Đang chuẩn bị liên kết để tải về tài liệu:
Advanced Methods and Tools for ECG Data Analysis - Part 6

Sự liên kết giữa trisomy 21 và bệnh tim bẩm sinh được công nhận. Trẻ em mắc hội chứng Down và khuyết tật vách liên nhĩ thất (AVSD) phải trải qua sửa chữa sớm trước khi sự phát triển của phổi cao huyết áp. | 6.4 Empirical Nonlinear Filtering 185 Figure 6.4 Illustration of NNR a original noisy ECG signal y t b underlying noise-free ECG x t c noise-reduced ECG signal z t and d remaining error z t -x t . The signal-to-noise ratio was Y 10 and the NNR used parameters m 20 d 1 and r 0.08. factor X and the correlation p as a function of the reconstruction dimension m for signals having Y 10 5 2.5. For Y 10 maxima occur at X 2.2171 and p 0.9990 both with m 20. For the intermediate signal to noise ratio Y 5 maxima occur at X 2.6605 and p 0.9972 with m 20. In the case of Y 2.5 the noise reduction factor has a maximum X 3.3996 at m 100 whereas the correlation p 0.9939 has a maximum at m 68. ICA gave best results for all signal to noise ratios for a delay of d 1. As may be seen from Figure 6.5 optimizing the noise reduction factor X or the correlation p gave maxima at different values of m. For Y 10 the maxima were X 26.7265 at m 7 and p 0.9980 at m 9. For the intermediate signal to noise ratio Y 5 the maxima are X 18.9325 at m 7 and p 0.9942 at m 9. Finally for Y 2.5 the maxima are X 10.8842 at m 8 and p 0.9845 at m 11. A demonstration of the effect of optimizing the ICA algorithm over either X or p is illustrated in Figure 6.6. While both the X-optimized cleaned signal Figure 6.6 b and the p-optimized cleaned signal Figure 6.6 d are similar to the original noise-free signal Figure 6.6 a an inspection of their respective errors Figure 6.6 c and Figure 6.6 e emphasizes their differences. The X-optimized outperforms the p-optimized in recovering the R peaks. A summary of the results obtained using both the NNR and ICA techniques are presented in Table 6.1. These results demonstrate that NNR performs better in terms of providing a cleaned signal which is maximally correlated with the original 186 Nonlinear Filtering Techniques Figure 6.5 Variation in a noise reduction factor X and b correlation p for ICA with reconstruction dimension m and delay d 1. The signal-to-noise ratios are