and maximal ratio combiner diversities, demonstrate the performance of the proposed algorithm.

• Journal of radiological science and technology
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• v.26 no.2
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• pp.57-61
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• 2003

The purpose of this study is to compare both 1.5T and 4.7T in Praietal White matter material Phantom using the same methodology at both field strengths. Data at both field strengths are compared in terms of $T_2$ relaxation times, line widths and SNRs MR imaging and $^1H$ MR spectroscopy were performed on GE 1.5T SIGNA system and Broker Biospec 4.7T/30 MRI/MRS system. After phantom axial scan $^1H$ MRS was obtained from T2 weighted image by 3-dimensional localization technique(PRESS : Point RE solved spectroscopy Sequence) this phantom is composed of an aqueous solution 36.7 mmol/L of NAA, 25.0 mmol/L of Cr, 6.3 mmol/L of choline chloride, 30.0 mmol/L or Glu, and 22.5 mmol/L of MI(adjusted to a pH of 7,15 in a phosphate buffet). Data processed using software developed inhouse. At 1.5T, T2 relaxation times for Cho, Cr, and NAA were $0.41{\pm}0.07,\;0.26{\pm}0.04,\;0.46{\pm}0.07$ while at 4.7T they were $0.17{\pm}0.03,\;0.14{\pm}0.05,\;0.20{\pm}0.03$ respectively. At 1.5T, line widths for water, Cho, Cr and NAA were $2.9{\pm}0.7,\;1.6{\pm}0.7,\;1.7{\pm}0.8,\;2.2{\pm}0.02Hz$ while at 4.7T they were $5.2{\pm}1.1,\;4.6{\pm}1.9,\;4.01{\pm}1.8,\;4.8{\pm}1.9Hz$ respectively. It can be seen that $T_2$ relaxation times were significantly shorter at 4.7 compared to 1.5T and that the line widths were also broader. The average SNRs for NAA for subjects at short and long TEs were $23.5{\pm}11.3$ at TE=20 msec ; $15.4{\pm}7.7$ at TE=272 msec at 1.5T and $40{\pm}8.3$ and $17{\pm}3.5$ respectively at 4.7T higher field strength is superior because of improved sensitivity and chemical shift dispersion. However these improvements are partially offset by increased line widths and decrease $T_2$ relaxation times, which act to reduce both sensitivity and resolution. In our experiments with the equipment available to us, 4.7T proton spectra at short TEs exhibit moderately improved sensitivity compared to 1.5T.