摘要:

This paper presents the applications of the spectrogram, Wigner distribution and wavelet transform analysis methods to the phonocardiogram (PCG) signals. A comparison between these three methods has shown the resolution differences between them. It is found that the spectrogram short-time Fourier transform (STFT), cannot detect the four components of the first sound of the PCG signal. Also, the two components of the second sound are inaccurately detected. The Wigner distribution can provide time-frequency characteristics of the PCG signal, but with insufficient diagnostic information: the four components of the first sound, SI, are not accurately detected and the two components of the second sound, S2, seem to be one component. It is found that the wavelet transform is capable of detecting the two components, the aortic valve component A2 and pulmonary value component P2, of the second sound S2 of a normal PCG signal. These components are not detectable using the spectrogram or the Wigner distribution. However, the standard Fourier transform can display these two components in frequency but not the time delay between them. Furthermore, the wavelet transform provides more features and characteristics of the PCG signals that mill help physicians to obtain qualitative and quantitative measurements of the time-frequency characteristics.

ISSN:0309-1902    

DOI:10.3109/03091909309006329

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

It is shown that time frequency signal analysis could be a useful technique in detecting late potentials (LP). In particular, the spectrogram, the Wigner distribution and the wavelet transform have been applied to ECG signals from patients with sustained ventricular tachycardia. Comparisons of the three algorithms reveals that much better time localization is achieved by the wavelet transform. Moreover, it is concluded that a separation between healthy subjects and patients could be obtained based upon time frequency analysis.

ISSN:0309-1902    

DOI:10.3109/03091909309006330

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Lever-propelled wheelchairs have been described as more efficient and less physically demanding than hand-rim-propelled wheelchairs. To evaluate a newly designed lever mechanism (MARC) in both one-and two-arm use, a series of wheelchair exercise tests were performed on a motor-driven treadmill. Eight able-bodied male subjects performed a standard exercise test in the prototype MARC, both in an asynchronic and a synchronic bimanual propelling mode and in an unilateral (left-sided) mode. Subsequently the subjects performed additional exercise tests in a conventional crank-to-rod lever mechanism with unilateral and bimanual propulsion and in a conventional hand rim wheelchair. Analysis of variance was used to study the effect of tile different work modes upon power output and cardio-respiratory parameters statistically (p<0.05). The MARC stood out well in comparison with the conventional lever design. The additional design features which are to be implemented (variable gearing, reverse gear) will make the MARC a useful wheelchair. One-arm wheelchair propulsion is a very strenuous form of locomotion, requiring careful consideration in terms of provision. Mechanical and ergonomic improvements are quite feasible in lever propulsion and may to a certain extent reduce this problem. To improve overall mobility of wheelchair-dependenl subjects further, ergonomic and mechanical design improvements are very necessary in lever as well as hand-rim wheelchairs. A combined biomechanical and physiological research approach will help in the definition of design criteria and fitting guidelines.

ISSN:0309-1902    

DOI:10.3109/03091909309006331

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0309-1902    

DOI:10.3109/03091909309006332

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0309-1902    

DOI:10.3109/03091909309006333

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor