• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.683-686
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• 1998

This paper introduces a sigma-delta DAC with a fully-differential current-mode semidigital IFIR postfilter. A proposed fully-differential postfilter exhibits not only an improved SNR(signal-to-noise ratio) but also a reduced opwer dissipation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.122-125
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• 2011

In real environment, background noise exists everywhere and degrades the performance of system. To reduce this distortion, a speech enhancement algorithm can be very useful and variety methods have been proposed. In this paper, we propose a postfilter to improve the performance of optimally modified log-spectral amplitude (OM-LSA) estimator. Proposed algorithm uses the formant postfilter to minimize perceptual distortion caused by background noise. We adjust an emphasizing parameter which is varied by spectral flatness and first reflection coefficient. The performance of the proposed algorithm is evaluated by measuring the log-spectral distance (LSD) and the perceptual evaluation of speech quality (PESQ) score. The test results show the improvement of proposed algorithm compared to conventional OM-LSA.

• Speech Sciences
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• v.11 no.2
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• pp.259-269
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• 2004

In this paper, we propose a new excitation enhancement technique to improve the speech quality of low bit-rate code-excited linear prediction (CELP) coders. The proposed technique is based on a harmonic model and it is employed only in the decoding process of speech coders without any additional bits. We develop the procedure of harmonic model parameter estimation and harmonic generation, and apply this technique to a current state-of-the-art low bit rate speech coder, ITU-T G.729 Annex D. Also, its performance is measured by using the ITU-T P.862 PESQ score and compared to those of the phase dispersion filter and the long-term postfilter applied to the decoded excitation. It is shown that the proposed excitation enhancement technique can improve the quality of decoded speech and provide better quality for male speech than other techniques.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.351.2-351
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• 2002

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.57-60
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• 2003

In this paper, we propose a new excitation enhancement technique to improve the speech quality of low bit rate speech coders. The proposed technique is based on a harmonic model and it is employed only in the decoding process of speech coders without any additional bits. We develop the procedure of harmonic model parameters estimation and harmonic generation. and apply the technique to a current state of the art low bit rate speech coder, ITU-T G.729 Annex D. Also its performance is measured by using the ITU-T P.862 PESQ score and compared to those of the phase dispersion filter and the long-term postfilter applied to the decoded excitation. It is shown that the proposed excitation enhancement technique can improve the quality of decoded speech and provide better quality for male speech than other techniques.

• Speech Sciences
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• v.7 no.3
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• pp.185-195
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• 2000

This paper seeks to compare the feature parameters used in speaker identification systems under noisy environments. The feature parameters compared are LP cepstrum (LPCC), Cepstral mean subtraction(CMS), Pole-filtered CMS(PFCMS), Adaptive component weighted cepstrum(ACW) and Postfilter cepstrum(PF). The GMM-based text independent speaker identification system is designed for this target. Some series of experiments show that the LPCC parameter is adequate for modelling the speaker in the matched environments between train and test stages. But in the mismatched training and testing conditions, modified parameters are preferable the LPCC. Especially CMS and PFCMS parameters are more effective for the microphone mismatching conditions while the ACW and PF parameters are good for more noisy mismatches.

• Childhood Kidney Diseases
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• v.9 no.1
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• pp.76-82
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• 2005

Purpose : Regional anticoagulation with trisodium citrate for continuous renal replacement therapy(CRRT) is an effective and safe method, with lower bleeding risk. However it is not widely used because of complex current protocols used to prevent anticipated metabolic derangements. We evaluated simplified regional anticoagulation protocols with ACD-A(R) solution and commercially available calcium-containing dialysis solution. Methods : The medical records of twenty-eight patients who underwent CRRT were reviewed. Hemofilter life span according to the anticoagulation method used was compared, and laboratory findings at Pre- and 48 hours post-CRRT initiation were compared in the citrate-based CRRT group. Results : Of the twenty-eight Patients, five patients underwent citrate-based CRRT Hemofilter life span was 1.60 $\pm$ 0.72 days, showing no significant differences with the hemofilter life span in the heparin based and LMWH based CRRT group. No patients experienced hemorrhagic complications. PT, aPTT, sodium, t$CO_{2}$, iCa levels showed no difference in pre- and post-CRRT. Total calcium levels were increased. At the recommended postfilter iCa level, j.e., 0.25-0.39 mmol/L, all five patients needed increased amount of citrate infusion, and Ca infusion requirement was decreased. Conclusion : Simplified regional citrate anticoagulation with calcium-containing dialysate is an effective and safe method, and is not associated with increased hemofilter clotting. However, increased postfilter iCa level is recommended.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.10
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• pp.964-971
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• 1991

In DPCM coder which has flat notse distributions, reconstruction noises might be shaped or transferred to hign frequency portion using the relevant noise reduction loop under the constraints of image compression. Noise shaping filter directly in loop can be used, but we shows the complete characteristics of signal blurred DPCM coder in view of data compression and noise processing. Equi weighting in bluming procedure of prefilter is introduced and the blurred signal is restored by debiurning postfilter. Noise shaping tegion on two dimensional frequency domain depends upon the size of masking filter. In spite of its noise increments by the signal blurring, the algonthm is effective for the visually relevant coding which has low pass freqency properties.