Applied Mechanics and Materials Vols. 239-240

Abstract: The diagnosis of sleep apnea syndrome (SAS) has important clinical significance for the prevention of hypertension, coronary heart disease, arrhythmias, stroke and other diseases. In this paper, a novel method for the detection of SAS based on single-lead Electrocardiogram (ECG) signal was proposed. Firstly, the R-peak points of ECG recordings were pre-detected to calculate RR interval series and ECG-derived respiratory signal (EDR). Then 40 time- and spectral-domain features were extracted and normalized. Finally, support vector machine (SVM) was employed to these features as a classifier to detect SAS events. The performance of the presented method was evaluated using the MIT-BIH Apnea-ECG database, results show that an accuracy of 95% in train sets and an accuracy of 88% in test sets are achievable.

Abstract: Accurate channel estimation plays a key role in multiple-input and multiple-output (MIMO) communication systems. In this paper, we firstly discuss the popular linear least squares (LS) channel estimation and the multiple LS (MLS) channel estimation. Then an adaptive multiple LS (AMLS) channel estimate approach is proposed. Using numerical simulation, it is found that the proposed estimation method outperforms LS and MLS for a wide range of training SNRs.

Abstract: The method to process measured data of ship model test with contact measurement to study the characteristics of relative motion between two side-by-side ships was investigated. The reference co-ordinate systems and the relative motions of two side-by-side replenishment ships were defined. Then the integration transform method which combines Fast Fourier Transform(FFT) with Empirical Mode Decomposition(EMD) self-adaptive filter was applied to transform measured acceleration signal into displacement. The EMD adaptive filter is designed, and the integration results from acceleration to displacement with and without EMD adaptive filter were compared, which shows that the EMD adaptive filter can effectively eliminate the noise embedded in the measured data. At last, the relative motions are acquired, which are consistent with the practical situation.

Abstract: The influence of parameters to the firing patterns of time-delayed linear and compound Hindmarsh-Rose(HR) model neuron are studied in this work. For an individual neuron, it can be found from different Intervalspike Interval (ISI) maps that the firing patterns transform among resting state, busting firing, tonic firing, and chaotic spiking, especially, the transfer of the firing patters are speeded up under feedback mechanism, it is easier to get into the chaotic firing state compared with linear feedback.

Abstract: Triphone DDBHMM (Duration Distribution Based HMM) is presented as the acoustic model for Mongolian continuous speech recognition, and the Mongolian Acoustic Model is optimized by state-binding. The experiment made a comparison of the triphone DDBHMM, diphone DDBHMM, triphone HMM on HTK platform and analyzed their effects on the accuracy of acoustic layer. The experimental results have showed that Triphone DDBHMM significantly improves the recognition performance of continuous speech recognition in Mongolian.

Abstract: The number of pixels of object and background generally has a large difference. Thresholds calculated by the optimal evolution algorithm (OEA) tend to the class which has more samples than the other, then the optimal evolution algorithm falls into a local optimal solution. A threshold modification model was built up for an improved optimal evolution algorithm. The improved OEA can adaptively modify the threshold in each evolutional generation according to the difference of pixels’ number between object and background. Experimental results show that the improved OEA is more stable, converge more rapidly, and has better segmentation quality than OEA.

Abstract: FID signal is the envelope of magnetic resonance signal, and the extraction accuracy of characteristic parameters directly influence the accuracy of the hydrogeologic parameters of the inverse interpretation. In order to improve the accuracy of characteristic parameters extraction, made simulation and study combined the autocorrelation function fitting with the least absolute value nonlinear fitting method in different SNR and different noise in this paper. The simulation results showed that, the characteristic parameters fitting error using this method was smaller than that using linear, nonlinear fitting method or the autocorrelation function with the least squares method, within 7% in lower SNR. The field measurement data and inversion results verified the method validity.

Abstract: A blind image restoration method is proposed to improve the quality of the image blurred by camera defocus and system noise. Firstly, the focus point spread function (PSF) of the blurred image is estimated through error-parameter analysis method. Secondly, the Signal-to-Noise Ratio (SNR) of the blurred image is estimated through local deviation method. Thirdly, utilizing the estimated defocus PSF and SNR, image restoration is performed through Wiener filtering method, in which circulation boundary method is adopted to reduce ringing effect. Experimental results show that the SNR of the blurred image is estimated approximately, and verify the great effect of SNR estimation in blind image restoration.

Abstract: Digital audio coding delays have become increasingly critical in real-time wireless applications. In live productions, a codec with ultra low delay is required within the constraints of the available channel bandwidth. However, such a threshold can hardly be reached by means of standard audio coding schemes. To achieve low delay as well as to satisfy cost and power consumption constraints, this paper presents an ultra low delay audio coder by very short block processing and embedded coding implemented in fixed-point DSP. The short block two dimensional (2D) spatial-frequency processing of audio input signal fully exploits the correlation for better compression performance. Lifting wavelet transform with boundary effects minimized by changing wavelet shape is developed using bit shifts and additions to replace multiplications in a fixed-point specification under accuracy constraint. The embedded coding offers the error resilience feature so that joint source-channel coding scheme for unequal error protection can be easily designed by varying both source coding bit rate and channel coding redundancy. Experimental results demonstrate that the proposed coder is efficient and requires less memory in fixed-point computation which guarantees no overflow.

Abstract: On the base of fundamental principle of multiple-average harmonic Algorithm, a novel Harmonic calculating method is proposed, by which the amplitude and phase of every harmonics can be calculated accurately and conveniently. Computer simulation and physical experiment prove that the Algorithm has very high accuracy. Further, the influence of noise at samples to the result has been discussed by Monte Carlo method and given a qualitative result for practical engineering application.